Fixed-pressure CPAP versus auto-adjusting CPAP : Comparison of efficacy in obstructive sleep apnoea (OSAS) according to the individual level of efficient pressure and pressure variability.

Introduction : There are currently only little data available on the factors predicting the respective efficacy of fixed CPAP (FP-CPAP) or automated CPAP (APAP) for OSAS treatment. Aims and objectives : We evaluated the efficacy of a 3month-period treatment with FP-CPAP versus APAP on a composit criteria involving apnoea/ hyponoea index (AHI) and the Epworth score (ESS), according to the level of effective pressure (Peff) as well as pressure variability (Pvar). Methods : A multicenter prospective controlled study was conducted in 22 academic and non academic french centers. Initial clinical and polygraphic data were obtained before initiating a 7-day period using APAP delivering a variable pressure between 4 and 20 cm Hg. Then, patients were randomised to either FP-CPAP or APAP used during 3 months, and the data obtained at the end of the study period were analysed according to the inital level of Peff and Pvar. Results : 616 patients (mean age : 56.8 yrs ± 11.2, mean AHI : 51.7/h ± 20.8) were included. CPAP compliance was the same in both groups (FP-CPAP : 5.78h ± 1.9 vs APAP : 5.85h± 1.9) with an identical efficacy on AHI and the ESS (FP-CPAP : 6.11/h ± 7.94 and 6.02 ± 4.37, and APAP 5.71/h ± 6.75 and 6.05 ± 4.5). Despite the lack of influence of Pvar on FP-CPAP vs APAP efficiency, a greater initial pressure variability was associated with a significant higher residual AHI whatever the mode of CPAP applied. Conclusion : The efficiency of FP-CPAP and APAP was identical on OSAS improvement after 3 months of treatment, independently of initial level of effective pressure and variability.