Known works have shown a decrease in the coherence of the process of parasympathetic control of heart rate variability and the process of respiration during healthy aging. To get an idea of the reasons for the decrease in the coherence of the processes under study, in this work we investigated the possibility of using the method for assessing the directional coupling based on modeling of phase dynamics to analyze the directional couplings between the processes of parasympathetic control of heart rate variability and the respiration process. Due to the complexity, nonstationarity and strong nonlinearity of the processes under study, an important and nontrivial task is to choose the duration of the analyzed time series of high-frequency oscillations of the RR-intervals signal and respiration in calculating the indices of directional coupling. This work shows the possibility of using the method for assessing the directional coupling with the length of the analyzed time series from 15 to 450 characteristic periods of oscillations.
The work aims to study the features of autonomic control of the cardiovascular system in two groups of patients with Covid-19: with and without arterial hypertension. A total of 15 pairs of 20-minute electrocardiogram and photoplethysmogram signals were registrated in each group. We used the methods of spectral analysis, as well as the previously proposed method for assessing the phase synchronization of 0.1-Hz rhythms of signals of autonomic control of heart rate and blood pressure. The data of patients with chronic arterial hypertension showed a lower level of synchronization than patients without it. This is probably due to the peculiarities of autonomic control of the cardiovascular system in patients with chronic arterial hypertension.
We provided a combined analysis of electroencephalogram and functional near-infrared spectroscopy signals in order to investigate the process of prolonged visual perception. We investigated perception and decision-making processing during long-term and intense cognitive load. We found characteristic changes in electrical and hemodynamic activities during the neurophysiological experiment. The relationship was found between the EEG characteristics and the ΔO2Hb oscillation registered with the help of functional near-infrared spectroscopy.
In this work, we analyzed the signals of heart rate variability and leg’s photoplethysmograms of newborns. A series o f experiments included 10 conditionally healthy subjects; each recording was carried out for 15 minutes during feeding. We used methods of spectral analysis and methods of nonlinear dynamics. This work shows some features of the autonomic nervous regulation of the cardiovascular system in newborns, an assessment of the degree of synchronization and the coupling of the loops for regulating heart rate variability and vascular tone using methods for calculating crossspectrum, the coherence coefficient and the total percentage of phase synchronization.
The spectral properties and synchronization of low-frequency (LF) oscillations during the tilt test were studied for the heart rate variability (HRV) and the finger photoplethysmogram (PPG) of healthy subjects. Dynamics of the LF oscillations in the PPG and synchronization strength between the HRV and the PPG were found to be inhomogeneous among healthy subjects, which suggest existence of individual differences in characteristics of adaptive reactions of the cardiovascular autonomic control.
KEYWORDS: Heart, Circulatory system, Cardiovascular system, Medicine, Electrocardiography, Signal analyzers, Signal processing, Systems modeling, Cardiovascular surgery
The paper is devoted to the analysis of dynamic of interactions between signals of autonomic circulatory regulation. We investigated two-hour experimental records of 30 healthy people. Phase synchronization was studied using the signals of the electrocardiogram and the photoplethysmogram of vessels. We found the presence of long synchronous intervals in some subjects. For analysis of the dynamic we calculated autocorrelation functions. The analysis made it possible to reveal indirect signs of the influence of the humoral regulation system.
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