ObjectiveTo investigate different levels of positive end-expiratory pressure (PEEP) on respiratory function and hemodynamics in patients with acute respiratory distress syndrome (ARDS) complicated with intra-abdominal hypertension(IAH). MethodsThirty patients with moderate ARDS admitted in ICU between January 2012 and December 2014 were recruited in the study. They were divided into three groups according to intra-abdominal pressure (IAP),including 10 patients with normal abdominal pressure as a normal IAP group,10 patients with IAP of 12-15 mm Hg as an IAPⅠ group,and 10 patients with IAP of 16-20 mm Hg as an IAPⅡ group. The optimal level of PEEP was titrated according to the best oxygenation methods. The changes of oxygenation index (OI),respiratory mechanics and hemodynamics before and after the optimal level of PEEP were monitored and compared in all groups. The 28-day mortality and ICU stay were also compared. ResultsThe OI after titration was significantly improved compared to baseline in all groups (all P<0.01). The OI after titration in the IAPⅡ group was significantly higher than that in other two groups (all P<0.05). The static lung compliance (Cst) after titration significantly improved than baseline in all groups(all P<0.05),but no significant difference was revealed among three groups (all P>0.05). In the IAPⅡ group,the levels of PEEP,IAP,blood lactate,heart rate and airway plateau pressure after titration were significantly increased than baseline but higher than those in other two groups(all P<0.05),while the level of mean arterial pressure was significantly decreased and significantly lower than those in other two groups(all P<0.01). Meanwhile,the ICU stay was longest in the IAPⅡ group (P<0.01). There was no significant difference in 28-day mortality among three groups(all P>0.05). ConclusionsPEEP can significantly improve oxygenation in patients with ARDS complicated with IAH. The higher the IAP is,the higher the PEEP level is required. However the higher PEEP will significantly increase IAP which will cause adverse impacts on hemodynamics and can not improve the prognosis.