Annotation files

Use the PhysioBank ATM (or any PhysioToolkit application) to read the annotation files included in the SHHS Polysomnography Database. The text strings associated with each annotation are described below.

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Hypnogram (.hypn) annotations

The text strings indicate the sleep stage for the following 30-second epoch, according to this scheme:

code	meaning
W	subject is awake
1	sleep stage 1
2	sleep stage 2
3	sleep stage 3
4	sleep stage 4
R	REM sleep

EEG arousal (.arou) annotations

The text strings contain the following information:

Event type (Arousal)
Duration in minutes, seconds, and tenths of seconds (m:ss.s)

Respiratory event (.resp) annotations

The text strings contain the following information:

Event type (Hyp: hypopnea; Ob.A: obstructive apnea; Cn.A: central apnea)
Duration in minutes, seconds, and tenths of seconds (m:ss.s)
Percent decrease in SaO2 associated with the event
Minimum SaO2 (percent) associated with the event

Oximeter artifact (.oart) annotations

The text strings contain the following information:

Event type (SaO2.Art)
Duration in minutes, seconds, and tenths of seconds (m:ss.s)

Composite (.comp) annotations

The composite annotation file for each record contains all of the annotations in the .hypn, .arou, .resp, and .oart annotation files. These can always be distinguished by the event type (or sleep stage, in the case of the .hypn annotations). In addition, the chan field of the annotations, which appears in the fifth column of rdann's output, indicates the source of each annotation, according to this scheme:

code	meaning
0	sleep stage (.hypn)
1	EEG arousal (.arou)
2	respiratory event (.resp)
3	oximeter artifact (.oart)

Return to the SHHS PSG Database