Pathophysiology of Obstructive Sleep Apnea (OSA)

Obstructive sleep apnea (OSA) is a complex disorder characterized by total or partial collapse of the upper airways (UA) during sleep, causing obstructive apneas or hypopneas, respectively. During respiratory events, respiratory efforts occur against the restricted or collapsed upper airway, hypoxia and hypercapnia develop, and sympathetic activation increases. The main symptoms of OSA are intermittent snoring and excessive daytime sleepiness. OSA is often associated with obesity, hypertension, and increased cardiovascular risk. Pathophysiological aspects include: anatomical and physiological determinants of UA closure, and immediate and long-term consequences of chronic intermittent hypoxia (CIH), which is believed to be the most relevant alteration induced by OSA. This chapter will briefly review OSA pathophysiology, with special attention to physiological phenotypes of OSA, and the role of intermittent hypoxia in the pathogenesis of cardiometabolic abnormalities.