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Chapter 12: TENS
586
QUICK POINTS
• Physiotherapists use TENS or transcutaneous
electrical nerve stimulation to treat pain and muscle
re-education.
• Common adjustments on all TENS devices are the
pulse width, frequency and intensity. Many TENS
devices also include preprogrammed modes for
treating specific patient issues.
• Common issues the biomed will experience with the
TENS device are shin burns, intermittent or no
output, all probably due to broken treatment wires or
poor application by the physiotherapist.
• Specific to the TENS device, the biomed verifies the
output accuracy.
TENS CHALLENGE QUESTIONS
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587
1. What is the main purpose of a TENS device?
2. Does TENS therapy cure the reason for pain?
3. What are the three common adjustments on all
TENS devices?
4. How does TENS treat pain?
5. How does TENS therapy re-educate muscles?
6. What are the two most common issues the biomed
will experience with the TENS device?
7. Outline the specific tests a biomed performs on the
TENS device during a PM.
CLINICAL INFORMATION
Chapter 12: TENS
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Physiotherapists use TENS or transcutaneous
electrical nerve stimulation to treat pain and muscle re-
education. TENS devices send electronic pulses across the
surface of the skin and along the nerve strands to stimulate
the nerves. TENS therapy does not cure the original cause of
the pain but does provide temporary relief or reduction of
pain. A Physiotherapist may use TENS treatment as an
alternative to ultrasound or diathermy, due to metal in the
treatment area.
What conditions is TENS treatment used for?
• labor and delivery
• migraine and tension headaches
• acute pain from sports and other injuries
• arthritis
• tendentious and bursitis
• cancer pain
• wound healing
How is TENS therapy applied?
• Plug the TENS in or ensure the batteries are fully
charged.
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589
• Clean the area using rubbing alcohol, put a thin coat
of gel on the bottom of each electrode and apply them
to the skin. The electrodes are placed strategically
near the treatment area.
• Connect the electrode wires to the electrodes and
TENS device.
• Adjust the controls slowly to the correct setting until
the patient feels a tingling feeling. A physiotherapist
can adjust the TENS pulse width, frequency,
intensity. Alternatively, some TENS devices include
preprogramed modes available to the Physiotherapist
such as pulsed, burst or continuous output modes.
How does TENS therapy relieve pain?
There are two theories on how TENS reduces pain
in the body. One theory is that TENS therapy stimulates
certain chemicals within the body (endorphins and
Chapter 12: TENS
590
enkephalins) which reduces the patient’s pain. Another
theory called gate theory believes the TENS signals pass
through a gate to the brain, instead of the pain signals.
How does TENS therapy re-educate muscles?
The TENS electrical stimulation will cause
muscle contractions and improve blood circulation. The
circulation is improved as the blood flows in and out of the
area with contractions. The contractions and increased
circulation helps re-educate a muscle.
COMMON FEATURES of TENS
Output Intensity:
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591
The output power is used by the physiotherapist
to adjust the intensity of the TENS treatment current. This is
used to adjust the comfort level, during treatment.
Pulse width/rate Adjustment:
The physiotherapist may have control over the
pulse rate and width to adjust them to treat the patient’s
condition.
Mode Selector:
The mode selector allows the user to select
various stimulation modes. Some TENS devices have
numerous modes, specifically available to treat specific
conditions.
Treatment Timer:
The physiotherapist sets the treatment timer to
ensure the correct period of treatment time is performed.
Some TENS devices will only enable an output, while the
timer is enabled and will disable the output when treatment
time is ended.
HOW TO TEST/PM THE TENS
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Always refer to the manufacturer's service manual for a
complete recommended PM guideline. Following is a
generic guideline only!
Perform a visual inspection:
• Ensure the overall TENS device has no obvious
issues such as a broken case, etc.
• The biomed should also check for the electrodes and
cables to be in good condition. The biomed should
measure all wires for continuity by using an
ohmmeter to ring the individual wires, while moving
and placing tension on the wires.
Ensure all user controls are operational:
• Ensure all the user controls are functioning during
your tests. A biomed will often find user controls not
working during their testing. If a button/control is not
working, repair it prior to placing the TENS device
back into service.
Ensure the TENS output is accurate:
• A resistor is used to load the output (about 1KΩ) and
an oscilloscope is used to measure the frequency,
current or voltage levels. The output should be within
manufacturer’s specifications. If available, the
manufacture may have a specific method and should
be followed. The various modes available are also
tested.
Treatment timer:
• While testing the TENS device, ensure the timer is
accurate.
Chapter 12: TENS
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• If the treatment timer accuracy is not within the
manufacturer’s specifications, the biomed must
repair the TENS timer.
Ensure the TENS device is electrically safe:
• Measure the ground in resistance.
• Measure the chassis leakage.
• Measure the applied part leakage, if required.
Always perform a final functional check:
• As a final test, the biomed should do a quick
operational test to ensure proper operation, prior to
placing it back into service.
• All operation, controls and alarms should operate as
per the manufacturer's design.
Ensure your documentation is accurate:
• All repairs and performance tests need to be
documented so that they can be retrieved at any time.
• This documentation should include all parts used for
repair and that all the above tests showing the
equipment is within manufacturers and local
authorities acceptable limits.
• These documents may be used legally to validate the
proper maintenance was performed by the biomed.
Ensure your documentation is accurate!
What do I do if any of my checks fail?
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• If any device maintained by the Biomed fails a
functional test and/or electrical safety, it is the
biomed's responsibility to pull it out of service!
• Failure means a patient safety issue exists!
• Fix the issues prior to placing the TENS device back
into service!
QUICK SERVICE TIPS
Skin burns:
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• Ensure there are no exposed treatment wires. If a
wire touches the patient during treatment, burns can
occur at the contact sight. The physiotherapist may
complain about skin burns which can occur at the
site, where an exposed wire is touching the patient.
• High contact resistance between the patient's skin
and treatment electrodes may cause the skin to
heat/burn between the patient’s skin and treatment
electrode(s). Also, if the resistance is high between
the electrodes and patient's skin, the physiotherapist
may have to increase treatment output to get the same
general treatment stimulation which may cause a
higher than normal battery replacement. If the
physiotherapist complains about reddening of the
skin at the treatment area and a higher than normal
battery usage, the biomed should suspect potential
problems with skin contact resistance caused by
either poor electrodes or poor electrode application.
Intermittent or no output:
• This is a common issue the physiotherapist will
question.
• Intermittent or no output is usually caused by
treatment wire breaks. The biomed can measure wire
continuity by using an ohmmeter to ring the
individual wires out while moving and placing
tension on the wires.
• Treatment shocks may be cause by intermittent
connections within the treatment lines.
High current level check:
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• Current levels of greater than 50mamps (RMS) may
cause ventricular fibrillation. Ensure the device
under test cannot create currents greater than
50mamps. If the device can create a current greater
than 50mamps, inform the physiotherapist.
CHALLENGE ANSWERS
1. The main purpose of a TENS device is to treat pain
and muscle re-education.
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597
2. TENS therapy does not cure the original cause of
the pain but does provide temporary relief or
reduction of pain.
3. The three common adjustments on all TENS
devices are the pulse width, frequency and intensity.
4. There are two theories which are it stimulates
certain chemicals within the body which reduces the
patient’s pain or it the pain signals to the brain.
5. TENS causes muscle contractions and improve
blood circulation which helps re-educate a muscle.
6. The two most common issues the biomed will
experience with the TENS device are either broken
treatment wires or poor pad contact by the
physiotherapist.
7. The specific tests a biomed performs on a TENS
device during a PM are:
• Ensures the TENS output is accurate.
• Ensures the treatment timer is working.