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Computer simulation of the effect of dDAVP with saline loading on fluid balance after 24-hour head-down tiltFluid loading (FL) before Shuttle reentry is a countermeasure currently in use by NASA to improve the orthostatic tolerance of astronauts during reentry and postflight. The fluid load consists of water and salt tablets equivalent to 32 oz (946 ml) of isotonic saline. However, the effectiveness of this countermeasure has been observed to decrease with the duration of spaceflight. The countermeasure's effectiveness may be improved by enhancing fluid retention using analogs of vasopressin such as lypressin (LVP) and desmopressin (dDAVP). In a computer simulation study reported previously, we attempted to assess the improvement in fluid retention obtained by the use of LVP administered before FL. The present study is concerned with the use of dDAVP. In a recent 24-hour, 6 degree head-down tilt (HDT) study involving seven men, dDAVP was found to improve orthostatic tolerance as assessed by both lower body negative pressure (LBNP) and stand tests. The treatment restored Luft's cumulative stress index (cumulative product of magnitude and duration of LBNP) to nearly pre-bedrest level. The heart rate was lower and stroke volume was marginally higher at the same LBNP levels with administration of dDAVP compared to placebo. Lower heart rates were also observed with dDAVP during stand test, despite the lower level of cardiovascular stress. These improvements were seen with only a small but significant increase in plasma volume of approximately 3 percent. This paper presents a computer simulation analysis of some of the results of this HDT study.
Document ID
20040089967
Document Type
Reprint (Version printed in journal)
Authors
Srinivasan, R. S. (KRUG Life Sciences Houston, TX 77058, United States)
Simanonok, K. E.
Charles, J. B.
Date Acquired
August 21, 2013
Publication Date
May 1, 1994
Publication Information
Publication: Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology
Volume: 1
Issue: 1
ISSN: 1077-9248
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Cardiopulmonary
NASA Discipline Number 70-30
NASA Discipline Number 14-10
Non-NASA Center
NASA Program Data Analysis
NASA Program Space Physiology and Countermeasures
NASA Center JSC