Multifractal analysis of central (electrocardiography) and peripheral (laser Doppler flowmetry) cardiovascular time series from healthy human subjects

Abstract

Analysis of the cardiovascular system (CVS) activity is important for several purposes, including better understanding of heart physiology, diagnosis and forecast of cardiac events. The central CVS, through the study of heart rate variability (HRV), has been shown to exhibit multifractal properties, possibly evolving with physiologic or pathologic states of the organism. An additional viewpoint on the CVS is provided at the peripheral level by laser Doppler flowmetry (LDF), which enables local blood perfusion monitoring. We report here for the first time a multifractal analysis of LDF signals through the computation of their multifractal spectra. The method for estimation of the multifractal spectra, based on the box method, is first described and tested on a priori known synthetic multifractal signals, before application to LDF data. Moreover, simultaneous recordings of both central HRV and peripheral LDF signals, and corresponding multifractal analyses, are performed to confront their properties. With the scales chosen on the partition functions to compute Renyi exponents, LDF signals appear to have broader multifractal spectra compared to HRV. Various conditions for LDF acquisitions are tested showing larger multifractal spectra for signals recorded on fingers than on forearms. The results uncover complex interactions at central and peripheral CVS levels.

Generalized fractal dimensions of laser Doppler flowmetry signals recorded from glabrous and nonglabrous skin

“…2͒ as awaited for such a signal. 31 Moreover, Z͑1,͒ = 1 at each scale, which is in accordance with Eq. ͑2͒.…”

“…This is in accordance with previous works using another method. 31,39 Moreover, this study shows that, contrary to pure multifractal signals, like binomial measures, the scale chosen for the multifractal analysis of an experimental LDF signal has an impact on the estimated generalized fractal dimensions. In addition, the spatial variations and the low variations for the estimated generalized fractal dimensions at the scales corresponding to the cardiac regulating mechanisms in the hand palms tend to indicate that the possible multifractal properties of the LDF signals are not principally governed by a central command, predominant in these zones.…”

“…Recently, multifractal analysis has been used for the study of physiological signals. 30,31 The multifractal formalism is based on the partition function, which is defined as ͑details can be found in Ref. 32͒…”

Comparison of laser Doppler and laser speckle contrast imaging using a concurrent processing system

“…They are both useful as they can non-invasively obtain images of blood flow for a range of applications such as burn depth assessment [1], [2], wound healing [3], ophthalmology [4], [5], cardiac activity analysis [6], [7] and studies of stimulant reactions of cortical activity [8][9][10]. They have also been used in numerous tissue phantom studies e.g.…”

Application of Katz algorithm for fractal dimension in analysis of room impulse response

“…Multifractal spectrum and its parameters are usually investigated for classification of signals, while fractal dimension is used for recognition of some characteristics of the signal. This is used in a variety of research areas including biomedical signal processing [4]- [6], physics [7], acoustics [8]- [10], and many others.…”