The Effects of Ventilation with Different Concentration of Oxygen on Lung Injury After Cardiopulmonary Bypass

【Objective】To investigate the effects of ventilation with 50% and 100% oxygen on lung injury after cardiopulmonary bypass(CPB).【Methods】Eighteen patients(aged 19~61,ASAⅡ~Ⅲ) undergoing valve replacement were randomized to receive 100% oxygen(group H,n=9) or 50% oxygen(group L,n=9) throughout surgery.Before CPB,1hour,6hours after CPB,blood samples were taken from radial artery and pulmonary artery for blood gas analysis.PaO2/FiO2,RI,Qs/Qt were calculated.SOD and MDA were determined in arterial blood sample before CPB and 60min after CPB.【Results】At 1hour after CPB,PaO2/FiO2 of two groups were lower than the levels before CPB.At 6 hours after CPB,PaO2/FiO2 were not different from the levels before CPB in Group L,but remained significantly lower in Group H.At 1hour after CPB,RI,Qs/Qt were higher than the levels before CPB in Group H.The change was not observed in Group L.Compared with group H,the production of MDA and depletion of SOD were tepid in group L at 1h after CPB.【Conclusion】Ventilation with 50% oxygen in patients undergoing valve replacement can alleviate lung injury.