Steady-state Cardiovascular Regulation In A Simple Model With Adjustable Intrathoracic Pressure And Abdominal Compression
- Paper number
IAC-07-A1.3.-A1.4.04
- Author
Dr. Ronald J. White, USRA, United States
- Year
2007
- Abstract
A small new compartmental model of the cardiovascular system will be presented that demonstrates some of the complexities that result from the interplay among some of the body’s many components. Although this small, five-compartment model with parallel visceral and peripheral flows and adjustable intrathoracic and abdominal pressures contains 25 adjustable physiological parameters, it will be shown that the steady state is completely determined by a two-parameter equation of the form Z = µ + λ log[(1-Z)/Z] where µ and λ are new dimensionless parameters and where Z is proportional to the cardiac output. Sensitivity analysis and numerical examples will be used to illustrate the interplay among the model’s parameters and the functioning of the model in various states. In particular, it will be shown how relaxation of abdominal compression by only 2 mm Hg and reduction of intrathoracic pressure by a like amount leads to a condition much like the rapid, initial response to weightlessness: a headward fluid shift, a reduction of central venous pressure, no change in arterial pressure and a very small change in cardiac output. The major conclusions of these modeling studies are the hypotheses that abdominal compression can play a major role in macroscopic cardiovascular events of interest during and after space flight and that relaxation of the abdominal muscles in addition to the previously proposed reduction in intrathoracic pressure may play a role in the initial body’s reaction to weightlessness.
- Abstract document
- Manuscript document
IAC-07-A1.3.-A1.4.04.pdf (🔒 authorized access only).
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