Comparison of pulmonary autopsy findings of the rats drowned at surface and 50ft depth

Introduction : When a body is recovered from the water after a fatal SCUBA diving accident, it is useful to know if the diver was under pressure or not when he/she took his/her last breath, in order to determine the cause and manner of the death. If the victim was under pressure, the air remained in the lungs of the diver will be equal to the environmental pressure. If the body comes to the surface, the air in the lung will expand according to the Boyle's Gas Law and give mechanical damage to the surrounding tissues, due to decreases in environmental pressure. We designed an experimental study to see the difference in pulmonary autopsy findings of the rats that drowned under normobaric and hyperbaric conditions. Method : Forty five male, 250-300g, Sprague Downey adult rats were divided into three groups. Two groups of rats were drowned under normobaric conditions (Groups DS Group DSS) and the third group at 50ft pressure (Group DD). The pulmonary autopsy findings of the groups were compared. In the light microscopy, the number of the microscopic fields (×10) containing at least one emphysematous area with longitudinal dimension greater than 300μm were compared among the groups. Results : The gross examination revealed a prominent swelling of the lungs in all rats in the Group DD, in comparison to that of the Groups DS and DSS. The number of the microscopic fields, which included at least one emphysematous area with longitudinal dimension greater than 300μm out of 150 fields from each of the groups DS, DSS and DD, were 88, 101 and 115 respectively. The difference between the group DS and DD was found to be statistically significant. Conclusion : We conclude that in investigating the fatal diving accidents, pulmonary autopsy findings give valuable information whether the death occurred at the surface or at the depth.