Document Detail

Effects of whole body heating on dynamic baroreflex regulation of heart rate in humans.
MedLine Citation:
PMID:  11045986     Owner:  NLM     Status:  MEDLINE    
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.
C G Crandall; R Zhang; B D Levine
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  279     ISSN:  0363-6135     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2000 Nov 
Date Detail:
Created Date:  2000-11-17     Completed Date:  2000-12-28     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  H2486-92     Citation Subset:  IM; S    
Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas 75231, USA.
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MeSH Terms
Baroreflex / physiology*
Blood Flow Velocity / physiology
Blood Pressure / physiology
Body Temperature / physiology*
Heart Rate / physiology*
Hot Temperature*
Skin / blood supply
Skin Temperature / physiology
Grant Support
C G Crandall / Presbyterian Hosp, Dallas, TX

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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