Open AccessBreathing 100% oxygen during water immersion improves postimmersion cardiovascular responses to orthostatic stress
Author(s) -
Florian John P.,
Chon Ki H.,
Faes Luca,
Shykoff Barbara E.
Publication year - 2016
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.13031
Subject(s) - presyncope , medicine , orthostatic intolerance , heart rate , blood pressure , cardiology , orthostatic vital signs , vascular resistance , stroke volume , room air distribution , hemodynamics , anesthesia , respiratory minute volume , respiratory system , physics , thermodynamics
Physiological compensation to postural stress is weakened after long‐duration water immersion ( WI ), thus predisposing individuals to orthostatic intolerance. This study was conducted to compare hemodynamic responses to postural stress following exposure to WI alone (Air WI), hyperbaric oxygen alone in a hyperbaric chamber (O 2 HC ), and WI combined with hyperbaric oxygen (O 2 WI ), all at a depth of 1.35 ATA , and to determine whether hyperbaric oxygen is protective of orthostatic tolerance. Thirty‐two healthy men underwent up to 15 min of 70° head‐up tilt ( HUT ) testing before and after a single 6‐h resting exposure to Air WI ( N = 10), O 2 HC ( N = 12), or O 2 WI ( N = 10). Heart rate ( HR ), blood pressure ( BP ), cardiac output (Q), stroke volume ( SV ), forearm blood flow ( FBF ), and systemic and forearm vascular resistance ( SVR and FVR ) were measured. Although all subjects completed HUT before Air WI , three subjects reached presyncope after Air WI exposure at 10.4, 9.4, and 6.9 min. HUT time did not change after O 2 WI or O 2 HC exposures. Compared to preexposure responses, HR increased (+10 and +17%) and systolic BP (−13 and −8%), and SV (−16 and −23%) decreased during HUT after Air WI and O 2 WI , respectively. In contrast, HR and SV did not change, and systolic (+5%) and diastolic BP (+10%) increased after O 2 HC . Q decreased (−13 and −7%) and SVR increased (+12 and +20%) after O 2 WI and O 2 HC , respectively, whereas SVR decreased (−9%) after Air WI . Opposite patterns were evident following Air WI and O 2 HC for FBF (−26 and +52%) and FVR (+28 and −30%). Therefore, breathing hyperbaric oxygen during WI may enhance post‐ WI cardiovascular compensatory responses to orthostatic stress.