Interferential Therapy

Lesley McLoughlin

Session content Introduction Definition Physical characteristics Therapeutic uses Treatment regimes Practical application Contra-indications Dangers

Introduction

Widely used electrotherapy modality Used since the 1950s to utilise the

therapeutic aspects of low frequency currents without the discomfort

Definition Two medium frequency currents of slightly

differing frequency are applied to the body in such a manner to produce;

an amplitude modulated medium frequency current within the body.

Amplitude modulation provides a beat frequency that is within the biological frequency range

Therapeutic Uses

Relief of pain – pain gate theory 80-140Hz (higher IFT frequencies) Stimulates Aβ fibres To inhibit impulse transmission in A∂

and C fibres Used for both acute and chronic pain Temporary pain relief

Therapeutic UsesRelief of pain – Ascending pain suppression, 2-30Hz (lower frequencies)

Stimulates A∂ fibres: To inhibit C fibre transmission Via the release of encephalins and

endorphins More longer lasting pain relief Only effective on chronic pain

Therapeutic Uses

Reduction of oedema 0-100 Hz Stimulates autonomic nerves to

produce vasodilatation Increases circulation

Therapeutic Uses

Motor stimulation 0-25 Hz - twitch 25-100 Hz - muscle contraction Can be used to treat incontinence

or muscle weakness secondary to trauma/surgery (in conjunction with active exercise).

Suggested treatment regimes

Pain80-140 Hz 15 minutes4 Hz constant 15 minutes

Circulation0-100Hz 20-30 minutes

Suggested treatment regimes

Muscle stimulation10-50 Hz 15 minutes50Hz constant with surge

IncontinenceStress incontinence - 10-50Hz, surge 15 minutes.Urge incontinence - 5-10Hz 10 minutes

Practical application Machine check - plugs, cable, electrodes etc. Test machine Position patient comfortably Explain nature of the treatment, what they will

feel and the benefits Prepare and wash the skin Inspect skin for any lesions - cover with

petroleum jelly

Practical application

Interferential with suction electrodes

Interferential with malleable electrodes

Preparation of the skin Skin has a high electrical resistance as the

outer surface is dry and contains few conducting ions

Skin is normally washed to remove excess oils and to moisten it

Any lesions can cause a concentration of current which will result in pain

Small lesions can be insulated with petroleum jelly

Practical application.

Position electrodes - must be moistened The four electrodes are arranged in two

circuits - apply to the patient at right angles to each other

If using two electrodes only, use the yellow (variable) circuit

Electrodes are attached by suction or bandages/ elastic straps

Suction electrode application

Suction machine

Suction electrodes with moistened sponges

Malleable electrode application

Interferential machine set up with malleable electrodes

Malleable electrodes in moistened sponge pockets

Electrode placement

Electrodes placed so that the two circuits produce an interferencecurrent and the patient experiencesthe tingling sensation on and around the site of their problem

Left knee

Practical application.

Give the patient a warning - will feel a tingling sensation which should not be uncomfortable or burn

Select the frequency required Increase the intensity - may need to

adjust due to accommodation Turn the machine off after treatment

completed

Select treatment parameters

•Power on

•Time

•Base & peak frequency

•Swing pattern

•Output

Termination of treatment

Remove electrodes Inspect the skin

Contra-indications

Acute sepsis - ↑ risk of spread of infection Tumours - ↑ risk of increased growth of

activity Pregnancy – no treatment over uterus or its’

nerve supply Cardiac disease – no treatment over the

heart, cervical ganglia or vagus nerve

Contra-indications

Cardiac pacemakers Febrile conditions Large open wounds Menstruation - ↑ risk of bleeding or pain if

treating abdominal of lumbar region Dermatological conditions Thrombophlebitis – risk of embolus being

dislodged

Contra-indications Severe ↑ or ↓ BP – avoid lower cervical

region – BP control via cervical ganglia Acute inflammation, oedema, haemorrhage or

haematoma when using suction cups Hypersensitivity or fear of electrical treatment Patients who are unable to understand the

treatment or what is required of them

Possible dangers Burns – high intensity currents can

cause sufficient heating to cause a burn. The patient should be given warnings which include the word BURN

Mains current shock – faulty equipment Electric shock – abrupt application of

high intensity current – turn current up/ down slowly

References Low J. and Reed A. (1992)

Electrotherapy Explained: Principles and Practice. Oxford

Watson T. (2000) The role of electrotherapy in contemporary physiotherapy practice. Manual Therapy Aug:5(3);132-41