Platisa Mirjana M, Gal Vera
Institute of Biophysics, Faculty of Medicine, University of Belgrade, Visegradska 26/2, 11000 Belgrade, Serbia and Montenegro.
Physiol Meas. 2006 Feb;27(2):145-54. doi: 10.1088/0967-3334/27/2/005. Epub 2006 Jan 4.
The aim of this study was to examine the dependence of heart rate variability (HRV) measures on RR interval length and to find out relationships between linear and nonlinear measures. The spectral powers in very low (VLF), low (LF) and high (HF) frequency regions, short-term scaling exponent alpha(1) and sample entropy (SampEn) were determined. All spectral powers increased with increasing RR interval length until they reached a plateau. Neighbouring spectral powers were strongly correlated. The largest fraction of the spectrum consisted of VLF (from about 40 to 95%) and the smallest of HF, although HF was most sensitive to changes in RR interval length. SampEn is also increased with increasing RR interval, reaching a plateau. The dependence of alpha(1) on RR showed a deflection point at 0.5 s. Nonlinear measures can be expressed by spectral powers: alpha(1) by a linear function of ln(LF/HF) and SampEn by a quadratic function of ln HF. We concluded that during the day an increase of HR up to 120 beats min(-1) was reflected in a reduction in HF and LF and to a smaller extent in VLF and by decreased complexity and increased correlation in RR interval series. In sleep, HRV measures are at a plateau. We suggest that below intrinsic value, HR is regulated mainly by changes of parasympathetic activity, reflected in linear and nonlinear HRV measures.
本研究的目的是检验心率变异性（HRV）测量值对RR间期长度的依赖性，并找出线性和非线性测量值之间的关系。测定了极低频（VLF）、低频（LF）和高频（HF）区域的频谱功率、短期标度指数α(1)和样本熵（SampEn）。所有频谱功率均随RR间期长度增加而增加，直至达到平稳状态。相邻频谱功率高度相关。频谱的最大部分由VLF组成（约40%至95%），最小部分由HF组成，尽管HF对RR间期长度的变化最为敏感。SampEn也随RR间期增加而增加，直至达到平稳状态。α(1)对RR的依赖性在0.5秒处出现一个拐点。非线性测量值可以用频谱功率表示：α(1)是ln(LF/HF)的线性函数，SampEn是ln HF的二次函数。我们得出结论，在白天，心率增加至120次/分钟会导致HF和LF降低，VLF降低程度较小，RR间期序列的复杂性降低且相关性增加。在睡眠中，HRV测量值处于平稳状态。我们认为，低于固有值时，心率主要由副交感神经活动的变化调节，这反映在线性和非线性HRV测量值中。
