The use of electric current to cure or relieve symptoms of pain have been documented as far back as 2500 BC, wherein stone carvings depicted how a species of catfish had organs that produced electric charge and was used to treat pain. Similarly, physician of Roman Emperor Claudius documented the use of electric fish to relieve symptoms of pain.
Transcutaneous Electrical Nerve Stimulation (TENS) is a means to analgesia but is simple to use and is non-addictive nor is it invasive, it is in fact a portable device to use. As technology has developed over the years, there are many devices available in the market which works on similar premise wherein via electrodes small electrical pulses are delivered directly onto the skin near the area of pain. This contact of electrical simulation helps to relieve pain.
The use of electro- analgesia increased manifolds due to the publication of the gate- control theory. According to this theory, the perception of pain could be reduced dramatically by the stimulating large diameter sensory nerve fibers while the pain is caused by activity in small diameter nerve fibers. According to Melzack and Wall (1965) there exists physiological gating mechanism at the dorsal horn of the spinal cord. They proposed that this gate can be either opened or closed in order to either permit or restrain the spread of pain information to the brain o let in process and make the individual feel the pain.
TENS excite the A- beta nerve fibers in the skin which causes the simulation of pain being transmitted to the smaller A- delta and C- fibers to be reduced, this is in turn leads to segmental inhibition. This is possible when the TENS machine is set on high pulse rate known as ‘high frequency’ (90- 130Hz), this causes the closure of pain gate.
Apart from having inhibitory effects on the neuron, TENS are also responsible for affecting the descending, extra- segmental pain pathways. The stimulation of A- fibers causes the release of neurotransmitters glutamate and aspartate and also increases the release of gamma- amniobutryic acid and serotonin, inhibitory neurotransmitters. On a ‘low frequency’ (2-5Hz) TENS stimulates the body to produce endorphins.
The burst mode in TENS machine helps to stimulate both the nerve types at the same time. Depending on the body type, pain and personal preference, different programs can be used throughout the day
Length of Pain Relief
A conventional TENS show quick results and pain relief is felt rapidly but the effect tends to wear down very rapidly, as soon as the machine is switched off. When TENS is used at low frequency the analgesic effect takes longer to achieve but the pain relief lasts long. Thus the effect of TENS may last anywhere from 10 minutes to 15 hours. In studies carried out by Cheing et al, 2003, some patients’ pain levels did not return to the same as before stimulation even after 24 hours. Thus depending upon the severity of pain, the body type and the stimulation effect, the length of pain relief differs from patient to patient.
Use of TENS in Various Conditions
TENS is used and recommended by doctors and physicians in various conditions such as:
Post-Operative: Various studies have found out the effectiveness of TENS post operation, especially when combined with various other analgesic methods.
Obstetrics: Many TENS machine brands promote the use of the machine to relieve labor pain as TENS does not have increased morbidity for mother and baby, as demonstrated by other traditional analgesics.
Wound Healing: Studies depict the effectiveness of TENS in advancing wound healing especially when electrodes are applied around the sacral and leg ulcers.
Chronic Pain: Various studies have reinforced the effectiveness of TENS in treating chronic pain in patients. TENS is extremely effective in treating lower back pain, osteoarthritis and neuropathic pain.
Thus according to the available literature, it is clearly evident that TENS is an effective method of relieve pain and pain symptoms of varied kinds.
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