Objective:To investigate the protective effects of prostaglandin E1(PGE1) on lung injury by regulating inflammatory system during cardiopulmonary bypass(CPB). Methods:From March to June in 2006,a total of 24 patients undergoing cardiac surgery were randomly divided into the control group(n = 12) and the experimental group(n = 12). Each patient in the experimental group received 15 ng(kg·min). min-1 of PGE1 from the induction of anaesthesia to the end of CPB. Blood PMN and Plt in left and right atrium were measured at 5 min before CPB and 15 min after heart resuscitation. The levels of sE-selectin and CRP in serum were measured at 5 min before CPB,30 min on CPB,15 min after heart resuscitation,1 h and 6 h after CPB. Oxygenation index(OI)and compliance of lung(CL) were also recorded in both groups. Results:①PMN and Plt count in the blood in left atrium were significantly lower than that in right atrium at 15 min after heart resuscitation in the control group(P < 0.01). ②During and after CPB,the level of sE-selectin increased in both groups, but it was significantly higher in the control group than that in the experimental group(P < 0.01). ③During and after CPB, the level of CRP in the experimental group was significantly lower than that in the control group(P < 0.01).④Compared with the control group, OI was significantly lower(P < 0.01) and CL was significantly higher in the experimental group(P < 0.01) at the end of CPB. Conclusion:PGE1 can effectively reduce the sequestration of neutrophil and platelet in the lungs,inhibit the activation of vascular endothelial cells and protect lungs during CPB.