Eberhart's Manual of High Frequency
Noble M. Eberhart
Characteristics and Synonyms. As Long ago
as 1899, Prof. D'Arsonval noticed that passing the D'Arsonval current through
certain tissues of the body produced a higher temperature in these tissues.
Nagelschmidt, Doyon and others confirmed these early observations, and
the name diathermy was applied to this method of increasing the
temperature of the internal tissues of the body.
The direct D'Arsonval current is used and diathermy
is synonymous also with the terms thermo-penetration, electro-coagulation
and electro-thermic coagulation. The application is always bi-polar.
It really amounts to the application of electrically
generated heat, which may be made to cover certain definite areas between
the poles of the apparatus, and may be used to raise the temperature of
the tissues or even carried to the point of coagulation with the formation
and separation of a slough. In the latter case it is the equivalent of
a surgical procedure.
We are familiar with the action of the galvanic
current. If we pass this current through water, owing to electrolysis,
the water is decomposed into hydrogen and oxygen which collect at the positive
and negative poles respectively, or, if the current is passed through a
solution of potassium iodide and starch, a dark color is immediately noticed
at the negative pole, due to the decomposition of the potassium iodide
and consequent action of the iodine on the starch solution. If we dip our
hand into the water while the current is passing, there is a distinct tingling
If, now, instead of using the galvanic current,
we pass the direct D'Arsonval current through the water or solution, no
electrolytic action is apparent and the only effect is an increase of temperature
in the solution, as is evidenced by the introduction of a thermometer which
shows the steady rise in temperature until the water boils. It is estimated
that with the diathermic current the internal temperature of the body,
located between the points of application can be raised to a temperature
of 110 to 140 degrees Fahrenheit, though many believe 110 degrees to be
about the limit of skin and tissue resistance.
Effects. On account of there being practically
no skin resistance to the passage of the diathermic current, the current
passes directly from one electrode to the other, heating the tissues that
lie between the electrodes. The current can be concentrated in this manner,
and is always under absolute control. This is of great value, as a little
experience will enable the operator to gauge the amount of current required
to produce any given temperature in the tissues and reduces the application
of this current to exact measurement, so difficult to obtain when applying
an ordinary high frequency current.
If electrodes of the same amount of surface are
used on the opposite sides of a part, the same effect would be produced
at each electrode or a uniform effect produced between the two, making
allowance for the fact that fatty tissues heat quickly and that bones are
slow to heat, but retain their heat longer, while muscular tissues are
slower to heat than either fat or bones.
If we decrease the size of one electrode, since
the same amount of current is passing, there will be a more intense heat
over the area of the smaller electrode. If sufficient current is used the
heat acts like the cautery, coagulating and destroying the tissue.
By regulating the size of the electrodes the heat
may be delivered wherever desired within the tissues, thus the value of
this current in all inflammatory conditions of joints, etc.
When the cauterizing effect is desired, the active
electrode is usually a metal point or a wire. In this form it represents
one form of fulguration. It is employed in papilloma of the bladder. (The
technique is given under this heading in Chapter VI.)
Diathermic currents are measured with the hot wire
Range of Usefulness. Outside of their use
in one form of fulguration as above referred to, they nave been very successfully
used in connection with deep Roentgen therapy in malignant growths, and
in the form of increased heat without carrying it to tissue coagulation,
in arteriosclerosis, local or peripheral disturbances, sciatica, neuralgia,
lumbago, asthma neuritis, headaches and rheumatic or other forms of arthritis.
Many other conditions naturally suggest themselves where these currents
may be employed.
Techniques. For increased internal heat,
the method of the use of this current is as follows: Connecting cords are
attached to electrode of suitable size or shape for the part that is to
be treated. These electrodes are made either of solid discs, or a thin
brass sheet covered with absorbent material. In order to make better contact
they are first covered with gauze saturated with a normal salt solution,
and the part to be treated is also moistened with this solution,. The control
of the current is easily maintained by using a meter and the exact amount
that is applied can be measured at all times. In general treatment, the
current is slowly turned on until the meter shows from 700 to 800 milliamperes
passing, and then it is gradually increased up to the tolerance of the
patient. The operator should remember that it is better to commence with
a small current and gradually and uniformly heat the part between the electrodes
rather than to start with a heavier current where the greatest effect is
nearer the two electrodes, for if too much current is used, the tissues
near the electrodes will be heated beyond the pont of tolerance before
the tissues that lie deeply are heated as much as they should be, and burns
will be produced.
Fig. 64b - A New Electrode for Modified Diathermy.
In the second method, where coagulation and cauterization
are desired, the active electrode must be metallic, and if extensive work
is to be done anaesthesia is required.
Fig. 64c - Diathermy Electrodes.
Dr. G. E. Pfahler (Journal Advanced Therapeutics,
Dec., 1914) has accomplished remarkable results by combining this method
with deep Roentgen therapy in malignant growths. The work is done under
an anaesthetic, as the pain is severe. In most of his cases ether was employed,
but in mouth cases hypodermic injections of one or one and a half HMC tablets
(hyoseine hydrobromide gr. 1/100; morphine hydrobromide gr. 1; and cactoid
gr. 1/64) were used. These in some cases had to be supplemented by ether.
He uses an instrument capable of generating 1,000
to 2,000 milliamperes. In removing a portion of a lip he uses a ball electrode
inside, about three-eights of an inch in diameter, and a needle-point electrode
externally. He says; "I would outline the area of the diseased tissue to
be removed by allowing the current to flow from this point toward the ball
electrode on the inside, and then coagulate the entire diseased tissue.
At first I depended upon the needle electrode to actually carve out the
diseased tissues, but now I find it simpler to cut this away with a pair
of curved scissors after coagulation, always cutting within the coagulated
tissues. In this way there is no bleeding and the edges are completedly
"In destroying an extensive lesion in the cheek
I used a flat electrode, one inch in diameter, on the inside and a point
electrode on the outside. In destroying a portion of the tongue I have
used two point electrodes. The electrodes are held in contact with the