[Changes in sleep architecture by resumption of CPAP in patients with sleep apnea syndrome]

It is known that application of continuous positive airway pressure (CPAP) improves sleep architecture in patients with sleep apnea syndrome (SAS). In contrast, there have been only a few studies which deal with deterioration of sleep architecture by discontinuation of CPAP. In the present study we analyzed changes of sleep architecture by temporary removal of CPAP. The subjects were 41 patients who underwent polysomnography (PSG) for diagnosis of SAS. The patients chose either a 1-night study in which only PSG was done, or a 2-night study in which, after treatment with CPAP for one month, PSGs with and without CPAP at night were done. The mean ages, heights, and weights between the 1-night group and the 2-night group were not statistically different The mean AHI of the 1-night group (38.9 +/- 5.0/hr; mean +/- SE) and that of the 2-night group (45.7 +/- 5.4/hr) were not significantly different. The mean AHI profoundly decreased (4.4 +/- 0.9) by CPAP therapy on the second night. Percents of each sleep stage in the 1-night group were as follows; stage 1, 31.8%; stage 2, 50.0%; stage (3 + 4), 2.8%: REM, 15.7%. In the 2-night group, stage 1 was 43.6%, significantly higher than that in the 1-night group, while stage 2 was 39.9%, which was significantly smaller. There were no significant difference in stage (3 + 4) and REM. When CPAP was again applied to the 2-night patients, stage 1 significantly decreased to 15.5%, while stage 2 (55.6%), stage (3 + 4) 6.7%, and REM (22.3%) increased significantly. Therefore, cessation of CPAP shifts the sleep stage from stage 2 to stage 1. Since stages 1 and 2 occupy approximately 80% of total sleep duration, the shift may have some physiological significance. Resumation of CPAP may have improved quality of life and day-time sleepiness by decreasing stage 1 sleep and increasing stages of deeper sleep and REM.