The basic rule of Interferential Therapy (IFT) is to employ the significant physiological effects of low frequency (<250pps) electrical stimulation of nerves without unpleasant side effects. Recently, many ‘portable’ interferential units have become easily available. Despite their size, they can accurately deliver ‘proper’ interferential therapy, yet some have limited functionality and ability for the professional to ‘set’ all parameters. Interferential Therapy(IFT) may be defined as the use of two medium frequency current around 4000hz to evoke interference current between 1Hz to 1000Hz.
Electrotherapy involves applying a device to use electrical energy to a patient’s body to encourage healing in muscle and other body tissues. It is necessary to consider the indications and contraindications of Interferential therapy before dealing with patients, as there are scenarios to avoid.
To build low-frequency effects at a satisfactory intensity and at sufficient depth, patients will experience considerable discomfort in the superficial tissues. This is for the impedance of the skin to be inversely proportional to the frequency of the stimulation. The barrier presented by the skin to passaging an electric current is more complex than just impedance or resistance. The lower the stimulation frequency, the greater the impedance to passaging the current and more discomfort experience as the current passes into the tissues against this barrier.
The skin impedance at 50Hz is approximately 3200, whilst at 4000Hz it will be almost 40. The result of giving a higher frequency is that it will pass more easily through the skin, requiring less electrical energy input to reach the deeper tissues & giving rise to less discomfort.
Physiological effect of IFT
Some suggest that IFT works in a ‘special way’ because it is ‘interferential’ as opposed to ‘normal’ stimulation. The evidence for this special effect is lacking, and it is most likely that IFT is just another means by which it can stimulate peripheral nerves. It is rather a generic means of stimulation—the machine set up to act more like a TENS type device or more like a muscle stimulator—by adjusting the stimulating (beat) frequency. I often regard it (by patients) to be more acceptable as it generates less discomfort than some alternative forms of electrical stimulation.
- Increase blood circulation
- Vasodilation
- Remove wastes substances
- Increase muscle stimulation
- Increase metabolic rate
- Reduction of oedema
- Relief of pain
- Decrease blood pressure
Indication of IFT
The clinical application of IFT therapy is peripheral nerve stimulation. Selection of a wide frequency sweeps considered frequency range of 1-100Hz, we can cover the effective treatment of these frequencies. The following main clinical applications of IFT :
- Pain – Both case of pain and referred pain- e.g.- Migraine, Vascular insufficiency, Stump complication, Neuralgia
- Muscle spasm
- Oedema
- Hematoma
- Chronic ligamentous lesion
- Trigger spot
- Stress incontinence – contraction of pelvic floor muscle
- Delayed union – in case of fracture to stimulate the union
Contraindication of IFT
IFT is a popular pain-relieving modality in rehabilitation because it has broadly applicable use without side effects that oral painkillers and anti-inflammatory medications may cause. As with any therapeutic modality, IFT has a list of contraindications-
- Arterial disease
- Deep vein thrombosis
- Infective condition
- Pregnant uterus
- Danger of hemorrhage
- Malignancy
- Pacemaker
- During menstruation
- Febrile condition
- Large open wounds
- Unreliable patient
- Dermatological condition
Danger of IFT
Electrode positioning should ensure adequate coverage of the area for stimulation. Using larger electrodes can minimize patient discomfort whilst small, closely positioned electrodes increase the risk of superficial tissue irritation and skin burn.
- Shock
- Burn.
