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Reflex cardiovascular responses after 36 hr of hypoxia
Journal article   Peer reviewed

Reflex cardiovascular responses after 36 hr of hypoxia

Donald D Heistad, Robert C Wheeler and Vincent S Aoki
The American journal of physiology, Vol.220(6), pp.1673-1676
06/1971
DOI: 10.1152/ajplegacy.1971.220.6.1673
PMID: 5087816

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Abstract

We have observed that acute hypoxia decreases vasoconstrictor responses in man. The purpose of this study n-as to determine whether reflex vasoconstriction in man remains depressed during prolonged hypoxia or whether adaptation occurs. The response of forearm resistance vessels to lower body negative pressure was compared while breathing air and 12 yO oxygen during two sessions: a control session and immediately after 36 hr in a hypobaric chamber at a simulated altitude of i4,ooo ft ( e q uivalent to breathing 12 y0 oxygen). Forearm blood flow was measured with a plethysmograph and arterial pressure by auscultation. In the control session the forearm vasoconstrictor response to lower body negative pressure was less while breathing 12 $6 oxygen than while breathing air. This reduction in vasoconstrictor response continued after 36 hr of hypoxia, and vascular responses were abruptly restored by breathing air. The results indicate that decreased vascular responsiveness was still apparent after 36 hr of hypoxia, suggesting that adaptation of vascular reflexes has not occurred. Measurement of the response of heart rate to lower body negative pressure also suggested interference with cardiac reflexes during both acute and prolonged hypoxia.
 Adaptation, Physiological Reflex Heart Rate Vascular Resistance Constriction Humans Male Regional Blood Flow Cardiovascular System - physiopathology Vasomotor System - physiopathology Forearm - blood supply Adult Hypoxia - physiopathology

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