This study will test the hypothesis that the modified positive airway pressure (PAP) device for OSA will be no worse than a market released product in terms of its treatment efficacy, comfort and patient compliance. Patients will have their treatment pressure titrated using polysomnography (PSG) in the sleep laboratory, and then in a random order will spend additional time undergoing PSG using both devices, and using both devices at home for 3 weeks. Data will be collected from the PSG studies, device downloads, independent pressure-flow loggers, and custom questionnaires.

The study will be held in two parts. The main portion of the study which compares the modified PAP device and the market released product including the laboratory testing and home testing of the devices will be called 'Part A'. Additional nights using the PAP device with PSG monitoring will be used to gather additional observational flow data to allow distortion testing and investigation of the FPH (Fisher & Paykel Healthcare) SensAwake (an unique feature which automatically lowers the pressure when a patient wakes up) algorithm while using PAP, this is part B.

Part A After the patient has undergone informed consent, their demographic and clinical variables will be collected and entered into a case report form (CRF) before any setup procedure is started. The patient will be asked to complete questionnaires regarding their normal therapy (ESS (Epworth Sleepiness Score), FOSQ (Functional Outcomes of Sleep Questionnaire), custom therapy comfort questionnaire), and then will be set up for a standard PSG. The patient will use their prescribed mask and a clean water chamber and breathing tube which will be connected to the modified PAP device. The patients will sleep on the device throughout the night while having their PAP titrated by a qualified sleep technician. Pressure titration is necessary for two reasons: firstly, it may have been a period of time since the participants last titration, and secondly this version of PAP involves the use of different levels of pressure. Pressures will be titrated according to the AASM (American Academy of Sleep Medicine) Clinical Guidelines for the Manual Titration of Positive Airway Pressure in Patients with OSA.

The participant will be randomized to either the modified PAP or market released device group. They will be issued with a PAP device and a pressure-flow logger to be used at home in the usual manner of their PAP therapy for 3 weeks (+/- 4 days), after which participants will return to the FPH sleep laboratory to participate in a overnight PSG study using their first device. At this visit the participant will also swap to the second PAP device; and the above home use repeated on device 2.

Part B After informed consent form the patient will be set up for a standard PSG, and sleep overnight using the modified PAP device, their prescribed mask, and a clean water chamber and breathing tube. This testing will be performed to provide additional flow data to the development engineers. This includes, but is not limited to, distortion testing and adjustment of device parameters during the sleep study. Distortion testing analyses the impact of the PAP pressure changes on the participants breathing or airflow.

Inclusion Criteria:

• Aged 18+
• Diagnosed with OSA by a practicing sleep physician

Exclusion Criteria:

• Patients with a known history of Cerebrospinal fluid leak, abnormalities of the cribriform plate, head trauma and/or pneumocephalus
• Patients with pathologically low blood pressure, pneumothorax, a previous history of pneumothorax, or dehydration.
• Patient with bypassed upper airway
• Other significant sleep disorder(s) (e.g. periodic leg movements, insomnia, central sleep apnea)
• Previous use of a bi-level device with-in the last 2 years (from enrolment date).
• Patients with respiratory failure, bullous lung disease or COPD (Chronic Obstructive Pulmonary Disease).
• Patients with obesity hypoventilation syndrome or congestive heart failure
• Patients that require supplemental oxygen with their CPAP (Continuous Positive Airway Pressure) device
• Patients with implanted or life-supporting electronic medical devices (e.g. cardiac pacemakers)

6 Weeks