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Effects of whole body heating on dynamic baroreflex regulation of heart rate in humansThe purpose of this project was to identify whether dynamic baroreflex regulation of heart rate (HR) is altered during whole body heating. In 14 subjects, dynamic baroreflex regulation of HR was assessed using transfer function analysis. In normothermic and heat-stressed conditions, each subject breathed at a fixed rate (0. 25 Hz) while beat-by-beat HR and systolic blood pressure (SBP) were obtained. Whole body heating significantly increased sublingual temperature, HR, and forearm skin blood flow. Spectral analysis of HR and SBP revealed that the heat stress significantly reduced HR and SBP variability within the high-frequency range (0.2-0.3 Hz), reduced SBP variability within the low-frequency range (0.03-0.15 Hz), and increased the ratio of low- to high-frequency HR variability (all P < 0.01). Transfer function gain analysis showed that the heat stress reduced dynamic baroreflex regulation of HR within the high-frequency range (from 1.04 +/- 0.06 to 0.54 +/- 0.6 beats. min(-1). mmHg(-1); P < 0.001) without significantly affecting the gain in the low-frequency range (P = 0.63). These data suggest that whole body heating reduced high-frequency dynamic baroreflex regulation of HR associated with spontaneous changes in blood pressure. Reduced vagal baroreflex regulation of HR may contribute to reduced orthostatic tolerance known to occur in humans during heat stress.
Document ID
20040112704
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Crandall, C. G.
(Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas Dallas 75231, United States)
Zhang, R.
Levine, B. D.
Date Acquired
August 21, 2013
Publication Date
November 1, 2000
Publication Information
Publication: American journal of physiology. Heart and circulatory physiology
Volume: 279
Issue: 5
ISSN: 0363-6135
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: HL-61388
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
Clinical Trial
NASA Discipline Cardiopulmonary

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