EFFECT OF CPAP DURING CARDIOPULMONARY BYPASS ON POSTOPERATIVE LUNG-FUNCTION - AN EXPERIMENTAL-STUDY

Background: Respiratory failure secondary to cardiopulmonary bypass (C PB) remains a major complication after cardiac surgery. We tested the hypothesis that post-CPB lung function impairment can be prevented by continuous positive airway pressure (CPAP) applied during the CPB. Met hods: In 6 pigs, CPAP with 5 cmH(2)O pressure was applied during CPB. Six other pigs served as control, i.e. the lungs were open to the atmo sphere during CPB. After median sternotomy, the right atrial appendage as well as the ascending aorta were cannulated. The total CPB duratio n was 90 min with 45 min cardioplegic arrest. Ventilation-perfusion di stribution was measured with the multiple inert gas elimination techni que and atelectasis by CT-scanning. Results: Large atelectasis appeare d after CPB, corresponding to 14.5%+/-5.5 (percent of the total lung a rea) in the CPAP group and 18.7%+/-5.2 in the controls (P=0.20). Intra pulmonary shunt increased and PaO2 decreased after the CPB in both gro ups. Conclusions: We conclude that in this pig model post-CPB atelecta sis is not effectively prevented by CPAP applied during CPB.