The subglottis is the narrowest portion of the pediatric airway, assuming a funnel-shaped internal dimension. In this smaller airway, relatively little edema can significantly reduce the diameter of the pediatric airway, increasing resistance to airflow and work of breathing. With appropriate airway support and antibiotics, most patients improve within 5 days. Cases usually occur in the fall or winter months, mimicking the epidemiology of viral croup. Predominance of morbidity and mortality is related to the potential for acute upper airway obstruction.
Morbidity is related predominantly to induced hypoxic insults.
In the acute phase, if the airway is managed adequately and antibiotic therapy initiated, patients generally do well. In most epidemiologic studies, cases of males are preponderant. Gallagher et al reported 161 cases of patients younger than 16 years. The range was from 3 weeks to 16 years, with a mean age of 4 years. Symptoms may be intermediate between epiglottitis and croup.