Abstract
The quantitative assessment of cardiovascular functions is particularly complicated, especially during any physiological challenge (e.g., exercise), with physiological signals showing intricate oscillatory properties. Signal complexity is one of such properties, and reflects the adaptability of the physiological systems that generated them. However, it is still underexplored in vascular physiology. In the present study, we calculate the complexity of photoplethysmography (PPG) signals and their frequency components obtained with the wavelet transform (WT), with two analytical tools—(i) texture analysis (TA) of WT scalograms, and (ii) multiscale entropy (MSE) analysis. PPG signals were collected from twelve healthy young subjects (26.0 ± 5.0 y.o.) during a unilateral leg lowering maneuver to evoke the venoarteriolar reflex (VAR) while lying supine, with the contralateral leg remaining stationary. Results showed that TA was able to detect a decrease in complexity, viewed as an increase in texture entropy (TE), of the PPG scalograms during VAR, similarly to MSE, suggesting that a decrease in the competence of vascular regulation mechanisms might be present during VAR. Nonetheless, TA showed lower sensitivity than MSE for low frequency spectral regions. TA seems to be a promising and straightforward analytical tool for the assessment of the complexity of PPG perfusion signals.
Highlights
The regulation of the cardiovascular system results from the adjustment of several biophysical phenomena, both electrical and mechanical
The performance of the reference multiscale entropy (MSE) method was superior under the conditions studied, these results suggest that texture entropy (TE) is an interesting and suitable tool for assessing the complexity of PPG microcirculation signals considered as wavelet transform (WT) scalograms, in particular for the analysis of high frequency components
In this paper we present for the first time the use of texture entropy (TE) for the quantification of complexity in microcirculatory perfusion signals, using MSE as a reference analytical tool
Summary
The regulation of the cardiovascular system results from the adjustment of several biophysical phenomena, both electrical and mechanical. Their coordination is highly complex, depending on the continuous feedback and cross-talk between effector organs and controlling systems [1]. Microcirculation signals are composed of both these central and peripheral components and provide an “integrated” view of cardiovascular function [4,5]. The contributions from these multiple regulation systems and their intricate interplay explain the oscillatory properties of microcirculation signals. These oscillatory properties are increasingly considered as a means to extract more sensible information
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
