What is the treatment for acute respiratory distress syndrome (ARDS)?

Treatment of Acute Respiratory Distress Syndrome (ARDS)

The cornerstone of ARDS treatment is lung-protective mechanical ventilation with tidal volumes of 4-8 mL/kg predicted body weight and plateau pressure ≤30 cmH₂O, combined with prone positioning for at least 12 hours daily in severe cases, while treating the underlying cause. 1

Initial Respiratory Support Decision

For patients with mild ARDS who are hemodynamically stable, alert, and cooperative without pneumonia as the etiology, consider a trial of high-flow nasal cannula starting at 30-40 L/min with FiO₂ 50-60%. 1 However, proceed immediately to intubation in a controlled setting if any of the following occur within 1 hour: deterioration, FiO₂ exceeds 70%, or flow exceeds 50 L/min. 1 Patients requiring intubation after failed noninvasive support have worse outcomes, so close monitoring during this trial is critical. 2

For moderate-to-severe ARDS or any patient with pneumonia as the underlying cause, proceed directly to intubation and mechanical ventilation. 1

Lung-Protective Mechanical Ventilation Protocol

Set the ventilator using these mandatory parameters:

• Tidal volume: 4-8 mL/kg predicted body weight (not actual body weight) 1
• Plateau pressure: ≤30 cmH₂O at all times 1
• PEEP: Use the ARDS-network PEEP-to-FiO₂ grid for moderate-to-severe ARDS, monitoring continuously for hemodynamic compromise 1
• Target SpO₂: 92-96% and PaO₂: 70-90 mmHg 1

Low tidal volume ventilation is the only ventilatory strategy proven protective in all ARDS patients. 2 Higher PEEP strategies work in specific subsets but can be harmful in others, requiring careful hemodynamic monitoring. 2

Fluid Management Strategy

Implement conservative fluid management to minimize pulmonary edema while maintaining adequate organ perfusion. 1 Excessive fluid administration represents a "second hit" that aggravates lung injury and should be avoided. 2, 3 Monitor urine output and lactate to ensure adequate perfusion while restricting fluids.

Adjunctive Therapies for Severe ARDS (PaO₂/FiO₂ <150 mmHg)

Prone Positioning (First-Line for Severe ARDS)

Implement prone positioning for at least 12 hours per day in severe ARDS, as this has demonstrated significant mortality reduction. 1 This becomes mandatory when PaO₂/FiO₂ falls below 150 mmHg and especially below 100 mmHg. 4

Neuromuscular Blockade

Consider cisatracurium infusion for 24-48 hours after ARDS onset in severe ARDS to improve ventilator synchrony, reduce oxygen consumption, and potentially improve outcomes. 1 This is particularly useful when patients demonstrate injurious respiratory effort despite optimized ventilator settings. 4

ECMO Consideration

Initiate ECMO evaluation when PaO₂/FiO₂ remains <100 mmHg despite lung-protective ventilation, prone positioning, and neuromuscular blockade. 4 ECMO improves gas exchange and modestly improves survival by allowing lung rest in select refractory cases. 5

Treatment of Underlying Cause (Essential)

Rapidly identify and treat the underlying etiology—this is the only causal treatment measure. 1, 6 Before assuming typical ARDS, establish a diagnostic protocol to identify ARDS-mimics that require specific therapies:

ARDS-Mimics Requiring Different Treatment

• Diffuse interstitial lung diseases (acute interstitial pneumonia, organizing pneumonia, acute eosinophilic pneumonia) may require corticosteroids 3
• Diffuse pulmonary infections (Pneumocystis jirovecii, viral pneumonitis, disseminated fungal infections, miliary tuberculosis) require pathogen-specific antimicrobials 3
• Drug/chemical-induced lung disease (vaping-induced injury, chemotherapy pneumonitis, amiodarone toxicity) requires immediate drug withdrawal 3
• COVID-19 pneumonia benefits from dexamethasone, unlike typical ARDS 1, 3

Obtain detailed exposure history (occupational, environmental, medications, vaping, recreational drugs), consider bronchoscopy with bronchoalveolar lavage (diagnostic yield 41% in treatment failures), and evaluate for systemic disease markers. 3

Monitoring Requirements

Monitor continuously:

• Oxygen saturation and arterial blood gases 1
• Respiratory mechanics (plateau pressure, driving pressure, compliance) 1
• Hemodynamics 1
• Right ventricular function via echocardiography, as RV failure significantly worsens outcomes 1

Reclassify severity at 24 hours, as this is more predictive of mortality than initial values. 4

Critical Pitfalls to Avoid

Avoid these iatrogenic "second hits" that aggravate lung injury:

• Excessive fluid administration 2, 1
• Blood product transfusions 2
• Injurious mechanical ventilation (high tidal volumes, high plateau pressures) 2

Do not assume all bilateral infiltrates with hypoxemia are typical ARDS—establish a diagnostic protocol to identify treatable ARDS-mimics, as only a minority of patients meeting Berlin criteria actually have diffuse alveolar damage at autopsy. 3, 4

Inhaled nitric oxide is ineffective in adult ARDS and is not indicated, despite acute improvements in oxygenation showing no effect on days alive and off ventilator support. 7

Therapies Without Proven Mortality Benefit

While the following may improve oxygenation, they do not clearly reduce mortality and should be used judiciously:

• Recruitment maneuvers 5
• Inhaled pulmonary vasodilators 5, 8
• Glucocorticoids (except in COVID-19 ARDS or suspected fibroproliferation) 2, 5