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Bursting into space: alterations of sympathetic control by space travelAIM: Astronauts return to Earth with reduced red cell masses and hypovolaemia. Not surprisingly, when they stand, their heart rates may speed inordinately, their blood pressures may fall, and some may experience frank syncope. We studied autonomic function in six male astronauts (average +/- SEM age: 40 +/- 2 years) before, during, and after the 16-day Neurolab space shuttle mission. METHOD: We recorded electrocardiograms, finger photoplethysmographic arterial pressures, respiration, peroneal nerve muscle sympathetic activity, plasma noradrenaline and noradrenaline kinetics, and cardiac output, and we calculated stroke volume and total peripheral resistance. We perturbed autonomic function before and during spaceflight with graded Valsalva manoeuvres and lower body suction, and before and after the mission with passive upright tilt. RESULTS: In-flight baseline sympathetic nerve activity was increased above pre-flight levels (by 10-33%) in three subjects, in whom noradrenaline spillover and clearance also were increased. Valsalva straining provoked greater reductions of arterial pressure, and proportionally greater sympathetic responses in space than on Earth. Lower body suction elicited greater increases of sympathetic nerve activity, plasma noradrenaline, and noradrenaline spillover in space than on Earth. After the Neurolab mission, left ventricular stroke volume was lower and heart rate was higher during tilt, than before spaceflight. No astronaut experienced orthostatic hypotension or pre-syncope during 10 min of post-flight tilting. CONCLUSION: We conclude that baseline sympathetic outflow, however measured, is higher in space than on earth, and that augmented sympathetic nerve responses to Valsalva straining, lower body suction, and post-flight upright tilt represent normal adjustments to greater haemodynamic stresses associated with hypovolaemia.
Document ID
20040087817
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Eckberg, D. L.
(Hunter Holmes McGuire Department of Veterans Affairs Medical Center and Medical College of Virginia at Virginia Commonwealth University Richmond, VA, United States)
Date Acquired
August 21, 2013
Publication Date
March 1, 2003
Publication Information
Publication: Acta physiologica Scandinavica
Volume: 177
Issue: 3
ISSN: 0001-6772
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: M01 RR00095
CONTRACT_GRANT: U01HL-56417
CONTRACT_GRANT: 5P01 HL56693
CONTRACT_GRANT: 1U01NS33460
CONTRACT_GRANT: 1U01HL53206
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Biomedical Research and Countermeasures
short duration
NASA Discipline Cardiopulmonary
STS-90 Shuttle Project
Review, Tutorial
Non-NASA Center
Flight Experiment
Review
manned

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