Pantalos GM, Sharp MK, Woodruff SJ, O'Leary DS, Gillars KJ.
ASGSB Bull. 1995 Oct; 9: 32.
Univ. of Utah, Salt Lake City, USA.
Measurement of cardiac stroke volume (SV) and central venous pressure (CVP) in Space Shuttle crew members during the SLS-1 and SLS-2 missions has resulted in the paradoxical observation of an increased SV in the presence of a reduced CVP compared to preflight values. The pressure change was documented to begin immediately upon entry into weightlessness. This team of investigators has proposed that the mechanism for this change is that the release of gravitational force on the massive chest wall structure initiates an integrated biomechanical interaction between the chest wall, lungs, heart, diaphragm and abdomen resulting in an increase in the cardiac transmural pressure via a reduction in the intrapleural pressure. The increase in cardiac transmural pressure promotes increased cardiac filling at a lower filling pressure. The objective of this investigation was to simulate this phenomenon with a life-size fluid circuit model of the cardiovascular system with resistance and compliance elements which create physiologic pressure and flow conditions. The model included a preload and afterload sensitive, compliant polymer sac that approximated the anatomy and pressure-volume relationship of the natural left ventricle. Ventricular contraction was simulated by delivering metered pulses of compressed air to the pressurization chamber surrounding the ventricular sac. The application of sub-atmospheric pressure in the ventricular pressurization chamber during diastole to simulate the proposed reduction in intrapleural pressure upon entry into weightlessness immediately resulted in a leftward shift of the ventricular function curve with no change in ventricular compliance. For example, the application of a 3 cm of H2O sub-atmospheric pressure during diastole resulted in the mean arterial pressure dropping 1 cm of H2O while the SV increased 10% as the ventricular function curve shifted to the left 3 cm of H2O. This simulated response is comparable to reported hemodynamic changes in-flight. Data with and without application of diastolic sub-atmospheric pressure during parabolic flight to examine the additional effects of fluid shifting will be presented.
Publication Types:
Keywords:
- Acclimatization
- Atmospheric Pressure
- Blood Pressure
- Central Venous Pressure
- Diastole
- Heart
- Heart Failure
- Heart Rate
- Heart Ventricles
- Pressure
- Stroke Volume
- Ventricular Function
- Ventricular Function, Left
- Weightlessness
- Weightlessness Simulation
- NASA Discipline Cardiopulmonary
- NASA Discipline Number 70-30
- NASA Program Data Analysis
- Non-NASA Center
Other ID:
UI: 102222749
From Meeting Abstracts