Accutech | Medical Device

Transcutaneous electrical nerve stimulation (acronym TENS) is the use of electric current produced by a device to stimulate the nerves for therapeutic purposes. TENS by definition covers the complete range of transcutaneously applied currents used for nerve excitation although the term is often used with a more restrictive intent, namely to describe the kind of pulses produced by portable stimulators used to treat pain.^[1]^{[page needed]} The unit is usually connected to the skin using two or more electrodes. A typical battery-operated TENS unit is able to modulate pulse width, frequency and intensity. Generally TENS is applied at high frequency (>50 Hz) with an intensity below motor contraction (sensory intensity) or low frequency (<10 Hz) with an intensity that produces motor contraction.^[2]

Stimulation of muscle contraction

The use of electrical stimulation to stimulate muscle contraction is known as neuromuscular electrical stimulation (NMES) or functional electrical stimulation (FES). NMES/FES therapies apply pulses of electrical current to target muscle groups to stimulate active motion, strengthen muscles, and prevent muscle atrophy.

In NMES/FES, electrodes are placed initially on the belly of the muscle that is to be stimulated. AC electrical stimulation is then applied at low levels (threshold levels for muscle movement). Based on muscle responses to the threshold stimulation, electrode positions are adjusted until the motor points of the muscle (optimal positions for generating muscle movement) are found. Electrodes are then secured at these optimal positions.

After the electrodes have been placed, parameters for NMES/FES are programmed into the electrical stimulator unit. Parameters include the amplitude of the electrical pulse, the duration of each pulse, the frequency of pulses, the duration of on/off (activation/rest) periods during the treatment session, ramping modulation (gradual increases and decreases) in stimulation, and duration of the treatment session. The maximum pulse amplitude recommended for NMES/FES is generally the maximum amplitude that can be tolerated by a given patient. Regarding pulse duration, there remains some ambiguity about the optimal duration time of each pulse; current practices suggest that pulse duration be set between 50 and 1000 microseconds. Pulse frequency tends to range from 30 pulses per second to 100 pulses per second. Since continuous electrical stimulation leads to early muscle fatigue, treatment sessions include rest periods between activation periods. The duration of “on” (activation) periods is typically 10–15 seconds; “off” (rest) periods can last up to one or two minutes. Treatment sessions may last between 10 and 20 minutes, and usually do not exceed one hour.

Electrical stimulation can begin after parameters are set. In general, the intensity of the stimulation is increased from contraction to contraction within a given session, and is also increased from session to session, depending on how well the patient tolerates the increases.

NMES/FES is usually approved by insurers for post-surgical rehabilitation and rehabilitation after immobilization (after a limb has been in a cast or splint). This form of electrotherapy is typically not approved for spinal cord injuries or for muscles that have been denervated.