AUTHOR=Koutnik Andrew P. , Favre Michelle E. , Noboa Karina , Sanchez-Gonzalez Marcos A. , Moss Sara E. , Goubran Bishoy , Ari Csilla , Poff Angela M. , Rogers Chris Q. , DeBlasi Janine M. , Samy Bishoy , Moussa Mark , Serrador Jorge M. , D’Agostino Dominic P. TITLE=Human Adaptations to Multiday Saturation on NASA NEEMO JOURNAL=Frontiers in Physiology VOLUME=11 YEAR=2021 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.610000 DOI=10.3389/fphys.2020.610000 ISSN=1664-042X ABSTRACT=

Human adaptation to extreme environments has been explored for over a century to understand human psychology, integrated physiology, comparative pathologies, and exploratory potential. It has been demonstrated that these environments can provide multiple external stimuli and stressors, which are sufficient to disrupt internal homeostasis and induce adaptation processes. Multiday hyperbaric and/or saturated (HBS) environments represent the most understudied of environmental extremes due to inherent experimental, analytical, technical, temporal, and safety limitations. National Aeronautic Space Agency (NASA) Extreme Environment Mission Operation (NEEMO) is a space-flight analog mission conducted within Florida International University’s Aquarius Undersea Research Laboratory (AURL), the only existing operational and habitable undersea saturated environment. To investigate human objective and subjective adaptations to multiday HBS, we evaluated aquanauts living at saturation for 9–10 days via NASA NEEMO 22 and 23, across psychologic, cardiac, respiratory, autonomic, thermic, hemodynamic, sleep, and body composition parameters. We found that aquanauts exposed to saturation over 9–10 days experienced intrapersonal physical and mental burden, sustained good mood and work satisfaction, decreased heart and respiratory rates, increased parasympathetic and reduced sympathetic modulation, lower cerebral blood flow velocity, intact cerebral autoregulation and maintenance of baroreflex functionality, as well as losses in systemic bodyweight and adipose tissue. Together, these findings illustrate novel insights into human adaptation across multiple body systems in response to multiday hyperbaric saturation.