ARDS Diagnosis and Management
Diagnose ARDS using the Berlin Definition criteria and manage with lung-protective ventilation as the foundation, escalating to prone positioning for severe cases, while avoiding pharmacologic therapies that have consistently failed to improve outcomes.
Diagnostic Criteria
ARDS is diagnosed when all of the following Berlin Definition criteria are met within 1 week of a known clinical insult: 1, 2, 3
- Acute onset of bilateral pulmonary opacities on chest imaging not fully explained by cardiac failure, fluid overload, or other causes 1, 4
- Arterial hypoxemia with PaO₂/FiO₂ ≤300 mmHg on minimum PEEP of 5 cmH₂O 5, 1
- Respiratory failure not fully explained by cardiac failure or fluid overload (clinical assessment or echocardiography may be needed) 4, 3
Severity classification based on PaO₂/FiO₂ ratio: 1, 6, 3
- Mild: 200-300 mmHg
- Moderate: 100-200 mmHg
- Severe: <100 mmHg
Common Diagnostic Pitfalls
- Clinician interpretation of chest radiographs and origin of edema shows poor reliability, potentially leading to underrecognition of ARDS 3
- Differentiate from cardiogenic pulmonary edema (which typically shows signs of fluid overload) and pneumonia 4
Initial Respiratory Support Strategy
Noninvasive Ventilation
Consider high-flow nasal cannula or noninvasive ventilation only in mild ARDS with close monitoring, as failure rates are high in moderate-to-severe cases 5, 2. Proceed to early intubation in a controlled setting if deterioration occurs rather than emergent intubation 2.
Lung-Protective Mechanical Ventilation (Foundation of Management)
Immediately implement lung-protective ventilation in all intubated ARDS patients: 1, 2, 6
- Tidal volume: 4-8 mL/kg predicted body weight (not actual body weight) 1, 2, 6
- Plateau pressure: ≤30 cmH₂O 1, 2, 6
- Higher PEEP strategy in moderate-to-severe ARDS without prolonged recruitment maneuvers 1, 2, 6
- Target SpO₂ no higher than 96% to avoid oxygen toxicity 2
Avoid prolonged lung recruitment maneuvers (strong recommendation) as they do not improve outcomes and may cause harm 1, 2, 6.
PEEP Titration
Titrate PEEP to optimize oxygenation while monitoring for hemodynamic compromise and right ventricular dysfunction 1. Higher PEEP improves outcomes in moderate-to-severe ARDS but requires careful monitoring of driving pressure and plateau pressure 1, 7.
Adjunctive Therapies for Severe ARDS
Prone Positioning (Mortality Benefit Proven)
Implement prone positioning for >12 hours daily (ideally 12-16 hours) in severe ARDS with PaO₂/FiO₂ <100 mmHg, as this intervention has demonstrated significant mortality reduction 1, 2, 6. This is one of the few interventions with proven survival benefit beyond lung-protective ventilation 3, 8.
Common pitfall: Delaying prone positioning in severe ARDS reduces its effectiveness 6.
Neuromuscular Blocking Agents
Consider neuromuscular blocking agents in early severe ARDS to improve ventilator synchrony, reduce oxygen consumption, and potentially improve outcomes 1, 2, 6. This is a conditional recommendation with low certainty of evidence 2, 6.
Corticosteroids
Consider systemic corticosteroids for ARDS (conditional recommendation, moderate certainty), particularly in patients with fibroproliferation or COVID-19 ARDS where mortality benefit has been shown 1, 2, 6. However, the evidence remains mixed for non-COVID ARDS 8.
Fluid Management
Implement a conservative fluid management strategy to minimize pulmonary edema while maintaining adequate organ perfusion 1, 2, 6.
Critical pitfall: Excessive fluid administration worsens oxygenation, promotes right ventricular failure, and increases mortality 1, 6. Monitor fluid balance carefully and avoid fluid overload 2, 6.
Advanced Therapies for Refractory Hypoxemia
Veno-Venous ECMO
Consider VV-ECMO in selected patients with severe ARDS (PaO₂/FiO₂ <100 mmHg) who fail conventional management, particularly those with reversible disease 5, 1, 2. This modestly improves survival by allowing lung rest 8.
Inhaled Pulmonary Vasodilators
Consider a trial of inhaled pulmonary vasodilators (e.g., inhaled nitric oxide) as rescue therapy for severe hypoxemia despite optimized ventilation, but discontinue if no rapid improvement in oxygenation 2. Avoid routine use as it does not improve mortality 2.
High-Frequency Oscillatory Ventilation
Avoid high-frequency oscillatory ventilation in moderate-to-severe ARDS as it does not improve outcomes and may cause harm 1, 3.
Pharmacologic Therapies to Avoid
Do not use the following pharmacologic interventions, as they have failed to show benefit and may cause harm: 3
- β2 agonists
- Statins
- Keratinocyte growth factor
- Aspirin for ARDS prevention
These therapies targeted underlying pathophysiology but demonstrated no benefit or possible harm in clinical trials 3.
Monitoring Requirements
Continuously monitor the following parameters: 2, 6
- Oxygen saturation (maintain >95% but ≤96%) 2, 6
- Respiratory mechanics (driving pressure, plateau pressure, dynamic compliance) 1
- Hemodynamics and right ventricular function via echocardiography 2, 6
- Signs of acute cor pulmonale, especially with higher PEEP strategies 6
Weaning and Liberation from Mechanical Ventilation
Perform daily spontaneous breathing trials once the patient's condition improves, as this consistently reduces duration of mechanical ventilation 5.
For patients at high risk for extubation failure, use noninvasive ventilation after extubation to reduce ICU length of stay and mortality 5.
Consider tracheostomy when prolonged mechanical ventilation is anticipated, though it should not be routine in every ARDS patient 5.
Key Management Pitfalls to Avoid
- Underutilization of proven therapies: Lung-protective ventilation and prone positioning remain underused despite strong evidence 6, 3
- Delayed prone positioning in severe ARDS reduces effectiveness 6
- Excessive fluid administration worsens outcomes 1, 6
- Inappropriate ventilator settings causing high driving pressure and mechanical power increase VILI risk 7, 8
- Failure to monitor for right ventricular dysfunction with higher PEEP strategies 6