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TENS

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Definition

� Transcutaneous Electrical Nerve

Stimulation (TENS) is a method of

electrical stimulation which primarily aims

to provide a degree of pain relief

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(symptomatic) by specifically exciting

sensory nerves and thereby stimulating

either the pain gate mechanism and/or

the opioid system.

Mechanism of Action

Possible Pain Relieving Mechanisms;

�Activation of ‘pain-gating’ mechanisms.

�Stimulation of the descending painsuppression system and endogenous opiate mechanisms.

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mechanisms.

�The Central Biasing Theory

�Removal of the substances which stimulate pain nerve endings from within the damaged area

Pain Pathway

� Aδ and C fibres that carry noxious sensory information

� Aβ fibres carry

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� Aβ fibres carry non-noxious stimuli

The pain gate mechanism

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Opiate-mediated control

� Endogenous opioids� Endorphins

� Dynorphins

� Enkephalins

Neurophysiology background:�The brain can secrete its own analgesic

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�The brain can secrete its own analgesic substance such as endorphins to modulate pain.�Endorphins are neuropeptides that act on the CNS and peripheral nervous system to reduce pain. �They have the similar pharmacological effect as morphine.

Local vasodilatation

� The Central Biasing Theory:

The motivational affective mechanism of the limpic system explains emotional responses to pain. The body uses past experiences with pain to judge the

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experiences with pain to judge the intensity/severity of current pain

� Removes pain causing anti inflammatory agents.

Parameters used for TENS

� Waveforms

� Frequency or Rate

� Pulse width or Duration

� Amplitude or Intensity

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Waveforms

Square / rectangular

�Instantaneous rise

�Less skin irritating as

approaches sine wave

form

�For nerve damage

Triangular / spike�Rapidly rising, but notinstantaneous�More skin irritatingtherefore requiresfrequent movement ofelectrodes or shorter

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�For nerve damage

associated with pain

pathology

�For hypersensitive and

chronic pain patients

�Delayed, long-lasting

analgesia

electrodes or shortertreatment times to avoidskin irritation�For acute pain orresistant tissue�Immediate, short lastingpain relief

Frequency or Rate

High Frequency (80-120):

� Large myelinated fibers respond effective > 100Hz

� Immediate relief of pain

� Acute pain

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Low Frequency (1-20):

� Small unmyelinated fibers respond effectively at

<100Hz

� Increase endorphin production, thus analgesia

following stimulation

� Chronic pain

Pulse width or Duration

Pulse width Indications

50μs Large myelinated fibers (sensory touch)

100 - 150μs Normal neuromuscular system

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100 - 150μs Normal neuromuscular system

200 μs Small myelinated fibers

200 – 300 μs Patients with neurological damage

Amplitude or Intensity

� TENS units intensity ranges form 1 mA to 100 mA

� TENS is only effective when the patient actually feels the stimulus

� Patients need to increase the intensity

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� Patients need to increase the intensity when the body accommodates to the stimulus (when they don’t feel the stimulation anymore)

� Dying batteries can cause fading intensities

Types of TENS

� Conventional TENS or High Frequency TENS

� Acupuncture-like TENS (AL-TENS) or Low Frequency TENS

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� Brief TENS or Intense TENS

� Burst TENS

� Modulated TENS or Modified TENS

Conventional or High TENS

� Frequency – 50 Hz to 100 Hz

� Pulse Width – 20 μs to 60 μs

� Intensity – (0 mA to 30 mA).

� The intensity until a prickling or tingling sensation is felt.

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sensation is felt.

� Principle –Presynaptic inhibition by pain gate mechanism by stimulating Aα and Aβ fibres.

� Duration – 30 to 60 minutes once or twice daily.

Acupuncture or Low TENS

� Frequency – 1 Hz to 4 Hz

� Pulse Width – 150 μs to 250 μs

� Intensity – 30 mA to 60 mA.

� applied to acupuncture points or motor points of muscle in the segmentally related myotome.

� Principle –This stimulates the high threshold Aδ

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� Principle –This stimulates the high threshold Aδ and C fibres, which lead to release of endogenous opioids and provides further sensory input from muscle spindle afferents (chemical theory).

� Duration – 20 to 30 minutes once a day.

Brief or Intense TENS

� Frequency – More than 100 Hz

� Pulse Width – 150 μs to 250 μs

� Intensity – Highest level tolerated by the patient.

� Principle –Activity in cutaneous Aδ

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� Principle –Activity in cutaneous Aδ afferents induced by intense TENS produce peripheral blockade of nociceptive afferent activity (Central biasing mechanism).

� Duration – 30 to 60 minutes once or twice daily.

Burst TENS

� Burst TENS is a series of pulses (i.e. a train), repeated 1-5 times a second, commonly twice.

� Each train or burst consists of a number of individual pulses at the usual

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of individual pulses at the usual conventional TENS frequencies of 50 Hz to 100 Hz but at higher intensity.

� It combines both the conventional and acupuncture-like TENS and

� therefore provides pain relief by both routes.

Modulated or Modified TENS

� In modulated TENS the pulse length, frequency, and amplitudes can be constantly and automatically varied.

� This cyclical variation is believed to prevent adaptation of the nerves to the

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prevent adaptation of the nerves to the current (no accommodation)

� is particularly appropriate as a variant of conventional TENS used over long periods.

Electrode Placement

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Electrode Placement

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Electrode Placement

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The position of electrodes and electrical characteristics of TENS when used to manage labour pain

Electrode Placement

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Contraindication

� Someone with a pacemaker

� Someone with undiagnosed pain.

� Someone with a heart condition

� On head or neck of someone with epilepsy

� Someone with venous or arterial thrombosis or thrombophlebitis

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thrombophlebitis

� Someone with indwelling phrenic nerve or urinary bladder stimulators

� Near operating diathermy device

Contraindication

� Around the head

� On the eyes

� Over mucosal surfaces

� Using electrodes on infected skin

� Electrodes across the chest of a patient with cardiac disease

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cardiac disease

� Electrodes should not be placed near carotid artery in the anterolateral region of the neck. There is a potential risk that stimulation at this site might cause heart block by exciting the vagus nerve.

Precautions

� Areas of skin irritation, damage or lesions

� Areas with impaired sensation

� Over abdominal, lumbosacral or pelvic regions during pregnancy other than for labor/delivery

� Tissues vulnerable to hemorrhage or hematoma

� Athletes should not be permitted to participate in

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� Athletes should not be permitted to participate in sports while under the influence of TENS analgesia

� Extreme caution is needed with patients taking narcotic medication or who are known to have hyposensitive areas.

Precautions

� Incompetent patients may not be able to manage the device and it must be kept out of reach of children.

� For patients with diagnosed malignancies that have been diagnosed as terminal, TENS can be used for pain control with informed consent of

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used for pain control with informed consent of the patient.

� Otherwise, TENS should not be used when malignancies are present.

References

1.Tim Watson. http://www.electrotherapy.org/modality/transcutaneous-electrical-nerve-stimulation-tens

2.http://www.answers.com/topic/pain-1

3.http://www.david.curtis.care4free.net/painrev.htm

4.Transcutaneous Electrical Nerve Stimulation. McGill Lecture Notes –January 22nd, 2002

5.Mark Johnson. Transcutaneous electrical nerve stimulation (TENS).

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5.Mark Johnson. Transcutaneous electrical nerve stimulation (TENS). P 259-286

6.Foster A, Palastanga N. Clayton’s electrotherapy,9th edition, AITBS Publishers, pp 100- 106

7.Singh Jagmohan. Textbook of Electrotherapy, 2 edition, 2012;pp 129 – 133

THANK YOU

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