Evaluation of a computerised polysomnography system

Manual analysis of sleep, breathing, and oxygenation records is the "gold standard" for diagnosing sleep abnormalities but is time consuming and cumbersome. The accuracy and cost of a computerised sleep analysis system have therefore been investigated.

Manual and computerised (CNS Sleep Lab) scores from 43 consecutive clinical sleep studies were prospectively compared for accuracy and the time and costs were recorded.

There were good correlations and no systematic differences between manual and computer scoring for total sleep time, sleep onset latency, and duration of REM sleep. There was a small but clinically insignificant systematic difference in breathing pattern analysis, the number of hypopnoeas/hour being lower with manual than with computer scoring (13 (SE 3) v 15 (SE 3)/hour). There was no difference between computer and manual scoring of the frequency of apnoeas, so the frequency of apnoeas + hypopnoeas was clinically insignificantly higher with computer scoring with a highly significant correlation between the two techniques. The time taken to perform the analyses was not different between the two methods (manual 83 (SE 8) v computer 86 (SE 8) minutes). The computer system was six times more expensive than the manual system and annual running costs, including full maintenance contract and 15% depreciation, were twice as great.

The CNS Sleep Lab is sufficiently accurate for use in clinical sleep studies but is significantly more expensive and does not save technician time.