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15-03-2024 | Original Article

Hemorrhage at high altitude: impact of sustained hypobaric hypoxia on cerebral blood flow, tissue oxygenation, and tolerance to simulated hemorrhage in humans

Authors: Alexander J. Rosenberg, Garen K. Anderson, Haley J. McKeefer, Jordan Bird, Brandon Pentz, Britta R. M. Byman, Nicholas Jendzjowsky, Richard J. Wilson, Trevor A. Day, Caroline A. Rickards

Published in: European Journal of Applied Physiology

Abstract

With ascent to high altitude (HA), compensatory increases in cerebral blood flow and oxygen delivery must occur to preserve cerebral metabolism and consciousness. We hypothesized that this compensation in cerebral blood flow and oxygen delivery preserves tolerance to simulated hemorrhage (via lower body negative pressure, LBNP), such that tolerance is similar during sustained exposure to HA vs. low altitude (LA). Healthy humans (4F/4 M) participated in LBNP protocols to presyncope at LA (1130 m) and 5–7 days following ascent to HA (3800 m). Internal carotid artery (ICA) blood flow, cerebral delivery of oxygen (CDO₂) through the ICA, and cerebral tissue oxygen saturation (ScO₂) were determined. LBNP tolerance was similar between conditions (LA: 1276 ± 304 s vs. HA: 1208 ± 306 s; P = 0.58). Overall, ICA blood flow and CDO₂ were elevated at HA vs. LA (P ≤ 0.01) and decreased with LBNP under both conditions (P < 0.0001), but there was no effect of altitude on ScO₂ responses (P = 0.59). Thus, sustained exposure to hypobaric hypoxia did not negatively impact tolerance to simulated hemorrhage. These data demonstrate the robustness of compensatory physiological mechanisms that preserve human cerebral blood flow and oxygen delivery during sustained hypoxia, ensuring cerebral tissue metabolism and neuronal function is maintained.

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Title: Hemorrhage at high altitude: impact of sustained hypobaric hypoxia on cerebral blood flow, tissue oxygenation, and tolerance to simulated hemorrhage in humans
Authors: Alexander J. Rosenberg
Garen K. Anderson
Haley J. McKeefer
Jordan Bird
Brandon Pentz
Britta R. M. Byman
Nicholas Jendzjowsky
Richard J. Wilson
Trevor A. Day
Caroline A. Rickards
Publication date: 15-03-2024
Publisher: Springer Berlin Heidelberg
Published in: European Journal of Applied Physiology
Print ISSN: 1439-6319
Electronic ISSN: 1439-6327
DOI: https://doi.org/10.1007/s00421-024-05450-1

At a glance: The STEP trials

Springer Medicine

Hemorrhage at high altitude: impact of sustained hypobaric hypoxia on cerebral blood flow, tissue oxygenation, and tolerance to simulated hemorrhage in humans

Abstract

At a glance: The STEP trials

Springer Medicine

Abstract

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