BACKGROUND: Injured lungs due to gastric acid aspiration may be rejected for transplantation because of the possibility of early graft dysfunction. We hypothesized that diluted surfactant administration during ex vivo perfusion would recondition the lungs injured by acid aspiration and permit their use as suitable grafts for transplantation. METHODS: Using a pig model, lung injury was induced with 5-ml/kg administration of a betaine-HCl/pepsin mixture via a flexible bronchoscope. After injury, animals were randomly assigned to three study groups (n = 6/group): saline lavage during ex vivo perfusion (control); surfactant lavage ex vivo (SL-Exvivo); and surfactant lavage before harvest (SL-Pre); and a normal group (n = 4), with no lung injury. Cold storage time was 3 hours. A volume of 10 ml/kg (4 mg/ml, 40 mg/kg) surfactant (Curosurf) was used for lavage. Bronchoalveolar lavage (BAL) was performed before and after injury and at the end of the experiment. Protein and neutrophil percentage in BAL were assessed. Hemodynamic and aerodynamic parameters were measured every 30 minutes during a 2-hour observation period. RESULTS: An approximately 50% decrease in Pao(2) was observed in all animals after injury. Ex vivo surfactant lavage resulted in lower pulmonary vascular resistance, lower oxygenation index and higher Pao(2)/Fio(2) ratio compared with the control group (p = 0.001, p = 0.0001 and p = 0.0001, respectively, according to analysis of variance for repeated measures). Wet-to-dry weight ratio was lower in the SL-Exvivo group compared with the control group (p = 0.015). BAL neutrophil percent at the end of the experiment differed significantly between control and all other groups (p < 0.05). CONCLUSION: Diluted surfactant lavage during ex vivo perfusion improves graft function of lungs injured by gastric acid aspiration.