Describe TENS and explain in detail its frequency, intensity, application, positioning of electrodes and types of TENS.
Describe TENS
Transcutaneous electrical nerve stimulation (TENS) is the use of transcutaneous electrical stimulation to modulate pain. TENS can be applied using various waveforms and a variety of other electrical stimulation parameters. The effect and use of TENS depends upon gate control theory and pain modulation.
PARAMETER FOR PAIN CONTROL
Waveform
TENS units output a pulsed biphasic current.
Although less often used, pulsed monophasic currents, such as high-voltage pulsed current, can also be used to reduce pain. A pulsed biphasic or monophasic waveform requires only two electrodes. Essentially, as long as the stimulus has the necessary pulse duration, amplitude, and rate of rise to stimulate the appropriate nerves, it can be effective for pain control.
Frequency
Selection of pulse frequency for pain control depends on the desired mode—conventional, low-rate, or burst.
Conventional TENS, the pulse frequency is set between 100 and 150 pps,
Low-rate TENS, the pulse frequency is set below 10 pps.
TENS units that have burst mode available are generally pre-set by the manufacturer to provide 10 or fewer bursts each second, with pulses within the burst being at 100 to 150 pps, thereby attempting to combine the effects of conventional and low-rate TENS, or to enhance endorphin release by maintaining the “low rate” and delivering more current.
Current amplitude(intensity)
To control pain with electrical stimulation, the treatment should be comfortable. For conventional TENS, it is generally recommended that the amplitude be set to produce a gentle sensation that is perceived as tingling or vibration.
Although some recommend a strong or maximally tolerated level of sensory stimulation for this application.
For low-rate and burst TENS to be effective, the amplitude must be sufficient to produce a muscle contraction that can be seen or palpated by the clinician.
Treatment time
When electrical stimulation is used for pain control with conventional TENS, the stimulation may be applied whenever the patient is in pain or would be expected to be in pain.
Low-rate or burst mode TENS should be applied only for a maximum of 20 to 30 minutes every 2 hours.
Electrode placement
When electrical stimulation is applied for pain control, a variety of electrode placements can be effective.
Placement around the painful area is most common.
Placement over trigger points or acupuncture points,
If the area is in a cast or local application of the electrodes is not tolerated, the electrodes can be placed proximal to the site of pain along the pathway of the sensory nerves supplying the area.
If two currents, and thus four electrodes, are used, the electrodes can also be placed to surround the area of pain.
For all applications, the electrodes should be at least 1 inch apart.
TYPES OF TENS
Conventional TENS
Conventional TENS, also known as high-rate TENS, uses short-duration higher-frequency pulses at a current amplitude sufficient to produce a comfortable sensation without muscle contractions to modulate pain.
- Frequency — 100–150 Hz
- Pulse width — 100 and 500 ms
- Intensity — 12–30 mA
Low-rate/Acupuncture-like TENS
Low-rate TENS, also known as acupuncture-like TENS, which involves repetitive stimulation of motor nerves to produce brief repetitive muscle contractions or twitches, or of nociceptive A-delta nerves to produce brief sharp pain, can stimulate endogenous opioid production and release. To achieve this, longer pulse durations and higher current amplitudes than used for conventional TENS are required because motor nerves, and possibly A-delta nerves, must be depolarized. A pulse frequency range of 2 to 10 pps is usually used for this application.
- Frequency — 1–5 Hz
- Pulse width — 100 and 500 ms
- Intensity — 30 mA or more
Burst mode TENS
Burst mode TENS, the stimulation is delivered in bursts, or packages, with a number of pulses in each burst.
Burst TENS is a series of impulse repeated for 1–5 times per second. Each train (burst) lasts for about 70 ms. The benefits for the Burst TENS are that it combines both the conventional and acupuncture like TENS and thus provide pain relief by the both routes.
Electroacupuncture
Electrical stimulation may also control pain when the electrodes are placed on the skin overlying acupuncture points. This method of application is thought to stimulate energy flow along acupuncture meridians that connect acupuncture points in the bod
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