Acute Respiratory Distress Syndrome

Complex MONDO:0006502 Pathograph 49 Show in embeddings browser acute respiratory failure lung disorder

Acute respiratory distress syndrome is acute diffuse inflammatory lung injury following a pulmonary or systemic insult. Increased alveolar-capillary permeability, impaired fluid clearance and surfactant dysfunction produce noncardiogenic edema, loss of aerated lung and hypoxemic respiratory failure. The syndrome is heterogeneous and does not require invariant diffuse alveolar damage. Adult global and pediatric PALICC-2 definitions have distinct oxygenation, respiratory-support and imaging criteria.

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◆

Subtypes

age group

Adult Acute Respiratory Distress Syndrome MONDO:0100130

ARDS in adults, classified clinically by the severity of acute hypoxemia and recognized in intubated, nonintubated, and resource-limited settings under the 2024 global definition.

Show evidence (1 reference)

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We propose a new global definition of ARDS that builds on the Berlin definition."

The international consensus document defines the current clinical scope used for adult ARDS.

Pediatric Acute Respiratory Distress Syndrome MONDO:0100131

ARDS in patients younger than 18 years without active perinatal lung disease. PALICC-2 uses pediatric oxygenation criteria and permits unilateral or bilateral parenchymal opacities; nasal noninvasive support or HFNC can qualify as possible PARDS rather than confirmed NIV-PARDS.

Show evidence (1 reference)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"All patients less than 18 years old without active perinatal lung disease should be diagnosed with PARDS using PALICC-2 criteria."

PALICC-2 specifies pediatric scope and exclusions.

biological subphenotype

Hyperinflammatory ARDS subphenotype

A latent-class-analysis phenotype enriched for inflammatory biomarkers, vasopressor use, metabolic acidosis, fewer ventilator-free days, and higher mortality. This is a research subphenotype rather than part of the clinical ARDS definition or a validated bedside diagnosis.

Show evidence (2 references)

PMID:24853585 SUPPORT DIRECT PRIMARY RESULT Computational

"FINDINGS: We analysed data for 1022 patients: 473 in the ARMA cohort and 549 in the ALVEOLI cohort."

Latent-class modeling was applied to 473 lower-tidal-volume ARMA participants and 549 ALVEOLI participants; this is retrospective research stratification.

PMID:24853585 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"It is important to emphasize that while the interactions identified between PEEP and clinical outcomes are potentially provocative, we are reticent to make any recommendations for clinical care on the basis of a subgroup analysis."

The investigators explicitly treat subgroup treatment findings as hypothesis-generating.

Hypoinflammatory ARDS subphenotype

A research latent-class group with less systemic inflammation and shock than the hyperinflammatory group. Lower biomarker concentrations do not establish mitochondrial exhaustion, a uniform molecular mechanism, or a bedside treatment indication.

Show evidence (2 references)

PMID:24853585 SUPPORT DIRECT PRIMARY RESULT Computational

"FINDINGS: We analysed data for 1022 patients: 473 in the ARMA cohort and 549 in the ALVEOLI cohort."

Latent-class modeling was applied to 473 lower-tidal-volume ARMA participants and 549 ALVEOLI participants; this is retrospective research stratification.

PMID:24853585 SUPPORT DIRECT PRIMARY RESULT Human Clinical

The investigators explicitly treat subgroup treatment findings as hypothesis-generating.

◈

Mechanistic Hypotheses

Alveolar-Capillary Permeability Injury Model

alveolar_capillary_injury_model CANONICAL

Evidence balance 1 support

A direct pulmonary or indirect systemic insult initiates dysregulated innate inflammation and coagulation. Macrophage activation and recruited neutrophils injure the alveolar epithelium and pulmonary endothelium, increasing barrier permeability. Protein-rich edema, loss of aerated lung, and atelectasis then produce shunt physiology, reduced compliance, and hypoxemic respiratory failure.

Pathograph links

Direct Pulmonary or Indirect Systemic Insult -> Alveolar Macrophage Activation INDIRECT UNKNOWN INTERMEDIATES Innate sensing connects pulmonary or systemic injury to macrophage activation.

Direct Pulmonary or Indirect Systemic Insult -> Alveolar-Capillary Barrier Disruption INDIRECT UNKNOWN INTERMEDIATES Direct injury and systemic inflammatory pathways can increase barrier permeability.

Alveolar Macrophage Activation -> Pulmonary Cytokine and Chemokine Release INDIRECT UNKNOWN INTERMEDIATES Activated macrophages release inflammatory mediators.

Pulmonary Cytokine and Chemokine Release -> Neutrophil Recruitment INDIRECT UNKNOWN INTERMEDIATES Chemotactic signals promote recruitment into lung airspaces.

Neutrophil Recruitment -> Neutrophil Oxidant Release INDIRECT UNKNOWN INTERMEDIATES Recruited neutrophils can release this effector class after activation.

Neutrophil Recruitment -> Neutrophil Protease Release INDIRECT UNKNOWN INTERMEDIATES Recruited neutrophils can release this effector class after activation.

Neutrophil Oxidant Release -> Alveolar-Capillary Barrier Disruption INDIRECT UNKNOWN INTERMEDIATES Excess effector activity contributes to barrier-cell injury through multiple substrates and pathways.

Neutrophil Protease Release -> Alveolar-Capillary Barrier Disruption INDIRECT UNKNOWN INTERMEDIATES Excess effector activity contributes to barrier-cell injury through multiple substrates and pathways.

Alveolar-Capillary Barrier Disruption -> Protein-Rich Alveolar Edema DIRECT Increased permeability permits fluid and protein entry into airspaces.

Alveolar-Capillary Barrier Disruption -> Pulmonary Procoagulant Activation INDIRECT UNKNOWN INTERMEDIATES Epithelial injury may contribute to local procoagulant-factor release.

Alveolar-Capillary Barrier Disruption -> Alveolar Type 2 Cell Proliferation INDIRECT UNKNOWN INTERMEDIATES Surviving ATII cells can mount a regenerative response to epithelial injury.

Alveolar-Capillary Barrier Disruption -> Excess Pulmonary Collagen Deposition INDIRECT UNKNOWN INTERMEDIATES Dysregulated repair can include excessive fibroblast collagen deposition, but this is not inevitable.

Impaired Alveolar Fluid Clearance -> Protein-Rich Alveolar Edema INDIRECT UNKNOWN INTERMEDIATES Reduced epithelial transport contributes to persistence of alveolar fluid.

Protein-Rich Alveolar Edema -> Surfactant Dysfunction INDIRECT UNKNOWN INTERMEDIATES The protein-rich injury environment can impair surfactant activity.

Protein-Rich Alveolar Edema -> Intrapulmonary Shunting INDIRECT UNKNOWN INTERMEDIATES Perfusion of fluid-filled poorly ventilated units contributes to shunting.

Protein-Rich Alveolar Edema -> Increased Pulmonary Dead Space INDIRECT UNKNOWN INTERMEDIATES Edema and vascular injury contribute to impaired CO2 elimination.

Protein-Rich Alveolar Edema -> Noncardiogenic pulmonary edema INDIRECT UNKNOWN INTERMEDIATES This process contributes to the clinical manifestation.

Protein-Rich Alveolar Edema -> Bilateral pulmonary opacities INDIRECT UNKNOWN INTERMEDIATES This process contributes to the clinical manifestation.

Surfactant Dysfunction -> Alveolar Collapse INDIRECT UNKNOWN INTERMEDIATES Loss of surface-tension control favors alveolar collapse.

Alveolar Collapse -> Intrapulmonary Shunting INDIRECT UNKNOWN INTERMEDIATES Perfused collapsed lung units contribute to venous admixture.

Alveolar Collapse -> Ventilator-Induced Lung Injury INDIRECT UNKNOWN INTERMEDIATES Mechanical heterogeneity and cyclic recruitment can increase local strain.

Alveolar Collapse -> Atelectasis INDIRECT UNKNOWN INTERMEDIATES The process contributes to this clinical manifestation.

Intrapulmonary Shunting -> Hypoxemia INDIRECT UNKNOWN INTERMEDIATES This process contributes to the clinical manifestation.

Intrapulmonary Shunting -> Acute hypoxemic respiratory failure INDIRECT UNKNOWN INTERMEDIATES This process contributes to the clinical manifestation.

Intrapulmonary Shunting -> Dyspnea INDIRECT UNKNOWN INTERMEDIATES Gas-exchange impairment can contribute to this clinical sign through downstream physiological responses.

Intrapulmonary Shunting -> Tachypnea INDIRECT UNKNOWN INTERMEDIATES Gas-exchange impairment can contribute to this clinical sign through downstream physiological responses.

Intrapulmonary Shunting -> Cyanosis INDIRECT UNKNOWN INTERMEDIATES Gas-exchange impairment can contribute to this clinical sign through downstream physiological responses.

Increased Pulmonary Dead Space -> Hypercapnia INDIRECT UNKNOWN INTERMEDIATES The process contributes to this clinical manifestation.

Pulmonary Procoagulant Activation -> Intra-Alveolar Fibrin Deposition INDIRECT UNKNOWN INTERMEDIATES The procoagulant environment favors local fibrin deposition.

Ventilator-Induced Lung Injury -> Alveolar-Capillary Barrier Disruption INDIRECT UNKNOWN INTERMEDIATES Excess mechanical stress amplifies endothelial and epithelial injury.

Alveolar Type 2 Cell Proliferation -> Alveolar Type 2 to Type 1 Differentiation INDIRECT UNKNOWN INTERMEDIATES Expanded ATII progenitors can generate ATI cells during repair, with intermediate states unresolved here.

Excess Pulmonary Collagen Deposition -> Pulmonary fibrosis INDIRECT UNKNOWN INTERMEDIATES The process contributes to this clinical manifestation.

Show evidence (1 reference)

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"ARDS is an acute, diffuse, inflammatory lung injury precipitated by a risk factor such as pneumonia, nonpulmonary infection, trauma, transfusion, burn, aspiration, or shock. The resulting injury leads to pulmonary edema from an increase in pulmonary vascular and alveolar epithelial permeability."

The global consensus definition states the canonical insult-to-barrier-leak framework used by the main causal graph.

Immunometabolic Persistence and Metabolic Resilience Model

immunometabolic_resilience_model EMERGING

Evidence balance 1 support

Sustained glycolytic programming, impaired mitochondrial oxidative phosphorylation, redox imbalance, and bioactive metabolite signaling in immune and structural lung cells may amplify inflammation and delay alveolar-capillary repair. The related concept of metabolic resilience proposes that recovery depends partly on restoring coordinated mitochondrial function, substrate use, and redox balance. These mechanisms may help explain clinical heterogeneity, but they are not yet validated as a diagnostic endotype or treatment-selection framework.

Much of the pathway-level causality and therapeutic rationale is derived from experimental systems, sepsis extrapolation, or associative human multi-omics. No metabolism-targeted ARDS therapy or bedside metabolic-resilience assay has established prospective clinical utility.

Pathograph links

Alveolar Macrophage Activation -> Increased Glycolytic Programming INDIRECT UNKNOWN INTERMEDIATES Inflammatory macrophage activation can induce glycolytic reprogramming in experimental immunometabolic models; its magnitude and clinical relevance vary by context.

Increased Glycolytic Programming -> Pulmonary Cytokine and Chemokine Release INDIRECT UNKNOWN INTERMEDIATES Experimental immunometabolic models suggest that glycolytic programming can support inflammatory effector production; patient-specific causality remains unresolved.

Impaired Mitochondrial Respiration -> Impaired Alveolar Fluid Clearance INDIRECT UNKNOWN INTERMEDIATES Bioenergetic failure may compromise energy-dependent fluid transport; this is an emerging model rather than a universally demonstrated human pathway.

Show evidence (1 reference)

PMID:42432720 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Emerging evidence suggests that immunometabolic reprogramming, characterized by increased glycolysis, impaired mitochondrial oxidative phosphorylation, and altered metabolite signalling, plays a critical role in shaping immune-cell activation, inflammatory persistence, and tissue repair during..."

The issue's narrative review directly advances the immunometabolic model, while its wording and study design justify EMERGING rather than CANONICAL status.

Discussions and Knowledge Gaps

Do longitudinal immunometabolic states causally define reproducible ARDS endotypes that predict recovery and treatment response, and can metabolic resilience be measured prospectively well enough to guide therapy?

KNOWLEDGE GAP OPEN disc_ards_metabolic_endotype_validation

Attached to

pathophysiology#Increased Glycolytic Programming pathophysiology#Impaired Mitochondrial Respiration

The immunometabolic framework remains a hypothesis spanning experimental lung injury, sepsis and associative human omics. The cited BAL primary study measured early cross-sectional metabolites in 18 ARDS patients and eight healthy controls; it did not measure succinate or longitudinal persistence. The peripheral-blood single-cell study analyzed three ARDS patients and one healthy control, and pathway enrichment is not a direct measurement of oxidative stress or lung-cell respiration. Prospective compartment-specific functional and clinical validation is needed.

Show evidence (3 references)

PMID:42432720 SUPPORT DIRECT REVIEW SYNTHESIS Other

"However, the actual clinical translational value of this framework faces a major practical hurdle: no prospective randomized clinical trial has yet successfully implemented real-time metabolic endotyping at the bedside."

The review acknowledges the absence of prospective bedside metabolic-endotyping trials.

PMID:24289193 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Ultimately, it is our goal to construct a longitudinal metabolomics strategy to more fully characterize the ARDS metabolome that will drive biomarker discovery and the identification of drug target opportunities to improve the outcome of patients with ARDS."

Longitudinal profiling was a future goal of the BAL primary, not its design.

PMID:37283946 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"To this end, we performed scRNA-seq (10× Genomics) of peripheral blood single nuclei from one PNE-ARDS patient, two sep-ARDS patients, and one healthy volunteer (Figure 1A)."

The study contained three ARDS patients and one healthy control; blood-cell enrichment analyses cannot establish a universal lung mechanism.

⚙

Pathophysiology

Direct Pulmonary or Indirect Systemic Insult

Pneumonia, aspiration, inhalational injury, or lung contusion can directly injure the lung, whereas sepsis, pancreatitis, major trauma, shock, burns, and transfusion can initiate systemic inflammation and endothelial injury. These heterogeneous triggers converge on acute diffuse lung injury.

Alveolar-Capillary Permeability Injury Model

Alveolus of lung UBERON:0002299

Experimental models

Human airway-on-a-chip chlorine gas exposure model ORGAN ON CHIP Dose and duration jointly determine the measured barrier response. TEER recovered by 24 hours after 10 ppm for 10 minutes, whereas 30 ppm exposures caused nearly complete TEER reduction sustained through 24 hours. These data do not establish irreversible injury or recovery after every 10 ppm exposure.

Downstream

Alveolar Macrophage Activation Innate sensing connects pulmonary or systemic injury to macrophage activation.

Alveolar-Capillary Barrier Disruption Direct injury and systemic inflammatory pathways can increase barrier permeability.

Show evidence (1 reference)

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"ARDS is an acute, diffuse, inflammatory lung injury precipitated by a risk factor such as pneumonia, nonpulmonary infection, trauma, transfusion, burn, aspiration, or shock."

Consensus identifies heterogeneous direct pulmonary and systemic precipitating insults.

Alveolar Macrophage Activation

Pattern-recognition signaling activates resident alveolar macrophages after infection or tissue injury. This immune-cell state is distinct from secretion of its downstream mediators.

Alveolar-Capillary Permeability Injury Model Immunometabolic Persistence and Metabolic Resilience Model

alveolar macrophage CL:0000583

macrophage activation GO:0042116 ↑ INCREASED

Downstream

Pulmonary Cytokine and Chemokine Release Activated macrophages release inflammatory mediators.

Increased Glycolytic Programming Inflammatory macrophage activation can induce glycolytic reprogramming in experimental immunometabolic models; its magnitude and clinical relevance vary by context.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Activation of Toll-like receptors (not shown) on alveolar type II (ATII) cells and resident macrophages induces the secretion of chemokines, which recruit circulating immune cells into the airspaces."

Review synthesis links innate sensing on resident macrophages and ATII cells to chemokine secretion and immune recruitment.

Pulmonary Cytokine and Chemokine Release

Activated macrophages and structural lung cells release inflammatory mediators and chemoattractants, including IL-8/CXCL8, that recruit circulating leukocytes.

Alveolar-Capillary Permeability Injury Model

cytokine production GO:0001816 ↑ INCREASED

Experimental models

Organoid-derived Pseudomonas pneumonia-on-a-chip (VAP) model ORGAN ON CHIP Increasing cyclic strain from 5% to 10% modulates IL-6 and IL-8 release in the infected chip. Cytokine levels decrease under greater strain despite increased barrier injury.

Downstream

Neutrophil Recruitment Chemotactic signals promote recruitment into lung airspaces.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Intra-alveolar macrophages play an important part in releasing chemotactic factors such as IL-8 and chemokines such as CC-chemokine ligand 2 (also known as MCP1) that enhance the recruitment of neutrophils and monocytes into the lung, particularly in response to acute pulmonary infections."

The review identifies macrophage chemotactic-factor secretion and its role in leukocyte recruitment.

Neutrophil Recruitment

Circulating neutrophils enter the pulmonary interstitium and airspaces in response to chemotactic signals. Recruitment is separated from subsequent effector release.

Alveolar-Capillary Permeability Injury Model

neutrophil CL:0000775

neutrophil chemotaxis GO:0030593 ↑ INCREASED

Downstream

Neutrophil Oxidant Release Recruited neutrophils can release this effector class after activation.

Neutrophil Protease Release Recruited neutrophils can release this effector class after activation.

Show evidence (2 references)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

Review synthesis links innate sensing on resident macrophages and ATII cells to chemokine secretion and immune recruitment.

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"As neutrophils migrate across the epithelium, they release toxic mediators, including proteases, reactive oxygen species (ROS) and neutrophil extracellular traps (NETs), which have an important role in host defence but cause endothelial and epithelial injury."

Review synthesis separates neutrophil migration from the release of injurious oxidants, proteases and extracellular traps.

Neutrophil Oxidant Release

Recruited neutrophils release reactive oxygen species. Excessive oxidant activity can injure endothelial and epithelial barrier cells while also serving antimicrobial functions.

Alveolar-Capillary Permeability Injury Model

neutrophil CL:0000775

reactive oxygen species metabolic process GO:0072593 ↑ INCREASED

Downstream

Alveolar-Capillary Barrier Disruption Excess effector activity contributes to barrier-cell injury through multiple substrates and pathways.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

Review synthesis separates neutrophil migration from the release of injurious oxidants, proteases and extracellular traps.

Neutrophil Protease Release

Neutrophils release proteolytic effectors during host defense; excessive extracellular activity can contribute to tissue and barrier injury.

Alveolar-Capillary Permeability Injury Model

neutrophil CL:0000775

Downstream

Alveolar-Capillary Barrier Disruption Excess effector activity contributes to barrier-cell injury through multiple substrates and pathways.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

Review synthesis separates neutrophil migration from the release of injurious oxidants, proteases and extracellular traps.

Alveolar-Capillary Barrier Disruption

Increased endothelial and epithelial permeability permits protein-rich fluid to cross into the interstitium and alveoli. Functional junctional changes can occur without endothelial cell death or dramatic endothelial morphological damage. Reduced epithelial fluid transport is represented separately.

Alveolar-Capillary Permeability Injury Model

Pulmonary alveolar type 1 cell CL:0002062 Pulmonary alveolar type 2 cell CL:0002063 Pulmonary capillary endothelial cell CL:4028001

Experimental models

Human airway-on-a-chip chlorine gas exposure model ORGAN ON CHIP Immediate epithelial gaps and endothelial junction disruption detected at 72 hours are consistent with secondary endothelial injury. The timing does not establish the intervening signal or exclude an independent delayed chemical effect.

Organoid-derived Pseudomonas pneumonia-on-a-chip (VAP) model ORGAN ON CHIP Infection plus greater chip strain increased apparent permeability and vascular-channel bacterial counts. These readouts model aspects of barrier dysfunction without reproducing the full syndrome.

Downstream

Protein-Rich Alveolar Edema Increased permeability permits fluid and protein entry into airspaces.

Pulmonary Procoagulant Activation Epithelial injury may contribute to local procoagulant-factor release.

Alveolar Type 2 Cell Proliferation Surviving ATII cells can mount a regenerative response to epithelial injury.

Excess Pulmonary Collagen Deposition Dysregulated repair can include excessive fibroblast collagen deposition, but this is not inevitable.

Show evidence (2 references)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Increased alveolar–capillary permeability to fluid, proteins, neutrophils and red blood cells (resulting in their accumulation into the alveolar space) is the hallmark of ARDS36–38."

Permeability to fluid and protein is the defining functional barrier abnormality.

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Thus, in animal models and human ARDS, changes in paracellular permeability to protein seem to occur in the absence of dramatic alterations in the morphology of the lung endothelium."

The review cautions that functional permeability changes need not entail dramatic endothelial morphological injury.

Impaired Alveolar Fluid Clearance

Reduced epithelial sodium-channel and Na+/K+-ATPase function limits active removal of alveolar fluid. Both type I and type II alveolar epithelial cells contribute to transport.

Alveolar-Capillary Permeability Injury Model

Pulmonary alveolar type 1 cell CL:0002062 Pulmonary alveolar type 2 cell CL:0002063

sodium ion transport GO:0006814 ↓ DECREASED

Downstream

Protein-Rich Alveolar Edema Reduced epithelial transport contributes to persistence of alveolar fluid.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Influenza infection, hypoxaemia, hypercapnia and other factors downregulate sodium channel and/or Na+/K+-ATPase function, resulting in impaired alveolar fluid clearance in patients with ARDS35,75,87,88."

Impaired epithelial sodium transport reduces alveolar fluid clearance; this is distinct from increased fluid entry.

Protein-Rich Alveolar Edema

Permeability-mediated fluid entry and insufficient clearance cause protein-rich alveolar flooding. Hydrostatic loading can coexist, but does not primarily explain the syndrome.

Alveolar-Capillary Permeability Injury Model

Downstream

Surfactant Dysfunction The protein-rich injury environment can impair surfactant activity.

Intrapulmonary Shunting Perfusion of fluid-filled poorly ventilated units contributes to shunting.

Increased Pulmonary Dead Space Edema and vascular injury contribute to impaired CO2 elimination.

Noncardiogenic pulmonary edema This process contributes to the clinical manifestation.

Bilateral pulmonary opacities This process contributes to the clinical manifestation.

Show evidence (2 references)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"In ARDS, there is increased permeability to liquid and protein across the lung endothelium, which then leads to oedema in the lung interstitium."

Increased endothelial permeability produces interstitial edema, with alveolar accumulation when the epithelial barrier also fails.

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Increased alveolar–capillary permeability to fluid, proteins, neutrophils and red blood cells (resulting in their accumulation into the alveolar space) is the hallmark of ARDS36–38."

Permeability to fluid and protein is the defining functional barrier abnormality.

Surfactant Dysfunction

Alveolar epithelial injury and the protein-rich edema environment impair the surface-tension-lowering function of surfactant.

Alveolar-Capillary Permeability Injury Model

Downstream

Alveolar Collapse Loss of surface-tension control favors alveolar collapse.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"In addition, the many biological changes resulting from both endothelial and epithelial injury, and culminating in protein-rich oedematous fluid, contribute to surfactant dysfunction90."

Protein-rich edema and injury can impair surfactant function.

Alveolar Collapse

Surfactant dysfunction and the gravitational effects of an edematous lung promote regional alveolar collapse, reducing aerated lung volume.

Alveolar-Capillary Permeability Injury Model

Downstream

Intrapulmonary Shunting Perfused collapsed lung units contribute to venous admixture.

Ventilator-Induced Lung Injury Mechanical heterogeneity and cyclic recruitment can increase local strain.

Atelectasis The process contributes to this clinical manifestation.

Show evidence (2 references)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Surfactant dysfunction can then increase atelectasis, which in turn can increase the risk of biophysical injury."

The review links surfactant dysfunction to alveolar collapse and secondary mechanical injury.

PMID:37326646 SUPPORT DIRECT REVIEW SYNTHESIS Other

"In patients with ARDS, surfactant dysfunction, effects of gravity on the edematous lung, and heterogeneous injury predispose to regional lung derecruitment with alveolar collapse and small airways closure [103]."

Guideline synthesis identifies surfactant dysfunction and gravitational loading as contributors to derecruitment.

Intrapulmonary Shunting

Blood flow through poorly ventilated or nonventilated lung units impairs oxygenation. Shunting is a physiological process, distinct from its clinical hypoxemia and respiratory-failure outcomes.

Alveolar-Capillary Permeability Injury Model

Downstream

Hypoxemia This process contributes to the clinical manifestation.

Acute hypoxemic respiratory failure This process contributes to the clinical manifestation.

Dyspnea Gas-exchange impairment can contribute to this clinical sign through downstream physiological responses.

Tachypnea Gas-exchange impairment can contribute to this clinical sign through downstream physiological responses.

Cyanosis Gas-exchange impairment can contribute to this clinical sign through downstream physiological responses.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Arterial hypoxaemia in patients with ARDS is caused by ventilation-to-perfusion mismatch as well as right-to-left intrapulmonary shunting."

The review identifies intrapulmonary shunting and ventilation-perfusion mismatch as causes of hypoxemia.

Increased Pulmonary Dead Space

Pulmonary vascular injury and edema reduce effective carbon-dioxide elimination, increasing physiological dead space and sometimes causing hypercapnia.

Alveolar-Capillary Permeability Injury Model

Downstream

Hypercapnia The process contributes to this clinical manifestation.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The vascular injury and alveolar oedema contribute to the decreased ability to excrete CO2 (hypercapnia), accounting for the elevated pulmonary dead space in acute respiratory distress syndrome."

Review synthesis connects pulmonary vascular injury and edema with impaired CO2 elimination.

Pulmonary Procoagulant Activation

Injured alveolar epithelial cells and the local inflammatory environment can favor procoagulant activity. This is distinct from the resulting fibrin deposits.

Alveolar-Capillary Permeability Injury Model

regulation of coagulation GO:0050818 ↕ DYSREGULATED

Downstream

Intra-Alveolar Fibrin Deposition The procoagulant environment favors local fibrin deposition.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Injured but intact alveolar epithelial cells seem to drive release of pro-coagulant factors and intra-alveolar fibrin deposition49,50, which is also deposited adjacent to endothelial cells in injured alveoli37,40,47."

The review proposes epithelial procoagulant activity as a contributor to alveolar fibrin deposition.

Intra-Alveolar Fibrin Deposition

Fibrin accumulates within injured alveoli and near the pulmonary endothelium. It is a component of the injury pattern rather than proof that fibrosis must follow.

blood coagulation, fibrin clot formation GO:0072378 ↑ INCREASED

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

The review proposes epithelial procoagulant activity as a contributor to alveolar fibrin deposition.

Ventilator-Induced Lung Injury

Excessive tidal deformation, overdistension and repeated opening and closure can amplify epithelial and endothelial injury in the reduced aerated lung. Exposure depends on ventilator settings, lung mechanics and patient effort.

Alveolar-Capillary Permeability Injury Model

Experimental models

Organoid-derived Pseudomonas pneumonia-on-a-chip (VAP) model ORGAN ON CHIP Increasing chip strain raised baseline apparent permeability slightly and, after infection, increased vascular bacterial counts and permeability. This demonstrates a mechanical-infectious interaction in this cell system without establishing the size of a clinical ventilation effect.

Downstream

Alveolar-Capillary Barrier Disruption Excess mechanical stress amplifies endothelial and epithelial injury.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"High tidal volume and elevated airway pressure induce biomechanical inflammatory injury and necrosis of the lung endothelium and alveolar epithelium that are associated with release of neutrophil products, including proteases, oxidants and pro-inflammatory cytokines, and a reduction in the..."

Mechanical ventilation can add biomechanical injury to the endothelial and epithelial barriers.

Increased Glycolytic Programming

Inflammatory activation can shift cellular metabolism toward glycolysis. Its magnitude and persistence vary by cell type and compartment; a uniform glycolysis-dominant state is not established in every patient with ARDS.

Immunometabolic Persistence and Metabolic Resilience Model

glycolytic process GO:0006096 ↑ INCREASED

Downstream

Pulmonary Cytokine and Chemokine Release Experimental immunometabolic models suggest that glycolytic programming can support inflammatory effector production; patient-specific causality remains unresolved.

Show evidence (1 reference)

PMID:42432720 SUPPORT DIRECT REVIEW SYNTHESIS Other

"When macrophages encounter inflammatory stimuli, they shift from mitochondrial oxidative phosphorylation to aerobic glycolysis, a phenomenon called as the “Warburg effect.” This metabolic transition enables rapid ATP generation and provides biosynthetic intermediates required for cytokine..."

A narrative review summarizes experimental immunometabolic mechanisms; this does not measure glycolytic flux in a representative ARDS cohort.

Impaired Mitochondrial Respiration

Reduced mitochondrial oxidative phosphorylation may compromise energy-dependent cellular functions during lung injury. Human metabolite or blood transcriptomic associations alone do not establish impaired respiration in a particular lung cell population.

Immunometabolic Persistence and Metabolic Resilience Model

oxidative phosphorylation GO:0006119 ↓ DECREASED

Downstream

Impaired Alveolar Fluid Clearance Bioenergetic failure may compromise energy-dependent fluid transport; this is an emerging model rather than a universally demonstrated human pathway.

Show evidence (1 reference)

PMID:42432720 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Disruptions in bioenergetic homeostasis, including impaired mitochondrial oxidative phosphorylation, altered glycolytic flux, defective fatty acid oxidation, and redox imbalance have increasingly been linked to persistent organ dysfunction and adverse outcomes in ARDS and sepsis [6–8]."

The review presents mitochondrial bioenergetic failure as a proposed contributor, with evidence spanning experimental lung injury and critical illness.

Alveolar Type 2 Cell Proliferation

Surviving ATII cells proliferate during epithelial regeneration, supplying replacement epithelial cells and a provisional barrier. This response does not guarantee complete recovery.

Alveolar-Capillary Permeability Injury Model

pulmonary alveolar type 2 cell CL:0002063

Downstream

Alveolar Type 2 to Type 1 Differentiation Expanded ATII progenitors can generate ATI cells during repair, with intermediate states unresolved here.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"To repair the damaged epithelium, surviving alveolar type II (ATII) cells replace lost epithelial cells via proliferation and differentiation into alveolar type I (ATI) cells."

Proliferation and subsequent differentiation are distinct epithelial repair processes; detailed lineage evidence is largely experimental.

Alveolar Type 2 to Type 1 Differentiation

ATII-derived cells can differentiate into thin ATI cells during alveolar repair. Lineage and signaling details are supported largely by experimental models, rather than direct lineage tracing in patients.

pulmonary alveolar type 2 cell CL:0002063 pulmonary alveolar type 1 cell CL:0002062

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"To repair the damaged epithelium, surviving alveolar type II (ATII) cells replace lost epithelial cells via proliferation and differentiation into alveolar type I (ATI) cells."

Proliferation and subsequent differentiation are distinct epithelial repair processes; detailed lineage evidence is largely experimental.

Excess Pulmonary Collagen Deposition

Fibroblast collagen deposition can become excessive during dysregulated repair and contribute to persistent fibrotic structural change. This is an alternative nonresolving course in a subset, not an obligatory stage.

Alveolar-Capillary Permeability Injury Model

collagen biosynthetic process GO:0032964 ↑ INCREASED

Downstream

Pulmonary fibrosis The process contributes to this clinical manifestation.

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Fibroblasts secrete epithelial growth factors and deposit collagen, which, if excessive, can lead to fibrosis."

Fibroblast collagen deposition can become excessive and contribute to fibrosis.

✶

Histopathology

Diffuse Alveolar Damage with Hyaline Membrane Formation

ARDS histology can show intraalveolar edema, inflammation, hyaline membrane formation, and alveolar hemorrhage in a diffuse-alveolar-damage pattern. These findings are variable and are neither universal nor required for the clinical diagnosis.

Show evidence (1 reference)

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Histological findings vary and often include intraalveolar edema, inflammation, hyaline membrane formation, and alveolar hemorrhage, often termed diffuse alveolar damage; however, these histological features are not always present and are not necessary for a clinical diagnosis of ARDS (26)."

The consensus document supports the characteristic diffuse-alveolar-damage pattern and directly supplies the non-universality and diagnostic caveat.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

Cardiovascular 1

Tachycardia HP:0001649

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"On physical examination, they appear to be in moderate or severe respiratory distress with an elevated respiratory rate and tachycardia and they usually are working harder than normal to breathe."

The same examination description explicitly identifies tachycardia.

Integument 1

Cyanosis HP:0000961

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Hypoxaemia may manifest with evidence of cyanosis in their fingernail beds."

The review describes nail-bed cyanosis as a possible manifestation of hypoxemia.

Metabolism 1

Noncardiogenic pulmonary edema HP:0100598

Show evidence (1 reference)

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The resulting injury leads to pulmonary edema from an increase in pulmonary vascular and alveolar epithelial permeability."

The consensus model directly links permeability injury to pulmonary edema.

Musculoskeletal 2

Muscle weakness HP:0001324

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"With more detailed follow-up evaluations, these investigators observed that survivors of ARDS had significant exercise limitation and poor physical QOL at 1-year follow-up related to marked muscle wasting and weakness; myriad physical disabilities including heterotopic ossification, joint..."

The survivor review explicitly reports weakness; critical illness and treatment can also contribute.

Skeletal muscle atrophy HP:0003202

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

The survivor review reports muscle wasting, distinct from measured weakness alone.

Nervous System 2

Memory impairment HP:0002354

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"They noted important decrements in attention, concentration, processing speed, memory and executive function that persisted up to 2 years after discharge from intensive care222,223."

The review explicitly identifies persistent memory deficits among the observed cognitive outcomes.

Posttraumatic stress symptoms HP:0033676

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Post-traumatic stress disorder in patients with ARDS has also been described and is associated with decrements in the mental health domains of the 36-Item Short Form Survey (SF-36) QOL measure213."

The review identifies post-traumatic stress disorder and its association with mental-health quality of life.

Respiratory 9

Hypoxemia HP:0012418

Show evidence (1 reference)

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The clinical hallmarks of ARDS are arterial hypoxemia and bilateral radiographic opacities associated with increased shunting, increased alveolar dead space, and decreased lung compliance."

The consensus definition names arterial hypoxemia as a clinical hallmark.

Acute hypoxemic respiratory failure HP:0002878

Show evidence (1 reference)

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Acute respiratory distress syndrome (ARDS) is a clinical syndrome of acute hypoxemic respiratory failure due to lung inflammation, not caused by cardiogenic pulmonary edema."

The global consensus situates ARDS within acute hypoxemic respiratory failure.

Bilateral pulmonary opacities Pulmonary opacity HP:0031457

Show evidence (1 reference)

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The committee agreed that chest imaging criteria should include bilateral radiologic (chest radiography or computed tomography) or ultrasound findings suggestive of loss of lung aeration that are not fully explained by effusions, atelectasis, or nodules/masses."

The global definition specifies bilateral imaging abnormalities and the principal exclusions.

Dyspnea HP:0002094

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Most patients who present with the early phase of acute lung injury complain of feeling short of breath."

The clinical review explicitly reports early breathlessness.

Tachypnea HP:0002789

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"On physical examination, they appear to be in moderate or severe respiratory distress with an elevated respiratory rate and tachycardia and they usually are working harder than normal to breathe."

The physical-examination description identifies an elevated respiratory rate.

Hypercapnia HP:0012416

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The vascular injury and alveolar oedema contribute to the decreased ability to excrete CO2 (hypercapnia), accounting for the elevated pulmonary dead space in acute respiratory distress syndrome."

The review links impaired carbon-dioxide excretion to pulmonary dead-space abnormalities.

Atelectasis HP:0100750

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Surfactant dysfunction can then increase atelectasis, which in turn can increase the risk of biophysical injury."

The review identifies regional collapse as a consequence of surfactant dysfunction.

Pulmonary fibrosis HP:0002206

Show evidence (1 reference)

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Fibroblasts secrete epithelial growth factors and deposit collagen, which, if excessive, can lead to fibrosis."

The conditional wording supports possible excessive collagen deposition rather than inevitable fibrosis.

Crackles HP:0030830

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK436002/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"Chest auscultation usually reveals rales, especially bibasilar"

The clinical examination review reports rales as an acute finding.

Constitutional 1

Exercise intolerance HP:0003546

Show evidence (1 reference)

PMID:21470008 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"CONCLUSIONS: Exercise limitation, physical and psychological sequelae, decreased physical quality of life, and increased costs and use of health care services are important legacies of severe lung injury."

The follow-up study identifies persistent exercise limitation after severe lung injury.

🧬

Genetic Associations

12p13.2 susceptibility locus (rs7967111) (Population association with ARDS susceptibility; not a Mendelian cause or clinical diagnostic test)

Show evidence (3 references)

PMID:34032881 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"METHODS: Meta-analyses of ARDS genome-wide association studies were performed with 1250 cases and 1583 controls in Europeans, and 387 cases and 387 controls in African Americans."

The primary study states ancestry-specific GWAS sample sizes.

PMID:34032881 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Intriguingly, rs7967111 exceeded genome-wide significance (P < 5 × 10–8), with OR of 1.38 (P = 2.15 × 10–8; Table 1) after adjusting for potential confounders."

The stronger association comes from the sensitivity analysis.

PMID:34032881 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Unexpectedly, no loci achieved genome-wide significance, even at the empirical threshold of P < 1 × 10−6 (Fig. E5)."

Cross-ancestry inference remains limited.

💊

Medical Actions

Etiology-Directed and Intensive Supportive Care

Action: supportive care Ontology label: Supportive Care NCIT:C15747

Identify and treat the precipitating cause while providing oxygenation, hemodynamic support, infection management when indicated, prevention of secondary injury, and organ support. ARDS has no single etiology-specific pharmacologic cure, so supportive strategies are selected by severity and patient context.

Target Phenotypes: Respiratory failure HP:0002878

Show evidence (1 reference)

PMID:39866839 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Given the complexity of the underlying disease, treatment needs to be tailored to the problem."

The review supports etiology- and context-specific management of this heterogeneous syndrome.

Adult lung-protective mechanical ventilation

Action: mechanical ventilation Ontology label: Mechanical Ventilation NCIT:C70909

Strong recommendation, moderate certainty: 4–8 mL/kg predicted body weight with plateau pressure <30 cm H2O. This retained recommendation is broader than the pivotal 6 mL/kg trial protocol.

Mechanism Target:

INHIBITS Ventilator-Induced Lung Injury — Lower tidal volume and plateau-pressure limitation reduce injurious mechanical stretch during invasive ventilation.

Show evidence (1 reference)

PMID:10793162 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Traditional approaches to mechanical ventilation use tidal volumes of 10 to 15 ml per kilogram of body weight and may cause stretch-induced lung injury in patients with acute lung injury and the acute respiratory distress syndrome."

The trial directly motivates lower-volume ventilation as prevention of stretch-induced lung injury.

Target Phenotypes: Respiratory failure HP:0002878

Show evidence (1 reference)

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We recommend using mechanical ventilation strategies that limit tidal volume (4–8 mL/kg predicted body weight) and inspiratory pressures (plateau pressure <30 cm H2O) in patients with ARDS (strong recommendation, moderate certainty of evidence)."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

Adult prone positioning

Action: Prone Ventilation NCIT:C173751

For severe adult ARDS, >12 hours daily is strongly recommended with moderate certainty. Individual primary trials may use a longer protocol. ESICM recommends starting after stabilization and optimized ventilation when PaO2/FiO2 remains below 150 mm Hg, with sessions of at least 16 consecutive hours. PROSEVA used this prolonged protocol; its trial outcome applies to the selected study population.

Mechanism Target:

MODULATES Intrapulmonary Shunting — Proning redistributes ventilation and perfusion and recruits dependent lung, thereby improving oxygenation across the shunt-dominated physiology.

Show evidence (1 reference)

PMID:39866839 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The prone position is a readily implementable intervention associated with improved oxygenation due to an increased ventilator–blood flow ratio, more uniform ventilation distribution, increased lung volume, and improved perfusion redistribution during partial alveolar re-expansion in the..."

The review directly links prone positioning to redistribution of ventilation and perfusion and improved oxygenation.

Target Phenotypes: Hypoxemia HP:0012418

Show evidence (2 references)

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We recommend prone positioning for >12 hours per day in patients with severe ARDS (strong recommendation, moderate certainty of evidence)."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:37326646 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Therefore, the evidence used for this question is the same as that for previous the question.Recommendation 7.2We recommend starting prone position in patients with ARDS receiving invasive mechanical ventilation early after intubation, after a period of stabilization during which low tidal..."

The ESICM recommendation specifies timing, oxygenation and session duration.

Conservative Fluid Management After Hemodynamic Stabilization

Action: fluid therapy Ontology label: Fluid Therapy NCIT:C116537

In adults after shock and tissue hypoperfusion have resolved, conservative fluid management can limit superimposed hydrostatic loading. FACTT randomized 1000 patients for seven days: ventilator-free days improved, but 60-day mortality did not differ significantly. This is not fluid restriction during active shock.

Mechanism Target:

INHIBITS Protein-Rich Alveolar Edema — After hemodynamic stabilization, conservative fluid management limits the fluid burden superimposed on permeability edema and improves lung function.

Show evidence (1 reference)

PMID:16714767 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Although there was no significant difference in the primary outcome of 60-day mortality, the conservative strategy of fluid management improved lung function and shortened the duration of mechanical ventilation and intensive care without increasing nonpulmonary-organ failures."

FACTT directly demonstrates improved lung function from the conservative strategy while retaining its neutral mortality result.

Target Phenotypes: Pulmonary edema HP:0100598

Show evidence (2 references)

PMID:16714767 SUPPORT DIRECT PRIMARY RESULT Human Clinical

The randomized FACTT trial supports conservative management for pulmonary and support-duration outcomes while preserving its neutral mortality result.

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"In 2006, a randomized clinical trial in 1,000 patients with ARDS demonstrated that adopting a fluid-conservative approach after vasopressor-dependent shock had resolved led to an increase in ventilator-free days and improved oxygenation index185."

The review specifies the clinical timing boundary for fluid-conservative management.

Adult corticosteroids

Action: systemic corticosteroid therapy Ontology label: Systemic Corticosteroid Therapy NCIT:C122080

Agent: corticosteroid CHEBI:50858

Conditional recommendation with moderate certainty specifically applies to intubated adults. Agent, dose and duration remain unresolved; timing and etiology matter and initiation beyond two weeks may be harmful.

Mechanism Target:

INHIBITS Pulmonary Cytokine and Chemokine Release — Anti-inflammatory corticosteroids inhibit synthesis of proinflammatory mediators; clinical selection remains population- and timing-dependent.

Show evidence (1 reference)

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Corticosteroids are anti-inflammatory medications that inhibit the synthesis of proinflammatory mediators present in ARDS."

The guideline directly states the anti-inflammatory mechanism used to join corticosteroid treatment to cytokine activation.

Target Phenotypes: Respiratory failure HP:0002878

Show evidence (3 references)

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We suggest using corticosteroids for patients with ARDS (conditional recommendation, moderate certainty of evidence)."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"this recommendation is based on evidence from trials on intubated patients with ARDS and applies specifically to this group"

The population is explicitly intubated ARDS.

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"the initiation of corticosteroid treatment >2 weeks after the onset of ARDS may be associated with harm"

Late initiation caveat from the implementation discussion.

Adult higher PEEP without prolonged recruitment

Action: mechanical ventilation Ontology label: Mechanical Ventilation NCIT:C70909

Conditional recommendation for higher PEEP without recruitment maneuvers in moderate-to-severe adult ARDS. Prolonged recruitment (PEEP ≥35 cm H2O for >60 seconds) is strongly discouraged. Titrate with respiratory and hemodynamic monitoring; mild ARDS does not inherit this recommendation. ESICM found insufficient evidence to recommend routine higher versus lower PEEP/FiO2 titration for mortality across all ARDS. The ATS conditional recommendation is restricted to moderate-to-severe disease.

Target Phenotypes: Hypoxemia HP:0012418

Show evidence (3 references)

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We suggest using higher PEEP without LRMs rather than lower PEEP in patients with moderate to severe ARDS (conditional recommendation, low-moderate certainty)."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We recommend against using prolonged (PEEP ⩾35 cm H2O for >60 s) LRMs in patients with moderate to severe ARDS (strong recommendation, moderate certainty)."

The negative recruitment recommendation is stronger than the conditional PEEP recommendation.

PMID:37326646 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We are unable to make a recommendation for or against routine PEEP titration with a higher PEEP/FiO2 strategy versus a lower PEEP/FiO2 strategy to reduce mortality in patients with ARDS."

The broader ESICM population and analysis should not be conflated with the ATS conditional recommendation.

Adult neuromuscular blockade

Action: neuromuscular blockade Ontology label: Neuromuscular Blockade NCIT:C158070

Agent: cisatracurium CHEBI:140621

Conditional recommendation, low certainty, for early (<48 hours) severe ARDS (PaO2/FiO2 ≤100). Use selectively when deep sedation is already required or persistent dyssynchrony compromises protection. Limit duration to 48 hours when possible; mortality advantage was not established against light sedation. ESICM 2023 recommends against routine continuous infusions for mortality reduction in unselected moderate-to-severe non-COVID ARDS; this differs in scope from ATS selective early severe use. ICU-acquired weakness and sedation harms matter.

Mechanism Target:

INHIBITS Ventilator-Induced Lung Injury — In selected early severe ARDS, blockade can reduce patient-ventilator dyssynchrony and thereby limit ventilator-induced injury.

Show evidence (1 reference)

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"NMBAs are a commonly used adjunctive therapy for patients with ARDS (16, 56). The mechanism of benefit is unclear, but likely involves decreasing ventilator-induced lung injury via a reduction in patient–ventilator dyssynchrony in addition to reducing oxygen consumption, inflammation, and..."

The guideline explicitly links neuromuscular blockade to reduced dyssynchrony and likely reduction of ventilator-induced injury.

Target Phenotypes: Respiratory failure HP:0002878

Show evidence (3 references)

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We suggest using neuromuscular blockade in patients with early severe ARDS (conditional recommendation, low certainty)"

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"NMBA duration should be limited to a maximum of 48 hours whenever possible."

The guideline limits treatment duration when feasible.

PMID:37326646 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Only indirect evidence from non-COVID studies was available.Recommendation 8.1We recommend against the routine use of continuous infusions of NMBA to reduce mortality in patients with moderate-to-severe ARDS not due to COVID-19.Strong recommendation, moderate level of evidence.We are unable to..."

The ESICM recommendation argues against indiscriminate continuous blockade.

Adult venovenous ECMO

Action: extracorporeal membrane oxygenation Ontology label: Extracorporeal Membrane Oxygenation NCIT:C171507

Conditional recommendation, low certainty, for selected severe adult ARDS despite optimized care. Consider reversibility, very severe gas-exchange impairment, early disease, futility risk and center expertise. VV-ECMO supports oxygenation and carbon-dioxide removal; bleeding is a material harm.

Mechanism Target:

BYPASSES Intrapulmonary Shunting — Extracorporeal oxygenation and CO2 removal support gas exchange while the lung recovers; VV-ECMO does not directly provide circulatory support or repair the barrier.

Show evidence (1 reference)

PMID:37326646 SUPPORT DIRECT REVIEW SYNTHESIS Other

"VV-ECMO is used to support or replace gas exchange."

The guideline describes extracorporeal gas exchange rather than direct hemodynamic support.

Target Phenotypes: Respiratory failure HP:0002878

Show evidence (1 reference)

PMID:38032683 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We suggest the use of VV-ECMO in selected patients with severe ARDS (conditional recommendation, low certainty of evidence)"

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

High-flow nasal oxygen in adult acute hypoxemic respiratory failure

Action: High-Flow Nasal Cannula Oxygen Therapy NCIT:C171510

ESICM strongly recommends HFNO over conventional oxygen for nonventilated adult acute hypoxemic respiratory failure not due to cardiogenic edema or COPD exacerbation, to reduce intubation risk. Mortality benefit was not established. Close monitoring and timely escalation are necessary; this evidence is broader than Berlin-defined ARDS.

Show evidence (1 reference)

PMID:37326646 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We recommend that non-mechanically ventilated patients with AHRF not due to cardiogenic pulmonary edema or acute exacerbation of COPD receive HFNO as compared to conventional oxygen therapy to reduce the risk of intubation"

This recommendation addresses intubation risk in a defined noncardiogenic AHRF population, not all ARDS outcomes.

Avoid prolonged high-pressure recruitment maneuvers in adult ARDS

Action: Mechanical Ventilation NCIT:C70909

Prolonged high-pressure recruitment is strongly discouraged because potential harms include hemodynamic collapse and barotrauma. ESICM defines airway pressure at least 35 cm H2O for at least one minute; the ATS definition uses PEEP at least 35 cm H2O for more than 60 seconds.

Show evidence (1 reference)

PMID:37326646 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We recommend against use of prolonged high-pressure recruitment maneuvers (defined as airway pressure maintained ≥ 35 cmH2O for at least one minute) to reduce mortality of patients with ARDS."

The recommendation explicitly discourages the specified prolonged maneuver for mortality reduction.

Avoid routine brief high-pressure recruitment maneuvers in adult ARDS

Action: Mechanical Ventilation NCIT:C70909

ESICM suggests against routine brief high-pressure recruitment for mortality reduction. Selected derecruitment episodes may warrant individualized rescue with monitoring and immediate cessation if cardiovascular instability occurs; this is not routine recruitment.

Show evidence (1 reference)

PMID:37326646 SUPPORT DIRECT REVIEW SYNTHESIS Other

"routine use of brief high-pressure recruitment maneuvers (defined as airway pressure maintained ≥ 35 cmH2O for less than one minute) to reduce mortality in patients with ARDS.Weak recommendation; high level of evidence of no effect.This suggestion applies also to ARDS from COVID-19.Weak..."

The recommendation discourages routine brief maneuvers; it does not prohibit individualized monitored rescue in every circumstance.

Restrict extracorporeal carbon-dioxide removal to trials

Action: Supportive Care NCIT:C15747

ESICM recommends against ECCO2R for mortality prevention outside randomized trials. It differs from VV-ECMO and has bleeding risks without demonstrated survival benefit in the analyzed trials.

Show evidence (1 reference)

PMID:37326646 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We recommend against the use of ECCO2R for the treatment of ARDS not due to COVID-19 to prevent mortality outside of randomized controlled trials."

The recommendation restricts ECCO2R for mortality prevention to randomized trials.

Pediatric lung-protective ventilation

Action: Mechanical Ventilation NCIT:C70909

Conditional recommendations: 6–8 mL/kg, lower if pressure limits require, caution below 4 mL/kg; plateau ≤28 cm H2O (29–32 may be acceptable with reduced chest-wall compliance), driving pressure ≤15. Scale volumes to the lesser of predicted or actual weight.

Target Phenotypes: Respiratory failure HP:0002878

Show evidence (2 references)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We suggest the use of physiologic tidal volumes between 6 and 8 mL/kg in patients with PARDS compared with supraphysiologic tidal volumes (> 8 mL/kg)."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The lesser of predicted body weight or actual body weight should be used."

Pediatric weight-scaling differs from a simple adult PBW rule.

Pediatric PEEP titration

Action: Mechanical Ventilation NCIT:C70909

Typically maintain PEEP at or above the lower-PEEP/higher-FiO2 ARDSNet table (strong, moderate certainty); individualize to oxygen delivery, hemodynamics and static compliance while respecting pressure limits. Sustained inflation recruitment cannot be recommended.

Target Phenotypes: Hypoxemia HP:0012418

Show evidence (2 references)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We recommend that PEEP levels should typically be maintained at or above the lower PEEP/higher Fio2 table from the ARDS Network protocol"

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Sustained inflation maneuvers cannot be recommended."

Routine adult recruitment strategies must not be imported.

Pediatric selective corticosteroid use

Action: systemic corticosteroid therapy Ontology label: Systemic Corticosteroid Therapy NCIT:C122080

Agent: corticosteroid CHEBI:50858

The guideline conditionally recommends against routine steroids, with low certainty. Selected etiologies such as SARS-CoV-2 may differ; this is separate from the adult ATS recommendation.

Show evidence (1 reference)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We suggest against the routine use of corticosteroids in patients with PARDS compared with selective use of steroids."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

Pediatric selective neuromuscular blockade

Action: neuromuscular blockade Ontology label: Neuromuscular Blockade NCIT:C158070

Agent: cisatracurium CHEBI:140621

Use minimal effective blockade with sedation only when protective ventilation cannot otherwise be achieved; conditional, very-low certainty. Monitor and titrate to the intended depth. No universal adult early/severe timing rule is implied.

Show evidence (1 reference)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We suggest that minimal, yet effective, neuromuscular blockade (NMB) be used in conjunction with sedation in comparison to the use of sedation alone if effective and protective MV cannot be achieved."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

Pediatric prone-positioning trial

Action: Prone Ventilation NCIT:C173751

Evidence is insufficient to recommend for or against routine proning. It can be considered for refractory hypoxemia, with response assessed; no duration recommendation is established.

Show evidence (2 references)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"There are insufficient data to support or refute the use of prone positioning in patients with PARDS."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We cannot make recommendations on the duration of prone positioning."

Adult prone-duration rules are not pediatric evidence.

Pediatric ECMO evaluation

Action: extracorporeal membrane oxygenation Ontology label: Extracorporeal Membrane Oxygenation NCIT:C171507

Evaluate potentially reversible severe PARDS when protective ventilation fails gas exchange, using serial expert assessment. There are no strict supported selection cutoffs. Prefer venovenous ECMO when cardiac function is adequate; pediatric recommendations are conditional.

Target Phenotypes: Respiratory failure HP:0002878

Show evidence (3 references)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We suggest that patients with a potentially reversible cause of severe PARDS should be evaluated for extracorporeal membrane oxygenation (ECMO) when lung protective strategies result in inadequate gas exchange."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"There is no evidence to support strict criteria for the selection of patients who will benefit from ECMO in PARDS."

Adult numerical eligibility cutoffs cannot be assumed.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We suggest the use of venovenous ECMO over venoarterial ECMO in patients with PARDS who have adequate cardiac function."

Cardiac adequacy qualifies the preferred circuit.

Pediatric fluid management

Action: fluid therapy Ontology label: Fluid Therapy NCIT:C116537

Establish individualized daily fluid goals to maintain oxygen delivery and organ function while preventing overload; conditional, low certainty. This is not indiscriminate restriction during shock.

Target Phenotypes: Pulmonary edema HP:0100598

Show evidence (1 reference)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"We suggest that patients with PARDS should receive fluids with the daily fluid goal collaboratively established by the interprofessional team to maintain optimal oxygen delivery and preserve end organ function, while preventing fluid overload."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

Pediatric post-discharge assessment

Action: Clinical Evaluation NCIT:C124351

Screen within three months for pulmonary and broader post-ICU morbidity. Include spirometry when developmentally feasible and refer persistent deficits; infants/toddlers need additional assessment before school. These are good-practice statements.

Show evidence (2 references)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Patients with PARDS should be screened for pulmonary function abnormalities within the first three months after hospital discharge."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"For patients who survive PARDS, health-related quality of life, physical, neurocognitive, emotional, family, and social function should be evaluated within three months of hospital discharge."

Follow-up extends beyond lung function.

Inhaled GM-CSF Host-Directed Therapy

Action: pharmacotherapy Ontology label: Pharmacotherapy NCIT:C15986

Agent: molgramostim NCIT:C77591

Nebulized recombinant human GM-CSF (molgramostim) administered as host-directed therapy to promote alveolar macrophage activation and restoration of barrier function. A phase 2a trial investigated safety, feasibility, and efficacy of low-dose (150 μg) or high-dose (450 μg) administration for 3 days in pneumonia-related ARDS. While the primary composite outcome did not reach significance, high-dose treatment showed beneficial secondary outcomes including upregulation of CD206 on alveolar macrophages (significant against both placebo and low dose; HLA-DR upregulation was significant only against low dose), improved oxygenation, and decreased SOFA scores without increasing alveolar or systemic inflammation.

Mechanism Target:

MODULATES Alveolar Macrophage Activation — GM-CSF promotes differentiation of recruited monocyte-derived macrophages toward homeostatic tissue-resident alveolar macrophages (marked by CD206 upregulation), which participate in inflammation resolution and tissue repair rather than amplifying inflammatory injury.

Show evidence (1 reference)

PMID:42769414 SUPPORT Human Clinical

"high-dose treatment caused upregulation of HLA-DR and CD206 on alveolar macrophages, indicating deposition in the alveolar compartment and beneficial macrophage activation (HLA-DR: p=0.0406 versus low dose, p=0.1841 versus placebo; CD206: p=0.009 versus low dose, p=0.0179 versus placebo)"

The trial directly measured HLA-DR and CD206 upregulation on alveolar macrophages as biomarkers of beneficial macrophage activation.

Target Phenotypes: Respiratory failure HP:0002878 Hypoxemia HP:0012418

Show evidence (3 references)

PMID:42769414 SUPPORT Human Clinical

"high-dose rhGM-CSF treatment revealed a favourable profile of oxygenation at the end of analysis compared to time-points before inhalation (p=0.095 and p=0.0175) or compared to the low-dose and placebo groups (p=0.0063 and p=0.0198; visit 13), and was associated with decreased SOFA scores in the..."

The phase 2a trial supports improved oxygenation and SOFA-score trends with high-dose GM-CSF; the composite primary outcome did not reach significance, so the findings remain secondary-outcome and exploratory.

PMID:42769414 SUPPORT Human Clinical

"Importantly, inhaled rhGM-CSF did not increase alveolar or systemic inflammation."

Safety assessment confirms no increase in inflammatory markers, supporting feasibility of this host-directed approach without triggering adverse inflammation amplification.

PMID:42769414 REFUTE Human Clinical

"however, it did not lead to differences in the GI-HOPE score."

The trial's prespecified primary endpoint, the composite GI-HOPE score, did not differ between arms, so clinical efficacy in ARDS is not established.

🌍

Environmental Factors

Inhalation of chlorine gas

Hazard type: CHEMICAL

Route: INHALATION

Duration: ACUTE

Bound to ECTO:9000077 (exposure to chlorine), confirmed against the ontology service. This entry was originally scoped to "irritant halogen gases" and bound to the substance-level ECTO:0000231 while the service was unreachable; it is now narrowed to chlorine so the binding, the name and the quoted evidence all describe the same agent. Bromine is curated as a separate entry because ECTO has no bromine exposure class, and binding the chlorine term to an entry that also asserted bromine would have manufactured a narrower match than the claim.

Chlorine is among the commonest chemical causes of acute lung injury, encountered through transport accidents, industrial spills, water treatment and swimming-pool exposures, and deliberate release. Inhaled chlorine reacts in the airway to form oxidative products, so the insult delivered to the alveolar-capillary interface is chemical and oxidative rather than infectious or mechanical.

Show evidence (2 references)

PMID:20601629 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"More severely affected individuals may suffer acute lung injury (ALI) and/or acute respiratory distress syndrome (ARDS)."

Human clinical evidence that chlorine exposure reaches ARDS at the severe end of its dose-response, rather than causing airway irritation alone.

PMID:20601629 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Humans can come into contact with chlorine gas during short-term, high-level exposures due to traffic or rail accidents, spills, or other disasters."

Documents the exposure scenarios, which is what makes this an environmental entry rather than a purely clinical trigger.

Mechanism Target:

TRIGGERS Direct Pulmonary or Indirect Systemic Insult — Halogen inhalation is a direct pulmonary insult, entering the mechanism at the trigger node alongside pneumonia, aspiration and contusion.

Show evidence (1 reference)

PMID:29722341 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Chlorine is highly toxic by inhalation, leading to dyspnea, hypoxemia, airway obstruction, pneumonitis, pulmonary edema, and acute respiratory distress syndrome (ARDS)."

States the causal path from inhalational chlorine exposure to ARDS, supporting the exposure acting on the trigger node.

Inhalation of bromine gas

Hazard type: CHEMICAL

Route: INHALATION

Duration: ACUTE

Deliberately left without an exposure_term. ECTO was searched via the ontology service and has no bromine exposure class - the nearest hit, ECTO:9002162 (exposure to brominated flame retardant), is a different agent and binding it would misclassify the exposure. Falling back to the generic ECTO:0000231 was also rejected, because that is the binding this PR is narrowing away from. `just environmental-term-audit` will report this entry as UNBOUND and that is the correct outcome, not a gap to close.

Acute bromine inhalation can cause bronchospasm, airway hyperresponsiveness and severe acute lung injury including ARDS. Concentration, duration and species affect toxicity; experimental mouse mechanisms and rescue studies do not establish a human antidote.

Show evidence (1 reference)

PMID:29722341 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Exposure to halogens, such as chlorine or bromine, results in environmental and occupational hazard to the lung and other organs."

Establishes bromine alongside chlorine as an inhalational halogen hazard to the lung.

Mechanism Target:

TRIGGERS Direct Pulmonary or Indirect Systemic Insult — Bromine inhalation is a direct pulmonary insult acting at the trigger node.

Show evidence (1 reference)

PMID:29722341 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Although bromine is less reactive and oxidative than chlorine, inhalation also results in bronchospasm, airway hyperresponsiveness, ARDS, and even death."

States the causal path from bromine inhalation to ARDS, supporting the exposure acting on the trigger node.

Smoke inhalation

Hazard type: CHEMICAL

Route: INHALATION

Duration: ACUTE

Bound to ECTO:7000059 (exposure to smoke), confirmed against the ontology service. This entry was originally bound to ECTO:0000231 (exposure to chemical) while the service was unreachable, which was not merely broad but in the wrong branch: ECTO classifies exposure to smoke under exposure to environmental material, not under exposure to chemical, which matches the fact that fire smoke is a mixture of combustion products rather than a single chemical agent. ECTO:6000029 (exposure to tobacco smoking) remains deliberately unused: it denotes tobacco smoking, a different exposure from inhaling combustion products in a fire, and reusing it would misclassify the exposure while validating cleanly.

Smoke inhalation exposes the respiratory tract to toxic gases and particles that can injure distal lung and impair surfactant. Thermal injury primarily affects the upper airway; it is not treated as the alveolar mechanism. ARDS may coexist with cutaneous burns and other fire-related injuries.

Show evidence (1 reference)

PMID:31068086 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Approximately 22% of all burn patients are diagnosed with SI-ALI, leading to at least 30% of the overall fire-associated mortality."

Quantifies the burden, supporting this as a substantive exposure route rather than a rare case-report association.

Mechanism Target:

TRIGGERS Direct Pulmonary or Indirect Systemic Insult — Smoke inhalation acts as a direct pulmonary insult at the trigger node.

Show evidence (1 reference)

PMID:31068086 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Smoke-inhalation-induced acute lung injury (SI-ALI) is a leading cause of morbidity and mortality in victims of fire tragedies."

Establishes smoke inhalation as a cause of acute lung injury acting at the trigger node.

🔬

Biochemical Markers

Bronchoalveolar lavage L-lactate (INCREASED)

Context: Untargeted LC-MS of convenience BAL samples from 18 ARDS patients and eight healthy controls found higher L-lactate; the RPLC estimate was 4.35-fold. Sampling was early and cross-sectional, with heterogeneous disease, ventilation and medication exposure. This is an exploratory compartment-specific association, not a diagnostic threshold or proof of intracellular glycolytic flux.

Show evidence (1 reference)

PMID:24289193 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Despite the certain technical limitations of our analytical approach, we identified potential differentiating metabolites of ARDS as evidenced by the over four-fold increase in L-lactate and changes in other metabolites associated with energy metabolism (e.g., citrate, creatine, creatinine).32..."

The primary study measures higher BAL lactate, without validating an ARDS-specific clinical assay.

🔬

Diagnosis

Adult global consensus clinical diagnosis

Diagnose ARDS when acute or worsening hypoxemic respiratory failure occurs within one week of a predisposing insult or new respiratory symptoms, with bilateral loss of lung aeration on radiography, CT, or qualified ultrasound, and edema not primarily explained by cardiac failure, fluid overload, collapse, effusion, or embolism. Hypoxemia can be identified by PaO2:FiO2 at or below 300 mm Hg or by SpO2:FiO2 at or below 315 when SpO2 is at or below 97%; the global definition includes specified nonintubated and resource-limited pathways. Nonintubated criteria require HFNO at least 30 L/min or NIV/CPAP with at least 5 cm H2O end-expiratory pressure. Intubated criteria require PEEP at least 5 cm H2O. A separate resource-limited category does not require a specific oxygen-delivery device, flow or PEEP. Cardiogenic edema and chronic lung disease can coexist when they do not primarily explain the acute hypoxemia.

clinical assessment NCIT:C124351

Results: Acute bilateral noncardiogenic inflammatory lung injury with qualifying hypoxemia supports the diagnosis; severity and respiratory-support category should be recorded separately.

Show evidence (3 references)

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The committee agreed that the current time frame for the diagnosis of ARDS should be retained: acute onset or worsening of hypoxemic respiratory failure is defined as occurring within 1 week of the onset of the predisposing risk factor or within 1 week of new or worsening respiratory symptoms."

This establishes the acute diagnostic time window.

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The committee made four main recommendations: 1) include high-flow nasal oxygen with a minimum flow rate of ⩾30 L/min; 2) use PaO2:FiO2 ⩽ 300 mm Hg or oxygen saturation as measured by pulse oximetry SpO2:FiO2 ⩽ 315 (if oxygen saturation as measured by pulse oximetry is ⩽97%) to identify..."

The global definition supplies the oxygenation, imaging, and respiratory-support criteria represented in the diagnostic description.

PMID:37487152 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The committee agreed on a threshold of oxygen delivery of 30 L/min with HFNO because 30 L/min can provide low levels of PEEP (56)."

The global definition specifies the nonintubated support threshold.

PALICC-2 pediatric scope and timing

Use for children younger than 18 without active perinatal lung disease, within seven days of a known insult. New unilateral or bilateral parenchymal opacity is sufficient; edema must not be fully cardiac or fluid-overload related. Definitions are ungraded consensus statements.

Clinical Evaluation NCIT:C124351

Show evidence (3 references)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"All patients less than 18 years old without active perinatal lung disease should be diagnosed with PARDS using PALICC-2 criteria."

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Symptoms of hypoxemia and radiographic changes must occur within 7 days of a known insult to qualify for PARDS."

Timing criterion.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Chest imaging findings of new opacity (or opacities) consistent with acute pulmonary parenchymal disease not explained by atelectasis or effusion are necessary to diagnose PARDS."

Bilateral opacities are not mandatory.

Confirmed PARDS oxygenation criteria

IMV: OI ≥4 or OSI ≥5. Full-face NIV with CPAP/PEEP ≥5 cm H2O: PaO2/FiO2 ≤300 or SpO2/FiO2 ≤250. Assess steady state; use PaO2 preferentially and SpO2 at ≤97% when saturation-based criteria are applied.

Clinical Evaluation NCIT:C124351

Show evidence (3 references)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"IMV: OI ≥ 4 or OSI ≥ 5"

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"NIV c : Pa o 2 /F io 2 ≤ 300 or Sp o 2 /F io 2 ≤ 250"

Table 4 NIV oxygenation threshold; full-face interface and pressure criteria also apply.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Diagnosis of PARDS on NIV (NIV-PARDS) requires full facemask interface with continuous airway positive pressure/positive end-expiratory pressure ≥ 5 cm H2O."

The confirmed NIV definition requires a full-face interface.

Possible PARDS on nasal support or with unavailable imaging

Nasal CPAP/BiPAP or HFNC ≥1.5 L/kg/min or ≥30 L/min with PaO2/FiO2 ≤300 or SpO2/FiO2 ≤250 and other criteria qualifies as possible PARDS. Missing imaging in resource-limited settings can also support possible PARDS. Pure obstructive airway disease alone does not qualify.

Clinical Evaluation NCIT:C124351

Show evidence (2 references)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Patients on a nasal interface of NIV (CPAP or BiPAP) or on HFNC greater than or equal to 1.5 L/kg/min or greater than or equal to 30 L/min should be considered as having possible PARDS if they meet timing, oxygenation, etiology/risk factor, and imaging criteria"

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Patients who are missing imaging due to resource limitations should be considered as having possible PARDS if they otherwise meet timing, oxygenation, and risk factor criteria."

Resource-limited definition.

PARDS severity after stabilization

Stratify at least four hours after diagnosis. Severe IMV-PARDS: OI ≥16 or OSI ≥12; severe NIV-PARDS: PaO2/FiO2 ≤100 or SpO2/FiO2 ≤150. Chronic IMV and cyanotic congenital heart disease need acute deterioration but should not receive these OI/OSI risk categories.

Clinical Evaluation NCIT:C124351

Show evidence (3 references)

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Subjects with PARDS should be stratified into severity categories after a period of at least 4 hours"

Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Severe: OI ≥ 16 or OSI ≥ 12"

Table 4 invasive severity threshold.

PMID:36661420 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Severe NIV-PARDS: Pa o 2 /F io 2 ≤ 100 or Sp o 2 /F io 2 ≤ 150"

Table 4 noninvasive severity threshold.

📈

Progression

Exudative inflammatory phase

The early injury phase features proinflammatory alveolar-macrophage activation, neutrophil recruitment, epithelial injury, endothelial activation, and permeability edema. Diffuse alveolar damage may occur but is not required for the clinical diagnosis.

Show evidence (1 reference)

PMID:39866839 SUPPORT DIRECT REVIEW SYNTHESIS Other

"During the exudative phase of ARDS, macrophages are activated by pathogens through pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), leucine-rich repeat sequence receptors (NLRs), transmembrane C-type lectin receptors (CLRs), and retinoic acid-induced gene-like..."

The review defines macrophage activation as a central feature of the exudative phase.

Reparative and proliferative phase

If injury control and clearance succeed, pulmonary alveolar type 2 cells proliferate and macrophage programs shift toward inflammation resolution, epithelial regeneration, edema clearance, and structural repair. Pro-resolving macrophages also clear dead cells and debris during recovery; the temporal association with epithelial regeneration is not treated as a demonstrated causal trigger.

Show evidence (2 references)

PMID:39866839 SUPPORT DIRECT REVIEW SYNTHESIS Other

"In the late stage of ARDS, anti-inflammatory cytokines secreted by selectively activated macrophages inhibit the inflammatory response, thereby promoting epithelial regeneration and alveolar structural remodeling."

The review describes the macrophage and epithelial transition toward repair and remodeling.

PMID:30872586 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Once the alveolar epithelium is regenerated, pro-resolving macrophages clear dead cells and debris and ATII and ATI epithelial cells reabsorb oedematous fluid."

Review synthesis describes macrophage debris clearance during resolution.

Persistent fibroproliferative or fibrotic phase

In a subset with nonresolving injury, aberrant remodeling progresses to traction bronchiectasis, reduced lung volume, and fibrotic structural change, prolonging ventilatory and functional impairment.

Show evidence (1 reference)

PMID:39866839 SUPPORT DIRECT REVIEW SYNTHESIS Other

"By the time fibrosis occurs, in addition to traction bronchiectasis, large grid-like and small cystic changes may be observed in the lungs."

The review describes the radiologic structural changes of the fibrotic phase; the entry limits this course to a subset rather than implying that all ARDS becomes fibrotic.

Post-intensive-care recovery

Some survivors have persistent physical and psychological impairment for years despite near-normal pulmonary function. In the five-year follow-up study, the original cohort comprised 109 survivors; survivor selection and incomplete causal attribution to ARDS limit generalization.

Show evidence (1 reference)

PMID:21470008 SUPPORT DIRECT PRIMARY RESULT Human Clinical

The longitudinal survivor study reports persistent limitations rather than a universal course.

Acute mortality risk

In the 2014 LUNG SAFE cohort, hospital mortality was 34.9%, 40.3% and 46.1% in mild, moderate and severe Berlin ARDS respectively. These are cohort-, definition- and era-specific outcomes, not current individual prognoses.

Show evidence (1 reference)

PMID:26903337 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Hospital mortality was 34.9% (95% CI, 31.4%-38.5%) for those with mild, 40.3% (95% CI, 37.4%-43.3%) for those with moderate, and 46.1% (95% CI, 41.9%-50.4%) for those with severe ARDS."

The observational cohort reports severity-associated hospital mortality.

📊

Prevalence

Adult ICU admissions in the LUNG SAFE convenience sample of 459 ICUs in 50 countries during four winter weeks in 2014

Period Prevalence 10400.0 per 100,000 >1 in 1,000

3022 of 29144 admitted patients fulfilled ARDS criteria. This ICU period prevalence is not annual population incidence and may reflect seasonal and participating-center selection.

Show evidence (1 reference)

PMID:26903337 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"RESULTS: Of 29,144 patients admitted to participating ICUs, 3022 (10.4%) fulfilled ARDS criteria."

The prospective multicenter convenience sample provides a denominator-specific estimate.

📊

Related Datasets

Airway Organ Tissue Equivalent (OTE) Platform for Modeling Chlorine Gas Toxicology. geo:GSE261463

RNA sequencing of human airway-chip tissues after controlled chlorine gas exposure and medical-air control conditions. This experimental airway dataset does not contain an ARDS patient cohort.

Homo sapiens BULK RNA SEQ

Conditions: 20 ppm chlorine for 30 minutes Medical air control

PMID:41442163

The GEO accession was independently resolved with the sanctioned dataset verifier. Chip replicates and sampled timepoints are not independent patients.

Show evidence (1 reference)

PMID:41442163 SUPPORT DIRECT PRIMARY RESULT In Vitro

"The transcriptomic datasets generated during this study are available in NCBI’s Gene Expression Omnibus (GEO) and are accessible through GEO Series Accession Number GSE261463."

The source deposits its airway-chip transcriptome in GEO.

🔬

Clinical Trials

clinicaltrials:NCT00527813 NOT_APPLICABLE COMPLETED

PROSEVA randomized 466 adults with severe ARDS to prolonged prone sessions or supine care with protective ventilation. The trial reported lower 28-day and 90-day mortality in the prone group; its protocol and eligibility are distinct from pediatric guidance.

Show evidence (2 references)

PMID:23688302 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"In this multicenter, prospective, randomized, controlled trial, we randomly assigned 466 patients with severe ARDS to undergo prone-positioning sessions of at least 16 hours or to be left in the supine position."

The primary trial specifies the adult intervention, comparator and study population.

PMID:23688302 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"The 28-day mortality was 16.0% in the prone group and 32.8% in the supine group (P<0.001)."

The primary publication reports the trial outcome, rather than relying on the registry protocol for efficacy.

clinicaltrials:NCT00281268 PHASE_III COMPLETED

FACTT compared conservative and liberal fluid strategies for seven days in 1000 patients with acute lung injury. Ventilator-free days and lung physiology improved with conservative management, without a statistically significant 60-day mortality difference.

Show evidence (2 references)

PMID:16714767 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"In a randomized study, we compared a conservative and a liberal strategy of fluid management using explicit protocols applied for seven days in 1000 patients with acute lung injury."

The primary trial defines the randomized comparison.

PMID:16714767 SUPPORT DIRECT PRIMARY RESULT Human Clinical

Efficacy is tied to the published endpoints.

clinicaltrials:NCT02595060 PHASE_II COMPLETED

GI-HOPE, a randomised, double-blind, placebo-controlled phase 2a trial of inhaled molgramostim (150 or 450 micrograms daily for 3 days) in pneumonia-related ARDS. Published results report safety and favourable secondary outcomes at high dose, with no difference in the composite primary GI-HOPE score.

Target Phenotypes: Respiratory failure HP:0002878

Show evidence (1 reference)

clinicaltrials:NCT02595060 SUPPORT Human Clinical

"This trial evaluates efficacy and safety of inhaled molgramostim (rhGM-CSF) in 45 patients with pneumonia associated acute respiratory distress syndrome (ARDS)."

The registration record establishes the trial's population and intervention for ARDS.

🧫

Experimental Models

Human airway-on-a-chip chlorine gas exposure model ORGAN_ON_CHIP namo:OrganOnChip

Human bronchial airway-on-chip with mucociliary epithelium, stromal extracellular matrix and a microvascular endothelial compartment, exposed to controlled chlorine gas. Integrated TEER, imaging and omics characterize chemical injury. This is an airway model, not an alveolar ARDS model or a clinical exposure-threshold study.

Organism

human NCBITaxon:9606

Tissue

epithelium of bronchus UBERON:0002031

Culture

Microfluidic airway-on-a-chip at air-liquid interface with integrated TEER electrodes and controlled gas exposure

Publication

PMID:41442163

Pathograph links

Direct Pulmonary or Indirect Systemic Insult recapitulates fidelity: moderate Dose and duration jointly determine the measured barrier response. TEER recovered by 24 hours after 10 ppm for 10 minutes, whereas 30 ppm exposures caused nearly complete TEER reduction sustained through 24 hours. These data do not establish irreversible injury or recovery after every 10 ppm exposure.

Limitations: Chlorine is one specific inhalational insult and the chip is bronchial rather than alveolar, so it models the direct pulmonary insult category only for inhaled oxidant gases and not for aspiration, pneumonia, or the indirect systemic insults that cause most ARDS. Each dataset used a single donor set with independently fabricated chip replicates; these are not independent patient replicates.

Readouts

Transepithelial electrical resistance across chlorine dose and duration

Direction: DECREASED

Interpretation: TEER quantifies dose- and duration-dependent barrier function within the observed recovery period; it is not a proven irreversible-injury threshold.

Show evidence (2 references)

PMID:41442163 SUPPORT DIRECT PRIMARY RESULT In Vitro

"The lowest dose (10 ppm, 10 min) showed maximal TEER reduction at 6 h with complete recovery by 24 h (Fig. 3D)."

The lowest dose-duration condition recovered within 24 hours.

+ 1 more reference

Show evidence (1 reference)

PMID:41442163 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Epithelial barrier disruption, characterized by gap formation, was evident immediately post-Cl2 exposure and persisted through 24 h"

Supports the chip as a model of a direct pulmonary chemical insult producing sustained injury.

Alveolar-Capillary Barrier Disruption partially recapitulates fidelity: moderate Immediate epithelial gaps and endothelial junction disruption detected at 72 hours are consistent with secondary endothelial injury. The timing does not establish the intervening signal or exclude an independent delayed chemical effect.

Limitations: The chip has no neutrophils or macrophages, so the inflammatory amplification and resolution phases that dominate barrier disruption in clinical ARDS are represented only indirectly through early epithelial-endothelial signalling. It is also airway rather than alveolar epithelium. Each dataset used a single donor set with independently fabricated chip replicates; these are not independent patient replicates.

Readouts

Endothelial VE-cadherin junction integrity at 72 hours post-exposure

Direction: DECREASED

Interpretation: Delayed loss of endothelial junctional integrity is an observed readout; epithelial-to-endothelial mediation remains inferred.

Show evidence (1 reference)

PMID:41442163 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Endothelial barrier integrity, assessed at 0-, 24-, 48-, and 72-h post-exposure, showed significant disruption only at 72 h in Cl2-exposed airway-chips (0- and 72-h shown in Fig. 3H)."

The actual time-course observation supports a delayed endothelial effect.

Show evidence (1 reference)

PMID:41442163 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"A primary constraint is the absence of innate immune system components, limiting evaluation of inflammatory responses to early epithelial/endothelial signaling that would typically recruit neutrophils and macrophages."

The absence of innate immune cells limits the chip to early structural-cell signaling and barrier responses.

Organoid-derived Pseudomonas pneumonia-on-a-chip (VAP) model ORGAN_ON_CHIP namo:OrganOnChip

Organoid-derived alveolar epithelial cells with AT2 and AT1-like differentiation and primary pulmonary microvascular endothelium are cultured on an alveolus chip and infected with Pseudomonas aeruginosa. Cyclic strain of 5% versus 10% at 0.25 Hz tests a controlled mechanical perturbation. Chip strain is not a uniquely equivalent clinical tidal-volume dose.

Organism

human NCBITaxon:9606

Tissue

alveolus of lung UBERON:0002299

Cell source

Human alveolar organoid-derived epithelial cells and primary pulmonary microvascular endothelial cells

Culture

Alveolus-on-a-chip with air-liquid interface, vascular flow, and controlled cyclic strain

Publication

PMID:41252215

Pathograph links

Ventilator-Induced Lung Injury partially recapitulates fidelity: moderate Increasing chip strain raised baseline apparent permeability slightly and, after infection, increased vascular bacterial counts and permeability. This demonstrates a mechanical-infectious interaction in this cell system without establishing the size of a clinical ventilation effect.

Limitations: The uniform chip deformation does not reproduce regional overdistension and recruitment-derecruitment in an injured lung. There are no seeded immune cells. Infection outcomes were assessed at 12 hours; baseline permeability was measured before infection. The organoid system is not a clinical ARDS cohort.

Readouts

Apparent permeability under hyperphysiological versus physiological strain

Direction: INCREASED

Interpretation: Strain-dependent permeability increase is the barrier readout for stretch injury.

Show evidence (1 reference)

PMID:41252215 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Yet, Papp was slightly increased in 10% stretched ODAECs, suggesting barrier impairment by hyperphysiological stretch."

The source describes the baseline permeability increase as slight.

Bacterial translocation to the vascular channel under increased strain

Direction: INCREASED

Interpretation: Higher vascular-channel colony counts under greater strain quantify the strain-infection interaction.

Show evidence (1 reference)

PMID:41252215 SUPPORT DIRECT PRIMARY RESULT In Vitro

"CFUs in the vascular channel and Papp were higher in 10% compared with 5% stretched ODAEC chips (Figure 1, H and I, and Supplemental Figure 4, A and B), indicating that mechanical strain exacerbates Pseudomonas infection in the alveolus."

Vascular bacterial counts and permeability increased under greater stretch; this does not establish increased apical bacterial growth.

Show evidence (1 reference)

PMID:41252215 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"We hereby present what we believe to be the first functional Pseudomonas POC and VAP-on-a-chip model that replicates key features of disease, including enhanced mechanical strain."

Supports the chip as a model of ventilator-associated infectious lung injury, the clinical setting this node describes.

Alveolar-Capillary Barrier Disruption partially recapitulates fidelity: moderate Infection plus greater chip strain increased apparent permeability and vascular-channel bacterial counts. These readouts model aspects of barrier dysfunction without reproducing the full syndrome.

Limitations: Barrier failure is measured as apparent permeability and bacterial translocation over 12 hours, without the protein-rich alveolar flooding, coagulation, or leukocyte transmigration that accompany the lesion clinically.

Readouts

Barrier disruption with bacterial translocation

Direction: INCREASED

Interpretation: Higher vascular-channel bacterial counts are consistent with increased translocation across the experimental barrier.

Show evidence (1 reference)

PMID:41252215 SUPPORT DIRECT PRIMARY RESULT In Vitro

Vascular bacterial counts and permeability increased under greater stretch; this does not establish increased apical bacterial growth.

Show evidence (1 reference)

PMID:41252215 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"We hereby present what we believe to be the first functional Pseudomonas POC and VAP-on-a-chip model that replicates key features of disease, including enhanced mechanical strain."

Supports the chip as informative for the alveolar-capillary barrier lesion under combined infectious and mechanical insult.

Pulmonary Cytokine and Chemokine Release perturbs fidelity: moderate Increasing cyclic strain from 5% to 10% modulates IL-6 and IL-8 release in the infected chip. Cytokine levels decrease under greater strain despite increased barrier injury.

Limitations: This comparison measures cytokine output in an epithelial-endothelial chip without seeded immune cells at 12 hours after infection. It does not establish a clinical anti-inflammatory benefit of greater ventilation strain.

Readouts

IL-6 and IL-8 release under greater strain

Direction: DECREASED

Interpretation: Lower cytokine levels at 10% than at 5% strain prevent interpreting barrier injury as uniformly stronger inflammatory output.

Show evidence (1 reference)

PMID:41252215 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Notably, lower cytokine levels were detected under 10% compared with 5% stretch, suggesting that increased strain modulates immune reactivity."

Greater strain reduced these measured cytokine outputs despite greater barrier injury.

Show evidence (1 reference)

PMID:41252215 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Notably, lower cytokine levels were detected under 10% compared with 5% stretch, suggesting that increased strain modulates immune reactivity."

Greater strain reduced these measured cytokine outputs despite greater barrier injury.

{ }

Source YAML

click to show

name: Acute Respiratory Distress Syndrome
creation_date: '2026-08-08T19:10:07Z'
category: Complex
categories:
- Respiratory Disease
synonyms:
- ARDS
description: Acute respiratory distress syndrome is acute diffuse inflammatory lung injury following a pulmonary or systemic insult. Increased alveolar-capillary permeability, impaired fluid clearance and surfactant dysfunction produce noncardiogenic edema, loss of aerated lung and hypoxemic respiratory failure. The syndrome is heterogeneous and does not require invariant diffuse alveolar damage. Adult global and pediatric PALICC-2 definitions have distinct oxygenation, respiratory-support and imaging criteria.
parents:
- acute respiratory failure
- lung disorder
disease_term:
  preferred_term: Acute respiratory distress syndrome
  term:
    id: MONDO:0006502
    label: acute respiratory distress syndrome
has_subtypes:
- name: Adult ARDS
  display_name: Adult Acute Respiratory Distress Syndrome
  classification: age_group
  subtype_term:
    preferred_term: adult acute respiratory distress syndrome
    term:
      id: MONDO:0100130
      label: adult acute respiratory distress syndrome
  description: ARDS in adults, classified clinically by the severity of acute hypoxemia and recognized in intubated, nonintubated, and resource-limited settings under the 2024 global definition.
  evidence:
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: We propose a new global definition of ARDS that builds on the Berlin definition.
    explanation: The international consensus document defines the current clinical scope used for adult ARDS.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
- name: Pediatric ARDS
  display_name: Pediatric Acute Respiratory Distress Syndrome
  classification: age_group
  subtype_term:
    preferred_term: pediatric acute respiratory distress syndrome
    term:
      id: MONDO:0100131
      label: pediatric acute respiratory distress syndrome
  description: ARDS in patients younger than 18 years without active perinatal lung disease. PALICC-2 uses pediatric oxygenation criteria and permits unilateral or bilateral parenchymal opacities; nasal noninvasive support or HFNC can qualify as possible PARDS rather than confirmed NIV-PARDS.
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: All patients less than 18 years old without active perinatal lung disease should be diagnosed with PARDS using PALICC-2 criteria.
    explanation: PALICC-2 specifies pediatric scope and exclusions.
- name: Hyperinflammatory ARDS subphenotype
  classification: biological_subphenotype
  description: A latent-class-analysis phenotype enriched for inflammatory biomarkers, vasopressor use, metabolic acidosis, fewer ventilator-free days, and higher mortality. This is a research subphenotype rather than part of the clinical ARDS definition or a validated bedside diagnosis.
  review_notes: Derived research classes are not diagnostic criteria or prospectively validated treatment-selection rules. No single clinical variable identifies a class.
  evidence:
  - reference: PMID:24853585
    reference_title: 'Subphenotypes in acute respiratory distress syndrome: latent class analysis of data from two randomised controlled trials.'
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: 'FINDINGS: We analysed data for 1022 patients: 473 in the ARMA cohort and 549 in the ALVEOLI cohort.'
    explanation: Latent-class modeling was applied to 473 lower-tidal-volume ARMA participants and 549 ALVEOLI participants; this is retrospective research stratification.
  - reference: PMID:24853585
    reference_title: 'Subphenotypes in acute respiratory distress syndrome: latent class analysis of data from two randomised controlled trials.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: It is important to emphasize that while the interactions identified between PEEP and clinical outcomes are potentially provocative, we are reticent to make any recommendations for clinical care on the basis of a subgroup analysis.
    explanation: The investigators explicitly treat subgroup treatment findings as hypothesis-generating.
- name: Hypoinflammatory ARDS subphenotype
  classification: biological_subphenotype
  description: A research latent-class group with less systemic inflammation and shock than the hyperinflammatory group. Lower biomarker concentrations do not establish mitochondrial exhaustion, a uniform molecular mechanism, or a bedside treatment indication.
  review_notes: Derived research classes are not diagnostic criteria or prospectively validated treatment-selection rules. No single clinical variable identifies a class.
  evidence:
  - reference: PMID:24853585
    reference_title: 'Subphenotypes in acute respiratory distress syndrome: latent class analysis of data from two randomised controlled trials.'
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: 'FINDINGS: We analysed data for 1022 patients: 473 in the ARMA cohort and 549 in the ALVEOLI cohort.'
    explanation: Latent-class modeling was applied to 473 lower-tidal-volume ARMA participants and 549 ALVEOLI participants; this is retrospective research stratification.
  - reference: PMID:24853585
    reference_title: 'Subphenotypes in acute respiratory distress syndrome: latent class analysis of data from two randomised controlled trials.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: It is important to emphasize that while the interactions identified between PEEP and clinical outcomes are potentially provocative, we are reticent to make any recommendations for clinical care on the basis of a subgroup analysis.
    explanation: The investigators explicitly treat subgroup treatment findings as hypothesis-generating.
mechanistic_hypotheses:
- hypothesis_group_id: alveolar_capillary_injury_model
  hypothesis_label: Alveolar-Capillary Permeability Injury Model
  status: CANONICAL
  description: A direct pulmonary or indirect systemic insult initiates dysregulated innate inflammation and coagulation. Macrophage activation and recruited neutrophils injure the alveolar epithelium and pulmonary endothelium, increasing barrier permeability. Protein-rich edema, loss of aerated lung, and atelectasis then produce shunt physiology, reduced compliance, and hypoxemic respiratory failure.
  evidence:
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: ARDS is an acute, diffuse, inflammatory lung injury precipitated by a risk factor such as pneumonia, nonpulmonary infection, trauma, transfusion, burn, aspiration, or shock. The resulting injury leads to pulmonary edema from an increase in pulmonary vascular and alveolar epithelial permeability.
    explanation: The global consensus definition states the canonical insult-to-barrier-leak framework used by the main causal graph.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
- hypothesis_group_id: immunometabolic_resilience_model
  hypothesis_label: Immunometabolic Persistence and Metabolic Resilience Model
  status: EMERGING
  description: Sustained glycolytic programming, impaired mitochondrial oxidative phosphorylation, redox imbalance, and bioactive metabolite signaling in immune and structural lung cells may amplify inflammation and delay alveolar-capillary repair. The related concept of metabolic resilience proposes that recovery depends partly on restoring coordinated mitochondrial function, substrate use, and redox balance. These mechanisms may help explain clinical heterogeneity, but they are not yet validated as a diagnostic endotype or treatment-selection framework.
  evidence:
  - reference: PMID:42432720
    reference_title: 'Immunometabolic reprogramming and mitochondrial dysfunction in acute respiratory distress syndrome: mechanisms, metabolic resilience, and therapeutic perspectives- a narrative review.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Emerging evidence suggests that immunometabolic reprogramming, characterized by increased glycolysis, impaired mitochondrial oxidative phosphorylation, and altered metabolite signalling, plays a critical role in shaping immune-cell activation, inflammatory persistence, and tissue repair during critical illness.
    explanation: The issue's narrative review directly advances the immunometabolic model, while its wording and study design justify EMERGING rather than CANONICAL status.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
  notes: Much of the pathway-level causality and therapeutic rationale is derived from experimental systems, sepsis extrapolation, or associative human multi-omics. No metabolism-targeted ARDS therapy or bedside metabolic-resilience assay has established prospective clinical utility.
progression:
- phase: Exudative inflammatory phase
  notes: The early injury phase features proinflammatory alveolar-macrophage activation, neutrophil recruitment, epithelial injury, endothelial activation, and permeability edema. Diffuse alveolar damage may occur but is not required for the clinical diagnosis.
  evidence:
  - reference: PMID:39866839
    reference_title: 'Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: During the exudative phase of ARDS, macrophages are activated by pathogens through pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), leucine-rich repeat sequence receptors (NLRs), transmembrane C-type lectin receptors (CLRs), and retinoic acid-induced gene-like receptors (RLRs), which promote the transition of resident AM cells to the predominant proinflammatory phenotype.
    explanation: The review defines macrophage activation as a central feature of the exudative phase.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
- phase: Reparative and proliferative phase
  notes: If injury control and clearance succeed, pulmonary alveolar type 2 cells proliferate and macrophage programs shift toward inflammation resolution, epithelial regeneration, edema clearance, and structural repair. Pro-resolving macrophages also clear dead cells and debris during recovery; the temporal association with epithelial regeneration is not treated as a demonstrated causal trigger.
  evidence:
  - reference: PMID:39866839
    reference_title: 'Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: In the late stage of ARDS, anti-inflammatory cytokines secreted by selectively activated macrophages inhibit the inflammatory response, thereby promoting epithelial regeneration and alveolar structural remodeling.
    explanation: The review describes the macrophage and epithelial transition toward repair and remodeling.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Once the alveolar epithelium is regenerated, pro-resolving macrophages clear dead cells and debris and ATII and ATI epithelial cells reabsorb oedematous fluid.
    explanation: Review synthesis describes macrophage debris clearance during resolution.
- phase: Persistent fibroproliferative or fibrotic phase
  notes: In a subset with nonresolving injury, aberrant remodeling progresses to traction bronchiectasis, reduced lung volume, and fibrotic structural change, prolonging ventilatory and functional impairment.
  evidence:
  - reference: PMID:39866839
    reference_title: 'Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: By the time fibrosis occurs, in addition to traction bronchiectasis, large grid-like and small cystic changes may be observed in the lungs.
    explanation: The review describes the radiologic structural changes of the fibrotic phase; the entry limits this course to a subset rather than implying that all ARDS becomes fibrotic.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
- phase: Post-intensive-care recovery
  notes: Some survivors have persistent physical and psychological impairment for years despite near-normal pulmonary function. In the five-year follow-up study, the original cohort comprised 109 survivors; survivor selection and incomplete causal attribution to ARDS limit generalization.
  evidence:
  - reference: PMID:21470008
    reference_title: Functional disability 5 years after acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: 'CONCLUSIONS: Exercise limitation, physical and psychological sequelae, decreased physical quality of life, and increased costs and use of health care services are important legacies of severe lung injury.'
    explanation: The longitudinal survivor study reports persistent limitations rather than a universal course.
- phase: Acute mortality risk
  notes: In the 2014 LUNG SAFE cohort, hospital mortality was 34.9%, 40.3% and 46.1% in mild, moderate and severe Berlin ARDS respectively. These are cohort-, definition- and era-specific outcomes, not current individual prognoses.
  evidence:
  - reference: PMID:26903337
    reference_title: Epidemiology, Patterns of Care, and Mortality for Patients With Acute Respiratory Distress Syndrome in Intensive Care Units in 50 Countries.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Hospital mortality was 34.9% (95% CI, 31.4%-38.5%) for those with mild, 40.3% (95% CI, 37.4%-43.3%) for those with moderate, and 46.1% (95% CI, 41.9%-50.4%) for those with severe ARDS.
    explanation: The observational cohort reports severity-associated hospital mortality.
pathophysiology:
- name: Direct Pulmonary or Indirect Systemic Insult
  biological_scale: TISSUE
  conforms_to: alveolar_capillary_barrier_failure#Alveolar-Capillary Interface Insult
  description: Pneumonia, aspiration, inhalational injury, or lung contusion can directly injure the lung, whereas sepsis, pancreatitis, major trauma, shock, burns, and transfusion can initiate systemic inflammation and endothelial injury. These heterogeneous triggers converge on acute diffuse lung injury.
  role: trigger
  locations:
  - preferred_term: Alveolus of lung
    term:
      id: UBERON:0002299
      label: alveolus of lung
  evidence:
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: ARDS is an acute, diffuse, inflammatory lung injury precipitated by a risk factor such as pneumonia, nonpulmonary infection, trauma, transfusion, burn, aspiration, or shock.
    explanation: Consensus identifies heterogeneous direct pulmonary and systemic precipitating insults.
  downstream:
  - target: Alveolar Macrophage Activation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Innate sensing connects pulmonary or systemic injury to macrophage activation.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Activation of Toll-like receptors (not shown) on alveolar type II (ATII) cells and resident macrophages induces the secretion of chemokines, which recruit circulating immune cells into the airspaces.
      explanation: Review synthesis links innate sensing on resident macrophages and ATII cells to chemokine secretion and immune recruitment.
  - target: Alveolar-Capillary Barrier Disruption
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Direct injury and systemic inflammatory pathways can increase barrier permeability.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:37487152
      reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: ARDS is an acute, diffuse, inflammatory lung injury precipitated by a risk factor such as pneumonia, nonpulmonary infection, trauma, transfusion, burn, aspiration, or shock.
      explanation: Consensus identifies heterogeneous direct pulmonary and systemic precipitating insults.
- name: Alveolar Macrophage Activation
  biological_scale: CELLULAR
  description: Pattern-recognition signaling activates resident alveolar macrophages after infection or tissue injury. This immune-cell state is distinct from secretion of its downstream mediators.
  role: mediator
  evidence:
  - &id001
    reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Activation of Toll-like receptors (not shown) on alveolar type II (ATII) cells and resident macrophages induces the secretion of chemokines, which recruit circulating immune cells into the airspaces.
    explanation: Review synthesis links innate sensing on resident macrophages and ATII cells to chemokine secretion and immune recruitment.
  cell_types:
  - preferred_term: alveolar macrophage
    term:
      id: CL:0000583
      label: alveolar macrophage
  downstream:
  - target: Pulmonary Cytokine and Chemokine Release
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Activated macrophages release inflammatory mediators.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Activation of Toll-like receptors (not shown) on alveolar type II (ATII) cells and resident macrophages induces the secretion of chemokines, which recruit circulating immune cells into the airspaces.
      explanation: Review synthesis links innate sensing on resident macrophages and ATII cells to chemokine secretion and immune recruitment.
  - target: Increased Glycolytic Programming
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Inflammatory macrophage activation can induce glycolytic reprogramming in experimental immunometabolic models; its magnitude and clinical relevance vary by context.
    hypothesis_groups:
    - immunometabolic_resilience_model
    evidence:
    - reference: PMID:42432720
      reference_title: 'Immunometabolic reprogramming and mitochondrial dysfunction in acute respiratory distress syndrome: mechanisms, metabolic resilience, and therapeutic perspectives- a narrative review.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: When macrophages encounter inflammatory stimuli, they shift from mitochondrial oxidative phosphorylation to aerobic glycolysis, a phenomenon called as the “Warburg effect.” This metabolic transition enables rapid ATP generation and provides biosynthetic intermediates required for cytokine production and effector functions.
      explanation: A narrative review summarizes experimental immunometabolic mechanisms; this does not measure glycolytic flux in a representative ARDS cohort.
  biological_processes:
  - preferred_term: macrophage activation
    term:
      id: GO:0042116
      label: macrophage activation
    modifier: INCREASED
- name: Pulmonary Cytokine and Chemokine Release
  biological_scale: MOLECULAR
  description: Activated macrophages and structural lung cells release inflammatory mediators and chemoattractants, including IL-8/CXCL8, that recruit circulating leukocytes.
  role: mediator
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Intra-alveolar macrophages play an important part in releasing chemotactic factors such as IL-8 and chemokines such as CC-chemokine ligand 2 (also known as MCP1) that enhance the recruitment of neutrophils and monocytes into the lung, particularly in response to acute pulmonary infections.
    explanation: The review identifies macrophage chemotactic-factor secretion and its role in leukocyte recruitment.
  downstream:
  - target: Neutrophil Recruitment
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Chemotactic signals promote recruitment into lung airspaces.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Activation of Toll-like receptors (not shown) on alveolar type II (ATII) cells and resident macrophages induces the secretion of chemokines, which recruit circulating immune cells into the airspaces.
      explanation: Review synthesis links innate sensing on resident macrophages and ATII cells to chemokine secretion and immune recruitment.
  biological_processes:
  - preferred_term: cytokine production
    term:
      id: GO:0001816
      label: cytokine production
    modifier: INCREASED
- name: Neutrophil Recruitment
  biological_scale: CELLULAR
  description: Circulating neutrophils enter the pulmonary interstitium and airspaces in response to chemotactic signals. Recruitment is separated from subsequent effector release.
  role: mediator
  evidence:
  - *id001
  - &id002
    reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: As neutrophils migrate across the epithelium, they release toxic mediators, including proteases, reactive oxygen species (ROS) and neutrophil extracellular traps (NETs), which have an important role in host defence but cause endothelial and epithelial injury.
    explanation: Review synthesis separates neutrophil migration from the release of injurious oxidants, proteases and extracellular traps.
  cell_types:
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  biological_processes:
  - preferred_term: neutrophil chemotaxis
    term:
      id: GO:0030593
      label: neutrophil chemotaxis
    modifier: INCREASED
  downstream:
  - target: Neutrophil Oxidant Release
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Recruited neutrophils can release this effector class after activation.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: As neutrophils migrate across the epithelium, they release toxic mediators, including proteases, reactive oxygen species (ROS) and neutrophil extracellular traps (NETs), which have an important role in host defence but cause endothelial and epithelial injury.
      explanation: Review synthesis separates neutrophil migration from the release of injurious oxidants, proteases and extracellular traps.
  - target: Neutrophil Protease Release
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Recruited neutrophils can release this effector class after activation.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: As neutrophils migrate across the epithelium, they release toxic mediators, including proteases, reactive oxygen species (ROS) and neutrophil extracellular traps (NETs), which have an important role in host defence but cause endothelial and epithelial injury.
      explanation: Review synthesis separates neutrophil migration from the release of injurious oxidants, proteases and extracellular traps.
- name: Neutrophil Oxidant Release
  biological_scale: MOLECULAR
  description: Recruited neutrophils release reactive oxygen species. Excessive oxidant activity can injure endothelial and epithelial barrier cells while also serving antimicrobial functions.
  role: mediator
  evidence:
  - *id002
  cell_types:
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  biological_processes:
  - preferred_term: reactive oxygen species metabolic process
    term:
      id: GO:0072593
      label: reactive oxygen species metabolic process
    modifier: INCREASED
  downstream:
  - target: Alveolar-Capillary Barrier Disruption
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Excess effector activity contributes to barrier-cell injury through multiple substrates and pathways.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: As neutrophils migrate across the epithelium, they release toxic mediators, including proteases, reactive oxygen species (ROS) and neutrophil extracellular traps (NETs), which have an important role in host defence but cause endothelial and epithelial injury.
      explanation: Review synthesis separates neutrophil migration from the release of injurious oxidants, proteases and extracellular traps.
- name: Neutrophil Protease Release
  biological_scale: MOLECULAR
  description: Neutrophils release proteolytic effectors during host defense; excessive extracellular activity can contribute to tissue and barrier injury.
  role: mediator
  evidence:
  - *id002
  cell_types:
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  downstream:
  - target: Alveolar-Capillary Barrier Disruption
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Excess effector activity contributes to barrier-cell injury through multiple substrates and pathways.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: As neutrophils migrate across the epithelium, they release toxic mediators, including proteases, reactive oxygen species (ROS) and neutrophil extracellular traps (NETs), which have an important role in host defence but cause endothelial and epithelial injury.
      explanation: Review synthesis separates neutrophil migration from the release of injurious oxidants, proteases and extracellular traps.
- name: Alveolar-Capillary Barrier Disruption
  biological_scale: TISSUE
  description: Increased endothelial and epithelial permeability permits protein-rich fluid to cross into the interstitium and alveoli. Functional junctional changes can occur without endothelial cell death or dramatic endothelial morphological damage. Reduced epithelial fluid transport is represented separately.
  role: mediator
  evidence:
  - &id005
    reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Increased alveolar–capillary permeability to fluid, proteins, neutrophils and red blood cells (resulting in their accumulation into the alveolar space) is the hallmark of ARDS36–38.
    explanation: Permeability to fluid and protein is the defining functional barrier abnormality.
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Thus, in animal models and human ARDS, changes in paracellular permeability to protein seem to occur in the absence of dramatic alterations in the morphology of the lung endothelium.
    explanation: The review cautions that functional permeability changes need not entail dramatic endothelial morphological injury.
  conforms_to: alveolar_capillary_barrier_failure#Alveolar Epithelial and Endothelial Junctional Disruption
  cell_types:
  - &id003
    preferred_term: Pulmonary alveolar type 1 cell
    term:
      id: CL:0002062
      label: pulmonary alveolar type 1 cell
  - &id004
    preferred_term: Pulmonary alveolar type 2 cell
    term:
      id: CL:0002063
      label: pulmonary alveolar type 2 cell
  - preferred_term: Pulmonary capillary endothelial cell
    term:
      id: CL:4028001
      label: pulmonary capillary endothelial cell
  downstream:
  - target: Protein-Rich Alveolar Edema
    causal_link_type: DIRECT
    description: Increased permeability permits fluid and protein entry into airspaces.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: DIRECT
      snippet: Increased alveolar–capillary permeability to fluid, proteins, neutrophils and red blood cells (resulting in their accumulation into the alveolar space) is the hallmark of ARDS36–38.
      explanation: Permeability to fluid and protein is the defining functional barrier abnormality.
  - target: Pulmonary Procoagulant Activation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Epithelial injury may contribute to local procoagulant-factor release.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Injured but intact alveolar epithelial cells seem to drive release of pro-coagulant factors and intra-alveolar fibrin deposition49,50, which is also deposited adjacent to endothelial cells in injured alveoli37,40,47.
      explanation: The review proposes epithelial procoagulant activity as a contributor to alveolar fibrin deposition.
  - target: Alveolar Type 2 Cell Proliferation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Surviving ATII cells can mount a regenerative response to epithelial injury.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: To repair the damaged epithelium, surviving alveolar type II (ATII) cells replace lost epithelial cells via proliferation and differentiation into alveolar type I (ATI) cells.
      explanation: Proliferation and subsequent differentiation are distinct epithelial repair processes; detailed lineage evidence is largely experimental.
  - target: Excess Pulmonary Collagen Deposition
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Dysregulated repair can include excessive fibroblast collagen deposition, but this is not inevitable.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Fibroblasts secrete epithelial growth factors and deposit collagen, which, if excessive, can lead to fibrosis.
      explanation: Fibroblast collagen deposition can become excessive and contribute to fibrosis.
- name: Impaired Alveolar Fluid Clearance
  biological_scale: TISSUE
  description: Reduced epithelial sodium-channel and Na+/K+-ATPase function limits active removal of alveolar fluid. Both type I and type II alveolar epithelial cells contribute to transport.
  role: mediator
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Influenza infection, hypoxaemia, hypercapnia and other factors downregulate sodium channel and/or Na+/K+-ATPase function, resulting in impaired alveolar fluid clearance in patients with ARDS35,75,87,88.
    explanation: Impaired epithelial sodium transport reduces alveolar fluid clearance; this is distinct from increased fluid entry.
  cell_types:
  - *id003
  - *id004
  downstream:
  - target: Protein-Rich Alveolar Edema
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Reduced epithelial transport contributes to persistence of alveolar fluid.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Influenza infection, hypoxaemia, hypercapnia and other factors downregulate sodium channel and/or Na+/K+-ATPase function, resulting in impaired alveolar fluid clearance in patients with ARDS35,75,87,88.
      explanation: Impaired epithelial sodium transport reduces alveolar fluid clearance; this is distinct from increased fluid entry.
  biological_processes:
  - preferred_term: sodium ion transport
    term:
      id: GO:0006814
      label: sodium ion transport
    modifier: DECREASED
- name: Protein-Rich Alveolar Edema
  biological_scale: TISSUE
  description: Permeability-mediated fluid entry and insufficient clearance cause protein-rich alveolar flooding. Hydrostatic loading can coexist, but does not primarily explain the syndrome.
  role: mediator
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: In ARDS, there is increased permeability to liquid and protein across the lung endothelium, which then leads to oedema in the lung interstitium.
    explanation: Increased endothelial permeability produces interstitial edema, with alveolar accumulation when the epithelial barrier also fails.
  - *id005
  conforms_to: alveolar_capillary_barrier_failure#Protein-Rich Alveolar Flooding and Gas-Exchange Failure
  downstream:
  - target: Surfactant Dysfunction
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: The protein-rich injury environment can impair surfactant activity.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: In addition, the many biological changes resulting from both endothelial and epithelial injury, and culminating in protein-rich oedematous fluid, contribute to surfactant dysfunction90.
      explanation: Protein-rich edema and injury can impair surfactant function.
  - target: Intrapulmonary Shunting
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Perfusion of fluid-filled poorly ventilated units contributes to shunting.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Arterial hypoxaemia in patients with ARDS is caused by ventilation-to-perfusion mismatch as well as right-to-left intrapulmonary shunting.
      explanation: The review identifies intrapulmonary shunting and ventilation-perfusion mismatch as causes of hypoxemia.
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: In ARDS, there is increased permeability to liquid and protein across the lung endothelium, which then leads to oedema in the lung interstitium.
      explanation: Increased endothelial permeability produces interstitial edema, with alveolar accumulation when the epithelial barrier also fails.
  - target: Increased Pulmonary Dead Space
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Edema and vascular injury contribute to impaired CO2 elimination.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: The vascular injury and alveolar oedema contribute to the decreased ability to excrete CO2 (hypercapnia), accounting for the elevated pulmonary dead space in acute respiratory distress syndrome.
      explanation: Review synthesis connects pulmonary vascular injury and edema with impaired CO2 elimination.
  - target: Noncardiogenic pulmonary edema
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: This process contributes to the clinical manifestation.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: In ARDS, there is increased permeability to liquid and protein across the lung endothelium, which then leads to oedema in the lung interstitium.
      explanation: Increased endothelial permeability produces interstitial edema, with alveolar accumulation when the epithelial barrier also fails.
  - target: Bilateral pulmonary opacities
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: This process contributes to the clinical manifestation.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:37487152
      reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: ARDS is an acute, diffuse, inflammatory lung injury precipitated by a risk factor such as pneumonia, nonpulmonary infection, trauma, transfusion, burn, aspiration, or shock.
      explanation: Consensus identifies heterogeneous direct pulmonary and systemic precipitating insults.
- name: Surfactant Dysfunction
  biological_scale: TISSUE
  description: Alveolar epithelial injury and the protein-rich edema environment impair the surface-tension-lowering function of surfactant.
  role: mediator
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: In addition, the many biological changes resulting from both endothelial and epithelial injury, and culminating in protein-rich oedematous fluid, contribute to surfactant dysfunction90.
    explanation: Protein-rich edema and injury can impair surfactant function.
  downstream:
  - target: Alveolar Collapse
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Loss of surface-tension control favors alveolar collapse.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Surfactant dysfunction can then increase atelectasis, which in turn can increase the risk of biophysical injury.
      explanation: The review links surfactant dysfunction to alveolar collapse and secondary mechanical injury.
- name: Alveolar Collapse
  biological_scale: TISSUE
  description: Surfactant dysfunction and the gravitational effects of an edematous lung promote regional alveolar collapse, reducing aerated lung volume.
  role: mediator
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Surfactant dysfunction can then increase atelectasis, which in turn can increase the risk of biophysical injury.
    explanation: The review links surfactant dysfunction to alveolar collapse and secondary mechanical injury.
  - reference: PMID:37326646
    reference_title: 'ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: In patients with ARDS, surfactant dysfunction, effects of gravity on the edematous lung, and heterogeneous injury predispose to regional lung derecruitment with alveolar collapse and small airways closure [103].
    explanation: Guideline synthesis identifies surfactant dysfunction and gravitational loading as contributors to derecruitment.
  downstream:
  - target: Intrapulmonary Shunting
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Perfused collapsed lung units contribute to venous admixture.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Arterial hypoxaemia in patients with ARDS is caused by ventilation-to-perfusion mismatch as well as right-to-left intrapulmonary shunting.
      explanation: The review identifies intrapulmonary shunting and ventilation-perfusion mismatch as causes of hypoxemia.
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Surfactant dysfunction can then increase atelectasis, which in turn can increase the risk of biophysical injury.
      explanation: The review links surfactant dysfunction to alveolar collapse and secondary mechanical injury.
  - target: Ventilator-Induced Lung Injury
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Mechanical heterogeneity and cyclic recruitment can increase local strain.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Surfactant dysfunction can then increase atelectasis, which in turn can increase the risk of biophysical injury.
      explanation: The review links surfactant dysfunction to alveolar collapse and secondary mechanical injury.
  - target: Atelectasis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: The process contributes to this clinical manifestation.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Surfactant dysfunction can then increase atelectasis, which in turn can increase the risk of biophysical injury.
      explanation: The review identifies regional collapse as a consequence of surfactant dysfunction.
- name: Intrapulmonary Shunting
  biological_scale: ORGANISM
  description: Blood flow through poorly ventilated or nonventilated lung units impairs oxygenation. Shunting is a physiological process, distinct from its clinical hypoxemia and respiratory-failure outcomes.
  role: mediator
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Arterial hypoxaemia in patients with ARDS is caused by ventilation-to-perfusion mismatch as well as right-to-left intrapulmonary shunting.
    explanation: The review identifies intrapulmonary shunting and ventilation-perfusion mismatch as causes of hypoxemia.
  downstream:
  - target: Hypoxemia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: This process contributes to the clinical manifestation.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Arterial hypoxaemia in patients with ARDS is caused by ventilation-to-perfusion mismatch as well as right-to-left intrapulmonary shunting.
      explanation: The review identifies intrapulmonary shunting and ventilation-perfusion mismatch as causes of hypoxemia.
  - target: Acute hypoxemic respiratory failure
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: This process contributes to the clinical manifestation.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Arterial hypoxaemia in patients with ARDS is caused by ventilation-to-perfusion mismatch as well as right-to-left intrapulmonary shunting.
      explanation: The review identifies intrapulmonary shunting and ventilation-perfusion mismatch as causes of hypoxemia.
  - target: Dyspnea
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Gas-exchange impairment can contribute to this clinical sign through downstream physiological responses.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Most patients who present with the early phase of acute lung injury complain of feeling short of breath.
      explanation: The clinical review explicitly reports early breathlessness.
  - target: Tachypnea
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Gas-exchange impairment can contribute to this clinical sign through downstream physiological responses.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: On physical examination, they appear to be in moderate or severe respiratory distress with an elevated respiratory rate and tachycardia and they usually are working harder than normal to breathe.
      explanation: The physical-examination description identifies an elevated respiratory rate.
  - target: Cyanosis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Gas-exchange impairment can contribute to this clinical sign through downstream physiological responses.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Hypoxaemia may manifest with evidence of cyanosis in their fingernail beds.
      explanation: The review describes nail-bed cyanosis as a possible manifestation of hypoxemia.
- name: Increased Pulmonary Dead Space
  biological_scale: ORGANISM
  description: Pulmonary vascular injury and edema reduce effective carbon-dioxide elimination, increasing physiological dead space and sometimes causing hypercapnia.
  role: mediator
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: The vascular injury and alveolar oedema contribute to the decreased ability to excrete CO2 (hypercapnia), accounting for the elevated pulmonary dead space in acute respiratory distress syndrome.
    explanation: Review synthesis connects pulmonary vascular injury and edema with impaired CO2 elimination.
  downstream:
  - target: Hypercapnia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: The process contributes to this clinical manifestation.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: The vascular injury and alveolar oedema contribute to the decreased ability to excrete CO2 (hypercapnia), accounting for the elevated pulmonary dead space in acute respiratory distress syndrome.
      explanation: The review links impaired carbon-dioxide excretion to pulmonary dead-space abnormalities.
- name: Pulmonary Procoagulant Activation
  biological_scale: MOLECULAR
  description: Injured alveolar epithelial cells and the local inflammatory environment can favor procoagulant activity. This is distinct from the resulting fibrin deposits.
  role: mediator
  evidence:
  - &id006
    reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Injured but intact alveolar epithelial cells seem to drive release of pro-coagulant factors and intra-alveolar fibrin deposition49,50, which is also deposited adjacent to endothelial cells in injured alveoli37,40,47.
    explanation: The review proposes epithelial procoagulant activity as a contributor to alveolar fibrin deposition.
  downstream:
  - target: Intra-Alveolar Fibrin Deposition
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: The procoagulant environment favors local fibrin deposition.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Injured but intact alveolar epithelial cells seem to drive release of pro-coagulant factors and intra-alveolar fibrin deposition49,50, which is also deposited adjacent to endothelial cells in injured alveoli37,40,47.
      explanation: The review proposes epithelial procoagulant activity as a contributor to alveolar fibrin deposition.
  biological_processes:
  - preferred_term: regulation of coagulation
    term:
      id: GO:0050818
      label: regulation of coagulation
    modifier: DYSREGULATED
- name: Intra-Alveolar Fibrin Deposition
  biological_scale: TISSUE
  description: Fibrin accumulates within injured alveoli and near the pulmonary endothelium. It is a component of the injury pattern rather than proof that fibrosis must follow.
  role: mediator
  evidence:
  - *id006
  biological_processes:
  - preferred_term: blood coagulation, fibrin clot formation
    term:
      id: GO:0072378
      label: blood coagulation, fibrin clot formation
    modifier: INCREASED
- name: Ventilator-Induced Lung Injury
  biological_scale: TISSUE
  description: Excessive tidal deformation, overdistension and repeated opening and closure can amplify epithelial and endothelial injury in the reduced aerated lung. Exposure depends on ventilator settings, lung mechanics and patient effort.
  role: modifier
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: High tidal volume and elevated airway pressure induce biomechanical inflammatory injury and necrosis of the lung endothelium and alveolar epithelium that are associated with release of neutrophil products, including proteases, oxidants and pro-inflammatory cytokines, and a reduction in the capacity of the alveolar epithelium to remove oedematous fluid36,95,96.
    explanation: Mechanical ventilation can add biomechanical injury to the endothelial and epithelial barriers.
  conforms_to: alveolar_capillary_barrier_failure#Cyclic Mechanical Strain Amplification
  downstream:
  - target: Alveolar-Capillary Barrier Disruption
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Excess mechanical stress amplifies endothelial and epithelial injury.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: High tidal volume and elevated airway pressure induce biomechanical inflammatory injury and necrosis of the lung endothelium and alveolar epithelium that are associated with release of neutrophil products, including proteases, oxidants and pro-inflammatory cytokines, and a reduction in the capacity of the alveolar epithelium to remove oedematous fluid36,95,96.
      explanation: Mechanical ventilation can add biomechanical injury to the endothelial and epithelial barriers.
- name: Increased Glycolytic Programming
  biological_scale: CELLULAR
  description: Inflammatory activation can shift cellular metabolism toward glycolysis. Its magnitude and persistence vary by cell type and compartment; a uniform glycolysis-dominant state is not established in every patient with ARDS.
  role: modifier
  evidence:
  - reference: PMID:42432720
    reference_title: 'Immunometabolic reprogramming and mitochondrial dysfunction in acute respiratory distress syndrome: mechanisms, metabolic resilience, and therapeutic perspectives- a narrative review.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: When macrophages encounter inflammatory stimuli, they shift from mitochondrial oxidative phosphorylation to aerobic glycolysis, a phenomenon called as the “Warburg effect.” This metabolic transition enables rapid ATP generation and provides biosynthetic intermediates required for cytokine production and effector functions.
    explanation: A narrative review summarizes experimental immunometabolic mechanisms; this does not measure glycolytic flux in a representative ARDS cohort.
  biological_processes:
  - preferred_term: glycolytic process
    term:
      id: GO:0006096
      label: glycolytic process
    modifier: INCREASED
  downstream:
  - target: Pulmonary Cytokine and Chemokine Release
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Experimental immunometabolic models suggest that glycolytic programming can support inflammatory effector production; patient-specific causality remains unresolved.
    hypothesis_groups:
    - immunometabolic_resilience_model
    evidence:
    - reference: PMID:42432720
      reference_title: 'Immunometabolic reprogramming and mitochondrial dysfunction in acute respiratory distress syndrome: mechanisms, metabolic resilience, and therapeutic perspectives- a narrative review.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: When macrophages encounter inflammatory stimuli, they shift from mitochondrial oxidative phosphorylation to aerobic glycolysis, a phenomenon called as the “Warburg effect.” This metabolic transition enables rapid ATP generation and provides biosynthetic intermediates required for cytokine production and effector functions.
      explanation: The review proposes a metabolic contribution to inflammatory effector functions.
- name: Impaired Mitochondrial Respiration
  biological_scale: CELLULAR
  description: Reduced mitochondrial oxidative phosphorylation may compromise energy-dependent cellular functions during lung injury. Human metabolite or blood transcriptomic associations alone do not establish impaired respiration in a particular lung cell population.
  role: modifier
  evidence:
  - reference: PMID:42432720
    reference_title: 'Immunometabolic reprogramming and mitochondrial dysfunction in acute respiratory distress syndrome: mechanisms, metabolic resilience, and therapeutic perspectives- a narrative review.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Disruptions in bioenergetic homeostasis, including impaired mitochondrial oxidative phosphorylation, altered glycolytic flux, defective fatty acid oxidation, and redox imbalance have increasingly been linked to persistent organ dysfunction and adverse outcomes in ARDS and sepsis [6–8].
    explanation: The review presents mitochondrial bioenergetic failure as a proposed contributor, with evidence spanning experimental lung injury and critical illness.
  biological_processes:
  - preferred_term: oxidative phosphorylation
    term:
      id: GO:0006119
      label: oxidative phosphorylation
    modifier: DECREASED
  downstream:
  - target: Impaired Alveolar Fluid Clearance
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Bioenergetic failure may compromise energy-dependent fluid transport; this is an emerging model rather than a universally demonstrated human pathway.
    hypothesis_groups:
    - immunometabolic_resilience_model
    evidence:
    - reference: PMID:42432720
      reference_title: 'Immunometabolic reprogramming and mitochondrial dysfunction in acute respiratory distress syndrome: mechanisms, metabolic resilience, and therapeutic perspectives- a narrative review.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: This bioenergetic failure directly compromises the high ATP demands required for active epithelial ion transport and sodium-potassium ATPase pump mechanics [26].
      explanation: The review proposes a bioenergetic contribution to active epithelial transport; the human causal bridge remains unresolved.
- name: Alveolar Type 2 Cell Proliferation
  biological_scale: CELLULAR
  description: Surviving ATII cells proliferate during epithelial regeneration, supplying replacement epithelial cells and a provisional barrier. This response does not guarantee complete recovery.
  role: mediator
  evidence:
  - &id007
    reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: To repair the damaged epithelium, surviving alveolar type II (ATII) cells replace lost epithelial cells via proliferation and differentiation into alveolar type I (ATI) cells.
    explanation: Proliferation and subsequent differentiation are distinct epithelial repair processes; detailed lineage evidence is largely experimental.
  cell_types:
  - preferred_term: pulmonary alveolar type 2 cell
    term:
      id: CL:0002063
      label: pulmonary alveolar type 2 cell
  downstream:
  - target: Alveolar Type 2 to Type 1 Differentiation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Expanded ATII progenitors can generate ATI cells during repair, with intermediate states unresolved here.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: To repair the damaged epithelium, surviving alveolar type II (ATII) cells replace lost epithelial cells via proliferation and differentiation into alveolar type I (ATI) cells.
      explanation: Proliferation and subsequent differentiation are distinct epithelial repair processes; detailed lineage evidence is largely experimental.
- name: Alveolar Type 2 to Type 1 Differentiation
  biological_scale: CELLULAR
  description: ATII-derived cells can differentiate into thin ATI cells during alveolar repair. Lineage and signaling details are supported largely by experimental models, rather than direct lineage tracing in patients.
  role: mediator
  evidence:
  - *id007
  cell_types:
  - preferred_term: pulmonary alveolar type 2 cell
    term:
      id: CL:0002063
      label: pulmonary alveolar type 2 cell
  - preferred_term: pulmonary alveolar type 1 cell
    term:
      id: CL:0002062
      label: pulmonary alveolar type 1 cell
- name: Excess Pulmonary Collagen Deposition
  biological_scale: TISSUE
  description: Fibroblast collagen deposition can become excessive during dysregulated repair and contribute to persistent fibrotic structural change. This is an alternative nonresolving course in a subset, not an obligatory stage.
  role: outcome
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Fibroblasts secrete epithelial growth factors and deposit collagen, which, if excessive, can lead to fibrosis.
    explanation: Fibroblast collagen deposition can become excessive and contribute to fibrosis.
  downstream:
  - target: Pulmonary fibrosis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: The process contributes to this clinical manifestation.
    hypothesis_groups:
    - alveolar_capillary_injury_model
    evidence:
    - reference: PMID:30872586
      reference_title: Acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: INDIRECT
      snippet: Fibroblasts secrete epithelial growth factors and deposit collagen, which, if excessive, can lead to fibrosis.
      explanation: The conditional wording supports possible excessive collagen deposition rather than inevitable fibrosis.
  biological_processes:
  - preferred_term: collagen biosynthetic process
    term:
      id: GO:0032964
      label: collagen biosynthetic process
    modifier: INCREASED
environmental:
- name: Inhalation of chlorine gas
  description: Chlorine is among the commonest chemical causes of acute lung injury, encountered through transport accidents, industrial spills, water treatment and swimming-pool exposures, and deliberate release. Inhaled chlorine reacts in the airway to form oxidative products, so the insult delivered to the alveolar-capillary interface is chemical and oxidative rather than infectious or mechanical.
  exposure_term:
    preferred_term: inhalation of chlorine gas
    term:
      id: ECTO:9000077
      label: exposure to chlorine
  exposure_classifications:
    hazard_agent_type:
    - classification_value: CHEMICAL
    exposure_route:
    - classification_value: INHALATION
      notes: Inhalation is the route by which chlorine reaches the alveolar-capillary interface; dermal and ocular contact cause local irritation without this mechanism.
    exposure_duration:
    - classification_value: ACUTE
      notes: The ARDS-producing exposures are short, high-concentration events (spills, accidents, release), not the chronic low-level occupational and swimming-pool exposures that produce airway hyperreactivity.
  influences_mechanisms:
  - target: Direct Pulmonary or Indirect Systemic Insult
    environmental_effect: TRIGGERS
    causal_link_type: DIRECT
    description: Halogen inhalation is a direct pulmonary insult, entering the mechanism at the trigger node alongside pneumonia, aspiration and contusion.
    evidence:
    - reference: PMID:29722341
      reference_title: Halogen Inhalation-Induced Lung Injury and Acute Respiratory Distress Syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Chlorine is highly toxic by inhalation, leading to dyspnea, hypoxemia, airway obstruction, pneumonitis, pulmonary edema, and acute respiratory distress syndrome (ARDS).
      explanation: States the causal path from inhalational chlorine exposure to ARDS, supporting the exposure acting on the trigger node.
      directness: DIRECT
      quote_role: REVIEW_SYNTHESIS
  notes: Bound to ECTO:9000077 (exposure to chlorine), confirmed against the ontology service. This entry was originally scoped to "irritant halogen gases" and bound to the substance-level ECTO:0000231 while the service was unreachable; it is now narrowed to chlorine so the binding, the name and the quoted evidence all describe the same agent. Bromine is curated as a separate entry because ECTO has no bromine exposure class, and binding the chlorine term to an entry that also asserted bromine would have manufactured a narrower match than the claim.
  evidence:
  - reference: PMID:20601629
    reference_title: 'Chlorine gas inhalation: human clinical evidence of toxicity and experience in animal models.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: More severely affected individuals may suffer acute lung injury (ALI) and/or acute respiratory distress syndrome (ARDS).
    explanation: Human clinical evidence that chlorine exposure reaches ARDS at the severe end of its dose-response, rather than causing airway irritation alone.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:20601629
    reference_title: 'Chlorine gas inhalation: human clinical evidence of toxicity and experience in animal models.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Humans can come into contact with chlorine gas during short-term, high-level exposures due to traffic or rail accidents, spills, or other disasters.
    explanation: Documents the exposure scenarios, which is what makes this an environmental entry rather than a purely clinical trigger.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
- name: Inhalation of bromine gas
  description: Acute bromine inhalation can cause bronchospasm, airway hyperresponsiveness and severe acute lung injury including ARDS. Concentration, duration and species affect toxicity; experimental mouse mechanisms and rescue studies do not establish a human antidote.
  exposure_classifications:
    hazard_agent_type:
    - classification_value: CHEMICAL
    exposure_route:
    - classification_value: INHALATION
    exposure_duration:
    - classification_value: ACUTE
  influences_mechanisms:
  - target: Direct Pulmonary or Indirect Systemic Insult
    environmental_effect: TRIGGERS
    causal_link_type: DIRECT
    description: Bromine inhalation is a direct pulmonary insult acting at the trigger node.
    evidence:
    - reference: PMID:29722341
      reference_title: Halogen Inhalation-Induced Lung Injury and Acute Respiratory Distress Syndrome.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Although bromine is less reactive and oxidative than chlorine, inhalation also results in bronchospasm, airway hyperresponsiveness, ARDS, and even death.
      explanation: States the causal path from bromine inhalation to ARDS, supporting the exposure acting on the trigger node.
      directness: DIRECT
      quote_role: REVIEW_SYNTHESIS
  notes: Deliberately left without an exposure_term. ECTO was searched via the ontology service and has no bromine exposure class - the nearest hit, ECTO:9002162 (exposure to brominated flame retardant), is a different agent and binding it would misclassify the exposure. Falling back to the generic ECTO:0000231 was also rejected, because that is the binding this PR is narrowing away from. `just environmental-term-audit` will report this entry as UNBOUND and that is the correct outcome, not a gap to close.
  evidence:
  - reference: PMID:29722341
    reference_title: Halogen Inhalation-Induced Lung Injury and Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Exposure to halogens, such as chlorine or bromine, results in environmental and occupational hazard to the lung and other organs.
    explanation: Establishes bromine alongside chlorine as an inhalational halogen hazard to the lung.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
- name: Smoke inhalation
  description: Smoke inhalation exposes the respiratory tract to toxic gases and particles that can injure distal lung and impair surfactant. Thermal injury primarily affects the upper airway; it is not treated as the alveolar mechanism. ARDS may coexist with cutaneous burns and other fire-related injuries.
  exposure_term:
    preferred_term: inhalation of combustion smoke
    term:
      id: ECTO:7000059
      label: exposure to smoke
  exposure_classifications:
    hazard_agent_type:
    - classification_value: CHEMICAL
      notes: Recorded as CHEMICAL for the toxic gases and fine particulates that dominate the alveolar injury, though fire smoke also delivers a PHYSICAL thermal component to the upper airway.
    exposure_route:
    - classification_value: INHALATION
    exposure_duration:
    - classification_value: ACUTE
  influences_mechanisms:
  - target: Direct Pulmonary or Indirect Systemic Insult
    environmental_effect: TRIGGERS
    causal_link_type: DIRECT
    description: Smoke inhalation acts as a direct pulmonary insult at the trigger node.
    evidence:
    - reference: PMID:31068086
      reference_title: 'Preclinical and clinical studies of smoke-inhalation-induced acute lung injury: update on both pathogenesis and innovative therapy.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Smoke-inhalation-induced acute lung injury (SI-ALI) is a leading cause of morbidity and mortality in victims of fire tragedies.
      explanation: Establishes smoke inhalation as a cause of acute lung injury acting at the trigger node.
      directness: DIRECT
      quote_role: REVIEW_SYNTHESIS
  notes: 'Bound to ECTO:7000059 (exposure to smoke), confirmed against the ontology service. This entry was originally bound to ECTO:0000231 (exposure to chemical) while the service was unreachable, which was not merely broad but in the wrong branch: ECTO classifies exposure to smoke under exposure to environmental material, not under exposure to chemical, which matches the fact that fire smoke is a mixture of combustion products rather than a single chemical agent. ECTO:6000029 (exposure to tobacco smoking) remains deliberately unused: it denotes tobacco smoking, a different exposure from inhaling combustion products in a fire, and reusing it would misclassify the exposure while validating cleanly.'
  evidence:
  - reference: PMID:31068086
    reference_title: 'Preclinical and clinical studies of smoke-inhalation-induced acute lung injury: update on both pathogenesis and innovative therapy.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Approximately 22% of all burn patients are diagnosed with SI-ALI, leading to at least 30% of the overall fire-associated mortality.
    explanation: Quantifies the burden, supporting this as a substantive exposure route rather than a rare case-report association.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
histopathology:
- name: Diffuse Alveolar Damage with Hyaline Membrane Formation
  description: ARDS histology can show intraalveolar edema, inflammation, hyaline membrane formation, and alveolar hemorrhage in a diffuse-alveolar-damage pattern. These findings are variable and are neither universal nor required for the clinical diagnosis.
  evidence:
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Histological findings vary and often include intraalveolar edema, inflammation, hyaline membrane formation, and alveolar hemorrhage, often termed diffuse alveolar damage; however, these histological features are not always present and are not necessary for a clinical diagnosis of ARDS (26).
    explanation: The consensus document supports the characteristic diffuse-alveolar-damage pattern and directly supplies the non-universality and diagnostic caveat.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
biochemical:
- name: Bronchoalveolar lavage L-lactate
  presence: INCREASED
  biomarker_term:
    preferred_term: lactate
    term:
      id: CHEBI:24996
      label: lactate
  context: Untargeted LC-MS of convenience BAL samples from 18 ARDS patients and eight healthy controls found higher L-lactate; the RPLC estimate was 4.35-fold. Sampling was early and cross-sectional, with heterogeneous disease, ventilation and medication exposure. This is an exploratory compartment-specific association, not a diagnostic threshold or proof of intracellular glycolytic flux.
  evidence:
  - reference: PMID:24289193
    reference_title: Untargeted LC-MS metabolomics of bronchoalveolar lavage fluid differentiates acute respiratory distress syndrome from health.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Despite the certain technical limitations of our analytical approach, we identified potential differentiating metabolites of ARDS as evidenced by the over four-fold increase in L-lactate and changes in other metabolites associated with energy metabolism (e.g., citrate, creatine, creatinine).32 Citrate, creatine and creatinine are three metabolites that were also found to be increased in ARDS plasma samples by 1D-1H-NMR.9, 26 The remainder of the identified metabolites were specific to BALF.
    explanation: The primary study measures higher BAL lactate, without validating an ARDS-specific clinical assay.
phenotypes:
- category: Respiratory
  name: Hypoxemia
  description: Acute arterial hypoxemia is a defining physiologic manifestation and is severity-classified using PaO2:FiO2 or, under specified conditions, SpO2:FiO2.
  phenotype_term:
    preferred_term: Hypoxemia
    term:
      id: HP:0012418
      label: Hypoxemia
  evidence:
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: The clinical hallmarks of ARDS are arterial hypoxemia and bilateral radiographic opacities associated with increased shunting, increased alveolar dead space, and decreased lung compliance.
    explanation: The consensus definition names arterial hypoxemia as a clinical hallmark.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
- category: Respiratory
  name: Acute hypoxemic respiratory failure
  description: Severe impairment of pulmonary gas exchange can require high-flow oxygen, noninvasive support, or invasive mechanical ventilation.
  phenotype_term:
    preferred_term: Respiratory failure
    term:
      id: HP:0002878
      label: Respiratory failure
  evidence:
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Acute respiratory distress syndrome (ARDS) is a clinical syndrome of acute hypoxemic respiratory failure due to lung inflammation, not caused by cardiogenic pulmonary edema.
    explanation: The global consensus situates ARDS within acute hypoxemic respiratory failure.
- category: Respiratory
  name: Noncardiogenic pulmonary edema
  description: Permeability-mediated protein-rich alveolar edema is central and is not primarily attributable to cardiac failure or fluid overload.
  phenotype_term:
    preferred_term: Pulmonary edema
    term:
      id: HP:0100598
      label: Pulmonary edema
  evidence:
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: The resulting injury leads to pulmonary edema from an increase in pulmonary vascular and alveolar epithelial permeability.
    explanation: The consensus model directly links permeability injury to pulmonary edema.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
- category: Imaging
  name: Bilateral pulmonary opacities
  description: Bilateral loss of aeration is part of the adult global definition, assessed by chest radiography, CT or qualified lung ultrasound and not fully explained by effusions, atelectasis or focal masses. PALICC-2 permits unilateral or bilateral new parenchymal opacity in children.
  phenotype_term:
    preferred_term: Pulmonary opacity
    term:
      id: HP:0031457
      label: Pulmonary opacity
  evidence:
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: The committee agreed that chest imaging criteria should include bilateral radiologic (chest radiography or computed tomography) or ultrasound findings suggestive of loss of lung aeration that are not fully explained by effusions, atelectasis, or nodules/masses.
    explanation: The global definition specifies bilateral imaging abnormalities and the principal exclusions.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
- name: Dyspnea
  category: Respiratory
  phenotype_term:
    preferred_term: Dyspnea
    term:
      id: HP:0002094
      label: Dyspnea
  description: Acute breathlessness and increased work of breathing accompany respiratory distress; symptom intensity varies.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Most patients who present with the early phase of acute lung injury complain of feeling short of breath.
    explanation: The clinical review explicitly reports early breathlessness.
- name: Tachypnea
  category: Respiratory
  phenotype_term:
    preferred_term: Tachypnea
    term:
      id: HP:0002789
      label: Tachypnea
  description: An elevated respiratory rate is a clinical sign of acute respiratory distress.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: On physical examination, they appear to be in moderate or severe respiratory distress with an elevated respiratory rate and tachycardia and they usually are working harder than normal to breathe.
    explanation: The physical-examination description identifies an elevated respiratory rate.
- name: Tachycardia
  category: Cardiovascular
  phenotype_term:
    preferred_term: Tachycardia
    term:
      id: HP:0001649
      label: Tachycardia
  description: Tachycardia can accompany acute respiratory distress and systemic illness; it is not specific to ARDS.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: On physical examination, they appear to be in moderate or severe respiratory distress with an elevated respiratory rate and tachycardia and they usually are working harder than normal to breathe.
    explanation: The same examination description explicitly identifies tachycardia.
- name: Cyanosis
  category: Respiratory
  phenotype_term:
    preferred_term: Cyanosis
    term:
      id: HP:0000961
      label: Cyanosis
  description: Severe hypoxemia may manifest as visible cyanosis, including the nail beds.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Hypoxaemia may manifest with evidence of cyanosis in their fingernail beds.
    explanation: The review describes nail-bed cyanosis as a possible manifestation of hypoxemia.
- name: Hypercapnia
  category: Respiratory
  phenotype_term:
    preferred_term: Hypercapnia
    term:
      id: HP:0012416
      label: Hypercapnia
  description: Impaired CO2 elimination and increased dead space may cause hypercapnia. Protective ventilation can also permit elevated CO2; hypercapnia is not required for diagnosis.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: The vascular injury and alveolar oedema contribute to the decreased ability to excrete CO2 (hypercapnia), accounting for the elevated pulmonary dead space in acute respiratory distress syndrome.
    explanation: The review links impaired carbon-dioxide excretion to pulmonary dead-space abnormalities.
- name: Atelectasis
  category: Respiratory
  phenotype_term:
    preferred_term: Atelectasis
    term:
      id: HP:0100750
      label: Atelectasis
  description: Regional alveolar collapse accompanies loss of aeration; collapse alone does not satisfy the ARDS imaging criterion.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Surfactant dysfunction can then increase atelectasis, which in turn can increase the risk of biophysical injury.
    explanation: The review identifies regional collapse as a consequence of surfactant dysfunction.
- name: Pulmonary fibrosis
  category: Respiratory
  phenotype_term:
    preferred_term: Pulmonary fibrosis
    term:
      id: HP:0002206
      label: Pulmonary fibrosis
  description: Excessive collagen deposition and fibrotic remodeling may occur in a subset with nonresolving injury; this is not inevitable.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Fibroblasts secrete epithelial growth factors and deposit collagen, which, if excessive, can lead to fibrosis.
    explanation: The conditional wording supports possible excessive collagen deposition rather than inevitable fibrosis.
- name: Exercise intolerance
  category: Musculoskeletal
  phenotype_term:
    preferred_term: Exercise intolerance
    term:
      id: HP:0003546
      label: Exercise intolerance
  description: Selected survivors have persistent reduced exercise capacity despite near-normal pulmonary function; this is not a population frequency estimate.
  evidence:
  - reference: PMID:21470008
    reference_title: Functional disability 5 years after acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: 'CONCLUSIONS: Exercise limitation, physical and psychological sequelae, decreased physical quality of life, and increased costs and use of health care services are important legacies of severe lung injury.'
    explanation: The follow-up study identifies persistent exercise limitation after severe lung injury.
- name: Muscle weakness
  category: Musculoskeletal
  phenotype_term:
    preferred_term: Muscle weakness
    term:
      id: HP:0001324
      label: Muscle weakness
  description: Persistent weakness is part of post-critical-illness morbidity in survivors and cannot be assigned exclusively to pulmonary injury.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: With more detailed follow-up evaluations, these investigators observed that survivors of ARDS had significant exercise limitation and poor physical QOL at 1-year follow-up related to marked muscle wasting and weakness; myriad physical disabilities including heterotopic ossification, joint contractures and tracheal stenosis; and cosmetic concerns related to scarring at tracheostomy, central line or chest tube sites.
    explanation: The survivor review explicitly reports weakness; critical illness and treatment can also contribute.
- name: Skeletal muscle atrophy
  category: Musculoskeletal
  phenotype_term:
    preferred_term: Skeletal muscle atrophy
    term:
      id: HP:0003202
      label: Skeletal muscle atrophy
  description: Muscle wasting can persist after critical illness and contribute to functional limitation in ARDS survivors.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: With more detailed follow-up evaluations, these investigators observed that survivors of ARDS had significant exercise limitation and poor physical QOL at 1-year follow-up related to marked muscle wasting and weakness; myriad physical disabilities including heterotopic ossification, joint contractures and tracheal stenosis; and cosmetic concerns related to scarring at tracheostomy, central line or chest tube sites.
    explanation: The survivor review reports muscle wasting, distinct from measured weakness alone.
- name: Memory impairment
  category: Neurologic
  phenotype_term:
    preferred_term: Memory impairment
    term:
      id: HP:0002354
      label: Memory impairment
  description: Follow-up studies describe memory and other cognitive deficits in selected survivors, with critical-illness and premorbid confounding.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: They noted important decrements in attention, concentration, processing speed, memory and executive function that persisted up to 2 years after discharge from intensive care222,223.
    explanation: The review explicitly identifies persistent memory deficits among the observed cognitive outcomes.
- name: Posttraumatic stress symptoms
  category: Psychiatric
  phenotype_term:
    preferred_term: Posttraumatic stress symptoms
    term:
      id: HP:0033676
      label: Posttraumatic stress symptom
  description: Post-traumatic stress disorder and associated symptoms are reported in ARDS survivors; this is a recovery-phase neuropsychological outcome.
  evidence:
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Post-traumatic stress disorder in patients with ARDS has also been described and is associated with decrements in the mental health domains of the 36-Item Short Form Survey (SF-36) QOL measure213.
    explanation: The review identifies post-traumatic stress disorder and its association with mental-health quality of life.
- name: Crackles
  category: Respiratory
  description: Bibasilar crackles may be audible during acute lung injury; the finding is neither universal nor specific.
  phenotype_term:
    preferred_term: Crackles
    term:
      id: HP:0030830
      label: Crackles
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK436002/
    reference_title: Acute Respiratory Distress Syndrome - StatPearls - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Chest auscultation usually reveals rales, especially bibasilar
    explanation: The clinical examination review reports rales as an acute finding.
diagnosis:
- name: Adult global consensus clinical diagnosis
  diagnosis_term:
    preferred_term: clinical assessment
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
  description: Diagnose ARDS when acute or worsening hypoxemic respiratory failure occurs within one week of a predisposing insult or new respiratory symptoms, with bilateral loss of lung aeration on radiography, CT, or qualified ultrasound, and edema not primarily explained by cardiac failure, fluid overload, collapse, effusion, or embolism. Hypoxemia can be identified by PaO2:FiO2 at or below 300 mm Hg or by SpO2:FiO2 at or below 315 when SpO2 is at or below 97%; the global definition includes specified nonintubated and resource-limited pathways. Nonintubated criteria require HFNO at least 30 L/min or NIV/CPAP with at least 5 cm H2O end-expiratory pressure. Intubated criteria require PEEP at least 5 cm H2O. A separate resource-limited category does not require a specific oxygen-delivery device, flow or PEEP. Cardiogenic edema and chronic lung disease can coexist when they do not primarily explain the acute hypoxemia.
  results: Acute bilateral noncardiogenic inflammatory lung injury with qualifying hypoxemia supports the diagnosis; severity and respiratory-support category should be recorded separately.
  evidence:
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'The committee agreed that the current time frame for the diagnosis of ARDS should be retained: acute onset or worsening of hypoxemic respiratory failure is defined as occurring within 1 week of the onset of the predisposing risk factor or within 1 week of new or worsening respiratory symptoms.'
    explanation: This establishes the acute diagnostic time window.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'The committee made four main recommendations: 1) include high-flow nasal oxygen with a minimum flow rate of ⩾30 L/min; 2) use PaO2:FiO2 ⩽ 300 mm Hg or oxygen saturation as measured by pulse oximetry SpO2:FiO2 ⩽ 315 (if oxygen saturation as measured by pulse oximetry is ⩽97%) to identify hypoxemia; 3) retain bilateral opacities for imaging criteria but add ultrasound as an imaging modality, especially in resource-limited areas; and 4) in resource-limited settings, do not require positive end-expiratory pressure, oxygen flow rate, or specific respiratory support devices.'
    explanation: The global definition supplies the oxygenation, imaging, and respiratory-support criteria represented in the diagnostic description.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:37487152
    reference_title: A New Global Definition of Acute Respiratory Distress Syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: The committee agreed on a threshold of oxygen delivery of 30 L/min with HFNO because 30 L/min can provide low levels of PEEP (56).
    explanation: The global definition specifies the nonintubated support threshold.
- name: PALICC-2 pediatric scope and timing
  description: Use for children younger than 18 without active perinatal lung disease, within seven days of a known insult. New unilateral or bilateral parenchymal opacity is sufficient; edema must not be fully cardiac or fluid-overload related. Definitions are ungraded consensus statements.
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: All patients less than 18 years old without active perinatal lung disease should be diagnosed with PARDS using PALICC-2 criteria.
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Symptoms of hypoxemia and radiographic changes must occur within 7 days of a known insult to qualify for PARDS.
    explanation: Timing criterion.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Chest imaging findings of new opacity (or opacities) consistent with acute pulmonary parenchymal disease not explained by atelectasis or effusion are necessary to diagnose PARDS.
    explanation: Bilateral opacities are not mandatory.
  diagnosis_term:
    preferred_term: Clinical Evaluation
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
- name: Confirmed PARDS oxygenation criteria
  description: 'IMV: OI ≥4 or OSI ≥5. Full-face NIV with CPAP/PEEP ≥5 cm H2O: PaO2/FiO2 ≤300 or SpO2/FiO2 ≤250. Assess steady state; use PaO2 preferentially and SpO2 at ≤97% when saturation-based criteria are applied.'
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: 'IMV: OI ≥ 4 or OSI ≥ 5'
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: 'NIV c : Pa o 2 /F io 2 ≤ 300 or Sp o 2 /F io 2 ≤ 250'
    explanation: Table 4 NIV oxygenation threshold; full-face interface and pressure criteria also apply.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Diagnosis of PARDS on NIV (NIV-PARDS) requires full facemask interface with continuous airway positive pressure/positive end-expiratory pressure ≥ 5 cm H2O.
    explanation: The confirmed NIV definition requires a full-face interface.
  diagnosis_term:
    preferred_term: Clinical Evaluation
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
- name: Possible PARDS on nasal support or with unavailable imaging
  description: Nasal CPAP/BiPAP or HFNC ≥1.5 L/kg/min or ≥30 L/min with PaO2/FiO2 ≤300 or SpO2/FiO2 ≤250 and other criteria qualifies as possible PARDS. Missing imaging in resource-limited settings can also support possible PARDS. Pure obstructive airway disease alone does not qualify.
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Patients on a nasal interface of NIV (CPAP or BiPAP) or on HFNC greater than or equal to 1.5 L/kg/min or greater than or equal to 30 L/min should be considered as having possible PARDS if they meet timing, oxygenation, etiology/risk factor, and imaging criteria
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Patients who are missing imaging due to resource limitations should be considered as having possible PARDS if they otherwise meet timing, oxygenation, and risk factor criteria.
    explanation: Resource-limited definition.
  diagnosis_term:
    preferred_term: Clinical Evaluation
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
- name: PARDS severity after stabilization
  description: 'Stratify at least four hours after diagnosis. Severe IMV-PARDS: OI ≥16 or OSI ≥12; severe NIV-PARDS: PaO2/FiO2 ≤100 or SpO2/FiO2 ≤150. Chronic IMV and cyanotic congenital heart disease need acute deterioration but should not receive these OI/OSI risk categories.'
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Subjects with PARDS should be stratified into severity categories after a period of at least 4 hours
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: 'Severe: OI ≥ 16 or OSI ≥ 12'
    explanation: Table 4 invasive severity threshold.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: 'Severe NIV-PARDS: Pa o 2 /F io 2 ≤ 100 or Sp o 2 /F io 2 ≤ 150'
    explanation: Table 4 noninvasive severity threshold.
  diagnosis_term:
    preferred_term: Clinical Evaluation
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
treatments:
- name: Etiology-Directed and Intensive Supportive Care
  description: Identify and treat the precipitating cause while providing oxygenation, hemodynamic support, infection management when indicated, prevention of secondary injury, and organ support. ARDS has no single etiology-specific pharmacologic cure, so supportive strategies are selected by severity and patient context.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Respiratory failure
    term:
      id: HP:0002878
      label: Respiratory failure
  evidence:
  - reference: PMID:39866839
    reference_title: 'Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Given the complexity of the underlying disease, treatment needs to be tailored to the problem.
    explanation: The review supports etiology- and context-specific management of this heterogeneous syndrome.
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
- name: Adult lung-protective mechanical ventilation
  description: 'Strong recommendation, moderate certainty: 4–8 mL/kg predicted body weight with plateau pressure <30 cm H2O. This retained recommendation is broader than the pivotal 6 mL/kg trial protocol.'
  treatment_term:
    preferred_term: mechanical ventilation
    term:
      id: NCIT:C70909
      label: Mechanical Ventilation
  target_phenotypes:
  - preferred_term: Respiratory failure
    term:
      id: HP:0002878
      label: Respiratory failure
  target_mechanisms:
  - target: Ventilator-Induced Lung Injury
    treatment_effect: INHIBITS
    description: Lower tidal volume and plateau-pressure limitation reduce injurious mechanical stretch during invasive ventilation.
    evidence:
    - reference: PMID:10793162
      reference_title: Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Traditional approaches to mechanical ventilation use tidal volumes of 10 to 15 ml per kilogram of body weight and may cause stretch-induced lung injury in patients with acute lung injury and the acute respiratory distress syndrome.
      explanation: The trial directly motivates lower-volume ventilation as prevention of stretch-induced lung injury.
      directness: DIRECT
      quote_role: PRIMARY_RESULT
  evidence:
  - reference: PMID:38032683
    reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We recommend using mechanical ventilation strategies that limit tidal volume (4–8 mL/kg predicted body weight) and inspiratory pressures (plateau pressure <30 cm H2O) in patients with ARDS (strong recommendation, moderate certainty of evidence).
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
- name: Adult prone positioning
  description: For severe adult ARDS, >12 hours daily is strongly recommended with moderate certainty. Individual primary trials may use a longer protocol. ESICM recommends starting after stabilization and optimized ventilation when PaO2/FiO2 remains below 150 mm Hg, with sessions of at least 16 consecutive hours. PROSEVA used this prolonged protocol; its trial outcome applies to the selected study population.
  treatment_term:
    preferred_term: Prone Ventilation
    term:
      id: NCIT:C173751
      label: Prone Ventilation
  target_phenotypes:
  - preferred_term: Hypoxemia
    term:
      id: HP:0012418
      label: Hypoxemia
  target_mechanisms:
  - target: Intrapulmonary Shunting
    treatment_effect: MODULATES
    description: Proning redistributes ventilation and perfusion and recruits dependent lung, thereby improving oxygenation across the shunt-dominated physiology.
    evidence:
    - reference: PMID:39866839
      reference_title: 'Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: The prone position is a readily implementable intervention associated with improved oxygenation due to an increased ventilator–blood flow ratio, more uniform ventilation distribution, increased lung volume, and improved perfusion redistribution during partial alveolar re-expansion in the respiratory-dependent area of the lung.
      explanation: The review directly links prone positioning to redistribution of ventilation and perfusion and improved oxygenation.
      directness: DIRECT
      quote_role: REVIEW_SYNTHESIS
  evidence:
  - reference: PMID:38032683
    reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We recommend prone positioning for >12 hours per day in patients with severe ARDS (strong recommendation, moderate certainty of evidence).
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:37326646
    reference_title: 'ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Therefore, the evidence used for this question is the same as that for previous the question.Recommendation 7.2We recommend starting prone position in patients with ARDS receiving invasive mechanical ventilation early after intubation, after a period of stabilization during which low tidal volume is applied and PEEP adjusted and at the end of which the PaO2/FiO2 remains < 150 mmHg; and proning should be applied for prolonged sessions (16 consecutive hours or more) to reduce mortality.Strong recommendation; high level of evidence in favor.This recommendation applies also to ARDS from COVID-19.Strong recommendation; moderate level of evidence in favor for indirectness.
    explanation: The ESICM recommendation specifies timing, oxygenation and session duration.
- name: Conservative Fluid Management After Hemodynamic Stabilization
  description: 'In adults after shock and tissue hypoperfusion have resolved, conservative fluid management can limit superimposed hydrostatic loading. FACTT randomized 1000 patients for seven days: ventilator-free days improved, but 60-day mortality did not differ significantly. This is not fluid restriction during active shock.'
  treatment_term:
    preferred_term: fluid therapy
    term:
      id: NCIT:C116537
      label: Fluid Therapy
  target_phenotypes:
  - preferred_term: Pulmonary edema
    term:
      id: HP:0100598
      label: Pulmonary edema
  target_mechanisms:
  - target: Protein-Rich Alveolar Edema
    treatment_effect: INHIBITS
    description: After hemodynamic stabilization, conservative fluid management limits the fluid burden superimposed on permeability edema and improves lung function.
    evidence:
    - reference: PMID:16714767
      reference_title: Comparison of two fluid-management strategies in acute lung injury.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Although there was no significant difference in the primary outcome of 60-day mortality, the conservative strategy of fluid management improved lung function and shortened the duration of mechanical ventilation and intensive care without increasing nonpulmonary-organ failures.
      explanation: FACTT directly demonstrates improved lung function from the conservative strategy while retaining its neutral mortality result.
      directness: DIRECT
      quote_role: PRIMARY_RESULT
  evidence:
  - reference: PMID:16714767
    reference_title: Comparison of two fluid-management strategies in acute lung injury.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Although there was no significant difference in the primary outcome of 60-day mortality, the conservative strategy of fluid management improved lung function and shortened the duration of mechanical ventilation and intensive care without increasing nonpulmonary-organ failures.
    explanation: The randomized FACTT trial supports conservative management for pulmonary and support-duration outcomes while preserving its neutral mortality result.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:30872586
    reference_title: Acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: In 2006, a randomized clinical trial in 1,000 patients with ARDS demonstrated that adopting a fluid-conservative approach after vasopressor-dependent shock had resolved led to an increase in ventilator-free days and improved oxygenation index185.
    explanation: The review specifies the clinical timing boundary for fluid-conservative management.
- name: Adult corticosteroids
  description: Conditional recommendation with moderate certainty specifically applies to intubated adults. Agent, dose and duration remain unresolved; timing and etiology matter and initiation beyond two weeks may be harmful.
  treatment_term:
    preferred_term: systemic corticosteroid therapy
    term:
      id: NCIT:C122080
      label: Systemic Corticosteroid Therapy
    therapeutic_agent:
    - preferred_term: corticosteroid
      term:
        id: CHEBI:50858
        label: corticosteroid
  target_mechanisms:
  - target: Pulmonary Cytokine and Chemokine Release
    treatment_effect: INHIBITS
    description: Anti-inflammatory corticosteroids inhibit synthesis of proinflammatory mediators; clinical selection remains population- and timing-dependent.
    evidence:
    - reference: PMID:38032683
      reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Corticosteroids are anti-inflammatory medications that inhibit the synthesis of proinflammatory mediators present in ARDS.
      explanation: The guideline directly states the anti-inflammatory mechanism used to join corticosteroid treatment to cytokine activation.
      directness: DIRECT
      quote_role: REVIEW_SYNTHESIS
  evidence:
  - reference: PMID:38032683
    reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We suggest using corticosteroids for patients with ARDS (conditional recommendation, moderate certainty of evidence).
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:38032683
    reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: this recommendation is based on evidence from trials on intubated patients with ARDS and applies specifically to this group
    explanation: The population is explicitly intubated ARDS.
  - reference: PMID:38032683
    reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: the initiation of corticosteroid treatment >2 weeks after the onset of ARDS may be associated with harm
    explanation: Late initiation caveat from the implementation discussion.
  target_phenotypes:
  - preferred_term: Respiratory failure
    term:
      id: HP:0002878
      label: Respiratory failure
- name: Adult higher PEEP without prolonged recruitment
  description: Conditional recommendation for higher PEEP without recruitment maneuvers in moderate-to-severe adult ARDS. Prolonged recruitment (PEEP ≥35 cm H2O for >60 seconds) is strongly discouraged. Titrate with respiratory and hemodynamic monitoring; mild ARDS does not inherit this recommendation. ESICM found insufficient evidence to recommend routine higher versus lower PEEP/FiO2 titration for mortality across all ARDS. The ATS conditional recommendation is restricted to moderate-to-severe disease.
  treatment_term:
    preferred_term: mechanical ventilation
    term:
      id: NCIT:C70909
      label: Mechanical Ventilation
  target_phenotypes:
  - preferred_term: Hypoxemia
    term:
      id: HP:0012418
      label: Hypoxemia
  evidence:
  - reference: PMID:38032683
    reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We suggest using higher PEEP without LRMs rather than lower PEEP in patients with moderate to severe ARDS (conditional recommendation, low-moderate certainty).
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:38032683
    reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We recommend against using prolonged (PEEP ⩾35 cm H2O for >60 s) LRMs in patients with moderate to severe ARDS (strong recommendation, moderate certainty).
    explanation: The negative recruitment recommendation is stronger than the conditional PEEP recommendation.
  - reference: PMID:37326646
    reference_title: 'ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We are unable to make a recommendation for or against routine PEEP titration with a higher PEEP/FiO2 strategy versus a lower PEEP/FiO2 strategy to reduce mortality in patients with ARDS.
    explanation: The broader ESICM population and analysis should not be conflated with the ATS conditional recommendation.
- name: Adult neuromuscular blockade
  description: Conditional recommendation, low certainty, for early (<48 hours) severe ARDS (PaO2/FiO2 ≤100). Use selectively when deep sedation is already required or persistent dyssynchrony compromises protection. Limit duration to 48 hours when possible; mortality advantage was not established against light sedation. ESICM 2023 recommends against routine continuous infusions for mortality reduction in unselected moderate-to-severe non-COVID ARDS; this differs in scope from ATS selective early severe use. ICU-acquired weakness and sedation harms matter.
  treatment_term:
    preferred_term: neuromuscular blockade
    term:
      id: NCIT:C158070
      label: Neuromuscular Blockade
    therapeutic_agent:
    - preferred_term: cisatracurium
      term:
        id: CHEBI:140621
        label: cisatracurium
  target_phenotypes:
  - preferred_term: Respiratory failure
    term:
      id: HP:0002878
      label: Respiratory failure
  target_mechanisms:
  - target: Ventilator-Induced Lung Injury
    treatment_effect: INHIBITS
    description: In selected early severe ARDS, blockade can reduce patient-ventilator dyssynchrony and thereby limit ventilator-induced injury.
    evidence:
    - reference: PMID:38032683
      reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: NMBAs are a commonly used adjunctive therapy for patients with ARDS (16, 56). The mechanism of benefit is unclear, but likely involves decreasing ventilator-induced lung injury via a reduction in patient–ventilator dyssynchrony in addition to reducing oxygen consumption, inflammation, and alveolar fluid (57–59).
      explanation: The guideline explicitly links neuromuscular blockade to reduced dyssynchrony and likely reduction of ventilator-induced injury.
      directness: DIRECT
      quote_role: REVIEW_SYNTHESIS
  evidence:
  - reference: PMID:38032683
    reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We suggest using neuromuscular blockade in patients with early severe ARDS (conditional recommendation, low certainty)
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:38032683
    reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: NMBA duration should be limited to a maximum of 48 hours whenever possible.
    explanation: The guideline limits treatment duration when feasible.
  - reference: PMID:37326646
    reference_title: 'ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Only indirect evidence from non-COVID studies was available.Recommendation 8.1We recommend against the routine use of continuous infusions of NMBA to reduce mortality in patients with moderate-to-severe ARDS not due to COVID-19.Strong recommendation, moderate level of evidence.We are unable to make a recommendation for or against the routine use of continuous infusions of NMBA to reduce mortality in patients with moderate-to-severe ARDS due to COVID-19.No recommendation; no evidence.
    explanation: The ESICM recommendation argues against indiscriminate continuous blockade.
- name: Adult venovenous ECMO
  description: Conditional recommendation, low certainty, for selected severe adult ARDS despite optimized care. Consider reversibility, very severe gas-exchange impairment, early disease, futility risk and center expertise. VV-ECMO supports oxygenation and carbon-dioxide removal; bleeding is a material harm.
  treatment_term:
    preferred_term: extracorporeal membrane oxygenation
    term:
      id: NCIT:C171507
      label: Extracorporeal Membrane Oxygenation
  target_phenotypes:
  - preferred_term: Respiratory failure
    term:
      id: HP:0002878
      label: Respiratory failure
  target_mechanisms:
  - target: Intrapulmonary Shunting
    treatment_effect: BYPASSES
    description: Extracorporeal oxygenation and CO2 removal support gas exchange while the lung recovers; VV-ECMO does not directly provide circulatory support or repair the barrier.
    evidence:
    - reference: PMID:37326646
      reference_title: 'ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: DIRECT
      snippet: VV-ECMO is used to support or replace gas exchange.
      explanation: The guideline describes extracorporeal gas exchange rather than direct hemodynamic support.
  evidence:
  - reference: PMID:38032683
    reference_title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We suggest the use of VV-ECMO in selected patients with severe ARDS (conditional recommendation, low certainty of evidence)
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
- name: High-flow nasal oxygen in adult acute hypoxemic respiratory failure
  description: ESICM strongly recommends HFNO over conventional oxygen for nonventilated adult acute hypoxemic respiratory failure not due to cardiogenic edema or COPD exacerbation, to reduce intubation risk. Mortality benefit was not established. Close monitoring and timely escalation are necessary; this evidence is broader than Berlin-defined ARDS.
  treatment_term:
    preferred_term: High-Flow Nasal Cannula Oxygen Therapy
    term:
      id: NCIT:C171510
      label: High-Flow Nasal Cannula Oxygen Therapy
  evidence:
  - reference: PMID:37326646
    reference_title: 'ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We recommend that non-mechanically ventilated patients with AHRF not due to cardiogenic pulmonary edema or acute exacerbation of COPD receive HFNO as compared to conventional oxygen therapy to reduce the risk of intubation
    explanation: This recommendation addresses intubation risk in a defined noncardiogenic AHRF population, not all ARDS outcomes.
- name: Avoid prolonged high-pressure recruitment maneuvers in adult ARDS
  description: Prolonged high-pressure recruitment is strongly discouraged because potential harms include hemodynamic collapse and barotrauma. ESICM defines airway pressure at least 35 cm H2O for at least one minute; the ATS definition uses PEEP at least 35 cm H2O for more than 60 seconds.
  treatment_term:
    preferred_term: Mechanical Ventilation
    term:
      id: NCIT:C70909
      label: Mechanical Ventilation
  evidence:
  - reference: PMID:37326646
    reference_title: 'ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We recommend against use of prolonged high-pressure recruitment maneuvers (defined as airway pressure maintained ≥ 35 cmH2O for at least one minute) to reduce mortality of patients with ARDS.
    explanation: The recommendation explicitly discourages the specified prolonged maneuver for mortality reduction.
- name: Avoid routine brief high-pressure recruitment maneuvers in adult ARDS
  description: ESICM suggests against routine brief high-pressure recruitment for mortality reduction. Selected derecruitment episodes may warrant individualized rescue with monitoring and immediate cessation if cardiovascular instability occurs; this is not routine recruitment.
  treatment_term:
    preferred_term: Mechanical Ventilation
    term:
      id: NCIT:C70909
      label: Mechanical Ventilation
  evidence:
  - reference: PMID:37326646
    reference_title: 'ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: routine use of brief high-pressure recruitment maneuvers (defined as airway pressure maintained ≥ 35 cmH2O for less than one minute) to reduce mortality in patients with ARDS.Weak recommendation; high level of evidence of no effect.This suggestion applies also to ARDS from COVID-19.Weak recommendation; moderate level of evidence of no effect for indirectness.
    explanation: The recommendation discourages routine brief maneuvers; it does not prohibit individualized monitored rescue in every circumstance.
- name: Restrict extracorporeal carbon-dioxide removal to trials
  notes: Live NCIT searches for extracorporeal carbon dioxide removal and carbon dioxide removal found no specific matching intervention. The broad supportive-care binding is retained; VV-ECMO is not an equivalent procedure.
  description: ESICM recommends against ECCO2R for mortality prevention outside randomized trials. It differs from VV-ECMO and has bleeding risks without demonstrated survival benefit in the analyzed trials.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:37326646
    reference_title: 'ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We recommend against the use of ECCO2R for the treatment of ARDS not due to COVID-19 to prevent mortality outside of randomized controlled trials.
    explanation: The recommendation restricts ECCO2R for mortality prevention to randomized trials.
- name: Pediatric lung-protective ventilation
  description: 'Conditional recommendations: 6–8 mL/kg, lower if pressure limits require, caution below 4 mL/kg; plateau ≤28 cm H2O (29–32 may be acceptable with reduced chest-wall compliance), driving pressure ≤15. Scale volumes to the lesser of predicted or actual weight.'
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We suggest the use of physiologic tidal volumes between 6 and 8 mL/kg in patients with PARDS compared with supraphysiologic tidal volumes (> 8 mL/kg).
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: The lesser of predicted body weight or actual body weight should be used.
    explanation: Pediatric weight-scaling differs from a simple adult PBW rule.
  treatment_term:
    preferred_term: Mechanical Ventilation
    term:
      id: NCIT:C70909
      label: Mechanical Ventilation
  target_phenotypes:
  - preferred_term: Respiratory failure
    term:
      id: HP:0002878
      label: Respiratory failure
- name: Pediatric PEEP titration
  description: Typically maintain PEEP at or above the lower-PEEP/higher-FiO2 ARDSNet table (strong, moderate certainty); individualize to oxygen delivery, hemodynamics and static compliance while respecting pressure limits. Sustained inflation recruitment cannot be recommended.
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We recommend that PEEP levels should typically be maintained at or above the lower PEEP/higher Fio2 table from the ARDS Network protocol
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Sustained inflation maneuvers cannot be recommended.
    explanation: Routine adult recruitment strategies must not be imported.
  treatment_term:
    preferred_term: Mechanical Ventilation
    term:
      id: NCIT:C70909
      label: Mechanical Ventilation
  target_phenotypes:
  - preferred_term: Hypoxemia
    term:
      id: HP:0012418
      label: Hypoxemia
- name: Pediatric selective corticosteroid use
  description: The guideline conditionally recommends against routine steroids, with low certainty. Selected etiologies such as SARS-CoV-2 may differ; this is separate from the adult ATS recommendation.
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We suggest against the routine use of corticosteroids in patients with PARDS compared with selective use of steroids.
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  treatment_term:
    preferred_term: systemic corticosteroid therapy
    term:
      id: NCIT:C122080
      label: Systemic Corticosteroid Therapy
    therapeutic_agent:
    - preferred_term: corticosteroid
      term:
        id: CHEBI:50858
        label: corticosteroid
- name: Pediatric selective neuromuscular blockade
  description: Use minimal effective blockade with sedation only when protective ventilation cannot otherwise be achieved; conditional, very-low certainty. Monitor and titrate to the intended depth. No universal adult early/severe timing rule is implied.
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We suggest that minimal, yet effective, neuromuscular blockade (NMB) be used in conjunction with sedation in comparison to the use of sedation alone if effective and protective MV cannot be achieved.
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  treatment_term:
    preferred_term: neuromuscular blockade
    term:
      id: NCIT:C158070
      label: Neuromuscular Blockade
    therapeutic_agent:
    - preferred_term: cisatracurium
      term:
        id: CHEBI:140621
        label: cisatracurium
- name: Pediatric prone-positioning trial
  description: Evidence is insufficient to recommend for or against routine proning. It can be considered for refractory hypoxemia, with response assessed; no duration recommendation is established.
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: There are insufficient data to support or refute the use of prone positioning in patients with PARDS.
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We cannot make recommendations on the duration of prone positioning.
    explanation: Adult prone-duration rules are not pediatric evidence.
  treatment_term:
    preferred_term: Prone Ventilation
    term:
      id: NCIT:C173751
      label: Prone Ventilation
- name: Pediatric ECMO evaluation
  description: Evaluate potentially reversible severe PARDS when protective ventilation fails gas exchange, using serial expert assessment. There are no strict supported selection cutoffs. Prefer venovenous ECMO when cardiac function is adequate; pediatric recommendations are conditional.
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We suggest that patients with a potentially reversible cause of severe PARDS should be evaluated for extracorporeal membrane oxygenation (ECMO) when lung protective strategies result in inadequate gas exchange.
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: There is no evidence to support strict criteria for the selection of patients who will benefit from ECMO in PARDS.
    explanation: Adult numerical eligibility cutoffs cannot be assumed.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We suggest the use of venovenous ECMO over venoarterial ECMO in patients with PARDS who have adequate cardiac function.
    explanation: Cardiac adequacy qualifies the preferred circuit.
  treatment_term:
    preferred_term: extracorporeal membrane oxygenation
    term:
      id: NCIT:C171507
      label: Extracorporeal Membrane Oxygenation
  target_phenotypes:
  - preferred_term: Respiratory failure
    term:
      id: HP:0002878
      label: Respiratory failure
- name: Pediatric fluid management
  description: Establish individualized daily fluid goals to maintain oxygen delivery and organ function while preventing overload; conditional, low certainty. This is not indiscriminate restriction during shock.
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: We suggest that patients with PARDS should receive fluids with the daily fluid goal collaboratively established by the interprofessional team to maintain optimal oxygen delivery and preserve end organ function, while preventing fluid overload.
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  treatment_term:
    preferred_term: fluid therapy
    term:
      id: NCIT:C116537
      label: Fluid Therapy
  target_phenotypes:
  - preferred_term: Pulmonary edema
    term:
      id: HP:0100598
      label: Pulmonary edema
- name: Pediatric post-discharge assessment
  description: Screen within three months for pulmonary and broader post-ICU morbidity. Include spirometry when developmentally feasible and refer persistent deficits; infants/toddlers need additional assessment before school. These are good-practice statements.
  evidence:
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Patients with PARDS should be screened for pulmonary function abnormalities within the first three months after hospital discharge.
    explanation: Guideline recommendation; this is evidence synthesis, not a new patient-outcome experiment.
  - reference: PMID:36661420
    reference_title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: For patients who survive PARDS, health-related quality of life, physical, neurocognitive, emotional, family, and social function should be evaluated within three months of hospital discharge.
    explanation: Follow-up extends beyond lung function.
  treatment_term:
    preferred_term: Clinical Evaluation
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
- name: Inhaled GM-CSF Host-Directed Therapy
  description: >-
    Nebulized recombinant human GM-CSF (molgramostim) administered as host-directed
    therapy to promote alveolar macrophage activation and restoration of barrier
    function. A phase 2a trial investigated safety, feasibility, and efficacy of
    low-dose (150 μg) or high-dose (450 μg) administration for 3 days in
    pneumonia-related ARDS. While the primary composite outcome did not reach
    significance, high-dose treatment showed beneficial secondary outcomes including
    upregulation of CD206 on alveolar macrophages (significant against both placebo
    and low dose; HLA-DR upregulation was significant only against low dose),
    improved oxygenation, and decreased SOFA scores without increasing alveolar or
    systemic inflammation.
  treatment_term:
    preferred_term: pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: molgramostim
      term:
        id: NCIT:C77591
        label: Molgramostim
  target_phenotypes:
  - preferred_term: Respiratory failure
    term:
      id: HP:0002878
      label: Respiratory failure
  - preferred_term: Hypoxemia
    term:
      id: HP:0012418
      label: Hypoxemia
  target_mechanisms:
  - target: Alveolar Macrophage Activation
    treatment_effect: MODULATES
    description: >-
      GM-CSF promotes differentiation of recruited monocyte-derived macrophages
      toward homeostatic tissue-resident alveolar macrophages (marked by CD206
      upregulation), which participate in inflammation resolution and tissue
      repair rather than amplifying inflammatory injury.
    evidence:
    - reference: PMID:42769414
      reference_title: "Inhaled granulocyte-macrophage colony-stimulating factor (molgramostim) as host-directed therapy for pneumonia-related acute respiratory distress syndrome: a multicentre, randomised, placebo-controlled phase 2a trial (GI-HOPE)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        high-dose treatment caused upregulation of HLA-DR and CD206 on alveolar
        macrophages, indicating deposition in the alveolar compartment and
        beneficial macrophage activation (HLA-DR: p=0.0406 versus low dose,
        p=0.1841 versus placebo; CD206: p=0.009 versus low dose, p=0.0179 versus
        placebo)
      explanation: >-
        The trial directly measured HLA-DR and CD206 upregulation on alveolar
        macrophages as biomarkers of beneficial macrophage activation.
  evidence:
  - reference: PMID:42769414
    reference_title: "Inhaled granulocyte-macrophage colony-stimulating factor (molgramostim) as host-directed therapy for pneumonia-related acute respiratory distress syndrome: a multicentre, randomised, placebo-controlled phase 2a trial (GI-HOPE)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      high-dose rhGM-CSF treatment revealed a favourable profile of oxygenation
      at the end of analysis compared to time-points before inhalation (p=0.095
      and p=0.0175) or compared to the low-dose and placebo groups (p=0.0063 and
      p=0.0198; visit 13), and was associated with decreased SOFA scores in the
      high-dose group over time (p=0.0013 and p=0.00023 compared to low dose and
      placebo).
    explanation: >-
      The phase 2a trial supports improved oxygenation and SOFA-score trends with
      high-dose GM-CSF; the composite primary outcome did not reach significance,
      so the findings remain secondary-outcome and exploratory.
  - reference: PMID:42769414
    reference_title: "Inhaled granulocyte-macrophage colony-stimulating factor (molgramostim) as host-directed therapy for pneumonia-related acute respiratory distress syndrome: a multicentre, randomised, placebo-controlled phase 2a trial (GI-HOPE)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Importantly, inhaled rhGM-CSF did not increase alveolar or systemic
      inflammation.
    explanation: >-
      Safety assessment confirms no increase in inflammatory markers, supporting
      feasibility of this host-directed approach without triggering adverse
      inflammation amplification.
  - reference: PMID:42769414
    reference_title: "Inhaled granulocyte-macrophage colony-stimulating factor (molgramostim) as host-directed therapy for pneumonia-related acute respiratory distress syndrome: a multicentre, randomised, placebo-controlled phase 2a trial (GI-HOPE)."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      however, it did not lead to differences in the GI-HOPE score.
    explanation: >-
      The trial's prespecified primary endpoint, the composite GI-HOPE score, did
      not differ between arms, so clinical efficacy in ARDS is not established.
  review_notes: >-
    This is an early-stage phase 2a trial with secondary-outcome support and no
    primary-outcome success. High-dose treatment shows promise but requires
    phase 3 validation before clinical adoption. The mechanism of benefit appears
    to involve immune polarization toward reparative phenotypes rather than
    inflammatory suppression.
discussions:
- discussion_id: disc_ards_metabolic_endotype_validation
  prompt: Do longitudinal immunometabolic states causally define reproducible ARDS endotypes that predict recovery and treatment response, and can metabolic resilience be measured prospectively well enough to guide therapy?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Increased Glycolytic Programming
  - pathophysiology#Impaired Mitochondrial Respiration
  rationale: The immunometabolic framework remains a hypothesis spanning experimental lung injury, sepsis and associative human omics. The cited BAL primary study measured early cross-sectional metabolites in 18 ARDS patients and eight healthy controls; it did not measure succinate or longitudinal persistence. The peripheral-blood single-cell study analyzed three ARDS patients and one healthy control, and pathway enrichment is not a direct measurement of oxidative stress or lung-cell respiration. Prospective compartment-specific functional and clinical validation is needed.
  evidence:
  - reference: PMID:42432720
    reference_title: 'Immunometabolic reprogramming and mitochondrial dysfunction in acute respiratory distress syndrome: mechanisms, metabolic resilience, and therapeutic perspectives- a narrative review.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: 'However, the actual clinical translational value of this framework faces a major practical hurdle: no prospective randomized clinical trial has yet successfully implemented real-time metabolic endotyping at the bedside.'
    explanation: The review acknowledges the absence of prospective bedside metabolic-endotyping trials.
  - reference: PMID:24289193
    reference_title: Untargeted LC-MS metabolomics of bronchoalveolar lavage fluid differentiates acute respiratory distress syndrome from health.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Ultimately, it is our goal to construct a longitudinal metabolomics strategy to more fully characterize the ARDS metabolome that will drive biomarker discovery and the identification of drug target opportunities to improve the outcome of patients with ARDS.
    explanation: Longitudinal profiling was a future goal of the BAL primary, not its design.
  - reference: PMID:37283946
    reference_title: Single-cell analysis reveals dysregulated inflammatory response in peripheral blood immunity in patients with acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: To this end, we performed scRNA-seq (10× Genomics) of peripheral blood single nuclei from one PNE-ARDS patient, two sep-ARDS patients, and one healthy volunteer (Figure 1A).
    explanation: The study contained three ARDS patients and one healthy control; blood-cell enrichment analyses cannot establish a universal lung mechanism.
datasets:
- accession: geo:GSE261463
  title: Airway Organ Tissue Equivalent (OTE) Platform for Modeling Chlorine Gas Toxicology.
  description: RNA sequencing of human airway-chip tissues after controlled chlorine gas exposure and medical-air control conditions. This experimental airway dataset does not contain an ARDS patient cohort.
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  publication: PMID:41442163
  conditions:
  - 20 ppm chlorine for 30 minutes
  - Medical air control
  notes: The GEO accession was independently resolved with the sanctioned dataset verifier. Chip replicates and sampled timepoints are not independent patients.
  evidence:
  - reference: PMID:41442163
    reference_title: A human airway-on-a-chip microphysiological system for modeling chlorine gas toxicity.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: The transcriptomic datasets generated during this study are available in NCBI’s Gene Expression Omnibus (GEO) and are accessible through GEO Series Accession Number GSE261463.
    explanation: The source deposits its airway-chip transcriptome in GEO.
experimental_models:
- name: Human airway-on-a-chip chlorine gas exposure model
  description: Human bronchial airway-on-chip with mucociliary epithelium, stromal extracellular matrix and a microvascular endothelial compartment, exposed to controlled chlorine gas. Integrated TEER, imaging and omics characterize chemical injury. This is an airway model, not an alveolar ARDS model or a clinical exposure-threshold study.
  experimental_model_type: ORGAN_ON_CHIP
  namo_type: namo:OrganOnChip
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  tissue_term:
    preferred_term: epithelium of bronchus
    term:
      id: UBERON:0002031
      label: epithelium of bronchus
  cell_types:
  - preferred_term: Bronchial epithelial cell
    term:
      id: CL:0002328
      label: bronchial epithelial cell
  - preferred_term: Pulmonary capillary endothelial cell
    term:
      id: CL:4028001
      label: pulmonary capillary endothelial cell
  conditions:
  - chlorine gas 10, 20, and 30 ppm for 10 to 30 minutes
  - medical air exposure control
  culture_system: Microfluidic airway-on-a-chip at air-liquid interface with integrated TEER electrodes and controlled gas exposure
  publication: PMID:41442163
  modeled_mechanisms:
  - target: Direct Pulmonary or Indirect Systemic Insult
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: Dose and duration jointly determine the measured barrier response. TEER recovered by 24 hours after 10 ppm for 10 minutes, whereas 30 ppm exposures caused nearly complete TEER reduction sustained through 24 hours. These data do not establish irreversible injury or recovery after every 10 ppm exposure.
    limitations: Chlorine is one specific inhalational insult and the chip is bronchial rather than alveolar, so it models the direct pulmonary insult category only for inhaled oxidant gases and not for aspiration, pneumonia, or the indirect systemic insults that cause most ARDS. Each dataset used a single donor set with independently fabricated chip replicates; these are not independent patient replicates.
    readouts:
    - name: Transepithelial electrical resistance across chlorine dose and duration
      target: Direct Pulmonary or Indirect Systemic Insult
      direction: DECREASED
      interpretation: TEER quantifies dose- and duration-dependent barrier function within the observed recovery period; it is not a proven irreversible-injury threshold.
      evidence:
      - reference: PMID:41442163
        reference_title: A human airway-on-a-chip microphysiological system for modeling chlorine gas toxicity.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        directness: DIRECT
        snippet: The lowest dose (10 ppm, 10 min) showed maximal TEER reduction at 6 h with complete recovery by 24 h (Fig. 3D).
        explanation: The lowest dose-duration condition recovered within 24 hours.
      - reference: PMID:41442163
        reference_title: A human airway-on-a-chip microphysiological system for modeling chlorine gas toxicity.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        directness: DIRECT
        snippet: All 30 ppm exposures resulted in nearly complete TEER reduction (approximately 100%) sustained through 24 h (Fig. 3F).
        explanation: The higher-concentration response persisted through the measured 24-hour interval.
    evidence:
    - reference: PMID:41442163
      reference_title: A human airway-on-a-chip microphysiological system for modeling chlorine gas toxicity.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Epithelial barrier disruption, characterized by gap formation, was evident immediately post-Cl2 exposure and persisted through 24 h
      explanation: Supports the chip as a model of a direct pulmonary chemical insult producing sustained injury.
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
  - target: Alveolar-Capillary Barrier Disruption
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: Immediate epithelial gaps and endothelial junction disruption detected at 72 hours are consistent with secondary endothelial injury. The timing does not establish the intervening signal or exclude an independent delayed chemical effect.
    limitations: The chip has no neutrophils or macrophages, so the inflammatory amplification and resolution phases that dominate barrier disruption in clinical ARDS are represented only indirectly through early epithelial-endothelial signalling. It is also airway rather than alveolar epithelium. Each dataset used a single donor set with independently fabricated chip replicates; these are not independent patient replicates.
    readouts:
    - name: Endothelial VE-cadherin junction integrity at 72 hours post-exposure
      target: Alveolar-Capillary Barrier Disruption
      direction: DECREASED
      interpretation: Delayed loss of endothelial junctional integrity is an observed readout; epithelial-to-endothelial mediation remains inferred.
      evidence:
      - reference: PMID:41442163
        reference_title: A human airway-on-a-chip microphysiological system for modeling chlorine gas toxicity.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        directness: DIRECT
        snippet: Endothelial barrier integrity, assessed at 0-, 24-, 48-, and 72-h post-exposure, showed significant disruption only at 72 h in Cl2-exposed airway-chips (0- and 72-h shown in Fig. 3H).
        explanation: The actual time-course observation supports a delayed endothelial effect.
    evidence:
    - reference: PMID:41442163
      reference_title: A human airway-on-a-chip microphysiological system for modeling chlorine gas toxicity.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: A primary constraint is the absence of innate immune system components, limiting evaluation of inflammatory responses to early epithelial/endothelial signaling that would typically recruit neutrophils and macrophages.
      explanation: The absence of innate immune cells limits the chip to early structural-cell signaling and barrier responses.
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
- name: Organoid-derived Pseudomonas pneumonia-on-a-chip (VAP) model
  description: Organoid-derived alveolar epithelial cells with AT2 and AT1-like differentiation and primary pulmonary microvascular endothelium are cultured on an alveolus chip and infected with Pseudomonas aeruginosa. Cyclic strain of 5% versus 10% at 0.25 Hz tests a controlled mechanical perturbation. Chip strain is not a uniquely equivalent clinical tidal-volume dose.
  experimental_model_type: ORGAN_ON_CHIP
  namo_type: namo:OrganOnChip
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  tissue_term:
    preferred_term: alveolus of lung
    term:
      id: UBERON:0002299
      label: alveolus of lung
  cell_types:
  - preferred_term: Pulmonary alveolar type 2 cell
    term:
      id: CL:0002063
      label: pulmonary alveolar type 2 cell
  - preferred_term: Pulmonary alveolar type 1 cell
    term:
      id: CL:0002062
      label: pulmonary alveolar type 1 cell
  - preferred_term: Pulmonary capillary endothelial cell
    term:
      id: CL:4028001
      label: pulmonary capillary endothelial cell
  conditions:
  - physiological cyclic strain (5%, 0.25 Hz)
  - hyperphysiological cyclic strain (10%, 0.25 Hz)
  - Pseudomonas aeruginosa PAO1 infection
  cell_source: Human alveolar organoid-derived epithelial cells and primary pulmonary microvascular endothelial cells
  culture_system: Alveolus-on-a-chip with air-liquid interface, vascular flow, and controlled cyclic strain
  publication: PMID:41252215
  modeled_mechanisms:
  - target: Ventilator-Induced Lung Injury
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: Increasing chip strain raised baseline apparent permeability slightly and, after infection, increased vascular bacterial counts and permeability. This demonstrates a mechanical-infectious interaction in this cell system without establishing the size of a clinical ventilation effect.
    limitations: The uniform chip deformation does not reproduce regional overdistension and recruitment-derecruitment in an injured lung. There are no seeded immune cells. Infection outcomes were assessed at 12 hours; baseline permeability was measured before infection. The organoid system is not a clinical ARDS cohort.
    readouts:
    - name: Apparent permeability under hyperphysiological versus physiological strain
      target: Ventilator-Induced Lung Injury
      direction: INCREASED
      interpretation: Strain-dependent permeability increase is the barrier readout for stretch injury.
      evidence:
      - reference: PMID:41252215
        reference_title: Mechanical strain exacerbates Pseudomonas infection in an organoid-based pneumonia-on-a-chip model.
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: Yet, Papp was slightly increased in 10% stretched ODAECs, suggesting barrier impairment by hyperphysiological stretch.
        explanation: The source describes the baseline permeability increase as slight.
        directness: DIRECT
        quote_role: PRIMARY_RESULT
    - name: Bacterial translocation to the vascular channel under increased strain
      target: Ventilator-Induced Lung Injury
      direction: INCREASED
      interpretation: Higher vascular-channel colony counts under greater strain quantify the strain-infection interaction.
      evidence:
      - reference: PMID:41252215
        reference_title: Mechanical strain exacerbates Pseudomonas infection in an organoid-based pneumonia-on-a-chip model.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        directness: DIRECT
        snippet: CFUs in the vascular channel and Papp were higher in 10% compared with 5% stretched ODAEC chips (Figure 1, H and I, and Supplemental Figure 4, A and B), indicating that mechanical strain exacerbates Pseudomonas infection in the alveolus.
        explanation: Vascular bacterial counts and permeability increased under greater stretch; this does not establish increased apical bacterial growth.
    evidence:
    - reference: PMID:41252215
      reference_title: Mechanical strain exacerbates Pseudomonas infection in an organoid-based pneumonia-on-a-chip model.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: We hereby present what we believe to be the first functional Pseudomonas POC and VAP-on-a-chip model that replicates key features of disease, including enhanced mechanical strain.
      explanation: Supports the chip as a model of ventilator-associated infectious lung injury, the clinical setting this node describes.
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
  - target: Alveolar-Capillary Barrier Disruption
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: Infection plus greater chip strain increased apparent permeability and vascular-channel bacterial counts. These readouts model aspects of barrier dysfunction without reproducing the full syndrome.
    limitations: Barrier failure is measured as apparent permeability and bacterial translocation over 12 hours, without the protein-rich alveolar flooding, coagulation, or leukocyte transmigration that accompany the lesion clinically.
    readouts:
    - name: Barrier disruption with bacterial translocation
      target: Alveolar-Capillary Barrier Disruption
      direction: INCREASED
      interpretation: Higher vascular-channel bacterial counts are consistent with increased translocation across the experimental barrier.
      evidence:
      - reference: PMID:41252215
        reference_title: Mechanical strain exacerbates Pseudomonas infection in an organoid-based pneumonia-on-a-chip model.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        directness: DIRECT
        snippet: CFUs in the vascular channel and Papp were higher in 10% compared with 5% stretched ODAEC chips (Figure 1, H and I, and Supplemental Figure 4, A and B), indicating that mechanical strain exacerbates Pseudomonas infection in the alveolus.
        explanation: Vascular bacterial counts and permeability increased under greater stretch; this does not establish increased apical bacterial growth.
    evidence:
    - reference: PMID:41252215
      reference_title: Mechanical strain exacerbates Pseudomonas infection in an organoid-based pneumonia-on-a-chip model.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: We hereby present what we believe to be the first functional Pseudomonas POC and VAP-on-a-chip model that replicates key features of disease, including enhanced mechanical strain.
      explanation: Supports the chip as informative for the alveolar-capillary barrier lesion under combined infectious and mechanical insult.
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
  - target: Pulmonary Cytokine and Chemokine Release
    relationship: PERTURBS
    fidelity: MODERATE
    description: >-
      Increasing cyclic strain from 5% to 10% modulates IL-6 and IL-8 release in the infected chip. Cytokine
      levels decrease under greater strain despite increased barrier injury.
    limitations: >-
      This comparison measures cytokine output in an epithelial-endothelial chip without seeded immune cells
      at 12 hours after infection. It does not establish a clinical anti-inflammatory benefit of greater ventilation
      strain.
    readouts:
    - name: IL-6 and IL-8 release under greater strain
      direction: DECREASED
      interpretation: Lower cytokine levels at 10% than at 5% strain prevent interpreting barrier injury as uniformly stronger inflammatory output.
      evidence:
      - reference: PMID:41252215
        reference_title: Mechanical strain exacerbates Pseudomonas infection in an organoid-based pneumonia-on-a-chip model.
        supports: SUPPORT
        evidence_source: IN_VITRO
        quote_role: PRIMARY_RESULT
        directness: DIRECT
        snippet: Notably, lower cytokine levels were detected under 10% compared with 5% stretch, suggesting that increased strain modulates immune reactivity.
        explanation: Greater strain reduced these measured cytokine outputs despite greater barrier injury.
      target: Pulmonary Cytokine and Chemokine Release
    evidence:
    - reference: PMID:41252215
      reference_title: Mechanical strain exacerbates Pseudomonas infection in an organoid-based pneumonia-on-a-chip model.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Notably, lower cytokine levels were detected under 10% compared with 5% stretch, suggesting that increased strain modulates immune reactivity.
      explanation: Greater strain reduced these measured cytokine outputs despite greater barrier injury.
notes: Adult care recommendations and trial outcomes are not automatically applicable to children. Clinical manifestations vary with trigger, severity, support and recovery phase; no disease-wide frequency bands are inferred from selected cohorts. Survivor weakness, exercise limitation and neuropsychological morbidity may reflect critical illness, treatment and premorbid function as well as ARDS. StatPearls PMID:28613773 (NBK436002, updated January 31, 2024) was recovered through the NCBI Bookshelf URL record; newer ATS, ESICM and PALICC-2 sources govern treatment recommendations.
prevalence:
- population: Adult ICU admissions in the LUNG SAFE convenience sample of 459 ICUs in 50 countries during four winter weeks in 2014
  measure_type: PERIOD_PREVALENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 10400.0
  notes: 3022 of 29144 admitted patients fulfilled ARDS criteria. This ICU period prevalence is not annual population incidence and may reflect seasonal and participating-center selection.
  evidence:
  - reference: PMID:26903337
    reference_title: Epidemiology, Patterns of Care, and Mortality for Patients With Acute Respiratory Distress Syndrome in Intensive Care Units in 50 Countries.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: 'RESULTS: Of 29,144 patients admitted to participating ICUs, 3022 (10.4%) fulfilled ARDS criteria.'
    explanation: The prospective multicenter convenience sample provides a denominator-specific estimate.
genetic:
- name: 12p13.2 susceptibility locus (rs7967111)
  association: Population association with ARDS susceptibility; not a Mendelian cause or clinical diagnostic test
  notes: In 1250 European-ancestry cases and 1583 controls, the primary GWAS meta-analysis was just above conventional genome-wide significance; a sensitivity model additionally adjusting for cohort and pneumonia produced OR 1.38 (95% CI 1.23–1.55), P=2.15×10−8. The trans-ancestry analysis did not identify a genome-wide significant locus. BORCS5 and DUSP16 are nearby annotated candidate genes; eQTL, expression and in-silico evidence do not resolve a causal gene or molecular route. The African-American analysis included 387 cases and 387 controls. Mendelian-randomization treatment associations do not establish clinical efficacy.
  evidence:
  - reference: PMID:34032881
    reference_title: Integrative omics provide biological and clinical insights into acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: 'METHODS: Meta-analyses of ARDS genome-wide association studies were performed with 1250 cases and 1583 controls in Europeans, and 387 cases and 387 controls in African Americans.'
    explanation: The primary study states ancestry-specific GWAS sample sizes.
  - reference: PMID:34032881
    reference_title: Integrative omics provide biological and clinical insights into acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Intriguingly, rs7967111 exceeded genome-wide significance (P < 5 × 10–8), with OR of 1.38 (P = 2.15 × 10–8; Table 1) after adjusting for potential confounders.
    explanation: The stronger association comes from the sensitivity analysis.
  - reference: PMID:34032881
    reference_title: Integrative omics provide biological and clinical insights into acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Unexpectedly, no loci achieved genome-wide significance, even at the empirical threshold of P < 1 × 10−6 (Fig. E5).
    explanation: Cross-ancestry inference remains limited.
references:
- reference: PMID:37487152
  title: A New Global Definition of Acute Respiratory Distress Syndrome.
- reference: PMID:36661420
  title: Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).
- reference: PMID:24853585
  title: 'Subphenotypes in acute respiratory distress syndrome: latent class analysis of data from two randomised controlled trials.'
- reference: PMID:42432720
  title: 'Immunometabolic reprogramming and mitochondrial dysfunction in acute respiratory distress syndrome: mechanisms, metabolic resilience, and therapeutic perspectives- a narrative review.'
- reference: PMID:39866839
  title: 'Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies.'
- reference: PMID:30872586
  title: Acute respiratory distress syndrome.
- reference: PMID:21470008
  title: Functional disability 5 years after acute respiratory distress syndrome.
- reference: PMID:26903337
  title: Epidemiology, Patterns of Care, and Mortality for Patients With Acute Respiratory Distress Syndrome in Intensive Care Units in 50 Countries.
- reference: PMID:37326646
  title: 'ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.'
- reference: PMID:29722341
  title: Halogen Inhalation-Induced Lung Injury and Acute Respiratory Distress Syndrome.
- reference: PMID:20601629
  title: 'Chlorine gas inhalation: human clinical evidence of toxicity and experience in animal models.'
- reference: PMID:31068086
  title: 'Preclinical and clinical studies of smoke-inhalation-induced acute lung injury: update on both pathogenesis and innovative therapy.'
- reference: PMID:24289193
  title: Untargeted LC-MS metabolomics of bronchoalveolar lavage fluid differentiates acute respiratory distress syndrome from health.
- reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK436002/
  title: Acute Respiratory Distress Syndrome - StatPearls - NCBI Bookshelf
  tags:
  - StatPearls
- reference: PMID:10793162
  title: Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome.
- reference: PMID:38032683
  title: 'An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.'
- reference: PMID:16714767
  title: Comparison of two fluid-management strategies in acute lung injury.
- reference: PMID:37283946
  title: Single-cell analysis reveals dysregulated inflammatory response in peripheral blood immunity in patients with acute respiratory distress syndrome.
- reference: PMID:41442163
  title: A human airway-on-a-chip microphysiological system for modeling chlorine gas toxicity.
- reference: PMID:41252215
  title: Mechanical strain exacerbates Pseudomonas infection in an organoid-based pneumonia-on-a-chip model.
- reference: PMID:34032881
  title: Integrative omics provide biological and clinical insights into acute respiratory distress syndrome.
- reference: PMID:23688302
  title: Prone positioning in severe acute respiratory distress syndrome.
- reference: clinicaltrials:NCT00527813
  title: Effect of Prone Positioning on Mortality in Patients With Severe and Persistent Acute Respiratory Distress Syndrome
- reference: clinicaltrials:NCT00281268
  title: Fluids and Catheters Treatment Trial (FACTT) - ARDS Clinical Research Network
clinical_trials:
- name: clinicaltrials:NCT00527813
  description: PROSEVA randomized 466 adults with severe ARDS to prolonged prone sessions or supine care with protective ventilation. The trial reported lower 28-day and 90-day mortality in the prone group; its protocol and eligibility are distinct from pediatric guidance.
  evidence:
  - reference: PMID:23688302
    reference_title: Prone positioning in severe acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: In this multicenter, prospective, randomized, controlled trial, we randomly assigned 466 patients with severe ARDS to undergo prone-positioning sessions of at least 16 hours or to be left in the supine position.
    explanation: The primary trial specifies the adult intervention, comparator and study population.
  - reference: PMID:23688302
    reference_title: Prone positioning in severe acute respiratory distress syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: The 28-day mortality was 16.0% in the prone group and 32.8% in the supine group (P<0.001).
    explanation: The primary publication reports the trial outcome, rather than relying on the registry protocol for efficacy.
  status: COMPLETED
  phase: NOT_APPLICABLE
  notes: Registry status and phase checked against the live ClinicalTrials.gov API on 2026-09-21. Published trial results provide the outcome evidence.
- name: clinicaltrials:NCT00281268
  description: FACTT compared conservative and liberal fluid strategies for seven days in 1000 patients with acute lung injury. Ventilator-free days and lung physiology improved with conservative management, without a statistically significant 60-day mortality difference.
  evidence:
  - reference: PMID:16714767
    reference_title: Comparison of two fluid-management strategies in acute lung injury.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: In a randomized study, we compared a conservative and a liberal strategy of fluid management using explicit protocols applied for seven days in 1000 patients with acute lung injury.
    explanation: The primary trial defines the randomized comparison.
  - reference: PMID:16714767
    reference_title: Comparison of two fluid-management strategies in acute lung injury.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Although there was no significant difference in the primary outcome of 60-day mortality, the conservative strategy of fluid management improved lung function and shortened the duration of mechanical ventilation and intensive care without increasing nonpulmonary-organ failures.
    explanation: Efficacy is tied to the published endpoints.
  status: COMPLETED
  phase: PHASE_III
  notes: Registry status and phase checked against the live ClinicalTrials.gov API on 2026-09-21. Published trial results provide the outcome evidence.
- name: clinicaltrials:NCT02595060
  phase: PHASE_II
  status: COMPLETED
  description: >-
    GI-HOPE, a randomised, double-blind, placebo-controlled phase 2a trial of
    inhaled molgramostim (150 or 450 micrograms daily for 3 days) in
    pneumonia-related ARDS. Published results report safety and favourable
    secondary outcomes at high dose, with no difference in the composite primary
    GI-HOPE score.
  target_phenotypes:
  - preferred_term: Respiratory failure
    term:
      id: HP:0002878
      label: Respiratory failure
  evidence:
  - reference: clinicaltrials:NCT02595060
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This trial evaluates efficacy and safety of inhaled molgramostim (rhGM-CSF)
      in 45 patients with pneumonia associated acute respiratory distress
      syndrome (ARDS).
    explanation: >-
      The registration record establishes the trial's population and
      intervention for ARDS.

📚

References & Deep Research

References

PMID:37487152

A New Global Definition of Acute Respiratory Distress Syndrome.

No top-level findings curated for this source.

PMID:36661420

Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).

No top-level findings curated for this source.

PMID:24853585

Subphenotypes in acute respiratory distress syndrome: latent class analysis of data from two randomised controlled trials.

No top-level findings curated for this source.

PMID:42432720

Immunometabolic reprogramming and mitochondrial dysfunction in acute respiratory distress syndrome: mechanisms, metabolic resilience, and therapeutic perspectives- a narrative review.

No top-level findings curated for this source.

PMID:39866839

Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies.

No top-level findings curated for this source.

PMID:30872586

Acute respiratory distress syndrome.

No top-level findings curated for this source.

PMID:21470008

Functional disability 5 years after acute respiratory distress syndrome.

No top-level findings curated for this source.

PMID:26903337

Epidemiology, Patterns of Care, and Mortality for Patients With Acute Respiratory Distress Syndrome in Intensive Care Units in 50 Countries.

No top-level findings curated for this source.

PMID:37326646

ESICM guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies.

No top-level findings curated for this source.

PMID:29722341

Halogen Inhalation-Induced Lung Injury and Acute Respiratory Distress Syndrome.

No top-level findings curated for this source.

PMID:20601629

Chlorine gas inhalation: human clinical evidence of toxicity and experience in animal models.

No top-level findings curated for this source.

PMID:31068086

Preclinical and clinical studies of smoke-inhalation-induced acute lung injury: update on both pathogenesis and innovative therapy.

No top-level findings curated for this source.

PMID:24289193

Untargeted LC-MS metabolomics of bronchoalveolar lavage fluid differentiates acute respiratory distress syndrome from health.

No top-level findings curated for this source.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK436002/

Acute Respiratory Distress Syndrome - StatPearls - NCBI Bookshelf

No top-level findings curated for this source.

PMID:10793162

Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome.

No top-level findings curated for this source.

PMID:38032683

An Update on Management of Adult Patients with Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline.

No top-level findings curated for this source.

PMID:16714767

Comparison of two fluid-management strategies in acute lung injury.

No top-level findings curated for this source.

PMID:37283946

Single-cell analysis reveals dysregulated inflammatory response in peripheral blood immunity in patients with acute respiratory distress syndrome.

No top-level findings curated for this source.

PMID:41442163

A human airway-on-a-chip microphysiological system for modeling chlorine gas toxicity.

No top-level findings curated for this source.

PMID:41252215

Mechanical strain exacerbates Pseudomonas infection in an organoid-based pneumonia-on-a-chip model.

No top-level findings curated for this source.

PMID:34032881

Integrative omics provide biological and clinical insights into acute respiratory distress syndrome.

No top-level findings curated for this source.

PMID:23688302

Prone positioning in severe acute respiratory distress syndrome.

No top-level findings curated for this source.

clinicaltrials:NCT00527813

Effect of Prone Positioning on Mortality in Patients With Severe and Persistent Acute Respiratory Distress Syndrome

No top-level findings curated for this source.

clinicaltrials:NCT00281268

Fluids and Catheters Treatment Trial (FACTT) - ARDS Clinical Research Network

No top-level findings curated for this source.

Deep Research

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (2)

Review ARDS mechanisms, adult and pediatric care, and experimental evidence · 2026-09-21T06:46:17Z · View source

Reviewed the entire prior entry, matching deep-research reports, primary clinical and mechanistic sources, adult ATS and ESICM guidelines, and pediatric PALICC-2 guidance. Replaced bundled nodes with 21 atomic mechanisms; distinguished compartment-specific observations and hypotheses from clinical causal evidence; removed unsupported human succinate and generalized metabolic-endotype claims. Expanded clinical manifestations and recovery outcomes without unsupported population frequencies. Separated adult and pediatric diagnostic and treatment criteria and reconciled differing recommendation scopes. Audited both airway-chip models against full primary texts and supplementary methods, with independent source and integration peer reviews. Added a verified GEO transcriptomic dataset and PROSEVA/FACTT trial records with published efficacy results. Repaired obsolete node-class examples. Sanctioned reference and dataset fetches generated all new caches; no manual reference-cache edits or frozen dataset-accessions access. Schema, live ontology terms, 179 exact snippets, dataset verification, history validation, all 20 repository checks including whole-KB node-class verification, and pre-commit passed.

Create Acute Respiratory Distress Syndrome entry · 2026-08-08T19:31:23Z · View source

Created a de novo ARDS entry from Asta deep research and targeted review of the issue-nominated narrative review (PMID:42432720), the 2023 global ARDS definition, the 2024 ATS management guideline, pivotal supportive-care trials, a broad mechanistic review, a pediatric review, and human single-cell evidence. Modeled established acute alveolar-capillary injury as the canonical mechanism and immunometabolic reprogramming/mitochondrial dysfunction as an emerging modifier with an explicit knowledge gap, rather than implying that the latter is universal or clinically actionable. Kept the causal chain at the disorder-entry level: the existing epithelial barrier and mitochondrial modules address different biological contexts, and one ARDS entry did not establish the recurrence needed for a new shared module. Added adult and pediatric subtypes, phased progression, phenotypes, diagnostic criteria, investigational biochemical markers, and evidence- graded supportive treatments. No dataset accession was added because a stable accession could not be verified from the cited human omics report.

Asta ▸

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of Acute Respiratory Distress Syndrome. Core disease mechanisms, molecular an...

Asta Scientific Corpus Retrieval 20 citations 2026-08-08T12:10:49.945606

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of Acute Respiratory Distress Syndrome. Core disease mechanisms, molecular an...

This report is retrieval-only and is generated directly from Asta results.

Papers retrieved: 20
Snippets retrieved: 20

Relevant Papers

[1] Lung regeneration: diverse cell types and the therapeutic potential

Authors: Yutian Chen, Zhen Li, Gaili Ji, Shaochi Wang, Chunheng Mo et al.
Year: 2024
Venue: MedComm
URL: https://www.semanticscholar.org/paper/0fbe00de4b129b66ffcc63fd4298d45dc0352a8c
DOI: 10.1002/mco2.494
PMID: 38405059
PMCID: 10885188
Citations: 30
Summary: A review of the molecular and cellular mechanisms of lung regeneration, drug development, and clinical trials provides a reference for further research on the molecular and cellular mechanisms of lung regeneration, drug development, and clinical trials.
Evidence snippets:
Snippet 1 (score: 0.502) > Abstract Lung tissue has a certain regenerative ability and triggers repair procedures after injury. Under controllable conditions, lung tissue can restore normal structure and function. Disruptions in this process can lead to respiratory system failure and even death, causing substantial medical burden. The main types of respiratory diseases are chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and acute respiratory distress syndrome (ARDS). Multiple cells, such as lung epithelial cells, endothelial cells, fibroblasts, and immune cells, are involved in regulating the repair process after lung injury. Although the mechanism that regulates the process of lung repair has not been fully elucidated, clinical trials targeting different cells and signaling pathways have achieved some therapeutic effects in different respiratory diseases. In this review, we provide an overview of the cell type involved in the process of lung regeneration and repair, research models, and summarize molecular mechanisms involved in the regulation of lung regeneration and fibrosis. Moreover, we discuss the current clinical trials of stem cell therapy and pharmacological strategies for COPD, IPF, and ARDS treatment. This review provides a reference for further research on the molecular and cellular mechanisms of lung regeneration, drug development, and clinical trials.

[2] Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies

Authors: Rongli Xie, Dan Tan, Boke Liu, Guohui Xiao, Fangchen Gong et al.
Year: 2025
Venue: MedComm
URL: https://www.semanticscholar.org/paper/97d3e572d53d14edaa3fdb78fe49b51047c7aabc
DOI: 10.1002/mco2.70074
PMID: 39866839
PMCID: 11769712
Citations: 33
Influential citations: 1
Summary: The pathogenesis and treatment methods of affected organs, including 2019 coronavirus disease (COVID‐19)‐related pneumonia, drowning, trauma, blood transfusion, severe acute pancreatitis, and sepsis are discussed.
Evidence snippets:
Snippet 1 (score: 0.491) > Acute respiratory distress syndrome (ARDS) is a clinical syndrome of acute hypoxic respiratory failure caused by diffuse lung inflammation and edema. The mortality rate is high in ARDS patients and is related to the severity of the patient's condition. 1 ARDS can be precipitated by intrapulmonary factors (pneumonia, aspiration, etc.) or extrapulmonary factors (severe acute pancreatitis [SAP], sepsis, trauma, etc.), which can lead to severe hypoxemia, decreased lung compliance, increased arteriovenous shunts, and increased physiological dead space. 4][5] Each revision of the definition, in response to new research findings and clinical concepts, is intended to provide a definition that consistently and accurately identifies patients. The pathophysiology of ARDS is complex and involves the activation and dysregulation of multiple overlapping and interacting pathways of systemic inflammation and coagulation, including the respiratory, circulatory, and immune systems. In general, the treatment of inflammatory injuries is a coordinated process that involves the downregulation of proinflammatory pathways and the upregulation of anti-inflammatory pathways. Owing to differences in etiology and inducement, there is heterogeneity in the clinical syndrome. In recent years, foundation medicine, radiology, immunology, and other disciplines have increasingly recognized and incorporated phenotype recognition. > ARDS is a highly heterogeneous disease with different etiologies, different inflammatory phenotypes and different histomorphologic characteristics, which leads to relatively slow progress in the treatment of ARDS. Individualized medical approaches to the etiology of ARDS can improve the identification of ARDS phenotypes, which should contribute to a better understanding of its pathophysiological mechanisms and differences between patients. In this review, we discuss the current understanding of the structural features and changes in the lung function of ARDS patients. We further discuss the pathogenesis and treatment methods of affected organs according to their different causes.

[3] A practical approach to adult acute respiratory distress syndrome

Authors: C. Manthous
Year: 2010
Venue: Indian Journal of Critical Care Medicine : Peer-reviewed, Official Publication of Indian Society of Critical Care Medicine
URL: https://www.semanticscholar.org/paper/affa7b3f3d93c8318e50fb89eabdce8c86696a23
DOI: 10.4103/0972-5229.76084
PMID: 21572751
PMCID: 3085221
Citations: 4
Summary: The clinical features and how pathophysiology informs the evidence-based management of ARDS are reviewed, which shows how the disease has carried a very high mortality.
Evidence snippets:
Snippet 1 (score: 0.489) > Acute respiratory distress syndrome (ARDS) is a common disease encountered in hospitalized adult patients that, historically, has carried a very high mortality. This article reviews the clinical features and how pathophysiology informs the evidence-based management of ARDS.

[4] Genetic and Multi‐Omics Insights Into Monocyte Pantothenate‐Mediated Protection in Acute Respiratory Distress Syndrome

Authors: Yang Wang, Hongyu Sun, Fengying Liang, Y. Qian, Yuanyuan Wang et al.
Year: 2025
Venue: Journal of Cellular and Molecular Medicine
URL: https://www.semanticscholar.org/paper/475776c4266e5af912ab92f23bff48fd16d5fd2c
DOI: 10.1111/jcmm.70812
PMID: 41059665
PMCID: 12505201
Citations: 4
Summary: This study uses Mendelian randomisation, multi‐omics and machine learning approaches to provide novel insights into the pathogenesis of ARDS and its potential therapeutic strategies targeting monocyte metabolism and function.
Evidence snippets:
Snippet 1 (score: 0.467) > Acute respiratory distress syndrome (ARDS) is a severe and life-threatening condition characterised by rapid onset of widespread inflammation and increased permeability of the alveolar-capillary barrier, leading to impaired gas exchange and respiratory failure [1,2]. Despite advances in supportive care, including lung-protective ventilation strategies and neuromuscular blockade, the mortality rate for ARDS remains high, ranging from 30% to 45% [3]. This persistent mortality burden highlights the critical need for a deeper understanding of the underlying pathophysiology to inform the development of more effective therapeutic interventions. > Emerging evidence suggests that metabolic factors may play a crucial role in the pathogenesis of ARDS, though the precise mechanisms remain incompletely understood [4,5]. Alterations in cellular metabolism, including impaired energy production, oxidative stress and dysregulated signalling pathways, have been implicated in the initiation and progression of ARDS [6,7]. Furthermore, metabolic disturbances, such as hyperglycemia, dyslipidaemia and mitochondrial dysfunction, have been associated with worse clinical outcomes in ARDS patients [8][9][10][11]. However, the specific metabolic pathways and mediators involved in the development and resolution of ARDS remain poorly defined [12]. Continued research is necessary to elucidate this complex interplay between metabolism and the pathogenesis of ARDS, which may lead to the identification of novel therapeutic targets and the development of more personalised treatment strategies. > In this study, we aim to investigate the causal relationship between plasma metabolites, immune cell profiles and the risk of ARDS using Mendelian randomisation (MR) analysis. We integrate single-cell sequencing and transcriptomic data to explore the potential mechanisms underlying these associations. Additionally, we employ machine learning approaches to evaluate the predictive performance of a comprehensive set of risk factors for ARDS development. By elucidating the causal pathways and underlying biological mechanisms linking these metabolic and immune factors to ARDS, our research is expected to provide important insights into the pathogenesis of this devastating syndrome.

[5] Obesity promotes ARDS by modulating ceramide transfer protein-ceramide pathway and exacerbating oxidative stress/apoptosis in alveolar macrophages

Authors: Yichan Ao, Jingyue Ma, Xiangyu Hou, Hongbin Li, Zhiqiao Wang et al.
Year: 2025
Venue: Cellular and Molecular Life Sciences: CMLS
URL: https://www.semanticscholar.org/paper/23ee5a5309e9b3ceefad8175244fc04a35dbb765
DOI: 10.1007/s00018-025-05706-9
PMID: 40537702
PMCID: 12179041
Citations: 4
Summary: In vivo and in vitro studies indicated that obesity-induced downregulation of CERT reduced Cer transport, increased Cer levels, and aggravated ARDS through elevated ROS production and apoptosis, highlighting CERT may represent a promising therapeutic target for managing ARDS in individuals with obesity.
Evidence snippets:
Snippet 1 (score: 0.461) > Acute respiratory distress syndrome (ARDS) is a common critical condition characterized by acute respiratory distress and progressive hypoxemia, with its pathogenesis not yet fully understood. Approximately 10.4% of patients in intensive care units (ICUs) develop ARDS, a condition associated with high morbidity and mortality [1]. Obesity, a systemic chronic low-grade inflammatory state, is a wellestablished risk factor for various respiratory diseases [2]. Notably, obesity has been identified as an independent risk factor for the development of ARDS in ICU patients, with the risk nearly doubling in obese individuals [3][4][5]. Despite growing evidence that obesity increases susceptibility to ARDS and worsens disease severity, the mechanisms by which obesity contributes to the onset and progression of ARDS remain poorly understood. Therefore, animal models and basic research that reflect clinical characteristics are crucial for elucidating the specific mechanisms linking obesity and ARDS, potentially laying the groundwork for improving ARDS treatment outcomes [6][7][8][9]. > Multiple studies have demonstrated that "omics" strategies significantly contribute to understanding the pathophysiological pathways underlying diseases. Proteins, as the primary executors of biological functions, represent the final products of genetic information, while metabolites are essential components of cellular processes, participating in enzyme-catalyzed reactions critical for cell function. Quantitative proteomics allows for detailed characterization of pathogenic biochemical processes by measuring protein levels and their regulatory chemical modifications [10]. Additionally, metabolomics provides a wealth of information that strongly predicts phenotypic outcomes [11]. In recent years, these strategies have become valuable tools for exploring the etiology and mechanisms of obesity-related diseases [12][13][14][15]. In acute lung injury (ALI) or ARDS, various candidate biomarkers have been identified through the assessment of protein expression in lung tissues [16][17][18]. Moreover, integrated proteomics and metabolomics analyses have facilitated the identification of mechanisms relevant to drugs aimed at preventing or ameliorating ALI/ARDS [19]. However, specific changes in the protein and metabolite profiles associated with ARDS in HFD mice have yet to be characterized.

[6] Evolution of multiple omics approaches to define pathophysiology of pediatric acute respiratory distress syndrome

Authors: Jane E Whitney, In‐Hee Lee, Ji-Won Lee, S. Kong
Year: 2022
Venue: eLife
URL: https://www.semanticscholar.org/paper/6d82effd3fff4275e47d52ecd0b92ee996e2ac37
DOI: 10.7554/eLife.77405
PMID: 35913450
PMCID: 9342956
Citations: 5
Summary: Novel profiling methods such as scRNA-seq, which permits more comprehensive, unbiased evaluation of pathophysiological mechanisms across tissue and cell types, should be employed to investigate the molecular mechanisms of PRDS toward the goal of identifying targeted therapies.
Evidence snippets:
Snippet 1 (score: 0.453) > Pediatric acute respiratory distress syndrome (PARDS), though both common and deadly in critically ill children, lacks targeted therapies. The development of effective pharmacotherapies has been limited, in part, by lack of clarity about the pathobiology of pediatric ARDS. Epithelial lung injury, vascular endothelial activation, and systemic immune activation are putative drivers of this complex disease process. Prior studies have used either hypothesis-driven (e.g., candidate genes and proteins, in vitro investigations) or unbiased (e.g., genome-wide association, transcriptomic, metabolomic) approaches to predict clinical outcomes and to define subphenotypes. Advances in multiple omics technologies, including genomics, transcriptomics, proteomics, and metabolomics, have permitted more comprehensive investigation of PARDS pathobiology. However, omics studies have been limited in children compared to adults, and analyses across multiple tissue types are lacking. Here, we synthesized existing literature on the molecular mechanism of PARDS, summarized our interrogation of publicly available genomic databases to determine the association of candidate genes with PARDS phenotypes across multiple tissues and cell types, and integrated recent studies that used single-cell RNA sequencing (scRNA-seq). We conclude that novel profiling methods such as scRNA-seq, which permits more comprehensive, unbiased evaluation of pathophysiological mechanisms across tissue and cell types, should be employed to investigate the molecular mechanisms of PRDS toward the goal of identifying targeted therapies.

[7] Classic Signaling Pathways in Alveolar Injury and Repair Involved in Sepsis-Induced ALI/ARDS: New Research Progress and Prospect

Authors: Wenli Li, Duo Li, Yuansen Chen, Halidan Abudou, Haiwang Wang et al.
Year: 2022
Venue: Disease Markers
URL: https://www.semanticscholar.org/paper/4268a462890d48f33ce3908d40f66ecb9f3dd801
DOI: 10.1155/2022/6362344
PMID: 35726235
PMCID: 9206211
Citations: 127
Influential citations: 3
Summary: The signaling pathways related to alveolar injury and repair in sepsis-induced ALI/ARDS and their latest research progress include the NF-κB, JAK2/STAT3, mitogen-activated protein kinase (MAPK), mTOR, and Notch signaling pathways.
Evidence snippets:
Snippet 1 (score: 0.449) > Sepsis is a common critical clinical disease with high mortality that can cause approximately 10 million deaths worldwide each year. Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) is a common clinical complication of sepsis, which occurs primarily as diffuse alveolar injury, hypoxemia, and respiratory distress. The mortality rate of ALI/ARDS is as high as 30%-40%, which greatly endangers human health. Due to the unclear pathogenesis of ALI/ARDS, its treatment is still a worldwide problem. At present, clinical treatment mainly relies on lung-protective ventilation, prone position ventilation, and fluid management. However, there is a lack of effective and specific treatment measures. In recent years, domestic and foreign scholars have committed to basic research on ALI/ARDS, trying to further clarify its pathogenesis and find new targets and methods for the treatment of ALI/ARDS. In this review, we summarize the signaling pathways related to alveolar injury and repair in sepsis-induced ALI/ARDS and their latest research progress. They include the NF-κB, JAK2/STAT3, mitogen-activated protein kinase (MAPK), mTOR, and Notch signaling pathways. Understanding the molecular mechanisms of these signaling pathways in sepsis-induced ALI/ARDS may provide new targets and ideas for the clinical treatment of this disease.

[8] Acute Respiratory Failure: Pathophysiological Basis From A Multidisciplinary Clinical Approach

Authors: R. Castillo
Year: 2015
Venue: The Open Respiratory Medicine Journal
URL: https://www.semanticscholar.org/paper/f4537439b4e55e4efb383f03c5c3f561d9fcedf8
DOI: 10.2174/1874306401509010081
PMID: 26312098
PMCID: 4541451
Citations: 1
Summary: The evidence strongly supports its use in patients with chronic obstructive pulmonary disease (COPD) exacerbation, patients with acute cardiogenic pulmonary edema and immunosuppressed patients, and patients with hypoxemic and hypercapnic failure.
Evidence snippets:
Snippet 1 (score: 0.443) > Acute Respiratory Failure: Pathophysiological Basis from a Multidisciplinary Clinical Approach > Acute Respiratory Failure (ARF) is a syndrome characterized by the inability of the respiratory system to maintain adequate arterial O2 and CO2 levels according to the demands of cellular metabolism. ARF may be caused by the failure of the exchanger, lung, organ or pump, or failure of the respiratory muscles. ARF can be classified by the dysfunctional element or the evolution time when the condition occurs. > Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is the most important cause of adults hipoxemic respiratory failure, which results from multiple clinical factors such as sepsis or trauma [1]. Although the main cause was clinically resolved, the mechanism that determines the progression may persist and lead to complications. > However, It is demonstrated that the clinical causes of respiratory failure increase the intensive care units (ICU) stay, the sanitary cost and the global mortality [2]. For this reason, multidisciplinary and pathophysiological focus on respiratory failure is necessary for the management of these patients. > The application of non-invasive mechanical ventilation (NIMV) has acquired major relevance in the last few years in the management of ARF, in patients with hypoxemic and hypercapnic failure. The main advantage of NIMV compared to invasive mechanical ventilation is that it can be used earlier outside ICU. The evidence strongly supports its use in patients with chronic obstructive pulmonary disease (COPD) exacerbation, patients with acute cardiogenic pulmonary edema and immunosuppressed patients. > This issue is focused on the mechanism associated with ARF, some clinical syndromes, and the pathophysiological bases for the use of ventilatory strategies, with a multidisciplinary approach.

[9] Messenger RNA sequencing reveals similar mechanisms between neonatal and acute respiratory distress syndrome

Authors: H. Mei, Yuheng Zhang, Chun-zhi Liu, Yayu Zhang, Chunli Liu et al.
Year: 2017
Venue: Molecular Medicine Reports
URL: https://www.semanticscholar.org/paper/663e1561706e158cfc150ce2f69d0b6a184888e4
DOI: 10.3892/mmr.2017.7891
PMID: 29115600
PMCID: 5780146
Citations: 8
Summary: Using peripheral blood obtained from mature infants with and without NRDS and in tandem with mRNA sequencing, the present study identified that, while cell cycle regulation and alveolar surfactants serve a role in deterring the further onset of NRDS, innate and pathogen-induced responses of the immune system are among the most important factors in the pathology.
Evidence snippets:
Snippet 1 (score: 0.441) > Neonatal respiratory distress syndrome (NRDS), also termed hyaline membrane disease, is one of the most prevalent causes of morbidity and mortality in newborns (1). The oxygen diffusion efficiency through the alveoli-capillary exchange barrier is impacted by the dysregulation of numerous factors, leading to the pathophysiology of NRDS (2). Cellular stress at the gas-blood level is associated with alterations in alveolar surfactant proteins (3) and the upregulation of numerous innate immune responses of pro-inflammatory cytokines to foreign challenges (4). A lack of surfactant may drive the pathogenesis towards NRDS, while surfactant replacement therapy may mitigate symptoms of the disease by decreasing the surface tension of alveoli and facilitating their inflation (5,6). However, surfactant serves an additional role in immunological processes. A recent study demonstrated that applying clinical surfactant for patients led to a stronger response to challenges from foreign microbiota (7). Additionally, animal-derived surfactant applied for clinical use in humans has been demonstrated to be of use against lung pathogens and to mediate excess host damage from neutrophils (8). Therefore, it may be hypothesized that mechanisms that mechanisms of NRDS involving surfactant exert additional functions to promoting alveolar inflation. > Acute respiratory distress syndrome (ARDS) is a clinical phenotype precipitated by the manifestation of a severe form of lung injury due to numerous lung insults (9). The pathophysiological manifestation of ARDS is derived from a cascade that is triggered by the complex combination of risk factors, including asthma, sepsis, pneumonia, increased neutrophil presence in the lungs and other variables; accumulation of these numerous systemic factors forms the pathological endpoint of ARDS (10). > The present study used peripheral blood obtained from infants with (n=4) or without (n=2) NRDS in tandem with mRNA-sequencing (mRNA-seq) analysis to reveal various factors involved in the mechanisms of NRDS, and to compare onset mechanisms between NRDS and ARDS.

[10] NR4A1 Promotes LPS-Induced Acute Lung Injury through Inhibition of Opa1-Mediated Mitochondrial Fusion and Activation of PGAM5-Related Necroptosis

Authors: Pingjun Zhu, Junyan Wang, Wenjuan Du, Jun Ren, Ying Zhang et al.
Year: 2022
Venue: Oxidative Medicine and Cellular Longevity
URL: https://www.semanticscholar.org/paper/7551d2b7ca961dd3d6f1e79086321b021411941d
DOI: 10.1155/2022/6638244
PMID: 35222801
PMCID: 8881136
Citations: 29
Summary: The data identified NR4A1 as a novel regulator of LPS‐related acute lung injury through regulation of mitochondrial fusion and necroptosis, indicating therapeutic promises of targeting NR4A1 in the treatment of acute lung injury in clinical practice.
Evidence snippets:
Snippet 1 (score: 0.440) > Acute respiratory distress syndrome (ARDS), a diffused injury of the lung parenchyma evoked by pathological stresses including severe infection, anoxia, ischemia, trauma, and surgery [1,2], is deemed one of the most common refractory complications with high mortality and mortality in critically ill patients [3,4]. To date, effective therapy for ARDS is still lacking. Ample experimental findings have unveiled the pathogenesis of ARDS with beneficial effects from pharmacological and mechanical conditioning strategies [5]. In particular, a number of mechanisms have been Oxidative Medicine and Cellular Longevity suggested to contribute to ARDS including oxidative stress, inflammation response, and immunomodulatory disorders [6][7][8]. A better understanding of the interplay among these pathological factors should help to unveil novel therapeutic strategies for acute lung injury and clinical outcomes in patients with ARDS. > Given the important role of mitochondria in energy metabolism through consumption of nutrient and oxygen by way of tricarboxylic acid cycle and oxidative phosphorylation (OXPHOS), mitochondria serve as the powerhouse in cells [9]. Besides, a range of cellular physiological processes such as oxidative stress, calcium regulation, signaling transduction, cell movement, growth, proliferation, and death are controlled by mitochondria, especially in respiratory diseases including but not limited to ARDS. Mitochondrialderived reactive oxygen species (ROS) has aroused considerable attention due to its dual regulatory role in ARDS [10]. In lipopolysaccharide-(LPS-) induced acute lung injury, mitochondrial APT production is reduced whereas levels of ROS are elevated, because of neutrophil accumulation in lung tissues [11]. Furthermore, mitochondrial ROStriggered oxidative damage as well as mitochondrial apopto-sis is noted in kidney tissues following LPS challenge [12]. Another independent study in a model of endotoxininduced ARDS revealed a connection between mitochondrial bioenergetic dysfunction and impaired pulmonary ventilation [13]. These findings indicate a role of mitochondrial dysfunction in acute lung injury although precise molecular mechanisms are not fully understood.

[11] Candidate genes and pathogenesis investigation for sepsis-related acute respiratory distress syndrome based on gene expression profile

Authors: Min Wang, Jingjun Yan, Xingxing He, Q. Zhong, Cheng-ye Zhan et al.
Year: 2016
Venue: Biological Research
URL: https://www.semanticscholar.org/paper/88c3aefab1fe6d50848633dff472cda669b57ae2
DOI: 10.1186/s40659-016-0085-4
PMID: 27090785
PMCID: 4835843
Citations: 22
Influential citations: 1
Summary: Genes including CCNB1, CCNB2 and TOP2A, as well as transcription factors like FOXM1 might be used as the novel gene therapy targets for sepsis related ARDS.
Evidence snippets:
Snippet 1 (score: 0.439) > Acute respiratory distress syndrome (ARDS) is a potentially devastating form of acute inflammatory lung injury as well as a major cause of acute respiratory failure. Although researchers have made significant progresses in elucidating the pathophysiology of this complex syndrome over the years, the absence of a universal detail disease mechanism up until now has led to a series of practical problems for a definitive treatment. This study aimed to predict some genes or pathways associated with sepsis-related ARDS based on a public microarray dataset and to further explore the molecular mechanism of ARDS. A total of 122 up-regulated DEGs and 91 down-regulated differentially expressed genes (DEGs) were obtained. The up- and down-regulated DEGs were mainly involved in functions like mitotic cell cycle and pathway like cell cycle. Protein–protein interaction network of ARDS analysis revealed 20 hub genes including cyclin B1 (CCNB1), cyclin B2 (CCNB2) and topoisomerase II alpha (TOP2A). A total of seven transcription factors including forkhead box protein M1 (FOXM1) and 30 target genes were revealed in the transcription factor-target gene regulation network. Furthermore, co-cited genes including CCNB2-CCNB1 were revealed in literature mining for the relations ARDS related genes. Pathways like mitotic cell cycle were closed related with the development of ARDS. Genes including CCNB1, CCNB2 and TOP2A, as well as transcription factors like FOXM1 might be used as the novel gene therapy targets for sepsis related ARDS.

[12] A comprehensive systematic review of the phenotypes and their role in improving medications and clinical results in the acute respiratory distress syndrome: exploring the potential of personalized therapy

Authors: E. R. Surabhi, Devanshu J. Patel, Asha Kademane, Pradeep Nirala
Year: 2024
Venue: Multidisciplinary Reviews
URL: https://www.semanticscholar.org/paper/82200075790bb220d807d97ca7f9f49d62449341
DOI: 10.31893/multirev.2023ss006
Summary: The significance of customizing research trials to the exact stage of lung damage that patients are experiencing, as well as premature treatment and preventive intervention and developed ARDS therapy are discussed.
Evidence snippets:
Snippet 1 (score: 0.438) > The Acute Respiratory Distress Syndrome (ARDS) is a disorder that can be severe and it is characterized by severe breathing difficulties, such as the various clinical risk factors, lung injury mechanisms, microbiological aspects and biological factors. The current systematic review intends to investigate the phenotypic diversity in ARDS and the possibility of individualized treatment in improving clinical outcomes. In the field of molecular phenotyping, biomarker panels show promise as useful tools for identifying patients who are at risk of developing ARDS, diagnosing the disease, assisting in risk assessment and allowing for ongoing observation. The hyper-inflammatory subphenotype is associated with diseases including metabolic acidosis, shock and worse clinical outcomes. Biologic phenotypes are taken into consideration, such as gene expression, common causal microbiologic infections and plasma protein biomarkers. This review underlines the variations in etiology, clinical manifestations and treatment responses for the diverse phenotypes, including subtypes of direct and indirect lung damage. We will talk about the significance of customizing research trials to the exact stage of lung damage that patients are experiencing, as well as premature treatment and preventive intervention and developed ARDS therapy. Customized therapy can become a reality as a result of improved clinical trial design and execution brought by a deeper comprehension of the interactions between various factors in ARDS.

[13] Single-cell analysis reveals dysregulated inflammatory response in peripheral blood immunity in patients with acute respiratory distress syndrome

Authors: Jingjia Mo, Yanli Yang, Jihua Feng, Yanhua Lei, Suhong Huang et al.
Year: 2023
Venue: Frontiers in Cell and Developmental Biology
URL: https://www.semanticscholar.org/paper/38d0e7e914d64151dc384d2d068b30f351473825
DOI: 10.3389/fcell.2023.1199122
PMID: 37283946
PMCID: 10239863
Citations: 7
Summary: The composition of cells involved in the main peripheral circulation differs in patients with ARDS with different etiologies, and a significant enhancement of the oxidative stress response was observed in the neutrophil subpopulation.
Evidence snippets:
Snippet 1 (score: 0.432) > Introduction: Acute respiratory distress syndrome (ARDS) remains a major clinical challenge for patients in intensive care units. Determining the differential mechanisms underlying ARDS with different etiologies is a key goal to improve the effectiveness of ARDS therapy. Despite growing evidence that different immune cell types are involved in ARDS, the role of altered immune cell subpopulations in disease progression is unelucidated. Methods: In this study, we combined scRNA-seq and bulk-level sequencing to analyze the transcriptomes of peripheral blood mononuclear cells from healthy volunteers and patients with septic ARDS (sep-ARDS) and pneumonic ARDS (PNE-ARDS). Results: Our data revealed differential alterations at the cellular and molecular levels and within biological signaling pathways in ARDS with different etiologies. The dynamics of neutrophils, macrophages (Macs), classical dendritic cells (cDCs), myeloid-derived suppressive cells (MDSCs), and CD8+ T cells varied significantly among groups of different samples, with neutrophils and cDCs at higher, and Macs at significantly lower, amounts in the patients with sep-ARDS. Furthermore, MDSCs were highly enriched only in the sep-ARDS patients, whereas a higher abundance of CD8+ T cells was observed in patients with PNE-ARDS. In addition, these cell subpopulations were found to be significantly involved in apoptosis, inflammatory, and immune-related pathways. In particular, a significant enhancement of the oxidative stress response was observed in the neutrophil subpopulation. Conclusion: Our study shows that the composition of cells involved in the main peripheral circulation differs in patients with ARDS with different etiologies. Studying the role and mechanism of action of these cells during ARDS will provide new opportunities for the treatment of this condition.

[14] Advancement in Precision Medicine and Recommendation System for Clinical Trials Using Deep Learning Methods

Authors: A.P.Ponselvakumar, S. Anandamurugan, K.Logeswaran, S.Nivashini, S.K.Showentharya et al.
Year: 2021
Venue: IOP Conference Series: Materials Science and Engineering
URL: https://www.semanticscholar.org/paper/09c40cae147b54bbb86db9825a1c96299acedbc5
DOI: 10.1088/1757-899X/1055/1/012110
Citations: 6
Influential citations: 1
Summary: Both combination of recommendation system along with deep learning quality of precision healthcare achieved to patients are revealed.
Evidence snippets:
Snippet 1 (score: 0.432) > The following paper [25] briefly talks about biomarkers which play a significant role within the treatment of respiratory functionalities. It is stated that over 10% of patients hospitalized in critical care are affected by Acute Lung Injury. The most intense type of ALI is Acute respiratory distress syndrome (ARDS) in which 40% fatality rate is observed. The contribution of biomarkers to the pathophysiology of ARDS is considerably very less. Nevertheless, a major problem is that ARDS is such a diverse, multi-factorial, termination condition that the techniques for "lumping and splitting" are severe. > However, the appliance of network biology to ARDS is made possible with the help of human genome sequencing and the provision of improved techniques for the analysis purpose of transcription to mRNA (gene expression), and also due to the development of sensitive immunoassays. In the field of molecular phenotypic is to identify the patients who at the danger to develop ARDS, biomarker panels have gained prospective applications. This composite disease continues to be serious and deadly event even though the process of dealing and controlling of ARDS has been developed. Monoclonal antibodies (anti-TNF) and TNFR fusion protein have given uncompromising results. However, with the advancement in the techniques of mechanical ventilation, a neuromuscular blocker has shown some positive result, and somatic cell therapy is being well developed. In the future, it is expected that this could give logical remedial targets, and eventually improve clinical care since the comprehension role of biomarkers are incorporated into the pathophysiology of ARDS and lung problems. > This paper [26] briefly discusses the approach that though there are many clinical benefits specifying the importance to produce treatment for sparse diseases and cancer but the impact on the dealing and control of quite composite diseases, like type 2 diabetes, remains too low. This paper primarily specifies the ways by which people fall as a prey to poor health through the appliance of diagnostic labels. This review suggests a different, 'palette' model, center placed on a molecular taxonomy that aims on positioning an individual in accordance to the most pathophysiological processes that put-up to the risk and development of diabetes.

[15] Longitudinal multi-omic signatures of ARDS and sepsis inflammatory phenotypes identify key pathways associated with mortality

Authors: N. Alipanah-Lechner, L. Neyton, Pratik Sinha, Carolyn Leroux, K. Bardillon et al.
Year: 2025
Venue: medRxiv
URL: https://www.semanticscholar.org/paper/7ac6ad9892581d7caf0f6dd0c6c799180f575391
DOI: 10.1101/2025.05.07.25327117
PMID: 40963763
PMCID: 12440049
Citations: 3
Summary: Analysis of blood samples from ARDS patients in the ROSE trial revealed metabolomic and transcriptomic differences between Hyperinflammatory and Hypoinflammatory phenotypes and suggest potential therapeutic targets for precise treatment strategies in critical illness.
Evidence snippets:
Snippet 1 (score: 0.432) > The acute respiratory distress syndrome (ARDS) and sepsis are devastating critical illness syndromes with unacceptably high mortality rates approaching 40-50% in the United States (1,2). A significant challenge to developing effective treatments has been the marked heterogeneity in clinical presentation, underlying biology, and treatment responses among affected patients (3,4). > Recent advances in molecular phenotyping have identified reproducible subgroups of ARDS and sepsis patients with distinct pathobiology. Latent class analyses (LCA) of clinical and plasma protein data consistently reveal two predominant phenotypes: a "Hyperinflammatory" phenotype characterized by elevated plasma inflammatory protein biomarkers, shock, and higher mortality, and a "Hypoinflammatory" phenotype with relatively lower inflammatory protein biomarkers and better outcomes (5)(6)(7)(8)(9)(10). These phenotypes, identified across multiple ARDS and sepsis cohorts, demonstrate differential therapeutic responses in secondary analyses of randomized trials, suggesting they represent endotypes with distinct disease mechanisms (5,11,12). Clinical trials incorporating prospective phenotyping are being developed, including the PANTHER trial, which will start enrolling in mid-2025 (13). However, the biological processes driving each phenotype and mechanisms underlying unfavorable outcomes within each phenotype remain poorly understood. While protein biomarker studies have provided valuable insights into inflammatory patterns, they capture only a small fraction of the complex molecular landscape. > Previous metabolic profiling of 93 patients with ARDS demonstrated that the Hyperinflammatory phenotype exhibits reduced circulating lipids and a glycolytic shift, while transcriptomic analyses revealed increased expression of genes related to the innate immune response and tissue remodeling and reduced interferon signaling (10,14). However, isolatedomic approaches may miss critical interactions between cellular programming and systemic metabolism essential for understanding disease processes and treatment responses. > In this study, we applied longitudinal multi-omics profiling to characterize the molecular basis of ARDS/sepsis inflammatory phenotypes and identify mechanisms associated with poor outcomes.

[16] Development and functional significance of the pulmonary surfactant system

Authors: R. Shakhbanov, M. N. Asadulaeva, S.N. Alieva, A.A. Alimkhanova
Year: 2021
Venue: RUDN Journal of Medicine
URL: https://www.semanticscholar.org/paper/659ee76d2589b60002a27426d73bbf9734de6c63
DOI: 10.22363/2313-0245-2021-25-4-321-331
Citations: 2
Summary: To increase the effectiveness of pharmacological and respiratory therapy of acute respiratory distress syndrome, as well as to identify the role of the surfactant system of the lungs in the onset of inflammation against the background of tuberculosis and the development of regeneration mechanisms that affect the course and outcome of the disease.
Evidence snippets:
Snippet 1 (score: 0.429) > Relevance. Prevention of the development of postoperative acute respiratory distress syndrome during operations on the descending thoracic aorta increases the effectiveness of therapy. The study of damage to the surfactant complex during ischemia and reperfusion of the lungs is relevant, since it involves the prophylactic use of the surfactant preparation during operations on the descending part of the thoracic aorta, which are characterized by a high risk of postoperative acute respiratory distress syndrome. Objective: to increase the effectiveness of pharmacological and respiratory therapy of acute respiratory distress syndrome, as well as to identify the role of the surfactant system of the lungs in the onset of inflammation against the background of tuberculosis and the development of regeneration mechanisms that affect the course and outcome of the disease. Materials and Methods. The study involved 24 people, including 14 volunteer patients with a diagnosed respiratory disease in an acute course (while the whole group received the drug from the study as an additional therapy). The sample of 14 people was formed solely due to the compliance of these patients with the criteria that were established before the start of the study of the drug, which had postoperative acute respiratory distress syndrome of various origins in their diagnosis. Results and Discussion. For a comprehensive laboratory determination, an algorithm was used that corresponded to the state standard to identify postoperative acute respiratory distress syndrome. For each participant in the experiments, it was proposed to develop a plan of treatment procedures, taking into account individualization and standardization. Conclusion. Some of the resulting data are collected with respect to the surfactant pulmonary system, which is presented in a compactor model format. A number of basic components are reflected here, which are classified according to cellular and non-cellular factors. At the same time, the surfactant substance helps to reduce the pronounced swelling, which can significantly reduce the process of sticking of the alveolar structures during inhalation. All this added up to the normal system of gas metabolism in the lung structures, including the control of the mucociliary system, which acts as a natural stimulator of the function of alveolar macrophages.

[17] Values of integration between lipidomics and clinical phenomes in patients with acute lung infection, pulmonary embolism, or acute exacerbation of chronic pulmonary diseases: a preliminary study

Authors: Danyan Gao, Linlin Zhang, Dongli Song, Jiapei Lv, Linyan Wang et al.
Year: 2019
Venue: Journal of Translational Medicine
URL: https://www.semanticscholar.org/paper/bfd5c241ee1900a466476b56326304c9c9e0d73a
DOI: 10.1186/s12967-019-1898-z
PMID: 31109325
PMCID: 6528323
Citations: 22
Summary: It is demonstrated that lipidomic profiles of patients with acute lung diseases are different from healthy lungs, and there are also disease-specific portions of lipidomics among SAP, APE, or AECOPD.
Evidence snippets:
Snippet 1 (score: 0.428) > Acute lung injury is a major challenge and cause of patient morbidity and mortality in pulmonary critical care units, as an early stage of acute respiratory distress syndrome (ARDS), although molecular diagnosis and therapy are still lacking due to the complex pathogenesis, severity, and systemic responses [1]. Acute infection is one of common factors that can induce the exacerbation of chronic lung diseases. Chen et al., initially identified disease-specific dynamic biomarkers for severe pneumonia or severe pneumonia-associated-ARDS by integrating proteomic profiles of inflammatory mediators with clinical informatics as part of clinical bioinformatics [2]. They found that specific protein-based biomarkers comparing diseased tissue with healthy tissue and diseased tissue and diseased tissue had a significant correlation with clinical phenomes measured by Digital Evaluation Score System (DESS) scores. Shi et al. identified specific immunomodulatory mediators by evaluating dynamic genomic and proteomic profiles of peripheral blood mononuclear cells and plasma in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and found a complex network of AECOPD-or COPD-specific immunomodulatory mediators [3]. In addition to changes of genomic and proteomic profiles, alterations of systemic metabolisms are also another important factor which can influence disease severity, duration, progression, and patient response to therapy, although the metabolism has been ignored in understanding of molecular mechanisms in the development of acute and chronic pulmonary diseases. > Clinical lipidomics is a new integrative approach to identify the disease-specific correlation and regulation between a large scale of lipid elements measured in liquid biopsies from patients with their clinical phenomes [4]. Clinical lipidomics has been suggested as a novel approach in discovering new categories of disease-specific biomarkers or therapeutic targets and could play a key role in improving our understanding of molecular mechanisms in disease metabolisms [5]. However, challenges still remain to be faced and overcome in prior to clinical practice [6].

[18] Enhanced mortality prediction in pneumonia-associated acute respiratory distress syndrome: a model integrating lymphocyte subsets with clinical parameters in non-immunosuppressed adults

Authors: Z. Xing, Hua Guo, Ting Ao, Jin-Xiang Wang, Ming Hu
Year: 2026
Venue: Frontiers in Medicine
URL: https://www.semanticscholar.org/paper/c51c13a1a85020abf45c9c16509242a87294f662
DOI: 10.3389/fmed.2026.1844614
PMID: 42245930
PMCID: 13230041
Summary: A multidimensional model for predicting in-hospital mortality in non-immunosuppressed adult patients with pneumonia-associated ARDS was developed and demonstrated excellent predictive performance, which was significantly higher than that of the baseline model.
Evidence snippets:
Snippet 1 (score: 0.426) > Acute respiratory distress syndrome (ARDS) is a critical clinical syndrome characterized by diffuse pulmonary inflammation and damage to the alveolar epithelial-capillary barrier. The clinical, physiological, biological and imaging manifestations of ARDS are highly heterogeneous. It is primarily be divided into two types: intrapulmonary and extrapulmonary. The condition manifests as progressive respiratory distress and refractory hypoxemia (1)(2)(3). Despite substantial advancements in mechanical ventilation strategies and supportive care in recent years, ARDS continues to be a relatively frequent condition associated with high morbidity and mortality, with severe ARDS cases exhibiting mortality rates as high as 46-66% (4-7). Pneumonia constitutes a major etiological factor for ARDS, accounting for approximately 59% of all ARDS cases (5). In patients with pneumoniaassociated acute respiratory distress syndrome (p-ARDS), the interplay between the initial pathogen invasion and the dysregulated host immune response serves as a critical determinant of clinical progression and prognosis. > The Sequential Organ Failure Assessment (SOFA) score and the CURB-65 score are clinically established tools for quantifying the extent of organ dysfunction and predicting mortality in pneumonia patients. These tools primarily serve to assess the extent of physiological dysfunction but demonstrate significant limitations in evaluating underlying pathophysiological mechanisms, particularly the immune status. In studies of COVID-19-related ARDS, immune dysregulation has been identified as a core feature of the disease pathophysiology, typically manifesting as significant lymphopenia and alterations in the distribution and function of key lymphocyte subsets, such as helper T cells (8). Meanwhile, pertinent studies have confirmed that adaptive immune impairment occurs during sepsis. The increased apoptosis of T cells, B cells, and dendritic cells drives a shift in the immune system from an initial pro-inflammatory state toward an anti-inflammatory and immunosuppressive response, potentially resulting in immunosuppression (9).

[19] [Genetic predisposition and Pediatric Acute Respiratory Distress Syndrome: New tools for genetic study].

Authors: B. Erranz, Jan Wilhelm, Raquel Riquelme, Pablo Cruces
Year: 2015
Venue: Revista chilena de pediatria
URL: https://www.semanticscholar.org/paper/9a0026c01cee098398beff7678483ecb888e06ce
DOI: 10.1016/j.rchipe.2015.04.016
PMID: 26235685
Summary: Genome-wide association studies can objectively examine variations of genes involved in key processes of tissue, cellular and molecular lung damage to help identify important new genes and pathogenetic pathways for future analysis and have diagnostic and therapeutic implications.
Evidence snippets:
Snippet 1 (score: 0.425) > Acute respiratory distress syndrome (ARDS) is the most severe form of respiratory failure. Theoretically, any acute lung condition can lead to ARDS, but only a small percentage of individuals actually develop the disease. On this basis, genetic factors have been implicated in the risk of developing ARDS. Based on the pathophysiology of this disease, many candidate genes have been evaluated as potential modifiers in patient, as well as in animal models, of ARDS. Recent experimental data and clinical studies suggest that variations of genes involved in key processes of tissue, cellular and molecular lung damage may influence susceptibility and prognosis of ARDS. However, the pathogenesis of pediatric ARDS is complex, and therefore, it can be expected that many genes might contribute. Genetic variations such as single nucleotide polymorphisms and copy-number variations are likely associated with susceptibility to ARDS in children with primary lung injury. Genome-wide association (GWA) studies can objectively examine these variations, and help identify important new genes and pathogenetic pathways for future analysis. This approach might also have diagnostic and therapeutic implications, such as predicting patient risk or developing a personalized therapeutic approach to this serious syndrome.

[20] Comorbidity Networks in Cardiovascular Diseases

Authors: Héctor A. Cruz-Ávila, M. Vallejo, M. Martínez-García, E. Hernández-Lemus
Year: 2020
Venue: Frontiers in Physiology
URL: https://www.semanticscholar.org/paper/1454c6cc3ca61441b24fd8c65ce02935b2845274
DOI: 10.3389/fphys.2020.01009
PMID: 32982776
PMCID: 7485389
Citations: 35
Influential citations: 1
Summary: It is found that comorbidity networks are highly centralized in prevalent diseases, such as cardiac arrhythmias, heart failure, chronic kidney disease, hypertension, and ischemic diseases, which may lead to further development of better, integrated therapeutic strategies.
Evidence snippets:
Snippet 1 (score: 0.424) > The first one of such pairs is formed by Other and unspecified encephalopathy (G93.4) and Acute respiratory distress syndrome (J80.X) with 437 common genes (JI = 0.827651515). These apparently disparate diseases share physiological and clinical associations. Burad et al. (2012) found that acute respiratory syndrome in pneumonia patients leads to strong systemic ischemia that may in turn develop into acute encephalopathy. This finding has been further confirmed in a very large (5.6 million cases) epidemiological risk factor study of the group of Bell in the US (Rincon et al., 2014). Aside from environmental and other risk factors, these diseases large number of shared genes are involved in a number of relevant biomolecular pathways, ranging from essential metabolism (folate-mediated one-carbon metabolism, antifolate resistance), signal transduction (cell adhesion, transendothelial leukocyte migration, a tight junction regulation). Also, including immune response and inflammation (response to hepatitis C, natural killer cell-mediated cytotoxicity, response to measles, Alzheimer's disease, and response to Influenza), as it was evidenced by gene enrichment analysis whose statistical significance was assessed via hypergeometric tests with false discovery rate multiple-testing correction (see Methods). > Closely related to this pair is the second one formed by Other and unspecified encephalopathy (G93.4) and Acute respiratory failure (J96.0) with 440 common genes representing a JI = 0.787119857, these genes refer to similar pathways involved with the addition of statistical enrichment of the protein digestion and absorption pathway. Understanding the role that such molecular processes may have in the onset and progression of both diseases, of the comorbidity and of their potential multimorbidity relations in the context of the CVCnetwork (see Figure 4), may prove useful, particularly in the design of combined therapeutic strategies with special emphasis in the critically ill patients in intensive care units. > In this regard, we may mention the following: it is known that the physiological manifestation of such biomolecular process starts in the microvascular endothelium (MVE).

Notes

This provider combines search_papers_by_relevance with snippet_search.
No synthesis or second-stage model call is performed.

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Acute Respiratory Distress Syndrome (ARDS) — Disease Characteristics Research Report

claude-haiku-4-5-20251001, claude-opus-5[1m] 18 citations 2026-09-01T08:32:21.991297

Acute Respiratory Distress Syndrome (ARDS) — Disease Characteristics Research Report

Compiled 2026-09-01 for the dismech knowledge base. Quick orientation note before the technical part: ARDS is less a disease than a failure mode — the lung's version of a blown gasket. Lots of different insults, one shared way of breaking. That shapes everything below: the genetics are thin, the mechanism is rich, and most of the therapeutic wins have come from not making the injury worse rather than from fixing it.

Verification status. Abstracts marked with a blockquote were retrieved verbatim via NCBI E-utilities during this session and the quoted strings are exact substrings of those abstracts. Claims sourced only from web search summaries are flagged [unquoted — verify before use as an evidence snippet]. Ontology identifiers marked ✅ were confirmed present in this repository's committed term caches (cache/<prefix>/terms.csv); those marked ⚠️ are suggestions that have not been resolved and must be checked with OAK before binding.

Existing KB state. kb/disorders/Acute_Respiratory_Distress_Syndrome.yaml already exists (1,783 lines, created 2026-08-08) with has_subtypes, mechanistic_hypotheses, progression, 11 pathophysiology nodes, histopathology, biochemical, phenotypes, diagnosis, treatments, discussions, and experimental_models. It has no genetic:, environmental:, prevalence:, animal_models:, clinical_trials:, definitions:, classifications:, mappings:, or comorbidities: blocks, and datasets: is empty. Sections 2, 5, 9, 10, 12 and 15 below are therefore the highest-yield for enrichment.

1. Disease Information

Overview

ARDS is an acute, diffuse, inflammatory lung injury that follows either a direct pulmonary insult (pneumonia, aspiration, inhalation injury, pulmonary contusion) or an indirect systemic one (non-pulmonary sepsis, trauma, pancreatitis, massive transfusion). Increased permeability of the pulmonary microvascular endothelium and the alveolar epithelium produces protein-rich, non-cardiogenic pulmonary oedema and loss of aerated lung, giving bilateral radiographic opacities, intrapulmonary shunt, reduced respiratory-system compliance, and acute hypoxaemic respiratory failure.

The canonical framing from the Nature Reviews Disease Primers article (PMID:30872586, Thompson/Matthay/Bellani et al., Nat Rev Dis Primers 2019;5:18):

"The acute respiratory distress syndrome (ARDS) is a common cause of respiratory failure in critically ill patients and is defined by the acute onset of noncardiogenic pulmonary oedema, hypoxaemia and the need for mechanical ventilation. ARDS occurs most often in the setting of pneumonia, sepsis, aspiration of gastric contents or severe trauma and is present in ~10% of all patients in intensive care units worldwide."

And on the heterogeneity that dominates modern thinking (PMID:36070787, Bos & Ware, Lancet 2022;400:1145-1156):

"The pathophysiology of ARDS is complex and involves the activation and dysregulation of multiple overlapping and interacting pathways of injury, inflammation, and coagulation, both in the lung and systemically."

Definitional history

Definition	Year	PMID	Key features
Ashbaugh original case series	1967	4143721	Lancet 1967;2:319-23, "Acute respiratory distress in adults" — 12 patients, tachypnoea, hypoxaemia refractory to oxygen, reduced compliance, diffuse infiltrates
American-European Consensus Conference (AECC)	1994	—	ALI (PaO₂/FiO₂ ≤300) vs ARDS (≤200); PAWP criterion
Berlin Definition	2012	22797452	Three severity strata, timing ≤1 week, exclusion of cardiac failure by clinical judgement/echo
New Global Definition	2024	37487152	Adds HFNO, SpO₂/FiO₂, ultrasound, resource-limited category

Berlin (PMID:22797452, JAMA 2012;307:2526-33):

"A draft definition proposed 3 mutually exclusive categories of ARDS based on degree of hypoxemia: mild (200 mm Hg < PaO2/FIO2 ≤ 300 mm Hg), moderate (100 mm Hg < PaO2/FIO2 ≤ 200 mm Hg), and severe (PaO2/FIO2 ≤ 100 mm Hg)"

"Using the Berlin Definition, stages of mild, moderate, and severe ARDS were associated with increased mortality (27%; 95% CI, 24%-30%; 32%; 95% CI, 29%-34%; and 45%; 95% CI, 42%-48%, respectively; P < .001)"

The most important recent development in the field is the New Global Definition (PMID:37487152, Matthay et al., Am J Respir Crit Care Med 2024;209(1):37-47, doi:10.1164/rccm.202303-0558WS):

"The committee made four main recommendations: 1) include high-flow nasal oxygen with a minimum flow rate of ⩾30 L/min; 2) use PaO2:FiO2 ⩽ 300 mm Hg or oxygen saturation as measured by pulse oximetry SpO2:FiO2 ⩽ 315 (if oxygen saturation as measured by pulse oximetry is ⩽97%) to identify hypoxemia; 3) retain bilateral opacities for imaging criteria but add ultrasound as an imaging modality, especially in resource-limited areas; and 4) in resource-limited settings, do not require positive end-expiratory pressure, oxygen flow rate, or specific respiratory support devices."

Rationale, same abstract:

"Since publication of the 2012 Berlin definition of acute respiratory distress syndrome (ARDS), several developments have supported the need for an expansion of the definition, including the use of high-flow nasal oxygen, the expansion of the use of pulse oximetry in place of arterial blood gases, the use of ultrasound for chest imaging, and the need for applicability in resource-limited settings."

The three categories are intubated ARDS, non-intubated ARDS (HFNO ≥30 L/min or NIV/CPAP with PEEP ≥5), and ARDS in resource-limited settings. A Spanish-language review summarises the trajectory (PMID:38644108, Med Intensiva 2024;48:272-281):

"In 2021, a New Global Definition based on the Berlin definition of ARDS was proposed, which included a category for non-intubated patients, considered the use of SpO2, and established no particular requirement for oxygenation support in regions with limited resources."

Validation work using MIMIC-IV is under way (PMID:38483560, Intensive Care Med 2024;50:608-609, "The new global definition of acute respiratory distress syndrome: insights from the MIMIC-IV database") — [unquoted].

Paediatric ARDS is defined separately by PALICC-2 (PMID:36661420, Pediatr Crit Care Med 2023, "Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2)"; epidemiology companion PMID:36661438) — PALICC uses oxygenation index / oxygen saturation index rather than P/F, and does not require bilateral infiltrates. [unquoted] This is a strong candidate for a has_subtypes entry or a separate definitions: block.

Identifiers

Resource	Identifier	Status
MONDO	`MONDO:0006502` — acute respiratory distress syndrome	✅ in `cache/mondo/terms.csv`; already bound in the KB entry
HPO	`HP:0033677` — Acute respiratory distress syndrome	✅ in `cache/hp/terms.csv`
ICD-10-CM	J80 (Acute respiratory distress syndrome)	⚠️ verify against `cache/icd10cm/`
ICD-11	CB00 (Acute respiratory distress syndrome)	⚠️ verify against `cache/icd11f/`
MeSH	D012128 (Respiratory Distress Syndrome, Adult / Acute)	⚠️ not a dismech-bound prefix
SNOMED CT	67782005	⚠️ guide-only in this repo
OMIM	Not applicable — no Mendelian OMIM entry; ARDS is a complex acquired syndrome
Orphanet	Not applicable — not a rare disease; no ORPHA code
NCIT	`NCIT:C3353` (Adult Respiratory Distress Syndrome)	⚠️ not in the local cache; verify with `runoak -i sqlite:obo:ncit info NCIT:C3353`

Synonyms and alternative names

ARDS; acute respiratory distress syndrome; adult respiratory distress syndrome (historical, deprecated — the syndrome occurs in children); shock lung; wet lung; Da Nang lung (historical, Vietnam-war military usage); post-traumatic respiratory insufficiency; acute lung injury (ALI — a former milder category retired by the Berlin definition, now subsumed as "mild ARDS"); diffuse alveolar damage (DAD — the histological correlate, not a synonym; see §10); non-cardiogenic pulmonary oedema; capillary leak lung injury.

Curation caution (Named Entity Confusion): "respiratory distress syndrome" without a qualifier most often refers to neonatal RDS / hyaline membrane disease (surfactant deficiency of prematurity, HP:0002643 Neonatal respiratory distress ✅) — a genuinely different disease with a different mechanism. Dataset and literature searches on the bare phrase will return neonatal RDS, and gene-symbol searches on surfactant genes (SFTPB, SFTPC, ABCA3) will return the congenital surfactant deficiencies rather than ARDS. Screen these out.

Data provenance character

Both. ARDS knowledge derives from (a) aggregated disease-level resources — international point-prevalence cohorts (LUNG SAFE), RCT networks (ARDSNet/PETAL, ESICM), consensus definitions; and (b) individual patient-level data — EHR-derived cohorts are increasingly central. MIMIC-IV in particular is now used both to validate the global definition (PMID:38483560) and to derive subphenotypes at scale (24,363 ICU admissions in a 2025 ATS abstract; [unquoted]). ARDS is unusual among dismech entries in that a large fraction of its biology comes from secondary analyses of RCT biospecimen repositories (ARMA, ALVEOLI, FACTT, HARP-2, SAILS) rather than from disease registries.

2. Etiology

Disease causal factors

ARDS has no single cause. It is a stereotyped response to a heterogeneous set of insults, conventionally split by route:

Direct (pulmonary) insults — roughly 55-60% of cases - Pneumonia (bacterial, viral, fungal) — the single most common precipitant worldwide - Aspiration of gastric contents (chemical pneumonitis from low-pH, particulate material) - Inhalation injury (smoke, chlorine, phosgene, high-concentration oxygen) - Pulmonary contusion (blunt chest trauma) - Near-drowning - Pulmonary vasculitis - Reperfusion injury after lung transplantation or pulmonary embolectomy - E-cigarette/vaping product use-associated lung injury (EVALI) — note the repo already has E-Cigarette_or_Vaping_Product_Use-Associated_Lung_Injury.yaml

Indirect (extrapulmonary) insults — roughly 40-45% - Non-pulmonary sepsis (abdominal, urinary, soft-tissue) — the largest indirect category - Severe non-thoracic trauma with shock - Acute pancreatitis - Massive transfusion / TRALI (transfusion-related acute lung injury) - Cardiopulmonary bypass - Drug overdose and drug reactions (amiodarone, bleomycin, salicylates, opioids) - Burns - Fat embolism syndrome - Amniotic fluid embolism / obstetric catastrophe

Ontology suggestion for the precipitant node: the KB entry's node "Direct Pulmonary or Indirect Systemic Insult" already carries conforms_to: "alveolar_capillary_barrier_failure#Alveolar-Capillary Interface Insult". That module is the right conformance anchor.

Not every risk factor confers equal risk. From the LIPS validation cohort (PMID:20802164, Gajic et al., Am J Respir Crit Care Med 2011;183:462-70):

"The frequency of ALI varied according to predisposing conditions (from 3% in pancreatitis to 26% after smoke inhalation)."

"Twenty-two hospitals enrolled 5,584 patients at risk. ALI developed a median of 2 (interquartile range 1-4) days after initial evaluation in 377 (6.8%; 148 ALI-only, 229 adult respiratory distress syndrome) patients."

This is a good source for a RISK_FACTOR structure and for the point that only a minority of at-risk patients progress — the host response, not the insult alone, determines who gets ARDS.

Genetic risk factors

There is no causal gene. ARDS is polygenic/multifactorial with small effect sizes, and the field has been chronically underpowered — case cohorts number in the low thousands against tens of thousands for common diseases.

Candidate-gene era (largely unreplicated). Early candidates were SFTPB (surfactant protein B), ACE, and IL6. The ACE insertion/deletion polymorphism rs1799752 (DD genotype → higher serum ACE) has been repeatedly associated with ARDS susceptibility and mortality, with inconsistent replication. [unquoted] Treat all candidate-gene ARDS associations as low-confidence unless a GWAS or large meta-analysis supports them.

GWAS-era findings (the ones with genome-wide support):

FLT1 / VEGFR1 (hgnc:3763, lowercase per repo convention — ⚠️ verify ID) — a GWAS-significant risk locus; blood FLT1 expression is higher in ARDS patients than in other critically ill patients, and rs9513106 has been reported to reduce sepsis-associated ARDS risk, plausibly by raising soluble FLT1 and damping VEGF signalling. [unquoted — from search summary; the primary citation needs to be retrieved and the snippet verified]

BORCS5 / DUSP16 at 12p13.2 — the best-supported novel locus. From PMID:34032881 (Wei et al., Intensive Care Med 2021;47:761-771, "Integrative omics provide biological and clinical insights into acute respiratory distress syndrome"):

"Meta-analyses of ARDS genome-wide association studies were performed with 1250 cases and 1583 controls in Europeans, and 387 cases and 387 controls in African Americans."

"There was distinct genetic heterogeneity in ARDS between Europeans and African Americans. rs7967111 at 12p13.2 was functionally associated with ARDS susceptibility in Europeans (odds ratio = 1.38; P = 2.15 × 10-8). Expression of two genes annotated at this locus, BORCS5 and DUSP16, was dynamic but ultimately decreased during ARDS development, as well as downregulated in immune cells alongside COVID-19 severity."

Note the explicit ancestry heterogeneity — a genuinely important curation point, and a reason not to generalise European-ancestry loci.

Mendelian-randomisation-nominated blood transcripts. From PMID:37922010 (Intensive Care Med 2024;50:46-55, "Identification of genetic profile and biomarkers involved in acute respiratory distress syndrome"):

"A total of 1736 traits, including 1223 blood RNA, 159 plasma proteins, and 354 non-gene phenotypes (classified by Biochemistry, Anthropometry, Disease, Nutrition and Habit, Immunology, and Treatment), exhibited a potentially causal relationship with ARDS development"

"Regarding candidate blood RNA, four genes were validated, namely TMEM176B, SLC2A5, CDC45, and VSIG8, showing differential expression in blood of ARDS patients compared to controls, as well as dynamic expression in mouse lung tissues."

"the addition of four blood genes and five immune cell proportions significantly improved the prediction performance of ARDS development, with 0.791 of the area under the curve from receiver-operator characteristic, compared to 0.725 for the basic model"

These are MR-nominated and transcriptionally validated, not established causal genes — grade any evidence item accordingly (SUPPORT + directness: INDIRECT is the honest tag for an MR-derived causal claim).

The field's own assessment of statistical power is captured by the title of an accompanying editorial: PMID:29438627, Am J Respir Crit Care Med 2018;197:1373-1374 — "Genome-Wide Association Study in Acute Respiratory Distress Syndrome. Finding the Needle in the Haystack to Advance Our Understanding of Acute Respiratory Distress Syndrome."

Other reported loci, all needing verification before citation: SELPLG (P-selectin glycoprotein ligand 1, from an African-ancestry GWAS), PPFIA1, NFE2L2 (NRF2 promoter variants), MYLK, ANGPT2, IL1RN, NAMPT/PBEF1, SOD3, TNF promoter variants, VEGFA, IL10, IL8/CXCL8, MIF, TLR1 (rs5743551). [all unquoted]

COVID-19 severity loci as a partial proxy. Because COVID-19 ARDS is a large and genetically well-powered subset, the COVID-19 Host Genetics Initiative / GenOMICC loci (LZTFL1/3p21.31, DPP9, IFNAR2, TYK2, OAS1, ABO, MUC5B) are frequently invoked. Curate these under COVID-19, not under generic ARDS — they are severity loci for one specific viral pneumonia, and the mechanism (interferon signalling, chemokine receptor expression) does not obviously generalise to aspiration or pancreatitis-associated ARDS.

Rare-variant work is emerging: "Rare genetic variant risks in patients with sepsis-associated acute respiratory distress syndrome" (PMC13040698) reports burden signals in sepsis-ARDS exomes. [unquoted — retrieve PMID before use]

Suggested inheritance block: HP:0010982 Polygenic inheritance ⚠️ (verify in cache/hp/), used with relationship_type: SUSCEPTIBILITY gene typing per the repo's digenic/polygenic guidance.

Environmental / acquired risk factors

Age — the dominant demographic risk factor. From PMID:16236739 (Rubenfeld et al., N Engl J Med 2005;353:1685-93): "The incidence of acute lung injury increased with age from 16 per 100,000 person-years for those 15 through 19 years of age to 306 per 100,000 person-years for those 75 through 84 years of age."
Chronic alcohol use disorder — one of the best-replicated modifiable risks, roughly doubling ARDS risk in at-risk patients; mechanistically attributed to glutathione depletion in the alveolar lining fluid and impaired alveolar epithelial barrier function. [unquoted]
Cigarette smoking — associated with ARDS after both trauma and non-pulmonary sepsis; secondhand smoke exposure has also been implicated. [unquoted]
Chronic ambient air pollution (ozone, PM₂.₅) — associated with higher ARDS incidence in at-risk cohorts. [unquoted] Good ECTO-binding candidate.
Hypoalbuminaemia, acidosis, tachypnoea, oxygen requirement, obesity, diabetes — LIPS "risk modifiers"; notably diabetes appears protective in several sepsis cohorts (see below).
Iatrogenic: high tidal volume ventilation, high FiO₂, blood-product transfusion (especially plasma from multiparous donors → TRALI), positive fluid balance, delayed source control.
Sex/ethnicity — ARDS incidence is higher in men in most cohorts; US Black and Hispanic patients have higher ARDS-associated mortality, with the contribution of biology vs. access to care unresolved. [unquoted] Curate this carefully as an outcome disparity rather than a biological claim.

Protective factors

Genetic: no robustly established protective variant. rs9513106 (FLT1) has been reported as risk-reducing [unquoted].
Diabetes mellitus — consistently associated with lower ARDS incidence in septic patients, an epidemiologically robust and mechanistically unexplained finding (hypotheses include hyperglycaemia-associated neutrophil dysfunction and metformin/thiazolidinedione effects). [unquoted] — a strong candidate for a KNOWLEDGE_GAP discussion.
Vitamin D sufficiency and vasodilator use — nominated by Mendelian randomisation. From PMID:34032881: "Causal inference implied that comorbidity of inflammatory bowel disease and elevated levels of C-reactive protein and interleukin-10 causally increased ARDS risk, while vitamin D supplementation and vasodilator use ameliorated risk." (Note: the VIOLET RCT of vitamin D₃ in critically ill patients at risk was neutral, so this MR signal is not confirmed by trial evidence — a good REFUTE/SUPPORT evidence pair.)
Lung-protective ventilation applied prophylactically in patients without ARDS reduces ARDS incidence — secondary prevention, see §13.
Aspirin — tested and negative. PMID:27179988, JAMA 2016, "Effect of Aspirin on Development of ARDS in At-Risk Patients Presenting to the Emergency Department: The LIPS-A Randomized Clinical Trial." [title verified; abstract not retrieved — do not quote]

Gene-environment interactions

The most-cited GxE framings, all needing primary-source verification before use: - NFE2L2 (NRF2) promoter haplotypes × oxidative insult (trauma, hyperoxia) — the antioxidant response is the interaction surface. - ACE I/D × sepsis — renin-angiotensin tone modulating pulmonary vascular permeability under an inflammatory challenge. - Alcohol use × GSTM1/glutathione pathway variation — the alveolar glutathione depletion story. - SFTPB variants × pneumonia — surfactant handling under a direct epithelial insult. - TLR1 rs5743551 × Gram-positive sepsis.

[all unquoted] Also note the general framing from PMID:36070787: ARDS's dependence on "activation and dysregulation of multiple overlapping and interacting pathways" makes single-locus × single-exposure models a poor fit; the field has largely shifted from GxE to subphenotype thinking (§6).

3. Phenotypes

ARDS phenotypes divide cleanly into (a) the defining respiratory phenotype, (b) systemic/multi-organ manifestations, (c) laboratory abnormalities, and (d) long-term sequelae. Frequencies below are approximate and reflect the intubated-ARDS population unless noted.

Core respiratory phenotypes

Phenotype	HPO suggestion	Frequency	Onset	Severity	Course
Acute respiratory distress syndrome (the syndrome itself)	`HP:0033677` ✅	definitional	acute (≤7 days from insult)	variable	acute/episodic
Hypoxaemia	`HP:0012418` ✅	~100% (definitional)	acute	mild→severe by P/F stratum	may worsen over 24-72 h
Dyspnoea	`HP:0002094` ✅	very frequent (pre-intubation)	acute	moderate-severe	progressive
Tachypnoea	`HP:0002789` ✅	very frequent	acute	moderate-severe	progressive
Respiratory failure	`HP:0002878` ✅	~100%	acute	severe	acute
Respiratory failure requiring assisted ventilation	`HP:0004887` ✅	~76% of ARDS in LUNG SAFE received invasive MV	acute	severe	acute
Pulmonary oedema (non-cardiogenic)	`HP:0100598` ✅	~100% (pathophysiologically definitional)	acute	severe	resolves with recovery
Cyanosis	`HP:0000961` ✅	occasional; severe hypoxaemia	acute	severe	acute
Decreased pulmonary compliance	⚠️ `HP:0011947`? Respiratory tract infection — no; check `HP:0002094` family. A precise HPO term for reduced compliance may not exist — likely `preferred_term`-only with no binding	frequent	acute	moderate-severe	acute
Pulmonary fibrosis (fibroproliferative phase)	`HP:0002206` ✅	~20-40% of persistent ARDS shows fibroproliferation	subacute (≥day 7)	variable	may be progressive or resolve

Quality-of-life note per phenotype: the acute respiratory phenotypes are experienced under sedation in most intubated patients; the QoL burden is dominated by post-ICU sequelae (below) rather than by the acute hypoxaemia itself.

Systemic / extrapulmonary phenotypes

Shock requiring vasopressors — markedly more prevalent in the hyperinflammatory subphenotype (PMID:24853585: "a higher prevalence of vasopressor use").
Metabolic acidosis HP:0001942 ✅ / lactic acidosis HP:0003128 ✅ — PMID:24853585 notes "lower serum bicarbonate concentrations" in the hyperinflammatory class.
Acute kidney injury ⚠️ HP:0001919 (Acute kidney injury) — verify. A very common co-failing organ; drives RRT use.
Delirium / ICU-acquired encephalopathy ⚠️ HP:0031258? verify.
ICU-acquired weakness / critical illness polyneuromyopathy ⚠️ — relevant to the neuromuscular-blockade debate (§12).
Right ventricular dysfunction / acute cor pulmonale ⚠️ — present in ~20-25% of moderate-severe ARDS; a mechanistically distinct "RV-protective" management strand.
Barotrauma / pneumothorax ⚠️ HP:0002107 (Pneumothorax) — verify. Quantified in the ART trial (PMID:28973363): "increased the risk of pneumothorax requiring drainage (3.2% vs 1.2%...) and the risk of barotrauma (5.6% vs 1.6%...)".

Laboratory abnormalities (LOINC-codable)

PaO₂/FiO₂ ratio ≤300 mmHg (LOINC 50984-4 ⚠️) — the defining measure
SpO₂/FiO₂ ratio ≤315 — the new global-definition surrogate
Elevated plasma IL-6, IL-8 (CXCL8), sTNFR-1, sRAGE, angiopoietin-2, PAI-1, surfactant protein D, ferritin
Reduced protein C
Elevated bronchoalveolar lavage protein / oedema-fluid-to-plasma protein ratio >0.65 (the classic bedside discriminator of non-cardiogenic oedema)
Reduced serum bicarbonate, elevated lactate

These belong in a biochemical: block with BiomarkerReadout links — the entry already has one; adding reference_ranges with interpretation_bands would be a natural extension, though most ARDS biomarkers lack consensus clinical cut-points (flag rather than invent).

Long-term / survivorship phenotypes

This is where the durable morbidity lives. From PMID:21470008 (Herridge et al., N Engl J Med 2011;364:1293-304, "Functional disability 5 years after acute respiratory distress syndrome"):

"At 5 years, the median 6-minute walk distance was 436 m (76% of predicted distance) and the Physical Component Score on the Medical Outcomes Study 36-Item Short-Form Health Survey was 41 (mean norm score matched for age and sex, 50)."

"With respect to this score, younger patients had a greater rate of recovery than older patients, but neither group returned to normal predicted levels of physical function at 5 years. Pulmonary function was normal to near-normal."

"Exercise limitation, physical and psychological sequelae, decreased physical quality of life, and increased costs and use of health care services are important legacies of severe lung injury."

The striking finding — pulmonary function normalises but physical function does not — is a first-class curation point: the long-term disability of ARDS is largely extrapulmonary (muscle wasting, neuropathy, cognitive impairment, PTSD/depression/anxiety, i.e. post-intensive-care syndrome), not a residual lung defect. QoL instruments in the literature: SF-36 (Physical and Mental Component Scores), EQ-5D, HADS, IES-R, and the 6-minute walk test as a functional endpoint.

4. Genetic / Molecular Information

Causal genes: none. ARDS has no Mendelian form and no OMIM entry. Do not curate relationship_type: CAUSATIVE gene relationships.

Pathogenic variants: not applicable. There is no ACMG/AMP variant classification framework for ARDS; ClinVar contains no ARDS-associated pathogenic variants. All genetic contributions are common-variant susceptibility alleles (MAF typically >5%) with odds ratios in the 1.2-1.5 range — see the BORCS5/DUSP16 OR of 1.38 (PMID:34032881). Somatic variation plays no role.

For the genetic: block, curate as susceptibility rather than causation:

Gene	HGNC (⚠️ verify all)	Relationship type	Evidence tier
FLT1	`hgnc:3763`	`SUSCEPTIBILITY`	GWAS-significant; functional support via sFLT1/VEGF
BORCS5	⚠️	`SUSCEPTIBILITY`	GWAS-significant locus 12p13.2 (rs7967111), European ancestry only
DUSP16	⚠️	`SUSCEPTIBILITY`	same locus; MAPK phosphatase — mechanistically plausible
ACE	`hgnc:2707` ⚠️	`SUSCEPTIBILITY`	candidate-gene era, inconsistent replication
SFTPB	⚠️	`SUSCEPTIBILITY`	candidate-gene era; watch for neonatal-RDS confusion
NFE2L2	⚠️	`MODIFIER`	oxidative-stress response
TMEM176B, SLC2A5, CDC45, VSIG8	⚠️	`SUSCEPTIBILITY`	MR-nominated + transcriptionally validated (PMID:37922010)

Modifier genes: the concept applies loosely — most reported loci modify severity/mortality rather than incidence, and the two are rarely separated cleanly in the literature.

Epigenetics. DNA methylation and histone-modification changes have been described in ARDS and sepsis leukocytes (notably at HIF1A, TNF, and interferon-response loci) and NET-derived extracellular histones are directly cytotoxic to pulmonary endothelium (§6). ENCODE/Roadmap have no ARDS-specific tracks; the useful epigenomic resources are sepsis leukocyte methylome studies. [unquoted]

Chromosomal abnormalities: not applicable.

Pharmacogenomics: no established ARDS pharmacogenomic markers. The closest analogue is predictive enrichment by subphenotype rather than by genotype (§12, HARP-2/simvastatin).

5. Environmental Information

This section is entirely absent from the current KB entry and is one of the clearest gaps. Candidate environmental: entries, each needing an influences_mechanisms link to a named pathophysiology node (remember: bare-name targets, not pathophysiology#Name):

Exposure	Suggested target node	`environmental_effect`	ECTO candidate
Gastric-contents aspiration	Direct Pulmonary or Indirect Systemic Insult	`TRIGGERS`	⚠️ search ECTO for aspiration; may be unbindable
Smoke inhalation	Direct Pulmonary or Indirect Systemic Insult	`TRIGGERS`	⚠️ ECTO "exposure to smoke"
Chronic alcohol consumption	Alveolar-Capillary Barrier Disruption	`PREDISPOSES`	⚠️ ECTO ethanol exposure
Cigarette smoking	Alveolar Macrophage and Cytokine Activation	`PREDISPOSES`	⚠️ check for an existing tobacco/cigarette binding elsewhere in the KB — run `just environmental-term-audit` for reuse candidates
Ambient particulate matter / ozone	Neutrophil Oxidative and Proteolytic Injury	`PREDISPOSES`	⚠️ ECTO air-pollutant exposure
Chlorine / phosgene inhalation	Direct Pulmonary or Indirect Systemic Insult	`TRIGGERS`	⚠️
Hyperoxia (high FiO₂)	Neutrophil Oxidative and Proteolytic Injury	`EXACERBATES`	⚠️ ECTO oxygen exposure
High tidal volume mechanical ventilation	Ventilator-Induced Lung Injury	`EXACERBATES`	likely unbindable — record the ECTO search in `review_notes:`
Blood-product transfusion (TRALI)	Alveolar-Capillary Barrier Disruption	`TRIGGERS`	⚠️

Repo-specific caution: check-environmental-evidence is now a hard gate — every environmental[] entry needs its own top-level evidence: block (evidence on influences_mechanisms does not count), or a review_notes: beginning with the exact sentence Left deliberately uncited. followed by ≥20 words describing the searches run.

Lifestyle factors

Alcohol use disorder, smoking, obesity (paradoxically associated with lower ARDS mortality in several cohorts — the "obesity paradox"), malnutrition/hypoalbuminaemia, and vitamin D status. [unquoted]

Infectious agents

ARDS is the most common severe endpoint of lower respiratory tract infection. Organisms to consider for NCBITaxon binding:

Agent	NCBITaxon (⚠️ verify)	Note
Streptococcus pneumoniae	1313	Leading bacterial cause; the repo has `Pneumococcal_Pneumonia.yaml`
SARS-CoV-2	2697049	The dominant ARDS cause 2020-2022; drove the global-definition revision
Influenza A virus	11320	Seasonal and pandemic ARDS
Legionella pneumophila	446
Staphylococcus aureus	1280	Including community-acquired MRSA necrotising pneumonia
Pneumocystis jirovecii	42068	The repo has `Pneumocystis_Pneumonia.yaml`
MERS-CoV	1335626	The repo has `Middle_East_Respiratory_Syndrome.yaml`
Respiratory syncytial virus	11250	Repo entry exists
Human metapneumovirus	162145	Repo entry exists
Mycoplasma pneumoniae	2104	Repo entry exists

This is a large comorbidity-curation opportunity: ARDS is the shared severe outcome of at least six diseases already in kb/disorders/. A Grouping (e.g. "ARDS-precipitating infections") or a set of sequelae edges from each infection entry to the ARDS entry would make that convergence machine-queryable.

Non-infectious triggers that reach the same node: acute pancreatitis, polytrauma, burns, cardiopulmonary bypass, amniotic fluid embolism.

6. Mechanism / Pathophysiology

The ordered causal chain

The mechanism is best read as a single trunk with three branches at the outcome. Steps marked [inferred] are extrapolated from model systems or human autopsy rather than demonstrated longitudinally in living patients.

A direct pulmonary or indirect systemic insult delivers PAMPs and/or DAMPs to the alveolar-capillary interface, either from the airspace side (pneumonia, aspirate, inhaled toxicant) or the vascular side (bacteraemia, circulating cytokines, activated neutrophils from a distant injury). → leads to
Pattern-recognition receptor engagement on alveolar macrophages and alveolar epithelium — TLR4 (LPS), TLR2, TLR3/7/9 (viral nucleic acid), RAGE, and NLRP3 inflammasome assembly — activates NF-κB and drives transcription of TNF, IL-1β, IL-6, IL-8/CXCL8, and IL-18. → results in
Chemokine-gradient-driven recruitment and margination of circulating neutrophils into the pulmonary microvasculature and then the alveolar space. The lung's capillary bed is narrower than a neutrophil, so this step is partly mechanical: activated, stiffened neutrophils are physically retained. → results in
Neutrophil degranulation and NETosis, releasing myeloperoxidase, neutrophil elastase, matrix metalloproteinases, reactive oxygen and nitrogen species, and extracellular chromatin decorated with citrullinated histones. → causes, in parallel:
4a. Proteolytic and oxidative destruction of endothelial tight and adherens junctions (VE-cadherin, occludin, claudin-5) and shedding of the endothelial glycocalyx (syndecan-1, heparan sulphate), via heparanase and MMPs. Extracellular histones from NETs are directly cytotoxic to pulmonary endothelial cells. [inferred, mostly in vitro/model]
4b. Injury and death of alveolar epithelium, disproportionately the thin, gas-exchanging type I pneumocytes (which cover ~95% of alveolar surface and are poorly regenerative), with necrosis, apoptosis, and pyroptosis.
Loss of alveolar-capillary barrier integrity — the two surfaces fail together, and the barrier's normal 1-µm-thick sandwich becomes leaky in both directions. → results in
Flooding of the alveolar space with protein-rich oedema fluid (oedema-fluid/plasma protein ratio >0.65), because plasma proteins now cross freely and the oncotic gradient that normally keeps the airspace dry is abolished. → compounded by
Failure of alveolar fluid clearance: injured type II pneumocytes lose apical ENaC and basolateral Na⁺/K⁺-ATPase function, so the pump that would drain the alveolus is disabled at exactly the moment the leak opens. Impaired clearance is one of the strongest single predictors of death. [inferred from ex vivo human lung and clinical oedema-fluid sampling]
Type II pneumocyte injury also collapses surfactant production and increases surfactant inactivation by plasma proteins, raising alveolar surface tension. → leads to
Alveolar collapse and de-recruitment, most severe in dependent lung regions (gravitational superimposed pressure) → the "baby lung": a small volume of aerated, compliant tissue receiving the whole tidal volume.
Intrapulmonary shunt — perfused but unventilated alveoli — plus dead-space ventilation from microvascular thrombosis, giving severe hypoxaemia refractory to supplemental oxygen and reduced respiratory-system compliance. This is the clinical syndrome.
In parallel from step 4: intra-alveolar coagulation. Tissue factor from injured epithelium and alveolar macrophages initiates extrinsic coagulation in the airspace; PAI-1 rises and protein C falls, suppressing fibrinolysis. → fibrin-rich hyaline membranes line the alveolar ducts — the pathological hallmark of diffuse alveolar damage.
Mechanical ventilation feeds back into step 4 (ventilator-induced lung injury). Because the aerated compartment is small, a "normal" tidal volume delivers regional overdistension (volutrauma) while repeated opening and closing of unstable units produces shear injury (atelectrauma); both amplify cytokine release (biotrauma), which spills systemically. This is the loop that low-tidal-volume ventilation breaks — and the reason the single most effective ARDS therapy is a reduction in intervention.
Systemic spillover of alveolar cytokines and translocated bacterial products drives distal organ injury — kidney, liver, brain — producing multiple organ dysfunction syndrome, which is what most ARDS patients actually die of.
Branch point at ~day 7. Three trajectories:
- 14a. Resolution. Pro-resolving mediators (lipoxins, resolvins, protectins), macrophage efferocytosis of apoptotic neutrophils, macrophage repolarisation toward a reparative phenotype, restored ENaC/Na⁺-K⁺-ATPase-mediated fluid clearance, and type II pneumocyte proliferation and transdifferentiation into type I cells to re-epithelialise the denuded basement membrane. Note the asymmetry: the AT2 cell is both a primary victim and the progenitor responsible for repair.
- 14b. Fibroproliferation. Persistent injury, TGF-β signalling, fibroblast recruitment and myofibroblast differentiation, collagen deposition in the alveolar septa and airspace → organising fibrosis, persistent low compliance, ventilator dependence. Candidate conforms_to target: the fibrotic_response module.
- 14c. Death, usually from refractory MODS or the underlying precipitant, not from refractory hypoxaemia (which accounts for only a minority of ARDS deaths).

Mapping to the existing KB nodes

The existing 11 pathophysiology nodes cover this chain well. Mapping:

Chain step	Existing node
1	Direct Pulmonary or Indirect Systemic Insult (`biological_scale: TISSUE`)
2	Alveolar Macrophage and Cytokine Activation (CELLULAR)
3-4	Neutrophil Oxidative and Proteolytic Injury (CELLULAR)
(metabolic layer)	Immunometabolic Reprogramming and Mitochondrial Dysfunction (CELLULAR)
12	Ventilator-Induced Lung Injury (TISSUE)
5	Alveolar-Capillary Barrier Disruption (TISSUE)
11	Intra-Alveolar Coagulation and Fibrin Deposition (TISSUE)
6-9	Protein-Rich Alveolar Edema and Loss of Aerated Lung (TISSUE)
10	Shunt Physiology and Hypoxemic Respiratory Failure (ORGANISM)
14a	Resolution and Alveolar Repair (TISSUE)
14b	Fibroproliferative Remodeling and Fibrosis (TISSUE)

Gaps in the current node set worth considering: step 7 (impaired alveolar fluid clearance / ENaC–Na⁺-K⁺-ATPase failure) and step 8 (surfactant dysfunction) are currently folded into the oedema node but are mechanistically distinct, separately measurable, and separately druggable (β₂-agonists targeted step 7; exogenous surfactant targeted step 8 — both failed in trials, which is itself informative). Step 13 (systemic spillover → MODS) has no node, despite being the dominant cause of death.

Molecular pathways (GO / KEGG / Reactome)

Process	GO term	Cache status
inflammatory response	`GO:0006954`	✅
toll-like receptor 4 signaling pathway	`GO:0034142`	✅
toll-like receptor signaling pathway	`GO:0002224`	✅
NLRP3 inflammasome complex assembly	`GO:0044546`	✅
NLRP3 inflammasome complex (CC)	`GO:0072559`	✅
neutrophil chemotaxis	`GO:0030593`	✅
leukocyte migration involved in inflammatory response	`GO:0002523`	✅
cytokine production involved in inflammatory response	`GO:0002534`	✅
interleukin-6 production	`GO:0032635`	✅
tumor necrosis factor production	`GO:0032640`	✅
cytokine-mediated signaling pathway	`GO:0019221`	✅
response to oxidative stress	`GO:0006979`	✅
coagulation	`GO:0050817`	✅
surfactant homeostasis	`GO:0043129`	✅
fibroblast proliferation	`GO:0048144`	✅
extracellular matrix organization	`GO:0030198`	✅
extracellular matrix disassembly	`GO:0022617`	✅
wound healing	`GO:0042060`	✅
positive regulation of NF-κB transcription factor activity	⚠️ `GO:0043123` (label: positive regulation of canonical NF-kappaB signal transduction)	verify
neutrophil extracellular trap formation	⚠️ `GO:1990266`?	verify
sodium ion transmembrane transport / ENaC	⚠️	verify
efferocytosis / apoptotic cell clearance	⚠️ `GO:0043277`?	verify

KEGG/Reactome anchors (not dismech-bound, but useful for the report): KEGG hsa04620 (Toll-like receptor signaling), hsa04064 (NF-κB signaling), hsa04621 (NOD-like receptor signaling), hsa04610 (Complement and coagulation cascades), hsa04370 (VEGF signaling), hsa04350 (TGF-β signaling); Reactome R-HSA-168256 (Immune System), R-HSA-140877 (Formation of Fibrin Clot).

Cellular processes and cell types

Cell type	CL term	Cache status	Role
alveolar macrophage	`CL:0000583`	✅	Sentinel; PRR sensing; cytokine amplification; later, efferocytosis and repair
neutrophil	`CL:0000775`	✅	Principal effector of tissue destruction; NETosis
pulmonary alveolar type 1 cell	`CL:0002062`	✅	Gas exchange surface; primary casualty; poorly regenerative
pulmonary alveolar type 2 cell	`CL:0002063`	✅	Surfactant production; ENaC-mediated fluid clearance; progenitor for AT1 repair
pulmonary alveolar epithelial cell (generic)	`CL:0000322`	✅	Use when AT1/AT2 not distinguished
capillary endothelial cell	`CL:0002144`	✅	Barrier; glycocalyx; adhesion-molecule display
fibroblast of lung	`CL:0002553`	✅	Fibroproliferative phase
myofibroblast cell	`CL:0000186`	✅	Collagen deposition
platelet	`CL:0000233`	✅	Platelet-neutrophil aggregates; microthrombosis
monocyte	`CL:0000576`	✅	Recruited; differentiates into inflammatory macrophage

Cellular processes: pyroptosis, necroptosis, apoptosis, NETosis, efferocytosis, epithelial-mesenchymal transition (contested in ARDS), autophagy, ferroptosis (an active 2023-2025 research area in ALI models — [unquoted]), mitochondrial dysfunction and metabolic reprogramming toward aerobic glycolysis in alveolar macrophages.

Protein dysfunction, metabolic changes, biochemical abnormalities

Surfactant proteins B and C: reduced production and functional inactivation by leaked plasma proteins → raised alveolar surface tension.
VE-cadherin / claudin-5 / occludin / ZO-1: junctional disassembly under RhoA/ROCK signalling and tyrosine phosphorylation.
Angiopoietin-2 vs Angiopoietin-1 / Tie2: Ang-2 rises, antagonises Ang-1's barrier-stabilising Tie2 signal. Ang-2 is among the best-performing ARDS biomarkers.
RAGE (AGER): soluble RAGE released from injured AT1 cells — a relatively specific marker of alveolar epithelial injury.
Endothelial glycocalyx: heparanase- and MMP-mediated shedding; syndecan-1 as the circulating marker.
Tissue factor ↑, protein C ↓, PAI-1 ↑, thrombomodulin shed: the procoagulant/antifibrinolytic shift in the airspace.
ENaC (SCNN1A/B/G) and Na⁺/K⁺-ATPase (ATP1A1/ATP1B1): downregulated/internalised → alveolar fluid clearance failure.
Metabolic: alveolar macrophage glycolytic switch; mitochondrial ROS; released mitochondrial DNA acting as a DAMP via TLR9 and cGAS-STING (the repo has a cgas_sting_pathway_activation module — a plausible additional conformance target).

Immune system involvement

ARDS is a disorder of dysregulated innate immunity — not autoimmunity and not immunodeficiency, though both can precipitate it. The central tension is that the neutrophil response required to clear a pathogen is the same response that destroys the barrier; the syndrome is what happens when that response is neither proportionate nor properly terminated. Resolution failure — not just excess activation — is increasingly seen as the therapeutic target (PMID:36070787: "Resolution of inflammation is a coordinated process that requires downregulation of proinflammatory pathways and upregulation of anti-inflammatory pathways.").

Adaptive immunity contributes via regulatory T cells (which promote resolution and AT2 proliferation in murine models) and, in viral ARDS, via CD8⁺ T-cell-mediated epithelial killing. The repo's cytokine_storm_hyperinflammation module is a candidate conformance target for the hyperinflammatory subphenotype specifically.

Tissue damage mechanisms

Oxidative stress (neutrophil NADPH oxidase, MPO-derived hypochlorous acid, mitochondrial ROS, hyperoxia), proteolysis (elastase, MMP-2/9), mechanical strain (volutrauma, atelectrauma), microvascular thrombosis with regional ischaemia, complement activation (C5a), and — in the late phase — fibrosis.

Subphenotypes: the dominant modern framework

This is the single most consequential idea in ARDS biology since low-tidal-volume ventilation, and it deserves its own mechanistic_hypotheses treatment. From PMID:24853585 (Calfee et al., Lancet Respir Med 2014;2:611-20):

"Independent latent class models indicated that a two-class (ie, two subphenotype) model was the best fit for both cohorts. In both cohorts, we identified a hyperinflammatory subphenotype (phenotype 2) that was characterised by higher plasma concentrations of inflammatory biomarkers, a higher prevalence of vasopressor use, lower serum bicarbonate concentrations, and a higher prevalence of sepsis than phenotype 1."

"In the ALVEOLI cohort, the effects of ventilation strategy (high PEEP vs low PEEP) on mortality, ventilator-free days and organ failure-free days differed by phenotype (p=0·049 for mortality, p=0·018 for ventilator-free days, p=0·003 for organ-failure-free days)."

Replicated in a non-US population with a pharmacological treatment interaction (PMID:30078618, Calfee et al., Lancet Respir Med 2018;6:691-698):

"a two-class (two subphenotype) model was an improvement over a one-class model (p<0·0001), with 353 (65%) patients in the hypoinflammatory subphenotype group and 186 (35%) in the hyperinflammatory subphenotype group."

"Patients with the hyperinflammatory subphenotype had fewer ventilator-free days (median 2 days [IQR 0-17] vs 18 [IQR 0-23]; p<0·0001), fewer non-pulmonary organ failure-free days (15 [0-25] vs 27 [21-28]; p<0·0001), and higher 28-day mortality (73 [39%] vs 59 [17%]; p<0·0001) than did those with the hypoinflammatory subphenotype."

"Although HARP-2 found no difference in 28-day survival between placebo and simvastatin, significantly different survival was identified across patients stratified by treatment and subphenotype (p<0·0001). Specifically, within the hyperinflammatory subphenotype, patients treated with simvastatin had significantly higher 28-day survival than did those given placebo (p=0·008)."

That last result is the field's proof of concept for predictive enrichment: a drug that "failed" in the whole population worked in a third of it.

A 2025 EHR-scale replication in MIMIC-IV (24,363 ICU admissions) reported 90-day mortality of 40.8% (hyperinflammatory) vs 19.1% (hypoinflammatory), adjusted OR 2.19 (95% CI 2.05-2.35), with invasive ventilation in 80.0% vs 37.5% (adjusted OR 5.67, 95% CI 5.32-6.04). [unquoted — ATS 2025 abstract A26-18; retrieve the peer-reviewed version before citing]

Complementary phenotyping axes to record as separate hypothesis groups: - Transcriptomic: "reactive" vs "uninflamed" (Bos et al.) — largely concordant with the LCA classes. [unquoted] - Radiographic/physiologic: focal vs diffuse loss of aeration, with a reported (and contested) differential response to recruitment. [unquoted] - Direct vs indirect insult: distinct biomarker profiles (higher sRAGE/SP-D in direct, higher Ang-2/vWF in indirect). [unquoted] - COVID-19 vs non-COVID ARDS: initially claimed as a distinct entity ("L" vs "H" phenotypes); the ESICM guideline's position is that COVID-19 ARDS should be managed as ARDS. The mechanistic distinctions that survived scrutiny are the degree of pulmonary microthrombosis and the duration of the illness.

Molecular profiling

Transcriptomics: whole-blood RNA-seq/microarray from ARDS and sepsis cohorts (GEO — search "ARDS", "acute lung injury", "sepsis whole blood"). The repo's datasets: block for ARDS is empty; just discover-datasets Acute_Respiratory_Distress_Syndrome followed by manual relevance triage is the right first move. Watch the Named Entity Confusion trap: searching "RDS" or surfactant genes will surface neonatal RDS cohorts.
Single-cell: the Human Cell Atlas lung and several COVID-19 autopsy atlases (e.g. Delorey et al., Melms et al., Nature 2021) provide alveolar-cell-resolution ARDS data, including the description of transitional/aberrant basaloid AT2-derived states in fibrotic lung. [unquoted]
Proteomics: plasma and BAL/oedema-fluid proteomics from ARDSNet biorepositories; PRIDE/ProteomeXchange deposits exist.
Metabolomics/lipidomics: eicosanoid and specialised pro-resolving mediator profiling in BAL; Metabolomics Workbench holds sepsis/ARDS studies. [unquoted]
Functional genomics screens: no ARDS-specific CRISPR screens; endothelial-barrier and inflammasome screens are the closest proxies.

7. Anatomical Structures Affected

Organ level

Primary organ: lung (UBERON:0002048 ✅), bilaterally and by definition — unilateral opacities do not satisfy any ARDS definition. Injury is bilateral but spatially heterogeneous, with a gravitational gradient: dependent (dorsal, in a supine patient) regions collapse and consolidate while non-dependent regions remain aerated and are preferentially overdistended by positive-pressure ventilation. This spatial asymmetry is the entire rationale for prone positioning.

Relevant UBERON terms:

Structure	UBERON	Cache
lung	`UBERON:0002048`	✅
alveolus of lung	`UBERON:0002299`	✅
lung parenchyma	`UBERON:0008946`	✅
lung epithelium	`UBERON:0000115`	✅
pulmonary capillary	`UBERON:0016405`	✅
lung mesenchyme	`UBERON:0004883`	✅
lung connective tissue	`UBERON:0000114`	✅
respiratory system	`UBERON:0001004`	✅
diaphragm	`UBERON:0001103`	✅ (relevant to ventilator-induced diaphragmatic dysfunction)
blood-air barrier / alveolar septum	⚠️ `UBERON:0004802`? verify

Secondary organ involvement: kidney (AKI in ~40-50%), cardiovascular system (shock; right ventricular strain and acute cor pulmonale from hypoxic vasoconstriction plus raised transpulmonary pressure), brain (delirium, later cognitive impairment), liver (shock liver, cholestasis), skeletal muscle (ICU-acquired weakness), gut (barrier failure and translocation, both cause and consequence), and haematologic (DIC).

Body systems: respiratory (primary), cardiovascular, renal, nervous, musculoskeletal, immune/haematologic.

Tissue and cell level

Alveolar epithelium (simple squamous AT1 + cuboidal AT2), pulmonary capillary endothelium, alveolar basement membrane, interstitial connective tissue, and — in the fibroproliferative phase — interstitial fibroblasts/myofibroblasts. Airway epithelium proximal to the alveolus is relatively spared in indirect ARDS but heavily involved in inhalational and aspiration injury. See the CL table in §6.

Subcellular level

Compartment	GO CC (⚠️ verify all)	Relevance
mitochondrion	`GO:0005739`	ROS, mtDNA release as DAMP, metabolic reprogramming
lamellar body	`GO:0042599`	Surfactant storage in AT2 cells
NLRP3 inflammasome complex	`GO:0072559` ✅	Caspase-1 activation, IL-1β maturation
tight junction	`GO:0005923`	Barrier
adherens junction	`GO:0005912`	VE-cadherin
cell surface / glycocalyx	⚠️	Syndecan/heparan sulphate shedding
endoplasmic reticulum	`GO:0005783`	ER stress in injured epithelium
extracellular matrix	`GO:0031012` ✅	Basement membrane denudation, later collagen deposition

Localization and lateralization

Bilateral, by definition. Distribution within each lung is heterogeneous and gravity-dependent; CT typically shows a dorsobasal gradient from normally aerated (ventral) → ground-glass → dense consolidation (dorsal). Direct-insult ARDS tends toward more focal, asymmetric consolidation; indirect ARDS toward diffuse, symmetric ground-glass. This distinction is the basis of the focal/diffuse morphological phenotype.

8. Temporal Development

Onset

Age: any age from neonate to elderly, but incidence rises steeply with age (PMID:16236739: 16 → 306 per 100,000 person-years from ages 15-19 to 75-84). Paediatric ARDS is defined separately (PALICC-2).
Pattern: acute, by definition. The Berlin and Global definitions require onset within one week of a known clinical insult or new/worsening respiratory symptoms. In practice, from LUNG SAFE, most ARDS is present early: "more than 75% being diagnosed with ARDS in the first 48 hours of admission to the ICU" [from search summary of the companion paper PMID:27608629 — unquoted]. From LIPS (PMID:20802164): "ALI developed a median of 2 (interquartile range 1-4) days after initial evaluation."
Suggested OnsetDescriptor: onset_category acute; temporality: ACUTE.

Stages

The classical three overlapping histopathological phases of diffuse alveolar damage:

Exudative phase (days 0-7). Interstitial and alveolar oedema, neutrophil infiltration, hyaline membranes, capillary congestion, AT1 necrosis. Maximal hypoxaemia and lowest compliance.
Proliferative phase (days ~7-21). AT2 hyperplasia, fibroblast and myofibroblast proliferation, organisation of intra-alveolar exudate, granulation tissue. Oedema begins to clear; dead space stays high.
Fibrotic phase (≥ ~2-3 weeks, in a subset). Collagen deposition, architectural distortion, cyst formation, honeycombing on CT. Associated with prolonged ventilation and higher mortality.

These are overlapping, not sequential, and coexist regionally within the same lung. Many patients never reach phase 3.

Progression rate and course

Rapid: severity is usually maximal within the first 24-72 hours.
Course pattern: acute, self-limited-or-fatal rather than relapsing or chronic. There is no "relapsing-remitting ARDS."
Duration: median duration of mechanical ventilation in survivors, by Berlin stratum (PMID:22797452): "increased median duration of mechanical ventilation in survivors (5 days; interquartile [IQR], 2-11; 7 days; IQR, 4-14; and 9 days; IQR, 5-17, respectively; P < .001)" for mild, moderate, and severe.

Remission patterns

Recovery is treatment-supported rather than spontaneous in most cases — the intervention keeps the patient alive while the resolution machinery (step 14a) does the actual work. Pulmonary function typically recovers to normal or near-normal by 6-12 months (PMID:21470008: "Pulmonary function was normal to near-normal"), while physical function does not.

Critical periods

The pre-ARDS window (hours to ~2 days from the precipitating insult): the only interval in which primary prevention is possible — this is the target of LIPS-based enrichment and of prophylactic lung-protective ventilation.
First 48 hours of ARDS: the window in which prone positioning (PROSEVA enrolled within 36 h of ARDS onset), neuromuscular blockade (ACURASYS: within 48 h), and low-tidal-volume ventilation deliver their benefit.
~24 hours of established moderate-severe ARDS: the DEXA-ARDS enrolment window for dexamethasone.
Day 7-14: the branch point between resolution and fibroproliferation; the theoretical window for antifibrotic intervention, currently with no proven therapy.

9. Inheritance and Population

Epidemiology

Incidence. The two anchor estimates:

United States, population-based (PMID:16236739, Rubenfeld et al., N Engl J Med 2005;353:1685-93):

"the crude incidence of acute lung injury was 78.9 per 100,000 person-years and the age-adjusted incidence was 86.2 per 100,000 person-years."

"We estimate that each year in the United States there are 190,600 cases of acute lung injury, which are associated with 74,500 deaths and 3.6 million hospital days."

Note this is acute lung injury under the pre-Berlin AECC definition and therefore includes what is now "mild ARDS"; it is not directly comparable to Berlin-ARDS incidence, and later US estimates using narrower criteria run lower (~34-64 per 100,000 person-years). [unquoted] Record this definitional caveat in notes: — comparing incidences across definitions is one of the easiest errors to make here.

ICU period prevalence — the LUNG SAFE benchmark (PMID:26903337, Bellani et al., JAMA 2016;315:788-800):

"Of 29,144 patients admitted to participating ICUs, 3022 (10.4%) fulfilled ARDS criteria."

"The period prevalence of mild ARDS was 30.0% (95% CI, 28.2%-31.9%); of moderate ARDS, 46.6% (95% CI, 44.5%-48.6%); and of severe ARDS, 23.4% (95% CI, 21.7%-25.2%). ARDS represented 0.42 cases per ICU bed over 4 weeks and represented 10.4% (95% CI, 10.0%-10.7%) of ICU admissions and 23.4% of patients requiring mechanical ventilation."

Suggested prevalence: records (structured slots, not the deprecated percentage):

prevalence:
- population: ICU admissions, 459 ICUs in 50 countries (LUNG SAFE)
  measure_type: PERIOD_PREVALENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 10400.0
  notes: 10.4% of ICU admissions over 4 consecutive weeks, winter 2014.
- population: United States adults (King County, WA; AECC acute lung injury)
  measure_type: ANNUAL_INCIDENCE
  prevalence_class: BAND_1_5_PER_10000
  rate_per_100000: 78.9
  notes: >-
    Crude incidence; age-adjusted 86.2 per 100,000 person-years. AECC-era
    acute lung injury, broader than Berlin ARDS.

Do not mix these two — one is a period prevalence among ICU patients, the other an annual population incidence. The measure_type slot exists precisely to keep them apart.

For genetic etiology

Inheritance pattern: multifactorial / polygenic. Suggested binding: HP:0010982 Polygenic inheritance ⚠️.
Penetrance, expressivity, anticipation, germline mosaicism, founder effects, carrier frequency: not applicable. ARDS has no Mendelian form. Do not populate these slots.
Ancestry heterogeneity is real and documented (PMID:34032881: "There was distinct genetic heterogeneity in ARDS between Europeans and African Americans") — record this rather than a founder-effect claim.
Consanguinity: not applicable.

Population demographics

Sex: male predominance in most cohorts (roughly 55-60% male), partly reflecting the sex distribution of the precipitating insults (trauma, alcohol-related illness). The ART trial cohort was "37.5% female" (PMID:28973363) — typical.
Age: median around 50-60 in trial cohorts; incidence and mortality both rise with age (PMID:16236739: "Mortality increased with age from 24 percent for patients 15 through 19 years of age to 60 percent for patients 85 years of age or older (P<0.001)").
Geographic distribution: worldwide. Recognised and reported ARDS incidence is strongly confounded by ICU-bed availability, ventilator access, and diagnostic capability — which is precisely why the Global Definition added a resource-limited category. Reported ICU incidence is far lower in low-income settings, and this is at least partly ascertainment, not biology.
Ethnic groups: no established incidence difference attributable to ancestry; documented outcome disparities in US cohorts. [unquoted]

10. Diagnostics

ARDS is a clinical-syndromic diagnosis. There is no confirmatory test. Everything below either establishes the syndromic criteria, excludes mimics, or identifies the precipitant.

Clinical criteria (the actual diagnostic instrument)

New Global Definition (2024, PMID:37487152) — all four required: 1. Timing: within 1 week of a known insult or new/worsening respiratory symptoms 2. Oxygenation: PaO₂/FiO₂ ≤300 mmHg, or SpO₂/FiO₂ ≤315 when SpO₂ ≤97% 3. Imaging: bilateral opacities on chest radiograph, CT, or lung ultrasound, not fully explained by effusion, collapse, or nodules 4. Origin of oedema: respiratory failure not fully explained by cardiac failure or fluid overload 5. Respiratory support: invasive MV; or HFNO ≥30 L/min; or NIV/CPAP with PEEP ≥5 cmH₂O; or, in resource-limited settings, no support requirement at all

Berlin severity strata retained for intubated patients (PMID:22797452): mild 200<P/F≤300, moderate 100<P/F≤200, severe P/F≤100 (all at PEEP ≥5).

Recognition is poor in practice — a genuinely important clinical-burden finding (PMID:26903337):

"Clinical recognition of ARDS ranged from 51.3% (95% CI, 47.5%-55.0%) in mild to 78.5% (95% CI, 74.8%-81.8%) in severe ARDS."

"This syndrome appeared to be underrecognized and undertreated and associated with a high mortality rate."

Laboratory tests

Arterial blood gas — PaO₂, PaCO₂, pH; the source of the P/F ratio. LOINC: 2703-7 (PaO₂), 2019-8 (PaCO₂), 11557-6 (pH) ⚠️ verify.
Pulse oximetry (SpO₂) — now a definitional alternative; note the systematic overestimation of oxygen saturation in patients with darker skin pigmentation, which has direct diagnostic-equity implications for the SpO₂/FiO₂ criterion. [unquoted — an important and citable 2020-2022 literature]
B-type natriuretic peptide (BNP/NT-proBNP) — to help exclude cardiogenic oedema; imperfect, since BNP rises in critical illness generally.
Full blood count, lactate, procalcitonin, blood/sputum cultures, respiratory viral PCR panel — for the precipitant.
Bronchoalveolar lavage — cell differential (neutrophil predominance), microbiology, and exclusion of alveolar haemorrhage or eosinophilic pneumonia.
Oedema-fluid-to-plasma protein ratio >0.65 — the classic bedside discriminator of increased-permeability from hydrostatic oedema. Underused, but conceptually central.

Biomarkers

None are validated for diagnosis; all are research/prognostic tools:

Biomarker	Compartment injured	Note
sRAGE (soluble receptor for advanced glycation end products)	AT1 epithelium	Highest in direct-insult ARDS
Surfactant protein D (SP-D)	AT2 epithelium
Angiopoietin-2	Endothelium	Among the best-performing single markers
von Willebrand factor antigen	Endothelium
IL-6, IL-8 (CXCL8), sTNFR-1	Inflammation	The core of the LCA subphenotype classifiers
PAI-1	Coagulation/fibrinolysis
Protein C (reduced)	Coagulation
Ferritin	Hyperinflammation	Proposed as a practical hyperinflammatory-class marker (PMC10980828) [unquoted]
Club cell protein 16 (CC16)	Airway epithelium

Parsimonious 3-variable classifiers (IL-8, bicarbonate, sTNFR-1) can assign subphenotype at the bedside — the enabling step for prospective enrichment trials. [unquoted]

Imaging

Chest radiograph — bilateral opacities; poor inter-observer reliability, which was a known Berlin-definition weakness.
Chest CT — the reference for distribution (focal vs diffuse), for complications (pneumothorax, abscess, PE), and for the fibroproliferative phase. Reveals the "baby lung."
Lung ultrasound — now an accepted imaging modality under the Global Definition; B-lines, subpleural consolidation, pleural-line abnormalities. Its inclusion is the change with the biggest practical effect in resource-limited settings.
Echocardiography — to assess LV function (excluding cardiogenic oedema) and RV size/function (acute cor pulmonale).
Electrical impedance tomography (EIT) — research/emerging bedside regional ventilation monitoring, used for PEEP titration.

Functional and physiologic tests

Respiratory system compliance (C_rs = Vt/(Pplat − PEEP)), driving pressure (ΔP = Pplat − PEEP; the ventilation variable most strongly associated with survival), plateau pressure, oesophageal manometry for transpulmonary pressure, dead-space fraction (V_D/V_T; strongly prognostic), oxygenation index (OI, used in paediatrics), and the recruitment-to-inflation ratio.

Biopsy and pathology

Open lung biopsy is rarely performed and is reserved for cases where an alternative treatable diagnosis is suspected. The histological correlate is diffuse alveolar damage (DAD): hyaline membranes, alveolar and interstitial oedema, capillary congestion, AT1 necrosis, later AT2 hyperplasia and interstitial fibroproliferation.

A curation-critical caveat: DAD is present in only roughly half of clinically defined ARDS at autopsy. From PMID:30872586: "Pathological specimens from patients with ARDS frequently reveal diffuse alveolar damage" — note frequently, not invariably. DAD is neither necessary nor sufficient for the clinical syndrome, and must not be curated as a synonym for ARDS. This clinical-pathological discordance is a legitimate KNOWLEDGE_GAP discussion.

Genetic testing

Not indicated. There is no clinical genetic test for ARDS; no gene panel, no single-gene test, no WES/WGS indication, no CMA, no karyotype, no FISH, no mtDNA testing, no repeat-expansion testing. Genetic work is research-only. Say so explicitly in the entry rather than leaving the section blank — the absence is informative.

Omics-based diagnostics

Research-stage only. Whole-blood transcriptomic classifiers for subphenotype assignment and plasma proteomic panels are the most developed; none is in clinical use. No liquid-biopsy or epigenomic diagnostic exists.

Differential diagnosis

Condition	Distinguishing features
Cardiogenic pulmonary oedema	Elevated BNP, LV dysfunction on echo, cardiomegaly, rapid response to diuresis, oedema/plasma protein ratio <0.65
Volume overload / fluid resuscitation-related oedema	Positive fluid balance, resolves with diuresis
Diffuse alveolar haemorrhage	Serial bloodier BAL aliquots, haemosiderin-laden macrophages, falling haemoglobin, vasculitis serology
Acute eosinophilic pneumonia	BAL eosinophilia >25%, dramatic steroid response
Acute interstitial pneumonia (Hamman-Rich)	Idiopathic — no identifiable insult; histologically DAD. `MONDO:0019203` ✅ in cache, and the repo has related interstitial-pneumonia MONDO terms cached
Acute exacerbation of idiopathic pulmonary fibrosis	Pre-existing fibrosis, honeycombing on prior imaging
Hypersensitivity pneumonitis (acute)	Exposure history; repo entry `Hypersensitivity_Pneumonitis.yaml` exists
Cryptogenic organising pneumonia	`MONDO:0015264` ✅; subacute course, migratory opacities
Drug-induced pneumonitis	Temporal drug relationship (amiodarone, bleomycin, checkpoint inhibitors)
Disseminated malignancy / lymphangitic carcinomatosis	Imaging pattern, history
Neurogenic pulmonary oedema	Preceding catastrophic CNS event
High-altitude pulmonary oedema	Exposure history
EVALI	Vaping history; repo entry exists

These make good differentials: entries — look up each MONDO ID from the sibling KB entry rather than guessing it.

Screening

No population screening exists or would be sensible (ARDS is an acute complication, not a latent disease). The functional analogue is risk stratification of at-risk hospitalised patients using the Lung Injury Prediction Score (PMID:20802164):

"LIPS discriminated patients who developed ALI from those who did not with an AUC of 0.80 (95% confidence interval, 0.78-0.82)."

"When adjusted for severity of illness and predisposing conditions, development of ALI increased the risk of in-hospital death (odds ratio, 4.1; 95% confidence interval, 2.9-5.7)."

LIPS is a good candidate for a definitions: entry with definition_type: PHENOTYPE_ALGORITHM and derivation_basis: ESTABLISHED_CRITERIA, validation_status.status: VALIDATED_AGAINST_GOLD_STANDARD (validated prospectively in the 5,584-patient multicentre cohort above).

11. Outcome / Prognosis

Mortality

Berlin-stratified hospital mortality (PMID:26903337, LUNG SAFE):

"Hospital mortality was 34.9% (95% CI, 31.4%-38.5%) for those with mild, 40.3% (95% CI, 37.4%-43.3%) for those with moderate, and 46.1% (95% CI, 41.9%-50.4%) for those with severe ARDS."

Berlin derivation-cohort mortality (PMID:22797452): 27% / 32% / 45% for mild / moderate / severe.

Overall trajectory (PMID:30872586): "Despite some improvements, mortality remains high at 30-40% in most studies."

Subphenotype-stratified (PMID:30078618, HARP-2): 28-day mortality 39% (hyperinflammatory) vs 17% (hypoinflammatory) — a larger spread than the Berlin severity strata produce, which is the argument that biology beats physiology as a prognostic axis.

Population-level burden (PMID:16236739): 190,600 US cases/year, 74,500 deaths, 3.6 million hospital days (AECC-era ALI).

Cause of death: predominantly multiple organ failure and the underlying precipitant; refractory hypoxaemia accounts for a minority (roughly 10-20%) of deaths. [unquoted] This is mechanistically important — it explains why oxygenation-improving therapies (inhaled NO, prone positioning in mild disease, ECMO) improve gas exchange without necessarily improving survival.

Life expectancy after survival

ARDS survivors carry elevated mortality for at least 1-5 years beyond discharge relative to matched controls, driven by comorbidity and functional decline rather than lung disease. [unquoted]

Morbidity, disability, and quality of life

The Herridge 5-year cohort (PMID:21470008) is the anchor — see §3 for verbatim quotes. Key points: 6-minute walk distance 76% of predicted at 5 years; SF-36 Physical Component Score 41 vs an age/sex-matched norm of 50; pulmonary function normal to near-normal; "a constellation of other physical and psychological problems developed or persisted in patients and family caregivers for up to 5 years"; "Patients with more coexisting illnesses incurred greater 5-year costs."

Common sequelae: ICU-acquired weakness, exercise limitation, cognitive impairment (executive function, memory), depression, anxiety, PTSD, chronic pain, joint contracture, tracheostomy-related complications, and caregiver burden. Instruments: SF-36, EQ-5D, 6MWT, HADS, IES-R, MoCA.

Complications

Ventilator-associated pneumonia, barotrauma/pneumothorax (quantified in PMID:28973363: 3.2% vs 1.2% requiring drainage), acute kidney injury, delirium, venous thromboembolism, GI bleeding, catheter-related bloodstream infection, ICU-acquired weakness, right heart failure, and — for ECMO patients — bleeding and thrombocytopenia (PMID:29791822: "more bleeding events leading to transfusion in the ECMO group than in the control group (in 46% vs. 28% of patients...) as well as more cases of severe thrombocytopenia (in 27% vs. 16%...)").

Recovery potential

Good pulmonary recovery is the norm in survivors; good functional recovery is not. Younger patients recover faster but, per PMID:21470008, "neither group returned to normal predicted levels of physical function at 5 years."

Prognostic factors

Clinical: age, severity stratum (P/F), non-pulmonary organ failures, shock, immunosuppression, chronic liver disease, APACHE/SOFA.
Physiologic: driving pressure (ΔP), dead-space fraction (V_D/V_T), respiratory-system compliance, ventilatory ratio, oxygenation index. Driving pressure is the ventilation variable most consistently associated with survival.
Aetiologic: trauma-associated ARDS has the lowest mortality; sepsis-associated the highest.
Biological: subphenotype assignment (above); individual markers Ang-2, IL-8, sRAGE, sTNFR-1, PAI-1, protein C.
Radiographic: extent of consolidation, fibroproliferative change on CT.

12. Treatment

The organising fact: no pharmacotherapy has an established mortality benefit in unselected ARDS. From PMID:30872586: "Treatment focuses on lung-protective ventilation; no specific pharmacotherapies have been identified." Every proven intervention is a way of supporting the patient while causing less additional injury. That is the shape of the treatment section, and it should be curated honestly — the negative trials carry as much information as the positive ones.

Interventions with proven mortality benefit

1. Low tidal volume ("lung-protective") ventilation — the foundational intervention (PMID:10793162, ARDS Network ARMA trial, N Engl J Med 2000;342:1301-8):

"The trial was stopped after the enrollment of 861 patients because mortality was lower in the group treated with lower tidal volumes than in the group treated with traditional tidal volumes (31.0 percent vs. 39.8 percent, P=0.007), and the number of days without ventilator use during the first 28 days after randomization was greater in this group (mean [+/-SD], 12+/-11 vs. 10+/-11; P=0.007)."

"In patients with acute lung injury and the acute respiratory distress syndrome, mechanical ventilation with a lower tidal volume than is traditionally used results in decreased mortality and increases the number of days without ventilator use."

Target: 6 mL/kg predicted body weight, plateau pressure ≤30 cmH₂O. treatment_term: NCIT:C70909 Mechanical Ventilation ✅ · therapeutic_modality: DEVICE (or OTHER) · targets the Ventilator-Induced Lung Injury node.

2. Prone positioning in severe ARDS (PMID:23688302, PROSEVA, N Engl J Med 2013;368:2159-68):

"The 28-day mortality was 16.0% in the prone group and 32.8% in the supine group (P<0.001). The hazard ratio for death with prone positioning was 0.39 (95% confidence interval [CI], 0.25 to 0.63). Unadjusted 90-day mortality was 23.6% in the prone group versus 41.0% in the supine group (P<0.001)"

"In patients with severe ARDS, early application of prolonged prone-positioning sessions significantly decreased 28-day and 90-day mortality."

Sessions of ≥16 h, in P/F <150 with FiO₂ ≥0.6 and PEEP ≥5. Severely underused — from LUNG SAFE: "Prone positioning was used in 16.3% (95% CI, 13.7%-19.2%) of patients with severe ARDS." treatment_term: ⚠️ search NCIT for a prone-positioning/patient-positioning procedure term; if none is reachable from NCIT:C25218, bind NCIT:C49236 Therapeutic Procedure ⚠️ and carry the specificity in preferred_term.

3. Dexamethasone in established moderate-severe ARDS (PMID:32043986, DEXA-ARDS, Lancet Respir Med 2020;8:267-276):

"The mean number of ventilator-free days was higher in the dexamethasone group than in the control group (between-group difference 4·8 days [95% CI 2·57 to 7·03]; p<0·0001). At 60 days, 29 (21%) patients in the dexamethasone group and 50 (36%) patients in the control group had died (between-group difference -15·3% [-25·9 to -4·9]; p=0·0047)."

"Early administration of dexamethasone could reduce duration of mechanical ventilation and overall mortality in patients with established moderate-to-severe ARDS."

Dose: 20 mg IV daily days 1-5, then 10 mg daily days 6-10. Note the trial stopped early for slow enrolment (277 of a planned 314), which tempers the estimate — worth a notes: line. treatment_term: NCIT:C15986 Pharmacotherapy ✅ · therapeutic_agent: CHEBI:41879 dexamethasone ✅ · therapeutic_modality: SMALL_MOLECULE.

4. Dexamethasone in COVID-19 respiratory failure (PMID:32678530, RECOVERY, N Engl J Med 2021;384:693-704):

"In the dexamethasone group, the incidence of death was lower than that in the usual care group among patients receiving invasive mechanical ventilation (29.3% vs. 41.4%; rate ratio, 0.64; 95% CI, 0.51 to 0.81) and among those receiving oxygen without invasive mechanical ventilation (23.3% vs. 26.2%; rate ratio, 0.82; 95% CI, 0.72 to 0.94) but not among those who were receiving no respiratory support at randomization (17.8% vs. 14.0%; rate ratio, 1.19; 95% CI, 0.92 to 1.55)."

The severity-dependent effect direction is the notable part — steroids help when lung injury is established and appear unhelpful (possibly harmful) before it is.

Interventions with benefit on secondary outcomes but not mortality

5. Conservative fluid management (PMID:16714767, FACTT, N Engl J Med 2006;354:2564-75):

"The rate of death at 60 days was 25.5 percent in the conservative-strategy group and 28.4 percent in the liberal-strategy group (P=0.30...)"

"the conservative strategy of fluid management improved lung function and shortened the duration of mechanical ventilation and intensive care without increasing nonpulmonary-organ failures."

treatment_term: NCIT:C116537 Fluid Therapy ✅.

6. High-flow nasal oxygen in acute hypoxaemic respiratory failure (PMID:25981908, FLORALI, N Engl J Med 2015;372:2185-96):

"The intubation rate (primary outcome) was 38% (40 of 106 patients) in the high-flow-oxygen group, 47% (44 of 94) in the standard group, and 50% (55 of 110) in the noninvasive-ventilation group (P=0.18 for all comparisons)."

"The hazard ratio for death at 90 days was 2.01 (95% confidence interval [CI], 1.01 to 3.99) with standard oxygen versus high-flow oxygen (P=0.046) and 2.50 (95% CI, 1.31 to 4.78) with noninvasive ventilation versus high-flow oxygen (P=0.006)."

treatment_term: NCIT:C94624 Oxygen Therapy ✅.

7. Awake prone positioning in COVID-19 hypoxaemic failure (PMID:34425070, Lancet Respir Med 2021;9:1387-1395):

"Treatment failure occurred in 223 (40%) of 564 patients assigned to awake prone positioning and in 257 (46%) of 557 patients assigned to standard care (relative risk 0·86 [95% CI 0·75-0·98]). The hazard ratio (HR) for intubation was 0·75 (0·62-0·91), and the HR for mortality was 0·87 (0·68-1·11)"

8. Helmet NIV (PMID:27179847, JAMA 2016;315:2435-41) — single-centre, stopped early, so hypothesis-generating:

"The intubation rate was 61.5% (n = 24) for the face mask group and 18.2% (n = 8) for the helmet group (absolute difference, -43.3%; 95% CI, -62.4% to -24.3%; P < .001)."

"Multicenter studies are needed to replicate these findings."

Interventions with contested or neutral results

9. Neuromuscular blockade — a genuine contradiction in the literature, and worth curating as such.

ACURASYS was positive (PMID:20843245, N Engl J Med 2010;363:1107-16):

"The hazard ratio for death at 90 days in the cisatracurium group, as compared with the placebo group, was 0.68 (95% confidence interval [CI], 0.48 to 0.98; P=0.04), after adjustment for both the baseline PaO2:FIO2 and plateau pressure and the Simplified Acute Physiology II score."

ROSE was null (PMID:31112383, N Engl J Med 2019;380:1997-2008):

"At 90 days, 213 patients (42.5%) in the intervention group and 216 (42.8%) in the control group had died before hospital discharge (between-group difference, -0.3 percentage points; 95% confidence interval, -6.4 to 5.9; P = 0.93). While in the hospital, patients in the intervention group were less physically active and had more adverse cardiovascular events than patients in the control group."

Curate this as two evidence items on the same claim — one SUPPORT (ACURASYS), one REFUTE (ROSE) — rather than averaging them into a hedge. The differences (ROSE used higher PEEP and lighter sedation in controls) are the substance of the disagreement. therapeutic_agent: CHEBI:140621 cisatracurium ✅.

10. ECMO in very severe ARDS (PMID:29791822, EOLIA, N Engl J Med 2018;378:1965-1975):

"At 60 days, 44 of 124 patients (35%) in the ECMO group and 57 of 125 (46%) in the control group had died (relative risk, 0.76; 95% confidence interval [CI], 0.55 to 1.04; P=0.09)."

"Among patients with very severe ARDS, 60-day mortality was not significantly lower with ECMO than with a strategy of conventional mechanical ventilation that included ECMO as rescue therapy."

Note the 28% crossover from control to rescue ECMO, which makes this a trial of early vs rescue ECMO rather than ECMO vs no ECMO — a Bayesian reanalysis favoured ECMO. [unquoted] treatment_term: NCIT:C171507 Extracorporeal Membrane Oxygenation ✅ · therapeutic_modality: DEVICE.

11. Conservative oxygenation — harmful signal (PMID:32160661, LOCO₂, N Engl J Med 2020;382:999-1008):

"After the enrollment of 205 patients, the trial was prematurely stopped by the data and safety monitoring board because of safety concerns and a low likelihood of a significant difference between the two groups in the primary outcome."

"At day 90, 44.4% of the patients in the conservative-oxygen group and 30.4% of the patients in the liberal-oxygen group had died (difference, 14.0 percentage points; 95% CI, 0.7 to 27.2). Five mesenteric ischemic events occurred in the conservative-oxygen group."

Interventions shown to be harmful

12. Aggressive recruitment manoeuvres with PEEP titration (PMID:28973363, ART trial, JAMA 2017;318:1335-1345):

"At 28 days, 277 of 501 patients (55.3%) in the experimental group and 251 of 509 patients (49.3%) in the control group had died (hazard ratio [HR], 1.20; 95% CI, 1.01 to 1.42; P = .041)."

"In patients with moderate to severe ARDS, a strategy with lung recruitment and titrated PEEP compared with low PEEP increased 28-day all-cause mortality. These findings do not support the routine use of lung recruitment maneuver and PEEP titration in these patients."

Failed pharmacotherapies (curate as REFUTE evidence — the negative record is the field's most consistent finding)

β₂-agonists (salbutamol/albuterol — CHEBI:2549 ✅ — BALTI-2 and ALTA, both harmful or futile), exogenous surfactant, inhaled nitric oxide (CHEBI:16480 ✅ — improves oxygenation, no mortality benefit, AKI signal), ketoconazole, lisofylline, N-acetylcysteine, activated protein C, statins in unselected patients (HARP-2, SAILS — see the subphenotype caveat below), omega-3/antioxidant enteral formulas (OMEGA — harmful), GM-CSF, keratinocyte growth factor (KGF — harmful), aspirin for prevention (LIPS-A, PMID:27179988), early high-dose methylprednisolone in late ARDS (harmful after day 14).

Precision-medicine / predictive enrichment

The one durable positive signal from a "failed" drug — simvastatin (CHEBI:9150 ✅) in the hyperinflammatory subphenotype (PMID:30078618, quoted in §6): "within the hyperinflammatory subphenotype, patients treated with simvastatin had significantly higher 28-day survival than did those given placebo (p=0·008)." Interpretation from the same abstract: "These findings support further pursuit of predictive enrichment strategies in critical care clinical trials."

Cell and advanced therapies

Mesenchymal stromal cells — extensively tested, consistently safe, not yet efficacious. A 2024 double-blind RCT of BM-MSCs in COVID-19 ARDS missed its primary endpoint (change in P/F at day 7) but showed shorter time to oxygen discontinuation (14 vs 23 days) and shorter hospital stay (17.5 vs 28 days); PMID:38409332, Bone Marrow Transplant 2024. The STAT phase 2b trial randomised 120 ventilated ARDS patients (101 COVID, 19 classical) to a single IV MSC dose vs placebo. [both unquoted — retrieve abstracts before creating evidence items] Safety across trials is good up to 10×10⁶ cells/kg. therapeutic_modality: CELL_THERAPY.

Gene therapy, gene editing, ASOs, siRNA, mRNA therapy: none in clinical development for ARDS. aso_details is not applicable.

Immunomodulators: anti-IL-6 (tocilizumab) and JAK inhibition (baricitinib) have proven benefit in COVID-19 specifically — e.g. PMID:33306283, ACTT-2: "Patients receiving high-flow oxygen or noninvasive ventilation at enrollment had a time to recovery of 10 days with combination treatment and 18 days with control (rate ratio for recovery, 1.51; 95% CI, 1.10 to 2.08)." Curate these under COVID-19, cross-referenced from ARDS, not as general ARDS therapy.

Experimental pipeline (2024-2026)

Treat all of the following as low-confidence, non-peer-reviewed corporate disclosures until a published trial report exists — do not create evidence items from press releases. Reported agents include paridiprubart (anti-TLR4 monoclonal antibody; a phase 3 readout was announced in 2025-2026), vilobelimab (anti-C5a), STSA-1002 (C5a inhibitor), GEn-1124 (MAPK14 inhibitor), ALT-100 (anti-eNAMPT), recombinant human plasma gelsolin (rhu-pGSN, FDA Fast Track June 2025), and AV-001 (Tie2 agonist, FDA Fast Track May 2024). More than 50 companies are reported to have ARDS programmes. [all unquoted — search-summary sourced] The mechanistic targets are informative even where efficacy is unproven: TLR4 (chain step 2), complement C5a (step 3-4), Tie2/Ang-2 (step 5), gelsolin (actin scavenging after cell necrosis).

A host-directed-therapy platform trial with placebo, vilobelimab (Cohort A), and paridiprubart (Cohort B) arms is running. [unquoted — locate the NCT identifier before curating a clinical_trials: entry]

Supportive and rehabilitative care

Sedation minimisation and daily awakening trials, early mobilisation, VTE and stress-ulcer prophylaxis, nutrition, tracheostomy for prolonged ventilation, delirium prevention, and structured post-ICU follow-up/rehabilitation. NCIT:C15747 Supportive Care ✅; NCIT:C15302 Physical Therapy ⚠️ and NCIT:C15315 Rehabilitation ⚠️ for the recovery phase.

Treatment algorithm

The ESICM 2023 guideline is the authoritative synthesis (PMID:37326646, Intensive Care Med 2023;49:727-759):

"The CPG addressed 21 questions and formulates 21 recommendations on the following domains: (1) definition; (2) phenotyping, and respiratory support strategies including (3) high-flow nasal cannula oxygen (HFNO); (4) non-invasive ventilation (NIV); (5) tidal volume setting; (6) positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM); (7) prone positioning; (8) neuromuscular blockade, and (9) extracorporeal life support (ECLS)."

"The scope of this CPG is limited to adult patients and to non-pharmacological respiratory support strategies across different aspects of acute respiratory distress syndrome (ARDS), including ARDS due to coronavirus disease 2019 (COVID-19)."

And the 2024 BMJ state-of-the-art review (PMID:39467606, BMJ 2024;387:e076612):

"Key highlights include a recommended new global definition of ARDS and updated guidelines for managing ARDS on a backbone of established interventions such as low tidal volume ventilation, prone positioning, and a conservative fluid strategy."

Practical escalation ladder: treat the precipitant → lung-protective ventilation (6 mL/kg PBW, Pplat ≤30, ΔP ≤15) → moderate PEEP → conservative fluids → if P/F <150: prone positioning ± neuromuscular blockade → consider dexamethasone → if refractory: inhaled pulmonary vasodilator as a bridge, then VV-ECMO at a specialist centre.

13. Prevention

Primary prevention

Prevent the precipitating insults: pneumococcal and influenza vaccination (NCIT:C15346 Vaccination ⚠️), COVID-19 vaccination, sepsis bundles with early antibiotics and source control, trauma prevention, aspiration precautions (head-of-bed elevation, careful sedation, swallow assessment), restrictive transfusion policies and male-predominant plasma donor selection (which substantially reduced TRALI incidence — a genuine public-health success), and alcohol- and tobacco-cessation programmes.

Secondary prevention (the active research frontier)

Lung-protective ventilation in patients without ARDS — intraoperatively and in the ICU — reduces subsequent ARDS incidence. [unquoted]
Restrictive fluid resuscitation in sepsis and trauma.
Risk stratification with LIPS (PMID:20802164, AUC 0.80) to enrich prevention trials.
Checklist-based prevention bundles (e.g. "Checklist for Lung Injury Prevention", CLIP) — modest observational benefit. [unquoted]
Pharmacological prevention: tested and negative. Aspirin (LIPS-A, PMID:27179988), inhaled budesonide/formoterol, and statins have all failed to prevent ARDS in at-risk patients. Curate these as REFUTE.

Tertiary prevention

Preventing complications in established ARDS: VAP prevention bundles, VTE prophylaxis, sedation minimisation and delirium prevention, early mobilisation to limit ICU-acquired weakness, pressure-injury prevention (especially in proned patients — facial and chest pressure injuries are the main prone-position harm), and avoiding the interventions shown to be harmful (aggressive recruitment, conservative oxygenation targets, late high-dose steroids).

Screening, genetic screening, and counselling

Not applicable. There is no ARDS screening programme, no carrier screening, no prenatal or preimplantation testing, and no role for genetic counselling. State this explicitly.

Public health and environmental interventions

Air-quality regulation (PM₂.₅, ozone), occupational exposure limits for respiratory irritants, industrial chemical-release preparedness, tobacco control, alcohol policy, pandemic preparedness and ICU surge capacity, and — following the Global Definition's resource-limited category — expansion of pulse oximetry and lung ultrasound in low-resource settings, which is a diagnostic-equity intervention with direct prevention implications.

14. Other Species / Natural Disease

ARDS is not a Mendelian animal disease and has no OMIA entry. It occurs naturally in animals as an acquired critical-illness syndrome, and the veterinary literature explicitly borrows the human framework.

Species with recognised naturally occurring ALI/ARDS

Species	NCBITaxon (⚠️ verify)	Context
Dog (Canis lupus familiaris)	9615	Veterinary ALI/ARDS consensus criteria exist (Dorothy Russell Havemeyer working group, 2007); causes include sepsis, pancreatitis, aspiration, smoke inhalation, babesiosis
Cat (Felis catus)	9685	Less commonly recognised; sepsis, trauma
Horse (Equus caballus)	9796	Foal ARDS/acute interstitial pneumonia; equine multinodular pulmonary fibrosis as a related fibrotic outcome
Cattle (Bos taurus)	9913	Acute bovine pulmonary emphysema and oedema ("fog fever", 3-methylindole from tryptophan fermentation) — a naturally occurring toxic ALI with real mechanistic interest
Pig (Sus scrofa)	9823	Both natural (PRRSV, Actinobacillus) and the dominant large-animal experimental model
Sheep (Ovis aries)	9940	Chronically instrumented smoke-inhalation/sepsis model; the classic lung-lymph preparation

[all veterinary claims unquoted — retrieve the Havemeyer veterinary ALI/ARDS consensus and any OMIA/VetCompass records before creating evidence items]

Orthologous genes

Not meaningful for a syndrome with no causal gene. The relevant orthologies are of the mechanism: mouse Tlr4/human TLR4, mouse Nlrp3/human NLRP3, mouse Scnn1a/human SCNN1A, mouse Sftpc/human SFTPC. Alliance of Genome Resources and HomoloGene are the resources.

Comparative pathology

Diffuse alveolar damage with hyaline membranes is recognisable across mammals, but there are consequential species differences that limit translation: - Neutrophil biology: mouse neutrophils lack defensins and have far lower MPO content than human neutrophils; mouse blood is lymphocyte-predominant, human neutrophil-predominant. - Endotoxin sensitivity: mice tolerate LPS doses that would be uniformly lethal in humans, by orders of magnitude. - Collateral ventilation and lobar anatomy differ (pigs and cattle have essentially no collateral ventilation; dogs have extensive collateral channels), which changes atelectasis and recruitment behaviour. - Pulmonary intravascular macrophages are present in ruminants, pigs, cats and horses but essentially absent in humans, mice and dogs — a major difference in how the lung handles circulating particulates and endotoxin. - Mice do not spontaneously develop hyaline membranes.

Zoonotic potential and cross-species susceptibility

ARDS itself is not transmissible; its precipitants frequently are. Zoonotic and cross-species agents that cause ARDS in humans: SARS-CoV-2, SARS-CoV, MERS-CoV (camel reservoir; the repo has a MERS entry), avian influenza H5N1/H7N9, hantavirus (HPS — hantavirus pulmonary syndrome, a distinct entity with a capillary-leak mechanism that overlaps ARDS), Coxiella burnetii, Francisella tularensis, Bacillus anthracis, leptospirosis (Weil's disease with pulmonary haemorrhage), and plague pneumonia.

15. Model Organisms

The essential framework document is the ATS workshop report (PMID:35103557, Am J Respir Cell Mol Biol 2022;66:e1-e14). It should be cited on every ARDS animal model entry:

"We propose that ALI presents as a 'multidimensional entity' characterized by four 'domains' that reflect the key pathophysiologic features and underlying biology of human acute respiratory distress syndrome. These domains are 1) histological evidence of tissue injury, 2) alteration of the alveolar-capillary barrier, 3) presence of an inflammatory response, and 4) physiologic dysfunction."

"We suggest that mechanistic studies may justifiably focus on a single domain of lung injury, but models must document alterations of at least three of the four domains to qualify as 'experimental ALI.'"

"The continuum concept of ALI increases the flexibility and applicability of the definition to multiple models while increasing the likelihood of translating preclinical findings to critically ill patients."

This maps directly onto dismech's ModelMechanismLink structure: the four domains are natural readouts, and the "at least three of four" rule is a defensible basis for assigning fidelity: HIGH vs MODERATE.

Induced models (there are no spontaneous genetic ARDS models)

Model	Species	Mimics	`fidelity` guidance	Key limitation
Intratracheal / intranasal LPS	Mouse (10090), rat (10116)	Direct insult, TLR4 → NF-κB (chain steps 1-3)	MODERATE	No pathogen replication; mice ~1000× less LPS-sensitive than humans; self-limited, rarely lethal
Intratracheal HCl (acid aspiration)	Mouse, rat, rabbit	Aspiration pneumonitis; epithelial necrosis	MODERATE	Uniform, synchronous injury unlike clinical aspiration
Cecal ligation and puncture (CLP)	Mouse, rat	Indirect/septic ARDS (steps 1, 13)	MODERATE	Lung injury is often mild; highly variable by puncture size/needle gauge
Live bacterial pneumonia (P. aeruginosa, S. pneumoniae, K. pneumoniae)	Mouse, rat, pig	Direct infectious ARDS	MODERATE-HIGH	Strain- and dose-sensitive
Influenza A / SARS-CoV-2 infection	Mouse (adapted strains or K18-hACE2 transgenic), hamster (10036), ferret (9669), NHP (9544/9541)	Viral ARDS	MODERATE-HIGH	Wild-type mice are not susceptible to SARS-CoV-2 without hACE2; K18-hACE2 mice die of encephalitis, not pneumonia — a well-documented `FAILS_TO_RECAPITULATE` case
High-tidal-volume ventilation (VILI)	Mouse, rat, pig (9823), sheep (9940)	Ventilator-induced injury (step 12)	HIGH for the mechanical domain	Requires healthy lungs unless combined ("two-hit"); Vt used (20-40 mL/kg) far exceeds anything clinical
Two-hit (LPS + VILI, acid + VILI)	Mouse, rat, pig	Clinical reality of injured lung + ventilator	HIGH	Complex, low throughput
Oleic acid infusion	Dog (9615), pig, sheep	Endothelial injury, fat embolism	MODERATE	Chemically non-physiological; minimal inflammatory component (fails the inflammation domain)
Hyperoxia (>95% O₂)	Mouse, rat	Oxygen toxicity, oxidative injury	LOW-MODERATE	Slow (days); mechanism is oxidant-dominant only
Bleomycin	Mouse, rat	Fibroproliferative phase only (step 14b)	MODERATE for fibrosis	Not an ARDS model — models fibrosis; self-resolving in mice, unlike human IPF
Smoke inhalation ± burn	Sheep, pig	Inhalation injury	HIGH	Requires large-animal facilities
Ischaemia-reperfusion / transplant	Rat, pig	Primary graft dysfunction	MODERATE	Narrow clinical analogue

Genetic models

Not disease models but mechanism dissection tools: Tlr4⁻/⁻, Nlrp3⁻/⁻, Casp1⁻/⁻, Il6⁻/⁻, Cxcr2⁻/⁻, Ager (RAGE)⁻/⁻, Nfe2l2 (Nrf2)⁻/⁻, Angpt2 conditional, Sftpc-CreER lineage-tracing for AT2→AT1 transdifferentiation, Scgb1a1-CreER, and neutrophil- or macrophage-specific conditional deletions (LysM-Cre, Mrp8-Cre). Resources: MGI, IMPC, KOMP, IMSR, MMRRC, EMMA. Because ARDS has no causal gene, no knockout "models ARDS" — each models a step in the chain, and modeled_mechanisms should point at that specific node with an honest relationship (usually PERTURBS, not RECAPITULATES).

Non-animal / NAM systems (these belong in `experimental_models:`, not `animal_models:`)

Human alveolar epithelial cell lines: A549 (Cellosaurus CVCL_0023 ⚠️ — a lung adenocarcinoma line, an imperfect AT2 surrogate), NCI-H441, primary human alveolar type II cells.
Human pulmonary microvascular endothelial cells (HPMEC/HMVEC-L) with trans-endothelial electrical resistance (TEER) and dextran-flux permeability readouts — directly measures chain step 5.
Air-liquid interface (ALI) cultures of primary human airway/alveolar epithelium.
iPSC-derived AT2 organoids / alveolospheres — currently the best system for step 7 (fluid clearance) and step 14a (AT2→AT1 repair).
Lung-on-a-chip — the Ingber alveolus-chip reproduces cyclic mechanical strain plus a vascular compartment, uniquely capturing volutrauma (step 12) in a human-cell system.
Ex vivo lung perfusion (EVLP) of rejected human donor lungs — the highest-fidelity human system available: measures alveolar fluid clearance directly in intact human tissue, and is where much of the MSC and β-agonist mechanistic work was done.
Precision-cut lung slices (PCLS) from human tissue.

The existing KB entry already has an experimental_models: block; adding an animal_models: block with modeled_mechanisms links (targeting the bare node names listed in §6) would be the single highest-value structural addition.

Research applications and limitations

Animal models have been reliable for testing ventilation strategies (VILI biology translated well — low tidal volume worked in animals and in humans) and unreliable for testing pharmacotherapy (dozens of agents that rescued LPS-treated mice have failed in humans). The honest framing for a HUMAN_MODEL_MISMATCH discussion: the models reproduce the injury but not the patient — no comorbidity, no age, no prior antibiotics, no concurrent organ failure, no 12-hour delay before treatment starts, and a genetically uniform host. The ATS report's "continuum" and "three of four domains" framework is the field's own attempt to fix the reporting side of this problem.

Curation Recommendations for the dismech Entry

Highest-value additions to kb/disorders/Acute_Respiratory_Distress_Syndrome.yaml, roughly in order:

prevalence: — two structured records (LUNG SAFE period prevalence; Rubenfeld annual incidence), each with measure_type and a notes: line recording the definitional era. Verbatim snippets are available above for both.
environmental: — 8-10 exposures with influences_mechanisms links (bare-name targets). Run just environmental-term-audit first for ECTO reuse candidates. Remember the top-level evidence: gate.
animal_models: — LPS, acid aspiration, CLP, VILI, two-hit, with modeled_mechanisms links and PMID:35103557 as the framework citation.
genetic: — susceptibility-typed entries only (FLT1, BORCS5/DUSP16, ACE), with inheritance: bound to HP:0010982 and a notes: line stating there is no causal gene.
clinical_trials: — the landmark set (NCT00527813 PROSEVA, NCT01731795 DEXA-ARDS, NCT00299650 ACURASYS, NCT02509078 ROSE, NCT01470703 EOLIA, NCT01374022 ART, NCT02713451 LOCO₂, NCT00281268 FACTT, NCT02010073 LUNG SAFE), all with phase: and status: as enum values (PHASE_III, COMPLETED — not "Phase III"/"Completed").
datasets: — currently empty; just discover-datasets then manual relevance triage, screening hard against neonatal RDS.
definitions: — the Global Definition, Berlin Definition, PALICC-2, and LIPS as a PHENOTYPE_ALGORITHM with derivation_basis: ESTABLISHED_CRITERIA.
New mechanistic_hypotheses group for the hyperinflammatory/hypoinflammatory axis, with downstream[].hypothesis_groups opting the relevant edges in.
Two new pathophysiology nodes: impaired alveolar fluid clearance (ENaC/Na⁺-K⁺-ATPase failure) and systemic cytokine spillover → MODS.
discussions: with kind: HUMAN_MODEL_MISMATCH for the animal-model translation failure, and kind: KNOWLEDGE_GAP for the DAD/clinical-syndrome discordance and the unexplained diabetes-protective effect.

Before any PR: just validate, just count-verified-snippets, just validate-terms, then the batched just validate-disorders. Every quoted snippet above that is not flagged [unquoted] was retrieved verbatim in this session and should survive the reference validator, but fetch each PMID's cache with just fetch-reference and re-check — whitespace normalisation and folded-scalar hyphenation are the usual failure modes, and square brackets inside snippets pass locally while failing CI.

Sources

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	46
Resolved	46
Unresolved (possible confabulation)	0
Unverifiable	0
Quoted claims checked	1
Quoted claims found in source	1
Quoted claims not found in source	0
References weighed for topical relevance	46
On topic	40
Off topic	0

All extracted references resolved successfully.

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Subtypes

Mechanistic Hypotheses

Discussions and Knowledge Gaps

Pathophysiology

Histopathology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Environmental Factors

Biochemical Markers

Diagnosis

Progression

Prevalence

Related Datasets

Clinical Trials

Experimental Models

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References & Deep Research

References

Deep Research

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of Acute Respiratory Distress Syndrome. Core disease mechanisms, molecular an...

Relevant Papers

[1] Lung regeneration: diverse cell types and the therapeutic potential

[2] Acute respiratory distress syndrome (ARDS): from mechanistic insights to therapeutic strategies

[3] A practical approach to adult acute respiratory distress syndrome

[4] Genetic and Multi‐Omics Insights Into Monocyte Pantothenate‐Mediated Protection in Acute Respiratory Distress Syndrome

[5] Obesity promotes ARDS by modulating ceramide transfer protein-ceramide pathway and exacerbating oxidative stress/apoptosis in alveolar macrophages

[6] Evolution of multiple omics approaches to define pathophysiology of pediatric acute respiratory distress syndrome

[7] Classic Signaling Pathways in Alveolar Injury and Repair Involved in Sepsis-Induced ALI/ARDS: New Research Progress and Prospect

[8] Acute Respiratory Failure: Pathophysiological Basis From A Multidisciplinary Clinical Approach

[9] Messenger RNA sequencing reveals similar mechanisms between neonatal and acute respiratory distress syndrome

[10] NR4A1 Promotes LPS-Induced Acute Lung Injury through Inhibition of Opa1-Mediated Mitochondrial Fusion and Activation of PGAM5-Related Necroptosis

[11] Candidate genes and pathogenesis investigation for sepsis-related acute respiratory distress syndrome based on gene expression profile

[12] A comprehensive systematic review of the phenotypes and their role in improving medications and clinical results in the acute respiratory distress syndrome: exploring the potential of personalized therapy

[13] Single-cell analysis reveals dysregulated inflammatory response in peripheral blood immunity in patients with acute respiratory distress syndrome

[14] Advancement in Precision Medicine and Recommendation System for Clinical Trials Using Deep Learning Methods

[15] Longitudinal multi-omic signatures of ARDS and sepsis inflammatory phenotypes identify key pathways associated with mortality

[16] Development and functional significance of the pulmonary surfactant system

[17] Values of integration between lipidomics and clinical phenomes in patients with acute lung infection, pulmonary embolism, or acute exacerbation of chronic pulmonary diseases: a preliminary study

[18] Enhanced mortality prediction in pneumonia-associated acute respiratory distress syndrome: a model integrating lymphocyte subsets with clinical parameters in non-immunosuppressed adults

[19] [Genetic predisposition and Pediatric Acute Respiratory Distress Syndrome: New tools for genetic study].

[20] Comorbidity Networks in Cardiovascular Diseases

Notes

Acute Respiratory Distress Syndrome (ARDS) — Disease Characteristics Research Report

1. Disease Information

Overview

Definitional history

Identifiers

Synonyms and alternative names

Data provenance character

2. Etiology

Disease causal factors

Genetic risk factors

Environmental / acquired risk factors

Protective factors

Gene-environment interactions

3. Phenotypes

Core respiratory phenotypes

Systemic / extrapulmonary phenotypes

Laboratory abnormalities (LOINC-codable)

Long-term / survivorship phenotypes

4. Genetic / Molecular Information

5. Environmental Information

Lifestyle factors

Infectious agents

6. Mechanism / Pathophysiology

The ordered causal chain

Mapping to the existing KB nodes

Molecular pathways (GO / KEGG / Reactome)

Cellular processes and cell types

Protein dysfunction, metabolic changes, biochemical abnormalities

Immune system involvement

Tissue damage mechanisms

Subphenotypes: the dominant modern framework

Molecular profiling

7. Anatomical Structures Affected

Organ level

Non-animal / NAM systems (these belong in `experimental_models:`, not `animal_models:`)