Application of heat results in the production of hyperemia, induction of reflex vasodilation, and acceleration of metabolic processes. Heating devices (fomentation devices) have been used for a variety of indications. General indications for therapeutic heat include pain, muscle spasm, contracture, tension myalgia, hematoma resolution, bursitis, tenosynovitis, fibrositis, fibromyalgia, superficial thrombophlebitis, and collagen vascular diseases. General contraindications and precautions for therapeutic heat include acute inflammation, trauma, or hemorrhage; bleeding disorders; temperature insensitivity; inability to communicate or respond to pain; poor thermal regulation (e.g., from neuroleptics); malignancy; edema; ischemia; atrophic skin; and scar tissue.
Hot packs, also known as hydrocollator packs, warm tissue by conduction. They typically consist of canvas bags filled with silicon dioxide that absorbs many times its own weight in water. Hot packs are immersed in a hot water bath, and are removed from the bath when needed, wrapped in 6 to 8 layers of toweling or an insulating cover, and applied to the patient. They are used to heat the body part prior to physical therapy. To avoid scalding, excess water should be drained from the pack and the covering towels or pad should be checked for excessive dampness. The packs cool slowly and can remain warm for 30 or more mins. Medicare considers hydrocollator units as non-covered institutional equipment.
Electric Heating Pads:
Because electric heating pads do not cool spontaneously, use should be limited to 20 mins to avoid the risk of burns. There is no evidence that the use of circulating-water heating pads or moist electric heating pads provide superior outcomes, in terms of enhancing recovery of function, compared to standard electric heating pads. According to Medicare DME MAC policy, it has not been established that a moist electric heating pad or water circulating heat pad with pump is reasonable and necessary compared to a standard electric heating pad. The policy states that, because a water-circulating heating pad system is not medically necessary, a replacement pump or pad is not reasonable and necessary.
According to Durable Medical Equipment Medicare Administrative Contractor (DME MAC) policy, standard electric heating pads are necessary to relieve certain types of pain, decrease joint and soft tissue stiffness, relax muscles, or reduce inflammation. DME MAC policy states that a heating pad is not reasonable and necessary to treat pain due to peripheral neuropathy, including but not limited to diabetic neuropathy.
In uncomplicated cases, heat treatments of this type, as well as paraffin baths, may not require the skills of a physical therapist.
Heat lamps warm tissues by conversion (i.e., by converting radiant energy to heat). Heat lamps often use 250-Watt incandescent bulbs and are usually placed about 40 to 50 cm from the patient. Because ordinary incandescent light bulbs produce large amounts of infrared energy, special infrared sources (e.g., quartz, tungsten) are seldom necessary. Heating rates and maximum temperatures are controlled by adjusting the distance between the lamp and the patient. Heat lamps may be preferred over hot packs where the patient is difficult to position or can not tolerate pressure. Heat lamps may also be easier to use than hot packs. According to DME MAC policy, the safety and effectivness of using a heat lamp in the home setting is not established.
Paraffin baths are primarily used to treat contractures, particularly for patients with rheumatoid arthritis, hand contractures, or scleroderma. The typical paraffin bath consists of a container filled with approximately a 1:7 mixture of mineral oil and paraffin maintained at 52°C to 54°C. Although paraffin-oil mixtures can be heated in a double boiler or stove, small commercial units are available for home use, which have the advantages of ease of use and increased safety. The patient may either continuously immerse the treated part for 20 to 30 mins, or may repetitively dip and remove the treated area from the paraffin.
Ultrasound is sound above the limits of human hearing. The therapeutic effects of ultrasound result from the conversion of sound to heat energy. Ultrasound diathermy typically employs frequencies between 0.8 and 1 MHz.
Ultrasound diathermy is considered a deep heating modality in that most absorption occurs far beneath the skin. It is most commonly used to treat tendonitis and bursitis, musculoskeletal pain, degenerative arthritis, and contractures. Maximal heating may be limited by deep tissue factors and not by skin tolerance. Ultrasound may be applied directly by placing the applicator on the skin, or indirectly by immersing the body part and applicator in a water-filled container.
Because of the importance of appropriate technique and inherent dangers, ultrasound diathermy should be applied by a trained attendant and the devices are not appropriate for unsupervised home use.
Short-wave diathermy uses radio waves to heat tissue conversively; tissue is heated by the actions of a rapidly alternating electrical field. Because of the inherent risks involved in application of this deep heating modality, short-wave diathermy machines are inappropriate for unsupervised use at home.
Microwave diathermy involves the use of microwaves for heating tissues, and offers an advantage over short-wave diathermy in treating small areas in that they can be relatively easily focused. However, microwaves generally do not penetrate tissue as deeply as short-waves.
Microwave diathermy has been used primarily to heat relatively superficial muscles and joints. Microwave diathermy is used relatively rarely, and indications for which microwaves would be appropriate often are treated with superficial heat, short-wave diathermy, or ultrasound. Because of the importance of appropriate application technique and the inherent risks of this deep heating modality, microwave diathermy machines are inappropriate for unsupervised home use.
Infrared Heating Pads:
An infrared heating pad system consists of a pad or pads containing mechanisms (for example, luminous gallium aluminum arsinide diodes) that generate infrared (or near infrared) light and a power source. According to DME MAC policy, there are no indications for which these devices have been demonstrated to have any therapeutic effect. DME MAC policy considers these devices and any related accessories not medically reasonable and necessary. As a heating device, infrared heating pads have not been shown to be more effective than electric heating pads and hot packs, despite their greater cost.
General indications for therapeutic heat include pain, muscle spasm, contracture, tension myalgia, hematoma resolution, bursitis, tenosynovitis, fibrositis, fibromyalgia, superficial thrombophlebitis, and collagen vascular diseases.
General contraindications and precautions for therapeutic heat include acute inflammation, trauma, or hemorrhage; bleeding disorders; temperature insensitivity; inability to communicate or respond to pain; poor thermal regulation (e.g., from neuroleptics); malignancy; edema; ischemia; atrophic skin; and scar tissue.