All patients with suspected obstructive sleep apnea presenting at the Auckland Hospital Sleep Laboratory and referred for either a split-night or full night diagnostic study, will be offered participation in the study and will be recruited. From these patients, a total of 20 patients that are diagnosed with clinical obstructive sleep apnea syndrome, based on diagnostic polysomnography, will undergo titration with the HC254 Auto CPAP. An additional 20 patients will undergo titration with the HC244 CPAP.