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Acute hemodynamic responses to weightlessness in humansAs NASA designs space flights requiring prolonged periods of weightlessness for a broader segment of the population, it will be important to know the acute and sustained effects of weightlessness on the cardiovascular system since this information will contribute to understanding of the clinical pharmacology of drugs administered in space. Due to operational constraints on space flights, earliest effects of weightlessness have not been documented. We examined hemodynamic responses of humans to transitions from acceleration to weightlessness during parabolic flight on NASA's KC-135 aircraft. Impedance cardiography data were collected over four sets of 8-10 parabolas, with a brief rest period between sets. Each parabola included a period of 1.8 Gz, then approximately 20 seconds of weightlessness, and finally a period of 1.6 Gz; the cycle repeated almost immediately for the remainder of the set. Subjects were semi-supine (Shuttle launch posture) for the first set, then randomly supine, sitting and standing for each subsequent set. Transition to weightlessness while standing produced decreased heart rate, increased thoracic fluid content, and increased stroke index. Surprisingly, the onset of weightlessness in the semi-supine posture produced little evidence of a headward fluid shift. Heart rate, stroke index, and cardiac index are virtually unchanged after 20 seconds of weightlessness, and thoracic fluid content is slightly decreased. Semi-supine responses run counter to Shuttle crewmember reports of noticeable fluid shift after minutes to hours in orbit. Apparently, the headward fluid shift commences in the semi-supine posture before launch. is augmented by launch acceleration, but briefly interrupted immediately in orbit, then resumes and is completed over the next hours.
Document ID
20050000903
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Lathers, C. M.
(Universities Space Research Association Houston, Texas)
Charles, J. B.
Elton, K. F.
Holt, T. A.
Mukai, C.
Bennett, B. S.
Bungo, M. W.
Date Acquired
August 22, 2013
Publication Date
July 1, 1989
Publication Information
Publication: Journal of clinical pharmacology
Volume: 29
Issue: 7
ISSN: 0091-2700
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other
Keywords
short duration
Randomized Controlled Trial
manned
NASA Center JSC
Parabolic Flight
Flight Experiment
Clinical Trial
NASA Discipline Cardiopulmonary

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