1. Interferential Therapy
Mohammed T, Ahmed PhD PT
Rehabilitation Health Sciences
CAMS-KSU
E.Mail

2. Outlines Introduction Definition Physical characteristics
Therapeutic uses
Contra-indications
Dangers
Treatment parameters
Practical application

3. Interferential Therapy
Introduction
Widely used electrotherapy modality
Developed by Dr. Hans Nemec of Vienna in Australia 1950s
Utilise the therapeutic aspects of low frequency currents without the discomfort.
Used in United States by 1980s
In 1999
fifth among the therapeutic modalities
In Australia 77% of 160 physiotherapy facilities reported using IFT daily
A survey in England found that 69% of respondents used IFT at least two to three times per day.

4. Principal 0f Interferential Therapy
Trancutaneous uses of two or three alternating medium frequency (2000 to 5000Hz) sinusoidal current to introduce low frequency (1 to 250Hz) current, used to stimulate sensory and motor nerves without painful and unpleasant side effect associated with low frequency current and with little skin resistance.

5. Interferential Therapy Principle
Two medium frequency current
-The F1 is fixed on the machine, 4000Hz (2000Hz -6000Hz).
-The F2 is variable between 4001Hz to 4150Hz
Beat Frequency (AMF) = F2 - F1= is range between Hz
It is better to have F2 “swing” within a range of frequencies, that limits accommodation and habituation to current)

6. Interferential Therapy Principle
Tissue resistance is inversely proportional to frequency.
Z=1/2πfc
Where
Z= Skin resistance by Ohm (Ώ)
F = Frequency
C= Capacity of the skin in microfarad (1 =10-6)
The tissue impedance at
50Hz is 3200 Ώ
4000Hz is 40 Ώ
Why Interferential Therapy (IFT)
Associated with lower skin resistance
More comfortable & tolerable
Deep penetration

7. Methods of Interferential Current Production
Application Modes
2-poles(Bipolar)
4-poles
Stereo-dynamic Method(3D
1-Quadripolar static
2-Quadripolar with Vector Scan

8. IFT- (pattern ) Modes Parameters 2-poles IFC (Bipolar)
4-poles (Quadripola) IFC
static
Vector Scan
Production
Interference of two medium frequency sinusoidal current circuit 1 ; C1=3000Hz), with another Circuit ;C2=3050Hz), to introduce low frequency current with beat frequency (50Hz).
Output
2electrodes /1 channel
4electrodes /2 channel
Modulation
Pre-modulated, at the device circuit (not at treated tissue level).
Current modulated at tissue level
Field
Static.
Static
Dynamic
Shape
Oval
Four-leaf clover
Circular
Intensity (amplitude )
Strong but comfortable , highest tolerance of muscles contraction . The maximum amplitude of current is halfway between the lines of two currents.
Uses
Suitable for small area
(ankle, elbow)
It is used for acute conditions because of its mildness effect
It is beast suited for large area and diffuse pain as shoulder, back, and thigh.
Sterodynamic Method(3D)
Production: Interference of three medium frequency sinusoidal current circuit; C1, C2 &C3), with interface to introduce low frequency current.
2. Output: Associated with use of six electrodes from two or three output channels, (star or Y-shaped electrodes).
Current modulation: Current modulated at the tissue level.
Current field: “Static”
Current Shape: “Flower shaped”
Sterodynamic allow the current field to, enlarged into 3D therefore induce large treatment area of interferential therapy.
This types of interferential not available and provided in separated machine.

9. Bipolar Method

10. Quadripolar Method

11. Quadripolar with Vector Scan
4. Amplitude: The maximum amplitude of current is halfway between the lines of two currents. The current amplitude from one circuit is allowed to vary slowly between 50% to 100% of the maximum value set, with the current amplitude of the second circuit sets automatically at fixed value of 75%, thus create electronic phenomenon described as "vector scan“.
Current field: is “Dynamic” , This "vector scan" rotates back and forth between the two lines of current, resulting in enlarged treatment area or field of interferential therapy.
Uses: It is beast suited for large area and diffuse pain as shoulder, back, and thigh.

12. Frequency Sweep
Interference frequencies come in automatic pre selected modes with a desired intensity at a constant level .
Frequency scale: 1 to 100Hz Constant frequency
1 to 10Hz Rhythmic frequency
90 to 100Hz Rhythmic frequency
Rhythmic frequency
it is obtained when one carrier frequency remains fixed and the other keeps on changing in frequency at regular interval from lower to higher value and back down.
It may take 10 seconds to go up and 5 seconds to come down,
it is known as Sweep , this sweep prevents accommodations of the nerves

13. Frequency Sweep Pattern
Triangular sweep pattern: The machine gradually changes from the base to the top frequency over 6 seconds (1-3seconds)
Rectangular (step) sweep pattern: This produces a very different stimulation pattern in that the base and top frequencies are set but the machine then “ switches” between these two specific frequencies rather than gradually changing from one to other.
Faster sweep is used for less painful stimulation & strong muscle contraction

14. IFC advantages & disadvantages
1. More comfortable than TENS
a. Medium-frequency currents meet with less skin resistance than low frequency currents; TENS uses low frequency currents
2. Stimulates tissues deeper than a TENS unit
3. Larger coverage area than TENS
Disadvantages
1-Eliminates pain; doesn't deal with cause of the pain
2. Few portable units available
3. Expensive

15. Physiological Effects of IFT
Prime physiological effects of interferential current therapy is the capacity to depolarize sensory and motor nerve fibers via application of surface electrodes positioned over the treated area.
The depends upon
1-Magnitude of current.
2-Types of mode used rhythmic, constant
3-Frequency of current
4-Accuracy of electrodes position
The 4 main clinical applications are
Pain relief
Muscles stimulation
Increased local blood flow
Reduction of edema

16. IFC is not effective in post-traumatic pain in the acute stages
This may be achieved through
Higher frequencies (90-130Hz) stimulate pain gate mechanisms
Lower frequencies (2-5Hz) can be used to activate the opioid
IFT has marked analgesic effect on pain in following conditions.
Reflex sympathetic dystrophy
Stump pain
Herpes Zoster
Vascular insufficiency
Myofascial Pain Syndrome (MPS)
IFC is not effective in post-traumatic pain in the acute stages

17. Urinary Incontinence
Strong muscle contraction using interferential therapy will be used to cause muscle reeducation for pelvic floor muscles
Program I Hz rhythmic
Program II Hz rhythmic
Program III Hz consistent
Electrodes placement
Technique I
One electrode placed under the ischial tubersity and other placed inferior to the symphysis pubis
Technique II
One electrode placed on inner upper aspect of the thigh and other electrode: inferior to the symphysis pubis (lower abdomen)
Duration of treatment minutes.
Dosage ; Medium

18. Edema Edema & Hematoma Hematoma PI- 1-100Hz rhythmic
PII- 100Hz consistent
Physiological effects :
Vibration of ions and facilitates ions movement in the cells.
Alternative rhythmic excitation and relaxation produce muscles pump
Alteration of cell membrane permeability
Increase venous and lymphatic drainage
Hematoma
During acute stage Using 100Hz constant current , with ice application.
During chronic stage: Using 100Hz constant current with ultrasound

19. Interferential Contraindication
Over arterial &venous thrombus 1
Over infected area 2
Over transcervical area 3
Over transcranial area 4
Pregnant uterus &lower abdominal 5
Over haemorrhagic area. 6
Over and around tumor 7
Pacemaker / metallic implant 8
Unreliable patients & patients suffering from mental confusion 9

20. Dangers and Precautions
Burn
Hematoma
Poor results
May be due to
Bar metal electrodes against skin
Increased intensity
Insufficient moisture pads
Suction force (negative pressure) may cause hematoma & ecchymosis
Improper position of electrodes
Poor balanced circuit
Incorrect choice of frequency
Device must be away fro diathermy device by 6meters

21. IFT Applications Parameters
I-Stimulator types
Desk cabinet (lined –powered).
Portable (battery powered).
II-Methods of delivery
Bipolar: for localized tissue
Quadripolar : for deeper tissue
Quadripolar with vector :for deeper tissue with enlarged area.
Stereodynamic ; for deeper tissue with enlargement area.
III-Current modes
Constant current modes
Sweep current (rhythmic current modes)

22. IFT Applications Parameters
IV-Electrode types ( plate , Pen and vacuum)
One-pole, pad, rubber carbon-impregnated.
Two-pole , pad, rubber carbon-impregnated .
Three -pole, pad, rubber carbon-impregnated (star or Y-shaped).
Four -pole , pad, rubber carbon-impregnated .
Vacuum or suction (rubber or metal ) electrodes.
Four Vacuum or suction cup electrodes

23. IFT Applications Parameters
V-Intensity of Current
-use an intensity of current which produces a strong but comfortable prickling sensation without a muscular contraction;
-Steps to follow:
Increase current until the patient feels a definite prickling, and leave for 1-5 minute for it to decrease.
2) Increase current again until the patient reports a slight muscular
contraction, then decrease until contraction stops
VI-Duration of treatment:
IFC usually applied for minutes treatment at a normal intensity.
Should not be given to one area for longer than 30 minutes
If more than one area is to be treated è total time should not exceed 30 min.
VII-Frequency of Treatment
In most cases, treatment every other day (i.e. 3/wk.) is ideal
A course of treatments is given(Use until IFT is no longer effective)

24. IIX-Electrodes Placement: Knee/elbow Pain

25. IIX-Electrodes Placement: Neck Pain

26. IIX-Electrodes Placement: Shoulder Pain

27. IIX-Electrodes Placement: Low BackPain