Should we titrate ventilation based on driving pressure? Maybe not in the way we would expect

Mechanical ventilation maintains adequate gas exchange in patients during general anaesthesia, as well as in critically ill patients without and with acute respiratory distress syndrome (ARDS). Optimization of mechanical ventilation is important to minimize ventilator induced lung injury and improve outcome. Tidal volume (V-T), positive end-expiratory pressure (PEEP), respiratory rate (RR), plateau pressures as well as inspiratory oxygen are the main parameters to set mechanical ventilation. Recently, the driving pressure (Delta P), i.e., the difference of the plateau pressure and end-expiratory pressure of the respiratory system or of the lung, has been proposed as a key role parameter to optimize mechanical ventilation parameters. The Delta P depends on the V-T as well as on the relative balance between the amount of aerated and/or overinflated lung at end-expiration and end-inspiration at different levels of PEEP. During surgery, higher Delta P, mainly due to V-T, was progressively associated with an increased risk to develop post-operative pulmonary complications; in two large randomized controlled trials the reduction in Delta P by PEEP did not result in better outcome. In non-ARDS patients, Delta P was not found even associated with morbidity and mortality. In ARDS patients, an association between Delta P (higher than 13-15 cmH(2)O) and mortality has been reported. In several randomized controlled trials, when Delta P was minimized by the use of higher PEEP with or without recruitment manoeuvres, this strategy resulted in equal or even higher mortality. No clear data are currently available about the interpretation and clinical use of Delta P during assisted ventilation. In conclusion, Delta P is an indicator of severity of the lung disease, is related to V-T size and associated with complications and mortality. We advocate the use of Delta P to optimize individually V-T but not PEEP in mechanically ventilated patients with and without ARDS.