The effect of different lung-protective strategies in patients during cardiopulmonary bypass: A meta-analysis and semiquantitative review of randomized trials

Objectives: A variety of lung-protective techniques, including continuous positive airway pressure and vital capacity maneuvers, have been suggested as beneficial when applied during cardiopulmonary bypass (CPB). To better define the efficacy of these techniques, a systematic review of different ventilation strategies during and after CPB was performed. Design: A systematic review and meta-analysis according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations. Setting: Hospitals. Participants: Eight hundred fourteen participants of 16 randomized controlled trials. Interventions: Continuous positive airway pressure (CPAP), low-volume ventilation, or vital capacity maneuvers (VCMs) during CPB. Measurements and Main Results: The methodologic validity of the included trials was scored according to the Oxford scale. Included trials had to report on at least 1 of the following parameters: oxygenation, oxygenation index, alveolar-arterial oxygen difference, or shunt fraction. The average quality of the included trials was as low as 2 on a scale from 1 to 5. The use of CPAP or VCM during CPB led to a significant increase in oxygenation parameters immediately after weaning from CPB, but this effect was not sustainable and did not improve patient outcome. Conclusions: This meta-analysis showed that the positive effects of the designated techniques are probably short-lived with a questionable impact on the long-term clinical outcome of the treated patients. Based on the available data, it might be impossible to advise an optimal or best-evidence strategy of lung preservation during CPB.