PROJECT SUMMARY Despite the clinical effectiveness of Continuous Positive Airway Pressure (CPAP) for obstructive sleep apnea (OSA), patient compliance with the therapy remains a major cause of treatment failure. This chronic sleep-related breathing disorder that affects 5-10% of the population is associated with various serious adverse outcomes, including cardiovascular diseases. OSA involves a decrease or complete halt in airflow despite an ongoing breathing effort. It occurs when muscles relax during sleep, causing soft tissues in the posterior pharynx to collapse and obstruct the upper airway. CPAP, which is broadly considered first-line therapy for OSA, keeps the upper airway open with positive airway pressure to prevent airway obstruction by the collapse of the soft tissues. However, CPAP requires a tight seal between the mask and the patient's face closed system to maintain airway pressure. Although effective when used consistently, CPAP is not well tolerated by many patients largely due to the discomfort of the tight-fitting mask of current devices. A promising new development derives from our recent work based on the re-application of “vortical airflow,” a flow control mechanism commonly used in aerospace engineering applications. The unique aerodynamic properties of vortical airflow enable it to pressurize the upper airways without the need for a tight-fitting mask. The current project is designed to accomplish two critical milestones. First, the current prototype will be advanced to function as a stand-alone unit with an overall size similar to currently marketed CPAP devices. Second, it will demonstrate that the nasal interface of the new prototype is more comfortable than CPAP masks.