4.1) electrical stimulation for pain modulation (not finished)

direct current

has charge, true anode, and cathode

Continuously used for iontophoresis

alternating current

has a waveform

no IPI

has frequency

continuous or interrupted

pulsed current

has a waveform

is mono or biphasic

has pulse/phase duration

has IPI

duration * amplitude =

pulse charge

steps of peripheral nerve activation

alpha, beta, delta, denervated muscle

(motor, sensory, autonomic) (myelinated --> unmyelinated)

strength-duration curve

subsensory, sensory, motor, noxious

carrier frequency modulation used only for

burst modulated AC currents

- russian waveforms

- interferential waveforms

burst frequency

number of bursts per second

transcutaneous electrical nerve stimulation (TENS)

complimentary treatment - still need to address impairments and function

can be used for acute and chronic pain conditions

TENS is the common name for

stim for pain modulation

gate theory

stimulation of large diameter afferent inhibits the nociceptor responses in the dorsal horn

ex- like grabbing hand and rubbing it after hitting it on something

main mechanisms

activation of peripheral opioid receptors

activation of CNS opioid receptors

Stimulation and neuropathways

stim may change endogenous neurotransmitters and affect plasticity of NMDA pathways

fiber activation at sensory level of TENS goal

is three or more times sensory threshold

sensory threshold is when

the pt first starts feeling a little tingle

motor threshold is when

the pt first feels a small movement

fiber activation at motor level of TENS

activate motor and sensory - benefits of contraction

more than 2 times motor threshold

high frequency of TENS

more than 50 pps

high frequency mechanisms

peripheral, SC, and supraspinal effects

- activation of delta-opioid

- GABA

low frequency of TENS

less than 10 pps

low frequency mechanisms

peripheral, SC, and supraspinal effects

- activation of mu-opioid

- GABA

if someone is taking opioids

low frequency is not gonna have an effect because the medication is already attached to the mu receptors

different frequencies of TENS activate

different neurotransmitters to decrease sensitization

sensory treatment duration

to fit intervention goal

sensory duration of analgesia (the effect)

length of treatment plus some

motor treatment duration

30-40 min - low frequency

10-15 min - high frequency

motor duration of analgesia

hours after treatment session

noxious/painful treatment duration

10-20 min

noxious/painful duration of analgesia

hours after treatment session

duration of analgesia definition

more energy in = longer duration of analgesia

sensory dosing intensity/amplitude

3 times sensory threshold

strong but comfortable

motor dosing intensity/amplitude

2 times motor threshold

noxious/painful dosing intensity/amplitude

sharp, prickly, stringing pain sensation

more than 3 times sensory and more than 2 times motor thresholds

when to choose between using sensory, motor, noxious

tissue type

patient presentation (high/low irritability)

patient preference

adaptation occurs with

constant sensory input

adaptation

reduced perception of a sensory level stimulus when experienced for a long period of time (aka accommodation)

preventing tolerance is critical for

full effectiveness

adaptation is minimized by

modulating current

- pulse/phase duration

- pulse/phase amplitude

- frequency

- combined (duration and amplitude)

interferential current is what type of current

specific type of current used primary for pain modulation

interferential current requires

a special machine that delivers IF current

Interferential Current

interference of currents (AC) from 2 channels each with different carrier frequencies

the carrier frequencies for IF current are usually

different by approx 100 Hz

options for electrode placement

site of pain

anatomically or physiologically related site (dermatome, spinal nerve)

other remote sites

must activate large diameter afferents

goal for current flow

to get current field to pass through affected deep tissues

if not getting the response you want change

- electrode placement

- electrode configuration

contraindications for TENS

- other electronic devices

- low back or abdomen of pregnant women

- regions of known or suspected malignancy

- recent radiated tissue

- near/over eyes

- anterior neck

- damaged skin

precautions for TENS

- sensory impairments

- chest wall

- active epiphysis

- cog/communication impairments

- regenerating nerves

when assessing outcome of TENS treatment what do we look for

pain

skin

did it help? did it make things easier?

when documenting use of TENS

mode of TENS

waveform type

waveform parameters

if IF current

level of stimulation intensity (mA)

electrode (type, shape, size, and #, placement/location)

integrity of skin before and after

patient position

treatment duration

What is the configuration of channels used in sensory-level TENS for knee OA?

Two channels with electric fields criss-crossing the joint.

What should be avoided during sensory-level TENS for knee OA?

Contractions of the quadriceps and anterior compartment muscles.

Sensory or noxious TENS: subacromial pain

- electrodes placed just anterior and posterior to acromion

- promotes deeper penetration of current than anterior placement of electrodes

- will get some muscle activation - even at 3 times sensory threshold

goal for sensory or noxious TENS subacromial pain

to provide analgesia to subarcomial bursa to supraspinatus

motor level stimulation is usually used for what type of pain

non-acute pain (low irritability)

possible mechanisms for analgesia with motor level stimulation

- blocks signal peripherally from going to brain

- endogenous opioid mechanism

- increased blood flow to area of injury

chronic active trigger point: levator scapula/upper trapezius

stimulation will cause some head/neck rotation

can also place electrode over posterior cervical musculature

2 pps, 400 microsecs. 1 min on/1 min off, 10 min duration

when doing noxious TENS where should we place elctrode?

tendon, ligament, fat pad pain - should be a palpable structure

noxious level stimulation uses perception of pain to

inhibit pain

parameters the elicit noxious response

long pulse duration and high amplitude