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.
KEYWORDS: Mathematical modeling, Cardiovascular system, Biological research, Heart, Signal detection, Data modeling, Control systems, Bandpass filters, Distance measurement, Process modeling
Study aims to adopt the cross-recurrence analysis for detection of coupling between the loops of sympathetic regulation of cardiovascular system. To test the applicability of the method and to set its parameters it was applied to the mathematical model of cardiovascular system that has a structure similar to the structure of the real system. To investigate whether the cross-recurrence analysis reflects the dynamics of autonomic control the authors conducted four numerical experiments with gradually decreasing activity of sympathetic regulation. No correlation was found between the results of cross-recurrence analysis and the coupling strengths.
We investigate the dynamics of the networks of 100 identical bistable Hodgkin-Huxley neurons with scale-free, small-world and random topologies. For all of them, we discover a phenomenon when one part of the neurons are in the resting state, while the other one is in the oscillatory regime in a certain area of coupling strength and external current amplitude. We investigate this phenomenon and explain it by neuron interaction similar to the short pulse of external current which is able to switch the neuron regime from resting to oscillatory one and vice versa. We find the differences on this phenomenon for different topologies and investigate the evolution of it with increasing of external current.
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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