In dissertation the important scientific task is solved – the phonocardial signal synchronously registered with electrocardiosignal mathematical model and analyzing methods improvement taking into account the mechanism of its generation for the human CVS state early diagnosis in automated diagnostic systems reliability increasing.
The heart rate (HR) is determined by the sinus node automatism, which is modulated by feedback through the influence of vegetative, humoral, and local factors. Therefore, the heart work can be described as «modulation» – each of the action potential impulses sequence causes the response in the form of series of consecutive time-varying heart contractions/relaxation. The shape, duration and phase shifts of these impulses may vary, depending on the physical loadings, the emotional state and a whole set of other exogenous and endogenous influences. The responses wouldn’t have constant parameters depend on the factors such as: the conducting system state: the Gis beam right leg blockade, the effort of the blood flow through the heart structures (prolapse, stenosis, aneurysms), postinfarctional scarring, and many other factors, which has a great diagnostic value.
Based on the considerations set in R. M. Baevsky, A. A. Talakov «Balistocardiography» work, the person`s cardiovascular system should be regarded as a closed hemodynamic one, where the primary information carrier about it is, among other things, is a phonocardiosignal generated by mechanical and acoustic processes in the system. It is used for obtaining additional (often critical) data to increase the researched object`s evaluation parameters reliability and the bimedia principle as the separation of the signal energy generated by one source, in space-time into two «flows» of different physical nature and (electric and mechanical) introduced the concept of «shunting».
By shunting we understand the principle of obtaining complementary information about the object through «bypass» «short» way, in particular, getting of the certain informative parameters from the signal of another physical process nature (electrical, in contrast to the acoustic) of the same genesis in terms of the signal-system concept.
Preprocessing was carried out according to the algorithm: signal detrending, smoothing, finding the repeatability period for the P-wave interval.
A new application of the periodically correlated random process as a mathematical model of a phonocardiosignal synchronously registered with electrocardiosignal is obtained, which, unlike known ones, represents the mechanism of its genesis. Based on a previously grounded mathematical model and on the concept of «shunting», the synphase method of statistical processing of a phonocardiosignal synchronously registered with an electrocardiosignal in automated diagnostic systems was modified, taking into account a phonocardiosignal genesis mechanism. As the processing result, the value of the phonocardiosignal spectral components were obtained, which are its information-invariant features and with certain certainty characterizing the functional state of the human SSS. Since the synphase method is insensitive to the coherent components presented in the signal, therefore no need to use alien crosstalk effects minimization procedure. Since the developed algorithm is focused on its application in the patient’s СVS state remote monitoring systems, so in order to trend minimization, it is proposed to use the hardware implementation the high-pass Bessel filter (Sallen-Key topology) implementation, which has uniform (flat) amplitude–frequency response characteristics (AFR) (minimal equiripple in passband), linear phase-frequency characteristic (PFR), and the constant group delay, parameter variation resistance. Bessel Discrete Filters do not have this property. Therefore, to process the signal at the software level, the FIR-filtering (which provides linearity of the PFR) is applied by the overlap-add method (OLA), which gives significant advantage in using hardware and software resources, in comparison with time-domain filtering (convolution)
As a result of processing, the phonocardiosignal spectral components, which are its informatively invariant features and with definite reliability characterize the functional state of the human cardiovascular system, is obtained.A method for simulating a phonocardiac signal based on periodically correlated random sequences has been developed to verify the results of studies. A package of computer programs has been created for the automated processing of phonocardiac signals and for carrying out simulation experiments for automated diagnostic systems.Key words: phonocardio-signal, electrocardiogram, genesis of phonocardial signal, periodically correlated random process, spectral components, reliability, verification, computer simulation.
