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Cardiovascular function in space flightChanges in orthostatic heart rate have been noted universally in Soviet and U.S. crewmembers post space flight. The magnitude of these changes appears to be influenced by mission duration, with increasing orthostatic intolerance for the first 7-10 days of flight and then a partial recovery in the orthostatic heart rate response. Fluid loading has been used as a countermeasure to this postflight orthostatic intolerance. Previous reports have documented the effectiveness of this technique, but it has also been noted that the effectiveness of volume expansion diminishes as flight duration exceeds one week. The response of carotid baroreceptor function was investigated utilizing a commercially available neck collar which could apply positive and negative pressure to effect receptor stimulation. Bedrest studies had validated the usefulness and validity of the device. In these studies it was shown that carotid baroreceptor function curves demonstrated less responsiveness to orthostatic stimulation than control individuals. Twelve Space Shuttle crewmembers were examined pre- and postflight from flights lasting from 4-5 days. Plots of baroreceptor function were constructed and plotted as change in R-R interval vs. carotid distending pressure (an orthostatic stimulus). Typical sigmoidal curves were obtained. Postflight the resting heart rate was higher (smaller R-R interval) and the range of R-R value and the slope of the carotid sigmoidal response were both depressed. These changes were not significant immediately postflight (L + O), but did become significant by the second day postflight (L + 2), and remained suppressed for several days thereafter. It is hypothesized that the early adaptation to space flight involves a central fluid shift during the initial days of flight, but subsequent alterations in neural controlling mechanisms (such as carotid baroreceptor function) contribute to orthostatic intolerance.
Document ID
20040089516
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Nicogossian, A. E.
(NASA Headquarters Washington, DC United States)
Charles, J. B.
Bungo, M. W.
Leach-Huntoon, C. S.
Nicgossian, A. E.
Date Acquired
August 21, 2013
Publication Date
January 1, 1991
Publication Information
Publication: Acta astronautica
Volume: 24
ISSN: 0094-5765
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other
Keywords
Review
NASA Center JSC
short duration
NASA Discipline Number 00-00
NASA Discipline Cardiopulmonary
NASA Center HQS
NASA Discipline Number 14-10
Flight Experiment
Review, Tutorial
manned
STS Shuttle Project
NASA Program Flight
NASA Program Space Physiology and Countermeasures

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