Update in Sleep Medicine 2011

Abstract

Although it is unclear why all respiratory events in obstructive sleep apnea (OSA) are not terminated with a recognizable cortical arousal, it has been hypothesized that events terminated without arousal may lead to more stable breathing. Jordan and colleagues attempted to define the physiologic parameters immediately related to stable breathing, including airflow, genioglossus and tensor palatini muscle activity, and airway resistance, after respiratory events terminated with or without cortical arousal (1). They hypothesized that respiratory events terminated without cortical arousal would produce less hyperventilation and less secondary events due to higher pharyngeal dilator activity compared with events with arousal. Sixteen patients with mild to severeOSA already treated with continuous positive airway pressure (CPAP) were studied. Using a sudden drop in CPAP pressure to subtherapeutic levels, they found that respiratory events terminated without arousal led to less hyperventilation and less secondary events (primarily hypopneas) compared with events terminated with arousal. This reduction in inspiredminute ventilation and subsequent events was not accounted for by differences in residual pharyngeal dilator activity. Specifically, secondary events were marked by less flow limitation and greater pharyngeal dilator activity relative to the initial event whether cortical arousal was present or not. These findings question the notion of arousal predisposing patients to further obstructive events.