Upper airway imaging in relation to obstructive sleep apnea.

A variety of imaging techniques have been used to assess upper airway size and function in patients with OSA. Each technique has certain advantages and limitations. Many of the imaging techniques study awake and upright patients, whereas OSA typically occurs while the patient is asleep in the supine position. Upper airway imaging may identify specific upper airway abnormalities that cause OSA. Furthermore, the majority of patients with OSA have a narrow and more collapsible airway in the velopharynx. Upper airway occlusion during sleep usually starts in the velopharynx and extends caudally. Obesity results in both extrinsic upper airway narrowing and soft tissue enlargement. Upper airway edema may occur secondary to OSA and subsequently exacerbate the OSA by causing further upper airway narrowing. Upper airway imaging provides some insights into the mechanism of action of certain treatments and is increasingly used to help direct treatment. Weight loss reduces upper airway collapsibility. Nasal CPAP increases upper airway size and reduces upper airway edema. UPPP enlarges the oropharynx and reduces upper airway collapsibility. Patients with a narrow upper airway, particularly relative to tongue size, have a good response to UPPP.