Impact of gas emboli and hyperbaric treatment on respiratory function of loggerhead sea turtles (Caretta caretta).

Cyril Portugues,Jordi Altimiras,Alicia Borque-Espinosa,Andreas Fahlman,Daniel García-Párraga,Jose Luis Crespo-Picazo,Teresa Lorenzo

doi:10.1093/conphys/cox074

Abstract

Fisheries interactions are the most serious threats for sea turtle populations. Despite the existence of some rescue centres providing post-traumatic care and rehabilitation, adequate treatment is hampered by the lack of understanding of the problems incurred while turtles remain entrapped in fishing gears. Recently it was shown that bycaught loggerhead sea turtles (Caretta caretta) could experience formation of gas emboli (GE) and develop decompression sickness (DCS) after trawl and gillnet interaction. This condition could be reversed by hyperbaric O2 treatment (HBOT). The goal of this study was to assess how GE alters respiratory function in bycaught turtles before recompression therapy and measure the improvement after this treatment. Specifically, we assessed the effect of DCS on breath duration, expiratory and inspiratory flow and tidal volume (VT), and the effectiveness of HBOT to improve these parameters. HBOT significantly increased respiratory flows by 32-45% while VT increased by 33-35% immediately after HBOT. Repeated lung function testing indicated a temporal increase in both respiratory flow and VT for all bycaught turtles, but the changes were smaller than those seen immediately following HBOT. The current study suggests that respiratory function is significantly compromised in bycaught turtles with GE and that HBOT effectively restores lung function. Lung function testing may provide a novel means to help diagnose the presence of GE, be used to assess treatment efficacy, and contribute to sea turtle conservation efforts.

Highlights

Decompression sickness (DCS), or ‘the bends’, is caused by the formation of gas bubbles, most commonly N2, in blood and tissues after reduction in pressure occurs during ascent from a dive (Mahon and Regis, 2014)
The current study suggests that respiratory function is significantly compromised in bycaught turtles with gas emboli (GE) and that hyperbaric O2 treatment (HBOT) effectively restores lung function
In turtles that underwent HBOT (n = 8), the expiratory flow increased an average of 32% and the inspiratory flow increased an average of 45% following HBOT

Summary

Introduction

Decompression sickness (DCS), or ‘the bends’, is caused by the formation of gas bubbles, most commonly N2, in blood and tissues ( called gas embolism) after reduction in pressure occurs during ascent from a dive (Mahon and Regis, 2014). DCS symptoms range in severity from skin rashes and tissue distortion to central. Of 67 bycaught turtles, 29 were found to have GE, and the bubbles resolved upon recompression treatment. These results provided a definitive diagnosis that marine vertebrates can experience DCS, at least under unnatural circumstances. The authors found that turtles with a high number of bubbles often had respiratory distress and frequently died (GarcíaPárraga et al, 2014; Fahlman et al, 2017a), the extent to which GE affects the respiratory system is not known

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