Mechanisms of Pharyngeal Collapse in Sleep Apnea, Study D

In obstructive sleep apnea (OSA), the upper airway recurrently closes during sleep. The mechanisms that lead to airway closure are not completely understood. Some studies have shown that there is progressive narrowing of the pharyngeal airway across breaths during expiration (Progressive Expiratory Narrowing, PEN) preceding an obstructive apnea. The investigators will assess the viscoelastic properties of the pharyngeal airway and its role in PEN.

In obstructive sleep apnea, the upper airway recurrently closes during sleep. The mechanisms that lead to airway closure are not completely understood. Some studies have shown that there is progressive narrowing of the pharyngeal airway across breaths during expiration (Progressive Expiratory Narrowing, PEN) preceding an obstructive apnea. The investigators will test how the viscoelastic properties of the airway influence PEN. To this end, the investigators will visualize the pharynx of sleep apnea patients using a thin endoscope and will induce central apneas during sleep. Pharyngeal cross-sectional area will be recorded during incremental changes in pharyngeal pressure during central apneas.

The investigators will determine elasticity of the upper airway during induced central apneas by dividing the change in airway pressure by the change in airway cross-sectional area. The time frame for the outcome of this study is equal to the duration of the induced central sleep apnea (usually less than 40 seconds).

Inclusion Criteria: Normal subjects or patients with OSA Exclusion Criteria: Any unstable cardiac condition (other than well controlled hypertension) or pulmonary problems. Any medication known to influence breathing, sleep/arousal or muscle physiology Concurrent sleep disorders (insomnia, narcolepsy, central sleep apnea or parasomnia) Claustrophobia Inability to sleep supine Allergy to lidocaine or oxymetazoline hydrochloride For women: Pregnancy