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Acute hypoxemia and vascular function in healthy humans.

Lewis, NCS and Bain, AR and Wildfong, KW and Green, DJ and Ainslie, PN (2017) Acute hypoxemia and vascular function in healthy humans. Experimental Physiology. ISSN 1469-445X

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Abstract

Endothelium-dependent flow mediated dilation (FMD) and endothelium-independent dilation (GTN) are impaired at high altitude (5050 m), and FMD is impaired following acute exposure (<60-minutes) to normobaric hypoxia equivalent to ∼5050 m (∼FI O2  = 0.11). Whether glyceryl trinitrate (GTN)-induced dilation is impaired acutely, and whether FMD is impaired during milder hypoxia is unknown. Therefore, we assessed brachial FMD at baseline and following 30-minutes of mild (74 ± 2 mmHg PET O₂) and moderate (50 ± 3 mmHg PET O₂) normobaric hypoxia (n = 12) or normoxia (time-control trial; n = 10). We also assessed GTN-dilaiton following the hypoxic FMD tests and in normoxia on a separate control day (n = 8). Compared to normoxic baseline, reduction during mild and moderate hypoxic exposure were evident in FMD (mild vs moderate: -1.2 ± 1.1% vs. -3.1 ± 1.7%; P = 0.01) and GTN-dilation (-2.1 ± 1.0 vs. -4.2 ± 2.0; P = 0.01); the decline in FMD and GTN-dilation were greater during moderate hypoxia (P < 0.01). When allometrically corrected for baseline diameter and FMD shear rate under the curve (SRAUC ), relative FMD was attenuated in both conditions (mild vs moderate: 0.6 ± 0.9% vs. 0.8 ± 0.7%; P ≤ 0.01). Following 30-minutes of normoxic time-control, FMD was reduced (-0.6 ± 0.3%; P = 0.02). In summary, there was a graded impairment in FMD during mild and moderate hypoxic exposure, which appears to be influenced by shear patterns and incremental declines in smooth muscle vasodilator capacity (impaired GTN-dilation). Our findings from the normoxic controls study, suggest the decline in FMD in acute hypoxia also appears to be influenced by 30-minutes of supine rest/inactivity. This article is protected by copyright. All rights reserved.

Item Type: Article
Additional Information: This is the accepted version of the following article: Lewis, N. C. S., Bain, A. R., Wildfong, K. W., Green, D. J. and Ainslie, P. N. (), Acute hypoxemia and vascular function in healthy humans. Exp Physiol. Accepted Author Manuscript. doi:10.1113/EP086532, which has been published in final form at http://dx.doi.org/10.1113/EP086532
Uncontrolled Keywords: 0606 Physiology, 1116 Medical Physiology, 1106 Human Movement And Sports Science
Subjects: R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions: Sport & Exercise Sciences
Publisher: Wiley
Related URLs:
Date Deposited: 27 Sep 2017 11:16
Last Modified: 27 Sep 2017 11:16
DOI or Identification number: 10.1113/EP086532
URI: http://researchonline.ljmu.ac.uk/id/eprint/7223

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