Short-Wave Diathermy .

Short-Wave Diathermy is the most commonly used physiotherapeutic modality for deep heating. The meaning of diathermy is heat given through an object and not confined to that object (Nagel Schmidt, 1908). Short-wave diathermy has been used for more than fifty years by physiotherapists around the globe, for deep heating purposes.

For short-wave diathermy, high frequency current with a frequency of 27.12 MHz and 11 meters wavelength is used. Other high frequency currents with their corresponding wavelengths, which are less commonly used, are 45 MHz with 7 meter and 13 MHz with 22 meter.

Production  of Short-wave diathermy .

Principle .

It is not possible to produce a high frequency current required for short-wave diathermy by mechanical means. Hence, discharging a condenser through an inductance of low ohmic resistance produces high frequency current with the desired frequency and wavelength.

Circuit .

The basic circuit consists of two parts, such as oscillator circuit and resonator circuit. In addition to this, an ammeter can be integrated in resonator circuit so as to register the resonance between oscillator circuit and resonance circuit. Oscillator circuit: It consists of a condenser and inductance. The values of condenser and inductance are such that they produce high frequency current with a frequency of 27.12 MHz. A valve is used along with condenser and inductance, so as to allow repeated charging and discharging of the condenser.

Resonator circuit .

It is also known as patient’s circuit. It consists of a variable condenser and an inductance coil. High frequency currents are transmitted from oscillator circuit to resonator circuit with the help of a variable condenser. Nerve Conduction Velocity

Ammeter .

The ammeter does not show the amount of current received by the patient but it shows when the oscillator and resonating circuits are in tune with each other. In most of the imported machines there is an automatic tuner (just like television sets) and hence, ammeter is not included in these types of machines.

Working .

When mains are switched on, it causes repeated charging and discharging of condenser C1 and produces high frequency current in oscillator circuit. As a result, high frequency current is also likely to develop in resonator circuit but maximum high frequency current can be produced in resonator circuit, if oscillator and resonator circuits are in tune or are in resonance with each other.

Tuning can be obtained manually by varying the capacity of the C2 condenser and the same can be confirmed from ammeter, which will show maximum deflection if these two circuits are in resonance with each other. In an automatic tuner, the machine does this automatically. Output is controlled by power or intensity control of the machine, which regulates the output by adjusting the grid bias of valve through variable resistance.

Electrodes Placement .

Electrodes are conductors through which current is applied to the body tissue. In case of short-wave diathermy, electrodes are the conductors through which short-wave diathermy current is applied. Nowadays, pad electrode, disk electrode, monode, minode, drum electrode and occasionally sinus electrodes are used for short-wave diathermy applications.

However, in the past, a number of electrodes, such as cable electrode, axillary electrode, rectal electrode and vaginal electrode were used. Condenser field electrodes such as, pad or disk electrodes can be arranged in monopolar, coplanar, contraplanar and crossfire arrangement.

Monopolar method . 

In monopolar arrangement, one electrode that may act as an active electrode is placed over the area to be treated and the other indifferent electrode is applied to some distant part of the body with maximum spacing so that the heating is produced at only the specific area that is treated.

Coplanar method .

In coplanar arrangement, electrodes are placed side-by-side on the same aspect of the part to be treated, provided that, there is an adequate distance between them. This arrangement is commonly used in the treatment of the back.

Contraplanar method . 

In contraplanar arrangement, electrodes are placed over opposite aspects of the body part treated, so that high frequency current is directed through the tissues. Contraplanar method is commonly used in the treatment of hip joints.  Electromyography

Cross-fire method .

In crossfire arrangement, half the treatment is given with the electrodes in one position then the arrangement is changed, so that the electric field lies at right angles to the electric field obtained in the first part of treatment. It is commonly used in the treatment of knee joints, treatment of sinuses, pelvis and thorax. While arranging the electrodes during the treatment, consideration should be given to the size of electrode, electrode spacing and position of electrode.

Size of Electrode .

Size of electrode should be larger than the body part that is to be treated, spacing should be as wide as the output the machine permits. In the space between electrode and the body part, there should be a medium with low dielectric constant such as air, felt with air columns or towels. Electrodes should be positioned in such a way that they are parallel to the body part to be treated.

Indications of Short-wave diathermy .

Short-wave diathermy can be used in the treatment of various orthopedic, as well as some of the non-orthopedic conditions.

1. Low back pain .
2. Osteoarthritis .
3. Rheumatoid arthritis .
4. Sprains .
5. Strains .
6. Muscle tear .
7. Tendon tear .
8. Capsulitis .
9. Tendonitis .
10. Frozen shoulder .
11. Myalgia .
12. Bursitis .
13. Hematoma .
14. Neuralgia .
15. Neuritis .
16. Traumatic arthritis .
17. Ankylosing spondylitis .
18. Fibrositis  .
19. Rectus femoris strain .
20. Hamstrings strain.
21. Tensor fascia lata strain .
22. Hip pointer .
23. Contusions of Thorax.
24. Infected surgical incisions and stitch abscess.
25. Chronic sinusitis and chronic otitis media.
26. Chronic bronchitis .
27. Chronic obstructive airways disease .
28. Pleurisy and pleuritis.
29. Nonspecific pelvic inflammatory disease.
30. Abscess .
31. Inflammation of gallbladder and ducts .
32. Peritoneal adhesions and prostatitis.

Contraindications of Short-wave diathermy .

Short-wave diathermy is contraindicated in

1. presence of pregnancy .
2. cardiac pacemaker .
3. Hemorrhage .
4. Thrombosis .
5. Peripheral vascular diseases .
6. Metal implants .
7. Impaired sensations .
8. Anesthetic areas .
9. Malignancy following X-ray therapy .
10. Epileptic patients .
11. Mentally retarded patients .
12. patients who are unable to communicate( unconsciousness) and those with fever( Pyrexia ) .

Precautions for Short-wave diathermy .

Major precautions, should be taken while treating patients with hearing aids, contact lenses and electrophysiological orthoses.

1. Contact lenses should be removed before the treatment in the vicinity of head, neck and face region.
2. Electrophysiological orthoses and hearing aids can be switched off or removed during the treatment.
3. It is also important to keep transistorized units, such as transcutaneous electrical nerve stimulator (TENS) units, muscle stimulators, phones, mobiles, electronic calculators, electronic watches, interferential therapy unit and electronic traction devices at least 5 to 10 feet away from the short-wave diathermy machine.

Dosages of Short-wave Diathermy .

In acute conditions, short-wave diathermy is applied for 5 to 10 minutes once or twice daily and in chronic conditions, it is applied for 20 to 30 minutes.  Intensity should be chosen in such a way that it produces mild, comfortable and perceptible warmth. In other words, it should raise the temperature of the tissues to safer therapeutic range, which is 40 to 45ºC.

In the past, the dosages were chosen from four levels.

1. Level I: Unnoticeable heat .
2. level II: Slightly noticeable heat .
3. level III: More noticeable heat .
4. level IV: Very noticeable heat.

Physiological Effects of Short-wave diathermy .

The main physiological effect of short-wave diathermic current on the body tissue is heat production and other physiological effects result from the increase in temperature.

1. Temperature .

Short-wave diathermy application produces heat in the body tissues. Increase in local temperature may occur due to the production of heat. But, if the short-wave diathermy is applied for a prolonged time, then there is a rise in general body temperature by a few degrees. The general rise in body temperature occurs due to blood that passes through the tissues in which the rise of temperature has occurred. The heated blood carries heat to other parts of the body.

2. Metabolism .

Metabolism is the collective process by which the living status of tissues of the body is maintained. When short-wave diathermy is applied to the body tissue, it produces heat. Heat production in the body tissues increases metabolism. This may occur as per the Van’t Hoff statement. Van’t Hoff has stated that any chemical change capable of being accelerated by heat is accelerated by rise in temperature.

3. Blood Supply .

Short-wave diathermy application increases local blood supply. Increase in blood supply may occur due to the direct effect of heat on the vessels in terms of vasodilation. This vasodilation may occur indirectly due to the action of metabolites on the vessel walls. Metabolites and other waste products produced is increased due to the increase in metabolic activity. Due to increased vasodilation, there is an increase in the lumen of the vessels, which leads to increased blood supply. Strength-Duration Curves

4. Effect on Nerves .

Mild heating due to short-wave diathermy application may reduce the excitability of the nerves, especially sensory nerves.

5. Muscle Relaxation .

Rise in temperature induces relaxation of muscles and increase their efficacy of action. The muscle fibers contract and relax very easily, but strength of the contraction is unaffected.

6. Tissue Damage .

Excessive heating due to short-wave diathermy application may cause damage to the tissues in the form of coagulation or thermal burns.

7. Blood Pressure .

Prolonged application of short-wave diathermy can reduce blood pressure. This happens due to reduction in peripheral resistance to the flow of blood, which is due to generalized vasodilation and reduction in viscosity of the blood.

8. Sweating . 

Increase in the local and general temperature can cause increased sweating either in the local region of heating or generalized area, depending on the extent of heating.

Therapeutic Effects of Short-wave diathermy .

1. Pain Relief .

Short-wave diathermy is one of the effective modalities in relieving musculoskeletal pain. The exact mechanism of pain relief is not known. But it may occur due to the sedative effect of short-wave diathermy on sensory nerves, counter-irritation by heat, resolution in inflammation, and the relief of underlying muscle spasm. However, in very acute conditions (less than 72 hours of onset) short-wave diathermy application may increase the pain due to increase in the inflammatory process.

2. Muscle Spasm .

Short-wave diathermy can induce the muscle relaxation and hence, it can be used in the treatment of muscle spasm.

3. Joint Stiffness .

Short-wave diathermy can minimize joint stiffness due to increased extensibility of connective tissue as a result of increase in local temperature and due to the relief of pain, spasm and inflammation. Usually, short-wave diathermy is used in the treatment of deep joints where superficial heating modalities may not be effective because of their smaller depth of penetration. In order to make use of this effect, short-wave diathermy should be applied prior to manual therapy.

4. Inflammation .

Increase in the blood supply also increases white blood cells, antibodies and other essential nutritive materials. Increase in all of these may help in resolution of inflammation. Short-wave diathermic application can minimize or resolve subacute and chronic inflammation. It may resolve or minimize acute inflammation, provided it is applied at the precise time following the onset of acute inflammation (after 72 hours) with right dosages, otherwise it can aggravate the acute inflammatory process.

5. Musculoskeletal Trauma .

Short-wave diathermy accelerates healing by increasing the amount of nutritive materials required for healing following musculoskeletal trauma.

Advantages of Short-wave Diathermy .

Heat is produced in the body tissue and not transmitted through the skin, localization of heat can be done by careful placement of electrodes, deep heating is possible. There is no discomfort to the patient as high frequency current of short-wave diathermy does not stimulate sensory and motor nerves and treatment can be controlled precisely.

Pulsed Short-wave Diathermy .

In pulsed mode of short-wave diathermy, the output of high frequency current commences and ceases at regular intervals. In other words, the output is applied in form of a series of short bursts. Pulsed short-wave diathermy is also called pulsed electromagnetic energy, pulsed peak power, diapulse, etc. In 1930s, pulsed shortwave diathermy was invented, but it became popular after 1950. Pulsed short-wave diathermy produces non-thermal effects mainly.

As a result, there is no appreciable heat developed during the treatment. Pulsed short-wave diathermy increases the cellular activity, reabsorption of hematoma, and the repair process. But it reduces inflammation, and swelling. Various parameters of pulsed shortwave diathermy include pulse duration, pulse repetition, intensity or pulse peak power, mean power, etc.

The treatment duration of pulsed short-wave diathermy ranges from 15 to 60 minutes. Indications and contraindications are more or less same as that of continuous shortwave diathermy .

 

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