Sleep Study Technical Setup & Electrode Application Flashcards

During PSG electrode application, an impedance check shows 18 kΩ on the C4-M1 EEG derivation. What is the correct action before starting the study?

Answer: Re-prep the scalp site and reapply the electrode to achieve impedance below 5 kΩ

AASM guidelines specify that electrode impedance should be ≤ 5 kΩ (ideally ≤ 2 kΩ) for all EEG electrodes. High impedance (18 kΩ) dramatically increases susceptibility to 60 Hz electrical artifact and degrades signal quality. The site must be re-prepped (lightly abraded and cleaned) and the electrode reapplied before the study proceeds.

According to AASM recommendations for adult PSG, which EEG derivations should be used as the primary channels for sleep staging?

Answer: F4-M1, C4-M1, O2-M1 (right hemisphere derivations as primary)

AASM (2007 and updated rules) recommends F4-M1, C4-M1, and O2-M1 as the primary EEG derivations for sleep staging, with F3-M2, C3-M2, and O1-M2 as backup channels. The right hemisphere is primary because the reference electrode M1 (left mastoid) is farther from the heart, reducing ECG artifact contamination in frontal leads.

During pre-study biocalibrations, the technologist asks the patient to look left and then right several times. Which recording channel is this instruction designed to verify?

Answer: EOG (electrooculography) channels

Horizontal eye movements produce large, out-of-phase deflections in the EOG channels (E1-M2 and E2-M1). Asking the patient to look side-to-side confirms that both EOG electrodes are properly placed and recording, and that the polarity (phase reversal) is correct. This is critical for distinguishing eye movements during REM and wake.

What is the primary clinical purpose of the submental (chin) EMG channel in a standard PSG montage?

Answer: To distinguish REM sleep (atonia) from NREM sleep (normal muscle tone)

The submental EMG is essential for sleep staging because REM sleep is defined in part by muscle atonia (very low chin EMG amplitude). AASM requires that REM be scored only when the chin EMG falls to its lowest level of the recording. Elevated chin EMG during suspected REM may indicate REM sleep behavior disorder.

In the standard PSG setup, leg EMG electrodes are placed on the anterior tibialis muscles of both legs. What minimum inter-electrode distance is recommended to ensure proper recording?

Answer: 2-3 cm apart on the anterior tibialis, one-third of the way down the lower leg

AASM recommends placing leg EMG electrodes 2-3 cm apart longitudinally on the belly of the anterior tibialis muscle, approximately one-third of the way down from the knee. This placement optimally captures tibialis muscle bursts associated with periodic limb movements, while minimizing cross-talk from adjacent muscles.

The standard PSG epoch length used for manual sleep staging according to AASM rules is:

Answer: 30 seconds

AASM scoring rules specify a standard epoch length of 30 seconds for sleep staging. Each epoch receives exactly one sleep stage designation (W, N1, N2, N3, or R). Thirty seconds was chosen to align with the traditional paper PSG speed of 10 mm/sec (which yields a 30-cm/page recording at that speed).