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Influence of gravity on cardiac performance
G M Pantalos1, M K Sharp, S J Woodruff
1Artificial Heart Research Laboratory, University of Utah, Salt Lake City 84112, USA.
Annals of Biomedical Engineering
|December 10, 1998
Summary
Lack of hydrostatic pressure significantly reduces cardiac output and stroke volume by 20-50%. This finding in a hydraulic model explains astronaut cardiac changes in weightlessness.
Area of Science:
- Cardiovascular Physiology
- Space Medicine
- Biomedical Engineering
Background:
- Cardiac performance in astronauts is altered during spaceflight.
- Understanding the physiological mechanisms behind these changes is crucial for astronaut health.
- Previous studies suggest microgravity impacts cardiovascular function.
Purpose of the Study:
- To investigate the effect of hydrostatic pressure absence on cardiac function.
- To determine if a hydraulic model can replicate human cardiovascular responses in weightlessness.
- To identify the role of hydrostatic pressure in astronaut cardiac adaptation.
Main Methods:
- Ground-based experiments using a hydraulic simulator of the human systemic circulation.
- Parabolic flight tests aboard NASA KC-135 aircraft.
- Analysis of stroke volume (SV) and cardiac output (CO) at various atrial pressures (AP).
Main Results:
- A 20%-50% decrease in stroke volume was observed due to the lack of hydrostatic pressure.
- Cardiac output and stroke volume dropped, shifting the cardiac function curve rightward.
- Results align with echocardiographic data from space shuttle missions showing a 15% SV decrease.
Conclusions:
- The absence of hydrostatic pressure is a key factor in reduced cardiac performance in weightlessness.
- A hydraulic model effectively simulates human cardiovascular responses to simulated weightlessness.
- Physical effects of hydrostatic pressure loss significantly impact astronaut cardiac function.