Effect of lung insufflation with oxygen or air during cardiopulmonary bypass on post-bypass pulmonary dysfunction

ABSTRACT

Cardiopulmonary bypass [CPB] causes various abnormalities in the physical and functional properties of the lungs that initiate increases in pulmonary capillary endothelial permeability, decreases in lung compliance, and impaired gas exchange during the immediate postoperative period. This prospective randomized clinical trial was designed to investigate the effect of insufflating the lungs with 100% oxygen or air versus totally disconnecting the lungs and leaving them to collapse during cardiopulmonary bypass. Fifty-six adult patients undergoing CABG surgery with total CPB and aortic cross-clamping were included. Patients were randomly allocated to 1 of 3 groups that differed only in respiratory management during CPB; Group I [O [2] group, n=19] received 100% oxygen insufflation at 4 L/min. Group II [Air group, n=19] received air [FiO[2] 0.2] at the same flow rate. Group III [Collapse group, n=18] were totally disconnected from the anesthesia machine, and their lungs were left to collapse. PaO[2]/FiO[2] was significantly reduced in O2and Collapse groups in the post-CPB measurement compared to baseline but not in Air group [p<0.05]. In the postoperative period PaO[2]/FiO[2] was significantly higher in Air group compared to O[2] group, measured at 1 hour and 4 hours postoperatively [473 + 60 vs 407 + 90, and 476 +/- 39 vs 416 +/- 73 respectively, p<0.05] denoting a more rapid recovery of the lungs. Static and dynamic lung compliance were significantly reduced in the post-CPB and postoperative measurements in 0[2] and Collapse groups, but not in Air group [p<0.05]. Bronchoalveolar lavage [BAL] cytolines [TNF-alpha and IL-8] were significantly elevated in the post-CPB measurement in 02 group compared to baseline [12.1 [0 -42.1] vs 1 [0 - 17] pg, and 674 [50 - 8767] vs 217 [<10 - 2076] pg respectively, p<0.05], but not in Air or Collapse groups. TNF-alpha and IL-8 were significantly higher in O[2] group in the post-CPB measurement compared to both other groups [p<0.05]. Lung insufflation with air [without the application of mechanical ventilation or CPAP] during CPB has attenuated post-CPB pulmonary dysfunction compared to insufflation with 100% oxygen or disconnecting the lungs and leaving them to collapse. Oxygen on the other hand has caused an inflammatory response as evident by an increase in BAL cytokines