short wave diathermy, Essays (university) of Physics

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Short Wave Diathermy

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Lecture Electrotherapy - Prof. K. Mamdouh, Ms. I. Devreux

 The concept of producing heat deep within the

tissues, beyond the reach of infrared and other forms of superficial heat is appreciated by physical therapists.

 Currents with oscillations greater than 1000 Hz

(cycles / second) are termed high-frequency currents.

 Generally, this type of currents used to generate

heat, is in the megacycle range.

 Most commonly utilized high-frequency

currents are found with: * Short wave diathermy.

• Microwave diathermy.

Lecture Electrotherapy - Prof.

 Short wave diathermy has been a viable

modality in physical therapy for many years.

 Originally, it was utilized for musculoskeletal

conditions which require increased circulation and other benefits of thermal increase.

 Short wave diathermy has proven an effective

modality in the management of non-orthopedic conditions: ◦ such as pulmonary, urologic and gynecological conditions.

Lecture Electrotherapy - Prof.

 Heat generation through short wave diathermy depends on the molecular activity within the tissue exposed.

 Differential heating is noted within bone, muscle and fat because of the different densities of these tissues.

 Note:

◦ The more-dense tissue naturally becomes warmer than the less-dense one. ◦ Actually, the shorter the wavelength or the higher the frequency is, the greater the penetration will be.

Lecture Electrotherapy - Prof.

The principal effect of short wave diathermy on the body is the production of heat in the tissues due to the rise of temperature.

1. Increased metabolism:

Heating tissues accelerates chemical changes such as metabolism, so oxygen and food stuffs are used up. With increased metabolism, there will be increased output of waste products.

Lecture Electrotherapy - Prof.

2. Increased blood supply:

As a result of increased output of waste products such as metabolites, which act on the walls of the capillaries and arterioles, these tissues dilate.

In addition, heat has direct effect on blood vessels, causing vasodilatation.

Heat also produces stimulation of superficial nerve endings, causing reflex dilatation of the arterioles.

Vasodilatation increases blood flow through the area, so that the necessary oxygen and nutritive materials are supplied and waste products are removed.

Lecture Electrotherapy - Prof.

4. Fall in blood pressure:

The generalized vasodilatation reduces the peripheral resistance to blood flow. Heat also reduces blood viscosity, which helps in the reduction of blood pressure.

5. Increased activity of sweet glands:

If a general rise of temperature occurs, there will be increased activation of the sweet glands.

Lecture Electrotherapy - Prof.

1. For chronic and mild conditions:

• Myositis and arthritis.
• Pelvic inflammation.
• Otitis media.
• Bronchitis.
• Sinusitis.

2. As an adjunctive modality:

Short wave is also used with other procedures such as iontophoresis to enhance local absorption

Lecture Electrotherapy - Prof.

4. Pregnancy: Diathermy shouldn’t be applied to the

abdomen or pelvis during pregnancy.

5. Metals in the tissues: Diathermy causes

concentration of electric field in the metal, which may precipitate burns.

6. Loss of skin sensation: It is safer to avoid the

application of diathermy to cases where there is loss of skin sensation.

7. Tumors: Short wave diathermy shouldn’t be

applied to areas of malignant growth.

8. X-ray therapy: X-ray therapy devitalizes the

tissues, rendering them more susceptible to damage. SW shouldn’t be applied to areas recently exposed to therapeutic doses of X-rays.

Lecture Electrotherapy - Prof.

Lecture Electrotherapy - Prof.

b) Cable method:

 The cable is coiled in relation to the patient’s skin but separated from it by a layer of insulating material.

 As high-frequency currents oscillate in the cable, an electric field is set up between its ends and a magnetic field around its center.

 These fields affect the tissues that lie within them.

Lecture Electrotherapy - Prof.

Electrode arrangement:

• Contraplanar technique:

It is the most satisfactory technique, especially for the treatment of deeply-placed structures.

The electrodes are then placed over the opposite aspects of the trunk or limb, so that the electric field is directed through the deep tissues.

Lecture Electrotherapy - Prof.

* Cross fire technique:

 Half of the treatment period is given with the electrodes in one position and then they are moved to be at right angle to that obtained during the first part of the treatment.

 For example, for the knee joint, during the first half of the session, the electrodes are placed on the medial and lateral aspects of the knee.

 On the opposite, during the second half of the session, the electrodes are transferred to the anterior and posterior aspects of the knee.

Lecture Electrotherapy - Prof.

• Monopolar technique:

 The active electrode is placed over the site of the lesion, while the indifferent one is applied to some distant part of the body.

 This method is used for very superficial lesions

(sinusitis).

Lecture Electrotherapy - Prof.