4. CONTENTS
Definition Main clinical applications
History Indications & contraindications
Amplitude modulated frequency Precautions
Static interference
Dynamic interference
Triangular
Rectangular
Trapezoidal
Frequency
Dosage
Bipolar
Quadripolar
Vector
5. DEFINITION
Developed by Dr. Hans Nemec of Vienna, Austria in
the early 1950’s.
It may be described as the transcutaneous
application of two alternating medium frequency
electrical currents, which are slightly out of phase
causing amplitude modulation at low frequency for
therapeutic purposes
6. PRINCIPLE
The main principle of IFT is that when two medium
frequency alternating currents of slightly different
frequency are passed through the tissues where the
current intersect to produce a low frequency current.
The interference produced by the two currents in the
tissue varies in amplitude is called BEAT
FREQUENCY or AMPLITUDE MODULATED
FREQUENCY
The current is delivered through two sets of electrode
via two separate channel in the same stimulator
7.
8.
9. Amplitude Modulated Frequency
(AMF)
The AMF or beat frequency is the effective
component of IFT, it mimics the low freq current and
creates differential stimulation of nerve.
Low AMF, elicits a beating or taping sensation, while
higher AMF elicits a tingling sensation.
10.
11. STATIC INTERFERENCE :
If the two medium frequencies remain constant, the
beat frequency will also be constant
When a constant beat frequency is selected for eg 10
Hz, 50Hz or 100Hz…or any frequency between 1 to
250Hz is called as constant mode or static mode or
static interference system.
It may lead to gradually diminishing response due to
habituation of this particular current
12.
13. DYNAMIC INTERFERENCE
An arrangement that allows the beat frequency to
change automatically and regularly in the given
time period is called frequency modulation or
sweep or swing or dynamic Interference system.
Here there is moving of the area of interference
current in a to and fro manner through 45 °.
14. Thus the machine could be set to sweep
Eg: between 20 to 80Hz over a period of 6secs and
back over next 6 secs.
This pattern and timing of the modulation is
adjustable and sometimes called as spectrum.
This dynamic system helps to prevent nerve
accomadation.
19. FREQUENCY
High AMF: 1) Frequency ranges from 100Hz-150Hz
2)Useful for relief of acute and chronic
pain
Low AMF : 1)Frequency below 50Hz
2)Useful for sub acute pain
20. DOSAGE
Intensity of Current:
It should be gradually increased till patient feels
comfortable tingling sensation
22. SWEEP
The principle of using the sweep is that the machine
is set to automatically vary the effective stimulation
frequency using either pre-set or user set sweep
ranges. Such sweep prevents accommodation of
nerves
23. METHOD OF APPLICATION
Bipolar Application
Quadripolar Application
Vector or scanning mode
24.
25. Quadripolar Application
Interferential current is produced by applying two
medium frequency currents via 4 electrodes.
Electrodes are used in two pairs.(color coded)
Each pair should be placed diagonally
It produces modulated current in a clover leaf
pattern.
26.
27. Vector or scanning mode
Specific area of the tissue at any depth can be
treated in patients with diffuse area of pathology
and when the arrangement of the lesion within the
static interference field is doubtful,
The vector principal which produces a scanning
movement of the field, so that all the field are
subjected to have maximal interferential effect
28.
29.
30.
31.
32.
33.
34. Suction Vs Plate electrode
IFT is often applied via electrodes that are held in
place using the intermittent suction unit. Alternately
flat carbon electrodes may be used.
Suction has claimed to stimulate cutaneous nerves
and vasodilatation.
36. This depends upon:
Magnitude of current
Type of mode used i.e. Rhythmic or constant
The frequency range used
Accuracy of electrode positioning
37. Main clinical applications are :
Pain relief
Muscle stimulation
Increased local blood flow
Reduction of edema
38. Pain Relief
Pain relief is achieved by stimulation of AB fibers by
using short duration pulses of frequency 100 Hz.
(pain gate theory)
While 15Hz is applied to stimulate the small
diameter c and Ad fibres via descending pain
supression pathway.
39. MUSCLE STIMULATION
For patients who can not generate useful voluntary
contraction, IFT may be beneficial. Most effective
motor nerve stimulation range is between 10-25Hz
When employing IFT it is possible to continue to
stimulate the muscle beyond its point of fatigue.
It helps in reducing oedema
40. Increase circulation
Deep tissue penetration stimulates parasympathetic
nerve fibers for increased blood flow
It improves circulation of blood and helps wash away
the chemicals that stimulate the nociceptive nerve
endings and thus help to reduce pain too.
41. OEDEMA
Local muscle contraction combined with its local
vascular changes encourages the reabsorbtion of
tissue fluid.
52. Interferential Precautions
• If there is abnormal skin sensation, electrodes
should be positioned in a site other than this area
to ensure effective stimulation
• Patients who have (marked) abnormal circulation
• For patients who have febrile conditions, the
outcome of the first treatment should be
monitored
53. • Patients who have epilepsy, advanced cardiovascular
conditions or cardiac arrhythmias should be treated at
the discretion of the physiotherapist in consultation
with the appropriate medical practitioner
• Treatment which involves placement of electrodes
over the anterior chest wall
54. Summary
History of IFT
Amplitude or beat frequency
Interferences( static and dynamic)
Types of sweep
Parameters
Techniques
Effects
Precautions
55. References
1.Textbook of electrotherapy Jagmohan Singh
2. Electrotherapy evidence-based practice by Sheila kitchen
3.https://www.slideshare.net/.../interferential-current-or-therapy-for-
physiotherapy-stude