Continuous positive airway pressure at 10 cm H2O during cardiopulmonary bypass improves postoperative gas exchange

Postbypass pulmonary dysfunction including atelectasis and increased shunti ng is a common problem in the intensive care unit. Negative net fluid balan ce and continuous positive airway pressure (CPAP) have been used to reduce the adverse effects of cardiopulmonary bypass (CPB) on the lung. To determi ne whether CPAP at 10 cm H2O during CPB results in improved postoperative g as exchange in comparison with deflated lungs during CPB, we examined 14 pa tients scheduled for elective cardiac surgery. Seven patients received CPAP at 10 cm H2O during CPB, and in the other seven patients, the lungs were o pen to the atmosphere (control). Measurements were taken before and after C PB, after thoracic closure, and 4 h after CPB in the intensive care unit. C PAP at 10 cm H2O resulted in significantly more perfusion of lung areas wit h a normal ventilation/ perfusion distribution (V-A/Q) and significantly le ss shunt and low V-A/Q perfusion 4 h after CPB in comparison with the contr ol group. Consequently, arterial oxygen partial pressure was significantly higher and alveolar-arterial oxygen partial pressure difference was signifi cantly smaller. We conclude that CPAP at 10 cm H2O during CPB is a simple m aneuver that improves postoperative gas exchange.