Physical bases of rheography

Biological objects are characterized active and jet resistance. Total resistance of objects is called impedance. Tissues of an organism spend not only constant, but also an alternating current. In an organism there are no such systems which would be similar to coils of inductance; therefore its inductance is close to zero. Biological membranes and, hence, all organism possess capacitor properties, the impedance of tissues of an organism is defined only ohmic and capacitor resistance. Ohmic and capacitor properties of biological tissues can be modeled, using equivalent electric schemes. We shall consider some of them. For the scheme represented on fig. and, frequency dependence of impedance at

L = 0:

The equivalent electric schemes (fig. a, b) have a divergence with experience. Biochemical fabrics have resistance at greater frequencies. The equivalent electric scheme, combining first two model (fig. c) is most successful. Frequency dependence of impedance allows estimating viability of tissues of an organism that it is important to know for change (transplantation) tissues and bodies. In a dead tissues of a membrane desolate and the tissues possesses only ohmic resistance. Distinction in frequency dependences impedance turns out and in cases of healthy and sick tissues.

The impedance of tissues and bodies depends upon them physiologic conditions. The impedance changes depending on a condition of cardiovascular activity at filling of blood vessels.

The diagnostic method based on registration of change of an impedance of fabrics during intimate activity, is called rheography (impedance- plethysmography).

By means of this method rheogram of a brain (rheoencephalography), hearts (rheocardiogram), the main vessels, lungs, a liver and extremities turn out. Measurements are usually are made on frequency 30 KHz.

Rheography is applied in diagnostics of a various vascular infringements of a brain, extremities, lungs, hearts, and a liver. Rheography of extremities is used at diseases of the peripheral vessels, accompanied by changes of their tone, elasticity, narrowing or full corking of arteries. Record rheogram is made from both symmetric sites of extremities, on which electrodes are imposed with identical area and width is equal to 1020 mm.

Rheoencephalography (REG) defines a tone and elasticity of vessels of a brain, measuring their resistance to a current of high frequency at small values of force of a current and voltage. It allows to define also filling of parts of a brain by blood, to diagnose character and localization of its defeats, gives good result at vascular diseases, especially at a cerebral atherosclerosis. In the sharp period of an insult it helps to establish ischemic character of frustration of blood circulation or inopectic cerebellar infarction. Rheoencephalography is perspective at traumas of a brain, its tumours, epilepsy, and migraines.

Opportunities of rheograph "Credo":

- Rheoencephalography, rheogram of the upper extremities and lower extremities, automatic measurement of parameters of wave and calculation rheographic indexes.

- Delivery on the screen or the printer of results of analysis REG in a text kind in view of age of the patient, the preliminary diagnosis and results of previous inspections.

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