Pathophysiology of adult obstructive sleep apnea

Pathophysiology of Adult Obstructive Sleep Apnea
Danny J. Eckert1 and Atul Malhotra1,2
1 Division of Sleep Medicine, Sleep Disorders Program, Brigham and Women’s Hospital, and Harvard Medical School; and 2Division of Pulmonary/Critical Care Medicine, Brigham and Women’s Hospital, Boston, Massachusetts

Obstructive sleep apnea (OSA) is a common disorder characterized by repetitive narrowing or collapse of the pharyngeal airway during sleep. The disorder is associated with major comorbidities including excessive daytime sleepiness and increased risk of cardiovascular disease. The underlying pathophysiology is multifactorial and may vary considerably between individuals. Important risk factors include obesity, male sex, and aging. However, the physiological mechanisms underlying these risk factors are not clearly understood. This brief review summarizes the current understanding of OSA pathophysiology in adults and highlights the potential mechanisms underlying the principal risk factors. In addition, some of the pathophysiological characteristics associated with OSA that may modulate disease severity are illustrated. Finally, the potential for novel treatment strategies, based on an improved understanding of the underlying pathophysiology, is also discussed with the ultimate aim of stimulating research ideas in areas where knowledge is lacking. Keywords: arousal; genioglossus; lung volume; upper airway; ventilatory control stability

Obstructive sleep apnea (OSA) is characterized by recurrent collapse of the pharyngeal airway during sleep, resulting in substantially reduced (hypopnea) or complete cessation (apnea) of airflow despite ongoing breathing efforts. These disruptions to breathing lead to intermittent blood gas disturbances (hypercapnia and hypoxemia) and surges of sympathetic activation. Loud snoring is a typical feature of OSA and in most cases the culmination of a respiratory event is associated with a brief awakening from sleep (arousal). These