A transcutaneous electrical nerve stimulation (TENS) unit is used to apply electrical currents through the skin to the nerves via electrodes in order to reduce chronic and acute pain from various causes.
TENS is a noninvasive therapeutic pain management modality that is used alone or in conjunction with pain medications or other pain-management techniques. A TENS unit is used to transmit low-voltage electrical currents through the skin to the underlying nerves at the area where pain occurs. TENS is used to treat both chronic and acute pain associated with musculoskeletal problems (e.g., arthritis, low back pain), dental problems and procedures, bursitis, menstruation, urinary incontinence, surgical procedures, labor and delivery, fracture pain, and traumatic injuries. TENS is also used as an adjunct treatment for chemotherapy-induced nausea and vomiting.
A TENS unit consists of an electronic stimulus generator, which transmits electrical current to electrodes placed directly on the patient's skin. Most TENS units use two or four electrodes to transmit electrical impulses. The number of impulses (frequency), the pulse duration, and intensity can be adjusted. Some TENS units offer modulation, which allows the frequency, duration, and intensity to be intermittently changed, and a burst mode, which allows groups of rapid pulses to be applied at regular intervals. The treatment parameters (i.e., rate of stimulation, pulse intensity and duration, other settings) are based on the type of TENS unit used, the patient's medical condition, and response to stimulation.
The physiological mechanism of TENS pain relief is not fully understood, but two theories are have been proposed to explain it: gate control and endorphin release.
According to the gate-control theory, pain is experienced when certain small unmyelinated fibers are stimulated (the "gate" is opened). Pain is not felt when larger mylelinated fibers that inhibit the feeling of pain are stimulated (the gate is closed). The electrical currents produced by a TENS unit stimulate these large myelinated fibers, blocking pain stimuli transmitted by the smaller unmyelinated fibers.
According to the endorphin release theory, TENS is believed to stimulate the release of endorphins, peptides in the body that help inhibit the transmission of painful stimuli.
TENS units are available in desktop, handheld, portable, and wearable configurations, depending on the manufacturer and clinical applications for which the unit is designed. For example, some TENS units dedicated to
treating premenstrual pain and dysmenorrhea are smaller and configured with a belt clip and battery operation so the patient can wear the unit for the duration of pain treatment.
TENS is used in physical therapy, rehabilitation, primary care, hospital, chiropractic care, long-term care, and home-care settings, and is initially administered with close supervision of the patient to evaluate their response to treatment. Depending on their pain and associated medical condition, the patient may then given instructions on how to use the TENS unit at home according to a prescribed schedule.
Jennifer E. Sisk M.A., The Gale Group Inc., Gale, Detroit,