Interferential therapy

Hands on Interferential therapy
#abcd
HSG
Shubham Singh

Outline
#abcd
 Introduction
 Principle of production
 Modes
 Methods of application
 Dosages
 Setting of apparatus
 Techniques of application
 Physiological effects
 Contraindication
 Indication

Introduction
Interferential therapy: a form of electrical treatment using medium
frequency currents to produce a low frequency current of low
frequency effects.
 also called nemac’s current
medium frequency currents = a current with frequency ranging between
1000Hz to 10,000Hz
Interference: the combination of two or more electromagnetic waveforms
to form a resultant wave in which the displacement is either reinforced or
cancelled

 Greater penetration
 Higher tolerance
 Comfort over the low frequency current
 Effects are produced in the tissues where they are required without unnecessary
or uncomfortable skin stimulation.
 Can be used for pain relief as well as for muscle stimulation.
Why Interferential therapy ?

 The problem associated with application of low frequency current (faradic,
sinusoidal current) is very high skin impedance that results in pain thereby
discomfort
𝑍 = 1/2𝜋fc
Abbrevations
Z = skin impedance in ohms
f = frequency of current in hertz
c = capacitance of skin in microfarad
 When low frequency current(frequency=50-60Hz) is applied
- skin resistance is 3200Ω
 When medium frequency current(frequency=4000Hz) is applied
- skin resistance becomes 40Ω
IFT over low frequency current

𝐼 = 𝑉/(𝑅 + 𝑟)
Abbreviations
I = Applied current
V = Voltage
R = Skin resistance (remains constant)
r = Skin resistance developed due to applied current
 When low frequency current is applied
- R(developed skin resistance) is large thus produces pain and
discomfort
 When medium frequency current is applied
- R(developed skin resistance) is small thus produces comfort with
higher penetration and higher tolerance

Principle of production
Interference effect:
 It uses two medium frequency currents that crosses in patient tissue
 One of the medium frequency current is kept constant at 4000Hz(at these
frequency tissue generates minimum impedance)
 The other current is varied between 3900 to 4100 Hz
 The point of interference or the point of intersection of currents produces
a low frequency current
 This point of interference effects a beat frequency (treatment frequency,
amplitude modulated frequency), which is equal to the difference between
two medium frequency currents.

Channel / Circuit A = 4000 Hz
Channel / Circuit B = 3900 Hz
Beat frequency = Frequency of (channel A – channel B)
 Also called as amplitude modulated frequency or frequency of
treatment
 Produced at the point of intersection
 Can be varied by varying the frequency of second circuit

Concept of beat frequency
At the point of intersection
 When two peaks of amplitude are in the same direction coincides the resultant
amplitude will be at maximum, called summation of frequency
 When two peaks of amplitude are in the opposite direction thus the resultant
amplitude will be the difference of two, called cancellation of frequency
same phase
opposite phase

Mode
- Can be pre selected on the machine
constant
mode
rhythmic
- both the currents are kept constant
- a constant beat frequency is produced
Ex. 10, 20, 50, 100 Hz
-one current is kept constant while other is
variable
- a variable beat frequency is produced
Ex. 20Hz to 80Hz for 6 sec

Rhythmic = beat frequency is variable = frequency surge(from lower to higher value and
back)
 Prevents accommodation
 The pattern and timing of this modulation is usually adjustable in some time called
the spectrum
 Allows the beat frequency to change automatically regularly between some present
pair of frequency over a specified time period called frequency modulation /
frequency swing / frequency sweep.
Ex. 20Hz to 80Hz for 6 sec
Importance of rhythmic beat frequency
Lower
frequency
Higher
frequency
Swinging time

Methods of application
Depending upon
- area to be treated
- extent of effect required whether deep or superficial
method
bipolar
quadripolar
vector scan
static
- static interference
- area in which IFT s set up remains
stationary
- clover leaf appearance
- lies at 45˚ from each electrode
dynamic interference

Electrode placement
 Electrode positioning should ensure adequate coverage of the area for
stimulation.
 Correct and proper positioning of electrodes is important for effective and
purposeful delivery, and it depends upon-
1. Size of electrodes: size is directly proportional to area
2. Distance of placement of electrodes: distance is inversely
proportional to intensity
3. Types of electrode placement: bipolar or quadripolar

Importance of electrode placement
 depth of modulation and amplitude is determined by
positioning of electrodes
 using larger electrodes will minimize patient discomfort
 closely spaced electrodes increase the risk of superficial tissue
irritation and possible damage and skin burn

Types of electrodes
commonly used
Suction electrode
Pad electrode
Pad electrode with
sponge cover
Self adhesive
pad electrode
- Used especially for larger body areas
like the shoulder girdle, trunk, hip,
knee
- Believed to be its effect in blood
flow and circulation

Quadripolar method
 Four electrodes are used in two pairs which colour coded
 Placement: placed diagonally, opposite to one another
 Produces deep effect i.e. modulation is 100 % and amplitude is
greatest

VECTOR SWEEP SCANNING:
 also called ROTATING VECTOR SYSTEM or DYNAMIC INTERFERANCE FIELD
SYSTEM
 by varying the current amplitude of circuit with respect to other,
leads to movement of clover leaf pattern of maximum modulation to
inflow through 45˚ in the region of intersection

Vector Scan
When two equal forces intersect, maximum result is
halfway between the two forces(45˚)
Clover leaf appearance:
maximum current modulation as
due to the submission of two
currents by varying the current
amplitude of circuit with
respect to other, leads to
movement of clover leaf
pattern: VECTOR SWEEP
SCANNING

Quadripolar placement at back Quadripolar placement at Shoulder

Bipolar method
 Two electrodes are used one of each pair
 Placement: placed diagonally, opposite to one another so that treatment are
lies in between
 In this case currents are superimposed such that single current is produced
 Interference occurs throughout the reason between two electrode
 Useful for small areas
 Produces superficial effect i.e. more sensory stimulation than four pole
technique.

Shoulder
Lower cervical:
upper trapezius
Knee
Elbow
Bipolar method

Depends upon
1. Intensity
2. Duration
3. Area to be treated
𝑎𝑟𝑒𝑎 𝑜𝑓 𝑡𝑟𝑒𝑎𝑡𝑚𝑒𝑛𝑡
𝑖𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦
= 1
i.e. for larger areas a current of higher intensity is required or vice versa to produce
effective therapeutic effect
When applying on rhythmic mode Intensity is gradually increased till patient feels
comfortable
Dosages

Duration:
A. For acute cases: low intensity with shorter time
- once or twice a week
B. For subacute and chronic cases: high intensity with longer
- three to four times

 Frequency setting: constant or variable
 Intensity
 Time: short or long
 Mode: static or rhythmic
Setting up the apparatus

 Inspection of skin: cleaning the skin
 Insulation of wounds over area of application: applying petroleum jelly
 Positioning of electrodes: positioned so that the crossing points of two currents is
over or within the lesion
 Selection of parameters
 Educating the patient
Techniques of application

Physiological effect of IFT
Clinical application of IFT therapy is based on peripheral nerve stimulation
Depends upon
- Magnitude of current: a current with minimum intensity to overcome the
threshold of nerve fibre is necessary for stimulation.
- Mode: whether rhythmic or constant
- Frequency range: EX. a frequency of 100 Hz stimulates large diameter nerve fibers
while that of 15 Hz small diameter fibres get stimulated
- Electrode positioning: distance between electrodes, accuracy of electrodes

 Pain relief: activation of pain gait control mechanism
 Shorter duration pulse at frequency of 100 Hz stimulates large diameter
nerve fibres (higher frequencies(90-130Hz) stimulates the pain gate mechanism)
 At frequency of 15 Hz small diameter fibres get stimulated (lower frequencies
(2-5Hz) activates the opioid mechanism, thus providing a degree of relief)
 Increased circulation is also thought to decrease pain
 Increased blood flow: stimulation of autonomic nervous system leads to muscle
contraction or by local pumping effect
 to achieve a greater effect stimulation was applied via suction electrodes
 a frequency sweep of 10-30 Hz is observed to be most effective

 Motor stimulation: innervated muscles will contract at frequency between 1 to
100 Hz
 at frequency 5 to 20Hz: twitch / partial tetany is produced
 at frequency 30 to 100Hz: tetanic contraction is produced
 in rhythmic mode a complete range of muscle contraction is produced
most effective motor nerve stimulation appears to lie between 10 and 25 Hz
 Absorption of exudates: a rhythmic frequency of 1-10 Hz produces a rhythmic
pumping action.
 Also believed its role in stimulating healing and repair

IFT over TENS for pain reduction
 Produced low frequency interference of IFT is characterized with
benefits over TENS as
 subsiding unpleasant effects like pain, discomfort and skin
irritation
 greater penetration
 treatment area is large for the same setup
NOTE: Every device has it’s own therauptic value, above
comparisons are made on common parameter for same therauptic
effect.

Contraindication
 Arterial disease: stimulatory effect may produce emboli
 DVT: can dislodge thrombus
 Acute Infection: can exaggerate acute infection
 Patient with pacemaker: may alter the function
 Malignant tumor: can metastasize
 Large open wound: charge accumulation
 Over insensitive areas: may leads to burns
 Over uterus of a pregnant women
 Very young or very old patients

Indication
 Widely used for relief of pain, for example
• Low back pain
• Periarthritis shoulder
• Osteoarthritis knee
• Chronic ligamentous lesion
• Fibrositis
• Neuralgia
• Sprain and strain
 Chronic edema
 Hematoma: during first 24 Hrs. together with ice packs it is useful for resolution
of hematoma
 Stress incontinence and urinary incontinence

IFT over Faradic current(faradism under pressure) for edema reduction
 Why IFT ?
 Stronger contraction
 Easier setup (bandaging is not needed but in cases area becomes problem
while placing electrodes in quadripolar method)
NOTE: Every device has it’s own therauptic value, above
comparisons are made on common parameter for same therauptic
effect.

Incontinence
Urinary
Incontinence
Stress
incontinence
Involuntary loss of urine due
to loss of sphincter control
Most common in women,
secondary to child birth
Treatment parameters
 A sweep of 10-100 Hz is used
 Frequency of 10-15 Hz stimulates the pelvic floor muscles
 Frequency of 5-80 Hz stimulates the autonomic nerves system
 Treatment is given 2-3 times weekly

Electrode placement
 One electrode from each channel is placed on the lower abdomen
above the outer half of inguinal ligament
 The other two electrodes are placed on the upper part of the inner
aspect of the thighs, near the origin of adductors
Patient position
 Stride sitting or stride lying
 May vary from condition to condition

Shubham Singh
#abcd
Thank you
for your
’active participation’ & ‘kind collaboration’

Interferential therapy

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