Abstract： Objective To investigate the therapeutic effects of delayed lung lavage with exogenous pulmonary surfactant(PS)diluent on endogenous surfactant system dysfunction and acute respiratory failure caused by severe smoke inhalation in rats.Method Ninety Wistar rats were randomly separated into five groups:Group I,normal control(n=14);Group Ⅲ,smoke inhalation(n=27);GroupⅢ,smoke+PS lavage+mechanical ventilation(MV),n=21;Group IV,smoke+saline lavage+MV,n=10;Group V,smoke+MV,n=18.The lungs were lavaged with 30 ml/kg normal ssdine containing 100 mg/kg PS or same volume of saline via tra cheal catheter at 2 h after smoke inhalation,then the animals were placed on a ventilator for 4 h,and observed until 24 h after injury.The arterial blood gas level,lung water volume,static lung compliance(Cst),total protein and albumin contents in bronchoalveolar lavage fluid(BALF),surface tension properties of BALF,and fatality rate at 24 h were measured.Results Smoke inhalation caused a similar acute hypoxia and severe carbon monoxide poisoning immediately in all injured groups.The animals in group Ⅱ showed acute respiratory failure,serious hish permeability pulrnonary edema,and surfactant system dysfunction.The surface tension properties of BALF and Cst were significantly improved by delayed lung lavage treated with exogenous PS diluent in group m(P<0.05).However,the lung water volume,total protein and albumin contents in BALF and the oxygenation had not significant difference between group Ⅲ and group Ⅱ(P>0.05).Conclusions Delayed lung lavage with exogenous PS diluent,at a certain extemt,restored endogenous suffactant function inhibited by smoke inhalation and improved lung function.Nevertheless,the trent could not alleviate rash permeability pulmonary edema and respiratory failure drarnatically.The expected decrease of mortality at early stage after smoke inhalation injury was not showed yet.