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Driving pressure: the ventilator number that tracks mortality

Two patients on 6 mL/kg can be ventilated very differently. Driving pressure is the number that tells them apart.

William Owens, MD, Attending Intensivist Physician · Updated 2026-10-05

The calculation

It is the difference between the pressure holding the lung open at the top of a breath and the pressure holding it open at the bottom.

Plateau pressure is read during an inspiratory pause of about half a second, once flow has stopped. While gas is still moving, the pressure at the airway includes the resistive cost of pushing it down the tube, which has nothing to do with how distended the alveoli are.

Because plateau minus PEEP is also tidal volume divided by static compliance, driving pressure is really tidal volume indexed to how much lung is actually available to receive it.

Why it beats tidal volume

Lung-protective ventilation is usually taught as a volume rule: 6 mL/kg of predicted body weight. Predicted body weight is a good proxy for how big the lungs were when they were healthy. It says nothing about how much of them is still open.

In ARDS the lung is not uniformly stiff, it is small. The alveoli that remain aerated have roughly normal compliance; there are simply far fewer of them. A 70 kg adult with severe disease can be left with the functional lung volume of a child. Six milliliters per kilogram of the adult is a large breath for what is left.

Driving pressure captures that, because compliance falls as recruitable lung is lost. The same 6 mL/kg produces a driving pressure of 11 in a patient with 40 mL/cmH2O of compliance and 19 in a patient with 22.

The numbers

Bringing it down

• Lower the tidal volume. Four mL/kg is a legitimate setting in moderate to severe disease, and the CO2 that follows is usually tolerable.
• Adjust PEEP, in either direction, and measure again. More PEEP that recruits lung raises compliance and can lower driving pressure even though it raised plateau. More PEEP that only overdistends does the opposite. The measurement after the change is the only way to know which happened.
• Treat what is loading the lung: drain an effusion, decompress an abdomen, diurese the edema.
• In severe disease, prone positioning and neuromuscular blockade both act on the stress distribution rather than the global number, and both are worth reaching for before accepting a driving pressure that will not come down.

A caution about the chest wall

Driving pressure measured at the airway is the pressure across the lung and the chest wall together. In obesity, abdominal hypertension or chest-wall restriction, a large part of it is spent on the wall rather than on distending alveoli, and the airway number overstates the danger to the lung.

An esophageal balloon separates the two. If one is in place, the end-expiratory transpulmonary pressure is a better target than PEEP alone, and setting PEEP so it sits near zero prevents collapse without inflating what is already open.