The SensAwake™ modification to the Fisher and Paykel automatically titrating positive airway pressure (APAP) device aims to sense whether the patient is awake via respiratory patterns that differentiate between sleep and wake. Upon sensing that the patient is awake the device is able to reduce positive airway pressure PAP aiming to improve patient comfort which should result in more consolidated sleep. This study will investigate Obstructive Sleep Apnea (OSA) and a automatically Adjusting Positive Airway Pressure (APAP) device with new technology called SensAwake™. This requires experimental confirmation in a randomised controlled trial. Double-blind randomised crossover trial comparing WASO on standard APAP with WASO using APAP modified by the addition of the SensAwake™ modification on consecutive nights in participants with moderate-to-severe OSA.

A total number of 45 participants will be recruited from an OSA population, aged 18-65. Participants will consist of male and female patients diagnosed with moderate-severe OSA (Apnea Hypopnea Index (AHI) greater than or equal to 15 per hour. Eligible participants, according to the protocol approved by the HREC, providing written informed consent will be enrolled into the study. Patients will be enrolled sequentially according to the randomisation list. Patients will be randomised to APAP or APAP with the addition of the SensAwake™ modification. The investigator and study staff will be blinded to the treatment of any participant.

Inclusion Criteria:

• Aged 18-65 years with moderate-to-severe OSA (Apnea Hypopnea index equal to or greater than 15 per hour).
• Epworth Sleepiness Scale (ESS) scores 0-15 inclusive (normal to moderately severe daytime sleepiness).
• Fluency in both written and spoken English.
• Do not have unstable psychiatric disease.
• No other significant sleep disorder.

Exclusion Criteria:

• Participants prescribed and fitted with any PAP device in the past 2 years.
• Unstable cardiovascular disease (untreated or resistant hypertension acceptable).
• Inability to tolerate CPAP due to nasal obstruction or claustrophobia as determined by the study investigator.
• Any known factor or disease that might interfere with treatment compliance, study conduct or interpretation of the results such as psychiatric disease, history of non compliance to medical regimens, or unwillingness to comply with study requirements.
• Participation in another clinical trial in the previous month.