RPSGT Technology & Tools 3 — Questions and Answers
Question 1: What is the minimum recommended sampling rate for EEG signals in digital PSG according to AASM guidelines?
- 128 Hz
- 200 Hz
- 256 Hz (Correct answer)
- 500 Hz
Correct answer: 256 Hz
AASM recommends a minimum sampling rate of 256 Hz for EEG to adequately represent frequencies up to 35 Hz per Nyquist theorem.
Question 2: A nasal pressure transducer is preferred over a thermistor for detecting hypopneas because it:
- Is more resistant to condensation artifact
- Better detects flow limitation via waveform flattening (Correct answer)
- Has a faster thermal response time
- Requires no calibration before use
Correct answer: Better detects flow limitation via waveform flattening
Nasal pressure transducers detect the characteristic flow-limited flattened waveform that precedes and defines many hypopneas better than thermistors.
Question 3: Piezoelectric effort belts used in PSG measure respiratory effort by detecting:
- Changes in thoracic electrical impedance
- Mechanical strain causing voltage changes (Correct answer)
- Infrared light absorption by chest wall
- Pressure changes transmitted through the belt
Correct answer: Mechanical strain causing voltage changes
Piezoelectric belts generate a voltage proportional to mechanical strain (stretching/compression) from thoracoabdominal movement.
Question 4: During a split-night PSG, CPAP titration should begin when which criterion is met?
- AHI ≥ 5 events/hr in the first 30 minutes
- RDI ≥ 10 events/hr after at least 2 hours of diagnostic recording (Correct answer)
- At least 3 REM episodes documented on diagnostic portion
- SpO2 drops below 85% for more than 5 minutes
Correct answer: RDI ≥ 10 events/hr after at least 2 hours of diagnostic recording
AASM criteria require an RDI ≥ 10 events/hr after a minimum of 2 hours of diagnostic recording before initiating CPAP titration in a split-night study.
Question 5: Which CPAP device feature automatically adjusts pressure breath-by-breath based on detected flow limitation?
- BiPAP ST mode
- CPAP with C-Flex
- Auto-titrating CPAP (APAP) (Correct answer)
- Volume-assured pressure support (VAPS)
Correct answer: Auto-titrating CPAP (APAP)
APAP devices use algorithms analyzing flow signals to continuously adjust pressure in response to detected apneas, hypopneas, snoring, and flow limitation.
Question 6: A technologist notices the chin EMG signal is flat throughout the recording. The FIRST troubleshooting step should be:
- Replace the EMG electrodes and reapply
- Check electrode impedances at the chin site (Correct answer)
- Switch to a backup chin EMG channel if available
- Increase the amplifier sensitivity setting
Correct answer: Check electrode impedances at the chin site
Checking impedance first identifies whether the problem is poor electrode contact (high impedance) before making hardware changes.
Question 7: End-tidal CO2 (EtCO2) monitoring during PSG is MOST indicated for which patient population?
- Adults with suspected obstructive sleep apnea
- Pediatric patients and those with suspected hypoventilation (Correct answer)
- Patients with insomnia undergoing MSLT
- Patients on supplemental oxygen therapy
Correct answer: Pediatric patients and those with suspected hypoventilation
EtCO2 monitoring is particularly valuable in pediatric PSG and for detecting nocturnal hypoventilation in adults with obesity hypoventilation or neuromuscular disease.
RPSGT Technology & Tools 3
What is the minimum recommended sampling rate for EEG signals in digital PSG according to AASM guidelines?