Application of healing thermal agents to certain body areas that feel wounded or dysfunction is heat treatment. The main use of a heat treatment is to help alleviate pain, support muscle repose, increase function of the tissue cells, improve blood flow, and remove poison from cells and to increase the extensibility of soft tissues. Superficial and deep are the two types of heat treatment. Superficial heat treatments apply heat to the exterior part of the body. Heat aimed at certain inner tissues through ultrasound or by electric current is deep heat treatment. Heat treatments are favorable before exercise, giving a limbering up result to the soft tissues involved. Heat treatment using conduction as a form of heat transfer in hot pacts is very common. Damp heat packs are easily available in most hospitals, physical treatment centers and sports teaching rooms.
For tissue heating many thermal agents are on hand. Superficial and deep heating agents are the two groups and they usually fall within one of these two. Paraffin wax, hot packs and a hot current are some of the superficial agents. Ultrasound, which is a deep heating agent, is used to raise the temperature of deeper tissues. Application of both superficial and deep heat to the body tissues shows many physiological changes. The degree of these changes depends on some factors: the amount of tissue shown to the heat; the rate of heat inside the tissue and the degree of the temperature rise. When the heat of the tissue temperature is raised between 40°C and 45 "C (104°F and 113°F), utmost therapeutic effect can be attained. The blood flow will rise to the heated area, when the tissues reach this temperature. Tissues when heated to temperatures over this level will have the potential to burn. Many therapeutic advantages are there when the tissue temperature is increased. Temperatures effect chemical reactions in the cells within the body. (Weinberger; Fadilah, Lev, 232)
An enhancement in the chemical reaction allows for a rise in oxygen uptake, as a result more nutrients will be available to help tissues cure more rapidly. Heating an area is linked to an improved blood flow to that area. Nutrients are carried and wastes are removed away from the area more efficiently, when there is an increased blood in the wounded area. Therapeutic heating has also shown to reduce pain and to help decrease muscle contraction. The physiological changes underlying these benefits include an increase of the level where pain is experienced, an alteration in the rate of signal conduction along a nerve and a fall in the rate of commencement of the muscle fibers. Temperature increase in amalgamation with elasticity will also help to change the length of connective tissue. If full range of motion movements is not made next to a wound, connective tissue structures will gradually condense. Adhesions may expand between the tissue layers and scar tissue may develop at the place of wound to further control mobility. Heat and stretch in amalgamation can result in reduced joint stiffness and improved tissue flexibility, thereby assist in easiness of movement and increase in range of motion. (Helfand; Bruno, 303)
The deep heat causes an increase in temperature from the exchange of energy into heat as it pierces the tissue of the body where the energy is applied. Ultrasound (high-frequency sound), electromagnetic radiation (microwaves) and high-frequency currents (short wave diathermy) are some of the energy sources. The temperature sharing in the tissue heated by any of these modalities is subjected to the type of relative heating, which is the amount of energy transformed to heat at any given position. The practitioner must select a heating modality that creates the highest temperature at the place of concern without exceeding the temperature acceptance at the affected site or in the tissues above or below that site. The properties of the tissue like the specific heat, thermal conductivity and the duration of time of the heat modality is applied depends on the increase in temperature. The spreading of both heat and temperature is connected with these modalities and are placed over on the physiological temperature distribution in the tissues before the diathermy treatment. Generally, the superficial temperature is considered minimum at the skin surface and more at the center. The physiological effects of temperature arise at the place of the treatment and in remote tissue. (Lehman; De Lateur, 562)
The reactions of cellular function by direct and reflex action are the local effects and are due to the high temperature. There is an enlarged blood flow linked with capillary dilatation and increased capillary permeability. There may be changes in the pain verge and the preliminary tissue metabolism rises. Reflex vasodilatation and decrease of muscle contraction are the distant changes from the heated target location and are due to skeletal muscle relaxation. At the point where the healing results are required, energetic heating is done which causes highest temperature. The temperature rise of the tissue is fast bringing it near the forbearance level. Energetic heating is used for persistent conditions, which require heating of deep structures such as large joints. As the swelling can be concealed, this modality requires great care in use with severe inflammatory processes. As the main effect is a higher temperature at a point away from the modality treatment local temperature is maintained during mild heating. During a sub-acute process reflex vasodilatation happens when the rise of temperature is slow for short periods. With proper treatment both superficial and deep heating methods can be got by mild heating. Short wave diathermy is the best technique for large area deep heating. This modality is helpful for different indications. (Biundo; Torres-Ramos, 293)
High radio frequency electrical currents are used in the remedial treatment of heat modality. The radio frequency electromagnetic field is generally at a frequency of 27.12 MHz (1=11.06m). The main physiological effects are analgesia, sedation and hyperemia. The decrease in muscle contraction is due to the muscle relaxation and is got as a result of increased vascular supply to the treated area. A slanting method is used to treat a larger anatomic area with the primary focus at the mid point between electrodes. Proper treatment and corrections are needed. The patient's electrical impedance becomes part of the impedance of the patient's own circuit. As movement can affect the amplitude of the heat concentration applied, screening of patient movement is necessary. Selective heating of the joint is done by the inductive coil technique, which uses coil applicators that selectively heat superficial musculature unless applied to joints with least overlying soft tissue. Tissues with high water content like muscles are heated by inductively coupled units that use induced eddy currents to heat tissue. Electrical fields with units connected to provide collective capacity are used to heat low water content tissues like fat. The positioning effects are minimized by the self-adjusting resonators. (Fedorczyk, 114)
Plastic spacers or felt aid in the condenser method of treatment. To prevent localized heat focus, a towel should be used to sop up perspiration with both condenser and inductive methods. The patient must be told to stay still. The short wave diathermy unit is adjusted to low power as per patient's forbearance and the meter readings should be noted correctly. Heating localization depends upon coupling of radio waves to the patient. Microwave diathermy is a deep heat modality that selectively heats tissues with high water content and is a form of electromagnetic radiation. Short wave diathermy shows various physiological effects like hyperemia, sedation and analgesia. Secondary local vascular dilatation results in improved limited metabolism. Healing effects of deep heating modalities generally are produced by the change of applied energy into heat as it pierces tissue. The clinician should use the suitable modality for the situation at hand because the temperature allocation varies considerably across different modalities. The temperature increase produced by the modality should be the most bear by the patient to give best healing effect. For a certain restricted pathology, the deep heating modality chosen should produce a maximum temperature increase at that specific point. (Helfand; Bruno, 306)
Superficial heating modalities in contrast to deep heating modalities, generally do not heat deep tissues, inclusive of muscles as the subcutaneous sheet of fat under the skin surface acts as a thermal insulator and hinder heat transfer. Moreover, improved cutaneous blood flow from superficial heating causes a cooling reaction as it removes the heat that is applied outwardly. Usually the transfer of heat (whether the intention is heating or cooling) is divided into three types of heat transfer (conduction, convection, conversion). Conductive heating is the heat transfer from one point to another without the obvious movement in the conduction medium. Naturally a straight contact takes place between the source and the target tissues. Superficial heat is a conductive heat (hot water baths, hot packs, electric heating pads, warm compresses). Convective heating is got by movement of the moving heating medium, which is either air or fluid. (Grana, 439)