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diathermy(dī`əthûr'mē), therapeutic measure used in medicine to generate heat in the body tissues. Electrodes and other instruments are used to transmit electric current to surface structures, thereby increasing the local blood circulation and facilitating and accelerating the process of absorption and repair. Diathermy is used for arthritis, bursitis, and other disorders of the tendons and muscles, as well as for certain other conditions requiring tissue repair. Because of the high-frequency current used in shortwave diathermy, care must be taken to avoid burning the patient's skin or injuring the deeper tissues.
(also endothermy, thermopenetration), one of the methods of electrotherapy that involves heating organs and tissues of the organism with high-frequency currents. The method was introduced into medical practice in 1905 by the Czech doctor R. von Zeynek. The term “diathermy” was proposed by the German doctor K. F. Nagelschmidt, who was working on the method at the same time. A strong current (up to 3 A) of high frequency (1.65 MHz) is used for diathermy.
The amount of heat created in the organism is proportional to the square of the strength of the current passing through the conductor (tissues of the organism), the electrical resistance of the tissues, and the duration of the current. Therefore, a current of great strength is required if intensive heating of the tissues is needed. However, a strong direct or low-frequency current irritates sensitive nerves (sensations of pain). By increasing the frequency the irritating action of a strong current is reduced and practically disappears at a current of 3 A and a frequency of 1 MHz. The body’s tissues and organs do not have the same electrical conductivity. Because the skin, fat, bones, and muscles have the greatest resistance, they heat up the most, while organs rich in blood or lymph, such as the lungs, liver, and lymph nodes, have the least resistance and heat up less.
High-frequency currents cause nonthermal (that is, specific) processes in the organism, the nature of which has not been clarified. It is hypothesized that the current causes the cell ions to shift to the borders of the cells. When a certain maximum concentration of ions is along the borders, the cell’s colloids precipitate out, and the cell passes to an excited state. The specific processes are more evident at a comparatively lower current frequency; at greater frequency, the thermal effect is more strongly marked. The action of diathermy is manifested in physiological reactions. The activity of the autonomous nervous system increases, which is expressed in intensified lymph and blood circulation and increased metabolism (in this case the body temperature may rise by 0.1°-0.2°C). Leucocyte activity also increases, especially in the area subjected to diathermy. The skeletal muscles and muscles of the internal organs relax, and the threshold of excitation of the sensory nerves increases. Therefore diathermy is used in the treatment of diseases based on spasms of the blood vessels, the urinary tract, the bile ducts, the gall bladder and other cavity organs as well as for chronic nonpurulent inflammatory diseases, inflammations of the nerves and their roots, neuralgias, and muscle, joint, and other pains.
REFERENCESObrosov, A. N. Fizioterapevticheskaia tekhnika. Moscow, 1945.
Kowarschik, J. Diatermiia. Moscow-Leningrad, 1931. (Translated from German.)
Liventsev, N. M. Elektromeditsinskaia apparatura, 3rd ed. Moscow, 1964.
Rukovodstvo po fizioterapii i fizioprofilaktike detskikh zabolevanii. Edited by A. N. Obrosov and K. V. Lapina. Moscow, 1968.
V. G. IASNOGORODSKII