AASM Scoring of Sleep Stages and Arousals Flashcards
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According to AASM guidelines, an epoch is scored as Stage N2 sleep upon the first occurrence of which of the following?
Answer: A K-complex or a sleep spindle.
Stage N2 sleep is defined by the presence of either a K-complex or a sleep spindle. The appearance of one of these events marks the transition from Stage N1 to Stage N2, even if the rest of the epoch resembles Stage N1.
To score a 30-second epoch as Stage N3, what percentage of the epoch must contain slow wave activity?
Answer: 20% or more
The AASM manual defines Stage N3 (slow-wave sleep) as any epoch in which 20% or more of the epoch consists of slow wave activity. This is defined as waves with a frequency of 0.5-2 Hz and a peak-to-peak amplitude of >75 µV, measured over the frontal regions.
Which combination of features is required to score an epoch as Stage R (REM) sleep?
Answer: Low-amplitude mixed-frequency EEG, low chin EMG, and rapid eye movements.
Stage R is characterized by a unique combination of physiological signals. These include a relatively low-amplitude, mixed-frequency EEG pattern, a low chin EMG tone (atonia), and the presence of rapid eye movements (REMs).
What is the minimum duration for an abrupt shift in EEG frequency to be scored as an arousal during NREM sleep?
Answer: 3 seconds
An arousal is defined as an abrupt shift in EEG frequency (to alpha, theta, and/or frequencies >16 Hz) that lasts for at least 3 seconds. It must also be preceded by at least 10 continuous seconds of sleep.
When scoring an arousal during Stage R sleep, what additional criterion must be met besides the 3-second EEG frequency shift?
Answer: A concurrent increase in submental EMG for at least 1 second.
Scoring an arousal during REM sleep has a stricter requirement than in NREM. In addition to the abrupt 3-second EEG frequency shift, there must be a concurrent increase in the submental (chin) EMG lasting for at least 1 second.
A 30-second epoch contains a single sleep spindle but is otherwise composed of low-amplitude, mixed-frequency activity consistent with Stage N1. How should this epoch be scored?
Answer: Stage N2
The presence of a single K-complex or sleep spindle is sufficient to define an epoch as Stage N2. Even if the rest of the epoch appears to be Stage N1, the defining feature of N2 takes precedence.