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.
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.
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.
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: Time delay generators, Oscillators, Analog electronics, Interference (communication), Mathematical modeling, Data transmission, Systems modeling, Complex systems
A method for the reconstruction of time-delayed feedback system is investigated, which is based on the detection of synchronous response of a slave time-delay system with respect to the driving from the master system under study. The structure of the driven system is similar to the structure of the studied time-delay system, but the feedback circuit is broken in the driven system. The method efficiency is tested using short and noisy data gained from an electronic chaotic oscillator with time-delayed feedback.
KEYWORDS: Mathematical modeling, Heart, Data modeling, Cardiovascular system, Signal processing, Numerical modeling, Systems modeling, Linear filtering
A model of human cardiovascular system is proposed to describe the main heart rhythm, influence of autonomous regulation on frequency and strength of heart contractions and resistance of arterial vessels; process of formation of arterial pressure during systolic and diastolic phases; influence of respiration; synchronization between loops of autonomous regulation. The proposed model is used to simulate the dynamics of heart rate and arterial pressure during passive transition from supine to upright position. Results of mathematical modeling are compared to original experimental data.
We proposed the model of cardiovascular system which describes the sinus rhythm, autonomic regulation of heart and arterial vessels, baroreflex, arterial pressure and respiration process. The model included a self-oscillating loop of regulation of mean arterial pressure. It was shown that suggested model more accurately simulated the spectral and statistical characteristics of heart rate variability signal in comparison with the model proposed earlier by Seidel and Herzel.
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