About possibility of using liquid respiration to prevent the development of decompression disorders

Abstract

Introduction. The problem of crew emergency evacuation after prolonged hyperbaric conditions is complicated by the extended decompression necessity. It is impossible to reach normal pressure conditions without risk of decompression sickness in the most cases due to large amount of dissolved indifferent gases in the tissues.
 
 Method for indifferent gases eliminating out of tissues to breathing liquid while liquid breathing is proposed. The absence of dissolved gases in the breathing liquid creates the pressure gradient that allows indifferent gases to diffuse through the alveolar-capillary barrier from the blood into the breathing liquid.
 
 The purpose of the study is to assess the possibility of liquid breathing application to prevent the development of decompression disorders after a long previous stay in conditions of excessive pressure of the gas environment.
 
 Materials and methods. Syrian hamsters, 4 months old, 120–140 g weight were used in the study. A mixture of perfluorodecalin and perfluorohexane 40:60 ratio was used as a breathing liquid. The animals were divided into four groups: control (№ 1) and three experimental by liquid breathing duration (№ 2, № 3 and № 4 was 15, 30 and 60 minutes, respectively). 
 For isobaric transition from gas to liquid breathing the special test bed was designed. The decompression sickness simulation in laboratory animals was carried out by ultrafast decompression (within 15 seconds) after a 60-minute exposure of 0.6 MPa air gauge pressure. The research method is based on the assessment of decompression disorders clinical picture and pathomorphological studies. The duration of the decompression sickness latent period, severity, animals’ lethality, the average animals’ lethal time, rectal temperature, results of pathomorphological examinations were evaluated. Results. Decompression sickness symptoms such as twitches, convulsions and paresis were observed in the № 1 group animals. Rather less explicit symptoms of decompression sickness were found in the group № 2 in comparison of group № 1. It was assessed by clinical pictures and pathomorphological examinations. Decompression sickness symptoms were not found in none of animals of the groups № 3 and № 4. Conclusions. The technology of liquid breathing with oxygenated and denitrogenated normobaric breathing liquid while hyperbaric conditions is possible to be applied for decompression sickness prevention. The dissolved in tissues nitrogen removal degree depends on the liquid breathing duration.