Compumedics Limited has developed an APAP device (Somnilink SPAP based on the new algorithm technology of characterising breaths and determination of inspiratory flow limitation. The objectives of this new technology are to enable accurate detection of inspiratory intervals for irregular breathing patterns that are likely to occur during REM sleep, sleep onset and wakefulness as well as to provide correct characterisation of inspiratory flow limitation. These features could translate in delivery of superior treatment because of improved sensitivity and specificity of respiratory event detection and earlier pressure response to inspiratory flow limitation. Demonstration of superiority of the Somnilink SPAP device relative to existing APAP treatment devices will be subject of future clinical trials (beyond the scope of this protocol). An early clinical trial of a pre-production version of Somnilink SPAP with the pressure control algorithm identical to the production version established non-inferiority for AHI relative to a reference APAP (Resmed Autoset Spirit) with the differential AHI estimate of -0.91 [-2.80; 0.91] (Mean [95%CI]). The Somnilink SPAP device is now available as a production version (CE and TGA approved) and the purpose of the current study is to establish its non-inferiority compared to an existing APAP device (Resmed Autoset S8).