Neuromuscular Electrical Stimulation Flashcards
Neuromuscular electrical stimulation (NMES)
Type of pulsed, alternating current used to stimulate a motor response by depolarizing intact peripheral nerves
Intact peripheral nerve and healthy muscle tissue is required for activation
Current flow parameters
Unipolar: Current flows in one direction
Bipolar: Current flows in two directions
Pulse frequency
Number of pulses per second (pps) or Hertz (Hz)
Recommended frequency range for NMES
30-75 Hz to facilitate increased firing rate and cause tetanic reaction
35 Hz for otherwise healthy patients
50 Hz to fatigue spastic muscles
Cycle frequency
Number of cycles completed per second (cps)
Pulse duration (pulse width)
Length of time electrical flow is on for one cycle to take place
Measured in microseconds
Determine which nerve fibers are preferentially recruited
Pulse width of 20-100 microseconds
Preferentially recruits sensory nerves
Large diamter A-beta nerve fibers that are hyper-stimulated to override pain
Pulse width of 200-400 microseconds
Preferntially recruits motor nerves
Recruits large diameter A-alpha motor nerves necessary for muscle contraction
Pulse width of 400-1000 miscroseconds
Preferentially recruits pain-carrying nerve fibers
Used in noxious electrotherapy protocols
Concept of pain relieving pain
Pulse amplitude
Strength of current measured in milliamps
Associated with the depth of penetration (deeper penetration will result in more muscle fiber recruitment)
Amplitude needs to be 25-50 milliamps to make a muscle contract
Pulse amplitude for cardiac arrest
75 milliamps
Peak amplitude
Maximum amount of voltage delivered in a single phase
Pulse charge
Number of electrons contained within a pulse
Pulse rise time
Time needed for pulse to reach its peak value for nerve depolarization
Pulse decay time
Time required or pulse to go from its peak back to zero
Pulse train
Individual patterns of waveforms, durations, and/or frequencies that are linked together and repeated at regular intervals
Amplitude ramp
Gradual rise or fall in the amplitude of a pulse train
2 second ramp up time is effective for non-spastic muscles
6-8 second ramp up time is helpful for mild to moderate spasticity
On/off cycle for strengthening
May require starting at 1:3 time ratio and progressing to 1:1 time ratio
On/off cycle for muscle reeducation
May require starting at a 1:3 time ratio and progress to 1:5 time ratio
Purposes of NMES
Improve muscle strength without increasing cardiovascular output
Enhancing range of motion
- Provides regular stretching over an extended period of time
Inhibit spasticity or muscle spasms
- Reciprocal stimulation of agonist and antagonist pairs can reduce spasticity
- Stimulate spastic agonist to fatigue
Strengthen muscles
- Increases muscle bulk
Improves capillary density in muscles
- Improves local blood supply
- Facilitates microcirculation
Improve endurance
Muscle reeducation or neuromuscular facilitation
- Ask patient to try and assist the action of the stimulator with voluntary movement
Reduce pain/temporarily correct shoulder spasticity/subluxation
- Can improve the resting position of joints
- Stimulation of posterior deltoid and supraspinatus as a substitute for traditional arm slings
- Modulate pain due to neurotransmitters and increase of endogenous opiates
Initiate orthotic substitution
Control edema
Enhance effect of botulinum toxin
- Botox can be more easily absorbed if muscles are active
Take up occurs over first two days after injection
Neuromuscular reeducation treatment protocol for NMES
Use goal-directed activity along with NMES to increase motivation, proprioceptive and kinesthetic feedback, and increase neural plasticity
Start with patient achieving tetanic muscle contraction
Progress to muscle fasciculation to cue patients to contract muscle
NMES Strengthening protocol
Increase amplitude to about half of individuals maximum isometric muscle contraction
NMES precautions
Use lowest effective current on patients with impaired mentation or sensation
Monitor motor response and skin
Areas of irritation, damage, or skin lesion can cause decreased tissue impedance and increased current tha tmay result in pain
Fractures
Pregnancy
Allergy or skin sensitivity
NMES contraindications
Lower back or uterus during first trimester of pregnacy
Metastases
Osteomyelitis
Thrombosis
Allergy to iontophoretically-derived medication
Patients who are taking diuretics
Should not be applied to craniofacial or cervical region of patient with history of CVA or seizures
Over phrenic nerve or bladder stimulators
Over carotid sinus
Near diathermy devices (minimum 9’ clearance)
Over or near superficial metal pins, plates, or hardware
Patients with cancer, infection, tuberculosis, or active hemorrhage
Cardiac pacemakers
