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EMG > Instrumentation and Common Errors > Flashcards

Instrumentation and Common Errors Flashcards

1
Q

A low frequency filter with too high of frequency limit may:

______ amplitude
____ peak latency
____the negative spike duration
______ a phase
and ____ total waveform duration

A

decrease amplitude
shorten peak latency
decrease the negative spike duration
add a phase
increase total waveform duration

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2
Q

A high frequency filter with too low a cut-off may:

_____ amplitude
______ onset and peak latency

A

decrease amplitude
prolong onset and peak latency

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3
Q

sweep speeds that are too slow may ____

A

omit phases, turns, or entire potentials when using digital equipment

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4
Q

name the equipment that comprises electrodiagnostics (5)

A

electrode
amplifier
microprocessor
stimulator
cathode ray tube (CRT)

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5
Q

when an event happens 1000 times in a second it has a frequency of ______

A

1kHz

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6
Q

equation for voltage

A

voltage (Volts) = current (amperes) x resistance (Ohms)

V=IR

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7
Q

equation for power

A

power = volts x amperage (current)

or P=VI or I^2 x R

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8
Q

equation for work

A

work/energy (E) = P x T or I^2 x R x t

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9
Q

____ measures energy stored in magnetic field set up by a conductor

A

Inductance - measured in Henrys (L)

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10
Q

____ measures the electric field that surrounds the conductor

A

capacitance (measured in Ferads)

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11
Q

_____ refers to the effects of resistance, capacitance, and inductance, not just the resistance. So it takes into account the associated magnetic field of the process, unlike resistance

A

impedance - there is a meter on the EMG machine to tell you how much leakage is in the system; twice a year someone should check to make sure there is no leakage in the system

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12
Q

_____ is cycles per second

A

frequency; 1 cycle per second is 1 Hz

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13
Q

a low filter (___ pass) allows the _____ frequencies to go through, and filters out the _____ fequencies

A

high pass, high, low

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14
Q

a high frequency filter (_____ pass) allows the ____ frequencies to go through and filters out the _____ frequencies

A

low pass, low, high

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15
Q

What are the normal settings for sensory NCS
Low freq
High freq

A

low 20Hz
High 2 kHz

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16
Q

what are the normal settings for motor NCS
Low freq
High freq

A

2 Hz
10 kHz

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17
Q

what are the normal settings for EMG
Low freq
high freq

A

20 Hz
10 kHz

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18
Q

what are the normal settings for single fiber EMG
low freq
high freq

A

500Hz
10Hz

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19
Q

elevating the low frequency filter on SNAP does what 4 things?

A

shortens peak latency
reduces the amplitude
changes potentials from bi-to tri-phasic
does not change onset latency

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20
Q

reducing the high frequency filter on SNAP does what 4 things

A

prolongs peak latency
reduces amplitudes
creates longer negative spike
prolongs onset latency

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21
Q

decreasing the low frequency filter on SNAP does what 4 things

A

onset latency - no change
peak latency - increases
negative spike duration - increases
amplitude - increases

22
Q

increasing high frequency filter on SNAP does what 4 thigns

A

onset latency - shortens
peak latency - decreases
negative spike duration
amplitude - increases

23
Q

CMAP if you increase low frequency filter:

A

same as SNAP

shortens peak latency
reduces the amplitude
changes potentials from bi-to tri-phasic
does not change onset latency

24
Q

CMAP decreasing high frequency filter: (4)

A

less change in amplitude
prolonged onset latency
prolonged peak latency - rightward shift

not nearly as effective (as sensory nerve study) b/c motor studies have more low frequency wave forms, so fewer are eliminated

25
Q

What should you do if you have simulus artifact? 4

A
  1. decrease skin impedence - remove lotions
  2. decrease resistance of the skin - pumous stone on callus
  3. make sure ground is between stim and pickup
  4. rotate the anode - changes isoelectric potential lines
26
Q

Monopolar needle measures ______ degrees

reference where ?

A

360

over inert point

27
Q

Concentric measures _____ degrees

reference where?

A

270 degrees - must spin electrode to get appropriate response “aiming periscope”

Reference is in steel shaft

28
Q

If cathode and anode are reversed ____ and ____ are affected

A

prolongs distal latency
increases conduction velocity

29
Q

what is the formula for conduction velocity

A

distance/prox lat - distal latency

30
Q

if proximal stim cathode reversed, CV will _____

A

decrease

31
Q

If cold, ______ stays open longer and ______ is less.

wave form gets _____.

Amplitude _____
Latency _____
CV ______

_____ per degree

A

Na channels

inactivation

larger

increases
decreases
decreases

2-4 m/sec per degree slowing

32
Q

if you increase the gain _______

A

smaller differences become larger
decreased onset latency
no change in amplitude

33
Q

Must have the same _____ for prox and distal stimulation

A

gains

34
Q

if you get a positive deflection during stimulation, you _______

If persistent + deflection, ______

A

not over motor point

measure where leaves baseline.

35
Q

Velocity =

A

distance/time.

36
Q

there are 4cm between active and reference electrodes. If less, will get a _____ shift.

____ peak latency
_____ onset latency
______ amplictude
______ duration

A

left
decreased peak latency
no effect on onset latency
decreased amplitude
increased duration

37
Q

constant voltage stimulation is inconsistent due to ____

A

skin resistance

38
Q

Constant current is _____ consistent and will get _____ irrespective of skin resistence

A

more, same stimulation

39
Q

latency and amplitude:

SNAP:

CMAP:

A

snap: latency to peak onset, amplitude peak to peak

CMAP onset latency when leaves the baseline. Amplitude is baseline to peak

40
Q

CmAP studies must subtract out distal stim point to extrude ______

A

NMJ elements

41
Q

which needle?

increased amplitudes
no change in duration in most studies
more phases

A

monopolar

42
Q

Turn the machine on first then _____

A

hook up the patient

43
Q

Nevere have ____ on the patient

A

2 grounds

44
Q

Plug all components into ____

A

the same electrical bed

45
Q

Absolute contraindication:

A

external pacemaker, no LVAds

central and deep lines okay just use opposite limb

46
Q

do not use extension cords due to ______

A

leakage of current

47
Q

Use ____ table

A

wooden exam table

48
Q

Can do study if on anticoagulation but avoiding ____ and ____

absolute contraindication if inr is > ____

A

deep muscles to avoid compartment syndrome and paraspinals/multifidi

3.5

49
Q

Do not place needle through ____

A

active cellulitis

or a nerve

50
Q

PTX “at risk muscles”
(4)

A

C&T paraspinals - no perpendicular - aim for lamina
Supraspinatus aim towards scapula, not perpendicular
Serratus anterior - aim for rib if not palpable
rhoboids - dont do study

51
Q

lymphedema is a _____ contraindication to EMG

A

relative - dont do it if the risk seems to be too much or if theyre having a lot of swelling. If it will change the treatment then its okay.

EMG (18 decks)

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