The two splints are coupled so the mandible is stabilised. Mandibular advancement improves passive pharyngeal anatomy, enlarging the upper airway and reducing its tendency to collapse during sleep.
Air entering the anterior port travels through both sides of the appliance and exits behind the last molars. This provides an oral inspiratory airflow path to the pharynx. In physiological testing, opening this airway reduced negative pharyngeal pressure swings during sleep thus reducing potential for sucking the airway shut.
The valve opens with inspiration and seals off during expiration. Restricted expiratory outflow generates oral expiratory positive airway pressure (oral EPAP), helping maintain pharyngeal patency late in expiration and into the transition to the next inspiration.
The upper airway can narrow toward the end of expiration, just before the next inspiratory effort generates negative pressure. Maintaining positive pressure late in expiration helps preserve airway patency as the next breath begins.