Interferential Therapy

Interferential Therapy

Interferential Therapy  Interferential therapy is a form of electrical treatment in which two medium-frequency currents are used to produce a lowfrequency effect.  the transcutaneous application of alternating medium-frequency electrical currents, which are slightly out of phase through the tissues, amplitude modulated at low frequency for therapeutic purposes such as relief of pain, improve circulation and

Carreir Currents

Constructive Interference Beat Frequency Cuurent

Destructive Interference

 skin impedance is inversely proportional to frequency  ohmic resistance - a material's opposition to the flow of electric current; measured in ohms  Ohmic resistance is developed due to skin and depends on following factors:  Ohmic resistance is inversely proportional to the size of the electrodes used.  Ohmic resistance is directly proportional to the dryness of the skin.  Ohmic resistance is directly proportional to the hairy

Production of Interferential Current  Interferential current is essentially a medium-frequency current that rhythmically increases and decreases in amplitude at low frequency  The principle upon which interferential therapy is based is that which produces the interference effect where two medium frequency currents cross in the patient’s tissues.

 Two medium

frequency currents are used to produce the interferential current. They are known as carrier waves as they do not produce muscle nerve stimulation and are just used to get the greater depth of penetration and to produce the

 Interferential current is produced by mixing two medium-frequency currents that are slightly out of phase, either by applying them so that they interfere within the tissues, or alternatively by mixing them within the stimulator prior to application (premodulated current).  Theoretically, the two currents summate or cancel each other out in a predictable manner, producing the resultant amplitude-modulated

 The frequency of the resultant current will be equal to the mean of the two original currents, and will vary in amplitude at a frequency equal to the difference between these two currents. This later frequency is known as the amplitude-modulated frequency (AMF) or beat frequency.

Area of Interference:  It is the area where interferential current is set-up. The pattern of the interferential area may be static or dynamic.

Amplitude-Modulated Frequency (AMF) or Beat Frequency:

 AMF is defined as the difference between the frequencies of the two medium-frequency currents, which is produced in the tissues at the point where the two currents cross.  Amplitude of AMF is always higher than the amplitude of the two medium-frequency currents.

Amplitude-Modulated Frequency (AMF) or Beat Frequency:

 Most IF machines allow a constant AMF to be selected, e.g. 10,50 or 100 Hz  This is called Constant or Static mode.  Some machines allow the AMF to change automatically & regularly b/w some preset pair of frequencies over a specified time period. This is variously called a Frequency Modulation, swing or Sweep.

Static AMF

INTERFERNTIAL CURRENT  Clover leaf pattern is bacically the theoretical distribution of current in a homogenous medium  In reality this neat uniformity cannot takes place b/c of the heterogeneity of tissues  This represents the static pattern and called STATIC AMF.  This pattern is used for treating smaller areas

INTERFERENTIAL CURRENT  By varying the current intensity in the two circuits with respect to each other, it is possible to move the clover leaf pattern to and fro through 45 degrees, this gives a more uniform total distribution of the IFC in the tissues  This pattern is used for the treatment of larger areas.

Methods of application

Quadripolar / Bipolar Application  Interferential currents may be produced either by applying the two medium frequency currents via four electrodes (quadripolar method) so that they intersect in the tissues, or alternatively by mixing the two currents in the stimulator prior to application via two electrodes (premodulated or bipolar method).

Quadripolar  A quadripolar application of interferential current produces modulated current in a clove leaf pattern, with leaves set up at right angles to the two medium frequency currents.  Quadripolar interferential current is produced deep inside the tissues (AMF is produced endogenously); hence there is lowered skin impedance. Thus it is used to treat larger areas.

 Bipolar Application  Bipolar interferential current will be distributed similarly to conventional electrical stimulation, with maximal current intensities underneath the electrodes, progressively decreasing with distance.  Bipolar interferential current is produced inside the machine (AMF is produced exogenously); hence there is increased skin impedance. Thus it is used to treat localized area or smaller areas.

INTERFERENTIAL THERAPY PHYSIOLOGICAL OBJECTIVES  Pain relief both acute and chronic  Reduction of edema  re-education and strengthening of muscle.  Stimulation and improvement of circulation  General facilitation of healing

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INTERFERENTIAL THERAPY  The generally accepted range of frequency is 0 to 150 Hz, with a low range from 0 to 10 Hz, commonly accepted as the appropriate treatment for increasing local blood circulation; and a high range from 80 to 150 Hz which is used for pain relief. 20

INTERFERENTIAL THERAPY CONTRAINDICATIONS  Pacemakers  Thrombosis  Cardiac Conditions  Bacterial Infections  Malignancy

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INTERFERENTIAL THERAPY WARNINGS  Pregnancy  Implants of any electrical nature  Transcerebrally  Skin diseases

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Application in Different Conditions

OR

How is IFC different than a TENS unit in relation to pain reduction?  TENS (Transcutaneous (through the skin) Nerve Stimulation) is strictly a non-

invasive (any procedure that does not penetrate the skin or a cavity) pain management tool. TENS stimulates peripheral nerves (the nerves which supply the musculoskeletal system and surrounding tissues) producing a tingling sensation that interferes with pain. TENS masks pain by blocking nerve impulses on the sensory nerve (nerves that convey impulses to the brain and spinal cord) (Gate Control Theory (the hypothesis that painful stimuli may be prevented from reaching higher levels of the central nervous system (spinal cord and/or brain) by stimulation of larger sensory nerves which will block or prevent the sensory nerves from sending pain signals effectively to the brain).  TENS, has no other physiological (the normal process of the body as opposed to abnormal or pathological functions) effect. TENS delivers nerve stimulation transcutaneously. The increased sensory activity activates cells in the dorsal (pertaining to the back or lower part of an organ) horn of the spinal cord , closing the gate to pain transmission along the fibers that send pain response’s to the brain. Accommodation (dependency on a device) and habituation (becoming used to something) with reduced or eventual noneffectiveness are concerns when TENS is used for an extended period of time. Since the stimulation parameters (settings or guidelines) are limited or kept constant, the patient can/will adapt to minimally changing or unchanging stimulus (anything which excites functional activity in an organ  or body part). When this happens the TENS unit will no longer be as effective for the patient, and TENS has no long term curative value.