Lung management during cardiopulmonary bypass: Is continuous positive airways pressure beneficial?

Abstract

It is not clear if the use of continuous positive airway pressure (CPAP) during cardiopulmonary bypass (CPB) improves lung function after cardiac surgery. We have measured alveolar-arterial oxygen partial pressure difference (PAo2 - PAo2) in 61 patients undergoing elective coronary artery bypass surgery. We studied three groups of patients: in group 1 the lungs were disconnected from the breathing system (no CPAP) during CPB; in group 2, 5 cm H2O CPAP with air was applied to the lungs; in group 3, 5 cm H2O of CPAP was applied with 100% oxygen. (PAo2 - PAo2) was measured before CPB and then at 30 min, 4 h and 8 h after CPB. Compared with group 1 (no CPAP), (PAo2 - PAo2) was significantly smaller in groups 2 and 3 at 30 min (P=0.036), but not at 4 h and 8 h after CPB (P=0.32, P=0.96). The time to extubation (P=0.42) and early extubation (P=0.87) were not affected by the use of CPAP. The results of this study do not support the use of CPAP during CPB as a mechanism of improving lung function after cardiac surgery. (Br. J. Anaesth. 1993; 71: 864-868) © 1993 British Journal of Anaesthesia.