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Acute hemodynamic responses to weightlessness in humans.
C M Lathers1, J B Charles, K F Elton
1Universities Space Research Association, Houston, Texas.
Journal of Clinical Pharmacology
|July 1, 1989
Summary
Understanding the cardiovascular system
Area of Science:
- Space physiology
- Cardiovascular research
- Human adaptation to spaceflight
Background:
- Prolonged weightlessness impacts astronaut health.
- Early cardiovascular effects of weightlessness are not well-documented.
- Understanding these effects is crucial for space pharmacology.
Purpose of the Study:
- To document acute hemodynamic responses to weightlessness.
- To investigate fluid shifts during transitions from acceleration to weightlessness.
- To compare responses across different body postures.
Main Methods:
- Utilized NASA's KC-135 aircraft for parabolic flights.
- Collected impedance cardiography data during parabolic maneuvers.
- Assessed hemodynamic responses in semi-supine, supine, sitting, and standing postures.
Main Results:
- Standing posture showed decreased heart rate and increased thoracic fluid.
- Semi-supine posture exhibited minimal headward fluid shift initially.
- Heart rate, stroke index, and cardiac index remained stable in semi-supine posture during weightlessness.
Conclusions:
- Initial weightlessness responses differ significantly by posture.
- The semi-supine posture may involve pre-launch fluid shifts.
- Early in-flight fluid shifts may differ from initial parabolic flight responses.