How do you manage driving pressure (the difference between plateau pressure and positive end-expiratory pressure (PEEP)) during mechanical ventilation?

Managing Driving Pressure During Mechanical Ventilation

Target a driving pressure ≤15 cmH₂O as your primary ventilator goal, as this threshold predicts mortality better than tidal volume or plateau pressure alone and represents the functional stress applied to the aerated "baby lung" in ARDS patients. 1

Understanding Driving Pressure

• Driving pressure (ΔP) is calculated as plateau pressure minus PEEP, and reflects the ratio of tidal volume to respiratory system compliance rather than predicted body weight 1
• This parameter indicates the actual functional size of lung available for ventilation, which is markedly decreased in ARDS where the proportion of aerated lung is substantially reduced 1
• Values ≥18 cmH₂O are specifically associated with right ventricular failure risk in ARDS patients, compounding hemodynamic instability 2, 1

Measurement Technique

• Measure plateau pressure during an inspiratory hold maneuver (requires adequate sedation/paralysis for accuracy) and subtract PEEP to calculate ΔP 1
• Perform measurements in volume-controlled ventilation with inspiratory pause >0.5 seconds and no intrinsic PEEP, or in pressure-controlled mode with constant support level and sufficient equilibration time at end-inspiration and end-expiration 2

Adjustment Algorithm When ΔP >15 cmH₂O

Step 1: Reduce Tidal Volume

• Decrease tidal volume below 6 mL/kg PBW if necessary to achieve ΔP ≤15 cmH₂O, as this takes priority over strict adherence to the 6 mL/kg target 1, 3
• In trauma patients requiring ≥48 hours of mechanical ventilation, limiting dynamic ΔP to <15 cmH₂O reduces 30-day mortality (OR 2.4 for ΔP ≥15) and ventilator-induced lung injury incidence (OR 2.2) 4

Step 2: Optimize PEEP

• Increase PEEP to recruit collapsed alveoli and improve respiratory system compliance, which can lower ΔP by increasing the denominator (compliance) 1
• For moderate-severe ARDS (PaO₂/FiO₂ <200), higher PEEP strategies reduce mortality (adjusted RR 0.90) 1
• Balance PEEP to avoid both lung derecruitment (which increases RV afterload) and overdistension (which impairs pulmonary circulation and RV function) 2

Step 3: Adjust Respiratory Rate

• When tidal volume is reduced to achieve target ΔP, decrease respiratory rate to maintain minute ventilation and prevent excessive mechanical power, accepting permissive hypercapnia if needed 5
• In one study, transitioning from PBW-guided to ΔP-guided ventilation increased tidal volume from 6.1 to 7.7 mL/kg PBW while decreasing respiratory rate from 29 to 21 breaths/min, resulting in 7% reduction in mechanical power 5

Critical Thresholds to Maintain

• Maintain plateau pressure ≤30 cmH₂O as an absolute ceiling regardless of driving pressure, even if this requires further reduction in tidal volume 1, 3
• Continue targeting tidal volumes 4-8 mL/kg PBW as the foundation of lung protection 1, 3
• Four modifiable risk factors for RV failure include: PaO₂/FiO₂ <150 mmHg, driving pressure ≥18 cmH₂O, and PaCO₂ ≥48 mmHg—all adjustable through ventilator settings 2

Advanced Strategies for Refractory Cases

• For severe ARDS with persistent ΔP >15 cmH₂O despite optimization, consider prone positioning >12 hours/day (reduces mortality with RR 0.74), which improves ventilation uniformity and may restore RV function 1
• Prone positioning has been shown to restore RV function in patients with previously overloaded right ventricles, potentially explaining mortality benefit beyond gas exchange improvement 2
• Consider ECMO for refractory cases where lung-protective ventilation cannot be achieved 1

Important Caveats

• Low driving pressure may allow relaxation of strict tidal volume targets in patients with conflicting priorities such as severe acidosis requiring higher minute ventilation 1
• Avoid respiratory modalities that promote high mean airway pressure and lung overdistension (such as high-frequency oscillation with high PEEP baseline), as these worsen prognosis through hemodynamic impairment and RV failure 2
• Driving pressure is an indicator of disease severity and is associated with complications and mortality, but should be used primarily to optimize tidal volume rather than PEEP titration 6
• When all four RV failure risk factors are present (including ΔP ≥18 cmH₂O), the risk of RV failure exceeds 60%, whereas when no factors are present the risk is <10% 2