Recruitment maneuvers to reduce pulmonary atelectasis after cardiac surgery: A meta-analysis of randomized trials

Background: Pulmonary atelectasis is a common postoperative complication that may lead to intrapulmonary shunt, refractory hypoxemia, and respiratory distress. Recruitment maneuvers may relieve pulmonary atelectasis in patients undergoing cardiac surgery. We conducted a meta-analysis of randomized controlled trials to evaluate the effectiveness of recruitment maneuvers in these patients. Methods: We conducted a search in PubMed, Embase, Cochrane Library, and the ClinicalTrials.gov registry for trials published before March 2020. Individual effect sizes were standardized, and a meta-analysis was performed to calculate a pooled effect size by using random-effects models. Pulmonary atelectasis was assessed postoperatively. Secondary outcomes included hypoxic events, arterial oxygen tension (PaO2)/inspired oxygen fraction (FIO2) ratio, cardiac index, mean arterial pressure, and postoperative complications including pneumothorax and pneumonia. Results: We reviewed 16 trials involving 1455 patients. Patients receiving recruitment maneuvers had a reduced incidence of pulmonary atelectasis (group with recruited pressure >40 cmH2O: risk ratio [RR], 0.20; 95% confidence interval [CI], 0.07-0.57; group with recruited pressure <40 cmH2O: RR, 0.54; 95% CI, 0.33-0.89), reduced incidence of hypoxic events (RR, 0.23; 95% CI, 0.14-0.37), reduced incidence of pneumonia (RR, 0.42; 95% CI, 0.18-0.95), and improved PaO2/FIO2 ratio (weighted mean difference [WMD]; 58.87, 95% CI, 31.24-86.50) without disturbing the cardiac index (WMD, 0.22; 95% CI, –0.18 to 0.61) or mean arterial pressure (WMD, –0.30, 95% CI, –3.19 to 2.59) as compared with those who received conventional mechanical ventilation. The incidence of pneumothorax was nonsignificant between the groups. Conclusions: Recruitment maneuvers may reduce postoperative pulmonary atelectasis, hypoxic events, and pneumonia and improve PaO2/FIO2 ratios without hemodynamic disturbance in patients undergoing cardiac surgery.