Evaluation of functional state of systems. Evaluation may be qualitative and quantitative. The presence (absence) of any waves on the curve presents quality evaluation, whereas their amplitude or frequency is their quantitative evaluation. For the evaluation of functional condition of any systems comparison of the results of measurements of function parameters to those that should be with the given system is needed. In order to be able to judge about the presence (absence) of pathology, it is not enough to measure just any parameter. For example, we have measured someone’s blood pressure and received the value of 190/100 mm Hg. Is it a high pressure or it is not? And what it should be like? To answer these questions it is necessary to compare the obtained result to a standard scale, i.e. to the due value. If the value obtained differs from the appropriate one, it speaks of the presence of pathology, if it does not, then it means there is no pathology. If blood pressure value of an order of 190/100 mm Hg is observed in quiescent state it would speak of pathology, while at the peak maximum load this value would be a norm. Hence, due values depend on the condition in which the given system is. There exist standard scales for the estimation of due values. There exist maximum and minimum due values, due values of quiescence state and peak load values, as well as due curves of functions. Minimum and maximum due values should not always correspondto those of quiescence state or peak load. For example, total peripheral vascular resistance should be maximum in quiescence state and minimum when loaded. Modern medicine makes extensive use of these kinds of due values, but is almost unfamiliar with the concept of due curves. Due value is what may be observed in most normal and healthy individuals with account taken of affiliation of a subject to certain standard group of alike subjects. If all have such-and-such value and normally exist in the given conditions, then in order for such subject to be also able to exist normally in the same conditions, he/she should be characterized by the same value. For this purpose statistical standard scales are applied which are derived by extensive detailed statistical research in specific groups of subjects. These are so-called statistical mathematical models. They show what parameters should be present in the given group of subjects. However, the use of standard tables is a primitive way of evaluation of systems’ functions. First, they provide due values characterizing only a group of healthy individuals rather than the given concrete subject. Secondly, we already know that systems at each moment of time are in one of their functional states and it depends on external influences. For example, when the system is in quiescence state it is at its lowest level of functional condition, while being at peak load it is at its highest level. What do these tables suggest then? They probably suggest due values for the systems of organism in quiescence state or at their peak load condition. But, after all, the problems of patients are not those associated with their status in quiescence state, and the level of their daily normal (routine) load is not their maximum load. For normal evaluation of the functional condition of the patient’s organism it is necessary to use not tabular data of due values, but due curves of functions of the body systems which nowadays are almost not applied. Coincidence or non-coincidence of actual curves of the body systems’ functions with due curves would be a criterion of their sufficiency or insufficiency. Hence, application of standard tables is insufficient and does not meet the requirements of adequate diagnostics. Application of due curves is more of informative character (see below). Statistical mathematical models do not provide such accuracy, howsoever exact we measure parameters. They show what values of parameters should be in a certain group of subjects alike in terms of certain properties, for example, males aged 20-30 years, of 165-175 cm height, smokers or non-smokers, married or single, paleface, yellow- or black-skinned, etc. Statistical models are much simpler than those determined, but less exact though, since in relation to the given subject we can only know something with certain degree (e.g. 80%) of probability. Statistical models apply when we do not know all elements of the system and laws of their interaction. Then we hunt for similar systems on the basis of significant features, we somewise measure the results of action of all these systems operating in similar conditions (clinical tests) and calculate mean value of the result of action. Having assumed that the given subject closely approximates the others, because otherwise he/she would not be similar to them, we say: “Once these (people) have such-and-such parameters of the given system in such-and-such conditions and they live without any problems, then he/she should have these same parameters if he/she is in the same conditions”. However, a subject’s living conditions do always vary. Change or failure to account even one significant parameter can change considerably the results of statistical researches, and this is a serious drawback of statistical mathematical models. Moreover, statistical models often do not reveal the essence of pathological process at all. The functional residual capacity (FRC) of lungs shows volume of lungs in the end of normal exhalation and is a certain indicator of the number of functional units of ventilation (FUV). Hence, the increase in FRC indicates the increase in the number FUV? But in patients with pulmonary emphysema FRC is considerably oversized. All right then, does this mean that the number of FUV in such patients is increased? It is nonsense, as we know that due to emphysema destruction of FUV occurs! And in patients with insufficiency of pumping function of left ventricle reduction of FRC is observed. Does this mean that the number of FUV is reduced in such patients? It is impossible to give definite answer to these questions without the knowledge of the dynamics of external respiration system function and pulmonary blood circulation. Hence, the major drawback of statistical models consists in that sufficiently reliable results of researches can be obtained only in the event that all significant conditions defining the given group of subjects are strictly observed. Alteration or addition of one or several significant conditions of research, for example, stature/height, sex, weight, the colour of eyes, open window during sleep, place of residence, etc., may alter very much the final result by adding a new group of subjects. As a result, if we wish to know, e.g. vitalcapacity of lungs in the inhabitants of New York we must conduct research among the inhabitants of New York rather than the inhabitants of Moscow, Paris or Beijing, and these data may not apply, for example, to the inhabitants of Rio de Janeiro. Moreover, standards/norms may differin the inhabitants of different areas of New York depending on national/ethnic/ identity, environmental pollution in these areas, social level and etc. Surely, one may investigate all conceivable variety of groups of subjects and develop specifications/standards, for example, for males aged from... to..., smokers or non-smokers of cigars (tobacco pipes, cigarettes or cigarettes with cardboard holder) with high (low) concentration of nicotine, aboriginals (emigrants), white, dark- or yellow-skinned, etc. It would require enormous efforts and still would not be justified, since the world is continually changing and one would have to do this work every time again. It’s all the more so impossible to develop statistical specifications/standards for infinite number of groups of subjects in the course of dynamic processes, for example, physical activities and at different phases of pathological processes, etc., when the number of values of each separate parameter is quite large. When the system’s details are completely uncertain, although the variants of the system’s reaction and their probabilistic weighting factorsare known, statisticalmathematicalmodel of system arises. Inaccuracy of these models is of fundamental character and is stipulated by probabilistic character of functions. In process of studying of the system details of its structure become apparent. As a result an empirical model emerges in the form of a formula. The degree of accuracy of this model is higher than that of statistical, but it is still of probabilistic character. When all details of the system are known and the mechanism of its operation is entirely exposed the deterministic mathematicalmodel appears in the form of the formula. Its accuracy is only stipulated by the accuracy of measurement methods. Application of statistical mathematical models is justified at the first stages of any cognition process when details of phenomenon in question are unknown. At this stage of cognition a “black box” concept is introduced when we know nothing about the structure of this “box”, but we do know its reaction to certain influences. Types of its reactions are revealed by means of statistical models and thereafter, with the help of logic, details of its systems and their interaction are becoming exposed. When all that is revealed, deterministic models come into play and the evaluation of the systems’ functions is made not on the basis of tabular data, but on the basis of due curve of the system function. Due curve of a system’s function is a due range of values of function of the given concrete system in the given concrete subject, with its load varying from minimum to maximum. Nowadays due curves are scarcely used, instead extreme minimum and maximum due values are applied. For example, due ventilationof lungs in quiescence state and in the state of peak load. For this purpose maximum load is given to individuals in homotypic groups and pulmonary ventilation in quiescence state and in the state of peak load is measured. Following statistical processing due values of pulmonary ventilation for the conditions of rest and peak load are obtained. The drawback of extreme due values consists in that this method is of little usefor the patients. Not all patients are able to normally perform a stress test and discontinue it long before due maximum value is achieved. The patient, for example, could have shown due pulmonary ventilation, but he/she just stopped the load test too early. How can the function be estimated then? It can be only done by means of due curve. If the actual curve coincides with the due curve, the function is normal at the site where coincidence occurred. If actual curve is lower than the due one, it is a lagging curve. Inclined straight line consisting of vertical pieces of line is the due curve. Vertical dotted straight line is the boundary of transition of normal or lagging function into the inadequate line (a plateau). The drawback of due curves is that in order to build them it is necessary to use deterministic mathematical models of systems which number is currently very low. They are built on the basis of knowledge of cause-and-effect relationship between the system elements. These models are the most complex, labor-consuming and for the time being are in many cases impracticable. Therefore, these models are scarcely usedin the sphere of applied medicine and this is the reason for the absenceof analytical medicine. But they are the most accurate and show what parameters should be present in the given concrete subject at any point of time. Only the use of due curve functions allows for evaluating actual curves properly. The difference of the deterministic mathematical models from statistical tables consists in that in the first case due values for the concrete given subject (the individual’s due values) are obtained, while in the second case due values for the group of persons alike the given subject are developed. The possibility of building deterministic models depends only on the extent of our knowledge of executive elements of the system and laws of their interaction. Calculation of probability of a thrown stone hitting a designated target can be drawn as an example of statistical standard scale in the mechanic. After a series of throws, having made certain statistical calculations it is possible to predict that the next throw with such degree of probability will hit the mark. If deterministic mathematical model (ballistics) is used for this purpose, then knowing the stone weight, the force and the angle of throw, viscosity of air, speed and direction of wind, etc., it is possible to calculate and predict precisely the place where a stone will fall. “Give me a spot of support and I will up-end the globe”, said Archimedes, having in view that he had deterministic mathematical model of mechanics of movements. Any living organism is a very complex and multi-component system. It’s impossible to account all parameters and their interrelations, therefore statistical mathematical models cannot describe adequately the condition of systems of organism. However, joint use of statistical and deterministic models allows, with sufficient degree of accuracy, to evaluate parameters of living system. In the lapse of time in process of accumulation of knowledge statistical models are replaced by deterministic. Engineering/technology is much simpler than biology and medicine because the objects of its knowledge are rather simple systems (machinery/vehicles) constructed by a man. Therefore, its development and process of replacement of statistical mathematical models for deterministic ones has made great strides as compared with medicine. Nevertheless, on the front line of any science including technical, where there is still no clarity about many things and still a lot has to be learnt, statistics stands its ground as it helps to reveal elements of systems and laws of their interaction. What do we examine the subject and conduct estimation of functions of the systems of his organism for? Do we do it in order to know to which extent he/she differs from the homothetic subject? Probably, yes. But, perhaps, the main objective of examination of a patient is to determine whether he/she can normally exist without medical aid and if not, what kind of help might be provided. Pathological process is a process of destruction of some SFU of the organism’s systems in which one of the key roles is played by a vicious circle. However, vicious circles start to actuate only if certain degree of load is present. They do not emerge below this level and do not destroy SFU, i.e. no pathological process emerges and no illness occurs below a certain threshold of loading (mechanical, thermal, toxic, etc.). Hence, having defined a threshold of the onset of the existence of vicious circle, we can learn the upper “ceiling” of quality of life of the given patient. If his/her living conditions (tempo of life) allow him/her not to exceed this “ceiling”, it suggests that the given subject will not be in poor health under these conditions. If the tempo of life requires more than the capacity of his/her organism may provide, he/she will be in poor health. In order not to be ill he/she should stint himself/herself in some actions. To limit oneself in actions means to reduce one’s living standard, to deprive oneself of the possibility to undertake certain actions which others can do or which he/she did earlier, but which are now inaccessible to the given patient on the grounds of restricted resources of his/her organism because of defects. If these restrictions have to do only with pleasure/delight, such as, for example, playing football, this may be somehow sustained. But if these restrictions have to do with conditions of life of the patient it has to be somehow taken into account. For example, if his/her apartment is located on the ground floor, then to provide for quite normal way of life his/her maximum consumption of О2 should be, e.g., 1000 ml a minute. But what one should do if he/she lives, e.g., on the third floor and in the house with no elevator, and to be able to get to the third floor on foothe/she should be able to take up 2000 ml/min О2, while he/she is able to uptake take up only 1000 ml/min О2,? The patient would then have a problem which can be solved only by means of some kind of health care actions or by changing conditions of life. In clinical practice we almost do not assess the patient’s functional condition from the stand point of its correspondence to living conditions. Of course, it is trivial and we guess it, but for the time being there are no objective criteria and corresponding methodology for the evaluation of conformity of the functional reserves of the patient’s organism with the conditions of his/her life activity. Ergonomics is impossible without systemic analysis. Major criterion of sufficiency of the organism’s functions in the given conditions of life is the absence of the occurrence of vicious circles (see below) at the given level of routine existential loads. If vicious circles arise in the given conditions, it is necessary either to somehow strengthen the function of the organism’s systems or the patient will have to change his/her living conditions so that vicious circles do not work, or otherwise he/she will always be in poor health with all the ensuing consequences. So, we need not only to know due minimum or maximum values which we may obtain using statistical mathematical models. We also need to know the patient’s everyday due values of the same parameters specific for the given concrete patient so that his/her living conditions do not cause the development of pathological processes and destroy his/her organism. To this effect we need deterministic mathematical models.