Phys Agents Diathermy

Clinical Considerations

• What is the clinical outcome being looked for?

• What is the target tissue?

• Will this intervention help with exercise?

What is Diathermy?

Application of high frequency electromagnetic energy

• Generates heat in body tissue

• But can also be non-thermal

Why use Diathermy?

• Deep tissue heating

• Decrease pain

• Decrease muscle guarding

• Increase tissue extensibility

• Prepare for exercise

Thermal Effects

• Vasodilation

• Increase circulation

• Increase tissue temperature

• Increase tissue extensibility

• Decreased muscle guarding

Why Deep Heating?

• Large muscle areas

• Chronic stiffness

• Deep joint restriction

• Mobility limitations

Diathermy vs Ultrasound

• Larger treatment area

• Less observation requirement

• Larger, regional heating

• Static (doesn’t need to move) application

Shortwave vs Microwave

Shortwave: 3 kHz - 300 MHz, 1 - 300 m wavelength

Microwave: 300 MHz - 300 GHz, 10 mm - 1 m wavelength

Shortwave Diathermy (SWD) 3 frequencies

13.56 MHz - 22 m

27.12 MHz - 11 m

40.68 MHz (rarely used)

Physiologic Response to Diathermy

Does not depolarize peripheral nerves/contract muscle because frequencies are too high

Heating with Short Wave Diathermy

• Vibration of charged molecules

• Rotation of dipolar molecules

• Distortion of non-polar molecules

Diathermy Key Factors

• Prescribe power and time, not a specific tissue temperature (like ultrasound)

• Heating = current² x resistance

• Not reflected by bone and does not concentrate in tissue (lower risk of burning than ultrasound)

• Heat deeper than hot packs and larger area than ultrasound

Inductive Coil

• Frequency: 48W at 27.12 MHz

• Magnetic field produces eddy current in tissue which causes charged particles in tissue to oscillate and cause friction/heat

• Patient in magnetic field not part of circuit

• Fat does not provide as much resistance to em energy, whereas high electrolyte tissue (muscle, blood) respond better

• Not as much superficial sensation of heat with electromagnetic capacitive plates

Does distance matter?

The closer the tissue is to an inductive coil, the stronger the magnetic field, the greater the induced eddy current, and greater the heating

Fat is still at risk of burning because:

still close to applicator and not as well vascularized so not efficiently cooled

Dosage Parameters

Dose I (5W): No sensation of heat

Dose II (12W): Mild heating sensation

Dose III (24W): Moderate/pleasant heating sensation

Dose IV (48W): Vigorous heating that is tolerable below pain threshold

Rebound Diathermy

• 34W at 13.56 MHz

• Form of inductive type diathermy

• Smaller, lighter and more portable

• Provides circumferential heating by utilizing special sleeve that patient wears

• Operates at low power level, making it usable for prolonged use at both thermal and non-thermal settings

• Easy to use

• Cheaper units

• Needs longer treatment time to get vigorous heating

Capacitive Plates

• Consists of metal plates encased in plastic or rubber

• High frequency AC flows from 1 plate to other, going through patient at part of circuit

• Heat amount determined by Strength and density of current, superficial vs deep tissues, conductivity of tissue

Capacitive Plates (Pads)

• Must have uniform contact

• Spacing equal to cross sectional diameter of pads

  • Increasing space will increase depth of penetration and decrease current density

• Pads centered on target treatment location

• Good for superficial soft tissue

Nonthermal Effects (Pulsed)

• Increases microvascular perfusion

• Affects ion binding and transport across cell membrane. Triggers biological processes

• Alters Ca binding

• 5W

Nonthermal effects

• Decrease pain

• Decrease edema

• Increase tissue healing

• Lymphedema, CVA, CRPS (chronic regional pain syndrome)

• Best in acute stages

Contraindications

General

• Metal implants

• Pregnancy

Thermal

• Malignancy

• Eyes, testes, growth plates

Nonthermal

• Deep tissue

• Substitute for conventional therapy for edema and pain

• Metal implants

• Electronic devices

Precautions

General

• Near electronic or magnetic equipment

• Obesity (high fat)

• Copper bearing IUD

Nonthermal

• Pregnancy

• Skeletal immaturity

To the therapist

• Exposure

• Pregnancy

Clinical Safety

Before treatment ask:

• Any implanted devices?

• Pregnancy?

• Altered sensation?

• Ability to report heating?

• Excess adipose tissue?

How to use Diathermy

• Position applicator directly over tissue

• Position drum perpendicular to body part

• Allow small air gap for heat dissipation (2-3cm)

• Use towel layer to absorb moisture

• Instruct patient not to move

• If using capacitive plates, equal distance apart

• Skin needs to be dry

Documentation

• Area treated

• Hz, power setting, pulse rate, time

• Type of applicator

• Treatment duration

• Patient position

• Distance of applicator from patient

• Patient response to treatment

Duration

10-20 minutes