Perioperative tidal volume and intra-operative open lung strategy in healthy lungs: where are we going?

Tidal volumes have tremendously decreased over the last decades from <15 ml kg(-1) to approximately 6 ml kg(-1) actual body weight. Guidelines, widely agreed and used, exist for patients with acute lung injury or acute respiratory distress syndrome (ARDS). However, it is questionable if data created in patients with acute lung injury or ARDS from ventilation on intensive care units can be transferred to healthy patients undergoing surgery. Consensus criteria regarding this topic are still missing because only a few randomised controlled trials have been performed to date, focussing on the use of the best intra-operative tidal volume. The same problem has been observed regarding the application of positive end-expiratory pressure (PEEP) and intra-operative lung recruitment. This article provides an overview of the current literature addressing the size of tidal volume, the use of PEEP and the application of the open-lung concept in patients without acute lung injury or ARDS. Pathophysiological aspects of mechanical ventilation are elucidated.