ARDS is a life-threatening form of noncardiogenic pulmonary edema characterized by the acute onset of hypoxemic respiratory failure with bilateral pulmonary infiltrates, not fully explained by cardiac failure or fluid overload. [1-2] It accounts for ~10% of ICU admissions and ~24% of mechanically ventilated patients, with in-hospital mortality ranging from 27% (mild) to 45% (severe). [2-3]
1. History
- Onset timing: Symptoms develop within 7 days of a known clinical insult or new/worsening respiratory symptoms [1][4]
- Key HPI questions: Preceding infection (pneumonia, URI), recent surgery, trauma, aspiration event, pancreatitis, transfusions, drug overdose, inhalation exposure, vaping/e-cigarette use [1]
- Symptom characterization: Rapidly progressive dyspnea, tachypnea, cyanosis refractory to supplemental oxygen, inability to lie flat [3][5]
- Progression: Typically evolves over hours to days; an indolent onset (>7 days) should prompt consideration of ARDS mimics [6]
- Important negatives: Absence of orthopnea, paroxysmal nocturnal dyspnea, peripheral edema, or prior CHF exacerbations helps distinguish from cardiogenic pulmonary edema [3]
2. Alarm Features
- Refractory hypoxemia: SpO₂ <88% despite high-flow oxygen or escalating FiO₂ [7]
- PaO₂/FiO₂ ≤100 mm Hg (severe ARDS) — mortality ~45% [1][5]
- Driving pressure >14 cm H₂O — independently associated with increased mortality [8]
- Hemodynamic instability requiring vasopressors
- Multi-organ dysfunction (renal failure, hepatic dysfunction, coagulopathy)
- Rapid deterioration despite lung-protective ventilation — consider ECMO referral [9-10]
- Acute cor pulmonale from elevated pulmonary vascular resistance [11]
3. Medications
- Corticosteroids: Suggested for moderate-to-severe ARDS within 14 days of onset (dexamethasone 20 mg IV daily × 5 days, then 10 mg × 5 days is a commonly studied regimen); administration past 14 days may worsen outcomes [9-10]
- Neuromuscular blocking agents (NMBAs): Cisatracurium boluses suggested in early severe ARDS with refractory hypoxemia or ventilator dyssynchrony; intermittent boluses preferred over continuous infusion; limit to ≤48 hours [7][10][12]
- Inhaled pulmonary vasodilators: Inhaled nitric oxide or epoprostenol may transiently improve oxygenation but have no proven mortality benefit — use as rescue therapy [11]
- Medications to avoid: Excessive IV fluids (target net neutral-to-negative balance once off vasopressors) [1][9]
- DVT prophylaxis: Subcutaneous heparin or LMWH unless contraindicated [1]
- Stress ulcer prophylaxis: PPI or H2 blocker [1]
- Treat the underlying cause: Antibiotics for sepsis/pneumonia, source control for intra-abdominal pathology [1]
4. Diet
- Enteral nutrition is preferred and should be initiated early (within 24–48 hours of ICU admission) when hemodynamically stable
- Trophic/hypocaloric feeding may be used initially in the acute phase
- Immunonutrition (omega-3 fatty acids, antioxidants) has not shown consistent benefit in ARDS [13]
- Conservative fluid strategy is critical — aggressive diuresis to achieve net negative fluid balance once off vasopressors improves lung function and shortens ventilator days [1][14]
5. Review of Systems
- Pulmonary: Dyspnea, cough, sputum production, hemoptysis, pleuritic chest pain
- Infectious: Fever, chills, rigors, recent sick contacts, travel history
- GI: Nausea/vomiting (aspiration risk), abdominal pain (pancreatitis, intra-abdominal sepsis)
- Hematologic: Recent transfusions (transfusion-related acute lung injury)
- Neurologic: Altered mental status (hypoxia, septic encephalopathy)
- Musculoskeletal: Trauma history, burns
- Substance use: Alcohol, vaping/e-cigarette use, drug overdose [1]
6. Collateral History and Family History
- Collateral: Witnesses to aspiration events, timeline of symptom onset, medication/substance ingestion, recent procedures or transfusions
- Social context: Alcohol use disorder (independent risk factor for ARDS), smoking, occupational/environmental inhalation exposures [1][15]
- Family history: Genetic susceptibility is suggested but attributable risk of any single polymorphism is small; haptoglobin variant Hp-2 is associated with increased ARDS risk in sepsis [15]
7. Risk Factors
- Pneumonia (most common cause — bacterial and viral) [1][15]
- Non-pulmonary sepsis [1]
- Aspiration of gastric contents [1]
- Severe trauma (especially thoracic injuries, pulmonary contusion, traumatic brain injury) [16]
- Pancreatitis [1]
- Massive transfusion / transfusion-related acute lung injury [15]
- Drug overdose (salicylates, opioids) [1][17]
- Burns and inhalation injury [2]
- Drowning, smoke inhalation, EVALI [1]
- Modifiable risk factors: Alcohol use, cigarette smoking, ambient air pollution, excessive crystalloid resuscitation in trauma (OR 1.19 per additional liter in first 6 hours) [15-16]
8. Differential Diagnosis
- Cardiogenic pulmonary edema / decompensated CHF — most important to exclude; look for elevated BNP, S3 gallop, JVD, peripheral edema; echocardiography is key [2-3]
- Bilateral pneumonia without ARDS — may not meet oxygenation criteria
- Diffuse alveolar hemorrhage — hemoptysis, dropping hemoglobin, bloody BAL [1]
- Acute eosinophilic pneumonia — peripheral eosinophilia, BAL eosinophils >25% [1]
- Organizing pneumonia / drug-induced pneumonitis — subacute course, medication exposure [1]
- Hypersensitivity pneumonitis — exposure history, BAL lymphocytosis [1]
- Acute exacerbation of interstitial lung disease — known ILD, ground-glass + honeycombing on CT [1]
- Pulmonary vasculitis (e.g., GPA, anti-GBM) — systemic features, ANCA/anti-GBM antibodies [1]
- Pulmonary alveolar proteinosis — "crazy paving" on CT, milky BAL [1]
- Acute chest syndrome (sickle cell disease) [1]
9. Past Medical History
- Prior episodes of ARDS or ICU admissions
- Chronic lung disease (COPD, ILD) — may complicate ventilator management
- Heart failure — must be excluded or recognized as coexisting (up to one-third of ARDS patients) [6]
- Immunosuppression — broadens infectious differential (PJP, fungal, viral)
- Chronic liver disease, chronic kidney disease — affect fluid management and prognosis
- Recent surgeries (especially esophagectomy, cardiothoracic) [1]
- Sickle cell disease [1]
10. Physical Exam
- Vital signs: Tachypnea (often >30/min), tachycardia, hypoxemia (SpO₂ <90% on room air), hypotension if concurrent sepsis/shock
- Pulmonary: Bilateral crackles/rales, decreased breath sounds, increased work of breathing (accessory muscle use, nasal flaring, intercostal retractions)
- Cardiovascular: Assess for JVD, S3 gallop, peripheral edema (to differentiate from cardiogenic edema); RV heave if acute cor pulmonale
- Skin: Cyanosis, mottling (if shock), petechiae (fat embolism syndrome)
- Abdominal: Tenderness (pancreatitis, intra-abdominal sepsis as precipitant)
- Neurologic: Altered mental status from hypoxia or underlying sepsis
11. Lab Studies
- ABG: Essential — PaO₂/FiO₂ ratio defines severity (mild >200, moderate 100–200, severe ≤100) [1-2]
- SpO₂/FiO₂ ratio: Alternative when ABG unavailable; SpO₂/FiO₂ ≤315 (if SpO₂ ≤97%) correlates with ARDS criteria per the 2024 Global Definition [4]
- CBC: Leukocytosis (infection), anemia (hemorrhage, DAH), eosinophilia (eosinophilic pneumonia)
- BMP/CMP: Renal function, electrolytes, lactate (tissue perfusion)
- BNP/NT-proBNP: Helps differentiate cardiogenic vs. noncardiogenic edema
- Procalcitonin, CRP: Infection markers
- Blood cultures: All patients without obvious sterile insult [1]
- Coagulation studies: DIC screening in sepsis
- Sputum/tracheal aspirate cultures, respiratory viral panel [1]
- BAL: Consider for atypical pathogens (PJP, Legionella, Nocardia), eosinophilic pneumonia, DAH, alveolar proteinosis [1]
- Autoimmune panel (ANA, ANCA, anti-GBM): If no infectious cause identified [18]
12. Imaging
- Chest X-ray (first-line): Bilateral opacities not fully explained by effusions, atelectasis, or masses — required for Berlin definition [1][5]
- CT chest: Gold standard for characterizing opacities; identifies mimics (effusions, masses, ILD); quantifies recruitability; useful when CXR is equivocal or to identify intra-abdominal source [1][18]
- Lung ultrasound: Bilateral B-lines (≥3 per intercostal space in multiple fields) consistent with pulmonary edema/ARDS; portable, radiation-free, repeatable; accepted in the 2024 Global Definition especially for resource-limited settings. Limitation: cannot distinguish cardiogenic from noncardiogenic edema by B-lines alone [1][4]
- Echocardiography: Essential to exclude hydrostatic edema if no clear ARDS risk factor is present; assess RV function for acute cor pulmonale [2][18]
- Imaging is unnecessary for: routine serial monitoring if clinical trajectory is stable; however, worsening oxygenation should prompt repeat imaging
13. Special Tests
- Berlin Definition criteria (diagnostic standard): Acute onset ≤7 days, bilateral opacities, PaO₂/FiO₂ ratio on PEEP ≥5 cm H₂O, not fully explained by cardiac failure [1]
- 2024 New Global Definition: Expands to include high-flow nasal oxygen (≥30 L/min), SpO₂/FiO₂ ratio, and lung ultrasound [4]
- Driving pressure (Plateau pressure − PEEP): Target <15 cm H₂O; independently predicts mortality [8-9]
- Mechanical power: Emerging concept integrating multiple ventilator variables contributing to VILI [11]
- Esophageal manometry: Measures transpulmonary pressure to individualize PEEP in refractory cases [11]
- Electrical impedance tomography (EIT): Bedside tool for regional ventilation monitoring and PEEP titration [11]
- Bronchoscopy with BAL: Sensitivity ~58% for identifying infectious etiology; superior for fungal, Legionella, and atypical pathogens; also identifies DAH, eosinophilic pneumonia, alveolar proteinosis [1]
14. ECG
- Indications: All patients — to evaluate for cardiac ischemia as a precipitant or complication, and to assess for acute cor pulmonale
- Findings to recognize:
- Sinus tachycardia (most common)
- Right heart strain pattern: Right axis deviation, S1Q3T3, RV strain (T-wave inversions V1–V4), P-pulmonale
- New atrial fibrillation (common in critically ill patients with ARDS)
- ST changes suggesting ACS as a precipitant of cardiogenic edema (must be excluded)
15. Assessment
Severity stratification (Berlin Definition, on PEEP ≥5 cm H₂O): [1][5]
ARDS is significantly under-recognized — the LUNG SAFE study found that clinicians failed to recognize ARDS in ~40% of cases at the time of diagnosis, and only 31.4% of patients received initial lung-protective ventilation. [2][16] Complications include ventilator-induced lung injury, barotrauma, acute cor pulmonale, ICU-acquired weakness, and long-term cognitive/psychological sequelae. [2][11]
The following figure from the LUNG SAFE study demonstrates outcomes stratified by ARDS severity and driving pressure:
16. Treatment Plan
Initial Stabilization
- Secure airway; intubate if unable to maintain oxygenation on high-flow nasal oxygen or NIV
- Target SpO₂ 88–95%; avoid hyperoxia
Lung-Protective Ventilation (strong recommendation): [10][12][19]
- Tidal volume: 4–8 mL/kg predicted body weight (target 6 mL/kg)
- Plateau pressure: ≤30 cm H₂O
- Driving pressure: <15 cm H₂O
- PEEP ≥5 cm H₂O; higher PEEP suggested for moderate-to-severe ARDS (without recruitment maneuvers) [10]
- Prolonged recruitment maneuvers are recommended against (strong recommendation) [10]
Prone Positioning (strong recommendation for severe ARDS): [10][20]
- ≥12–16 hours/day for moderate-to-severe ARDS (PaO₂/FiO₂ <150 mm Hg)
- Combining low tidal volume with prone positioning is associated with the greatest mortality reduction [20]
Fluid Management
Pharmacotherapy
- Corticosteroids: Consider in moderate-to-severe ARDS within 14 days of onset [9-10]
- NMBAs: Intermittent boluses for severe ARDS with refractory hypoxemia or dyssynchrony; limit ≤48 hours [10][12]
- Treat underlying cause: Broad-spectrum antibiotics for suspected infection, source control [1]
Rescue Therapies for Refractory Hypoxemia
- Inhaled pulmonary vasodilators (iNO, epoprostenol) — improve oxygenation, no mortality benefit [11]
- VV-ECMO: Suggested for selected patients with severe ARDS refractory to conventional therapy; transfer to ECMO center [10-11]
Supportive Care: [1]
- DVT prophylaxis (subcutaneous heparin/LMWH)
- Stress ulcer prophylaxis
- Early enteral nutrition
- Sedation/analgesia titrated to comfort and ventilator synchrony
- Daily spontaneous breathing trials when FiO₂ ≤0.5 and PEEP ≤8 cm H₂O
17. Disposition
- All patients meeting ARDS criteria require ICU admission — there is no outpatient or floor-level management for established ARDS [2-3]
- Observation/step-down: May be appropriate for patients with resolving mild ARDS who are weaning from ventilatory support
- ECMO center transfer: Consider early for severe ARDS (PaO₂/FiO₂ <80) refractory to prone positioning and lung-protective ventilation [10-11]
- Specialist consultation triggers:
- Pulmonary/critical care: All cases
- Infectious disease: Atypical or refractory infections
- Surgery: If source control needed (intra-abdominal sepsis, trauma)
- Rheumatology: If autoimmune etiology suspected (vasculitis, DAH)
18. Follow Up / Return Precautions
- Survivors of ARDS are at significant risk for long-term sequelae: [2-3]
- Physical: Diminished functional capacity, ICU-acquired weakness, persistent pulmonary dysfunction
- Cognitive: Memory impairment, executive dysfunction
- Psychological: PTSD, depression, anxiety (up to 50% of survivors)
- Follow-up timing: Pulmonary function testing and clinical reassessment at 3–6 months post-discharge; earlier if symptomatic
- Pulmonary rehabilitation should be initiated early
- Primary care follow-up is essential for ongoing monitoring of physical, cognitive, and mental health recovery [3]
- Return precautions for discharged survivors: Worsening dyspnea, new fever, oxygen desaturation, chest pain, or functional decline should prompt immediate reassessment
References
1. Acute Respiratory Distress Syndrome. — Meyer NJ, Gattinoni L, Calfee CS. Lancet. 2021.
2. Acute Respiratory Distress Syndrome in Adults: Diagnosis, Outcomes, Long-Term Sequelae, and Management. — Gorman EA, O'Kane CM, McAuley DF. Lancet. 2022.
3. Acute Respiratory Distress Syndrome: Diagnosis and Management. — Saguil A, Fargo MV. American Family Physician. 2020.
4. A New Global Definition of Acute Respiratory Distress Syndrome. — Matthay MA, Arabi Y, Arroliga AC, et al. American Journal of Respiratory and Critical Care Medicine. 2024.
5. Acute Respiratory Distress Syndrome: Advances in Diagnosis and Treatment. — Fan E, Brodie D, Slutsky AS. The Journal of the American Medical Association. 2018.
6. Acute Respiratory Distress Syndrome. — Thompson BT, Chambers RC, Liu KD. The New England Journal of Medicine. 2017.
7. The Standard of Care of Patients With ARDS: Ventilatory Settings and Rescue Therapies for Refractory Hypoxemia. — Bein T, Grasso S, Moerer O, et al. Intensive Care Medicine. 2016.
8. Epidemiology, Patterns of Care, and Mortality for Patients With Acute Respiratory Distress Syndrome in Intensive Care Units in 50 Countries. — Bellani G, Laffey JG, Pham T, et al. The Journal of the American Medical Association. 2016.
9. Emergency Medicine Updates: Acute Respiratory Distress Syndrome. — Long B, Lentz S, Gottlieb M. The American Journal of Emergency Medicine. 2025.
10. An Update on Management of Adult Patients With Acute Respiratory Distress Syndrome: An Official American Thoracic Society Clinical Practice Guideline. — Qadir N, Sahetya S, Munshi L, et al. American Journal of Respiratory and Critical Care Medicine. 2024.
11. Management of Severe Acute Respiratory Distress Syndrome: A Primer. — Grotberg JC, Reynolds D, Kraft BD. Critical Care. 2023.
12. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2026. — Prescott HC, Antonelli M, Alhazzani W, et al. Critical Care Medicine. 2026.
13. Immunonutrition for Acute Respiratory Distress Syndrome (ARDS) in Adults. — Dushianthan A, Cusack R, Burgess VA, Grocott MP, Calder PC. The Cochrane Database of Systematic Reviews. 2019.
14. Optimizing Management of Acute Respiratory Distress Syndrome in Critically Ill Surgical Patients: A Systematic Review. — Zagales R, Lee P, Kumar S, et al. The Journal of Surgical Research. 2025.
15. Acute Respiratory Distress Syndrome: Causes, Pathophysiology, and Phenotypes. — Bos LDJ, Ware LB. Lancet. 2022.
16. American Association for the Surgery of Trauma/American College of Surgeons Committee on Trauma Clinical Protocol for Management of Acute Respiratory Distress Syndrome and Severe Hypoxemia. — Fawley JA, Tignanelli CJ, Werner NL, et al. The Journal of Trauma and Acute Care Surgery. 2023.
17. Acute Lung Injury and the Acute Respiratory Distress Syndrome: A Clinical Review. — Wheeler AP, Bernard GR. Lancet. 2007.
18. Diagnostic Workup for ARDS Patients. — Papazian L, Calfee CS, Chiumello D, et al. Intensive Care Medicine. 2016.
19. An Official American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine Clinical Practice Guideline: Mechanical Ventilation in Adult Patients With Acute Respiratory Distress Syndrome. — Fan E, Del Sorbo L, Goligher EC, et al. American Journal of Respiratory and Critical Care Medicine. 2017.
20. Comparative Effectiveness of Protective Ventilation Strategies for Moderate and Severe Acute Respiratory Distress Syndrome. A Network Meta-Analysis. — Sud S, Friedrich JO, Adhikari NKJ, et al. American Journal of Respiratory and Critical Care Medicine. 2021.