BIOELECTRIC MANAGEMENT

From Big Medical Encyclopedia

BIOELECTRIC MANAGEMENT — the way of management based on use as managing influences of bioelectric potential of a live organism. The theoretical and experimental sides of the problem of B. at. are a basis for creation of the systems of bioelectric management (SBM). Systems of biological management are a specialized version automated control system (see) and similarly reflex arc in biol, systems turn on the sensor (an analog of a receptor), a logical element (an analog of a ganglion) and an executive element (an analog of a muscle or gland). Such systems are more and more widely applied in orthopedics, cardiovascular surgery, during the development of active prostheses (see) the amputated top and bottom extremities, and also at prosthetics injured as a result of a heart attack of conduction paths of heart by means of pacemakers (see. Cardiostimulation ). Thanks to the researches conducted in the area B. at., in medicine arose and intensively the recent trend develops — prosthetics bioelectric (see). Development of problems B. at. it is very urgent also for diagnosis, biotelemetry (see), therapy and theoretical medicine.

Three main problems are developed. The first is the problem of reception biol, information. The new principles of assignment of biopotentials, types of electrodes sensors are for this purpose developed, questions of decrease in the noise arising owing to the electrochemical processes accompanying interaction of the sensor with fabric are investigated.

Other problem B. at. development of questions of technical transformation and processing of bioelectric information is. Here special importance is gained by development of ways of allocation of a final signal from biological and technical noise; the choice of the logical scheme or a way of transformation biol, information (in an analog or digital form) from the point of view of the maximum noise stability and reliability at development of managing teams. The third problem B. at. — development of compact and reliable executive servo-drivers (amplifiers) working according to commands of logic and other devices of processing of bioelectric information. Here difficult technical issues of power and a design of prostheses with medical questions of their connection (implantation) with fabrics and bodies are closely closed.

In the field of studying bioelectric phenomena (see), accompanying processes of excitement, essential results are achieved. Methods and means of registration of biocurrents of a brain (see Elektroentsefalografiya), hearts are developed and are improved (see. Elektrokardiografiya ), sensitive elements of a retina of an eye (see. Elektroretinografiya )), skeletal muscles (see. Electromyography ), amplitude and frequency characteristics of biocurrents are studied in detail.

Fig. 1. Miogramma of biocurrents of a beam sgibatel of a brush (1) and mekhanogramm of bending of a brush (2); and — the moment of giving of a signal on bending (emergence of bioelectric potential precedes the beginning of bending).

It is well known that any movement of a live organism is preceded and followed by change of biocurrents of the corresponding muscles. It visually illustrates the figure 1 where are written at the same time down mechano-gram of the movement of bending of a brush and a miogramm of a biocurrent of a muscle of a sgibatel of a brush.

Any system including the person and the technical device managed by it can be considered as a biomechanical control system, in a cut the program of work of the technical device is developed by c. the N of page of the operator is also coded so that to cause his relevant movements («a code of the movement») making managing impacts. Here it is necessary to understand as the movement not only directly mechanical motion, but also, e.g., sounds of the speech, etc. So, the car printing from dictation can be also carried to this class of systems. The movements of the person are not the unique source of control signals in a biomechanical control system. If it was succeeded to give the commands going from c. the N of page directly on an operating controls of the technical device, would carry out system of direct bioelectric control without the need for any code conversion.

However lack of the effective ways allowing to take from c. N of page the relevant information, insufficient level of our knowledge of the ratios connecting any activity of the person with a condition of biopotentials of its c. N of page, exclude so far an opportunity to directly use these signals for purposeful management.

During the processing of bioelectric information in systems of bioelectric management indirect methods of extraction of managing information, based on use of miografichesky methods found application. At the same time managing information is obtained by processing of the signals of the bioelectric excitement of muscles arising under the influence of managing influences of c registered miografichesk. N of page that gives the chance to catch the teams generated by it irrespective of, they cause the relevant movements or not. In this case the disabled person, at to-rogo is amputated, e.g., a hand, can manage the technical device (see. Prosthetics bioelectric ), using skill of management of a hand, usual for it — for this purpose enough to obtain information on the teams arriving from c. N of page to the corresponding muscles. As a result of miografichesky researches it was established that dependence between total muscular effort and power of biopotentials in certain limits of values of these sizes can be considered linear. Idea that the integral effect of reduction of muscles is proportional to the power of fluctuations of their biopotentials was the basis during the designing of the first systems of biocontrol.

The principle of bioelectric management, in essence, was used in the first devices intended for registration of bioelectric activity (see. Bioelectric potential ). In any of such devices the bioelectric signal which is taken away from a live organism influences the chart recorder, carrying out thereby functions of management of it.

One of the first bioelectrical systems intended directly for implementation of function of management should be considered probably the device used during the performance of work, connected with definition of a lethal dose of electric blow (the USA, 1936). Among the made experiments were also such in which the biocurrent of a cardiac muscle managed the moment of giving of electric blow. In 1952 questions of use of the efforts developing in the course of reduction of muscles of a stump for management of inclusion and switching off of a prosthesis with the electric drive were investigated; then it was suggested about an opportunity to use the bioelectric signal arising at reduction of a muscle for this purpose.

Despite the high general level of the equipment, creation of electrotechnical, hydraulic, pneumatic, electrostrictive and other servo-drivers with the minimum dimensions and weight at the maximum reliability remains a complex technical problem.

The «programs» of management realized by the systems stated above are rather elementary; they are limited only to giving of signals on inclusion and switching off of the technical device; at the same time even these experiences testified to ample opportunities of use of bioelectrical systems for the most various purposes of management.

Fig. 2. The block diagram of the simple (opened) system of bioelectric management.

In 1957 the block diagram of the simple (opened) system of any bioelectric management (fig. 2) is developed. There are bioelectric signals which are taken away from a muscle, level of excitement the cut changes according to «program» of c. N of page, are processed in the control unit of the technical device possessing an autonomous energy source and used for control of executive mechanisms of system. One of the most important improvements of the SSU should consider introduction of negative feed-backs (see. Feed-back ).

Fig. 3. Model of a bioelectrical system of traffic control of an artificial brush (TsNIIPP, 1957).

In the figure 3 the first model of the bioelectrical system constructed in 1957 in Central research in-those prosthetics and prosthetic engineering (TsNIIPP), issued in the form of the artificial brush of the person managed by biocurrents of the muscles bending and unbending fingers of a hand is represented.

For assignment of biocurrents the so-called laid on electrodes (used, e.g., in an electromyography), established on the sites of skin located directly over the muscle used for management were used. This way of assignment was widely used most, in particular, in bioelectric prosthetics.

Fig. 4. The oscillogram of biocurrents from a surface of a sgibatel of fingers (1) and corresponding signals (2) used for management of an artificial brush of the movements (below an otmetchik of time).
Fig. 5. Functional flowchart of system of bioelectric management. In an upper part of the drawing the nature of transformation of bioelectric signals after escaping of various blocks of system is shown (1 — after strengthening by the electronic linear amplifier; 2 — after escaping of the two-half-period rectifier; 3 — after an exit from the integrating block; 4 — after an exit from the device creating impulses of constant amplitude and duration). The system of bioelectric management turns on two channels: 1 — 4 and 11 — 41 (1 and 11 — electronic linear amplifiers; 2 and 21 — two-half-period rectifiers; 3 and 31 — the integrating blocks; 4 and 41 — the device creating impulses of constant amplitude and duration); 5 — the block of strengthening on power; 6 — a control oscilloscope

In the figure 4 the oscillogram of the biocurrents which are taken away by laid on electrodes from a superficial sgibatel of fingers under various conditions of his tension is submitted. The difficult type of a curve is explained by the fact that the taken-away biocurrents represent a cooperative effect of action of biocurrents of muscle fibers of this muscle, and also numerous fluctuations of the biopotentials generated by adjacent muscles. In this system biocurrents from two antagonistic muscles — a sgibatel and a razgibatel of fingers were at the same time taken away. As a result of it on an entrance to a technical part of system two groups of control signals (fig. 5, the functional flowchart) moved. Each of the potentials removed from the electrodes pasted on skin considerably amplified the electronic linear amplifier (fig. 5, 1) and arrived on an entrance of the two-half-period rectifier (fig. 5, 2); from an exit of the rectifier tension moved on an entrance of the integrating block (fig. 5, 5), tension at the exit to-rogo approximately proportional (at the corresponding choice of parameters of the integrating chain) to an instantaneous value of power of biocurrents.

In the model represented in the figure 3 as executive body (servomechanism), setting in motion an artificial brush, the device managed by discrete current parcels (the so-called electromechanical step engine) was designed. This feature of the executive mechanism resulted in need to enter continuous and discrete transformation into the block of processing of managing information. For this purpose continuously changing tension from an exit of the integrator (fig. 5, 3) moved on the device (fig. 5, 4) creating impulses of constant amplitude and duration. (In the bottom of fig. 4 these discrete signals submitting as if the program of the movement of an artificial brush are written down in the form of vertical hyphens which frequency changes according to change of level of potential of muscles.)

After strengthening on the power (fig. 5, 5) the created impulses move on an entrance of the mechanical device. The control oscilloscope (fig. 5, 6) provides a possibility of sighting behind the size of stress removed from a muscle. The step servo-driver managed by two chains of such discrete signals works in the differential mode.

During the designing of the first model of a bioelectrical system the aim to approve the principle B. at was pursued. technical device. It is natural that at the same time questions of weight reduction and dimensions of system, its reliability and durability paled into insignificance. The intensifying equipment (in fig. 3 it is not shown) since installation needed to be protected from external aimings was the most bulky and heavyweight part of system. Despite these shortcomings, the first model of a bioelectrical system confirmed a full opportunity to realize B.'s idea at. also defined problems of further researches. As a result of the subsequent developments the small-size electronic control units constructed on semiconductor devices were created and various executive nodes of both discrete, and continuous action are developed.

Fig. 6. Bioexact manipulator.

The so-called bioexact manipulator (fig. 6) created by Institute of engineering science of Academy of Sciences of the USSR and TsNIIPP in 1958 is of the greatest interest. This manipulator operated as a peculiar muscular amplifier and could increase repeatedly force of a skhvat in comparison with the effort developed by the person. Its scheme included the block of setup of an intensification coefficient.

Fig. 7. Conditional scheme of the bioexact manipulator: 1 — the electric motor — an energy source; 2 — dvupolostny a hydraulic pump; 3 — the electromagnets, setting in motion needles which are blocking off the traffic of the liquid arriving under the influence of a hydraulic pump in monitors; 4 — a power hydraulic cylinder; 5 — an artificial brush; 6 — a bracelet with the electrodes imposed on skin of a hand of the operator, which are taking away biocurrents; 7 — a node of management of the manipulator; 8 — food of a node of management of the manipulator. Shooters specified the direction of fluid movement from a hydraulic pump to a power hydraulic cylinder, the direction of the movement of a pusher of a hydraulic cylinder and the movement of fingers of an artificial brush.

In the figure 7 the conditional scheme of this manipulator is shown. Unlike the first model (fig. 3), the executive system of continuous type is constructed with use of a hydraulic actuator. The electric motor (1) which sets in motion dvupolostny a hydraulic pump (2) is an energy source. From the pump the pressurized fluid comes to monitors. The fluid flow in these devices is blocked by the needles set in motion by electromagnets (3). At the same time the signals determining the level of excitement of electromagnets and respectively — the provision of needles come to monitors from a node of management (7). Depending on it there is a distribution of the fluid flows bypassed in working cavities of a power hydraulic cylinder (4). The hydraulic cylinder is connected to a pusher, setting in motion skhvat (5) artificial brushes.

As a source of the signals managing the level of excitement of magnets serve the biocurrents which are taken away by laid on electrodes from the muscles bending and unbending fingers of hands of the operator. Electrodes are strengthened in the special bracelet which is put on a hand of operator (6). Assignment and processing of biosignals is made on a symbolic circuit (fig. 5) except that need of transformation of a continuous signal to set of the discrete current parcels modulated on frequency disappears.

During creation of the bioexact manipulator much attention was paid to development of a compact electronic control unit, power supply to-rogo was carried out from the tiny cadmium-nickel accumulator. Existence of a transformer entrance protected system from influence of external noise and aimings. Dimensions of the control unit allowed to use it and to place in such devices as, e.g., a sleeve of a prosthesis of a forearm.

In the USSR and abroad in problems B. at. the central place was taken by works on practical implementation of the idea of B. at. in the field of prosthetics which were developed in a number of the countries after in 1950 in the Soviet Union the first samples of prostheses of a forearm with bioelectric management were created and given to disabled people. Along with it the researches aiming to increase efficiency and to expand opportunities and, respectively, range of application of a new way of management for the research, diagnostic and medical purposes continue.


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A. E. Kobrinsky.

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