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Cardiopulmonary function during 10 days of head-down tilt bedrest
H Schulz1, A Hillebrecht, J M Karemaker
1Max-Planck-Institute for Experimental Medicine, Göttingen, Germany.
Acta Physiologica Scandinavica. Supplementum
|January 1, 1992
Summary
Simulated weightlessness via head-down tilt bedrest significantly impacts cardiovascular function and gas exchange. These changes, including reduced pulmonary blood flow and diffusing capacity, may explain post-flight intolerance.
Area of Science:
- Physiology
- Aerospace Medicine
Background:
- Simulated weightlessness is crucial for understanding physiological adaptations to spaceflight.
- Head-down tilt bedrest (HDT) is a common model for simulating weightlessness effects.
Purpose of the Study:
- To investigate the pulmonary and cardiovascular responses to simulated weightlessness using 6° HDT.
- To assess short-term and prolonged effects of HDT on physiological parameters.
Main Methods:
- Six healthy male volunteers underwent 6° HDT bedrest for 10 days.
- Pulmonary function (diffusing capacity, lung volumes) was measured using inert gas rebreathing.
- Cardiovascular parameters (heart rate, blood pressure) were monitored non-invasively.
Main Results:
- Short-term HDT caused increased pulmonary blood flow and decreased blood pressure and heart rate.
- Functional residual capacity significantly decreased, while lung tissue volume showed no significant change.
- Prolonged HDT led to a gradual decline in diffusing capacity and pulmonary blood flow, persisting into recovery.
Conclusions:
- Simulated weightlessness induces significant cardiovascular alterations and mild gas exchange impairments at rest.
- These physiological changes may contribute to orthostatic and exercise intolerance experienced after spaceflight.