REOGRAFIYA (Greek rheos a current, a flow + grapho to write, represent; synonym: impedance pletizmografiya, reopletizmografiya, elektropletizmografiya) — the general name of a method of a research of a krovenapolneniye of bodies and fabrics or separate body parts on the basis of registration of changes of their electric resistance. The river finds broad application in clinic and an experiment on animals as the method allowing to estimate objectively changes of a pulse krovenapolneniye and properties of a vascular wall in dynamics; it is used for different diagnosis of organic and functional vascular changes both in arterial, and in venous beds; for studying of features of collateral circulation, effect of medicinal substances, the mechanism of extreme impacts on an organism and so forth. For this purpose in a wedge, practice R.'s kinds, e.g., by R. of a brain are used (see. Rheoencephalography ), R. of lungs (see. Reopulmonografiya ), R. of heart (see. Reokardiografiya ), R. of a liver (see. Reogepatografiya ), R. of an eye (see. Reooftalmografiya ), R. of the lower and upper extremities (reovazografiya) etc.
Biophysical bases of a reografiya
Essence of a method P. consists in the following: on the studied object impose electrodes and pass through them electric current of high frequency. Change of degree of a krovenapolneniye and speed of the movement of blood in blood vessels is followed by fluctuations of electric resistance in the living tissues located between electrodes.
In a habit view this communication is defined by A. A. Kedrov's formula:
dV/V = dR/R,
where dV/V — relative change of volume of fabric in the explored site almost equal to change of volume of blood in this site; dR/R — relative change of resistance of this site.
During a cardial cycle dR value changes according to changes of a krovenapolneniye of the studied object or the site of fabric: decreases under a certain law at a systole and increases at a diastole. Graphic record of dependence dR in time is called reogrammy. Parameters of the reografichesky waves forming a reogramma serve as expression of those complex processes, to-rye provide manifestation of a variable of electric resistance in fabrics (see. Conductivity of biological systems ). Fluctuations of mass of blood in the studied site of a vascular bed cause corresponding changes of amplitude of reografichesky waves, and the condition of a vascular wall (its elasticity, a tone, elastoviscous properties, etc.) finds the reflection in changes of other indicators reogramm.
Researches make by means of reograf, to-rye for strengthening and record of signals are connected to electrocardiographs (see. Elektrokardiografiya ), to electroencephalographs (see. Elektroentsefalografiya ) and to other similar devices. On a body by means of rubber tapes, an adhesive plaster, bandage, etc. electrodes, the size and a form become stronger to-rykh is defined by area and research objectives. Special pastes are applied to reduction of resistance of skin and strengthening of contact. At the same time the ECG registers.
The analysis reogramm is made according to its amplitude and temporary indicators (fig. 1). In each reografichesky wave allocate the beginning, top and the end, and also ascending (anacrotic) and descending (catacrotic) speak rapidly. On the descending part 1 — 2 additional waves usually are observed. The regularity, a form, expressiveness and an arrangement of additional waves belong to external indicators. The curve is normal rather regular; changes of a regularity depend on disturbance of a rhythm of cordial reductions or breath. The regularity of reografichesky waves significantly changes at nek-ry types of pathology, napr, at the expressed vascular dystonia. The form of reografichesky waves depends, mainly, on a condition of a vascular wall. At it patol. changes the configuration of separate parts, tops of a reografichesky wave, a tilt angle of the ascending part, expressivenesses and locations of additional waves changes. Characteristic changes of a form of a reogramma are observed at pathology of venous system. For objective assessment of a state venous blood circulations (see) the method of division reogramm on arterial and venous components with use of extreme points of a curve and their comparison to a tangent of angle of an inclination of this curve is used (i.e. from the first derivative). From indicators of a reogramma and physiologically reasonable the following is the most informative: the reografichesky index (the relation of amplitude of a reografichesky wave to the size of a standard calibration index) characterizing the size of a pulse krovenapolneniye in the studied site of a vascular bed, time of the ascending part of a wave (the period of full disclosure of a vessel — and), reflecting a tonic condition of vessels, hl. obr. large; time of a bystry krovenapolneniye (a1) determined by the module of elasticity of walls of large vessels and sokratitelny function of a myocardium; time of a slow krovenapolneniye (a2) depending on elastoviscous properties of a vascular wall; the relation of time of the ascending part to duration of all wave (and: T), the reflecting tonic condition of vessels; dicrotic index (h2: h1 characterizing a tone of arterioles; diastolic index (h3: h1), reflecting a condition of outflow of blood in veins and a tone of veins; the transmission time of a wave (Q — and) characterizing a total condition of large vessels of an organism; coefficient of skewness. Absolute values of all these indicators are depending on area of a research and age of people (fig. 2).
Results of researches by method P. depend on the frequency of alternating current, on a cut measurements are taken. Theoretical and experimental works on justification of a method showed that the reogramma is most adequate to indicators of blood supply during the use of alternating current with frequencies of 30 — 300 kHz. For elimination of unpleasant feelings for the patient and changes of physiological indicators of the studied object (disturbances of structure, mechanical, chemical, nervous or any other processes of life activity) the size of current of high frequency shall not exceed threshold value. For the specified frequency range the size of current makes 1 — 5 ma.
A clinical use
In a wedge. to practice the greatest value was gained by R. of extremities (reovazografiya) and R. of a brain (rheoencephalography) giving an idea of a pulse krovenapolneniye and a state arterial and, to a lesser extent, a venous tone of vessels. Reogramma of extremities is used at diagnosis of diseases of the peripheral vessels which are followed by change of elasticity, narrowing or a full obliteration of arteries, measurement of a vascular tone and also during the studying of a pharmacodynamics of various pharmacological means.
For registration longitudinal reogramm various departments of extremities plate or annular electrodes impose on proximal and distal departments of a shoulder, forearm, brushes or fingers of a hand, hip, shins, foot or toes. Electrodes are chosen the identical area, 10 — 20 mm wide. Electrode separation, imposed on various sites of extremities, makes 100 — 150 mm; at R. of a finger elastic electrodes from a foil or the brass silvered rings with a slanting section and with an internal diameter from 15 to 24 mm at electrode separation of 10 — 15 mm are applied. Record is recommended to be carried out from symmetric sites of both extremities.
At quality standard reogramm the attention to a regularity of pulse waves, the steepness of rise and descent, character of top, expressiveness of an intsizura of the descending wave, existence and expressiveness of additional waves, symmetry of record on different extremities is paid. At quantification the following indicators are defined: amplitude of a reogramma reflects change of elasticity and elasticity of walls of arteries and their pulse krovenapolneniye, a cut depends also on the size of a stroke output of heart. The relation of amplitude of a reogramma to ohmic basic resistance gives more exact ideas of a pulse krovenapolneniye of various departments of extremities.
Amplitude of a reogramma is depending on the relation of volume of a pulse krovenapolneniye to total amount of the studied department of an extremity therefore amplitude of a reogramma of a hip is less than amplitude of a reogramma of a shin and toes. At healthy faces amplitude reog-grams on average makes for a shoulder 0,05 ohms, for a forearm of 0,08 ohms, for a brush of 0,1 ohms, for a finger of 0,24 ohms; for a hip of 0,035 ohms, for a shin of 0,08 ohms, for foot of 0,1 ohms, for toes of 0,22 ohms.
The rise time of a reografichesky wave (a) is measured from the beginning of a wave to the basis of the perpendicular lowered from a point of the maximum rise. It characterizes ability of arteries of large and average caliber to stretching. Normal and 0,08 — 0,13 sec. make.
The dicrotic index of the relation of amplitude at the level of an intsizura of the descending wave to the maximum amplitude of the main wave of a reogramma reflects a condition of a tone of arteries of preferential small and average caliber and averages 50%.
Reografichesky coefficient (a*100%/T where the T — duration of middle ring) reflects a condition of a tone of arteries and normal averages 10 — 13%.
Reogramma of healthy faces is characterized by the main systolic wave with the steep slope pointed by top, flat descent, on Krom there are two-three additional waves, well-marked intsizury. The differential reogramma (i.e. the first derivative of the main reogramma) characterizes the speed of inflow and outflow of the studied area (ohms/sec).
Increase in rigidity (decrease in elasticity) of arteries caused by increase in a tone or organic changes of walls of arteries is followed by reduction of amplitude, lengthening of a rise time (a), increase in reografichesky coefficient, a curve of top of a curve, shift of a dicrotic wave to top, a smoothness of a curve owing to disappearance of diastolic waves.
From organic and clarifications of compensatory opportunities of vascular system are applied to differentiation of functional changes functional trials:
test with nitroglycerine (fig. 3). The patient accepts 0,5 — 1 tab. of nitroglycerine; in the absence of organic changes of arteries amplitude of a reogramma increases by 1,5 — 1,8 times, decreases and and the dicrotic index (positive test) decreases;
postural test consists in registration of a reogramma of shins and feet in situation: a) with the raised extremities at an angle 45 ° and b) with the shins lowered at an angle 90 °. At healthy faces in situation with the raised legs increase in amplitude of a systolic wave, and with the lowered legs — its reduction is noted;
test with a local exercise stress — bending, extension in an ankle or radiocarpal joint within 1 min.: at a disease of an artery amplitude of reografichesky coefficient does not change or decreases, and duration and increases by 30 — 60% (negative test);
test on reactive a post an ischemic hyperemia: at healthy faces after the two-minute ischemia created by pressure exceeding systolic in a cuff, the imposed use-simalnee of the explored area, amplitude of reografichesky coefficient increases in 1,0 — 1,5 min. by 30 — 40%;
cold test: normal after cooling of a brush within 1 — 2 minutes with water at a temperature of 5 — 8 ° amplitude of a reografichesky wave decreases slightly with return to initial in 6 — 8 min.
At diagnostic use of R. for the patient with suspicion on a Raynaud's disease (see. Reynaud disease ) in an initial stage signs of the raised tone of arteries of hands are noted; test with nitroglycerine is positive, and cold — is sharply negative (initial level of amplitude of a reografichesky wave is recovered only in 15 min.).
At an obliterating endarteritis (see. obliterating endarteritis ) in an initial stage of a disease on a reogramma of feet the changes characteristic of vascular dystonia are observed; nitroglyceric test is positive, postural and test on a reactive hyperemia are often negative. During the progressing of a disease of change of a reogramma become more expressed and are found also on reogramma of shins.
At obliterating atherosclerosis (see) in initial stages on reogramma of shins additional waves are expressed poorly at preservation of normal amplitude of a systolic wave, angle of lead and the pointed top. Postural test is often negative at positive nitroglyceric test. In process of increase in disease severity decrease in amplitude of the main and differential reogramm shins and feet (fig. 4) is noted. At a full obliteration of large arteries of a reogramma get an arc-shaped form — collateral type of a curve. Nitroglyceric test reveals the hidden opportunities of collateral circulation (see. Collaterals vascular ).
Reografy are the electronic devices intended for transformation of fluctuations of an impedance of living tissue (see. Impedance ) or its components caused by pulse changes of a krovenapolneniye in a proportional electric signal. The analysis of this signal is carried out visually at record on the chart recorder (most often the electrocardiograph) or automatic computers. On number of channels reograf are subdivided on single-channel and multichannel.
The principle of work of a reograf consists in the following: from the generator of high frequency of a reograf by means of electrodes through the studied body current of high frequency is passed. At the same time on the explored site (body) there is a power failure. Changes of a krovenapolneniye in the studied body lead to changes of its impedance and proportional changes of amplitude of high-frequency tension. After strengthening by means of the detector and filters the low-frequency component representing a reografichesky signal (reogramma) is allocated.
Depending on quantity of the electrodes used in each channel distinguish two-electrode (biopolar) and four-electrode (tetrapolar) reograf. In turn two-electrode reograf depending on the scheme of transformation of change of an impedance to an electric signal are subdivided on electrometric and bridge. Besides, it is developed and even more often the so-called method focusing reografsht began to be applied.
The greatest distribution was gained by bridge schemes (fig. 5). On the explored site 2 electrodes providing a transmission of electric current through this site are imposed. By means of conductors the explored site joins in the bridge scheme formed by the elements R1, R2, Re, SE. At balance of the bridge that takes place at equality of resistance of R1 and R2 and also equality of an impedance of the explored site (a shoulder and — d of the bridge) to an impedance of a chain of Re, SE (a shoulder of d — from the bridge), tension at the exit of the bridge is equal to zero. Changes of an impedance of the explored site lead to disturbance of balance of the bridge and emergence at the exit of the bridge (a point of b — d) of high-frequency tension, amplitude to-rogo changes in proportion to changes of an impedance. Further transformation of tension is carried out in strengthening of an output signal and filtering out of a low-frequency component. Balancing of the bridge is made usually smoothly by adjustment of resistance of Re and is discrete (by means of the switch) connection of condensers of various capacity.
Calibration of a reogramma in terms of the measured size — ohms is made for quality standard of results of a research. Nearly amplitude of a reogramma is very small and the sizes of calibration used in practice have standard values 0,05; 0,1 and 0,2 ohms.
Common fault of bipolar reograf is that the measuring scheme of a reograf joins not only an impedance of the studied body, but also transfer resistances between an electrode and internal fabrics: resistance of transition an electrode — paste, paste — skin, skin — internal fabrics. It leads to the fact that the impedance measured by a reograf, actually above, than an impedance of actually studied body and consequently, during the calculations of quantitative indices of a krovenapolneniye the mistake takes place, to-ruyu difficult to consider.
Development of methods of quantitative R. led to development and widespread introduction in clinical practice of tetrapolar four-electrode reograf. In them current of high frequency moves through the electrodes located near the explored site. By means of two other electrodes located at the edges of the explored site high-frequency stress is removed, amplitude to-rogo changes in proportion to changes of an impedance between these electrodes. At the big entrance resistance of the amplifier of high frequency tension of high frequency which is formed on internal structures of the explored site completely arrives on its entrance. Power failure on transitions internal fabrics — electrodes is insignificant a little and therefore on the scheme of a reograf tension proportional to an impendans of internal fabrics arrives. Increase in accuracy of measurement of an impedance of internal fabrics and consequently, and increase in accuracy of a research of a krovenapolneniye on the site limited to electrodes are the most important and basic advantage tetrapolyarno-go a four-electrode reograf.
The most widespread in the USSR is the reopletizmograf of RPG — 202. It has 2 measuring channels executed according to the four-electrode scheme of measurement, provides quantitative measurement of shock and minute volumes of blood circulation, pulse volume of a krovenapolneniye etc. Reograf is intended for record reogramm on ELKAR electrocardiographs, registrars of type N — 338 or the analysis by automatic computers.
Reograf has one general generator of high frequency with a frequency of 40 kHz creating stable current with a force of 2 ma. Both measuring channels are executed according to the uniform scheme and provide the following indicators at their exits:
— its first derivative (differential reogramma);
— slow component of an impedance.
Reograf has calibration of all output tension: channels of a reogramma of 0,1 and 0,5 ohms, channels of a differential reogramma of 1 and 5 ohms/sec. Calibration is carried out from the built-in generator of sinusoidal fluctuations with a frequency of 1,59 Hz. Measurement of a basic impedance is carried out by the arrow measuring device in the range of 10 — 100 ohms with a margin error no more than ±5%. Reopletizmograf is executed in the case having dimensions 106 X 238 X 304 mm, weight it no more than 5 kg.
Bibliography: Bolshov V. M. and Tsvetkov A. A. Reopletizmograf of RPG-202, Medical equipment, No. 3, page 49, 1978; M and t in e y to about in G. of the Item and P sh about N and to S. S. Clinical reografiya, Minsk, 1976, bibliogr.; Mintz A. Ya. both P about the Tax Code and N M. A. Reograficheskaya diagnosis of vascular diseases of a brain, Kiev, 1967, bibliogr.; With and in in and t e - ev K. L. and the Gunner Yu. T. Izucheniye of a pharmacodynamics of drugs of nitroglycerine by methods of a tetrapolar reo-pletizmografiya of a finger and an impedance cardiography at patients with coronary heart disease, Cardiology, t. 20, No. 12, page 89, 1980; E N and N I am G. I. Reografiya as a method of assessment of cerebral circulation, Riga, 1973, bibliogr.; Yarullin X. X. Clinical rheoencephalography, L., 1967; Jenkner F. L. Rheoencephalography, Springfield, 1962; Kaindl F., PolzerK. u. Schuhf-ri ed F. Rheographie, Darmstadt, 1959
M. A. Ronkin; Yu. T. Pushkar (wedge, use), V. M. Bolshov (tekhn.).