Diathermy Lecture IV

Dr. Amal HM Ibrahim

Professor of Physical Therapy

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Diathermy

• Application of High-Frequency Electromagnetic Energy

• Used To Generate Heat In Body Tissues

• Heat Produced By Resistance of Tissues

• Also Used For Non-Thermal Effects

The electromagnetic

spectrum

• Dia means through and Thermo means temperature heat.

• Short wave diathermy (SWD), or radio frequency (RF), is used to penetrate deep into the body tissues to stimulate blood flow and to heat the treated area.

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Diathermy Heating

• Doses Are Not Precisely Controlled Thus The Amount of Heating Cannot Be Accurately Measured – Basically means amount of heating

patient receives cannot be directly measured

• Heating= Current2 X Resistance

Shortwave Diathermy

• SWD is electrical field that oscillate at varying frequencies and different wavelength and is applied to a patient by capacitor field or coil field treatment.

Shortwave Diathermy

• The SWD machines used by physical therapist utilize the frequency of 27.12 MHz and wavelength greater than 11meter

Shortwave Diathermy

• To apply SWD we have two main circuits, the machine circuit which produce high frequency current coupled with the patient circuit through inductors to transfer the electrical energy to the patient.

Electromagnetic Phenomena

• Electromagnetic phenomena can be considered from two different aspects:

• 1- Electrostatic field .

Electromagnetic Phenomena

2- Electromagnetic field

Description

• High-frequency electrical currents

– Radio waves

• Pass through the tissues

• Cause molecular vibration

• Results in deep heating

• Capable of heating large volumes of tissues

• Causes both thermal and nonthermal effects

Uses

Thermal Effects

(Contenous)

• Deep heat

• Increased blood flow

• Increased cell metabolism

• Increased tissue extensibility

• Muscular relaxation

• Possible changes in

• enzyme reactions

Non-thermal Effects

(Pulsed)

• Edema reduction

• Lymphedema reduction

• Superficial wound healing

• Treatment of venous stasis ulcers

Types of Shortwave

Diathermy

• Induction Field

• Capacitive Field

Induction Field Diathermy

• Places the patient in the electromagnetic field

• Selectively heats muscle

• Also referred to as: – Condenser field diathermy

– Magnetic field diathermy

Induction Field Diathermy

(Cont.)

• A coil is housed within a drum

• Current flowing within the coil produces a rotating magnetic field

• Magnetic field produces eddy currents in the tissues

• Eddy currents cause friction that produce heat

• Although rare, cables are sometimes used in place of drums

Capacitive Field Diathermy

• Uses the patient’s tissues as a part of the circuit

• The tissues’ electrical resistance produces heat

• Selectively heats skin

• Muscle is heated via conduction from the adipose

• Also referred to as “condenser field diathermy”

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Capacitor (Condenser) Electrodes

• Create Stronger Electrical Field Than Magnetic Field

• Ions Will Be Attracted Or Repelled Depending on the Charge of the Pole

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Capacitor Electrodes

• Electrical Field Is The Lines of Force Exerted on Charged Ions That Cause Movement From One Pole To Another

• Center Has Higher Current Density Than Periphery

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Capacitor Electrodes

Patient Is Between

Electrodes and Becomes

Part of Circuit

Tissue Is Between

Electrodes in a Series

Circuit Arrangement

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Electrical Field

• The Tissue That Offers The Greatest Resistance To Current Flow Develops The Most Heat – Fat Tissue Resists Current Flow

– Thus Fat Is Heated In An Electrical Field

– Precaution: electrical field may overheat

area with large fat content

Modes of Application

Continuous

• Increases tissue temperature

• Increased risk of burns

Pulsed

• May or may not increase temperature

• Pulses allow for increased treatment intensity and duration

• Not the same as “nonthermal”

1- Pain relief: of traumatic pain and rheumatic conditions affecting muscles, ligaments and joints.

2-Muscle spasm: may be reduced directly by SWD.

3- Inflammation: resolution of inflammation as a result of increase blood supply.

4- Accelerate wound healing: by increase coetaneous circulation.

5- Infection: increase circulation and increase white blood cells and antibodies.

6- Fibrosis: increase extensibility of fibrous tissues such as tendons, joint capsule and scars.

Contraindications

• Metal implants or metal jewelry

• Cardiac pacemakers

• Ischemic areas

• Peripheral vascular disease

• Perspiration and moist dressings: The water collects and concentrates the heat.

• Tendency to hemorrhage, including menstruation.

• Pregnancy

• Fever

Contraindications

• Sensory loss

• Cancer

• Areas of particular sensitivity:

– Epiphyseal plates in children

– The genitals

– Sites of infection

– The abdomen with an implanted intrauterine device (IUD)

– The eyes and face

– Application through the skull

• Six main variations in electrodes are commonly available:

1. Flexible pads: consist of metal electrode encased in rubber and produce an electrostatic field.

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Capacitor Electrodes (Pad Electrodes)

• Greater Electrical Field

• Patient Part of Circuit

• Must Have Uniform Contact (toweling)

• Spacing Equal To Cross-sectional Diameter of Pads

• Part To Be Treated Should Be Centered

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Pad Electrodes

• Increasing The Spacing Will Increase The Depth Of Penetration But Will Decrease The Current Density

• Capacitive Method Good for Treating Superficial Soft Tissues

2- Space plates: consist of a rigid metal electrode encased in a Perspex cover electrostatic field.

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Air Space Plate Electrodes

• Area To Be Treated Is Placed Between Electrodes Becoming Part of Circuit

3- Coil: or cable electrode consists of a wire with plugs at either end electromagnetic field.

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Induction Electrodes

• Passing Current Through A Coiled Cable Creates A Magnetic Field By Inducing Eddy Currents (small circular electrical fields) That Generate Heat

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Induction Electrodes (Cable Electrode)

• Two Arrangements:

– Pancake Coils

– Wraparound Coils

• Toweling Is Essential

• Pancake Coil Must Have 6” in Center Then 5-10cm Spacing Between Turns

• Best Frequency

• 4- The monod: flat, rigid coil encased in Perspex cover electromagnetic field.

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Induction Electrodes (Drum Electrode)

• One Or More Monopolar Coils Rigidly Fixed In A Housing Unit

• May Use More Than One Drum Depending On Area Treated

• Penetration

– Deeper Soft Tissues

• Toweling Important

5- The minode: conical rigid coil encased in Perspex cover electromagnetic field.

6- The diplode: or drum electrode, consists of a flat coil electrode encased in a Perspex cover with two wings electromagnetic field

1- Spacing: allows the lines of force in the electrostatic field to diverge before entering the tissues. This prevents concentration of heat in the super-facial tissues and ensures more heating through the part.

• Spacing provided by: 1- wrapping flexible pads in towel. 2-flat felt spacing pads between pad electrode and skin. 3-air when using space plates.

• a- Normal spacing even field distribution.

• b- Increased spacing deep field concentration.

• c- Decreased spacing superficial concentration.

• It has been suggested that for most short wave sources at maximum output spacing of about 4 cm to the maximum that will give the greatest absolute heating of the deep tissues.

• Conversely the minimum skin electrode distance is about 2 cm.

• Note: the spacing refers to the distance of the metal electrode, not the plastic cover, from the skin.

2- Air in cavities: as sinuses or uterus, the lines of force deviate to avoid air as it offers a high resistance. As a result only the sides of air cavity will be heated.

3- Electrode size: if the electrodes are too small than the diameter of treated part line of force will be concentrated superficially.

• -If the electrodes are markedly larger the line of force will be lost in the air.

3- Electrode size:

• -Ideally, the electrodes should be slight larger than the area treated.

4- Metal: metal causes the lines of force to concentrate on the metal

• -Is short wave at the frequency of 27.12 MHz, which is pulsed at a rate, selected by the therapist.

• -The pulse frequency range is from 15 to 200 Hz.

• -The maximum intensity is 1000 watts.

• -The pulse duration is constant at 0.4 ms in square pulse.

• -The advantage of pulsed S.W.D. is that a very high intensity of power can be administered with minimal effect.

Biological Effects 1-Increased metabolism.

2-Relief of pain.

3- Stimulated wound healing.

4- Relaxed muscle spasm.

5- Accelerated wound healing.

6- Decreased haematoma formation.

2- Indications 1- Sprains.

2- Contusions.

3- Haematoma.

4- Bursitis.

5- Sinusitis.

Microwave Diathermy

Properties of Microwave

Diathermy

• Microwave diathermy (MWD), is a form of electromagnetic radiations (part of electromagnetic spectrum), lying between shortwave and infrared waves. The microwaves diathermy gives superficial heating where energy is first absorbed at the surface of the body (skin) and a part of it penetrate and absorbed in deep tissues.

Properties of Microwave

Diathermy

The general frequency of microwave is between 300 to 30000MHz with wave length of 10mm to 1 meter.

The therapeutic microwave generators used frequency of 2450MHz with wave length of 122.5mm.

Directors Used in Microwave

Applications

• There are different shapes of directors used in microwave applications:

Directors Used in Microwave

Applications

• Large circular field director: the effective diameter is 200mm. The heating pattern is more intense around the outer portion than the centre. The power output range is up to 250 watts.

Directors Used in Microwave

Applications

• Small circular field director: the effective diameter is 100 mm. the heating pattern is more intense around the outer portion than in the center. The power output is up to 25 watts

Directors Used in Microwave

Applications

• Longitudinal director: the effective treatment area is 500mm by 100mm. the heating pattern tends to be more concentrated in the center of this area. The power output is up to 250 watts

1. Relief of pain: by microwave diathermy is

useful in the treatment of traumatic and rheumatic conditions affecting superficial muscles, ligaments and small superficial joints.

2. Reduce muscle spasm: may be reduced directly by microwave diathermy or may be reduced by relieving of pain.

3. Inflammation: increase in the blood supply will increase venous return from the inflamed area and aids the re-absorption of edema exudates.

Dosage of MWD

• Duration of treatment 20 minutes is the optimum.

• :Intensity: the patient should feel mild and comfortable warmth.

• Frequency: daily or on alternating day.

Indications of MWD

1- Musculoskeletal disorders:

• Sprain- strain – muscle and tendon tear – degenerative joint disease- joint stiffness in superficial joints- capsular lesions.

2- Superficial inflammatory or infective conditions :

• Tenosynovitis – bursitis – synovitis – infected surgical incisions – carabuncles – abscess.

Contra-indications

Over malignant tissues.

Over ischemic tissues.

Moderate and excessive edema.

Over wet dressings and adhesive tapes.

Metal implants.

Pacemaker.

Over growing bone.

Male gonads: repeated radiations can cause sterility.

Contra-indications

Hemorrhage.

Tuberculosis joints.

Impaired thermal sensation.

Unreliable patients.

The eyes: cause cataract.

Recent radiotherapy.

Hypersensitivity to heat.

Acute infection or inflammation.