Chapter 12

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

• Evaluate how the diathermies 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.
• Demonstrate the equipment setup and treatment technique for microwave diathermy.
• Discuss the various clinical applications and indications for using continuous short-wave, pulsed shortwave, and microwave 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 resistance of the tissue to the passage of the energy. Diathermy may also be used to produce nonthermal effects.

 Diathermy can have both thermal and 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. For the past 15–20 years, clinicians have not widely used diathermy. It is likely that many young clinicians have never even seen a diathermy unit. 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 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 or microwave 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 the infrared modalities, and further it has been shown that pulsed shortwave diathermy produces the same magnitude and depth of muscle heating as 1 MHz ultrasound.4,5

### Thermal Effects

The diathermies are not capable of producing depolarization and contraction of skeletal muscle because the wavelengths are much too short in duration.6,7,38 Thus, the physiologic effects ...

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