Driving pressure is marker of severity and a possible target for lung protection during controlled ventilation, but its value during assisted ventilation is unknown. Inspiratory holds provide an estimate of driving pressure (quasi-static).

Expiratory holds provide an estimate of the inspiratory effort, useful to estimate the transpulmonary dynamic driving pressure.

Objectives: To assess the correlation between driving pressures measured during assisted ventilation and ICU outcomes.

Multicenter prospective observational study. Patients with acute hypoxemic respiratory failure were enrolled within 48 hours of triggering the ventilator.

Respiratory mechanics were measured daily and the variables of interest averaged over the first three days of partial assistance.

ICU outcomes were collected until day 90.

Measurements and Main Results: Two-hundred ninety-eight patients from 16 centers were enrolled.

Tidal volume, peak airway pressure, positive-end-expiratory-pressure and inspiratory effort during the first three days of assisted ventilation did not differ between survivors and non-survivors.

Quasi-static driving pressure and transpulmonary dynamic driving pressure were higher in non-survivors than in survivors, while compliance normalized to predicted body weight was lower.

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