Second 50 Flashcards
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What is the best sensitivity setting for an EEG channel?
7 uV / mm or 70 uV/cm
Which montage usually includes a full EEG hookup in order to rule out the possibility of seizure activity?
REM behavior disorder
Which montage includes a pressure and airflow channel from a DC device?
CPAP
What percentage of the circumference of the head is T5 from T3?
10%
Where should the chin EMG electrodes be placed?
Above and below the chin
Which electrode site is not usually used in a baseline montage?
Arm EMG
G2 (exploring electrode) detects a voltage of -20 uV. The output voltage is 50 uV. What voltage did G1 (reference electrode) detect?
-70 uV (exploring electrode minus output voltage -20 -50 = -70)
Which muscle are the leg EMG electrodes placed on?
Anterior tibialis
G1 and G2 both equal -25 uV. What is the output voltage?
0 uV
Which electrode is located to the left of Cz?
C3
In standard placement for EOG electrodes, what happens when the pt looks up?
The channels move toward one another
If G1 (reference) is -80 uV, and the output voltage is 20 uV, what is the voltage of G2 (exploring)?
-100 uV ( -80 - -100) = -80 +100
Which electrode site is half the distance Fp2 to T4?
F8
What percentage of the vertical head measurement (nasion to inion) is Pz from the inion?
30%
Ear to ear measures 36 cm. What is the distance from the left ear to T3?
3.6 cm
The measurement from T6 to Pz is 8 cm. What is the distance from P4 to Pz?
4 cm
The measurement from F7 to F3 is 6 cm. What is the distance from F3 to Fz?
6.0 cm
What electrode site is located half the distance from O2 to C4 ?
P4
Which electrode site is located 10% above the inion?
Oz
A stress loop is helpful for which electrodes?
Leg EMGs
What is the likely cause of a high amplitude, low frequency artifact in the EEG?
Sweat artifact
What is verified during the time axis alignment check?
Vertical pen alignment
What is the best way to correct a 60 Hz artifact in the leg EMG?
Re-apply these electrodes
Electrical interference can be prevented if …?
The impedances of input electrodes are similar
What is acceptable current leakage in equipment?
Less than 100 uA for safety
Which sensor generates its own voltage and may be plugged directly into the headbox?
Thermocouple and Piezo-electric crystal band
A ground loop may occur when…?
The pt is attached to more than one diagnostic device, each with its own patient ground connection.
When should notch filters be used?
Only when absolutely necessary, never routinely
Electrical baseline refers to….?
The starting position for pen deflection when powered on, but no signal is detected by the amplifier, and also when the same signal is received by both inputs.
High and unequal electrode impedances will result in…?
60 Hz artifact
What causes electrode popping?
Loose electrodes or direct pressure against an electrode
If slow wave artifact is seen in three EEG channels with the same G1 (reference), an appropriate response is to…?
Re-reference the input to a backup electrode.
If a high frequency artifact appears in a single EEG channel, an appropriate response is to…?
Change the signal input to a backup exploring electrode (G2).
What may cause a strong EKG artifact in an EMG channel?
Poor electrode placement or high impedances
If a LOW frequency artifact appears in the EEG and EOG channels, what should be done?
Attempt to cool the pt and room (sweat artifact) and temporarily raise the low frequency filters to 1 Hz
Double referencing electrodes may be beneficial for which artifact?
EKG artifact in the EEG or eye channels
With artifact, changing the filters is…?
Only effective if underlying signals are intact and only as a last result when the artifact can’t be corrected
The preferred type of amplifier is…?
Differential
If G1 (reference) is more negative than G2 (exploring), the pen will…?
The pen will deflect upward (negative)
How far will the pen deflect if sensitivity is 10 uV/cm and the input voltage is 75 uV?
75 mm or 7.5 cm
What is the input voltage if the sensitivity is 5 uV/cm and the pen deflection is 10 cm?
50 uV
In most sleep systems which device is the patient head box directly plugged into?
AC amplifier
Which channel is DC?
SpO2
What is the primary difference between thermisters and thermocouples?
Thermocouples generate their own electricity (dissimilar metals) while thermisters do not.
Which device uses a cuff and bladder system?
Pneumatic respiratory transducer (in belt)
Common Mode Rejection Ratio (CMRR) refers to…?
The ability of an amplifier to eliminate unwanted signals
What device stores and releases energy in an alternating current circuit?
Capacitor
What is the max allowable leakage in diagnostic equipment?
100 uA
A frequency response curve is …?
A visual representation of the amplifier’s ability to eliminate frequencies outside the filter settings
The rise time is the time it takes the pen to reach what percentage of its deflection?
63%
The fall time is the amount of time for the pen to return to ___ of its baseline during amplifier calibrations
37%
The pen’s vertical position when the power is turned off is called the…?
Mechanical baseline
During amplifier calibrations, the display signals are…?
50 uV and -50 uV
