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

The debate on lung-protective ventilation strategies for surgical patients is ongoing. Evidence suggests that the use of low tidal volume V improves clinical outcomes. However, the optimal levels of PEEP and recruitment manoeuvre (RM) strategies incorporated into low V ventilation remain unclear.Several electronic databases were searched to identify RCTs that focused on comparison between low V strategy and conventional mechanical ventilation (CMV), or between two different low V 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.Compared with CMV, low V ventilation with moderate-to-high PEEP reduced the risk of PPCs (moderate PEEP [5-8 cm HO]: OR 0.50 [95% CrI: 0.28, 0.89]; moderate PEEP+RMs: 0.39 [0.19, 0.78]; and high PEEP [≥9 cm HO]+RMs: 0.34 [0.14, 0.79]). Low V 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 V ventilation with moderate PEEP was superior to CMV in reducing the risk of pneumonia (OR 0.46 [95% CrI: 0.15, 0.94]).The combination of low V ventilation and moderate-to-high PEEP (≥5 cm HO) seems to confer lung protection in surgical patients undergoing general anaesthesia.PROSPERO (CRD42019144561).