Morphometric investigation of pulmonary barotrauma: a study in forensic autopsies by SCUBA-diving

Abstract

Background: SCUBA-diving is one of the most popular and safely water sports activities in our country. Approximately 7 million divers are active worldwide. Although recreational diving is overall safe, diving accidents are potentially serious and even fatal. While there may be an initial presumption that all water-related deaths are accidental drownings, other possibilities must be considered, such as arterial gas embolism (AGE), decompression sickness, natural pathology, and trauma. PBt/AGE has been described as the cause of death in SCUBA diving in 13-24% of cases. Currently, the medical-forensic criteria for the diagnosis of PBt/AGE are based mainly on macroscopic autopsy and on imaging diagnostic techniques. Microscopic studies of pulmonary histopathology of PBt have not contributed specific changes to date. Certain authors describe pulmonary emphysema as a lesion characteristic of pulmonary barotrauma and experimental animal model studies, where pulmonary barotrauma has been artificially reproduced, have described microscopic changes in alveolar light with emphysema, atelectasis and haemorrhages. Complementary tests in cases of PBt/AGE are based mainly on conventional histopathological studies, not allowing an adequate assessment of the dimension of air spaces. Consequently, we propose the morphometric analysis of lung tissue to provide objective quantitative data of air spaces and their alterations in order to achieve more reliable data in the face of diagnose PBt/AGE. Objectives: 1) to describe frequency of acute pulmonary microscopic emphysema observed in lung tissue samples from forensic autopsies of PBt/AGE in context of SCUBA-diving as compared to those in forensic autopsies of drowning. 2) To analize differences in variables defining acute pulmonary microscopic emphysema observed in lung tissue samples from forensic autopsies of PBt/AGE in context of SCUBA-diving as compared to those in forensic autopsies of drowning. Design: the design of the study is cross-sectional and descriptive to be performed in Girona from 2018 to 2019. Population: the study population are people who died as a result of submersion diagnosed of drowning or PBt/AGE in a context of SCUBA-diving by a macroscopic autopsy. The collection have consisted on taking lung tissue samples of all autopsied corpses diagnosed of drowning and PBt/AGE in the province of Girona between 2014 and 2017. Sample have been stratified in two groups, according to the cause of death. Methods: Pulmonary histological preparations selected according to the type of death will be used, defining two groups (a group diagnosed of PBt/AGE and the other group diagnosed of drowning). For each histological preparation 5 fields will be selected. Each field will be photographed with a high resolution microscopic camera coupled to a triochial microscope. The captured images will be analyzed (to see the presence/absence of microscopic emphysema) and the following variables will be measured: total alveolar area, average alveolar diameter, alveolar density and average thickness of the alveolar wall. The morphometric analysis will be carried out by means of image analysis software. This project has been approved by the Comité de Ética de Investigación Clínica del Hospital Universitari de Bellvitge