Sleep reactivity during acute nasal CPAP in obstructive sleep apnea syndrome

Objective: To measure the readjustments of sleep macro- and microstructure in patients with obstructive sleep apnea syndrome (OSAS) after acute nasal continuous positive airway pressure (NCPAP) treatment. Background: The conv entional polysomnographic analysis (macrostructure of sleep) does not neces sarily provide the best measures of sleep disruption associated with OSAS. In contrast, microstructural methods of analyzing sleep (i.e., arousals and cyclic alternating pattern) may improve evaluation of patients with OSAS. Method: Ten patients with OSAS were monitored polygraphically before and du ring the first night of NCPAP therapy. The results were compared with those of 10 age- and sex-matched controls without sleep-related breathing disord ers. Each nocturnal recording was followed by daytime observation using the multiple sleep latency test and Visual Analogue Scale (VAS). Results: The first night of ventilatory therapy was characterized by a remarkable expans ion of stages 3 and 4 and of REM sleep. In addition, NCPAP suppressed the p resence of cyclic alternating pattern (CAP) in REM sleep and induced an imp ressive rebound of arousals and of certain CAP variables-i.e., CAP rate, CA P time, number of CAP cycles-which dropped well below the physiologic value s expressed by controls. A normal duration of phases A and B was re-establi shed starting the first treatment night. When we matched sleep variables wi th the indices of daytime function, a significant correlation emerged only between the variations of CAP rate and VAS scores. In particular, improveme nt of daytime sleepiness was less evident when the ventilatory-induced drop of CAP rate was more pronounced. Conclusions: The application of CAP varia bles to the microstructural analysis of sleep may expand our knowledge rega rding sleep and respiration.