CHAPTER 97: Physical Modalities, Orthoses, and Assistive Devices

PHYSICAL MODALITIES

Modalities are commonly used to produce a response in tissues and include heat, water, cold, sound, and electricity. These modalities should not be used as the primary mode of treatment but rather used in adjunct with the main intervention such as physical or occupational therapy. This chapter will discuss the more common modalities used as well as briefly discussing electrical stimulation. Box 97-1 describes factors to consider prior to selection of a specific therapeutic modality.

HEAT

Therapeutic uses for heat are based on analgesia, increase in collagen elasticity, and hyperemia to decrease pain, reduce contractures and joint stiffness, and decrease muscle spasms.¹ Therapeutic range for heat is 40° to 45°C and is commonly maintained for about 5 to 30 minutes. It is important to note that the temperature for pain threshold in humans is 45°C.² Heat can be divided by superficial and deep heat and is dependent on depth of heat and form of transfer of heat which include convection, conversion, conduction, and radiation. Convection is the contact between two surfaces at different temperatures with resultant flow through this medium to transport thermal energy. Examples include contrast baths and hydrotherapy. Conduction is the transfer of thermal energy between two bodies by contact at different temperatures with examples such as hot water and hot packs. Conversion is the transformation of energy to heat such as ultrasound and microwave diathermy. Lastly, radiation involves thermal radiation from any surface or body with temperature above absolute zero. General precautions for the use of heat are listed in Box 97-2 but can include acute inflammation, ischemic locations, bleeding disorders, impaired sensation, malignancy, scar tissue, and those with inability to communicate or respond to pain.³

Superficial heat is considered to be 1 to 2 cm and deep heat generally involves increasing tissue temperature to a depth of 3 to 5 cm or more. Examples of superficial heat include heating pads, hydrocollator packs, whirlpool baths, and paraffin baths which achieve maximal tissue temperature in the skin and subcutaneous fat. Hot packs such as hydrocollator packs are commonly stored in heated water tanks and need to be wrapped in layers of insulation prior to being applied to the skin. Caution should be used as this type of modality is one of the most common reasons for burns in therapy sessions. Radiant heat in the form of heat lamps can also be used therapeutically and is usually placed 30- to 60 cm from the patient's body and is useful when ...