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Thermal agents are used in physical therapy and rehabilitation to reduce pain, to enhance healing, and to improve motion. The physical therapist should have a solid foundation in the normal physiologic control of the cardiovascular and neuromuscular systems prior to using an agent that can alter the function of these structures. In addition, a background in the physiology of healing mechanisms and of pain serves as a basis for the rationale of using thermal agents.

Often, the decision to include a thermal agent in a therapy plan or to have the thermal agent be the sole treatment rendered (as in the case of the frequently used "hot packs and ultrasound combination" for back pain) is based on empirical evidence. The purpose of this book is to provide the reader with the underlying rationale for selection of an agent to be included in a therapy program, based on (1) the known physiologic and physical effects of that agent; (2) the safety and use of the heat/cold agent, given the conditions and limitations of the patient's dysfunction; and (3) the therapeutic goals for that particular patient. The authors have been asked to review critically the literature available that documents the efficacy and effectiveness of each thermal agent. A problem-solving approach to the use of thermal agents is stressed throughout the text.

The primary audience for this text is the physical therapist. The student will gain a solid foundation in thermal agents, the clinician will strengthen his or her perspective of thermal agents, and the researcher is given information that will provide ideas for clinical studies on thermal agents. Athletic trainers and other professionals who use thermal agents in their practice should find this text of value.

The text is in three parts. Part I, Foundations for the Use of Thermal Agents, includes information from basic and medical sciences that can serve as a framework for the choice to include thermal agents in a rehabilitation program. A discussion of the proposed mechanisms by which heat and cold can alter inflammation, healing, and pain is included in these chapters.

Part II of the text, Instrumentation: Methods and Application, incorporates concepts of equipment selection, operation and maintenance, and clinical application. The leading chapter in this part is on instrumentation principles and serves to introduce concepts of equipment circuitry and safety as applied to equipment used for thermal therapy. Physical therapists have become responsible for product purchase and making recommendations about products through the expansion of consultation services, private practices, sports medicine clinics, extended care facilities, and home health care. Therefore, we must be prepared to engage in dialogue with manufacturers, product distributors, and other colleagues about the safety and quality of these products. To this end, some practical suggestions are provided in Chapter 3 to assist with purchase decisions.

Chapters 4,5,6,7,8 discuss the operation and application of heat and cold agents. Numerous principles of clinical decision-making are included within each chapter. There are certain principles inherent to all agent applications: (1) The patient must be evaluated and treatment goals established; (2) contraindications to treatment must be known; and (3) the safe and effective use of equipment must be understood.

Chapter 9, on low-power laser, deviates somewhat from the overall theme of thermal agents. Low-power laser is not expected to produce an increase in tissue temperature, so its effects could not be attributed to thermal mechanisms. Therefore, this cannot be categorized as a thermal agent. However, I believe this topic is worthy of inclusion in this text because (1) the indications for its use overlap those of thermal agents; (2) laser is a form of non-ionizing radiation, as are diathermy and ultrasound, which are used for pain reduction and tissue healing; and (3) laser would most likely be included in a physical therapy student curriculum in the coursework that includes thermal agents. At the time of this writing (summer 1985), low-power laser is still considered by the U.S. Food and Drug Administration as an investigational device. Only carefully designed clinical studies will help determine the laser's clinical efficacy—perhaps contributing to the body of knowledge needed to change the laser's status from an investigational to an accepted therapeutic product.

Part III, Clinical Decision Making, is designed to assist the student and clinician in integrating basic concepts that have been presented throughout the entire book, emphasizing problem solving and evaluation.

Much information has been published in the medical literature on the effects or clinical results of heat and cold application. Oftentimes, the therapist is called upon to justify the use of a certain modality. A careful review of the research literature may be necessary to provide an explanation for treatment.

There are many areas that require further investigation. For example, contrast baths (alternating heat and cold) are often used in sports medicine clinics. But a careful review of the literature reveals that only scanty information supports the use of contrast baths for any patient population. It is important for the clinician to be able to interpret accurately and to apply the methods and results that are presented in the literature. The inclusion of a chapter (Chapter 10) on techniques for reviewing the literature and establishing a paradigm for clinical studies of thermal agents provides the clinician with such a background on which to build.

Chapters 11 and 12 are devoted to specific patient populations in which thermal agents are commonly used. The chapter on sports medicine is representative of a population with a known cause of injury and predictable course of recovery. The majority of these patients are otherwise healthy. On the other hand, the chapter on rheumatic disease presents a model for a patient population that can be expected to have chronic recurrent—sometimes progressive—dysfunction associated with systemic manifestations.

An appendix is included: temperature conversion scales (this text uses the centigrade scale).

Susan L. Michlovitz, PhD, PT, CHT

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