Objective To explore the relation between the level of oxygen pressure and lactate in arterial blood and prognosis of cardiopulmonary resuscitation (CPR).Methods 36 patients with sudden cardiac arrest received CPR were selected.Patients were divided into 3 groups.The 21 patients who 30 minutes of CPR didn't regain heart beats were group A,those 10 who kept blood circulation for over 2 hours but finally died were group B,and the remaining 5 who survived were group C.Control group was made up of 20 people with no disease.In CPR immediately (0h),1h,3h,6h,12h were measured in blood specimens from arterial partial pressure of oxygen and lactate levels were compared among groups of patients dynamic changes of the index.Results The 3 groups A,B,C significantly reduced blood oxygen pressure,blood lactate increased significantly the CPR in the early,and compared with the control group there was significant difference( P ＜ 0.01 ).The group B CPR 3h,6h,and continue until no significant changes in 12h;The group C CPR 3h,6h began to increase blood oxygen pressure and blood lactate levels begin to decline,blood oxygen pressure increased significantly,lower blood lactate to a lower level after 12h.Taken with marked changes in B group,the difference was significant ( P ＜ 0.05 ).Conclusion Arterial partial pressure of oxygen and blood lactate levels could be used as indicators of prognosis of patients with CPR.Sustained increase in arterial oxygen partial pressure showed a good prognosis,lactate levels continued to rise that a poor prognosis.