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Cardiovascular dynamics associated with tolerance to lower body negative pressureThe purpose of this investigation was to identify cardiovascular responses associated with tolerance to lower body negative pressure (LBNP). Eighteen men, ages 29-51 years, were categorized as high (HT) or low (LT) LBNP-tolerant based on a graded presyncopal-limited LBNP exposure criterion of -60 mm Hg relative to ambient pressure. Groups were matched for physical characteristics and pre-LBNP cardiovascular measurements, with the exceptions of greater (p less than 0.05) end-diastolic volume and cardiac output in the HT group. During peak LBNP, cardiac output was similar in both groups, although the HT group displayed a greater heart rate (p less than 0.05). In both groups, venous return appeared to limit cardiac output resulting in decreased arterial pressure. Tolerance to LBNP did not appear solely dependent on the absolute amount of blood pooled in the legs since the HT group demonstrated a greater (p less than 0.05) peak LBNP-induced increase in midthigh-leg volume. Greater tolerance to LBNP was associated with a larger pre-LBNP cardiac output reserve and higher compensatory increases in heart rate and peripheral resistance.
Document ID
19860051572
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Sather, T. M.
(NASA Ames Research Center Moffett Field, CA, United States)
Goldwater, D. J.
(NASA Ames Research Center Moffett Field, CA, United States)
Montgomery, L. D.
(NASA Ames Research Center Moffett Field, CA; Arizona, University, Tucson, United States)
Convertino, V. A.
(Bionetics Corp. Cocoa Beach, FL, United States)
Date Acquired
August 12, 2013
Publication Date
May 1, 1986
Publication Information
Publication: Aviation, Space, and Environmental Medicine
Volume: 57
ISSN: 0095-6562
Subject Category
Aerospace Medicine
Accession Number
86A36310
Distribution Limits
Public
Copyright
Other

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