Abstract
Background: The present study was designed to observe if different decompression profiles,
calculated as a function of tissue supersaturation during ascent, would result in significantly
different outcomes, measured through different physiological stress indicators, even in the absence
of symptoms of decompression sickness.
Aim: The aim of this study was to evaluate if simulated decompression profiles would affect the
immune system, oxidative stress indicators, and heart rate variability.
Methods: A total of 23 volunteers participated in two different experimental protocols in a dry
hyperbaric chamber. These simulated dives comprised two different compression–decompression
arrangements with the same maximum pressure and duration but different decompression profiles.
Results: The shallow decompression profile with shorter deeper stops and longer shallow stops
presented an increase in the standard deviation of the normal-to-normal R-R interval (a wide
indicator of overall variability); the deep decompression profile with longer deeper stops and shorter
shallow stops did not exhibit such increase. The shallow decompression profile resulted in an
increase in neutrophil count and its microparticles (MPs), but no changes were observed for platelet
count and its MPs, as well as for endothelial-derived MPs. In contrast, the deep decompression
profile resulted in no changes in neutrophil count and its MPs, but a decrease in platelet count along
with an increase in MPs from both platelets and endothelial cells. The observed difference might
be related to different levels of decompression-related activation of immune system responses and
oxidative processes triggered by different levels of inert gas supersaturation upon surfacing.
Conclusion: From previous results and literature data, we present a tentative schematic of how
the velocity of ascent would trigger (or not) pro-inflammatory and immune system responses that
could ultimately lead to the development of decompression sickness.
Relevance for patients: Increasing safety in exposure to hyperbaric environments and subsequent
decompression by evaluating individual physiological responses to the process.
DOI: https://doi.org/10.36922/jctr.24.00021
Author affiliation
1Department of Physiology, Biosciences Institute, University of São Paulo, São Paulo, Brazil
2Peter Murányi Experimental Research Center,
Albert Einstein Hospital, São Paulo, Brazil
3DAN Europe Research Division, Roseto Degli Abruzzi, Italy, 4Environmental Physiology and
Medicine Laboratory, Department of Biomedical Sciences, University of Padova, Padova, Italy
*Corresponding author:
Sergio Rhein Schirato
Department of Physiology, Biosciences
Institute, University of São Paulo, São Paulo,
Brazil
Email: sergio.schirato@gmail.com
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