Study Of Direct Lung Injury By Seawater In Canine Models

Objective To construct an animal model in order to provide a platform for studying and treating direct lung injury by seawater. MethodsIn order to exclude the effects of hypoxia and acidosis on the study of the direct lung injury mechanism by seawater, 18 common hybrid dogs in good health were evenly assigned into 3 groups at random: group A with all lobes of lung instilled by seawater; group R with the right lobe of lung instilled by seawater and group D with the diaphragmatic lobe of lung instilled by seawater. The changes in Hemodynamics, blood gas acid-base and electrolyte, the histiocytic changes in lung and the continuous changes in tertiary bronchiole under a bronchial microscope before and after seawater instillation were observed and compared respectively. The concentrations of bronchoalveolar fluid and blood LDH-L and ALP were tested. Results The values of PaO2,PaCO2, PH, AB, BE, Vt, and RR in groups A and R were significantly different from those in group D (P<0.01). The values of PaO2, PaCO2, PH, AB, BE, Vt, and RR at every stage before seawater instillation were significantly different from those after seawater instillation in groups A and R (P<0.01). However, the values in Hemodynamics, blood gas acid-base and blood gas electrolyte before seawater instillation were insignificantly different from those after seawater instillation in Group D statistically (P>0.05). In all groups, injuries, congestive edema and local wine-colored sheet-like changes and infarctional hemorrhage foci were evidently seen in the lung tissues with seawater instillation. Alveolar edema, alveolar collapse, marked pulmonary interstitial congestive edema and the infiltration of neutrophilic granulocyte in large numbers and pulmonary hemorrhage were observed under the microscope. Meanwhile, the observation under the electron microscope demonstrated that type II alveolar epithelial cells were injured, respiratory mucosa were broadened, plateletadhered to walls. Continuous observation under the bronchial microscope in Group D showed that bronchoalveolar fluid flooded at different degrees into bronchus instilled with seawater and the concentrations of blood LDH-L and ALP continued to go up, which was significantly different compared with groups A and R (P<0.01). It was found in the study as well that in 4 hours no abnormal changes in pulmonary tissues were histomorphologically seen in the lungs without seawater instillation.Conclusion In all groups, lung injury occurred after seawater instilled. The occurrence and severity of hypoxia and acidosis were positively associated with the areas in the lungs with seawater instillation. In Group D, the injuries in the lung were obvious after eliminating the roles of hypoxia and acidosis. Therefore, the seawater left over in the lungs after seawater drowning can lead to direct severe lung injury , which is a primary factor resulting in acute lung injury.