EMG Bio feedback/NCV Flashcards
EMG biofeed back in general?
therapeutic use of instrumentation to detect feeback from MUAP by active muscle
signal is amplified and converted
used to increase or decrease muscle activity
Does it measure actual events occuring?
Measures the highly correlated events such as periperal skin temp, finger photo transmission, electromyography
What leads to change in ion concentration
increased perm to sodium and potassium
What is ion concentration measured in?
microvoltage by the device
Change in electrochemical gradient created by MUAP measured by?
electrodes
Which units are recruited first
smaller units recruited first then larger units with faster contractions may depress smalleru nits
EMG amplification reflects
number of active motor units size of motor units distance of active mm from electrode size of recording area interelectrode spacing
EMG and Force relationship
Isometric is linear
concentric/eccentric is nonlinear
3 kinds of electrodes?
2 active electrodes
1 ground electrode
How do we get to smoothened/integrated
2 active electrodes give off an amplified resultant signal that is subtracted from each other to get the amplified difference
Differential amplification removes extraneous noises
Common mode reflection ratio removes the common noise between the 2 electrode
Remaining noise is then filtered then amplified to get the raw activity (alternating) true electrical activity,
then rectified and integrated and smoothened
Purpose of EMG
to change the MUAP to audiovisual to increase or decrease mm activity
Advantages
immediate feedback/rewards that typically isn’t noted to allow for greater improvements
feedback without the constant supervision of the physical therapist
Indications
motor inhibition
motor recruitment
total body relaxation (generalized pain/stress) goal to decrease undesired muscle tension= muscle/stress relaxation
Contraindications
when mm contraction would make the condition worse
Safe and Effective application
consent
select appropriate muscle group with goal
alcohol the skin
place electrodes parallel to muscle fiber belly
place ground electrode on bony prominence
set gain/sensitivty threshold, goal on EMG unit
What can nerve conduction/EMG diagnose
peripheral nn lesion, mm injury, ongoing process of the neuromuscular system
establish correct diagnosis
localize lesion
determine treatment
info on prognosis
Hardware
EMG machine, monitor, amplifier, stimulator, needle electrode, recording electrode
Surface vs. Needle
Surface: disposable/nondisposable, ring or disc, all surface electrode
Needle: disposable, mono/bipolar concentric, active is needle, all other are surface
General consideration
replacing electrode
alcohol/clean skin
disposing of needles in sharps container
measuring site with tape
Precautions
morbidly obesed
thin individual
bleeding disorder
blood cautions
Contraindications
automatic cardiac defibrillator pacemaker metal lining soft tissue infection indwelling catheter
Variables
25 for room temp, 31 for UE, 29 for LE
Coldertemp: requires more current to get to AP, longer to go from rest to AP, sodium channels open slower=decreased NCV, remain open longer for increased AMP/Duration
Age and myelination
complete by age 5
mild decrease by 40
sig decrease by 70
UE vs LE nerves
UE: shorter latency, increased NCV, increased temperature, shorter nerves, thicker diameter
Wave form analysis
measures largest, fastest fibers
Evoked potentials from sensory nerve fibers. SNAP, orthodromic or antidromic
Evoked potentials from muscle. Compound motor action potentials. orthodromic
shape, area, rise time, duration, amp affected by axonal pathology, latency affected by demyelination, NCV affected by pathology
Insertional activity
brief electrical activity with insertion
crisp
healthy muscles don’t make a sound if needle stops moving
damages the muscle when inserted, test all 4 quadrants
normal muscles are crisp, 150ms
decreased insertional activity atrophied muscles, needle into the sand
increased insertional activity, muscle pathology, sharp positive waves that don’t last, >300ms
Examination of muscle at rest
abnormal spontaneous muscle activity
denervation, positive membrane caused by inc sodium
Positive sharp waves
dull thud, mm ap, recorded from mm with innervation impairment, positive deflections from basline 0.5 to 15Hz
Fibrillations
single muscle fibers firing autonomously
rain drops hitting roof of car
impair innervation
regular pattern
Complex Repetitive discharge
spontaneous activity
stim adjacent mm
motor boat misfiring
>6months neurogenic/myopathic condition
Myotomic discharge
prolonged fashioned AP
delayed relaxation
dive bombing waxing/waning
chronic radiculopathies/neuropathies
myotomic dystrophy
polymyelitis
Myokymic discharge
group of spontaneous motor potentials
continuous or discontinous
regular firing pattern/rhythm
Spontaneous end plate potential
if needle in the endplate of health muscle, painful and spontaneous activity, must reposition
Miniature endplate potential
short duration/amp, monophasic, spontaneous release of AcH
Endplate spike
short duration, int amp, depolarization from a single fiber
Motor unit amplitude
increases when reinnervated
represents fiber density
peak to peak
decreases when myopathic condition
Motor unit duration
increase with neuropathic
decreases with myopathic
initially from baseline
normal is 5-15ms
Motor unit phasic
phase is when it crosses baseline from negative to positive pole polyphasic >4 normal is <4 10-35% of normal muscle is polyphasic
Recruitment how to inc force
increase firing rate
increase units recruited
How to measure units/second
measure motor units repeated across the sweep
multiply by 10
yields the MUAP/1second
decreased recruitment
nerve trauma, neurogenic
increased firing rate and decreased recruitment
Early recruitment
myopathic, recruits large units early with minimal force produced
Pitfalls
bad subj/obj exam technical difficulties measuring error temperature anamolous innervation accessory peroneal nerve
