ELECTROTHERAPY, a general term for the use of elec tricity in the alleviation and cure of disease. Many claims have been made for it in the past which could not be justified, or at best were psychological. Of recent years its sphere has been better defined and at present four different types of electricity are em ployed in medicine:— 0) The constant, continuous, or galvanic current.
(2) The interrupted currents of low frequency (the interrupted galvanic current, the alternating and sinusoidal currents, the faradic current).
(3) The interrupted currents of high frequency (high fre quency currents and diathermy).
(4) The high voltage unidirectional currents derived from the static machine.
The Constant Current.—It is now generally accepted that the chief curative action of the constant current is due to the reflex action resulting from the stimulation of the cutaneous and sub cutaneous nerves immediately beneath the area over which the pads conveying the current are applied. By this reflex stimulation an increased blood supply, with its valuable consecutive effects, is obtained. This stimulation is very similar in nature to what has been termed "counter-irritation," with the great advantages that the amount of stimulation is capable of exact regulation, that it takes place within the epidermis, thus acting directly on the nerve endings, and that it can be continued daily for a long period, im proving the condition of the skin rather than destroying it, as the constant painting on of an irritant would do. The extent of this stimulation is dependent on the strength and duration of the cur rent employed and the nature of the solutions with which the con ducting pads are moistened.
When a positive pole of zinc or copper, or when salts of these metals in solution are employed, a caustic and destructive com pound such as the chlorides or oxychlorides of zinc or copper is formed in the submucous or subcutaneous area by the combina tion of the negatively charged atoms of zinc (zinc ions), proceed ing from the positive pole to the tissues, with the positively charged chlorine atoms (chlorine ions) proceeding from the tissues toward the positive pole. In the process of combination the atoms get rid of their electrical charges, the process is there fore rather one of de-ionisation. This method is very valuable for the thorough and safe destruction of the diseased membranes of cavities, such as the unhealthy mucous membrane of the uterus or the lining of septic cavities.
Similarly, by the employment of less destructive solutions, a reflex stimulation of the tissues can be brought about. The amount of stimulation depends on (1) the nature of the solution; (2) the strength and duration of the current. In general the best results are obtained by a solution causing the minimum of irritation and the application of the maximum current which can be readily tolerated by the patient for at least 4o minutes.
This form of treatment is indicated when increased local nu trition or the re-absorption of fibrotic thickening is desired : such as in the local treatment of chronic rheumatics, neuritis, sprains, and many other conditions. It is especially valuable in the treat ment of tic douloureux, for which the employment of strong cur rents of from 40 to 8o milliamperes is necessary.
Interrupted Currents of Low Frequency.—The therapeutic effects obtainable from the employment of the interrupted cur rents of low frequency have been greatly increased by the methods recently introduced by Prof. Lapicque, Prof. Leduc, and Dr. Mor ton Smart. In the method of Lapicque, by the interposition in parallel of condensers with capacities varying from 2 to 3o micro farads, an interrupted current of such progressive onset and decline is obtained that it will excite contractions in paralysed muscles without exciting corresponding or over-powering contractions in the neighbouring healthy muscles due to the physiological fact that the contraction excited in a paralysed muscle is less dependent on a sharp make and break than with a healthy muscle.
In the treatment of infantile paralysis objection has been raised to the electrical excitation of the paralysed muscles on account of the over-excitation of the opposing healthy muscles which accom panies such stimulation. By the method of Lapicque this objec tion is entirely overcome. The defined and isolated contraction elicited by this method has a valuable re-educative effect in cases of recovering motor-nerve lesions. Lapicque's technique is espe cially useful in the treatment of facial palsy.
The Leduc current consists in the interruption at a frequency of about ioo per sec. of the galvanic current at the very low intensity of from two to four milliamperes. Leduc claims that it is possible by employing these minute currents interrupted at such frequency to induce successively local anaesthesia and, if applied through the brain, general anaesthesia, electric sleep, coma, and eventually death. Applied locally, avoiding the region of the brain, this treatment is perfectly safe and has proved valuable in the treatment of certain forms of neuritis and especially in that other wise intractable condition, causalgia.
The advantages of the instrument and technique elaborated by Dr. Morton Smart for the application of faradism to muscles de ficient in excitability and tone, which have very greatly enhanced the therapeutic value of the faradic current, are that the pain of the treatment is abolished or reduced to a minimum, the vigour and amplitude of the contractions are increased ; and, above all, when employing this method, the operator can at once appreciate when the muscles are becoming fatigued and so can at once dis continue further stimulation before any of the bad effects, which were liable to occur when employing the older methods, can take place.
High Frequency Currents and Diathermy.—Although the researches of D'Arsonval which led to his discovery of the high frequency currents and diathermy were commenced in 1888 and concluded in 18go, diathermy (the most valuable result of his research) only began to be employed in Great Britain in 1911 or 1912. D'Arsonval, when experimenting with alternating currents in 1888, noticed that, with a constant strength of current, the more rapidly the interruptions occurred the more vigorous were the resulting muscular contractions.
When, however, a frequency of from 2,50o to 5,oOO excitations a second was reached, a decrease in the vigour of the contractions occurred and progressively decreased with the increased frequency of excitation. At this time, the instruments at D'Arsonval's dis posal did not permit a further increase of frequency, but in 18g0, by employing the wireless apparatus of Hertz, he obtained what he rather exaggeratingly termed "billions of oscillations a second." With these frequencies he found that he was able to pass a current of two or three amperes through the human body without pro ducing any muscular contraction or other sensation than that of heat. He thus obtained the clinical high frequency currents. Dia thermic currents were subsequently evolved from the high fre quency currents by such modifications in the instruments as per mitted currents of lower voltage, higher amperage, and higher frequency to be obtained.
The main therapeutic effect of diathermy is the generation of heat deeply in the tissues by the friction from the oscillation of the electrically charged atoms. Any organ of the body, any limb or part of the body, or the whole body to any extent required, can be heated by this current. Before the advent of diathermy we were able to heat only the superficies or the accessible cavities of the body ; even under such limitations the application of heat formed one of the oldest and most useful therapeutic measures. Moreover, the heat obtainable from diathermy admits of exact and easily regulated adjustment to a degree never before ob tainable.
The consecutive effects of heat applied in this manner are an increased blood supply, relaxation of tension and spasm with con sequent relief of pain, increased local drainage, increased local nutrition. The heat thus generated is an expression of the mechan ical or dynamic force exercised by the oscillations of the ions within the tissues and this primary action (the so-called "ionic massage") appears to be of value in aiding the dispersal of recent effusions. Some of the main indications for the application of diathermy are the relief of pain and spasm, the treatment of rheumatism, neuritis, sciatica, asthma, and pneumonia.
Diathermy in Surgery.—Apart from its medical application, diathermy is of considerable value in surgical practice for the destruction of superficial morbid growths, such as rodent ulcers, warts, naevi, etc. When applied for this purpose, in place of the two electrodes of large size employed in medical diathermy, one large (the indifferent electrode) and one small metal point (the active electrode) are substituted. In this way the heat, which is distributed and is only appreciated as a slight warmth over the large pad, is concentrated at the small metal point and almost immediately coagulates and destroys the tissue with which the point is brought in contact. Very satisfactory results have been obtained from the treatment of haemorrhoids in this manner.
The point of a metal wire can be employed as the active elec trode and by inserting this wire through, e.g., a cystoscope (an instrument for viewing the interior of the bladder) small growths can be readily destroyed and serious surgical operations avoided.