DIATHERMY

• Diathermy was once one of the most popular modalities used in rehab.

• Became less popular with development of more modern tech like US and because machine were big and cumbersome

Safety issues – electromagnetic leakage

Diathermy is used to increase tissue temp in deep tissue in order to:

1. increase delivery of nutrients to the area by increasing blood flow

2. Promote resolution of inflammatory waste products

3. Decrease pain

4. Decrease mm spasms

5. Decrease joint stiffness

6. Increase soft tissue extensibility

What is Diathermy

• Uses high frequency energy that is converted to deep heat.

• Diathermy uses nonionizing electromagnetic energy from the radio-frequency portion of the elctromagnetic spectrum

Types of diathermy used in rehab

1. Microwave2. Shortwave

– Named for position in the radio frequency continuum

*** Shortwave diathermy (SWD) is currently the only type that is commonly used in the U.S. ***

• The frequency ranges of SWD devices are rigorously controlled by the FCC.

• The most common frequency used in PT is 27.12 MHZ

Physical Properties of Diathermy

Page 386

• The intensity of the electromagnetic field produced by diathermy and tissue type determine how much energy will be absorbed by the tissue and how much the tissue temperature will increase.

• See Table 14-2 on page 387

• Similar to ultrasound, diathermy is a deep heat modality. The amount of heat delivered can be controlled thru a continuous and pulsed mode of application.

Types of Diathermy Applicators

Inductive Coil

• An inductive diathermy applicator is made up of a coil thru which an alternating electric current flows.

• The AC current in the coil produces a magnetic field perpendicular to the coil. This in turn produces eddy currents in the tissue that cause charged particles in the tissue to oscillate. The friction produced by the oscillation causes and increase in tissue temperature.

• With an inductive coil diathermy applicator heat is induced in the tissues by a magnetic field.

• The amount of heat generated in an area of tissue is affected by the strength of the magnetic field that reaches the tissue and by the strength and density of the induced eddy currents.

• The strength of the magnetic field is determined by the distance of the tissue from the applicator.

• The strength decreases with increased distance.

• The strength of the eddy currents is determined by the strength of the magnetic field in the area and by the electrical conductivity of the tissue in the area.

• Tissue with high water content have good electrical conductivity.– Muscle– Synovial fluid

Low conductivity : fat, bone, and collagen rich tissue.

Capacitive Plates

• Capacitive plate diathermy applicators are made of metal encased in a plastic housing or transmissive carbon rubber electrodes.

• A high frequency alternating electric current flows from one plate to the other thru the patient.

• An electric field is produced and flow of current in the body tissue that is between the plates.

• Heating with capacitive plates is known as heating by ELECTRIC FIELD method because electric current generates the heat produced.

• Like inductive coils, the amount of heat generated in an area of tissue is affected by the strength the strength and density of the current.

• With capacitive plates the electric current will take the path of least resistance.

• The current will generally be concentrated in more superficial tissue with good conductivity.

• Generally produce more heat in the skin than deeper structures.

Thermal vs. Nonthermal Effects of Diathermy

Page 390

Clinical Indications

Page 391

Contraindications

Page 393

Precautions

Page 394

Adverse Effects

Page 395