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Effects of prolonged head-down bed rest on physiological responses to moderate hypoxiaTo determine the effects of hypoxia on physiological responses to simulated zero-gravity cardiopulmonary and fluid balance measurements were made in 6 subjects before and during 5-degree head-down bed rest (HDBR) over 8 d at 10,678 ft and a second time at this altitude as controls (CON). The V-dot(O2)(max) increased by 9 percent after CON, but fell 3 percent after HDBR. This reduction in work capacity during HDBR could be accounted for by inactivity. The heart rate response to a head-up tilt was greatly enhanced following HDBR, while mean blood pressure was lower. No significant negative impact of HDBR was noted on the ability to acclimatize to hypoxia in terms of pulmonary mechanics, gas exchange, circulatory or mental function measurements. No evidence of pulmonary interstitial edema or congestion was noted during HDBR at the lower PIO2 and blood rheology properties were not negatively altered. Symptoms of altitude illness were more prevalent, but not marked, during HDBR and arterial blood gases and oxygenation were not seriously effected by simulated microgravity. Declines in base excess with altitude were similar in both conditions. The study demonstrated a minimal effect of HDBR on the ability to adjust to this level of hypoxia.
Document ID
19930051497
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)
Greene, E. R.
(NASA Lyndon B. Johnson Space Center Houston, TX, United States)
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
93A35494
Funding Number(s)
CONTRACT_GRANT: NAG9-375
Distribution Limits
Public
Copyright
Other

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