How to Calculate Driving Pressure
Driving pressure is calculated as plateau pressure minus PEEP (ΔP = Plateau Pressure - PEEP). 1
The Formula
The calculation is straightforward:
- ΔP = Pplat - PEEP
Where:
- Pplat = Plateau pressure (measured during an inspiratory hold maneuver at zero flow)
- PEEP = Positive end-expiratory pressure (can be total PEEP including intrinsic PEEP)
Alternative Calculation Method
Driving pressure can also be calculated as the ratio of tidal volume to respiratory system compliance 2:
- ΔP = VT / Crs
This method yields equivalent results but requires measuring respiratory system compliance.
Key Measurement Considerations
Proper Measurement Technique
To accurately measure plateau pressure for driving pressure calculation 3:
- Perform an inspiratory hold maneuver during mechanical ventilation
- Ensure zero flow is achieved
- The plateau pressure (Pplat) is measured after the first pressure drop (P1) has occurred
- Account for total PEEP (tPEEP), which includes any intrinsic PEEP
Important Distinction from Peak Pressure
Do not confuse driving pressure with the dynamic pressure gradient (Peak Inspiratory Pressure - PEEP). The dynamic pressure gradient overestimates true driving pressure 2. Peak pressure includes resistive forces from airway resistance and flow, while plateau pressure reflects only elastic recoil of the respiratory system.
Clinical Significance
The 2017 ATS/ERS/SCCM guidelines note that driving pressure is a better predictor of outcome in ARDS than either tidal volume or plateau pressure alone 1. This is because driving pressure accounts for individual variations in respiratory system compliance—patients with stiffer lungs will have higher driving pressures for the same tidal volume.
Prognostic Thresholds
Recent evidence suggests:
- DP ≥ 15.72 cm H₂O is associated with increased ICU mortality 4
- Higher driving pressures are independently associated with increased time to extubation in mechanically ventilated children 2
Mode-Independent Application
Driving pressure can guide clinical decisions independent of ventilatory mode (volume-controlled vs. pressure-controlled ventilation) 3. The calculation remains valid across different ventilation strategies, though the measurement technique must account for the specific mode being used.