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Effects of head-down bed rest on complex heart rate variability: response to LBNP testing
A L Goldberger1, J E Mietus, D R Rigney
1Cardiovascular Division, Beth Israel Hospital, Boston, Massachusetts.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|December 1, 1994
Summary
Short-term head-down bed rest reduces heart rate complexity in women. This decrease in physiological heart rate variability during lower body negative pressure (LBNP) testing may indicate altered cardiovascular regulation.
Area of Science:
- Cardiovascular Physiology
- Spaceflight Physiology
- Nonlinear Dynamics
Background:
- Head-down bed rest simulates spaceflight's physiological effects.
- Spaceflight can alter cardiovascular regulation and heart rate variability.
- Complex physiological heart rate variability is crucial for adaptation.
Purpose of the Study:
- To investigate the impact of short-term head-down bed rest on heart rate variability.
- To assess if bed rest decreases the complexity of heart rate signals.
- To evaluate heart rate complexity as a marker for physiological changes.
Main Methods:
- Eight healthy women underwent 13 days of 6° head-down bed rest.
- Continuous heart rate data were collected using Holter recordings.
- Heart rate variability was analyzed using conventional and nonlinear (approximate entropy) methods during lower body negative pressure (LBNP) tests.
Main Results:
- Tolerance to LBNP significantly decreased during bed rest.
- Heart rate approximate entropy (complexity) was significantly reduced on bed rest days.
- Conventional heart rate variability measures did not change significantly.
Conclusions:
- Short-term bed rest decreases heart rate complexity in healthy women.
- Reduced heart rate complexity during LBNP may indicate impaired cardiovascular adaptation.
- Approximate entropy is a sensitive marker for detecting changes in physiological variability.