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Lookup NU author(s): Dr Adrian Mellor,
Dr David Woods
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
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.
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
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
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