A.A. Mikheev – Dr. Sc. (Eng.), Professor, Department of Automated Control Systems,  V.F. Utkin Ryazan State Radio Engineering University

E-mail: maa0312@yandex.ru

T.A. Vityazeva – Assistant, Department of Automated Control Systems; Post-graduate Student, Department  of Information-Measuring and Biomedical Engineering, V.F. Utkin Ryazan State Radio Engineering University

E-mail: vsv630@yandex.ru

This article discusses the issues of joint processing of heart rhythm and respiration signals, carried out in order to analyze the stress state of the human body. The objective of this article is to find the cardiac rhythm and pneumogram signals at the stage of registration of the signals, ensuring maximum synchronization of the signals with each other. It is proposed to sample the breathing signal at the time points determined by the beginning of the next heartbeat cycle and delay them for the time of the next heart rhythmogram segment. In this case, to ensure synchronous recording of signals at the beginning of every n-th successive cycle of heartbeat (cardiac cycle), the n-th count of the pneumogram signal is taken and it is delayed until the next (n+1)-th cycle of heartbeat. At the same time, the measurement of the duration of the current n-th cardiac cycle begins. At the time of the beginning of the next (n+1)-th cardiac cycle, the duration of the previous n-th cardiac cycle is memorized and the value of the delayed n-th pneumogram sample is also memorized. Thus, the registration of the n-th sample of the pneumogram and the values of the duration of the n-th cardiac cycles occur at the same time points, ensuring the formation of synchronized time sequences of the cardiac rhythm and pneumogram.

These sequences can be directly analyzed to determine the correlation between them. It is also possible to interpolate these sequences by restoring intermediate values between the values of the pneumogram signal samples and between the durations of the neighboring cardiocycles. The synchronization of the interpolated sequences is not disturbed.

For the purpose of modeling, a set of programs has been developed that allows the formation of a sequence of time points corresponding to the beginnings of heartbeat cycles, and matched with the points of breathing signal sampling. The respiration signal is modeled by a simple harmonic signal. The signal at the output of the heartbeat cycle detector is modeled by a sequence of rectangular pulses with variable frequency. By modeling, it was shown that the proposed matched registration of pneumogram and heart rhythmogram signals can significantly increase the reliability of the assessment of respiration and heart rhythm interconnection. The proposed method is more than 10% superior in quality to an approach that uses additional processing, which also requires significant computational costs. Compared to the analysis of signals without synchronization, the gain can reach more than 50%.

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