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Head-down bed rest impairs vagal baroreflex responses and provokes orthostatic hypotensionThe hypothesis that baroreflex malfunction contributes to orthostatic hypotension in microgravity was tested by studying vagally mediated carotid baroreceptor-cardiac reflexes in healthy human subjects before, during, and after 30 days of 6-deg head-down bed rest. The baroreflex response relationships were provoked with ramped neck pressure-suction sequences comprising pressure elevations to 40 mm Hg followed by serial R-wave-triggered 15-mm Hg reductions to -65 mm0 Hg; each R-R interval was plotted as a function of systolic pressure minus the neck chamber pressure applied during the interval. It is shown that head-down bed rest led to an impairment of vagal baroreflex function and that it was associated with an impairment of hemodynamic adjustments to standing, indicating that baroreflex impairment may contribute to orthostatic hypotension observed in spacecrews after a flight.
Document ID
19900046661
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Convertino, Victor A.
(NASA John F. Kennedy Space Center Cocoa Beach, FL, United States)
Doerr, Donald F.
(NASA John F. Kennedy Space Center Cocoa Beach, FL, United States)
Eckberg, Dwain L.
(NASA John F. Kennedy Space Center Cocoa Beach, FL, United States)
Fritsch, Janice M.
(NASA John F. Kennedy Space Center Cocoa Beach, FL, United States)
Vernikos-Danellis, Joan
(NASA Kennedy Space Center Cocoa Beach, FL; NASA, Ames Research Center, Moffett Field, CA; USVA, Medical Center; Virginia, Medi, United States)
Date Acquired
August 14, 2013
Publication Date
April 1, 1990
Publication Information
Publication: Journal of Applied Physiology
Volume: 68
ISSN: 0161-7567
Subject Category
Aerospace Medicine
Accession Number
90A33716
Funding Number(s)
CONTRACT_GRANT: NAG2-408
CONTRACT_GRANT: NAS10-10285
CONTRACT_GRANT: NIH-HL-22296
Distribution Limits
Public
Copyright
Other

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