mechanics

Driving Pressure

ΔP = Pplat − PEEP

Normal: < 15 cmH₂O; values > 15 cmH₂O independently associated with increased ARDS mortality

Variables

ΔP

Driving pressure (tidal stress)(cmH₂O)

Normal: < 15 cmH₂O in ARDS

Pplat

Plateau pressure(cmH₂O)

Normal: < 30 cmH₂O

PEEP

Positive end-expiratory pressure(cmH₂O)

Normal: 5–15 cmH₂O in ARDS

What It Measures

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.

When to Use

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.

Interactive Calculator

Plateau Pressure (Pplat)(cmH₂O)

PEEP(cmH₂O)

Worked Examples

Acceptable lung protection

→ 14 cmH₂O

Below 15 cmH₂O target — acceptable driving pressure

High driving pressure in ARDS

→ 22 cmH₂O

Exceeds target — reduce tidal volume or optimize PEEP

Clinical Significance

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.

Memory Tips

💡Driving Pressure = the pressure SWING each breath applies to alveoli above their resting pressure (PEEP)
💡ΔP = Pplat − PEEP; it equals VT/Crs (tidal volume divided by respiratory compliance)
💡High ΔP = each breath is over-stretching available alveoli → volutrauma → more ARDS

NBRC Pearls

Driving pressure < 15 cmH₂O is the single strongest predictor of ARDS survival (Amato NEJM 2015)
ΔP = VT / Crs — when compliance is very low (small baby lung), even small tidal volumes cause high ΔP
PEEP optimization: if increasing PEEP reduces Pplat and increases compliance, it may REDUCE driving pressure

← All Formulas

What It Measures

Clinical Significance

NBRC Pearls

Driving pressure < 15 cmH₂O is the single strongest predictor of ARDS survival (Amato NEJM 2015)

ΔP = VT / Crs — when compliance is very low (small baby lung), even small tidal volumes cause high ΔP

PEEP optimization: if increasing PEEP reduces Pplat and increases compliance, it may REDUCE driving pressure