Effects of Positive Airway Pressure and Mechanical Ventilation of the Lungs During Cardiopulmonary Bypass on Pulmonary Adverse Events After Cardiac Surgery: A Systematic Review and Meta-Analysis.

OBJECTIVE: To investigate whether different ventilation strategies during cardiopulmonary bypass (CPB) can improve outcomes in adult cardiac surgery patients.

DESIGN: Systematic review of randomized controlled trials with meta-analyses.

SETTING: Clinical trials for human studies up to July 2016 were obtained from electronic databases (Medline, Embase, PubMed, and the Cochrane Central Register of Controlled Trials) and reference lists of relevant randomized trials and review articles.

PARTICIPANTS: Adult patients undergoing cardiac surgery.

INTERVENTIONS: Patients who underwent cardiac surgery with CPB and ventilation or continuous positive airway pressure (CPAP).

MEASUREMENTS AND MAIN RESULTS: Fifteen randomized controlled trials with 748 patients were analyzed. In cardiac surgery, CPAP use during CPB was associated with an improved alveolar-arterial oxygen gradient difference compared with no CPAP (weighted mean difference [WMD] = 4.11 kPa; 95% confidence interval [CI] = 0.85-7.37; I2 = 28.8%). Ventilation during CPB did not improve the postoperative hypoxemia score (WMD = 30.94; 95% CI = -20.76 to 82.63; I2 = 61%) or diffusion capacity compared with the apnea group (WMD = 2.59 kPa; 95% CI = -2.49 to 7.67; I2 = 81.3%). Neither CPAP nor ventilation during CPB was associated with a shorter mechanical ventilation time or hospital stay.

CONCLUSIONS: CPAP during CPB improved the alveolar-arterial oxygen gradient difference compared with apnea, but ventilation during CPB did not. Neither CPAP nor ventilation during CPB demonstrated evidence of improving clinical outcomes in low- or intermediate-risk patients for elective cardiac surgery. The findings are inconclusive because of heterogeneity and small sample sizes.