Electrophysiological recording of nocturnal sleep and the multiple sleep latency test in obstructive sleep apnea syndrome

Polysomnographic studies were performed in 6 patients with obstructive sleep apnoea syndrome (OSA). The sleep study consisted of: electroencephalography, electromyography, electrooculography, electrocardiography, pulse oximetry and observation of respiration. During day multiple sleep latency tests were performed. In all patients fragmentation of sleep with prevalent stages 1. and 2. of NREM and occasionally deep sleep and REM phase were observed. Concomitantly with the appearance of electrophysiologic sleep stages the muscle tone decreased and episodes of obstructive apnoea occurred. The periods of sleep and apnoea alternated with wakefulness and breathing. In MSLF the mean latency was 3 +/- 2 min. In OSA syndrome episodes of obstructive sleep apnoea cause sleep fragmentation and prevalence of light sleep stages. Excessive daytime somnolence observed in this syndrome is caused by sleep disturbances. MSLT demonstrated pathologic hypersomnolence in OSA syndrome.