Alternative Pain Relief in the Mainstream
In the last few decades, many medical professionals have found that there are several ways to help their patients heal without the use of or with limited use of long-term pain medication use. Therapies such as therapeutic massage, neuromuscular stimulators, and therapeutic ultrasound have revolutionized the way the medical community can aid in patient healing.
Another type of technology that has shown real worth in the clinical setting is shortwave diathermy. This method of controlling pain and increasing the blood flow to damaged muscle areas acts with deep heat, as opposed to sound waves like therapeutic ultrasound. In conjunction with other non medication-based therapies, shortwave diathermy can help a large number of patients with varying degrees of injury, as well as different types of injury.
How Shortwave Diathermy Works
The temperature distribution in the tissues heated by short radio waves results from the pattern of relative heating, which is the amount of energy converted to heat at any given location. The practitioner should choose a heating modality that produces the highest temperature at the site of focus, without exceeding the temperature tolerance at the affected site or in tissues above or below that site. The temperature rise depends on the properties of the tissue, including the specific heat, thermal conductivity, and the length of time that the heating modality is applied.
The temperature rise and distribution of heat that are associated with RF (Radio Frequency), are superimposed on the physiologic temperature distribution in the tissues, prior to diathermy application. Usually, the superficial temperature is low at the skin surface and higher at the core.
The Physiological Effects of Temperature
The physiological effects of temperature occur at the site of application and in distant tissue. The local effects are caused by the elevated temperature response of cellular function by direct and reflex action. Locally, there is a rise in blood flow with associated capillary dilatation and increased capillary permeability. Initial tissue metabolism increases, and there may be changes in the pain threshold. Distant changes from the heated target location include reflex vasodilatation and a reduction in muscle spasm (as a result of muscle relaxation).
Vigorous heating produces the highest temperature at the site where the therapeutic result is desired. The tissue undergoes a rapid temperature rise, with the temperature coming close to the tolerance level. Vigorous heating is used for chronic conditions that require deep structures, such as larger joints, to be heated. When acute inflammatory processes are occurring, deep heating requires extreme care, because it can obscure inflammation.
Local tissue temperature is maintained during mild heating, the primary effect being the production of a higher temperature at a site distant from the heating modality’s application. Reflex vasodilatation occurs when the rise in temperature is slow for short periods, such as during a sub-acute process. With the proper application, superficial and deep heating methods can accomplish mild heating.
Radiofrequency (RF) Energy and Shortwave Bands
When radio-frequency energy of sufficient intensity is directed at biological tissue, it will cause heating. This effect was recognized many years ago and has been used therapeutically since 1928. Commercial units generate RF energy at shortwave bands (13 MHz, 27 MHz, etc.)
Shortwave diathermy (SWD) equipment is designed to emit either a constant or a pulsed output and sometimes provides both. Constant output units are used primarily to achieve deep heating of tissues. Pulsed output allows cooling between pulses, heats less strongly and possibly enhances the non-thermal influences of RF energy. Many studies have shown a beneficial therapeutic effect with pulsed output, although the mode of action remains still obscure.
Continuous Shortwave Diathermy
Continuous Shortwave Diathermy (SWD) is widely used clinically, but remains poorly researched. Practical details of Continuous Shortwave Diathermy (SWD) use are not included here. However, it should always be kept in mind that this equipment can cause serious burns if used incorrectly.
The design of shortwave diathermy units will vary between the manufacturers, as does the maximum power output and range of compatible applicators.
Each unit consists of a generator and amplifier designed to deliver an output at a single frequency and with intensity capable of producing therapeutic effects. The energy at the output of the amplifier is fed to a coupling circuit that delivers the energy via various types of applicators, to the patient. The whole system is tuned into resonance manually or automatically to allow the maximum amount of energy to be delivered.
The applicators convey energy either by acting as a capacitor, in which the tissues of the patient behave as a dielectric within the electric field, by means of rigid or flexible air- or felt-spaced electrodes, or by acting as an inductor. The latter technique employs an insulated cable that is either pre-formed into a flat spiral and contained within an insulated casing, or is wound by hand to enclose or lie adjacent to the target tissue which then behaves primarily as a conductor within a magnetic field. The ability of these applicators to heat the musculature, while retaining a low temperature in the subcutaneous fat varies considerably.
The very simplified explanation of the RF heating effect can be as following: Oscillating electric and magnetic fields produce heat in biological tissues by inducing a rapidly alternating movement of ions, rotation of dipolar molecules and the distortion of non-polar molecules. A movement of ions represents a real flow of current and occurs readily in tissues rich in electrolytes, such as blood vessels and muscle. Resistance to this flow leads to heart production.
By contrast, in fatty tissue the main effect of an alternating electromagnetic field is to produce rotation and distortion of molecules, which does not constitute a real flow of current, therefore little heat is generated.
The activity of the Continuous Shortwave Diathermy (SWD) field at molecular level should cause blood vessels and muscle to heat strongly and adipose tissue to heat properly. Experience reveals, however, that adipose tissue is also heated vigorously because it is permeated by small blood vessels that contain a solution of electrolytes. The heat generated is then retained due to the insulating properties of fat allowing a high temperature to develop. Fibrous tissue is not particularly rich in either blood vessels or fat and usually shows a moderate elevation of temperature.
How Therapeutic Changes Occur
Therapeutic changes only occur when the temperature of the tissue rises to 40-45oC. Below this there is little demonstrable effect. At higher temperatures the rate at which proteins denature proceeds more rapidly than repair, resulting in irreparable cell damage and acute pain.
In general, the tissue response to Continuous Shortwave Diathermy (SWD) compares closely with that from other methods of heating, and the common indications and contradictions are similar to those for superficial heating. Those differences which do however exist, originate in the patterns of heating generated by the diathermies, which are unlike those produced by more superficial heating. Diathermy heats both the deep and superficial layers of tissue whilst the effect of superficial heating is most marked in the skin and subcutaneous tissues. The physiological response also depends upon the magnitude of the rise in temperature, rate of rise, volume of tissue heated and the efficiency of the homeostatic mechanisms active in dissipating heat.