Abstract: Objective:To evaluate the effects of atomization inhalation of dexmedetomidine on heme oxygenase-1 expression in lung tissues and Qs/Qt during one-lung ventilation in rats.Methods:Forty-eight male SD rats weighed 300-350 g were randomly divided into the two-lung ventilation group(group C),one-lung ventilation group(group O),intravenous injection dexmedetomidine group(group V) and atomization inhalation dexmedetomidine group(group I)(12 rats each group).The group C was coped with two-lung ventilation for 1 h(tidal volume of 10 mL/kg,ventilatory frequency of 60/min and respiration ratio of 1:2) after endotracheal intubation.The O,V and I groups were treated with right lung ventilation for 1 h(tidal volume of 5 mL/kg,ventilatory frequency of 80/min and respiration ratio of 1:2) after endotracheal intubation.The group V was injected with 5 μg/kg of dexmedetomidine at the speed of 2.5 μg·kg^-1·h^-1 from before operation to the end of operation.The group I was coped with atomization inhalation of 0.1 μg dexmedetomidine combined with 4 mL 0.9% sodium chloride solution before 10 min of operation,oxygen flow for 2 L/min,and the 1 μg dexmedetomidine was continuously inhaled after endotracheal intubation.The group C and group O were coped with the same volume of 0.9% sodium chloride solution.The arterial blood gas,respiratory index(RI),oxygenation index(OI) and Qs/Qt were detected before mechanical ventilation(T0),at the end of mechanical ventilation(T1) and after 30 min of mechanical ventilation(T2).The contents of TNF-α,IL-6 and IL-10 in lung tissue were detected using ELISA assay,the W/D and expression of heme oxygenase-1(HO-1) were examined,and the pathobiology change of lung tissue was observed.Results:Compared with the group C,the contents of TNF-α,IL-6 and IL-10 in lung tissues and W/D increased,the expression of HO-1 upregulated,the RI at T1and T2 increased,the QI decreased and QS/Qt increased in group O,group V and group I(P<0.05 to P<0.01).Compared with the group O,the contents of TNF-α and IL-6 in lung tissues and W/D decreased,the content of IL-10 increased,the expression of HO-1 upregulated,the RI decreased,the QI increased,the QS/Qt decreased,and the pathological injury alleviated in group V and group I(P<0.01).The differences of all indexes between group V and group I were not statistically significant(P>0.05).Conclusions:The atomization inhalation of dexmedetomidine can attenuate the lung injury induced by one-lung ventilation in rats,the mechanism of which maybe involves in the upregulation of HO-1 expression,and decreasing of Qs/Qt.