EARLY ELECTROTHERAPY DEVICES
BERNHARD RUDERT BSc Electr Eng
RUDERT TECHNOLOGIES LTD
INTRODUCTION
Electrotherapy was extensively used in the first half of the 20th century with the intent to
cure all kinds of ailments. While this
approach benefitted skin care, hair loss
and pain, manufacturers exploited this fact
by claiming that their equipment cound
practically cure anyything. Eventually the
authorities intervened and stopped this
exaggeration, with the result that this kind
of therapy gradually got classified as
quackery, while the medical profession
increasingly relied on the prescription of
pharmaceutical
products.
Early
electrotherapy
devices
and
their
derivatives are still used in beauty spas
and by other firm believers in their
therapeutic benefits.
An example of a historic hand held device can be seen in Fig.1. To date there exists no
scientific or technical anlysis of the operation and benefits of this type of equipment, which
is the reason for the many weird unsubstantiated claims regarding its functionality or
efficacy. It is the intention of this paper to disperse some of these claims and show that the
operating principle employed is actually very much supported by today’s understanding of
electrical stimulation of the physical body. It will also emerge that early electrotherapy
devices are in fact another form of today’s frequently used Transcutaneous Electrical Nerve
Stimulators, or TENS devices. The subject matter is viewed from a technical perspective
relating to the equipment itself with pointers to ptential biological or medical benefits.
THE ELECTRICAL OPERATING PRINCIPLE
A basic understanding of the operating principle of the devices
is essential in order to make sense of the subsequent content.
Fig.2 shows the simplified electrical circuit of an early
electrotherapy
device.
The
capacitor “C” is charged by the
electrical current source “I” until
the energy stored in it reaches a
predetermined value while switch
“S” is in the position shown.
Thereafter switch “S” is activated
and connects capacitor “C” across
the primary winding of the transformer “T” until all the energy
is dissipated. Capacitor “C” together with the inductance of the
transformer “T”, form a partially damped oscillating circuit with
a characteristic frequency usually well above 100 KHz. The resulting ringing voltage dies
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down to zero after a few cycles and then switch “S” returns to the original position. The
process is repeated about every 10ms or 100 times per second, which means that at the
output of transformer “T” there appear very short bursts of high voltage peaks separated by
long periods of inactivity as shown in Fig.3. The bottom part of Fig.3 shows the short high
voltage peaks just as straight lines because the peaks are extremely short. The top part of
Fig.3 shows a time magnification of these pulses where the damped oscillation of the high
voltage can be seen. The devices usually have means of controlling the energy level to
which the capacitor “C” is charged or change the repetition rate of the pulses, thus making
it possible to adjust the output power. In practice the waveform is not always as clean as
shown in Fig.3 due to contact bounce in the mechanical switch “S” causing a whole bundle
of pulses to occur containing all kinds of harmonic frequencies.
The output of transformer “T” is held at ground potential on the one side, while the other
side is connected to the electrode of a glass tube “N” filled with either neon or argon gas.
When the high voltage bursts occur the gas ignites and the glass tube becomes electrically
conductive on the inside. Where the glass tube touches the skin of the human body “HB” a
small capacitance is created by the electrically insulating glass barrier. Because the high
voltage bursts vary with time, a small electrical current flows into the skin. Since the body
capacitance “BC” is much larger than the barrier capacitance between the glass tube and
the skin, the major potential drop occurs across this barrier, which causes corona discharge
to occur on the glass surface. This discharge is seen as very tiny sparks.
ABOUT THE SKIN
The human skin consists of 3 major layers as shown in Fig.4. The outermost layer, the
epidermis, is the body’s actual protective layer. No blood vessels or nerve endings are found
in this layer. It is nourished by the layer
below, the dermis. The newly formed cells
near the barrier between the dermis and
the epidermis are pushing the older cells
towards the outer surface of the latter
while slowly dying, until finally they form
a thin layer of flattened dead cells, the
stratum corneum, which is the actual
surface of the skin.
The dermis, which is below the epidermis,
is made up of 80% water, elastin fibres
and collagen. It contains many blood
vessels and nerve endings and plays an
important part in temperature regulation
and healing. The sweat glands are found
in this layer, as well as the hair follicles
with their arrector pili muscles and their
oil or sebaceous glands.
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Under the dermis is the hypodermis, also called subcutaneous tissue. The hypodermis
consists primarily of loose connective tissue and lobules of fat. It contains larger blood
vessels and nerves. The blood supply to the hair follicles originates from this layer.
To stimulate the skin electrically it is essential to overcome the often poorly conducting
surface formed by the stratum corneum on top of the epidermis. This layer, which mainly
consists of dead organic matter, is a very poor electrical conductor, especially if the skin is
dry. For this reason conductive pads are used for modern electrotherapy treatment.
However, if bare metal probes are used, as with some skin or hair treating products, a
moistening liquid is necessary to ensure that electrical current flows into the skin under all
circumstances. The dermis and the hypodermis are electrically conductive. Their electrical
resistance is a nonlinear function of applied potential. Therefore, for effective stimulation
the electrical source requires proper attention.
With the instruments used in early electrotherapy the above problems are solved very
simply. The reason is that the electrical stimulus is transmitted via the capacitive barrier,
formed by the glass wall of the electrode together with the insulating properties of the
stratum corneum. Because of the high voltage, combined with the high impedance of the
barrier capacitance, a reasonably defined electrical current source supplies the dermis with
the desired electrical stimuli.
It is known that electrical stimulation decreases with distance from the outer surface of the
skin. This means that an adequate electrical current is required to stimulate the neves down
to the hypodermis. A much higher electrical stimulus would be required to affect a muscle
situated below the hypodermis.
It has been established that with a decreasing pulse width, especially below 100
microseconds, the intensity of the stimulus required to cause muscle contraction increases
rapidly. Early electrotherapy units can be considered as having very short stimulating
pulses. Therefore, even if they were to produce high currents, they would not reach the
threshold where muscle contraction occurs.
After treatment the skin often gets a slightly rosy colour, indicating improved blood flow in
the treated area. This suggests that the body responds to the treatment, implying that the
skin and the hair follicles are nourished more effectively.
Some of these early devices cause very strong stimulation, which could be excessive and
even harmful. For biological effects higher intensity is not always better. For example in
some instances positive effects regarding pain relief and healing have been observed with
the administration of minute electrical stimuli. This is due to the fact that the human body
has its own very small electrical fields, which can be influenced by small electrical currents.
MYTHS SURROUNDING EARLY ELECTROTHERAPY
In the early days nobody really understood the mechanism of electrical stimulation of the
human body and therefore all kinds of ficticious properties were attributed to the devices
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used at the time. Numerous different glass shapes were constructed with the perceived aim
to facilitate the effectiveness of the equipment for specific ailments. No wonder that today’s
technologists categorize early electrotherapy as quackery. The subsequent paragraphs are
meant to demystify some of the claims, which are still upheld by present day users of these
and similar devices.
The first myth to be unraveled is the classification of early electrotherapy as HIGHFREQUENCY treatment. Being unfamiliar with the electrical operating principle explained
above, it can easily be assumed that the device puts out a continuous high frequency signal.
However, the above description shows that the unit puts out repeated very short bursts of
damped oscillations at a low repetition rate of about 100 times per second. In terms of
today’s definition of high frequency, it would be more correct to say that we are dealing
with pulsed low frequency operation, which falls within the domain of today’s popular ‘MicroCurrent’ or TENS equipment with well established therapeutic effects.
There is the notion that a specific HIGH FREQUENCY is a critical element for the
effectiveness of the therapy. The fallacy of this assumption becomes immediately clear with
the realization that the damped high frequency bursts do not have an exact frequency due
to big manufacturing tolerances. In addition, when the glass tubes touch the skin, the
frequency is usually lowered considerably. With modern technology the pulse repetition rate
can be controlled very accurately, which is more likely to influence the therapeutic effect of
the equipment than a ficticious high frequency.
Some people claim that the effectiveness of the therapy is due to the OZONE produced by
the little arcs, which are generated around the glass tubes. These can be considered as
miniature lightning strikes, producing minute amounts of ozone. Since this gas is generated
along the entire length of the arcs which are more or less perpendicular to the skin, it
immediately mixes with the surrounding air, whereby most of it is carried away from the
surface of the skin. While the minuscule amount of gas that gets in touch with the skin
could possibly have some minor beneficial cleansing effect, it is most certainly not an
explanation for the therapeutic effect of the equipment.
There are claims that the arc, formed when holding the electrode a few millimeters away
from the skin, creates enough ozone to heal infected areas, as for example acne. In reality
the small diameter of the arc causes a very high current density at the surface of the skin,
which destroys bacteria and some cells in the area.
When the tiny arcs ‘hit’ the skin, they create minute burn marks only visible under a
microscope. Since the effect is probably much less than the skin’s exposure to radiation or
pollutants in the normal environment, this effect can be ignored. However, these little arcs
are the major physical sensation felt by the human body. Because this sensation originates
from the surface of the skin, it can be expected that the nerve endings just under the
epidermis are stimulated. In addition to the electrical pulse this could be the cause for the
possible contraction of the arrector pili muscles, which leads to clearing clogged follicle
pores. It was also observed that a flat mushroom like electrode, producing similar results as
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other electrodes produced very little arcing, and therefore practically no ozone. This would
again point to the major therapeutic effect of the electrical pulses and not the ozone.
Some of the old equipment is specified as having an OUTPUT VOLTAGE of up to 50 KiloVolts. The voltage specification is totally meaningless, because it is the electrical current,
which flows into the skin, that causes the therapeutic effect. Much lower peak output
voltages can be used by constructing the glass electrode differently. It can therefore be
concluded that such high output voltages are required to compensate for a very inefficient
device or that the stimulation created is excessive.
The output voltage is generated by the high voltage transformer often referred to as the
Tesla Coil shown as “T” in Fig.2. There are those who believe that a special construction of
the coil according to Nikola Tesla would have an important influence on the therapeutic
outcome. This is unrealistic, as a transformer has clearly defined properties, which can be
calculated and verified by measurements.
When the glass touches the skin, the neon or argon gas in the glass tube begins to glow.
The light is generated only during the very short bursts of damped oscillations. During that
period the light is very bright and will penetrate the outer layers of the skin. Some of the
colours in the wide spectrum of light emitted could have a therapeutic effect, provided the
light energy is high enough. Since the latter is not the case it is sensible to discard this
effect. Initial experiments seem to confirm this, although the small amount of infrared light
emitted could stimulate the production of some additional ATP in the mitochondria. The light
spectrum for argon gas shows some UV components, while with neon this can be ignored.
Because of the low energy levels there is no danger of UV radiation.
RELIABILITY AND REGULATORY REQUIREMENTS
Early electrotherapy devices are highly inefficient, causing the handle to get hot after a
while. Furthermore, the high voltage transformer generates enough heat to self-destruct
over time mainly due to the melting of the candle wax used for insulation. The mechanical
intensity adjustment is subject to considerable wear, making the devices even more
unreliable.
Due to the construction, traditional equipment and modern so called High Frequency devices
have the common problem of safety. The long glass tubes not only break easily, but when
broken can in some cases expose the user to dangerous electrical shocks. For this reason
marketers state that the intended use is either for experimental purposes only or need to be
handled by professionals. Since mandatory safety standards are generally not met, the
equipment may not be sold freely on the open market and cannot be found in public stores.
Another undesirable characteristic of the above equipment and its derivatives is the huge
amount of radio interference generated. In order to meet mandatory standards set by the
FCC or CE, the equipment would become not only bulky but could lose its therapeutic effect
if the problem is handled incorrectly. This again restricts selling the equipment freely on the
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open market. Equipment meeting regulatory requirements must be labled according to set
standards backed by valid certificates.
NEW TECHNOLOGY
Because the equipment described above could not meet mandatory requirements regarding
safety and EMC, industry had to develop new technology, which can comply with the set
standards. This led to a great variety of electrical stimulators, mainly for pain relief, muscle
stimulation, cosmetics and healing. The various designs differ widely from each another but
share the common need to communicate the electrical impulses to the physical body via the
skin. This is done either by specially designed conductive pads or by means of metallic
contacts. As discussed earlier, this approach is not very practical for cosmetic purposes,
especially when massaging the scalp in the presence of hair.
By combining the original concept of early electrotherapy with the latest technological
advances, it is now possible to generate a whole new generation of electrical stimulators for
a variety of applications all of which meet regulatory
requirements. With modern programmable devices it is
also possible to continuously modify the electrical stimuli
during treatment to suit the application, while at the same
time the necessity of electrical contacts or pads is
eliminated. New electronic components create the
possibility of having such devices operate efficiently from
batteries. The first in a series of such devices is the
TESLABRUSH™, manufactured in Canada.
CONCLUSION
Early electrotherpy had its merit but was badly misunderstood. Using one of its operating
principles in combination with modern technology leads to a new generation of electrical
stimulators with useful benefits.
Copyright © 2011 – 2014 Rudert Technologies Ltd
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