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1 Harvard University-Massachusetts Institute of Technology Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts; 2 Kumoh National University of Technology, Kumi, Kyungbuk, 730-701, Republic of Korea; 3 Division of Bioengineering and Environmental Health, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
The
objective of this study is to develop a model of the
cardiovascular system capable of simulating the short-term (
5 min) transient and steady-state hemodynamic responses to head-up tilt and
lower body negative pressure. The model consists of a closed-loop lumped-parameter representation of the circulation connected to set-point models of the arterial and cardiopulmonary baroreflexes. Model parameters are largely based on literature values. Model verification was performed by comparing the simulation output under
baseline conditions and at different levels of orthostatic stress to
sets of population-averaged hemodynamic data reported in the
literature. On the basis of experimental evidence, we adjusted some
model parameters to simulate experimental data. Orthostatic stress
simulations are not statistically different from experimental data
(two-sided test of significance with Bonferroni adjustment for multiple
comparisons). Transient response characteristics of heart rate to tilt
also compare well with reported data. A case study is presented on how
the model is intended to be used in the future to investigate the
effects of postspaceflight orthostatic intolerance.
mathematical model; simulation; head-up tilt; lower body negative pressure; orthostatic intolerance
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