3 - Electrical currents for Pain Relief

What is the Gate Control Theory of pain?

Activation of nerves that carry vibration, stretching and mechanoreception inhibit the transmission of noxious (pain) signals from the spinal cord to the pain

What is interferential ES?

• ES delivered through two set of electrodes from separate channels that interest

• The result of interacted waves is pulses or beats

• Beat frequency is equal to the difference between two frequencies

What happens when intersecting interreferential ES waves are in the same phase?

It causes higher amplitudes

What happens when intersecting interferential ES waves are in opposite phases?

It causes lower amplitudes

Why is interreferential believed to be more comfortable than other forms of ES?

A lower amplitude current is perceived at the skin while higher amplitude waves are working at deeper tissues

What is interferential current used to treat?

Used to decrease pain associated with inflammation and ischemia

What is a TENS unit used for?

Used to modulate pain

What is the most common wave form used with a conventional TENS unit?

Biphasic

What is a conventional TENS?

• Shorter duration, higher frequency pulses

• Comfortable sensation without ms contractions

• Stimulates A-beta nerves (inhibits transmission of pain)- look at the chart

• Gating only occurs when TENS is applied

• Tries to interrupt the pain-spasm-pain cycle

What is a low-rate/acupuncture-like TENS unit?

• Small amount of motor nerves are stimulated to produce contractions and A-delta fibers (quick pain) are stimulated briefly - look at the chart!

• This causes a release of endogenous opioids which bind to opiate receptors in the brain (works like morphine)

How long does low-rate/acupuncture-like TENS control pain?

4-5 hours after a 20-30 min session (4.5 hrs is the half-life of endogenous opioids)

What is a burst mode TENS?

• Composed of a series of pulses delivered in groups

• Delivered with a preset frequency and duration

• Works through the same mechanism as low-rate TENS

• Fig13-1, pg 259

What wave forms can be used with a TENS unit?

• Pulsed biphasic - TENS

• Interferential current - alternating

• Pulsed monophasic (modulated) - high voltage pulsed current - alternating current used for pain

Where are the electrodes placed when using a TENS unit?

• On or around the area

• For interferential, the channels must intersect

What is the pulsed duration/wave length for conventional TENS?

50-80 microseconds to depolarize A-beta fibers

What is the pulse duration/wave length of the low-rate TENS unit?

200-300 microseconds to depolarize motor nerves and A-delta fiber

What is the frequency of a convential TENS unit?

• 100-150 pps

• Same for burst but administered in 10 bursts per second

What is the frequency of a low-rate/acupuncture TENS unit (or burst)?

2-20 pps

How is a TENS unit applied?

No on:off, it is continuous

What should the current amplitude be when using TENS (or IFES)?

Whatever the patient can tolerate - should be gentle (MODERATELY GENTLE)

What should the sensation be like when using low-rate TENS?

Small motor twitch or stinging

What is the treatment time for a conventional TENS unit?

Can be continuous

What is the treatment time for a low-rate/acupuncture TENS unit?

• 20-30 min ever 2 hours

What is the treatment time for IFES TENS?

20-30 min and often combined with ice or MHP

What form of ESTIM is usually often combined with MHP or ice pack.

IFES (for 20-30 min)

What type sensation should conventional TENS and IFES produce?

A gentle sensation