How does drive pressure affect ventilation strategy in mechanically ventilated patients?

Driving Pressure as a Primary Ventilator Target

Driving pressure (ΔP = plateau pressure - PEEP) should be maintained ≤15 cmH₂O as it predicts mortality better than tidal volume or plateau pressure alone in mechanically ventilated patients, and represents the functional lung stress applied to the "baby lung" available for ventilation in ARDS. 1

Why Driving Pressure Matters More Than Traditional Parameters

• Driving pressure reflects the ratio of tidal volume to respiratory system compliance, which indicates the actual "functional" size of the lung available for ventilation rather than predicted body weight 1
• In ARDS patients, the proportion of aerated lung is markedly decreased, making driving pressure a superior predictor of outcomes compared to tidal volume or plateau pressure measured independently 1
• Values exceeding 15 cmH₂O are associated with significantly increased mortality risk 1
• Recent evidence demonstrates that limiting daily dynamic driving pressure ≤15 cmH₂O reduces adherence-adjusted mortality from 20.1% to 18.1% (risk ratio 0.90) when added to traditional lung-protective ventilation 2

How to Implement Driving Pressure-Guided Ventilation

Initial Assessment

• Calculate driving pressure at the bedside: ΔP = plateau pressure - PEEP 1
• Measure plateau pressure during an inspiratory hold maneuver (requires sedation/paralysis for accuracy) 1
• If ΔP >15 cmH₂O, immediate adjustment is required 1, 2

Adjustment Algorithm When ΔP is Elevated

Option 1: Reduce tidal volume first

• Decrease tidal volume below 6 ml/kg PBW if necessary to achieve ΔP ≤15 cmH₂O 1
• Accept permissive hypercapnia unless contraindicated 1
• This approach directly reduces the numerator of the ΔP equation 1

Option 2: Optimize PEEP to improve compliance

• Increase PEEP to recruit collapsed alveoli and improve respiratory system compliance 1
• Higher PEEP reduces driving pressure when applied with constant plateau pressure by keeping the lung recruited 1
• For moderate-severe ARDS (PaO₂/FiO₂ <200), higher PEEP strategies reduce mortality (adjusted RR 0.90) 1

Option 3: Combined approach

• The combination of lower tidal volume and higher PEEP significantly reduced hospital mortality compared to higher tidal volume and lower PEEP 1
• This strategy works synergistically: lower VT reduces stress while higher PEEP improves compliance 1

Special Circumstances Where ΔP Guides Flexibility

• Low driving pressure may allow relaxation of strict tidal volume targets in patients with conflicting priorities (e.g., severe acidosis requiring higher minute ventilation) 1
• If a patient has high chest wall stiffness causing elevated plateau pressure but low driving pressure, the lung itself may not be experiencing excessive stress 1
• Dynamic driving pressure during spontaneous breathing may underestimate true transpulmonary driving pressure when expiratory muscle activity is present, limiting its usefulness as a surrogate for lung stress in actively breathing patients 3

Critical Pitfalls to Avoid

• Do not rely solely on tidal volume targets without checking driving pressure - patients with poor compliance may have injurious ΔP even at 6 ml/kg PBW 1
• Do not use driving pressure to titrate PEEP in isolation - while ΔP is an excellent severity indicator, trials that minimized ΔP by increasing PEEP with recruitment maneuvers showed equal or higher mortality 4
• Driving pressure ≥18 cmH₂O is specifically associated with right ventricular failure risk in ARDS patients, compounding hemodynamic instability 1
• Static driving pressure measurements require accurate plateau pressure measurement, which necessitates passive ventilation (sedation ± paralysis) 1, 3

Integration with Other Lung-Protective Strategies

• Maintain plateau pressure ≤30 cmH₂O as an absolute ceiling regardless of driving pressure 1
• Continue targeting tidal volumes 4-8 ml/kg PBW as the foundation of lung protection 1
• The effect of limiting ΔP is most pronounced with early and sustained intervention, not intermittent adjustments 2
• For severe ARDS with persistent ΔP >15 cmH₂O despite optimization, consider prone positioning >12 hours/day (reduces mortality with RR 0.74) 1 or ECMO for refractory cases 1