XXXX volume variability and heart rate power spectrum in relation to posture changes in healthy subjects.

@entity1 @entity6355 @entity64
BACKGROUND: Power spectrum analysis of heart rate variability (HRV) can be used to assess the state of sympathovagal balance-modulating sinus node activity. @entity64 volume variability ( @entity6355 ) probably reflects the dynamics of physiological control mechanisms over time. MATERIAL/METHODS: Power spectrum HRV and @entity6355 were simultaneously measured in 44 healthy @entity1 . The values of the HRV and @entity6355 parameters were compared for the supine and upright body positions in three age groups (I: 20-40; II: 40-60; III: >60 years old). The total power (TP) of the very low (VLF:<0.05 Hz), low (LF: 0.05-0.15 Hz) and high (HF: 0.15-0.5 Hz) HRV and @entity6355 frequency bands were measured. The LF/HF and lnLF/lnHF ratios for HRV and @entity6355 were calculated. RESULTS: The upright position caused a significant decrease in HRV in the HF and lnHF bands and an increase in the LF/HF and lnLF/HF ratios in all groups. @entity6355 analysis for the supine position revealed significant differences in lnTP and HF values (between groups I and II) and in lnHF values (between groups I and II and I and III). @entity6355 analysis for the upright position revealed differences in lnTP (between groups I and II and I and III), lnVLF (between groups I and III and I and III), lnLF (between groups I and II and I and III) and lnHF (between groups I and II and I and III). CONCLUSIONS: The combined analysis of HRV and @entity6355 revealed different cardiovascular responses to postural stress in the three age groups considered.
