Effects of fixed compared to automatic CPAP on sleep in Obstructive Sleep Apnoea Syndrome

Background: Automatic CPAP has been developed to improve CPAP efficiency and compliance. Continually matching the effective pressure may be associated to more frequent arousals that could disturb sleep. The aim of the present study was to compare sleep architecture after one month’s home therapy with CPAP or with an AutoCPAP device. Methods: Twenty OSAS patients (18 M / 2 F) after polysomnographic study with CPAP titration received either an automatic (AutoSet T, ResMed, Sydney, Australia) or a fixed level CPAP machine in a random, single blind fashion for one month. At the end of the home treatment period polysomnography was repeated while CPAP was administered by the same machine used at home. Results: There was no significant difference between groups in terms of age (50.0 vs 45.5, NS), sex, BMI (38.3 vs 35.1, NS), RDI (45.4 vs 48.0, NS), and CPAP effective level (9.8 vs 10.8, NS). After one month of therapy the correction of sleep respiratory disturbances and of sleep structure was satisfactory in both groups. No difference in any polysomnographic variable or in subjective sleepiness was found at re-evaluation. Conclusions: The results of this study demonstrate that on average CPAP administered by a fixed CPAP machine and by the AutoSet T autoCPAP device has similar effects in improving respiratory function during sleep, nocturnal sleep architecture, and subjective daytime sleepiness after a one-month therapy. As autoCPAP devices are more expensive than fixed CPAP machines, their prescription should be considered only after a clear demonstration of an increase in compliance to treatment by these devices.