Medium Frequency Current (Interferential Current & Premodulated)

1. INTERFERENTIAL CURRENT
(IFC)
MEDIUM FREQUENCY CURRENT
Aditya Johan .R, M.Fis

2. • Dr. Hans Nemec was born July 6, 1907 in Vienna and died
September 1981 as the Inventor of IFC
• IFC is most likely one of the most commonly used forms of
electrical stimulation in the clinical environment for the
reduction of pain
• IFC is the application of two different and separate sinusoidal
currents that are delivered to the same treatment area at the
same time at different frequencies with carrier frequencies
above 1,000 pps (1000 – 10.000 Hz)
• The difference between two currents produces what is referred
to as a beat frequency

3. • When two sine waves interact with each other and are at the
same frequency, they are in phase, meaning the amplitude
would double
• When two sine waves interact with each other and are at the
same frequency but 180 degrees out of phase, they would
cancel each other out
• When two sine waves interact with each other and are at
different frequencies, they would periodically be in phase and
out of phase, which means that the amplitude would double
and be canceled out, thus creating a beat frequency

6. • The main advantage of IFC is the depth of penetration and that
it can cover a larger treatment area than other forms of
electrical stimulation

7. • Many electrical stimulation devices that offer IFC have a
additional setting on the device that is referred to as “premod”
or premodulated IFC
• Remember that interferential occurs due to the interference of
separate channels within the tissues
• the stimulations that are provided by the uninterrupted
kilohertz frequency under the electrodes of each channel are so
rapid that they are incapable of eliciting a specific motor
response (Wedensky Inhibition)
• According to Lullies, continued stimulation with a medium-
frequency alternating current can result in a situation in which
the nerve fibre ceases to react to the current (Wedensky
inhibition)

8. • To prevent Wedensky Inhibition, it is necessary to interrupt the
current after each depolarization. This can be achieved by
rhythmically increasing and decreasing the amplitude (amplitude
modulation)
• once two channels interfere with each other and the difference is
within a sensory or motor range, the patient then perceives the
sensation within the tissues rather than under the actual electrodes
• The amplitude modulation is also characterized by the modulation
dept (M).
• The modulation depth is expressed as a percentage, and can lie
between 0 and 100%. It will be clear that a modulation dept of
100% is required to actually interrupt the current

11. FREQUENCY MODULATION
• Method of preventing accommodation
1. The width of the Frequency Modulation
• A ‘broad’ Frequency Modulation (i.e. a large frequency range) is
better for preventing accommodation than a ‘narrow’ Frequency
Modulation
2. The Frequency Modulation mode (frequency modulation
sweep)
• Depending on the equipment used, there are various ways of
indicating the ratio between the base AMF and the Frequency
Modulation (in seconds)

12. If the AMF is set at 20 Hz and the frequency modulation
at 50 Hz, the current will scan through all frequencies
between 20 Hz and 70 Hz

13. Patients with acute conditions are treated with :
1.a relatively low amplitude
2.a relatively high AMF
3.a relatively broad Frequency Modulation
4.a relatively gently changing Frequency Modulation
program with a long duration (6/6 or 1/30/1/30 s’)

14. Patients with less acute conditions are treated with :
1.a relatively high amplitude;
2.a relatively low AMF;
3.a relatively narrow Frequency Modulation;
4.a relatively abrupt Frequency Modulation program
with a short duration (1/1 s)

15. THE END…