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Effects of head-down bed rest on complex heart rate variability: Response to LBNP testingHead-down bed rest is used to model physiological changes during spaceflight. We postulated that bed rest would decrease the degree of complex physiological heart rate variability. We analyzed continuous heart rate data from digitized Holter recordings in eight healthy female volunteers (age 28-34 yr) who underwent a 13-day 6 deg head-down bed rest study with serial lower body negative pressure (LBNP) trials. Heart rate variability was measured on a 4-min data sets using conventional time and frequency domain measures as well as with a new measure of signal 'complexity' (approximate entropy). Data were obtained pre-bed rest (control), during bed rest (day 4 and day 9 or 11), and 2 days post-bed rest (recovery). Tolerance to LBNP was significantly reduced on both bed rest days vs. pre-bed rest. Heart rate variability was assessed at peak LBNP. Heart rate approximate entropy was significantly decreased at day 4 and day 9 or 11, returning toward normal during recovery. Heart rate standard deviation and the ratio of high- to low-power frequency did not change significantly. We conclude that short-term bed rest is associated with a decrease in the complex variability of heart rate during LBNP testing in healthy young adult women. Measurement of heart rate complexity, using a method derived from nonlinear dynamics ('chaos theory'), may provide a sensitive marker of this loss of physiological variability, complementing conventional time and frequency domain statistical measures.
Document ID
19950039898
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Goldberger, Ary L.
Mietus, Joseph E.
Rigney, David R.
Wood, Margie L.
Fortney, Suzanne M.
Date Acquired
August 16, 2013
Publication Date
December 1, 1994
Publication Information
Publication: Journal of Applied Physiology
Volume: 77
Issue: 6
ISSN: 8750-7587
Subject Category
Life Sciences (General)
Accession Number
95A71497
Funding Number(s)
CONTRACT_GRANT: NIH-R01-HL-42172
CONTRACT_GRANT: NAG9-514
Distribution Limits
Public
Copyright
Other

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