Related Experiment Videos
Orthostatic blood pressure control before and after spaceflight, determined by time-domain baroreflex method
J Gisolf1, R V Immink, J J van Lieshout
1Department of Physiology, Rm. M01-215, Academic Medical Center, University of Amsterdam, PO Box 22700, 1100 DE Amsterdam, The Netherlands. j.gisolf@amc.uva.nl
Journal of Applied Physiology (Bethesda, Md. : 1985)
|January 15, 2005
Summary
Spaceflight alters baroreflex function, leading to orthostatic intolerance. Post-flight, cosmonauts showed impaired baroreflex sensitivity and abnormal responses to standing, indicating potential sympathetic nervous system changes.
Area of Science:
- Cardiovascular Physiology
- Space Medicine
- Autonomic Nervous System Function
Background:
- Orthostatic tachycardia and hypotension after spaceflight are linked to reduced plasma volume.
- Baroreflex sensitivity (BRS) plays a crucial role in maintaining cardiovascular stability during postural changes.
Purpose of the Study:
- To evaluate time- and frequency-domain baroreflex function in cosmonauts before and after spaceflight.
- To determine if reduced central blood volume mimics post-flight orthostatic responses.
Main Methods:
- Noninvasive finger arterial pressure measurement in supine and upright positions.
- Baroreflex sensitivity (BRS) assessment using spectral analysis and PRVXBRS during preflight and postflight orthostatic stress.
- Preflight venous occlusion to simulate reduced central blood volume.
Main Results:
- Two of five cosmonauts exhibited significant orthostatic intolerance post-flight.
- A decrease in low-frequency baroreflex gain was observed post-flight (P = 0.033).
- A significant shift towards higher values in the pulse interval-to-pressure lag (Tau) was noted post-flight (P < 0.001).
Conclusions:
- Cosmonauts can experience abnormal orthostatic responses days after returning from spaceflight.
- Post-flight orthostatic stress suggests an increased sympathetic response to standing.
- Preflight venous occlusion did not replicate the observed post-flight orthostatic responses.