Abstract: Objective To identify serum proteins differentially expressed in patients undergoing different ventilation modes during thoracic operations. Methods Ten patients underwent one-lung ventilation（group A） and 10 underwent two-lung ventilation（group B） during thoracic operations. Serum samples were collected， and highly abundant serum proteins were purified on an immunoaffinity chromatography column.The iTRAQ technique combined with two-dimensional liquid chromatography tandem mass spectrometry （2D LC-MS/MS） was used to identify and quantitate proteins differentially expressed between the two groups. Results A total of 189 pro-teins were identified by mass spectrometry，and 42 proteins were differentially up-or down-regulated by at least 20%.Of these proteins，33 were up-regulated and 9 were down-regulated in group A compared to group B. Conclusions The iTRAQ technique is effective for comparative proteomic studies.Protein expression profiling may prove a useful approach for investigating the pathogenesis of lung injury in patients undergoing one-lung ventilation.

Key words:  One-lung ventilation, Lung injury, Proteomics, iTRAQ technology, biochemical marker