Objective To observe the effect of intraoperative 5 cm H2O positive end expiratory pressure on vascular endothelial function in patients with uvulopalatopharynplasty (UPPP ). Methods Forty patients with obstructive sleep apnea-hypopnea syndrome (OSAHS)scheduled for UPPP were selected,including 25 males and 15 females,fully met the following conditions as age<60 years,BMI<30 kg/m2and ASA physical status Ⅰ or Ⅱ.Patients were divided into two groups, 20 in each group using random number table method.The observation group was given the intermit-tent positive pressure ventilation (IPPV)with 5 cm H2O PEEP,while the controls group were given IPPV.3 ml of arterial blood was drawn at the time of 5 min of pure oxygen Inhalation (T0),intuba-tion (T1),extubation (T2),and 20 min after extubation (T3).Vascular endothelium expansion fac-tors such as nitric oxide (NO),endothelin (ET),and soluble cell adhesion molecule (CAMs)were detected by ELISA.Results There was no significant difference in plasma ET concentrations between the two groups at different time points.Plasma NO concentration in the observation group was signif-icantly higher than that in the control group at T2and T3(P<0.05).Compared with T0,the concen-trations of CAMs in the control groups from T1to T3,and in the observation group at T2and T3in-creased significantly (P<0.05).In the perioperative period,the plasma CAMs of the control group increased along with the prolongation of the operation time,but the plasma CAMs concentrations in the observation group decreased in the same observation time (P<0.05).Conclusion Low level of PEEP 5 cm H2O may improve endothelial function in general anesthesia patients with OSAHS.