Index for Evaluating Heart Rate Variability based on the Extreme Point of Time Series

Abstract

Keywords : number of extreme point , heart rate variability , autonomic functionIn this study, it aimed at the proposal of real time and continuous estimating method of physiological states using biological signals. The proposal method will be one of the basic technology to develop physiological state monitor. The proposal index is defined in the ratio of the number of extreme points of the heart rate time series and the number of heart rate. This index is called NEP. NEP is defined as equ. (1).In this equation, n is the number of total heart beats, and R ( i ) is the i -th R-R interval. The characteristic of the NEP was shown by simulation analysis. The NEP was compared with classical indices of heart rate variability by the analysis of measured heart rate time series. NEP decreased significantly (p<0.05) when posture changed from supine to standing. In this case, the autonomic nervous activity balance changes from the parasympathetic to the sympathetic nerve. Moreover, the NEP was correlated with the respiratory frequency in supine position (p<0.01). It is not necessary to consider individual variation of NEP in the physiological state evaluation. Standardization process or relative value is not necessary to compare individual persons. This parameter is applicable to evaluate physiological state at real time and continuously.