The expert kernel program is designed for the diagnostics of the functional body state according to the heart rate variability. It is based on the idea that the cardiovascular system with its multilevel regulation is a functional system designed to provide a specified level of the functioning of the entire organism. Having complex neuroreflex and neurohumoral mechanisms, the blood circulation system provides for timely and adequate blood supply of appropriate structures. Other things being equal, it can be considered that to any specified level of the functioning of the entire organism corresponds the equivalent level of the functioning of the blood supply apparatus (V.V. Parin, 1967). This close correlation is explained with the help of the three-level management model in the body proposed by S.N. Braines and V.B. Svechinsky (1974).

The heart rate and the process of its management of the autonomic nervous system and humoral system are an important link in the adaptation of the organism to the conditions of external and internal environment. It makes it possible to use the characteristics of the heart rate for the evaluation of the functional body state as a whole. The average frequency of heartbeats reflects the end result of numerous regulatory influences on the blood circulation apparatus, characterizes the homeostasis formed during the adaptation process. The information on how this homeostasis has formed, the “cost” of adaptation is contained in the structure of the heart rate, its variability.

The main methods of the evaluation of the functional body state were formulated by R.M. Baevsky (1979) as a conception about the three most significant components of the functional body state: the initial level of functioning, regulation tension and the state of functional reserves.

The expert kernel program has been developed taking into account this conception. In order to create the data base of age-related and typological characteristics, rhythmograms of ten thousand healthy people without any pathology of the cardiovascular system have been analyzed. The mathematical apparatus of the expert kernel program is based on discriminator equations and decision rules.

During the development of the expert system the initial autonomic tone was taken to be the initial level of the body functioning. It reflects the background activity of the structures responsible for the regulation of the organism's functions in the process of adaptation and can be considered one of constitutional characteristics forming the type of body reaction to the influence of external functions (V.P. Kaznacheev, 1980). The autonomic tone was determined with the help of HRV (Heart-Rate Variability) statistical parameters in the state of rest, taking into account age-related characteristics of regulation and had three states: amphotonic, sympathicotonic and vagotonic.

As the initial condition of the autonomic nervous system effects the reaction type, the norm limits for other components of the functional state have been determined separately for each type of regulation for each particular age. Additional factors under consideration were age and sex. Thus, the degree of tension of the regulation mechanisms and functional reserves was determined taking into account age-related and typological characteristics. The method of evaluating functional reserves taking into account typological characteristics has been patented.

The degree of tension of regulatory systems was evaluated according to the correlation of HRV spectral components which reflect the interaction of autonomic and humoral regulatory mechanisms and their activity level (R.M. Baevsky, 1979; N.N. Danilova, 1992).

For the evaluation of the functional possibilities of the body HRV changes in load testing mode were analyzed. For this purpose we used an active tilt-test as the most convenient and adequate indicator of functional possibilities (D.I. Zhemaitite, 1989). The tilt-test was taken to evaluate the provision for the tone of the vascular channel and the functional state of the heart in accordance with the parameters of the transition process (L.I. Osadchy, 1982; D.I. Zhemaitite, 1989). The adaptation of the cardiovascular system to the load was determined according to the ration of the pulse rate taken in the state of calm and orthostasis (D.I. Zhemaitite, 1989; G.V. Ryabykina, 1996). The autonomic provision of the activity under the load was determined as the ration of statistic parameters of the heart rate in the state of calm and orthostasis (R.M. Baevsky and others, 1981).

Table. 2. Typification of the conclusions about the functional body state

The analysis of all information about the components of the functional state serves as the basis for the overall conclusion about the functional body state. The importance of each conclusion when evaluating the functional body state was determined empirically, with the help of clinical data of long-time patient supervision. Seven variants of conclusion are envisaged aimed at providing extended quantitative information about the tension of regulatory mechanisms and functional possibilities (Table 2). The typification of conclusions is in agreement with the work of many authors (R.M. Baevsky, 1979; E.M. Kazin, Y.P. Shorin, 1993) about adaptation types and the functional body state: conclusions 1-3 correspond to the satisfactory state, 4,5—to the strain of the body systems and 6,7—to the unsatisfactory state.