Overview of Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) affects nearly one billion adults worldwide and represents a multifactorial disorder in which pharyngeal collapse during sleep produces intermittent hypoxia, sleep fragmentation, and downstream cardiometabolic sequelae. This chapter provides a comprehensive, multi-authored overview of OSA for the practicing sleep surgeon, organized around twelve thematic sections. The opening sections trace the historical arc from early palatal procedures and tracheostomy through the CPAP revolution of 1981, the multilevel surgical paradigm, and the emergence of implantable hypoglossal nerve stimulation. Pathophysiology is addressed through the lens of four interacting endotypes—pharyngeal collapsibility (Pcrit), arousal threshold, loop gain, and dilator muscle responsiveness—that together determine collapse severity and treatment response. Subsequent sections examine obstruction systematically at each upper airway level: nasal and nasopharyngeal, retropalatal and oropharyngeal, and hypopharyngeal and laryngeal, with emphasis on drug-induced sleep endoscopy (DISE) and the VOTE classification as tools for phenotype-guided surgical planning. The role of surgery within multidisciplinary OSA care is examined alongside outcome metrics, patient selection principles, and perioperative management. Dedicated sections address PAP therapy from the surgeon's perspective, the bidirectional relationship between obesity and OSA, powered surgical instruments (coblation, microdebrider, radiofrequency ablation, lasers, electrocautery, and piezosurgery), and the surgical management of pediatric OSA from adenotonsillectomy through craniofacial surgery and hypoglossal nerve stimulation. Throughout, the chapter emphasizes phenotype-directed, multilevel strategies as the cornerstone of contemporary sleep surgery practice.