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R-R interval variability with lower body positive pressure assessed by wavelet packet transform
Kunihiko Tanaka1, Taro M Gotoh, Hironobu Morita
1Gifu University, School of Medicine, Department of Physiology.
Uchu Seibutsu Kagaku
|December 17, 2003
Summary
Lower body positive pressure (LBPP) simulates microgravity by shifting fluids. This study found LBPP increases heart rate variability's high frequency component, indicating autonomic nervous system changes.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Research
- Space Medicine Simulation
Background:
- Lower body positive pressure (LBPP) is a method to simulate microgravity effects, specifically central fluid shifts.
- R-R interval variability serves as an indicator of the human cardiovascular autonomic nerve status.
Purpose of the Study:
- To evaluate the impact of standing LBPP on R-R interval variability in healthy males.
- To analyze time-dependent changes in cardiovascular autonomic nerve status under simulated microgravity conditions.
Main Methods:
- Utilized wavelet packet transform (WPT) and Hilbert transform to analyze R-R interval variability.
- Measured changes in low frequency (LF) and high frequency (HF) components of heart rate variability.
- Applied incremental LBPP up to +40 mmHg in 10 healthy male subjects.
Main Results:
- Calf circumference decreased with increasing chamber pressure.
- Mean arterial blood pressure (ABP) remained stable.
- R-R interval was significantly prolonged at +30 and +40 mmHg LBPP.
- Observed an increase in the high frequency (HF) component and a decrease in the LF/HF ratio.
Conclusions:
- Standing LBPP induces central fluid shifts, affecting cardiovascular autonomic regulation.
- Increased HF component and decreased LF/HF ratio suggest parasympathetic nervous system modulation.
- WPT combined with Hilbert transform effectively reveals time-dependent autonomic responses to LBPP.