Special Testing & Calibration Procedures B

Question 1

When are amplifier calibrations performed? (AKA differential amplifier calibration)

Answer 1

At the beginning and at the end of a study

Question 2

What is the purpose of an amplifier calibration?

Answer 2

It assures that the signals from the amplifier to the recorder (polysomnograph) are valid.

Question 3

What does an amplifier calibration do?

How long should it last?

Answer 3

It assures polarity for each channel.

Should last at least 30 seconds.

Question 4

What does CMRR stand for?

What does it mean?

Answer 4

Common Mode Rejection Ratio

The machine is reducing unwanted signals and interferance..

Question 5

What’s another name for a low frequency filter (LFF)?

Answer 5

High pass filters. (It allows high frequencies to pass through while low frequencies are filtered out.)

Question 6

What is a time constant?

Answer 6

The time (in seconds) it takes for a waveform to drop to 37% of its calculated amplitude. (Remember 37%)

Question 7

What is the importance of a low time constant?

Answer 7

If there is a low time constant, low frequencies will be read. If you have a high time constant, then low frequencies won’t be read.

Question 8

What are high frequency filters (HFF) used for?

Answer 8

Used to attenuate muscle artifact in EEG channels.

Question 9

What is another word for a high frequency filter?

Answer 9

Low pass filters. (It allows low frequencies to pass through while high frequencies are filtered out.)

Question 10

What does it mean to adjust a time axis?

Answer 10

Adjust the vertical lines so they line up on the polysomnography reading
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Question 11

What does it mean to adjust the mechanical baseline>

Answer 11

Adjust the horizontal lines for each channel. Kind of like adjusting ECG baselines so that they're evenly spaced.
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Question 12

After physiological calibrations are completed, what should you do?

Answer 12

Instruct the patient to assume a comfortable sleeping position.

Question 13

How does a patient do physiologic calibration? (Steps 1-5)

Answer 13

1. Eyes open 30 seconds
2. Eyes closed 30 secibds
3. Look right and left 5 times
4. Look up and down 5 times
5. Eyes blink

Question 14

How does a patient do a physiologic calibration? (Steps 6-10)

Answer 14

6. Breath-hold, breathe through the nose, breathe through mouth 10 seconds
7. Breathe normally, check airflow and effort are synchronous (no time specified)
8. Move the right foot, move the left foot
9. Snore
10. Grind teeth for 5 seconds (C-24)