What is the recommended first‑line management protocol for an adult patient with moderate‑to‑severe acute respiratory distress syndrome (PaO₂/FiO₂ ≤150 mm Hg)?

ARDS Management Protocol for Moderate-to-Severe Disease (PaO₂/FiO₂ ≤150 mm Hg)

Immediate Ventilator Settings

Set tidal volume to 6 mL/kg predicted body weight (not actual weight) with an absolute plateau pressure ceiling of ≤30 cm H₂O. 1, 2

• Calculate predicted body weight using height and sex-specific formulas, never actual body weight, even in obese patients 2
• Start with tidal volume at 6 mL/kg PBW; you can range between 4-8 mL/kg PBW if needed to keep plateau pressure ≤30 cm H₂O 1, 2, 3
• Measure plateau pressure on every patient with ARDS using an inspiratory hold maneuver 1
• If plateau pressure exceeds 30 cm H₂O, reduce tidal volume further toward 4 mL/kg PBW 1, 2

PEEP Strategy

For moderate-to-severe ARDS (PaO₂/FiO₂ ≤150), use higher PEEP (≥10 cm H₂O) titrated upward in 2-3 cm H₂O increments as long as plateau pressure remains ≤30 cm H₂O. 1, 2, 3

• Start with PEEP of 10-12 cm H₂O 3
• Increase PEEP incrementally by 2-3 cm H₂O to optimize oxygenation, provided plateau pressure stays ≤30 cm H₂O and driving pressure (plateau pressure minus PEEP) does not increase 2, 3
• Target driving pressure ≤15 cm H₂O when possible 4
• Consider recruitment maneuvers in severe ARDS, though this is a weaker recommendation 1

Prone Positioning

Implement prone positioning for >12 hours per day immediately in patients with PaO₂/FiO₂ <150 mm Hg. 1, 2

• This is a strong recommendation with moderate-quality evidence showing mortality reduction 1, 2
• Duration must exceed 12 hours daily to achieve benefit 1, 2
• Continue prone positioning sessions until oxygenation improves consistently 2

Neuromuscular Blockade

Consider continuous cisatracurium infusion for ≤48 hours in patients with PaO₂/FiO₂ <150 mm Hg who have persistent ventilator dyssynchrony despite optimized settings. 1, 2, 5

• Administer 15 mg bolus followed by 37.5 mg/hour continuous infusion 5
• Ensure adequate sedation before initiating to prevent awareness 5
• Limit to first 48 hours only; discontinue as soon as lung mechanics improve 5
• Do not extend beyond 48 hours due to risk of ICU-acquired weakness 5

Fluid Management

Use a conservative fluid strategy targeting neutral to negative fluid balance in established ARDS without tissue hypoperfusion. 1, 2

• Avoid fluid overload as it worsens pulmonary edema and gas exchange 2
• Ensure adequate tissue perfusion first (normal lactate, adequate urine output, no vasopressor requirement) before restricting fluids 1

Sedation Strategy

Target light sedation (RASS -1 to +1) using analgesia-first approach unless deep sedation is required for lung-protective ventilation or prone positioning. 5

• Use protocolized sedation with daily interruption or intermittent bolus dosing rather than continuous deep sedation 5
• Reserve deep sedation only for: patients requiring neuromuscular blockade, those undergoing prone positioning, or those with plateau pressures >30 cm H₂O despite optimized settings 5
• Transition to lighter sedation as soon as oxygenation and respiratory mechanics improve 5

Additional Ventilator Management

Set respiratory rate to maintain pH >7.20-7.25 using permissive hypercapnia. 2, 4

• Adjust respiratory rate between 20-35 breaths per minute as needed 6
• Accept PaCO₂ elevation if pH remains >7.20 3

Elevate head of bed to 30-45 degrees to prevent ventilator-associated pneumonia. 1, 2

Titrate FiO₂ to maintain SpO₂ 88-95% to avoid hyperoxia. 6

What NOT to Do

Do not use high-frequency oscillatory ventilation—this is strongly recommended against. 1

• High-quality evidence shows no benefit and potential harm 1

Do not use beta-2 agonists unless bronchospasm is present. 1, 2

Do not routinely place pulmonary artery catheters. 1

Do not use tidal volumes >8 mL/kg PBW or allow plateau pressures >30 cm H₂O. 1, 2, 4

Monitoring and Weaning

Calculate mechanical power and target <17 J/min (definitely <22 J/min) using the formula: 0.098 × RR × Vt(L) × (PEEP + Driving Pressure). 4

Implement daily spontaneous breathing trials when patients meet criteria: arousable, hemodynamically stable without vasopressors, no new serious conditions, low PEEP requirements (<8 cm H₂O), and FiO₂ ≤0.4. 1, 2

• Use a weaning protocol to systematically assess readiness 1

Refractory Hypoxemia

For profound refractory hypoxemia (PaO₂/FiO₂ <80 mm Hg) after PEEP optimization, prone positioning, and neuromuscular blockade, consider early transfer to an ECMO-capable center. 3

• Inhaled vasodilators (nitric oxide, epoprostenol) may improve oxygenation but lack mortality benefit 3