EEG evaluation of a sleep recorder.

Abstract

Sleep disorders are important diagnostic and therapeutic aspects of many common psychiatric syndromes. Clinicians have to be content with the patients' own assessment of their sleep patterns, or at the best, those of a night nurse; both methods are known to be unreliable, particularly where insomnia is present (Kuper et al., 1970). In a previous paper, Johnson and Kitching (1972) described a simple device for assessing the duration of sleep in ward situations. It depended upon the patient's ability to signal wakefulness by pressing a mechanical switch in response to an intermittent light stimulus throughout the night. This was considered to indicate a level of cerebral arousal compatible with wakefulness: failure to respond to the light stimulus indicated that the patient's level of cerebral arousal was lowered to the level of ‘sleep‘. A number of objections were anticipated, however, which might invalidate these assumptions. Most important of these were: (i)The intermittent occurrence of the light stimulus, every 15–20 minutes, limits the device to an approximation of the duration of sleep. The system of scoring was to assume a period of 10 minutes of sleep on either side of a missed stimulus.(ii)The possibility that the patient could press the mechanical switch in response to the light stimulus whilst in Stage I or even Stage II of sleep (Rechtschaffen et al., 1968) without returning to wakefulness.(iii)The intermittent light stimulus might itself act as a disruptive stimulus to sleep, producing arousal and thus altering the sleep level.