BRPT Scoring Artifacts and Troubleshooting 2 — Questions and Answers
Question 1: Which artifact in EEG channels is identified by comparing it with the respiratory channels and finding that the EEG waveform cycles at exactly the breathing rate?
- Cardiac artifact
- Respiratory artifact (Correct answer)
- Movement artifact
- Reference electrode artifact
Correct answer: Respiratory artifact
Respiratory artifact causes slow rhythmic EEG waveforms that match the breathing frequency seen in respiratory effort or airflow channels.
Question 2: A completely flat (isoelectric) signal in a single EEG channel while all other channels show normal activity most likely indicates:
- The patient has entered very deep N3 sleep
- A disconnected lead, broken wire, or complete loss of electrode contact (Correct answer)
- Successful application of a high-pass filter
- Severe cerebral ischemia
Correct answer: A disconnected lead, broken wire, or complete loss of electrode contact
An isoelectric single channel with normal surrounding channels almost always represents a hardware fault — disconnected wire, broken lead, or electrode that has completely lost contact.
Question 3: The AASM recommended maximum electrode impedance for PSG recordings is:
- Less than 1 kΩ
- Less than 5 kΩ (Correct answer)
- Less than 10 kΩ
- Less than 25 kΩ
Correct answer: Less than 5 kΩ
AASM guidelines specify that electrode impedances should be below 5 kΩ to minimize signal distortion and artifact in PSG recordings.
Question 4: Eye movement artifacts can contaminate frontal EEG channels (F3, F4) because:
- EOG electrodes share amplifier circuits with EEG electrodes
- The corneoretinal potential of the eye acts as a voltage dipole whose field spreads to nearby electrodes (Correct answer)
- Eye movements generate 60 Hz interference
- Blinking causes mechanical movement of frontal scalp electrodes
Correct answer: The corneoretinal potential of the eye acts as a voltage dipole whose field spreads to nearby electrodes
The eye's corneoretinal potential (cornea positive, retina negative) creates a dipole; eye rotation changes the orientation of this dipole and induces voltage changes in nearby frontal EEG electrodes.
Question 5: Respiratory inductance plethysmography (RIP) belt artifact is most commonly caused by:
- High electrode impedance at the belt sensor
- Belt displacement or changed belt tension from patient repositioning (Correct answer)
- 60 Hz power line interference
- Cardiac pulsations transmitted to the chest wall
Correct answer: Belt displacement or changed belt tension from patient repositioning
RIP belts measure changes in cross-sectional area; repositioning shifts the belt or alters its tension, creating artifact that can mimic changes in respiratory effort.
Question 6: A pulse oximetry sensor showing poor signal quality with low-amplitude, irregular waveform is best corrected by:
- Increasing the oximeter's gain setting
- Repositioning the sensor or applying it to an alternate, better-perfused site (Correct answer)
- Applying a digital low-pass filter
- Increasing the sampling rate
Correct answer: Repositioning the sensor or applying it to an alternate, better-perfused site
Poor perfusion, nail polish, motion, or cold extremities reduce pulse oximetry signal quality; repositioning the probe or using an alternate site (earlobe, forehead) is the primary corrective action.
BRPT Scoring Artifacts and Troubleshooting 2
Which artifact in EEG channels is identified by comparing it with the respiratory channels and finding that the EEG waveform cycles at exactly the breathing rate?