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<center><h2>Annotation files</h2></center>
<p>
Use the <a href="/cgi-bin/ATM?database=shhpsgdb">PhysioBank ATM</a> (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.
<p>
<a href="./">Return to the SHHS PSG Database</a>
<h2>Hypnogram (.hypn) annotations</h2>
<p>
The text strings indicate the sleep stage for the <em>following</em> 30-second
epoch, according to this scheme:
<center><table>
<tr><th align=center width=20%>code</th><th align=left>meaning</th></tr>
<tr><td align=center>W</td><td>subject is awake</td></tr>
<tr><td align=center>1</td><td>sleep stage 1</td></tr>
<tr><td align=center>2</td><td>sleep stage 2</td></tr>
<tr><td align=center>3</td><td>sleep stage 3</td></tr>
<tr><td align=center>4</td><td>sleep stage 4</td></tr>
<tr><td align=center>R</td><td>REM sleep</td></tr>
</table></center>
<h2>EEG arousal (.arou) annotations</h2>
<p>
The text strings contain the following information:
<ul>
<li> Event type (Arousal)
<li> Duration in minutes, seconds, and tenths of seconds (m:ss.s)
</ul>
<h2>Respiratory event (.resp) annotations</h2>
<p>
The text strings contain the following information:
<ul>
<li> Event type (Hyp: hypopnea; Ob.A: obstructive apnea; Cn.A: central apnea)
<li> Duration in minutes, seconds, and tenths of seconds (m:ss.s)
<li> Percent decrease in SaO2 associated with the event
<li> Minimum SaO2 (percent) associated with the event
</ul>
<h2>Oximeter artifact (.oart) annotations</h2>
<p>
The text strings contain the following information:
<ul>
<li> Event type (SaO2.Art)
<li> Duration in minutes, seconds, and tenths of seconds (m:ss.s)
</ul>
<h2>Composite (.comp) annotations</h2>
<p>
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 <tt>chan</tt>
field of the annotations, which appears in the fifth column of
<tt>rdann</tt>'s output, indicates the source of each annotation,
according to this scheme:
<center><table>
<tr><th align=center width=20%>code</th><th align=left>meaning</th></tr>
<tr><td align=center>0</td><td>sleep stage (.hypn)</td></tr>
<tr><td align=center>1</td><td>EEG arousal (.arou)</td></tr>
<tr><td align=center>2</td><td>respiratory event (.resp)</td></tr>
<tr><td align=center>3</td><td>oximeter artifact (.oart)</td></tr>
</table></center>
<p>
<a href="./">Return to the SHHS PSG Database</a>
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