| Heart rate and blood pressure responses to +Gz following varied-duration -Gz. | |
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MedLine Citation:
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PMID: 10685587 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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BACKGROUND: The push-pull effect has been defined previously as decreased +Gz tolerance caused by previous baseline zero or -Gz exposure. Earlier work indicates that the delay in BP (BP) recovery during +Gz is a function of time at -G7, and is due to the lengthened time-course of sympathetically mediated peripheral vasoconstriction. HYPOTHESIS: The purpose of this study was to retrospectively determine whether heart rate (HR) varies with BP as duration at preceding -Gz increased. METHODS: Continuous ECG R-R interval data from 15 s of +2.25Gz after preceding 2, 5, 10, or 15 s at 2Gz obtained from previous experiments were analyzed and compared with the previously reported BP data. Repeated measures ANOVA and regression analyses were used to compare +2.25Gz HR responses after the four -Gz conditions and one control +2.25Gz condition. RESULTS: An initial rapid rise in HR was observed for all conditions with a consistent steady-state plateau achieved after the first 7 s of +2.25Gz. However, there were significant differences in mean HR attained during the +2.25Gz plateau for preceding 15 s -2.0 Gz vs. the control, 2, 5, and 10s -Gz conditions (109+/-1.1 vs. 102+/-1.8, 100+/-2.0, 97+/-1.1 and 101+/-1.1, bpm, respectively; p<0.05). CONCLUSIONS: HR, unlike BP, increases briskly across all preceding -Gz time conditions, adapting within the initial baroreflex-compensatory time frame typically expected for +Gz exposures. These results suggest there may be a threshold effect for HR response. Consequently, vasoconstrictor response is a critical adaptive mechanism during +Gz when preceded by long (>10 s) -Gz exposures. |
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Authors:
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L S Goodman; R D Banks; J D Grissett; P L Saunders |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Aviation, space, and environmental medicine Volume: 71 ISSN: 0095-6562 ISO Abbreviation: Aviat Space Environ Med Publication Date: 2000 Feb |
Date Detail:
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Created Date: 2000-03-02 Completed Date: 2000-03-02 Revised Date: 2004-11-17 |
Medline Journal Info:
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Nlm Unique ID: 7501714 Medline TA: Aviat Space Environ Med Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 137-41 Citation Subset: IM; S |
Affiliation:
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Defence and Civil Institute of Environmental Medicine, Aerospace Life Support Section, Toronto, Ontario, Canada. len.goodman@dciem.dnd.ca |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adaptation, Physiological
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physiology* Aerospace Medicine* Analysis of Variance Blood Pressure / physiology* Bradycardia / diagnosis, etiology*, physiopathology Electrocardiography Heart Rate / physiology* Homeostasis Humans Hypergravity / adverse effects* Hypogravity / adverse effects* Monitoring, Physiologic Regression Analysis Retrospective Studies Time Factors Vasoconstriction / physiology* |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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