Nasal CPAP therapy is the most effective treatment for OSA, and it has become the standard of care for this condition. (It is also effective for treating mixed apneas and some central apneas.) The CPAP device consists of a blower unit that produces continuous positive-pressure airflow. This airflow is usually applied at the nose and is then directed through the UA. CPAP increases the caliber of the airway in the retropalatal and retroglossal regions (see the image below). It increases the lateral dimensions of the UA and thins the lateral pharyngeal walls, which are thicker in patients with obstructive sleep apnea than in people without obstructive sleep apnea.