Interferential current

Interferential current

1. Electrotherapy DR RIAZ AHMED PT LECTURER

2. Medium Frequency Current Medium frequency current are the current whose frequency fall between the range of 1000 to 10000 Htz. ADVANTAGES 1)Greater penetration 2) High tolerance and comport 3) Can be used for pain and muscle stimulation 4) Low skin resistance

3. Types 1) Rebox -type current: rebox electrotherapeutic method is based on non invasive transcutaneous application of specific current to a living tissue. it is used for acute and chronic pain, immobility musculoskeletal and neurological disorders. 2) Russian current: The Russian current waveform is type of electrical stimulation that delivers medium frequency current in alternating pulses or burstof energy. . 3) Interferential therapy

4. Interferential therapy Historical Background Introduced by Dr. Nemec in Vienna in the early 1950’s. D efinition : T he transcutaneous application of alternating medium-frequency electrical currents, amplitude modulated at low frequency for therapeutic purposes. Or It is the resultant current produced when two or more alternating current are applied simultaneously at the point of intersection in a given medium.

5. Definitions Impedance :- The effective resistance of an electric circuit or component to alternating current, arising from the combined effects of ohmic resistance. Modulation is the process of varying one or more properties of a periodic waveform. Beat Frequency The interference produced by the two current in the tissue is called beat frequency

6. Basic Principles of ITF The ITF depends upon the interferential effect of two medium frequency currents crossing in the patient tissue. The interference produced by the two current in the tissue is called beat frequency.

7. Let us take two medium frequency current in circuit A =4000Hz and circuit B=3900 Hz. Where these two current are applied to the tissues, at he point where current cross over, a new beat frequency current is setup whose amplitude is modulated and the frequency of the new current is called beat frequency (Interferential current). Current A: f1 (this current is set on the machine, thus called “intrinsic/carrier frequency”) Current B : f2 (same amplitude, but slightly higher frequency; therapist sets this one) F=f1-f2=4000-3900=100Hz Frequency range can be produced 1-250Hz

8. Physiological Effects of ITF Excitable tissues can be stimulated by low frequency alternating currents. Although to some extent, all tissues in this category will be affected by a broad range of stimulations, it is thought (Savage 1984) that different tissues will have an optimal stimulation band, which can be estimated by the conduction velocity of the tissue. These are detailed below: Sympathetic Nerve 1-5Hz Parasympathetic Nerve 10-150Hz Motor Nerve 10-50Hz Sensory Nerve 90-100Hz Nociceptive fibers 90-150Hz (?130Hz specific) Smooth Muscle 0-10Hz The clinical application of I/F therapy can be based logically on this.

9. The are 4 main clinical applications for which I/F appears to be used: Pain relief Muscle stimulation Increased blood flow Reduction of oedema

10. Pain Relief: Higher frequencies (90-150Hz) to stimulate the pain gate mechanisms & thereby mask the pain symptoms. Short duration pulses at a frequency of 100Hz may stimulate large diameter nerve fibers which will have an effect on the pain gate in the posterior horn, and inhibit transmission of small diameter nociceptive traffic.

11. Muscle Stimulation Stimulation of the motor nerves can be achieved with a wide range of frequencies. Range 1-100Hz stimulation at low frequency (e.g. 1-5Hz) will result in a twitches (5-20Hz) Partial tetany 30-100Hz Tetanic contraction. The choice of treatment parameters will depend on the desired effect, but to combine muscle stimulation with an increase in blood flow and a possible reduction in edema, there is some logic in selecting a range which does not involve strong sustained tetanic contraction & a sweep of 10-25Hz is often used.

12. Increased blood flow combine muscle stimulation with an increase in blood flow and a possible reduction in oedema, there is some logic in selecting a range which does not involve strong sustained tetanic contraction & a sweep of 10-25Hz is often used .

13. Reduction of oedema This is accelerated by a frequency of 1-10Hz rhythmic, as a rhythmical pumping action is produced by muscle contraction, and there is possible effect on autonomic nerves which can effect the diameter of blood vessels, and therefore the circulation. Both of these factors will help absorb exudates and thus reduce swelling.

14. INDICATION 1. Relief of chronic pain (i) Low back pain (ii) Periarthritis shoulder (iii) Osteoarthritis knee 2. Absorption of exudates 3. Stress incontinence

15. Contraindications(General) Pacemakers Malignancy Pregnancy Bacterial Infections Thrombosis Fever Hypertension Anemia Sever renal and cardiac failure

16. Deep X-ray and cobalt therapy Epileptic patients Non cooperative patients Mentally retarded patients Very poor general condition of the patient

17. Contraindications (Local) Open wounds Very recent fractures Skin grafts Severe edema Hairy surface Acute inflammation Metal in the part Hypersensitive skin Loss of sensation

18. Methods of treatment Skin must be clean and clear before the start of the treatment The part of the body to be treated should be washed and if there is any skin lesion it should be covered by applying petroleum jelly on it. The electrodes should be placed in such a way that the crossing point of two currents lie above or around the affected part. The suitable frequency current should be given for different conditions. Increase the power gently and cautiously until the patient starts feeling the current. It can be increased till the patient can tolerate.

19. Preparation of Apparatus Check whether all the knobs are at zero Checking the pins of the plugs and check whether the switch is turned off Check the insulation of wire Check whether the switch in the stimulator is working Check whether fuse is present Check whether hand switch of patients use is intact and working