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Effect of 6 degrees head-down tilt on cardiopulmonary function: comparison with microgravityBACKGROUND: Head-down tilt (HDT) of 6 degrees is a commonly used model of weightlessness, but there are few comparisons with actual microgravity. HYPOTHESIS: Our study was designed to prove that the changes in cardiopulmonary function seen in HDT would be similar to those seen in microgravity. METHODS: We compared measurements of cardiovascular and pulmonary function from three separate spaceflights of 14 to 17 d duration, with data collected during a 17-d period of HDT. RESULTS: HDT proved a good model of the cardiovascular response to microgravity, resulting in increases in cardiac output and stroke volume of a similar magnitude to those seen in microgravity, with a concomitant reduction in heart rate. By contrast, HDT was a poor model of the effects of microgravity on pulmonary ventilation and gas exchange. CONCLUSION: Pulmonary function in HDT approximated the changes seen in the 1-G supine posture, while in microgravity this was much closer to that seen in the 1-G upright position. The differences probably reflect the fact that changes in cardiovascular function result primarily from fluid shifts within the entire body, whereas changes in pulmonary ventilation are primarily a result of mechanical influences on the lung and chest and abdominal wall.
Document ID
20040088496
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Prisk, G. Kim
(University of California San Diego, La Jolla, 92093-0931, United States)
Fine, Janelle M.
Elliott, Ann R.
West, John B.
Date Acquired
August 21, 2013
Publication Date
January 1, 2002
Publication Information
Publication: Aviation, space, and environmental medicine
Volume: 73
Issue: 1
ISSN: 0095-6562
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: U01-HL53208-01
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Cardiopulmonary
manned
short duration
STS-90 Shuttle Project
Non-NASA Center
STS-58 Shuttle Project
STS-78 Shuttle Project
Flight Experiment

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