Instrumentation and Common Errors

Question 1

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

\_\_\_\_\_\_ amplitude
\_\_\_\_ peak latency
\_\_\_\_the negative spike duration
\_\_\_\_\_\_ a phase
and \_\_\_\_ total waveform duration

Answer 1

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

Question 2

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

_____ amplitude
______ onset and peak latency

Answer 2

decrease amplitude

prolong onset and peak latency

Question 3

sweep speeds that are too slow may ____

Answer 3

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

Question 4

name the equipment that comprises electrodiagnostics (5)

Answer 4

electrode
amplifier
microprocessor
stimulator
cathode ray tube (CRT)

Question 5

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

Answer 5

1kHz

Question 6

equation for voltage

Answer 6

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

V=IR

Question 7

equation for power

Answer 7

power = volts x amperage (current)

or P=VI or I^2 x R

Question 8

equation for work

Answer 8

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

Question 9

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

Answer 9

Inductance - measured in Henrys (L)

Question 10

____ measures the electric field that surrounds the conductor

Answer 10

capacitance (measured in Ferads)

Question 11

_____ 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

Answer 11

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

Question 12

_____ is cycles per second

Answer 12

frequency; 1 cycle per second is 1 Hz

Question 13

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

Answer 13

high pass, high, low

Question 14

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

Answer 14

low pass, low, high

Question 15

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

Answer 15

low 20Hz

High 2 kHz

Question 16

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

Answer 16

2 Hz

10 kHz

Question 17

what are the normal settings for EMG
Low freq
high freq

Answer 17

20 Hz

10 kHz

Question 18

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

Answer 18

500Hz

10Hz

Question 19

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

Answer 19

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

Question 20

reducing the high frequency filter on SNAP does what 4 things

Answer 20

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

Question 21

decreasing the low frequency filter on SNAP does what 4 things

Answer 21

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

Question 22

increasing high frequency filter on SNAP does what 4 thigns

Answer 22

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

Question 23

CMAP if you increase low frequency filter:

Answer 23

same as SNAP

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

Question 24

CMAP decreasing high frequency filter: (4)

Answer 24

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

Question 25

What should you do if you have simulus artifact? 4

Answer 25

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

Question 26

Monopolar needle measures ______ degrees reference where ?

Answer 26

360 over inert point

Question 27

Concentric measures _____ degrees reference where?

Answer 27

270 degrees - must spin electrode to get appropriate response "aiming periscope" Reference is in steel shaft

Question 28

If cathode and anode are reversed ____ and ____ are affected

Answer 28

prolongs distal latency | increases conduction velocity

Question 29

what is the formula for conduction velocity

Answer 29

distance/prox lat - distal latency

Question 30

if proximal stim cathode reversed, CV will _____

Answer 30

decrease

Question 31

If cold, ______ stays open longer and ______ is less. wave form gets _____. Amplitude _____ Latency _____ CV ______ _____ per degree

Answer 31

Na channels inactivation larger increases decreases decreases 2-4 m/sec per degree slowing

Question 32

if you increase the gain _______

Answer 32

smaller differences become larger decreased onset latency no change in amplitude

Question 33

Must have the same _____ for prox and distal stimulation

Answer 33

gains

Question 34

if you get a positive deflection during stimulation, you _______ If persistent + deflection, ______

Answer 34

not over motor point measure where leaves baseline.

Question 35

Velocity =

Answer 35

distance/time.

Question 36

there are 4cm between active and reference electrodes. If less, will get a _____ shift. ____ peak latency _____ onset latency ______ amplictude ______ duration

Answer 36

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

Question 37

constant voltage stimulation is inconsistent due to ____

Answer 37

skin resistance

Question 38

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

Answer 38

more, same stimulation

Question 39

latency and amplitude: SNAP: CMAP:

Answer 39

snap: latency to peak onset, amplitude peak to peak CMAP onset latency when leaves the baseline. Amplitude is baseline to peak

Question 40

CmAP studies must subtract out distal stim point to extrude ______

Answer 40

NMJ elements

Question 41

which needle? increased amplitudes no change in duration in most studies more phases

Answer 41

monopolar

Question 42

Turn the machine on first then _____

Answer 42

hook up the patient

Question 43

Nevere have ____ on the patient

Answer 43

2 grounds

Question 44

Plug all components into ____

Answer 44

the same electrical bed

Question 45

Absolute contraindication:

Answer 45

external pacemaker, no LVAds central and deep lines okay just use opposite limb

Question 46

do not use extension cords due to ______

Answer 46

leakage of current

Question 47

Use ____ table

Answer 47

wooden exam table

Question 48

Can do study if on anticoagulation but avoiding ____ and ____ absolute contraindication if inr is > ____

Answer 48

deep muscles to avoid compartment syndrome and paraspinals/multifidi 3.5

Question 49

Do not place needle through ____

Answer 49

active cellulitis or a nerve

Question 50

PTX "at risk muscles" | 4

Answer 50

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

Question 51

lymphedema is a _____ contraindication to EMG

Answer 51

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.