AimTo investigate the therapeutic effect of Hydrogen inhalation on cardioplumonary bypass(CPB) induced acute lung injury(ALI) in Beagle dogs.MethodsCPB models were set up with living Beagle dogs.20 dogs were divided into hydrogen inhalation group(H₂ group) and control group(C group) randomly.Pulmonary artery pressue(PAP),pulmonary capillary wedge pressure(PCWP) and pulmonary vascular resisitance(PVR) were recorded at the five defined time points, artery blood samples were obtained for blood gas analysis and determined plasma cytokine levels(TNF-α,IL-6,IL-8) at the mean time.At the end of the research lung tissue were acquired for evaluation of pulmonary malondiadehyde(MDA)， superoxide dismutase(SOD), myeloperoxidase(MPO)，the ratio of wet to dry lung weight(W/D) and lung histopathology.Neutrophils and total protein content in bronchoalveolar lavage fluid(BALF) were also determined.ResultsCompared with control group, PAP,PCWP and PVR were significiantly improved in H₂ group.Neutrophils,total protein,differentiation in the lung W/D and cytokine content were lower than those in control group.Pulmonary MDA and MPO in hydrogen group were lower than those in control group, and the SOD was higher than that in control group.Histologic analysis showed that less lung injury by microscope examination was seen in hydrogen group than that in control group.Conclusion2% Hydrogen inhalation can alleviate CPB induced lung by inhibition of inflammatory and oxidative stress.