Protective Ventilation during One-lung Ventilation

Abstract

I read with interest the report by Michelet et al.1 For many years, hypoxemia was considered as the most important—if not the only—problem during one-lung ventilation (OLV). Therefore, the guidelines are primarily aimed at preventing and treating the hypoxemia.2 Since Katz et al.3 found that large tidal volumes produced the highest arterial oxygen tension (Pao2) during OLV, one can find in these guidelines that the tidal volume during OLV should be kept as high as in two-lung ventilation (i.e., 8–10–12 ml/kg).However, recent studies have shown that the lung injury after thoracotomy is also an important challenge in lung surgery, and the ventilatory setting (especially during OLV) is probably associated with this injury. So, a revision of the classic guidelines has been necessary.4 This article is indeed an important step in this revision after some in vitro5 and in vivo6 studies. However, in contrast to the current study, in the study of Schilling et al.,6 decreased tidal volumes were associated with a (statistically insignificant) decrease in Pao2 levels during OLV. This contrast may be a result of the fact that there was no positive end-expiratory pressure (PEEP) application in the control group in the current study. In several studies, it has been shown that PEEP was associated with an increase in oxygenation compared with zero end-expiratory pressure without any other change in ventilatory setting.7 So, PEEP should be considered as a prevention/treatment strategy both against hypoxemia and against lung injury. Furthermore, information about and comparison of the number of the patients in each group in whom the fraction of inspired oxygen has been increased to treat arterial hypoxemia would also be necessary.Therefore, I agree with authors that a protective ventilation (lower tidal volumes and PEEP) during OLV can lead to a decrease in lung injury during OLV; however, to argue that this method is also associated with improved oxygenation, a further study comparing low and high tidal volumes (with PEEP in both groups) would be necessary.