The application of clinical electrotherapy covers the full spectrum of electricity and magnetism, from direct currents through to light waves. We take a very brief look at developments through the ages and highlight some of its possible future progress. This article (courtesy of Everyday Practical Electronics magazine - epemag3.com) starts by looking at some early developments in medical electricity and goes on to look at some current day clinical applications across the whole spectrum, including some areas of research and pioneering technology as well as other related topics.
The term electrotherapy covers the application of just about the full spectrum of electricity and magnetism from direct currents, through electromagnetic radiation right up to light waves, stopping short of ionising radiation. Electric currents of all descriptions, along with electromagnetic waves, ultrasound, infra red and UV phototherapy as well as lasers, are all common place and in regular clinical use for eliciting thermal and non-thermal effects in the body for an extremely wide variety of conditions and dysfunctions, including wound healing and, of course, pain relief. Electrotherapy in clinical use can be regarded as another form of medicine, dispensed on prescription for a particular diagnosis or aliment. Just like medicines there is often a range of options available to the doctor. Electrotherapy is seen as another treatment option, which may not be the first or preferred choice. You are likely to see electrotherapy techniques in use in some hospitals more than others and in certain departments rather than others. As an example; for pain management there are various options for treatment using electrical stimulation techniques and equipment. Heat inducing apparatus that employs shortwave or microwave radiation (diathermy apparatus) might be used in pain management. So might infrared sources, ultrasound or lasers be used for treating pain.
Man’s interest in electrotherapy probably extends several thousand years ago. At that time only natural forms of magnetism and electricity existed. Many bracelets, necklaces and other items of jewellery made from loadstone have been found. Fishermen were certainly aware of the electrical discharge effect obtainable from certain types of fish; the electric torpedo fish is capable of delivering a very painful shock. The first recorded clinical application of electric shock therapy is attributed to Roman physician Scribonus Largus in 46AD, using the electric power of a torpedo fish as a cure for headache and gout. Galen (131 – 201AD) also advocated the use of the electric torpedo fish for all types of disease and ailments. He is perhaps the first to try muscle stimulation by electricity from a fish in his cure for anal prolapse. The practice of using the electric discharge of this type of fish for clinical reasons continued until about the mid 1800s with ever increasing applications being found. The development of manmade electricity from electrostatic generators eventually took over from the natural source of electricity from fish. Also with the development of the Leyden jar (an early capacitor) it was found that stronger electrical shocks could be obtained. Perhaps an unexpected contributor in this transformative time is the Rev. John Wesley (1702-1791), better known maybe as the founder of the Methodist Church movement. Part of his mission was to help the poor and sick people of London. In the UK at this time physician’s bills were unaffordable by the poor, Wesley sought to bring cheap medical treatment to the poor and often found himself at odds with the medical profession. Not only did Wesley experiment with electricity and documented for what aliments and conditions he found it useful, he also took as much care over investigating various other medicinal and herbal treatments. He wrote several medical books in which he extolled the virtues of electricity as a cure. By 1768 the Middlesex hospital in London was the first to have installed an electrical shock machine; many other hospitals followed this lead over the next decade. It seems almost every medical practitioner was using electricity and the diseases, illnesses, conditions etc curable or treatable by this means were unlimited. Pretty soon some very questionable cures were being offered by frauds and fakes, and over the years there have been many. One notable early quack practitioner was James Graham who in 1780 was offering a night’s sleep for £50 in his electric “celestial bed” to promote fertility. For over 100 years electricity was dispensed liberally for virtually everything presented to the doctor and of course there was also an ever increasing number of quacks. These factors contributed heavily to its decline in the early 1900s, electricity had fallen out of fashion and new ideas were not viewed with very high regard in main stream science. It was not until about the 1960s that electricity in medical circles began to make a comeback as being an effective form of pain relief, and its ability to activate muscles.
Electromagnetic waves in the radio spectrum have a very long standing medical history and are in regular clinical use by physiotherapists, primarily to deliver heat deep to tissue within the body. Broadly speaking two bands are used, shortwave and microwave. The medical term for this type of treatment and apparatus is known as "diathermy". Shortwavediathermy operates in the range 10MHz to 100MHz and the RF energy (around 27MHz in UK) is either inductively coupled to the body by means of a coil or capacitively coupled by way of insulated electrode plates. The RF output may be continuous or pulsed. Typically the average power for high dosage is about 80W with peak pulse power as much as 1kW. The heat produced can be very effective for treating joint stiffness, relieving muscle pain and spasm, as well as reducing swelling. Microwave energy is absorbed more by structures with a high water content (blood vessels, muscle, skin, internal organs but not fat). The energy is delivered to the body by means of "directors" (antennas).
In therapeutic clinical terms ultrasound (US) covers the range of frequencies between 1MHz to 3MHz (diagnostic US extends to 20MHz or beyond). Sometimes low frequency ultrasound (~44kHz) is used. Principally, US is used for wound healing and has been in use for this purpose for a number of years. A UK survey in 1985 showed 20% of all NHS physiotherapy treatments involved US; this figure rose to 54% in private treatments (Haar G., Dyson M., Oakley E. M., The use of ultrasound by physiotherapists in Britain, 1985,Ultrasound Med Biol. 1987 Oct;13(10): 659-63). Both thermal effects and non-thermal effects are utilised. An advantage of US thermal effects is that the depth of effective penetration in soft tissue can be controlled easily by altering the frequency (~4mm at 3MHz, ~11mm at 1MHz).
There are three phases of tissue repair; inflammation, proliferation and remodelling. Inflammation is characterised by the formation of a clot; this serves as a temporary seal. Clotting also releases many active substances known as "wound factors" that are used in subsequent phases and also "cleaner" agents that break down and dispose of tissue debris, foreign matter and bacteria. The proliferation phase is where deposits of new tissue( s) are formed and new skin layer is created; the process can be monitored by observing the decrease in wound size. The last phase, remodelling, takes place over months or years. The wound has fully healed, but we are left with a scar.
Ultrasound can modulate the chemical processes of the inflammatory phase in various ways that accelerate tissue repair. A single US treatment, if given early enough after injury (early inflammatory period), can be very effective. There is also evidence that wound contraction can be accelerated by the application of US during the proliferation phase. Commencing treatment at the early inflammatory phase and continuing treatment three times a week for two weeks has been shown to have a beneficial effect on scar formation. An interesting recent development using ultrasound concerns delivering drugs into the body. Ultrasound has been shown to be able to "push" certain drugs though the skin into the body; this process is known as "phonophoresis". More research is needed to clarify parameters and limitations.
Electrotherapy has been used clinically for a few centuries for numerous and countless conditions, diseases etc. Current modern day regular practice and application can be broadly classified into muscular control, pain relief, and neuromodulation. Wound healing is a relatively new application of electric current and is not in widespread practice here in the UK. Many electrical stimulators for whatever function are essentially the same – a repetitive rectangular pulse generator that switches a high-voltage stage on and off. The difference perhaps is the frequency of repetition, pulse width and amplitude which is usually a constant current or constant voltage output. Other refinements are frequently added such as "ramp-up" - "ramp-down" that slowly increases and decreases the amplitude to make the device’s use more comfortable. Often a timer will also be incorporated to deliver the stimulation for a set period of time. Electrical stimulators are often used for muscle strengthening in conjunction with some form of biofeedback, for example in toning up pelvic floor muscles for some forms of incontinence. They are also used for other muscle toning. The sports industry uses them for this purpose.