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ΔP = Pplat − PEEP
Normal: < 15 cmH₂O; values > 15 cmH₂O independently associated with increased ARDS mortality
Driving pressure represents the pressure swing applied to the alveoli with each breath — the actual 'tidal stress' delivered to lung tissue. It normalizes tidal volume to the functional lung size (respiratory system compliance). A high driving pressure indicates that each breath is exerting excessive mechanical stress on available lung units.
Calculate in all ARDS patients on mechanical ventilation. When both Pplat ≤ 30 AND driving pressure ≤ 15 are achievable, lung protection is optimized. When Pplat is acceptable but ΔP remains high (e.g., high PEEP with stiff lungs), the tidal volume may still be causing harm.
→ 14 cmH₂O
Below 15 cmH₂O target — acceptable driving pressure
→ 22 cmH₂O
Exceeds target — reduce tidal volume or optimize PEEP
Amato et al. (NEJM 2015) showed that driving pressure was the ventilator variable most strongly associated with survival in ARDS — more so than tidal volume or PEEP in isolation. Driving pressure essentially normalizes tidal volume to the 'baby lung' — the functional lung size in ARDS. Target ΔP < 15 cmH₂O.