Comparison on the features between seawater-induced and freshwater-induced acute lung injuries

Objective To compare the features and differences between seawater-induced and freshwater-induced acute lung injuries in rat models.Methods Ninety SD rats were randomly divided into three groups(30 each):control group,seawater drowning group and freshwater drowning group.Rats in the latter 2 groups were given 4ml/kg seawater or freshwater intratracheally to induce acute lung injury,and 6 rats in each group were taken for observation at 30min,1h,2h,4h and 8h time points.Blood gas was monitored and wet/dry weight(W/D) of lung tissue was determined.Pulmonary microvascular permeability(PMVP) was examined with Evan's blue assay.The content of TNF-α in serum and bronchoalveolar lavage fluid(BALF) was measured by ELISA,and pathological changes in lung tissues were observed under microscope.Results After inhalation of freshwater or seawater,PaO2 decreased remarkably(P0.05),and more declination was found in seawater drowning group than the freshwater drowning group.W/D of lung tissue,PMVP and the contents of TNF-α in serum and BALF of both seawater and freshwater drowning groups were higher than that of control group(P0.05),and it was evidently higher in seawater drowning group than in freshwater drowning group(P0.05).Pathological changes,including interstitial edema and alveolar edema,focal hemorrhage in pulmonary tissues,inflammatory cells,especially neutrophil infiltration,were found to be more serious in seawater drowning group than in freshwater drowning group.Conclusion The pulmonary injuries induced by seawater drowning,such as hypoxemia,lung edema and inflammatory reaction,are more serious compared to that induced by freshwater drowning.