Predictive Accuracy of MATRx Plus in Identifying Favorable Candidates for Oral Appliance Therapy

Obstructive sleep apnea (OSA) is a common disease that is largely un-diagnosed and untreated. Standard treatment for obstructive sleep apnea, nasal continuous positive airway pressure (CPAP), entails use of a nose mask to deliver positive pressure which dilates the pharynx and eliminates obstruction. This therapy is highly efficacious and benign but is associated with low adherence, particularly in non-sleepy apneics with disease of mild and moderate severity. The principal alternative to CPAP therapy is oral appliance (OA) therapy in which a custom made mandibular advancement splint (MAS) is used to protrude the mandible during sleep, thereby opening the pharyngeal airway. OA therapy, while preferred and well accepted by most participants, is not uniformly efficacious. Additionally, uncertainty regarding the patient's response to OAT and the effective target mandibular position can lead to a significant time span between diagnosis and initiation of effective treatment. Furthermore, knowledge of the effective target mandibular position supports the use of new OA design and manufacturing processes that can further reduce the time and cost in delivering the therapy.

Zephyr Sleep Technologies (the Sponsor) has developed a method of identifying OAT responsive participants and their efficacious mandibular protrusion. Recently, Zephyr Sleep Technologies developed a portable device that avoids this requirement and can be used in a multi-night test in the home. Using a feedback controlled mandibular positioner (FCMP), the device measures and analyzes respiratory airflow and oxygen saturation and makes decisions in real-time about moving the mandible. The FCMP device was tested in a blinded, bi-phase clinical study in which participants with mild-to-severe sleep apnea (n=202) underwent two full-night studies in the home. Data from phase 1 were used to develop a predictive method, and data from phase 2 were used to prospectively test the accuracy of the predictive method. An efficacious mandibular position was also predicted, and each participant was treated with a custom oral appliance set to that position. Data from both phases were used to evaluate the feasibility of use of the device in the home.

A random forest machine learning system was used to develop and test the predictive method. The overall oral appliance success rate was 76% for phase 1 and 71% for phase 2. The overall predictive accuracy was 88%. Values for sensitivity and specificity were 85% and 93%, respectively. Positive and negative predictive values were 97% and 72%, respectively. The effective target protrusive position was identified in 86% of cases. The studies were conducted independently by the participants in their homes, though due to limitations in the early prototype design, a clinical coordinator visited the home to set up the equipment prior to each night of study. No significant problems were encountered, and no significant risks were identified. The results of the clinical trial show that the auto-titrating mandibular positioner is suitable for use in the home and accurately predicts OAT outcome as well as target protrusive position.

Based on the results of this study, Zephyr developed a commercially available device which has been approved for sale in Canada (Health Canada device license #97614). The device, branded MATRx plus, functions as both a sleep recorder as well as a home-based system to select patients for oral appliance therapy. This commercially available device is currently being used in three separate usability trials to quantify the usability of the device and the benefits of an improved workflow through adoption of the new technology in a dental practice.

Evidence has recently appeared to indicate that the change in pharyngeal volume caused by protrusion of the mandible, measured while awake, correlates with the change in apnea-hypopnea index (AHI) achieved by OAT, measured while asleep. This is the first convincing evidence that an awake measurement of the pharyngeal airway correlates with the improvement in respiratory status during sleep induced by an oral appliance. The implication is that a simple conebeam CT of the pharynx can predict outcome with OAT. Accordingly, we shall carry out conebeam CTs in the research protocol, both at rest position of the mandible and at 90% of maximal protrusion.

The purpose of this study is to test whether the predictive accuracy of the FCMP in the home environment is improved by the commercial design and whether patients predicted to be suitable for oral appliance therapy have long term adherence.