TRANCUTANEOUS ELECTRICAL
NERVE STIMULATION -TENS
RHPT 353 – 1435-1436-1ST SEMESTER
Lecture outlines
2
This lecture deals about transcutaneous electrical nerve
stimulation (TENS) in following categories;
 Physiology of pain

Basic terminologies & Definition of TENS

Physiological & therapeutic effects of TENS

Indications & Contra indication of TENS

Technique of application of TENS
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Lecture objectives
3
At the end of lecture the student is able to

Define and outline the principle of TENS.

List the physiological effects, therapeutic effects, indication,
& contraindication of TENS

Select the appropriate TENS dose

Demonstrate & apply TENS on her/ his colleague
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PHYSIOLOGY OF PAIN
4
Definition of pain:

Pain is an unpleasant sensory and emotional
experience associated with tissue damage. It is a
protective mechanism that warns us that there is
something wrong and can provoke body response
to avoid further injury.
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PHYSIOLOGY OF PAIN
5
Pain Process
The pain process started whenever there is tissue damage which
stimulate the nociceptors
Nociceptors
They are receptors responsible for the reduction and transmission of
pain impulses.
They are free nerve endings that are widely distributed throughout
the body and stimulated with noxious intense stimulus damaging the
tissue as intense heat, cold, strong mechanical deformation and
chemical substances.
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Types of Pain
6
Acute pain
- It is pain of sudden welldefined onset and associated
with tissue damage.
- It is usually accompanied by
signs of hyperactivity in the
autonomic nervous system.
- Signs & symptoms of
inflammation are very strongly
perceived – leads to very
intense pain
Referred Pain
Chronic Pain
- It is pain extending beyond the
- Pain originating in deep
normal course of injury or illness.
structures and viscera
- It is usually lasting 6 months or
which is perceived in some
more.
superficial sites as skin.
- Chronic pain produces significant
- The actual damage
changes in personality, life style,
occur in area and pain is
and functional ability.
felt in other remote area.
- The signs & symptoms of
inflammation is very less – leads to
mild pain in certain activities.
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TYPES OF NERVE FIBERS
7

The nervous system responds promptly to all kinds
of stimuli. The nerve fibers have different of
transmitting the impulse depending on the diameter
of the nerve and other factors.
A fiber
B fiber
C fiber
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A fiber
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Large myelinated, fast conducting, motor and sensory nerve fibers.
A delta
fibers
Mediate afferent
information
pertaining to touch
proprioception
A alpha
and kinesthesia.
and beta
The smallest of myelinated A
fibers mediates nociceptive
information primarily to
superficial sharp, easy to
localize pain.
A
fibers
A
gamma
fibers
fibers
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Convey
information
relative to
changes in
muscle length.
9
B fiber
Smaller and slower
conducting myelinated,
efferent, preganglionic fibers of the
autonomic nervous
system
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C fiber
Unmyelinated post ganglionic
fibers of the synaptic nervous
system. Unmyelinated or poorly
myelinated afferent fibers of
the peripheral nerves. Group C
fibers are small and slow
conducting.
It mediates nociceptive
information, more indication
of deep, hard to locating
pain of chronic variety
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Note
10

Myelinated nerve fibers conduct an electrical current
at faster velocity then non-myelinated fibers C.

Larger diameter fibers also has a rapid conduction
velocity. So The largest myelinated afferent nerve
fibers ( A alpha and beta) are the most rapid
conducting and also the easiest to excite or
depolarize.
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Pain pathway
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Once nociceptors are stimulated the pain impulses passed to
the spinal cord along two types of afferent nerve fibers:
A delta fibers:
Conduct impulses of acute sharp fast pain at speed of
6-30 m/sec.
C fibers:
Conduct impulses of chronic, dull slow pain at speed of
0.5-2 m/sec.
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Pain pathway
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
The nerve impulses giving rise to conscious pain travel in 4
regions of nervous system
1. The peripheral nervous system (nociceptors & afferent
pathways)
2. Spinal cord (Dorsal horn, Spinothalamic tract & multisynaptic
ascending system)
3. Brain stem & thalamus
4. Cerebral cortex
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First order neuron
13
• Start at peripheral receptor
• Ends in the dorsal horn of the spinal cord
Second order neuron
• Start at dorsal horn of the spinal cord
• Ends in the thalamus
Third order neuron
• Start at thalamus
• Ends in the sensory cortex
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Afferent nerve fiber distribution
14
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Neurotransmitter –
Substance “P” is
believed to be the
neurotransmitter
involved at the
synapse between 1st
& 2nd order neurons.
After synapse – the
2nd order neuron cross
to the opposite side
of the sp. cord &
ascend to central
pathways.
Synapse
15
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The ascending tracts
carry the 2nd order
neuron (Sp.Cord) through
central pathways
concerned with
nociception are Lateral
Spinothalamic tract(LST)
& Multi Synaptic
Ascending system (MAS).
The 2nd order neuron end
in thalamus & synapse.
Pathways – Ascending tracts
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Pathways – Ascending tracts
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Neuromodulation of Pain
18

The passage of nociceptive information is
interrupted along several stages of ascending
nociceptive pathways to produce Neuromodulation
of pain.
1. Peripheral
2. Spinal segmental
3. Supraspinal
4. Cortical
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Neuromodulation of Pain Peripheral level
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

Intervention involves a ↓ in the amount of those
chemicals released in response to tissue damage which
are responsible for nociceptor activation.
S.W.D, Hot Packs – Heat – Produce local vasodilatation
- ↑ blood flow – removal of these chemicals.

Ultrasound – Cell permeability - ↓ amount of exudates.

Ice - ↓ amount of exudates
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Neuromodulation of Pain Spinal segmental level
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
It involves inhibition of activity of Aδ & C fibers
before ascends further in neural axis.

The inhibition – Pain modulation theories – Melzack
& Wall
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Neuromodulation of Pain Supraspinal level
21

The placebo effect & counter irritation are also
believed to operate at this level - Pain modulation
theories – Melzack & Wall
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Neuromodulation of Pain Cortical level
22

It involves modification of individual perception &
interpretation of pain.

Behavior modification & cognitive strategies –
psychological approach.
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Pain modulation Theories
23
Gate control theory
Descending inhibition of pain
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Gate Control Theory– by Melzack & Wall
24

It serves as a major impetus to the commercial
production of TENS.

The modulation of pain transmission by altering
afferent input to the spinal cord is called gate
control theory.
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Gate Control Theory– by Melzack & Wall
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According to this theory:

Pain impulses are relayed from the periphery to the spinal
cord through thin myelinated A delta and unmyelinated C
fibers which synapse with neurons and interneurons in the
dorsal horn.

These dorsal horn neurons also received non-nociceptive
input from other fibers as large myelinated low threshold A
beta fibers that carry353
touch
sensation.TENS
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
Stimulation of A beta fibers inhibits pain transmission
at the level of spinal cord as the following:
- A beta fibers give off collateral which impinge on
the terminations of A delta and C fibers in laminae
of the dorsal horn where they produce presynaptic
inhibition of pain impulses by secretion of substance
called gama aminobuteric acid (GABA) which inhibit
substance p secretion, thus preventing pain impulses
from reaching higher centers.
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Stimuli – Aδ + c fiber –
Dorsal horn – open gate for
pain.
Stimuli – Aβ – Presynaptic
inhibition – closing of gate
for pain.
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Descending inhibition of pain
28
When stimulation of A delta fibers, the pain impulse ascend up
to the higher brain centers. Once the pain impulses have reached
the higher centers, they activate certain areas in the midbrain
which send
descending inhibition impulses that travel back down
to the spinal cord where they inhibit transmission of pain impulses.
Descending inhibition of pain.
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Definition
29

Transcutaneous electrical nerve stimulation (TENS) is a non
invasive method of electrical stimulation through intact skin
and aimed to relief pain by specifically exciting peripheral
nerves.

Or it is the application of electrical stimulation to skin via
surface electrode to stimulate nerve fibers to relief pain.
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Types of TENS mode
30
Conventional
TENS (High
TENS)
Brief intense
TENS
Burst mode
TENS
Acupuncture
(Low) TENS
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1. Conventional TENS (High TENS)
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Conventional TENS (high frequency, short pulse , low intensity).
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Conventional TENS (High TENS)
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
Usually use stimulation at a relatively high frequency.

Hi TENS is effective in treatment of acute pain of
superficial nature as well as chronic pain. Relief pain
through gait control theory.

Patient sensation is tingling ,and paresthesia
sensation.
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Conventional TENS (High TENS)
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
Parameters:
-
Low intensity: 12-30mA
-
High frequency: 100-150 Hz
-
Pulse duration: 50-80us
-
Duration: 20-60min
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2. Acupuncture (Low) TENS
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Acupuncture TENS (low frequency, long pulse, high intensity)
Stimulation parameters:
-Low frequency: 1-5 Hz
-High intensity: 30mA or more
-Long pulse duration: 150-300us
-Duration: 30-40min
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2. Acupuncture (Low) TENS
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


Low TENS is effective in treatment of
chronic pain of damaged deep tissues
Patient sensation is paresthesia , pulse
muscle twitch seen.
Pain relief through descending pain
suppression system
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3-Brief intense TENS
36
It produce rapid onset but
short term pain relief
Use during painful
procedures as wound
debridement, joint
mobilization.
Parameters:
•
•
•
•
•
Amplitude : to patient’s tolerance.
Pulse rate: 80-150Hz
Duration: 15 min
Pulse duration 50-250us
Duration of pain relief:
temporary.
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4- Burst mode TENS
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
It provide a packaging of stimuli groups ranging
from 1-10

It combine characters of both low and high TENS

Relief pain through endogenous opiate
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4- Burst mode TENS
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
Produce more comfortable contraction.

Parameters:
-
amplitude: comfortable paresthesia
-
Frequency: 50-100Hz
-
Pulse duration: 50-200 us
-
Duration: 20-30min
-
Duration for pain relief: long lasting
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Indications of TENS
39
Acute and chronic
post operative pain
Musculoskeletal
pain” sprain, strain,
myofascial”
Neurological pain as
in, trigeminal
neuralgia, and
peripheral nerve
injuries.
Obstetric pain “
during delivery”
Arthritic pain “
osteoarthritis,
rheumatoid”
Acute and chronic
low back pain
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TENS
Other recent indication of TENS:
40
Improve
cutaneous blood
flow
Anti emetic
effect
Wound healing
Fracture healing
(non-united fracture)
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Reduction of
neglect in post
stroke patients
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Contraindication
41
Anesthetic
skin
Patient at
risk
Over the
carotid sinus
Pregnancy
Allergy
Epilepsy
Treatment
while driving
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Parameters used in TENS unit
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
-

-
Waveforms :
biphasic waveform is used.
It may be square ,rectangular, triangular, or sine
wave. Each type used according the patient’s
case as the triangular used for acute pain.
Frequency :
High TENS 80- 120 Hz as in acute pain
Low TENS 1-20 Hz as in chronic pain
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Parameters used in TENS unit
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
-

-

-
-
Pulse width:
Vary from 50-400 us
For normal neuromuscular system100-150us
For neurological damage 200-300us
Amplitude
based on the patient’s sensation
Modulation:
There is a variation in either pulse duration, frequency, or
amplitude parameter in a cycle fashion
This help to overcome nerve accommodation.
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Types of Electrodes
44
Carbon rubber
Self adhesive
Aluminum foil
• coated with a conductive gel
prior to attachment to the skin.
• become more popular
• Lint pad covering
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Advantage of TENS
45

Non invasive

Portable

Safe

Cheaper

Few contraindications and precaution

Non addictive
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Disadvantage
46

Fail of patients to tolerate the sensations

Skin irritation due to allergic reaction to gel

Chemical burn

Some patients fail to respond to the treatment
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Electrode placement:
47

Over the painful site, or trigger point.

Acupuncture point proximal and distal to the painful area.

Over the same dermatome. In case the pain is distributed across a
large area with no definite trigger point.

Peripheral nerves. Electrodes are placed in the line of the nerve
where it is particularly superficial. This method is effective in
treatment of neurological pain.
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Electrode placement:
48

Spinal nerve root associated with pain. The electrodes should be
placed parallel to the spinal column.

Contiguous placement. In conditions such as postoperative
incisions, lacerations in which direct electrode placement is
contraindicated as in incisional pain. The electrodes are placed
parallel and approximately 1cm from the incision using 2
electrodes or in crossed pattern if 4 electrodes are used.
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Treatment setup and application
49

Prepare the patient.

Adjust output parameters.

Place the electrodes in position.

Increase the output intensity slowly to the desired sensation level
according to the patient. Usually with conventional TENS the subjects feel
tingling sensation with no muscle twitch, while with acupuncture TENS
subjects feel more strong sensation but not unpleasant with visible muscle
contraction.
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TENS
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Electrode positions for common pain conditions (A) anterior view,
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Electrode positions for common pain conditions (B) posterior view
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Duration and Frequency of Treatment
52

Conventional TENS may be used as needed, but caution should
be used when applied while the patient is sleeping.

Patient response usually immediate ( high TENS), but adapt
quickly to this type of stimulation (the reason many unit have
included modulation modes).

Acupuncture TENS and burst TENS may be given as needed in
treatment bouts not exceeding 30 minutes and may be repeated 3
or 4 times daily.
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TENS Application in Non-united Fracture
53
Treatment Parameters
 Frequency:
120 Hz
 Pulse duration:
300 μsec
 Intensity:
barely sensed by the patients (lowest
possible)
 Duration:
1 hour /session, 4 times daily
Electrodes placement
 If the fracture is enclosed in a blaster cast electrodes
should be placed proximal and distal to the cast.
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TENS

If the fracture site is free of casting, use two electrodes
one placed on either side of the of the fracture site.
54
Electrodes placement for non-union fracture with
the cast present.
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Electrodes placement for non-union fracture
with no cast present.
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Precautions
56

Intense or prolonged stimulation may result in
muscle spasm or muscle soreness.

Improper use can result in electrode burn or skin
irritation Contact dermatitis may occur after
prolonged use.

Careful cleansing of the skin and the use of
different sites for the electrodes help to avoid that.
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