ObjectiveTo systematically evaluate the benefits and harms of intraoperative positive end-expiratory pressure (PEEP) to all adult patients suffered surgery, especially on the postoperative mortality and pulmonary outcomes. MethodsWe electronically searched PubMed, EMbase, The Cochrane library (Issue 3, 2012), CBM, CNKI from inception to January 2013, for randomized controlled trials (RCTs) about PEEP for the prevention of pulmonary complications. Two reviewers independently screened literature according to the inclusion and exclusion criteria, extracted the data, and evaluated the quality of the included studies. Then meta-analysis was conducted using RevMan 5.1 software. ResultsA total of 8 RCTs involving 336 patients were finally included. The results of meta-analysis showed that there was no difference between two groups in mortality (OR=0.95, 95%CI 0.13 to 6.92, P=0.96). However, the PEEP group had a higher PaO2/FiO2 the first day after surgery (MD=22.98, 95%CI 4.40 to 41.55, P=0.02), while there was no difference 2-3 days after surgery (MD=12.59, 95%CI-6.78 to 31.96, P=0.31). Meanwhile, postoperative atelectasis was less in the PEEP group (OR=0.27, 95%CI 0.08 to 0.9, P=0.03). ConclusionChoosing PEEP mode during general anaesthesia may improve postoperative oxygenation index in the first day after surgery, and reduce pulmonary complications, which has a protective effect on patients pulmonary function. However, it has no marked influence on the prognosis. Because of the limited quality and sampling size of the induced studies, this conclusion still needs to be further proved by more large-scale, multicenter and perspective RCTs.