What is TENS?
Transcutaneous electrical nerve stimulation (TNS or TENS) TENS therapy is the application of a pulsed rectangular wave current via surface electrodes on the patients’s skin. This current is often generated by small battery operated machines in which circuits modify the battery’s output in such a way that it will have stimulatory effect.
TENS frequency is between 2 Hz to 600 Hz.
Intensity lies in between 0 to 60 mA.
Large mains units are available to produce the current, but often small units made to be placed in the patient’s pocket and utilizing batteries are preferred. Conductive rubber electrodes covered with a conductive gel in order to gain good skin contact are placed on the patients skin. The electrodes can be bandaged on to the patient or fixed with adhesive tape. The wires connecting the electrodes to the unit can strategically concealed with clothing.
Positioning of TENS electrodes:
Electrode positioning is an area of considerable debate and a number of approaches may be used. Electrodes can be placed over:
- Acupuncture points, motor points or trigger points
- Area of greatest intensity of pain
- The appropriate dermatome or spinal segments
- The appropriate peripheral nerves
Some advocates always place one electrode over the spine and one over the peripheral pain. Others prefer the use of two simultaneous currents applied via separate circuits. The permutations for placement with a dual channel unit are considerable. Whichever position is chosen for electrode placement, it is best if the skin below them has an intact sensory mechanism as it is the large diameter afferent sensory stimulation produced by TNS current acting on the skin that produces effect on pain.
Treatment by Tns therapy:
A number of strategies may be adopted,
➢The patient may have a single daily treatment session upto 40 minutes duration.
➢The patient may stay connected to portable TENS unit all the time and:
The unit switched on when required
Unit left on most of the time
Dangers & Contraindications of TNS therapy:
➢A continous application of high intensity TNS with high frequency and long duration pulses could produce an electrolyte reaction below the electrodes.
➢Application of TNS in the region of a cardiac pacemaker is inadvisable as possible interference with a pacemaker function could occur.
Uses of TENS:
TNS can be a useful method of reducing or removing pain in chronic pain syndromes in order to recieve a successful result the treatment parameter may have to be changed and considerable experimentaions with pulse width, frequency, electrode placement and intensity may be required.
Types of TENS:
The most common method by which TENS therapy is applied is where the treatment parameters are:
- Frequency between 100 and 150 Hz.
- Pulse width between 100 and 500 micro sec.
- Intensity: The patient should feel a tingling, pins and needles sensation often between 12 and 30 mA.
- Activate A delta fibres occurs.
- This method may be called High TNS.
Uses of High TENS:
- Tetanic Muscle Contraction
- Muscle Stimulation
- Nociceptive transmission inhibited
- Pain reduction
A less popular method is where the treatment parameters are:
- Frequency 1 to 5 Hz.
- Pulse width 100 to 150 micro sec.
- Intensity may be higher than 30 mA.
- Release of beta endorphins from pituitary occurs.
- This method may be called Low TNS
Low TENS uses:
- Muscle twitching
- Blocks nociceptive transmission
- Chronic Pain
- Myofascial Pain
- Pain caused by muscle spasm