Upper-airway collapsibility - Measurements and sleep effects

Study objectives: Obstructive sleep apnea (OSA) is characterized by repetit ive pharyngeal collapse during sleep. Several techniques have been proposed to assess the collapsibility of the upper airway in awake humans, but slee p-wake comparisons have rarely been attempted and there air? few studies co mparing OSA patients to control subjects, We sought to compare two collapsi bility measurement techniques between normal and apneic subjects, and betwe en wakefulness and sleep. Design: We conducted three studies. First, we examined whether collapsibili ty assessed by negative pressure pulses (NPPs) during wakefulness reflected values during sleep in 21 normal subjects. Second we determined in these n ormal subjects whether collapsibility during sleep assessed by NPPs was pre dictive of collapsibility measured by inspiratory resistive loading (LRL). Finally, we compared upper-airway collapsibility between apnea patients (n = 22) and normal volunteers (n = 38) during wakefulness by MPPs, Setting: Clinical and research laboratories at the Brigham and Women's Hosp ital. Participants: Two populations of normal subjects (n = 21 and n 38) and OSA patients (n = 22), Measurements and results: Collapsibility during wakefulness, as measured by NPPs, correlated significantly with collapsibility during sleep (r = 0.62; p = 0.003), There was also a significant correlation between the two measu res of collapsibility (IRL and NPP) during sleep (r = 0.53; p = 0.01). Both measures revealed a significant increase in pharyngeal collapsibility duri ng sleep as comp:ucd to wakefulness. Finally, apnea patients had significan tly greater pharyngeal collapsibility than control subjects during wakefuln ess (p = 0.017), Conclusions: These data suggest that upper-airway collapsibility measured d uring wakefulness does provide useful physiologic information about pharyng eal mechanics during sleep and demonstrates clear differences between indiv iduals with and without sleep apnea.