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 (VT), 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 (ΔP), 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 ΔP depends on the VT 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 ΔP, mainly due to VT, was progressively associated with an increased risk to develop post-operative pulmonary complications; in two large randomized controlled trials the reduction in ΔP by PEEP did not result in better outcome. In non-ARDS patients, ΔP was not found even associated with morbidity and mortality. In ARDS patients, an association between ΔP (higher than 13–15 cmH2O) and mortality has been reported. In several randomized controlled trials, when ΔP 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 ΔP during assisted ventilation. In conclusion, ΔP is an indicator of severity of the lung disease, is related to VT size and associated with complications and mortality. We advocate the use of ΔP to optimize individually VT but not PEEP in mechanically ventilated patients with and without ARDS.