Protective versus Conventional Ventilation for Surgery: A Systematic Review and Individual Patient Data Meta-analysis

Background: Recent studies show that intraoperative mechanical ventilation using low tidal volumes (V-T) can prevent postoperative pulmonary complications (PPCs). The aim of this individual patient data meta-analysis is to evaluate the individual associations between V-T size and positive end-expiratory pressure (PEEP) level and occurrence of PPC. Methods: Randomized controlled trials comparing protective ventilation (low V-T with or without high levels of PEEP) and conventional ventilation (high V-T with low PEEP) in patients undergoing general surgery. The primary outcome was development of PPC. Predefined prognostic factors were tested using multivariate logistic regression. Results: Fifteen randomized controlled trials were included (2,127 patients). There were 97 cases of PPC in 1,118 patients (8.7%) assigned to protective ventilation and 148 cases in 1,009 patients (14.7%) assigned to conventional ventilation (adjusted relative risk, 0.64; 95% CI, 0.46 to 0.88; P < 0.01). There were 85 cases of PPC in 957 patients (8.9%) assigned to ventilation with low V-T and high PEEP levels and 63 cases in 525 patients (12%) assigned to ventilation with low V-T and low PEEP levels (adjusted relative risk, 0.93; 95% CI, 0.64 to 1.37; P = 0.72). A dose-response relationship was found between the appearance of PPC and V-T size (R-2 = 0.39) but not between the appearance of PPC and PEEP level (R-2 = 0.08). Conclusions: These data support the beneficial effects of ventilation with use of low V-T in patients undergoing surgery. Further trials are necessary to define the role of intraoperative higher PEEP to prevent PPC during nonopen abdominal surgery.