The upper airway is conventionally described as being made up of all the structures that conduct air between the carina and the nares and includes the trachea, larynx, pharynx, nasal airway, and oral airway. Upper airway structures may change their physiologic function in response to pressures around them and anatomic structures near them. Thus, physiologically, the segments of the upper airway behave differently when they are subject to pleural pressures (anatomically intrathoracic) or ambient pressures (anatomically extrathoracic). Furthermore, extrathoracic airway function may change with posture, sleep/wake state, and the function and anatomy of tissues surrounding the airway.
The upper airway evolved anatomically in humans to subserve several important functions including swallowing, breathing, and vocalization.1 The multifunctionality of the upper airway increases the risk of certain diseases (e.g., aspiration and sleep apnea).2 These functions require that different segments of the airway have differing properties. The trachea receives some support by the tracheal rings, the nasal airway is surrounded by rigid structures, and the oral airway has a rigid bony roof, the hard palate. On the other hand, the pharyngeal airway does not have rigid structures supporting it. It is a collapsible tube whose patency is maintained by muscles whose function is affected by arousal state (sleep/wake, and more specifically during sleep, the stage of sleep), the structures around it, and posture. Thus, the pharyngeal airway is divided anatomically and physiologically into the nasopharynx, retropalatal oropharynx, retroglossal oropharynx, and hypopharynx.
Clinically significant obstruction in adults may occur anywhere within the upper airway. Common etiologies of upper airway obstruction (UAO) include neoplasia, scar formation, skeletal facial malformations, infection, inflammatory disorders, trauma, extrinsic compression related to pathology of adjacent structures, and functional changes related to posture and sleep/wake state. Airway obstruction may be classified as extrinsic, intrinsic, or mixed (Fig. 47-1).
Classification of airway tumor involvement. A. Intrinsic stenosis. Purely endoluminal tumor without breech of the cartilage. B. Extrinsic stenosis. Extraluminal tumor causing mass effect but no endoluminal involvement. C. Mixed stenosis. Extraluminal tumor causing mass effect and endoluminal involvement.
UAO can be acute and life-threatening, or chronic and resulting in significant symptoms, some of which may not even relate to the respiratory system. Initial management of acute UAO focuses on securing the airway and stabilizing the patient. Often the intervention is surgical. Some diseases require bypassing the obstruction using translaryngeal intubation or tracheostomy. Definitive long-term management depends on the underlying etiology and physiology and may include both medical and surgical interventions. The still-evolving fields of imaging and interventional pulmonology offer new diagnostic and management modalities. This chapter provides an overview of acute and chronic UAO in adults and focuses on clinical presentation, assessment, etiology, and management. Obstructive sleep apnea is covered in Chapter 98 of this volume.