Interferential Current - IFC Interferential Current • History: In 1950 Nemec used interference of electrical currents to achieve therapeutic benefits. Further research and refinements have led to the current IFC available today – Two AC are generated on separate channels (one channel produces a constant high frequency sine wave (4000-5000Hz) and the other a variable sine wave – The channels combine/interface to produce a frequency of 1-100 Hz (medium frequency) Effects of IFC treatment: • Sensory nerve fibers - Pain reduction - receive a lower amplitude stimulation than the area of tissue affected by the vector, thus IFC is said to be more comfortable than equal amplitudes delivered by conventional means • Muscle fatigue - muscle spasm - is reduced when using IFC versus HVS due to the asynchronous firing of the motor units being stimulated Positive effects of IFC include: • reduction of pain and muscle discomfort following joint or muscle trauma • these effects can be obtained with the of IFC and without associated muscle fatigue which may predispose the athlete to further injury. Principles of wave interference - Combined Effects • Constructive, Destructive, & Continuous • Constructive interference: when two sinusoidal waves that are exactly in phase or one, two, three or more wavelengths our of phase, the waves supplement each other in constructive interference + = Principles of wave interference - Combined Effects • Destructive interference: when the two waves are different by 1/2 a wavelength (of any multiple) the result is cancellation of both waves + = Principles of wave interference - Combined Effects • Continuous Interference – Two waves slightly out of phase collide and form a single wave with progressively increasing and decreasing amplitude + = Amplitude-Modulated Beats: • Rate at which the resultant waveform (from continuous interference) changes • When sine waves from two similar sources have different frequencies are out of phase and blend (heterodyne) to produce the interference beating effect IFC • Duration of tx 15-20 • Contraindications minutes – Pain of central origin – Burst mode typically – Pain of unknown applied 3x a week in origin 30 minute bouts • Indications • Precautions – Acute pain – same as all electrical – Chronic pain currents – Muscle spasm IFC Techniques of treatment: • Almost exclusively IFC is delivered using the four-pad or quad-polar technique. • Various electrode positioning techniques are employed: – Electrodes (Nemectrody: vacuum electrodes): • four independent pads allow specific placement of pads to achieve desired effect an understanding of the current interference is essential • four electrodes in one applicator allows IFC treatment to very small surface areas. The field vector is pre-determined by the equipment Quad-polar Technique • Pads placed at 45º angles from center of tx area • Can reduce inaccuracy of appropriate tissues by selecting rotation or scan Channel B Channel B Channel A Channel A SCAN Bipolar Electrode Placement • The mix of two channels occurs in generator instead of tissues • Biopolar does not penetrate tissues as deeply, but is more accurate • When effects are targeted for one muscle or muscle group only one channel is used Two-circuit IFC: – At other points along the time axes the wave amplitude will be zero because the positive phase from one circuit cancels the negative phase from the second circuit (destructive interference) – The rhythmical rise and fall of the amplitude results in a beat frequency and is equal to the number of times each second that the current amplitude increases to its maximum value and then decreases to its minimum value Special Modulations of IFC: – Constant beat frequencies (model): the difference between the frequencies of the two circuits is constant and the result is a constant beat frequency. That is, if the difference in frequency between the two circuits is 40 pps, the beat frequency will be constant at 40 bps. Special Modulations of IFC: – Variable beat mode: the frequency between the two circuits varies within preselected ranges. The time taken to vary the beat frequency through any programmed range is usually fixed by the device at about 15 sec. IFC machines often allow the clinician to choose from a variety of beat frequency programs. Pain Control – Similar to TENS - beat frequency 100Hz – Low beat frequencies when combined with motor level intensities (2-10Hz) initiate the release of opiates – 30 Hz frequencies affects the widest range of receptors Parameter Range Intensity Sensory Electrode Config Quadpolar Beat Fq High – Gate Control Low – Opiate release Sweep Fq Long Duration Neuromuscular Stimulation • Beat frequency of approximately 15 HZ is used to reduce edema • General Parameters Parameter Range Intensity 1-100mA Carrier Fq 2500-5000Hz Beat Fq 0-299 Hz Sweep Fq 10-500sec IFC Technique of treatment: – Electrode placement: • The resultant vector should be visualized in placing the electrodes for a treatment . The target tissue should be identified and the vector positioned to hit that area. Typically at 45º angles is most effective. • Segregation of the pin tips is essential in the proper electrode positioning for IFC. The electrodes may be of the same size or two different sizes (causing a shift in the intersecting vector). Treatment through a joint has also been advocated without adequate research to establish efficacy of the treatment technique. Bone Stimulating Current: – Bone Stimulating Current:Bone Stimulating Current:IFC has been used (Laabs et al) studied the healing of a surgically induced fracture in the forelegs of sheep. Their study indicated an acceleration of healing in the sheep treated with IFC as compared to the control group Bone Stimulating Current: – This study validated an earlier study by Gittler and Kleditzsch which showed similar results in callus formation in rabbits. Several other studies have shown an increase in the healing rate of fractures but the exact mechanism by which the healing occurs is not understood. Bone Stimulating Current: – Some speculation is that an increased blood flow to the injured area is produced which allowed natural healing processes to occur more rapidly. – In one study (mandible fractures ) the IFC caused very mild muscle contraction of the jaw and this muscle activity was thought to have been a potential accelerator of the healing.