Acute obstruction of the upper airway can be immediately life-threatening and must be relieved promptly to avoid asphyxia. Causes of acute upper airway obstruction include trauma to the larynx or pharynx, foreign body aspiration, laryngospasm, laryngeal edema from thermal injury or angioedema, infections (acute epiglottitis, Ludwig angina, pharyngeal or retropharyngeal abscess), and acute allergic laryngitis.
Chronic obstruction of the upper airway may be caused by goiter, carcinoma of the pharynx or larynx, laryngeal or subglottic stenosis, laryngeal granulomas or webs, or bilateral vocal fold paralysis. Laryngeal or subglottic stenosis may become evident weeks or months after endotracheal intubation. Laryngomalacia refers to the collapse of the supraglottic structures during inspiration. It is the most common congenital anomaly of the larynx, manifests in infancy, and is usually resolved by 12–18 months. Inspiratory stridor, intercostal retractions on inspiration, a palpable inspiratory thrill over the larynx, and wheezing localized to the neck or trachea on auscultation are characteristic findings. Flow-volume loops may show characteristic flow limitations. Soft-tissue radiographs of the neck may show supraglottic or infraglottic narrowing. CT and MRI scans can reveal exact sites of obstruction. Flexible endoscopy may be diagnostic, but caution is necessary to avoid exacerbating upper airway edema and precipitating critical airway narrowing.
Vocal fold dysfunction syndrome, a type of inducible laryngeal obstruction, is characterized by paradoxical vocal fold adduction causing acute or chronic upper airway obstruction, or both. It presents as dyspnea and wheezing that may mimic asthma but may be distinguished from asthma or exercise-induced asthma by the lack of response to bronchodilator therapy, normal spirometry immediately after an attack, spirometric evidence of upper airway obstruction in a flow-volume loop, and a negative bronchial provocation test. However, vocal fold dysfunction may coexist with asthma, be induced by exercise, inhalational irritant exposures, laryngopharyngeal reflux of gastric contents, or psychological stress. Definitive diagnosis requires direct visualization of adduction of the vocal folds on inspiration. Treatment consists of addressing underlying precipitants (including psychogenic contributors), and speech therapy.
et al. Acute upper airway obstruction. N Engl J Med. 2019;381:1940.
AA. Vocal cord dysfunction: the spectrum across the ages. Immunol Allergy Clin North Am. 2019;39:547.