Mechanisms of Pharyngeal Collapse in Sleep Apnea, Study A

In obstructive sleep apnea, the upper airway recurrently closes during sleep. The mechanisms that lead to airway closure are not completely understood. While the airway of some people narrows and airflow decreases during inspiration due to increasing inspiratory effort, others maintain constant airflow throughout inspiration. Airway neuromuscular reflexes may protect against airway narrowing that occurs due to increasing inspiratory effort. To test this hypothesis, the investigators will initially measure airway neuromuscular reflex and inspiratory flow and then attenuate neuromuscular reflex through topical pharyngeal anesthesia to observe the effects on inspiratory flow.

The mechanisms that lead to airway closure are not completely understood. While the airway of some people narrows and airflow decreases during inspiration due to increasing inspiratory effort, others maintain constant airflow throughout inspiration (negative effort dependence, NED). The investigators hypothesize that upper airway neuromuscular reflexes may protect against narrowing that occurs due to increasing inspiratory effort. Topical oropharyngeal anesthesia has been shown to reduce neuromuscular reflexes. Thus, the investigators also hypothesize that patients with stable inspiratory flow will develop NED once the reflexes have been impaired with topical anesthetic. The investigators plan to: measure upper airway muscle EMG to assess how it corresponds to the presence or absence of NED. This aim will allow us to test the hypothesis that robust upper airway muscle reflexes can protect against NED. reduce upper airway muscle activity and reflexes by topical oropharyngeal anesthesia. This will allow us to test the hypothesis that attenuated upper airway muscle activity induced by topical anesthesia can induce NED.

The magnitude of negative effort dependence will be expressed as the percent decrease in inspiratory flow from Vmax. NED will be compared before and after topical upper airway anesthesia

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 HCl For women: Pregnancy