Abstract
In this study, the Lyapunov exponent (LE) of heart rate variability (HRV) is investigated for feasibility as an index of hemodynamics. In a previous study, we calculated the HRV and evaluated blood pressure fluctuations via the autonomic nervous activity during standing. Herein, we examine the LE of HRV using resampled electrocardiogram (ECG) R-R
interval (RRI) data. ECG and blood pressure measurements were obtained from healthy young (< 30 years) and older (≥ 65 years) subjects during rest-to-stand motion experiments. The LE calculated from HRV measurements were lower in older participants than young participants. In both age groups, the LE decreased when the RRI and blood pressure decreased. However, the LE was not significantly correlated with either the RRI or blood pressure. Further, the LE was not significantly correlated with the indices of autonomic nervous system activity. Thus, the LE could be used as an independent index to monitor fluctuations in circulatory dynamics. We believe that this preliminary work will be of use in developing medical applications using the LE for telemedicine and home nursing.
