Impact on upper airway mechanics of a built in oral appliance airway in patients with obstructive sleep apnoea.

Part 1 – Night 1 Assessment of nasal obstruction using rhinomanometry followed by observational level 1 diagnostic sleep study without oral appliance to evaluate relationship between breathing route and Apnoea-Hypopnea Index (AHI), Pharyngeal pressures measured throughout will also be used to evaluate site of upper airway collapse. Participants with supine AHI <15 and >60 or unable to demonstrate ability to sleep in the supine position or sleep with the required instrumentation, will not go on to participate in Part 2 of the study. Part 2 – Night 2 and 3 Device - The O2Vent T is a customized oral appliance similar in appearance to a mouth guard. to treat snoring and sleep apnoea. The main structure which forms the breathing port at the front leading to the airways on each side to the rear of the appliance, is made from polished medical grade titanium customized to the maxillary arch. The "landing" area or inserts for the top and lower teeth is customized to the patient's dentition and are made from dual laminate material. The upper insert is fixed to the titanium arch whilst the lower insert is positioned in an advanced position to bring the jaw forward. Further titration is possible with a screw mechanism. Night 2 – Interventional study with O2Vent T and titration as per titration protocol to optimize level of advancement. Prior to titration, the study dentist will define the limits of advancement for the titration night so that it does not exceed 100%. 1. The titration will commence at the Zero position which will be set at 50% of maximum protrusion 2. The Zero position will be held to the end of the first REM period 3. At the conclusion of the first REM period, titration will commence in 1 mm increments in response to AHI greater than 10 or <50% reduction in the preceding 15 minutes of sleep 4. At least 15 minutes of consistent sleep (not interrupted by periods of wakefulness) should be observed prior to further advancement. 5. Advancement to occur until any of the following conditions are met: a. limits of advancement as defined by dentist b. the lower of AHI <10 reached or >50% reduction c. Limit of device i.e. +7mm reached 6. Advancement to occur in sleep only. No advancement to occur during wakefulness or Stage 1 sleep. Night 3 – Interventional study with the device airway being opened and closed alternating every 30 minutes. The level of advancement throughout will be the optimal advancement determined on night 2. Pharyngeal pressures measured throughout. Whilst the device airway is closed, breathing is possible through the nose. Whilst the device airway is open, breathing is possible through the nose and the device. Night 2 will occur approximately 2 months after Night 1 to allow for manufacture of device and acclimatization. Night 3 will occur up to 2 weeks after night Night 2. Monitoring of adherence is not applicable.