Eberhart's Manual of High Frequency Currents
Noble M. Eberhart
Chapter Five
Physiological Action of High Frequency Currents; Burns; Offsetting Tendency to X-Ray Burns.
   The physiological action of high frequency varies with the form employed.
   In the construction of the apparatus the coarse coil or solenoid of the D’Arsonval machine is used as the primary coil of the Oudin resonator, and the current from the secondary of the Tesla coil is essentially the same as that from the secondary of the resonator.
   If a vacuum tube is excited by attaching to one pole of the Tesla secondary it gives the same effect as if coming from the top of the Oudin resonator.
   With the hyper-static transformer the primary yields a D’Arsonval current and the secondary one similar to that of the resonator or Tesla secondary.
   When vacuum tubes are applied locally there is soon produced redness and hyperemia, with all of the resultant benefits on nutrition.
   In short, the fundamental value of high frequency currents is their beneficial effect on all nutritive processes.  Incidental to this we have increased oxygenation of blood and tissues, increased leucocytosis (and Phagocytosis); and increased elimination.
   There is no painful sensation produced by the vacuum tube when held firmly in the hand, thus establishing complete electrical contact.  Ordinarily there is a sensation of heat and in some instances perceptible vibration.  Removing the tube produces a spark which increases in sharpness as the tube is drawn away, up to the full length spark it is capable of emitting.  The longest spark which may be drawn from the tube has been my method of roughly calculating the strength of the current and the regulation of the dosage.  See Chapter VI.
   General Action of Vacuum Electrode.  In a general way the action of the current when applied by means of the glass vacuum electrode is as follows:  A mild current with tube in contact is sedative.  As the current is increased, or the electrode removed from the surface, allowing a spark to pass, it becomes first mildly stimulating, then strongly stimulating and finally caustic or destructive.  The whole gradation of effect from sedation to cauterization being essentially a question of current intensity and length or sharpness of spark.
   With this is the effect of hyperemia and the germicidal action of the spark and the ozone which it liberates.
   Summary of Vacuum Tube Effects, from Oudin resonator or Tesla secondary:
1.  Increase blood-supply to a given area.. (Hyperemia.)
2.  Increase oxidization and local nutrition.
3.  Increase intake of oxygen.
5.  Increase output of carbon dioxide.
6.  Increase secretions.
7.  Increase elimination of waste products.
8.  Liberate ozone, with the resultant benefit of more or less of this ozone being inhaled by the patient, and also probably carried directly into the tissues.
9.  Increase bodily heat, without a corresponding rise in temperature.
10.  Locally germicidal.
11.  Mild and medium sparks stimulate or soothe according to length and character of application.
12.  Strong sparks are caustic.
13.  Sparks to spine increase arterial tension.
14.  Promote absorption of plastic exudates or adhesions.
   These effects of vacuum tube applications, while essentially local, are not absolutely so.  The current traverses the body in all directions from the point of entry, but is, of course, most intense and pronounced at the latter point.  Prolonged applications of vacuum tubes will give systemic effects, but these are obtained more easily by auto-condensation.
   Constitutional Effects.  These are derived through auto-condensation and auto-conduction.   These currents increase bodily heat, almost always showing a rise of from one-half to one and a half degrees in temperature during a ten-minute application.
   Some attribute the effect of these currents to the heat they develop in the tissues.  In my opinion their principal effects are due to “cellular massage.”  They have, therefore, a great effect upon metabolism.
   The effect of auto-condensation in producing cellular massage is appreciated when we realize that the charge in the patients’s body must return back into the circuit and then alternate with one of opposite polarity; thus, first a positive and then a negative charge is carried into the body and back again.   This produces a to-and-fro wave that acts upon every cell in the organism.  No sensation is usually perceptible if perfect electrical contact with the patient exists in the latter’s circuit.
   Synopsis of Constitutional Effects:
1.  Increase general metabolism.
2.  Increase glandular activity.
3.  Increase temperature and bodily heat.
4.  Increase oxidization and hemoglobin.
5.  Increase secretions.
6.  Increase elimination.
7.  Lower blood-pressure when hypertension exists.
8.  Soothing to the nervous system.
   High Frequency Burns.  This is a subject which has not been touched upon in the literature on high frequency.  There is a prevalent idea among many operators that these currents do not and cannot produce a burn.  True, they do not cause a dermatitis, comparable to that produced by the X-ray, but they are still capable of causing annoying surface burns.
   It will be noted by the physician who is accustomed to handling the excited tube with his hands that after a time the skin, especially about the finger tips, feels as if he had been handling a hot dish, that had seared the outer skin.  Also in giving vaginal treatments, prolonged application may result in shreds of the mucous membrane adhering to the tube when it is withdrawn.
Fig. 28 - Formalin Sterilizer.

  To avoid this, I make it a rule never to leave a vacuum tube in contact with a mucous membrane for more than seven minutes at a time.  Occasionally the urgency of a case is such that I am willing to give longer treatments and take the chance of a possible burn.
   High frequency currents seem to have no cumulative effect in so far as burning is concerned, and treatment may be repeated frequently without any apparent danger; thus, three seven-minute treatments may be given in one day with intervals of three to six hours between, without any serious consequence when one twenty-minute treatment may be disastrous.
   High frequency burns appear immediately; there is no interval as with the X-ray.  Another use of the high frequency in which burns may result is in the application of the spark to a mucous membrane, as for instance, to the lip, where care and judgment must be used.
   I have seen a fairly sharp application to a “cold sore” result in the formation of a large vesicle which ruptured and poured forth an incredible amount of serum and was three weeks in healing.
   As a sharp spark has a cauterizing effect and is used for that purpose, it is readily inferred that the reaction just referred to is of this nature, as even a comparatively mild spark will influence a mucous membrane.
   Another condition in which these currents must be used with care is about the neck or scalp, where there is a fine, fuzzy growth of hair, as with some forms of apparatus having considerable amperage, enough current comes through to produce a spark capable of setting fire to any inflammable substance.
   This property of the high frequency spark may be easily demonstrated by lighting a gas jet with it.  I have been told of one or two instances where severe burns occurred from the spreading of the tiny flame to the hair on the head.
   I wish to specially caution against the danger of using the high frequency spark on the scalp in connection with lotions containing a high per cent of alcohol or other readily inflammable material.  Where such lotions are employed, the high frequency spark must be used first and the lotion applied thereafter, or a serious accident may happen.
   The same point must be kept in mind when using the cataphoric electrode.
   Offsetting Tendency to X-Ray Burns.  While I am touching on the subject of burns I wish to call attention to a use which I have made of the high frequency current, regarding which I have seen no reference elsewhere.  This is the use of this current to offset some of the effects of the X-ray, and by its use in conjunction with the latter, to enable a larger dose of the X-ray to be administered without a corresponding degree of danger.  A stimulating application is used to the point of producing some reddening of the skin.
   The ultimate action of the application of the X-ray is to cause a decreased amount of blood in the part treated through the action of the ray in increasing the cellular lining of the arterioles and thereby producing a diminution in their caliber.  It is well known that in deep X-ray burns we have a condition of starvation and death of tissues, resulting from insufficient nourishment.  Now, as far as the action of the high frequency current on the vessels is concerned it is diametrically opposite.  It increases the blood-supply to the part treated, and to this extent it tends to offset the anemia produced by the X-ray.  Otherwise the two methods usually act in harmony with one another in a large number of diseases, particularly those affecting the skin, and by combining the two, a greater amount of X-ray may be safely used, while its action is hastened by the complementary effect of the high frequency current.

Fig. 28a - Portable Outfit.

   This must not confound the reader with the action of strong sparks, which, as in fulguration, destroy arterioles, or produce an endarteritis similar to that caused by the X-ray.