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Body fluid alterations during head-down bed rest in men at moderate altitudeTo determine the effects of hypoxia on fluid balance responses to simulated zero-gravity, measurements were made in six subjects before and during -5 deg continuous head-down bed rest (HDBR) over 8 d at 10,678 ft. The same subjects were studied again at this altitude without HDBR as a control (CON) using a cross-over design. During this time, they maintained normal upright day-time activities, sleeping in the horizontal position at night. Fluid balance changes during HDBR in hypoxia were more pronounced than similar measurements previously reported from HDBR studies at sea level. Plasma volume loss was slightly greater and the diuresis and natriuresis were doubled in magnitude as compared to previous studies in normoxia and sustained for 4 d during hypoxia. These changes were associated with an immediate but transient rise in plasma atrial natriuretic peptide (ANP) to day 4 of 140 percent in HDBR and 41 percent in CON (p less than 0.005), followed by a decline towards baseline. Differences were less striking between HDBR and CON for plasma antidiuretic hormone and aldosterone, which were transiently reduced by HDBR. Plasma catecholamines showed a similar pattern to ANP in both HDBR and CON, suggesting that elevated ANP and catecholamines together accounted for the enhanced fluid shifts with HDBR during hypoxia.
Document ID
19930051496
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Loeppky, J. A.
(NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Roach, R. C.
(Lovelace Medical Foundation Albuquerque, NM, United States)
Selland, M. A.
(Colorado Univ. Denver, United States)
Scotto, P.
(Napoli, Univ. Naples, Italy)
Luft, F. C.
(Erlangen-Nuernberg Univ. Erlangen, Germany)
Luft, U. C.
(Lovelace Medical Foundation Albuquerque, NM, United States)
Date Acquired
August 16, 2013
Publication Date
April 1, 1993
Publication Information
Publication: Aviation, Space, and Environmental Medicine
Volume: 64
Issue: 4
ISSN: 0095-6562
Subject Category
Aerospace Medicine
Accession Number
93A35493
Funding Number(s)
CONTRACT_GRANT: NAG9-375
Distribution Limits
Public
Copyright
Other

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