Chapter 12: Shortwave and Microwave Diathermy

OBJECTIVES

Following completion of this chapter, the student will be able to:

• Evaluate how diathermy may best be used in a clinical setting.

• Explain the physiologic effects of diathermy.

• Differentiate between capacitance and inductance shortwave diathermy techniques and identify the associated electrodes.

• Compare treatment techniques for continuous shortwave and pulsed shortwave diathermy.

• Discuss the various clinical applications and indications for using continuous short-wave, pulsed shortwave diathermy.

• Identify the treatment precautions for using the diathermies.

• Analyze the rate of heating and how long muscle retains the heat generated from a shortwave diathermy treatment.

• Compare and contrast diathermy and ultrasound as deep-heating agents.

Diathermy is the application of high-frequency electromagnetic energy that is primarily used to generate heat in body tissues. Heat is produced by either resistance of the tissue to the passage of the energy or by friction, kinetic energy or eddy currents. Diathermy may also be used to produce nonthermal effects.

Diathermy as a therapeutic agent may be classified as two distinct modalities, shortwave and microwave diathermy. Shortwave diathermy may be either continuous or pulsed. Continuous shortwave diathermy has been used in the treatment of a variety of conditions for some time. However, in the past decade most of the shortwave diathermy treatments are pulsed (PSWD). For some time now, clinicians have not widely used diathermy. It is likely that many young clinicians have never even seen a diathermy unit. Another reason that diathermy fell out of use was because of the negative articles written about it. A survey of over 42,000 physical therapists found a modest increase in the risk of miscarriage of pregnant therapists who were regularly exposed to microwave diathermy.³ Regular exposure to shortwave diathermy during pregnancy, however, did not increase the risk of miscarriage.^3,61 However, over the last 5 years there seems to be renewed interest in this treatment modality due in large part to some newly published, evidence-based information that has begun to appear in the professional literature.^{1,2,3,61–68} In addition, there appears to be renewed effort by equipment manufacturers who are once again beginning to market pulsed shortwave diathermy units.⁴ Shortwave diathermy is a relatively safe modality that can be very effectively incorporated into clinical use. Clinically, shortwave diathermy is much more commonly used than is microwave diathermy.

The effectiveness of a shortwave diathermy treatment depends on the clinician's ability to tailor the treatment to the patient's needs. This requires that the clinician have an accurate evaluation or diagnosis of the patient's condition and knowledge of the heating patterns produced by various diathermy electrodes or applicators. Many clinicians mistakenly feel that neither shortwave nor microwave diathermy produces heating at the depths desired for the treatment of musculoskeletal injuries. In fact, the depth of penetration is greater than with any of ...