Autoadjusted versus fixed CPAP for obstructive sleep apnoea: a multicentre, randomised equivalence trial.

Background The obstructive sleep apnoea syndrome (OSAS) is conventionally treated by continuous positive airway pressure set at a fixed level (fCPAP). Automatic mask pressure adjustment (autoCPAP) is increasingly used during home therapy. We investigated whether autoCPAP is equivalent to fCPAP in improving sleepiness in patients with OSAS in the long-term. Methods In this multicentre equivalence trial, 208 patients with OSAS, with median Epworth sleepiness score (ESS) 13, apnoea/hypopnoea index 48.4/hour, were randomised to treatment with autoCPAP (5-15 mbar) or fCPAP (pressure set at the 90th percentile applied by autoCPAP during 2-4 weeks adaptation). Coprimary outcomes were changes in subjective and objective sleepiness from baseline to 2 years after treatment. Equivalence ranges were 2 points in ESS and 3min sleep resistance time evaluated by recording responses to light signals. Results At 2 years, in the intention to treat analysis, the reduction in sleepiness versus pretreatment baseline was similar in patients using autoCPAP (n=113, mean ESS-change -6.3, 95%CI -7.1 to -5.5; sleep resistance time +8.3min, +6.9to +9.7) and fCPAP (n=95, mean ESS-change -6.2, 95%CI -7.0 to -5.3; sleep resistance time +6.3min, +4.7to +7.8). The 95%CI of difference in ESS-reduction between autoCPAP and fCPAP was -0.9 to +1.4 and the 95%CI of difference in increase in sleep resistance time was -2.6 to +1.0min. Blood pressure reduction and OSAS-related costs were similar between groups. Conclusions AutoCPAP and fCPAP are equivalent within prespecified ranges in improving subjective and objective sleepiness in patients with OSAS over the course of 2 years. Costs of these treatments are similar.