Intraoperative ventilation strategies to prevent postoperative pulmonary complications: a network meta-analysis of randomised controlled trials

Abstract Background The debate on lung-protective ventilation strategies for surgical patients is ongoing. Evidence suggests that the use of low tidal volume VT improves clinical outcomes. However, the optimal levels of PEEP and recruitment manoeuvre (RM) strategies incorporated into low VT ventilation remain unclear. Methods Several electronic databases were searched to identify RCTs that focused on comparison between low VT strategy and conventional mechanical ventilation (CMV), or between two different low VT strategies in surgical patients. The primary outcome was postoperative pulmonary complications (PPCs). The secondary outcomes were atelectasis, pneumonia, acute respiratory distress syndrome, and short-term mortality. Bayesian network meta-analyses were performed using WinBUGS. The odds ratios (ORs) and corresponding 95% credible intervals (CrIs) were estimated. Results Compared with CMV, low VT ventilation with moderate-to-high PEEP reduced the risk of PPCs (moderate PEEP [5–8 cm H2O]: OR 0.50 [95% CrI: 0.28, 0.89]; moderate PEEP+RMs: 0.39 [0.19, 0.78]; and high PEEP [≥9 cm H2O]+RMs: 0.34 [0.14, 0.79]). Low VT ventilation with moderate-to-high PEEP and RMs also specifically reduced the risk of atelectasis compared with CMV (moderate PEEP+RMs: OR 0.36 [95% CrI: 0.16, 0.87]; and high PEEP+RMs: 0.41 [0.15, 0.97]), whilst low VT ventilation with moderate PEEP was superior to CMV in reducing the risk of pneumonia (OR 0.46 [95% CrI: 0.15, 0.94]). Conclusions The combination of low VT ventilation and moderate-to-high PEEP (≥5 cm H2O) seems to confer lung protection in surgical patients undergoing general anaesthesia. Clinical trial registration PROSPERO (CRD42019144561)