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A Four-Way Comparison of Cardiac Function with Normobaric Normoxia, Normobaric Hypoxia, Hypobaric Hypoxia and Genuine High Altitude

Lookup NU author(s): Dr Adrian Mellor, Dr David Woods

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

BackgroundThere has been considerable debate as to whether different modalities of simulated hypoxia induce similar cardiac responses.Materials and MethodsThis was a prospective observational study of 14 healthy subjects aged 22-35 years. Echocardiography was performed at rest and at 15 and 120 minutes following two hours exercise under normobaric normoxia (NN) and under similar PiO(2) following genuine high altitude (GHA) at 3,375m, normobaric hypoxia (NH) and hypobaric hypoxia (HH) to simulate the equivalent hypoxic stimulus to GHA.ResultsAll 14 subjects completed the experiment at GHA, 11 at NN, 12 under NH, and 6 under HH. The four groups were similar in age, sex and baseline demographics. At baseline rest right ventricular (RV) systolic pressure (RVSP, p = 0.0002), pulmonary vascular resistance (p = 0.0002) and acute mountain sickness (AMS) scores were higher and the SpO(2) lower (p<0.0001) among all three hypoxic groups (GHA, NH and HH) compared with NN. At both 15 minutes and 120 minutes post exercise, AMS scores, Cardiac output, septal S', lateral S', tricuspid S' and A' velocities and RVSP were higher and SpO(2) lower with all forms of hypoxia compared with NN. On post-test analysis, among the three hypoxia groups, SpO(2) was lower at baseline and 15 minutes post exercise with GHA (89.3 +/- 3.4% and 89.3 +/- 2.2%) and HH (89.0 +/- 3.1 and (89.8 +/- 5.0) compared with NH (92.9 +/- 1.7 and 93.6 +/- 2.5%). The RV Myocardial Performance (Tei) Index and RVSP were significantly higher with HH than NH at 15 and 120 minutes post exercise respectively and tricuspid A' was higher with GHA compared with NH at 15 minutes post exercise.ConclusionsGHA, NH and HH produce similar cardiac adaptations over short duration rest despite lower SpO(2) levels with GHA and HH compared with NH. Notable differences emerge following exercise in SpO(2), RVSP and RV cardiac function.

Publication metadata

Author(s): Boos CJ, O'Hara JP, Mellor A, Hodkinson PD, Tsakirides C, Reeve N, Gallagher L, Green NDC, Woods DR

Publication type: Article

Publication status: Published

Journal: PLoS ONE

Year: 2016

Volume: 11

Issue: 4

Online publication date: 21/04/2016

Acceptance date: 21/03/2016

Date deposited: 25/07/2016

ISSN (electronic): 1932-6203

Publisher: Public Library of Science

URL: http://dx.doi.org/10.1371/journal.pone.0152868

DOI: 10.1371/journal.pone.0152868

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