title: R-R interval variability with lower body positive pressure assessed by wavelet packet transform.
abstract: Lower body positive pressure (LBPP) is used for simulation of microgravity due to central fluid shift. In the present study, we evaluate R-R interval variability, which is sometimes considered as an index of human cardiovascular autonomic nerve status. 10 healthy male subjects were set in a chamber with standing position. Chamber pressure was raised 10 mmHg each for every 3 minutes, up to +40 mmHg. Wavelet packet transform (WPT) followed by Hilbert transform was employed to analyze time-dependent changes in low frequency component (LF) and high frequency component (HF) of R-R interval variability. Calf circumference lowered according to chamber pressure. ABP was maintained throughout measurements. R-R interval was significantly higher at +30 and +40 mmHg compared to that of control. Standing LBPP causes higher HF and lower L/H probably due to central fluid shift, and WPT followed by Hilbert transform shows time-dependent changes in R-R interval variability.
authors.affiliation: Gifu University, School of Medicine, Department of Physiology.
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tanaka
authors.forename: Taro M
authors.initials: TM
authors.lastname: Gotoh
authors.forename: Hironobu
authors.initials: H
authors.lastname: Morita
authors.forename: Alan R
authors.initials: AR
authors.lastname: Hargens
mesh_terms: D001273:Atmosphere Exposure Chambers; D001274:Atmospheric Pressure; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000033:anatomy & histology; D008297:Male; D011187:Posture / Q000502:physiology*