Document Detail


Leg vascular responsiveness during acute orthostasis following simulated weightlessness.
MedLine Citation:
PMID:  3355464     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Ten men (35-49 years old) underwent lower body negative pressure (LBNP) exposures before and after 10 d of continuous 6 degrees head-down bedrest in order to predict the effect of weightlessness on the responsiveness of leg vasculature to an orthostatic stress. Heart rate (HR), mean arterial blood pressure (MAP), and impedance rheographic indices of arterial pulse volume (APV) of the legs were measured during rest and at 1 min of -30 mm Hg LBNP. Bedrest-induced deconditioning was manifested by decreases (p less than 0.05) in plasma volume (17%), peak oxygen uptake (16%), and LBNP tolerance (17%). Resting HR was unchanged after bedrest, but HR was higher (p less than 0.05) at 1 min of -30 mm Hg LBNP after, compared with before, bedrest. Responses of MAP to -30 mm Hg LBNP were not altered by bedrest. Resting APV was decreased (p less than 0.05) by simulated weightlessness. However, APV was reduced (p less than 0.05) from rest to 1 min -30 mm Hg LBNP by the same relative magnitude before and after bedrest (-21.4 +/- 3.4% and -20.5 +/- 2.7%, respectively). We conclude that peripheral arterial vasoconstriction, as indicated by reductions in APV during LBNP, was not affected by bedrest. These results suggest that there was no apparent alteration in responsiveness of the leg vasculature following simulated weightlessness. Therefore, it appears unlikely that control mechanisms of peripheral resistance contribute significantly to reduced orthostatic tolerance following spaceflight.
Authors:
C A Blamick; D J Goldwater; V A Convertino
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Aviation, space, and environmental medicine     Volume:  59     ISSN:  0095-6562     ISO Abbreviation:  Aviat Space Environ Med     Publication Date:  1988 Jan 
Date Detail:
Created Date:  1988-05-06     Completed Date:  1988-05-06     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7501714     Medline TA:  Aviat Space Environ Med     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  40-3     Citation Subset:  IM; S    
Affiliation:
Bionetics Corp., Biomedical Operations and Research Office, Kennedy Space Center, FL 32899.
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MeSH Terms
Descriptor/Qualifier:
Adaptation, Physiological
Adult
Blood Vessels / physiology*
Humans
Leg / blood supply*
Lower Body Negative Pressure
Male
Middle Aged
Muscle, Smooth, Vascular / physiology
Posture*
Pulse
Weightlessness*

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


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