INTRODUCTION
The use of physical agents and devices to reduce pain and improve function has a long history in the practice in medicine. In recent decades, technology has increased the variety of modalities available to the practitioner. This chapter surveys the most commonly used options, with the goal of aiding the practitioner in choosing among alternatives. Despite widespread use and decades of experience, however, consensus is lacking regarding indications, implementation, and efficacy for many of these approaches.
SUPERFICIAL HEAT THERAPY
Heat may be transferred to a patient from an object, a device, or water using hot packs, heat lamps, paraffin baths, and whirlpools. All of these options are considered superficial heating modalities because they are unable to produce temperature changes of more than a few degrees at depths of 1–2 cm. It is generally accepted that heat increases the extensibility of collagen tissue, decreases joint stiffness, relieves muscle spasms, provides pain relief, and increases both blood flow and metabolism. Superficial heat is an adjunctive treatment and generally not the primary curative intervention. Table 8–1 lists general precautions and contraindications for its use. Permanent brown skin discoloration (erythema ab igne) can result from repeated chronic overuse of superficial heat.
| Sensory deficits |
| Cutaneous insensitivity |
| Edema |
| Acute inflammation, trauma, or hemorrhage |
| Circulatory impairment |
| Bleeding disorders |
| Inability to communicate or respond to pain |
| Poor thermal regulation (eg, from neuroleptic drugs) |
| Malignancy |
| Ischemia |
| Atrophic skin |
| Scar tissue |
| Unstable angina or blood pressure |
| Decompensated heart failure within 6–8 weeks of myocardial infarction |
Many different varieties of hot packs are available. Outer layers may be made of rubber, cloth, or soft plastic; the interior may be filled with a gel, water, or another substance with a high heat capacity. A common type used in clinics is a hydro-collator pack, which contains a silicate gel that absorbs water and creates a high heat content. This pack is usually submerged in a self-contained heated water solution. It is removed and wrapped in towels to protect the patient from the pack temperature of 70–80° C. Some hot packs can be heated in a microwave. Other heating devices circulate a fluid through tubes to a pad or cuff. Electrical current can also be used to produce heat in a pad.
Hot packs warm tissue by conduction. Heat conduction, also called diffusion, is the direct microscopic exchange of the kinetic energy of particles through the boundary between two systems. Skin tolerance, tissue thermal conductivity, and the body’s responses to increased temperature limit the effective depth of temperature changes to a few centimeters.
Hot packs are commonly applied to patients with a variety of conditions, including muscle sprain and strain, tendonitis, bursitis, muscle spasm, contracted muscles or joints, osteoarthritis, rheumatoid arthritis, spasticity, chronic pelvic inflammatory disease, and superficial phlebitis. Hot packs can be used to facilitate hematoma resolution or muscle relaxation prior to traction or stretching.
In writing a prescription for use of hot packs, the patient’s name, age, diagnosis, goal, and precautions are delineated. The prescription should include the area of application and time usage. Time of application can vary from a few to as long as 30 minutes. Frequency of application is typically three times a week. Flexibility can be provided for the therapist by expressing this information as a range; for example, “Hot packs to lumbar sacral area for 10–20 minutes to tolerance.” Extra caution must be used when applying hot packs to insensate individuals as burns have been reported. For this reason, many hospitals use only a very low heat system for this patient group.
Although inexpensive and versatile, heat lamps are used less frequently in clinics today than in the past. They consist of a bulb (typically 250 W) energized by electricity that emits a light source that can be incandescent or a special infrared. Ordinary incandescent lightbulbs emit large amounts of infrared light, so special tungsten or quartz-type bulbs are rarely necessary. The patient is positioned about 40–50 cm from the light source. Moving the lamp farther away or closer to the target tissue controls the amount of heat administered.
Heat lamps convert radiant energy to heat. In this case the infrared light generated is converted to heat energy on the target tissue. The distance between the heat lamp and the patient controls the rate of heating and the temperature achieved. The intensity radiating from a point source (energy per unit of area perpendicular to the source) is inversely proportional to the square of the distance from the source.
The applications for heat lamp use are generally the same as those for hot packs. Factors influencing the choice include ease of application to the target tissue (placement can be difficult depending on the patient’s position) and whether the area to be treated is intolerant to pressure. If the patient would benefit most from moist heat, then hot packs will be preferable to a heat lamp.
In writing a prescription for heat lamp use, the patient’s name, age, and diagnosis are delineated, along with the treatment goal, precautions, area of the body to be treated, and duration. Precautions are included to adjust to tolerance of the patient and to monitor frequently. The typical duration is a few to 20–30 minutes, and frequency is generally three times a week, although daily application for a limited time may be helpful in some patients. An example might be, “Heat lamp to right medial elbow area for 10 minutes to tolerance.” Any integrative modalities should also be listed, along with how they fit into the treatment plan.
Application of superficial heat via paraffin bath utilizes a small container of mineral oil and paraffin wax (1 part mineral oil to 6 or 7 parts wax) that is heated to 52–54° C in a tabletop or standalone unit. The patient immerses a clean limb (usually the hand) into the unit and coats it several times (eg, 7–12), obtaining a thick glove of paraffin wax. The coated limb is then placed in an insulated mitten or towel for up to 30 minutes. The conductive heating provided by this method facilitates active range of motion (ROM), friction massage, and improvements in hand function for patients with rheumatoid arthritis and scleroderma.
Heat transferred by conduction is obtained by summation of several layers of wax that build up on the affected area, typically the hand. Because paraffin has a low heat capacity and insulates the engulfed tissue, the received temperature of 45–54° C is tolerated by the tissue better than similarly heated water. Heating of the skin to 47° C at first is followed by a decline to a few degrees above baseline. While subcutaneous tissue temperatures can increase 3–5° C, intramuscular and intraarticular temperatures increase only by 1° C. Despite good tolerance by patients, a thermometer inserted in the mixture is recommended for safety. The temperature elevations in the treated tissue decrease after 15–20 minutes.
Paraffin baths have many applications, including subacute or chronic wrist, hand, digit, foot, or ankle injuries; contractures from burns; osteoarthritis; inflamatory arthropathies; and muscle, tendon, and joint contractures.
The prescription for a paraffin bath should delineate the patient’s name, age, and diagnosis; outline goals; and list precautions, which include specifying “to tolerance of patient” and “monitor frequently.” Duration is 20–30 minutes; frequency can be three times a week for several weeks.
A sample prescription might read, “[Patient Name], 35-year-old male, contracture of digits post-traumatic hand injury. Goals: Increase ROM of digits. Precautions: To tolerance and frequent communication with patient to reference any increased discomfort. Paraffin wax to left hand via dipping technique, wrap for warmth 20–30 minutes, then active assisted and passive ROM to tolerance.”
In whirlpool therapy, also called hydrotherapy, a tank containing water may be heated, cooled, or agitated to provide the desired treatment effect. Tanks vary in size from 120 to several thousand liters. Large tanks (eg, Hubbard) allow for treatment of multiple body areas simultaneously.
Musculoskeletal injuries, burns, wound cleaning, arthritis, and stiff or frozen joints are the main indications for hydrotherapy. Stiff joints can be heated to facilitate movement, and acute traumatized limbs can be cooled. Immersion in water can decrease stress on bones and joints. Benefits in wound and burn care include removal of gross contaminants, toxic debris, and dilution of bacterial content. Additionally, bandages can be removed more easily following hydrotherapy.
Hydrotherapy uses water as the medium, but alternative media can include pulverized corn cobs or small beads heated and circulated in a chamber by hot jet air (a modality termed fluidotherapy). In this variation, the patient’s limb is placed in a dry, high-temperature (46.1–48.9° C), low-heat-capacity environment. Hand and foot temperatures of 42° C and 39.5° C have been obtained after 20 minutes. Advantages include the ability to perform ROM exercises and massage.
Table 8–2 lists contraindications for whirlpool therapy. The long-term benefits of this approach remain controversial.
In whirlpool therapy, heat is transferred around tissue by convection. Heating of the body or body parts is facilitated by the agitation of the water (or alternative medium), thus preventing formation of an insulating layer. The temperature of the heated whirlpool water is generally 33–39° C for a patient without evidence of ischemia. If a small area of the body is treated, a greater range of temperatures can usually be tolerated before core body temperature change is noted. Limbs can be heated to a higher temperature (43–45° C) in healthy adults, but in individuals with vascular impairment, temperatures above 32° C should be avoided because of the risk of precipitating an ischemic event. For immersion of larger areas in a patient without vascular impairment, neutral temperatures (33–36° C) are recommended to decrease the likelihood of adverse changes to core body temperature. In healthy people near-total immersion in temperatures up to 40° C (104° F) can be tolerated for short periods; this equates to the maximum usually recommended for personal hot tubs. Exposure time to temperatures higher than that of the normal body must be monitored as the body’s ability to cool itself can be overcome, leading to altered homeostasis.
Whirlpool is well suited for the treatment of wounds and burns. Large tanks such as the Hubbard can accommodate the whole body. The variable agitation, heat, and solvent action can help debride a wound and remove adherent bandages or dead skin. The use of various additives can provide a bactiricidal element to the overall process, aiding in the treatment of infections. However, there is little consensus on which antimicrobials to use or their effectiveness. Among the commonly used antimicrobial agents are sodium hypochlorite, providine–iodine, chlorhexidine gluconate–isopropanol, and chloramine. Isotonic sodium chloride can be added for treatment of very large wounds to minimize fluid shifts (900 g/100 L) in sensitive individuals.
Concern has been expressed about the possibility that antimicrobial agents used in whirlpool treatments may adversely affect the healing of wounds. Research suggests that overuse of additives may harm the cells involved in tissue repair. For this reason, use of antimicrobial additives should be directed to necrotic, heavily exudative wounds, with monitoring and discontinuation of chemicals as the wound cleans up. Concerns about cross-contamination have led some hydrotherapy providers to use disposable liners for each patient treatment.
Mobilization of joints in patients with arthritis or other musculoskeletal conditions (eg, involving the ankles and wrists, but not limited to them) can be facilitated, particularly after cast removal. Acutely sprained joints can be cooled via whirlpool. Muscle soreness and fatigue in athletes can be addressed with cold-water immersion in a nonagitated tank. (See also Cryotherapy, below).
In addition to listing the patient’s name, age, diagnosis, goals, and precautions, the hydrotherapy prescription must specify the area to be treated, water temperature, and any additives. Treatment duration is generally 15–20 minutes for each session, although shorter times may be appropriate for some patients. Treatment with additives is continued until the wound starts to improve (eg, a few days to weeks or more).
As an example, a diabetic patient with a leg wound from a burn and contractures of the ankle might benefit from the following prescription: “Whirlpool to left leg wound as tolerated for 15–20 minutes 3 times a week for 2 weeks. Keep temperature below 32° C and u se sodium hypochlorite until wound begins to become clean. Please stretch ankle after heating. Discontinue treatment if patient complains of increased pain or worsening of condition and return for evaluation in 2 weeks.”
CRYOTHERAPY
Like therapeutic heat, cryotherapy, the therapeutic application of cold, has utility in treating a wide variety of conditions. Ice and cold are both considered superficial agents. The depth of cold penetration is limited by adipose tissue, and by tissue circulatory responses that attempt to maintain homeostasis, and is generally a few centimeters. Vapor sprays use an evaporative mechanism of action to freeze the outer skin, albeit for a few seconds. Ice packs made of ice, water, and various thin materials are inexpensive and effective options. Cryogel chemical packs are easily transported and stored, and can be instantly activated by punching the pack, which starts an endothermic chemical reaction. Other cryogel packs, which may be soft or hard, are stored in a freezer for later use. Icewater devices with cuffs or tubes can be used to selectively cool specific areas, such as the knee or shoulder, and provide a relatively constant cooling action utilizing circulation from an ice bath reservoir. Large tanks or tubs can be filled with icewater for near-full immersion. Ice massage combines pressure on the tissue in addition to the cold.
The generally accepted effects of cooling are decreases in tissue blood flow (vasoconstriction), tissue metabolism, oxygen utilization, inflammation, muscle spasm, spasticity, nerve conduction, and pain. Decreases in tissue temperature have been shown to decrease muscle force production, muscular power, and proprioception. Table 8–3 lists contraindications for cryotherapy.
The cooling effect of an ice pack begins at the skin, dropping the temperature to 12–13° C in 10 minutes. Subcutaneous tissue temperature decreases 3–5° C in 10 minutes, and deep muscular temperatures falls the least, by a degree or less. With longer periods of cooling (more than 20 minutes, up to 3 hours), forearm muscle temperatures drop 6–16° C, and intraarticular knee temperatures by 5–6° C. Muscle spindles, γ fibers, nerve conduction, and muscle contraction are all influenced by cold. When cooling is provided by means of whirlpool, the agitated water and ice limits formation of an insulation layer.
In muscle injury, the early use of cryotherapy is associated with significantly smaller hematoma formation between the ruptured myofiber stumps, less inflammation, and somewhat accelerated early regeneration. In rheumatoid arthritis, reductions in histamine and intraarticular collagenase have been reported. The initial onset of cooling causes a local reflex and increased sympathetic tone, resulting in vasoconstriction; however, subsequent body response to further cooling may or may not lead to a reactive vasodilation. The dilation of deeper vessels limits the effect of the cold on deeper tissue. Analgesia can be achieved in 7–10 minutes.
Cryotherapy applications include acute soft tissue injuries and trauma, reduction of compartmental pressures, muscle soreness, sprains, strains, spasms, spasticity, fractures, traumatic joint injuries, joint inflammation, joint surgeries, burns, chronic musculoskeletal pain, dental pain, oral surgery, injection sites, and postsurgical sites.
The prescription of cold modalities must take into account the area to be treated, the tolerance of that area, and the duration of treatment desired. A vaporizing spray will quickly cool the skin; however, the effect lasts for only few seconds. The transient increased pain threshold can be useful in reducing the discomfort of injections of joints or trigger points. Typical application times for cold packs and ice are about 20 minutes. A cryocuff or device can be applied for longer periods (eg, 1–2 hours) in patients after joint surgery, depending on tolerance. Because whirlpool temperatures below 13–15° C are usually uncomfortable, session times for this cooling modality are typically 10–20 minutes.
The patient’s name, age, and diagnosis should be clearly delineated, as well as goals and precautions. A sample prescription might read, “[Patient Name], 44-year-old male, with lumbar sprain. Goal: Reduce spasm and pain. Precautions: To tolerance, frequent monitoring, and discontinue if increased discomfort. Ice to right side lumbar area for 10–20 minutes, 3 times a week for 2 weeks. [Any other modalities to be used should be noted.] Return for evaluation in 2 weeks.”
DEEP HEATING THERAPY
Ultrasound, short-wave diathermy (SWD), and microwave diathermy can attain deep heating of body tissues, which may have benefit for some patients after traumatic injury or surgery. The choice of modality is often based on availability, but subtle differences exist that may influence the practitioner’s decision of which to prescribe.
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