This lecture intends to provide general outline about the uses, parameters, precautions and contraindications of interferential current for undergraduate physiotherapy students at Kathmandu University School of Medical Sciences, Nepal. After the lecture, students will explore the evidences about current practices on the uses of IFT in various musculoskeletal pain conditions, critically appraise them and present the evidences to the class.

1. Saurab Sharma, MPT
Lecturer, KUSMS
Interferential therapy/ current
(IFT, IFC)
Electrotherapy
Lecture 5

2. Objectives of session
 At the end of the class, students will be
able to:
 Understand the background of IFT
 Explain the mechanism
 Explain the clinical uses of IFT
 Understand the use of various treatment
parameters
 Identify Hazards, Precautions and
Contraindications2

3. Introduction
 Developed in 1950’s
 Popular in 1970’s
 Transcutaneous application of medium
frequency alternating currents, whereas
amplitude is modulated at the low
frequency for therapeutic purpose.
3

4. Introduction
 Reduces the skin resistance, thus
reduces discomfort produced by low
frequency currents.
 Also permits treatment of deeper
tissues.
4

5. Introduction
 Available in 77- 98% per PT
departments in Western world (UK,
Ireland, Australia). (1995- 2000)
 90% use it at least once a day.
5

6. Uses
 Pain relief (91%)
 Acute pain- 26%
 Chronic pain- 50%
 NSCLBP- 88% (Foster et al.
1999)
 Other conditions- asthma, fracture,
incontinence, psoriasis, swelling,
enhance tissue healing, improve blood
circulation, muscle strengthening6

7. Theoretical mechanisms of IFC
 Neural effects
 Blood flow and swelling
 Placebo
 Muscle stimulation
 Bone and tissue healing
 Bronchodilatation
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8. Uses- EBP
 Ischaemic pain
 Cold induced pain
 Thermal quantitative sensory testing
 Mechanical pain
 DOMS
 Blood flow
 Cell activity
 Muscle stimulation
 IFC versus TENS
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9. Clinical indications
 For all types of pain syndrome
 Various musculoskeletal conditions,
Knee OA, Jaw pain, Fracture pain, LBP,
shoulder disorders, Palmar Psoriasis,
Fibromyalgia, knee surgery, swelling,
incontinence, bone healing
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10. Physical principles of IFC
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11. Physical principles of IFC
 Current A- 4,000 Hz
 set in the machine (Intrinsic frequency/
carrier frequency)
 Current B- 4,000 -4,200 Hz
 set by the therapist.
 Same amplitude but higher frequency
 Resultant waveform (F) = f2-f1
 Low frequency Current (0-200 Hz)
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12. Physical principles of IFC
 Amplitude of F (Current C) is NOT
constant
 Called as “beat frequency- BF” or
“amplitude modulated frequency-
AMF”
 F ranges from 1 Hz to 200 Hz
 The frequency swing is also referred to
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13. Physical principles of IFC:
Example
 When two medium frequency currents
are mixed:
 Frequency of resultant current will be
equal to the mean of the two original
currents
 This will vary in amplitude at frequency
equal to difference between the two
currents- AMF/ BF
 When two currents of 4000 and 4100 Hz
are mixed, results in medium frequency
current of 4050 Hz, whereas amplitude13

14. AMF
 Medium frequency current act as carrier
 Carrier frequency brings low frequency
current to the tissue.
 Literature shows that it is medium
frequency that causes the effect rather
than AMF
 But, responses induced by IFC
stimulation changes with different AMF14

15. AMF
 Lower AMF causes tapping or beating
sensation
 Higher AMF causes tingling sensation or
tetanic muscle contraction.
 Lower AMF (5Hz) are more uncomfortable
than 50-100 Hz
 50 and 100 Hz produces similar effects
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16. AMF- Parameters for conditions
 Treatment of pain- 1- 130 Hz (no
consensus)
 130 Hz for pain (38% therapist use in
Scotland)
 LBP- 80- 120 Hz
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17. Frequency sweep
 Sweep may be set between two pre-
fixed AMFs
 Hypothesized to reduce adaptation,
stimulates greater range of excitable
tissues for better treatment effects
 Eg- between 50 – 100 Hz (can be
adjusted in most machines)
 Most common- 6^6 (slowly increasing
and decreasing over period of 617

18. Electrode placement
 4 electrodes - Quadripolar, 4 pole method
 2 Electrodes- Premodulated-Bipolar, 2 pole
method
 Effects are like normal electrical stimulation
 More effects under the electrodes
 More sensory stimulation
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19. Electrode Placement-
Quadripolar
19
• Clover leaf
pattern
• Leaves are at right
angle to the
electrode
placement
• “4 pole” causes deep
within tissue effects

20. Electrode Types
 Suction electrode
 Carbon electrode
 Plate electrode
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21. Electrode placement
 For muscle stimulation:
 large electrode over nerve supplying the
muscle, smaller electrode over the motor
point
 Two electrodes of equal size over
proximal and distal end of muscles
 For Pain relief: same as TENS21

22. Electrode placement in LBP
 painful area (86.4%)
 spinal nerve root (53%)
 peripheral nerve (26%)
 trigger point (10%)
 acupuncture point (5%)
 Stimulation of nerve root better
improvement in function compared to
application at painful area22

23. Current intensities
 Strong but comfortable sensation- as
reported by patients
 Strong but comfortable sensation for
various people may be achieved at
different intensities
23

24. Treatment Duration
 Recommended 10- 15 minutes
 No longer than 20 minutes on one area
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25. Use as a treatment adjunct
 In 73% of cases
 IFC may not be an effective treatment
on its own, but rather as part of
comprehensive treatment program
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26. Hazards
 Burns
 Increased pain
 General malaise
 Nausea
 Vomiting
 Dizziness/ fainting
 Migraine/ headache
 Neurological effects
 Infection
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27. Contraindications
 Uncooperative patients
 Under anticoagulation therapy or history
of pulmonary embolism or deep vein
thrombosis should not be treated with
the vacuum electrode applications
 Fragile or bruised skin
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28. Contraindications: Application
over
 The trunk or pelvis during pregnancy
 Active or suspected malignancy
 The eyes
 The anterior aspect of the neck
 The carotid sinuses
 Patients with pacemakers
 Dermatological conditions e.g. dermatitis,
broken skin
 Danger of haemorrhage or current tissue
bleeding (e.g. recent soft tissue injury)
 Avoid active epiphyseal regions in children
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29. Precautions:
Check for pain sensitivity prior to
Rx
 Care should be taken to maintain the suction at a
level below that which causes damage / discomfort
to the patient
 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
 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
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30. Ask yourself
 What do I hope to achieve?
 How can this be done?
 What frequency would be most
effective?
 Should 2 or 4 electrodes be used?
 Where exactly are the electrodes to be
placed?
 How long a treatment should be given?
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31. References
 Kathleen Sluka. Mechanisms and
Management of Pain for the Physical
Therapist. 2nd Edition. IASP Press. Wolters
and Kluwer. 2016
 Tim Watson. Electrotherapy: Evidence Based
Practice. 2008. Churchill Livingstone. 12th
edition.
 John Low, Ann Reed. Electrotherapy
Explained. Principles and Practice.
Butterworth Heinemann. 3rd Edition.
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