Upper airway mechanics: The influence of gender

Obstructive sleep apnea is an important disease characterized by repetitive pharyngeal collapse. This disease leads to substantial sleep fragmentation with associated hypoxemia and hypercapnia. Individuals with this disease have compromised pharyngeal anatomy, characterized by a positive critical closing pressure during sleep. During wakefulness, neuromuscular compensatory reflexes lead to increased pharyngeal dilator muscle activation. However, with the onset of sleep, these reflex mechanisms fail leading to pharyngeal collapse. For unclear reasons, this disease is substantially more common in men than in women. In order to characterize the mechanisms underlying this gender predisposition, we studied a total of 41 normal subjects. It was found that the major differences between the genders with regard to the upper airway appear to be anatomical. Gender-specific differences in pharyngeal airway length may explain much of the increased propensity for pharyngeal airway collapse observed in men. These findings may have relevance to the pathogenesis of obstructive sleep apnea syndrome.