What are the recommended mechanical ventilation settings for patients with Acute Respiratory Distress Syndrome (ARDS)?

ARDS Mechanical Ventilation Settings

Core Ventilator Parameters

Use a tidal volume of 6 mL/kg predicted body weight (not actual body weight) with a plateau pressure target ≤30 cm H₂O for all patients with ARDS. 1, 2

Tidal Volume Strategy

• Set initial tidal volume at 6 mL/kg predicted body weight (PBW), which has demonstrated a 9% absolute mortality reduction compared to 12 mL/kg 3
• Calculate PBW using height and sex, never actual body weight—this is critical in obese patients to avoid excessive lung stretch 2
• Acceptable range is 4-8 mL/kg PBW if needed for individual patient factors, but target 6 mL/kg 1, 2
• Some patients may require volumes <6 mL/kg if plateau pressures exceed 30 cm H₂O despite standard settings 1

Plateau Pressure Management

• Maintain plateau pressure ≤30 cm H₂O through an inspiratory hold maneuver of 0.5-1.0 seconds 1, 4
• This pressure limit applies to total pressure (PEEP + driving pressure) 4
• Monitor driving pressure (plateau pressure minus PEEP) as it may be a better predictor of outcomes than tidal volume or plateau pressure alone 2
• If plateau pressure exceeds 30 cm H₂O despite 6 mL/kg tidal volume, reduce tidal volume further 1

PEEP Strategy

For moderate to severe ARDS (PaO₂/FiO₂ <200 mmHg), use higher PEEP levels (>10 cm H₂O); for mild ARDS, use lower PEEP (<10 cm H₂O). 1, 2

PEEP Titration by Severity

• Mild ARDS: Use lower PEEP strategy (<10 cm H₂O) to optimize oxygenation while minimizing hemodynamic compromise 2
• Moderate to severe ARDS: Use higher PEEP (>10 cm H₂O) to prevent alveolar collapse and improve oxygenation 1, 2
• Apply PEEP ≥5 cm H₂O minimum to avoid atelectotrauma in all ARDS patients 1, 5
• Titrate PEEP to optimize oxygenation while monitoring for hemodynamic compromise 2

Important caveat: While higher PEEP improves oxygenation in moderate-severe ARDS, one large trial showed no mortality difference between higher (mean 13.2 cm H₂O) versus lower (mean 8.3 cm H₂O) PEEP strategies when both groups used lung-protective tidal volumes 6. This suggests PEEP should be individualized based on oxygenation needs and hemodynamic tolerance.

Adjunctive Strategies for Severe ARDS

For severe ARDS with PaO₂/FiO₂ <150 mmHg, implement prone positioning for >12 hours per day. 1, 2

Prone Positioning

• Strong recommendation for PaO₂/FiO₂ ratio <150 mmHg (previously stated as ≤100 mmHg in 2012 guidelines, updated to <150 mmHg in 2016) 1
• Duration must exceed 12 hours per day to maximize mortality benefit 1, 2
• Requires facilities with experience in prone positioning techniques 1

Recruitment Maneuvers

• Consider recruitment maneuvers in severe ARDS with refractory hypoxemia 1
• This is a conditional recommendation with low confidence in effect estimates 1

Neuromuscular Blockade

• Consider cisatracurium for ≤48 hours in severe ARDS with PaO₂/FiO₂ <150 mmHg to improve ventilator synchrony 2, 7
• Particularly useful when plateau pressures exceed targets despite lung-protective settings 2

Additional Ventilator Management

Respiratory Rate and Oxygenation

• Set respiratory rate 20-35 breaths per minute to maintain adequate ventilation 5
• Titrate FiO₂ to SpO₂ 88-95% to prevent hyperoxia 5
• Avoid excessive oxygen exposure beyond what is needed for adequate tissue oxygenation 5

Patient Positioning and Aspiration Prevention

• Maintain head of bed elevated 30-45 degrees to limit aspiration risk and prevent ventilator-associated pneumonia 1, 2

Fluid Management

• Use conservative fluid strategy for established ARDS without evidence of tissue hypoperfusion 1, 2
• Avoid fluid overload as it worsens lung edema and gas exchange 2

What to Avoid

Do not use high-frequency oscillatory ventilation in moderate or severe ARDS. 1, 2

Contraindicated or Not Recommended Interventions

• High tidal volumes (>8 mL/kg PBW) increase ventilator-induced lung injury risk 1, 2
• High-frequency oscillatory ventilation has strong evidence against its use 1, 2
• Routine pulmonary artery catheter use is not recommended 1
• Beta-2 agonists should not be used unless bronchospasm is present 2

Noninvasive Ventilation

• Use noninvasive ventilation only in carefully selected minority of ARDS patients where benefits clearly outweigh risks 1
• The 2016 guidelines make no recommendation regarding NIV use, reflecting uncertainty about its role 1

Weaning Protocol

Implement spontaneous breathing trials regularly when patients meet readiness criteria. 1, 2

Criteria for Spontaneous Breathing Trial

• Patient is arousable 1
• Hemodynamically stable without vasopressor agents 1
• No new potentially serious conditions 1
• Low ventilatory and PEEP requirements 1
• Low FiO₂ requirements safely deliverable with face mask or nasal cannula 1
• If trial successful, consider extubation 1, 2