NTRS - NASA Technical Reports Server

Back to Results
The effect of blood volume loss on cardiovascular response to lower body negative pressure using a mathematical modelDifferent mathematical models of varying complexity have been proposed in recent years to study the cardiovascular (CV) system. However, only a few of them specifically address the response to lower body negative pressure (LBNP), a stress that can be applied in weightlessness to predict changes in orthostatic tolerance. Also, the simulated results produced by these models agree only partially with experimental observations. In contrast, the model proposed by Melchior et al., and modified by Karam et al. is a simple representation of the CV system capable of accurately reproducing observed LBNP responses up to presyncopal levels. There are significant changes in LBNP response due to a loss of blood volume and other alterations that occur in weightlessness and related one-g conditions such as bedrest. A few days of bedrest can cause up to 15% blood volume loss (BVL), with consequent decreases in both stroke volume and cardiac output, and increases in heart rate, mean arterial pressure, and total peripheral resistance. These changes are more pronounced at higher levels of LBNP. This paper presents the results of a simulation study using our CV model to examine the effect of BVL on LBNP response.
Document ID
Document Type
Reprint (Version printed in journal)
Karam, E. H. (NASA Johnson Space Center Houston TX United States)
Srinivasan, R. S.
Charles, J. B.
Fortney, S. M.
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
NASA Discipline Number 70-30
NASA Program Data Analysis
NASA Program Space Physiology and Countermeasures
NASA Discipline Number 14-10
NASA Discipline Cardiopulmonary