Effects of whole body heating on dynamic baroreflex regulation of heart rate in humans
Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas 75231; and Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235 The purpose of this project was to identify whether dynamic baroreflex regulation of heart rate...
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Published in | American journal of physiology. Heart and circulatory physiology Vol. 279; no. 5; pp. H2486 - H2492 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Legacy CDMS
01.11.2000
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Subjects | |
Online Access | Get full text |
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Summary: | Institute for Exercise and Environmental Medicine, Presbyterian
Hospital of Dallas, Dallas 75231; and Department of Internal
Medicine, University of Texas Southwestern Medical Center, Dallas,
Texas 75235
The 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.
baroreceptor; orthostatic intolerance; transfer function analysis; spectral analysis |
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Bibliography: | CDMS Legacy CDMS ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0363-6135 1522-1539 |
DOI: | 10.1152/ajpheart.2000.279.5.h2486 |