Stridor is noisy breathing coupled with increased inspiratory efforts, such as nasal and rib-cage flaring and suprasternal and sternal retraction. Severe airway obstruction may result in cyanosis, respiratory distress and fatigue, pneumothorax, pneumomediastinum, and death. Inspirat-ory stridor indicates lesions above the vocal cords. Lesions distal to the vocal cords usually produce expiratory stridor. Biphasic stridor is most characteristic of obstruction at the level of the subglottic space.
Postextubation stridor manifests as a barky or croupy cough; it usually develops within the first hour after extubation, but it can develop as late as 24 hours after extubation. It arises from glottic and subglottic edema caused by ischemia of the tracheal mucosa as a result of pressure by the endotracheal tube (ETT). The symptoms appear after extubation because compression by the ETT prevents narrowing of the tracheal lumen. Upon the removal of the ETT, edema develops and narrows the tracheal lumen. Symptoms include expiratory stridor, hoarseness, and chest retractions. If the airway obstruction becomes severe, arterial desaturation occurs, and reintubation may be required to maintain a patent airway.
The following factors increase the risk of postextubation stridor:
ETT: Tightly fitting in the trachea with a leak pressure above 25 cm H2O. Leak pressure should be between 10 and 25 cm H2O to permit ventilation and to maintain perfusion of the tracheal mucosa.
Age: Children younger than 4 years old are at greater risk because of their disproportionately smaller airway lumen.
Intubation maneuver: Risk increases with multiple and/or traumatic attempts.
Duration of endotracheal intubation: Risk for trauma or ischemia increases with prolonged intubation.
Head or neck surgery: Frequent position changes of the head and neck increase the risk for trauma or ischemia of tracheal mucosa.
Ongoing upper airway infection or a recent bout of infectious croup: Tracheal mucosa is inflamed and edematous.
Extubation: Coughing vigorously when an ETT is present.
Subglottic stenosis: Congenital or acquired lesions or syndromes associated with a disproportionately narrow airway for age, such as Down syndrome.