By

Ass.Prof.Dr. Gehan Mosad

At the end of the lecture the student should be able to:

Define diathermy Know types of diathermy Identify the physical properties of

diathermy Know thermal and non-thermal

effects of diathermy Know indications and

contraindications of thermal and non thermal diathermy

Diathermy

Diathermy, from the Greek meaning, it means "through heating"

It is the application of high frequency electromagnetic energy that is used to generate heat in body tissue.

Types of Diathermy Shortwave Microwave

Physical properties of diathermy

1- Frequency: Short wave frequency is 10 -100 MHz Microwaves frequency is 300 MHz to

300 GHz)2- Wave length: Short wave is 3 -30 m. Microwaves is1 mm to 1 m.3- Both shortwave and microwave

radiation are nonionizing.

Physical properties of diathermy (cont.)

4- Both short wave and micro waves can be delivered either continuous or pulsed.

When delivered in continuous mode at a sufficient average intensity can generate heat in the body.

When delivered in a pulsed mode at low average intensity, heat is dissipated before it can accumulate

5- Pulsed low-intensity electromagnetic energy in the shortwave or microwave produces a number physiological effects by nonthermal mechanism.

Physical properties of diathermy (cont.)

An increase of tissue temperature depends on the amount of energy absorbed by the tissue. This is determined by:

- Intensity of the electromagnetic field. - Type of tissue to which the field is

applied.

Pulsed signals can dissipate heat during the off cycle.

PSWD deliver very short pulses to avoid any cumulative increase in tissue temperature.

Advantages of Diathermy

Diathermy has a number of advantages over other thermal agents:

It can heat deeper layer, than other thermal agents as infrared and hot packs

It can heat larger areas than ultrasound. SWD is not reflected by bones and therefore

does not concentrate at the periosteum or cause risk of periosteal burning, as does ultrasound.

Both SWD and MWD treatments generally need little time for application and do not require the clinician to be in direct contact with the patient throughout the treatment period.

Types of Diathermy Applicators

There are three different types of diathermy applicators: inductive coils, capacitive plates, and a magnetron

Inductive coils and capacitive plates are used to apply SWD.

Magnetron is used to apply MWD.

Effect of diathermy

Thermal effects Non thermal effects

Thermal effects (continuous shortwave)

When SWD & MWD applied at sufficient intensity, they increase tissue temperature which leads to the following physiological effects:

vasodilatation increased rate of nerve conduction decrease pain acceleration of enzymatic activity increased soft tissue extensibility increase cutaneous circulation Increase muscular circulation.

Non thermal effects (pulsed shortwave)

When applied at a low average intensity, with a short pulse duration, diathermy doesn't produce any maintained increase in tissue temperature because any transient heat of tissue is dissipated by the blood perfusing the area during off time of the pulse.

Although the mechanism of the following physiological effects is unknown, it has bee suggested that they are due to modification of ion binding and cellular functions by the incident electromagnetic field and the resulting electric current.

Non thermal effects (cont.)

B- Altered cell membrane function and cellular activity.

Electromagnetic fields can affect ion binding to the cell membrane, which can trigger a series o f biological processes including:

Activation growth factor in fibroblasts and nerve ce1ls,

Macrophages activation, Change in myosin phosphorylation, Regulation of the cell cycle by altering calcium

ion binding, Stimulation of ATP and protein synthesis.

Non thermal effects (cont.)

B- Increase local micro-vascular perfusion

Increase local tissue oxygenation. Increase tissue nutrients. Increase phagocytosis Increase healing rate of ulcers.

Clinical Indications of Diathermy

Thermal level diathermyUsed in management of chronic conditions control of pain accelerate healing rheumatic pain Chronic sprains and strains Decrease joint stiffness in large, deep

structures such as hip joint or diffuse area of the spine.

Improve joint function (ROM), if applied in conjunction with stretching.

Clinical Indications of Diathermy (cont.)

Non thermal levelUsed in management of acute

conditions Control of pain and edema Pain control Wound healing Nerve healing Bone healing Management of neuropathy

Contraindications of Diathermy

Thermal diathermy acute inflammation and infection metal (implants or external) pacemaker malignancy pregnancy eyes testes growing epiphysis sever circulatory impairment impaired thermal sensation

Contraindications of Diathermy (cont.)

Non thermal diathermy metal (implants or external) pacemaker malignancy pregnancy eyes testes growing epiphysis.