Foundational Sleep Technology Knowledge
Core concepts
CPSGT foundational knowledge centers on normal sleep and the signals used to describe it. Know the 30-second epoch and the standard stages: W, N1, N2, N3, and R. Wake typically shows alpha rhythm (8–13 Hz) over occipital regions when eyes are closed, with relatively high chin EMG. N1 is low-amplitude mixed-frequency EEG with theta (4–7 Hz), slow eye movements, and vertex sharp waves. N2 requires sleep spindles (usually 11–16 Hz) or K-complexes without an arousal. N3 requires slow-wave activity (0.5–2 Hz, >75 µV) occupying at least 20% of the epoch. REM requires low-amplitude mixed-frequency EEG, low chin EMG, and rapid eye movements, though REM can occur without eye movements within a REM period. Sleep architecture changes with age: children generally have more N3, while older adults often have less slow-wave sleep and more awakenings. Also understand circadian rhythm (an endogenous ~24-hour system entrained by light) and homeostatic sleep drive.
Traps
Questions often blur stage boundaries: alpha versus theta, N1 versus REM, and N2 versus N3. Do not score N3 for a few delta waves; apply the 20% rule. Do not call an epoch REM solely because EMG is low-look at EEG and eye-movement context. Arousals require an abrupt EEG frequency shift lasting at least 3 seconds. Distinguish central from obstructive apneas by effort, not by oxygen desaturation alone.
Worked example
An epoch contains 8 seconds of 1 Hz, 100 µV waves in a 30-second epoch. That is about 27% of the epoch, so it meets the slow-wave proportion for N3 if other features are consistent.
Rule of thumb
Stage by the defining feature that occupies the required proportion of the epoch; when features conflict, follow scoring rules rather than one channel.