Electrical currents for pain control

physology of pain

Gate control theory

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

you can gate or interupt pain by distracting mechanisms?

interferential ES

delivered through two sets of electrodes from separate channels that intersect

intersection of waves cause higher amplitude when the currents are in the same phase (working together) and lower amplitudes when they are in opposite phases (working against each other)

the result of the interacting waves is pulse or beat. beat frequency is to 10 the difference b/w the frequencies of the original alternating current

it is believed…

Transcutaneous electrical nerve stimulation (TENS)

use of transcutaneous electrical stimulation to modulate pain

most common : biphasic

4 main types: conventional TENS, low-rate/acupuncture-like TENS, burst mode tens, electroacupuncture

conventional TENS

shorter duration, higher frequency pulses

comfortable sensation without ms control

stimulates the A-beta nerves to inhibit transmission of pain signals

usually delivered with pulses of 50-80

low-rate/acupuncture-like TENS

motor nerves are stimulated to produce a muscle contraction and/or brief stimulation of A-delta nerve fibers (quick pain stimuli) → releases endogenous opioids → the endogenous opioids bind to opiate receptors in the brain and act as neurotransmitters and neuromodulators (like morphine does)

only localized effect

uses pulse frequency od 2-10 pps

wavelength is usually around 200-300 microseconds

low rates TENS usually controls pain for 4-5 hrs after a 20-30 min treatment bc the half-life of endogenous opioids is usually 4-5 hrs

link waves lengths to the strength-duration curve

A beta sensory - conventional

motor and s delta - low-rate

burst mode TENS

is a current composed of a series of pulses delivered in groups known as bursts. it is generally delivered with a preset frequency and duration

believed to work through the same mechanism as low-rate TENS

figure 13-1 pg. 259

electroacupuncture

parameters

waveforms - pulsed biphasic, interferrential current, pulsed monophasic (premodulated) - high voltage pulsed current

electrode placement - on or around area and for inferential the channels must intersect

pulse duration - (conventional) 50-80 microseconds to depolarize A-beta fibers only; low-rate TENS 300-300 microseconds to depolarize motor nerves and A-delta fibers

frequency

applied continuously

current amplitude

• per patient tolerance. “moderately gentle sensation” for convention TENS and IFES

• to small motor twitch or “sting” for low rate TENS

treatment time

• can be continuous for conventional TENS

• Low rate or burst mode TENS; up to 20-30 min every two hours

• IFES - usually 20-30 mins. often with MHP or ice pack.