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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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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

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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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• 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

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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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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.

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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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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.