This chapter describes common methods of applying therapeutic cold and superficial heating agents; unique physiological effects; the procedures used; and the specific indications, contraindications, and precautions in their use. The deep-heating agents, therapeutic ultrasound and shortwave diathermy, are discussed in the next section.
• Multiple methods are used to apply cryotherapy and superficial heating agents. Although the physiological effects are similar within each classification—cold or heat—each technique has its individual benefits and limitations. The stage of injury, the depth of the target tissues, the uniformity of the surface area being treated, and the patient outcomes factor into selecting the method of application. In many instances more than one technique may be appropriate. Refer to Chapter 5 for a detailed description of the physiological effects of cold and heat modalities.
The various modalities presented in this chapter generally do not require a physician's prescription or direction. However, professional responsibility dictates that clinicians become aware of state practice acts and professional standards of practice and work within those boundaries.
Cold packs are delivered by one of four techniques: (1) plastic bags filled with cubed, crushed, or flaked ice; (2) reusable cold gel packs; (3) cold compression therapy (CCT) units; and (4) chemical (or "instant") cold packs.
The effectiveness of cold packs is based on their ability to safely decrease tissue temperatures to therapeutic levels. Superficial blood flow begins to decrease within the first minute of treatment. Subsequent cooling decreases cell metabolism and nerve conduction velocity. Maximum analgesia is obtained when skin temperature reaches 58°F (14.4°C) (see Therapeutic Temperature Benchmarks, Chapter 5).16,40
A layer of insulation is sometimes placed between the cold pack and the skin, often done with the well-meaning intent of patient comfort or frostbite prevention. However, with the exception of reusable cold packs, this technique limits the effects of cold to the point where the treatment yields little or no therapeutic benefits (Table 6-1).
TABLE 6-1Skin Temperatures Obtained During Cold Pack Application With Insulators Used |Favorite Table|Download (.pdf) TABLE 6-1 Skin Temperatures Obtained During Cold Pack Application With Insulators Used
|INSULATOR BETWEEN COLD PACK AND SKIN ||MINIMUM SKIN TEMPERATURE OBTAINED (°F)* |
|No insulation (baseline) ||37.8 |
|Wet wrap ||48.0 (27.0%) |
|Frozen wrap ||51.4 (36.0%) |
|Tegaderm™ ||60.8 (60.8%) |
|Plaster cast ||65.7 (73.8%) |
|Dry wrap ||67.1 (77.5%) |
|Synthetic cast ||67.5 (78.6%) |
|Dry towel ||69.6 (84.1%) |
|Wool and crepe dressing ||80.6 (113.2%) |
✱ Practical Evidence
A layer of insulation is often placed between the cold pack and the patient's skin, either for comfort or convenience. In most cases this barrier layer decreases the amount of cooling to subtherapeutic temperatures.34,133,134 An insulator ...