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

Postbypass pulmonary dysfunction including atelectasis and increased shunting is a common problem in the intensive care unit. Negative net fluid balance and continuous positive airway pressure (CPAP) have been used to reduce the adverse effects of cardiopulmonary bypass (CPB) on the lung. To determine whether CPAP at 10 cm H2O during CPB results in improved postoperative gas exchange in comparison with deflated lungs during CPB, we examined 14 patients scheduled for elective cardiac surgery. Seven patients received CPAP at 10 cm H2O during CPB, and in the other seven patients, the lungs were open to the atmosphere (control). Measurements were taken before and after CPB, after thoracic closure, and 4 h after CPB in the intensive care unit. CPAP at 10 cm H2O resulted in significantly more perfusion of lung areas with a normal ventilation/ perfusion distribution (V-A/Q) and significantly less shunt and low V-A/Q perfusion 4 h after CPB in comparison with the control group. Consequently, arterial oxygen partial pressure was significantly higher and alveolar-arterial oxygen partial pressure difference was significantly smaller. We conclude that CPAP at 10 cm H2O during CPB is a simple maneuver that improves postoperative gas exchange.