E stim types

NMES goals

◦ Atrophy treatment/prevention
◦ Strengthening
◦ Achieve synchronous firing/ recruitment of motor units

what are NMES typical settings

PC burst modulated waveforms

Voluntary (no e-stim)

◦ Smaller → larger motor units
◦ # of motor units can be altered during voluntary contractions

“Artificial” contractions stimulated by NMES

◦ More random recruitment, large and small together
◦ Cannot alter # of motor units recruited

Most common form of NMES

Russian

burst modulation (russian)

Variation of alternating current that is interrupted and delivered in short bursts (AKA medium frequency burst alternating current)

is russian bipolar or monopolar

bipolar electrode placement

NMES pulse width/duration

200-800 nsec

NMES pulse frequency

30-100 pps

NMES on:off time

10 sec on : 50 sec off common for >10 reps

◦ The shorter the off time and the longer the on time = greater chance for fatigue
◦ The longer the on time = a decrease in force output over time
◦ 1:5 ON:OFF typically

NMES ramp

1-5 sec up/down

NMES amplitude

max contraction/tolerance

◦ Force output is found to decrease if current amplitude is not increased both in and between treatments
◦ To decrease the chance of adaptation and optimize strengthening with ES current amplitude should be increased as often and as much as tolerated

NMES electrode configuration

◦ Aligning two electrodes parallel to the direction of the m. fibers produces greater force than a transverse configuration
◦ Using large electrodes for one, or two channel setup is beneficial with large m. groups

functional electrical stimulation (FES)

• A type of NMES in which the electrical stimulation is utilized as an alternative or supplement to orthotic devices or braces

• peripheral n has to be intact

• shoulder subluxation & foot drop

interferential current (IFC) goals

• Most commonly used for pain modulation
◦ Can also be used for production of muscle contraction and reduction of edema

what is IFC characterized by?

crossing of two sinusoidal waves that interfere with one another to generate an amplitude-modulated beat frequency

Constructive interference

when the two waves are in phase, the sum of the superimposed wave is large

Destructive interference:

sum of the two waves is zero when the waves are
180 degrees out of phase

Beat frequency (amplitude-modulated)

resultant frequency produced by the two frequencies going into and out of phase

what is IFC setup?

quadripolar

Effects of IFC Treatment

•Sensory nerve fibers receive a lower amplitude stimulation than the area of tissue affected by the vector, thus IFC is said to be more comfortable than equal amplitudes delivered by conventional means.
•Medium frequency allows it to get through the skin with less resistance but once the interference begins it mimics low frequency effects

Conventional (High Rate) Transcutaneous Electrical Stimulation (TENS)

•Pain modulation through activation of central inhibition of pain transmission (gate control theory)
•Large diameter A-beta fibers activate inhibitory interneurons located in the dorsal horn of the spinal cord, producing inhibition of smaller A- delta and C-fibers (pain fibers)
•Presynaptic inhibition of the T-cells close the “gate” and modulates pain. Gating mechanism also includes release of enkephalins which combine with opiate receptors to depress the release of substance P from the A-delta and C-fibers

high rate TENS wave form

typically asymmetrical biphasic

high rate TENS current

continuous, pulsatile, burst

high rate TENS amplitude

comfortable tingling sensation; no muscle response

high rate TENS pulse rate

50-80 pps

high rate TENS pulse duration

50-100 nsec

high rate TENS duration of tx

10 mins - several hours

high rate TENS pain relief

onset: relatively fast

duration: temporary

Acupuncture-like (low rate) TENS

•Pain modulation through descending pathways generating endogenous opiates
• Noxious stimuli generate endorphin production from pituitary gland and other CNS areas
• Endogenous opiate-rich nuclei, periaqueductal gray matter (PAG) in midbrain and thalmus are also activated by noxious stimulus leading to presynaptic inhibition of the release of substance P from the A-delta and C-fibers

when can high rate TENS be applied?

acute & chronic phase of pain

when can low rate TENS be applied?

chronic phase of pain. Analgesia produced through stimulation-evoked production of endogenous opiates

low rate TENS wave form

typically asymmetrical biphasic

low rate TENS current

continuous, pulsatile, or burst

low rate TENS amplitude

strong, but comfortable rhythmic muscle twitch

low rate TENS pulse rate

1-5pps

low rate TENS pulse duration

150-300 μsec

low rate TENS duration of tx

20-40 minutes

low rate TENS pain relief

onset: 20-40 mins

duration: long lasting > 1 hr

IFC pulse width/duration

200-400 nsec

IFC frequency

10-150 pps (typically 100-150 pps)

IFC duration

10-30 mins

IFC amplitude

strong but tolerable

brief intense TENS

Used to provide rapid-onset, short term pain relief during painful procedures (wound debridement, passive stretching, joint mobilizations)

Burst-mode TENS

Combines characteristics of both high and low rate TENS. Stimulation of endogenous opiates, but current is more tolerable to patient than low rate TENS

Hyperstimulation (point stimulation) TENS

noxiously stimulate trigger point or local area of pain such as tendonitis

what is often used to improve patient tolerance and limit adaptation

amplitude modulation

Modulation mode TENS

a method of modulating parameters of any of above TENS to prevent adaptation due to constant ES; alters frequency, intensity, or pulse durations by > 10%

Low-intensity DC (micro- current)

•Does not stimulate sensory/motor nerves
•Used for tissue repair, wound healing

High-Volt Pulsed Current (HVPC)

•Wave form: typically paired monophasic with instantaneous rise and exponential fall of current
•Used for tissue repair and wound healing primarily; can be used for pain

Wound healing concept

◦ Intact skin surface negative with respect to deeper epidermal layers
◦ Injury to skin develops positive potentials initially and negative potentials during healing process

wound healing type

monophasic

Direct Current and/or HVPC

When positive electrode (anode) placed over wound cells ions that are negatively charged they will be drawn toward the electrodes; cells and ions that are positively charged will be repelled; vice versa for cathode

Iontophoresis

• Application of a continuous direct current to transport medicinal agents through the skin or mucous membranes for therapeutic purposes; Need prescription to apply medication
• Like charges repel like charges
• Unlike charges attract unlike charges

Iontophoresis electrode placement

Which electrode positive (anode) or negative (cathode) placed over treatment area will depend on charge of medicinal agent being utilized (dexamethasone negative polarity)

Decrease muscle spasm

types of NMES just alter on/off time to achieve goal
◦ Muscle fatigue: tetanic contraction sustained for several minutes by continuous mode

Edema reduction

NMES: Muscle pump to increase lymph and venous flow
◦ Muscle pump: interrupted mode produces rhythmic contraction and relaxation of muscle to replicate muscle pump and improve circulation