Study Population

Children 24 months or younger admitted with a primary or secondary diagnosis of bronchiolitis to the general pediatric infant and toddler unit through the ED at an urban tertiary care center over a 4-year period from April 1, 2011, to March 31, 2015, were identified by using International Classification of Diseases, Ninth Revision codes 466.11 and 466.19. Children who required ventilatory support at the time of presentation to the ED and children who were not evaluated in the ED were excluded. Risk factors for respiratory decompensation may be different for children with a concomitant pneumonia; therefore, children diagnosed with pneumonia by a hospital medicine attending physician and treated with antibiotics were excluded from the study. In addition, risk factors for respiratory decompensation are likely also different for children with complex comorbidities that impact respiratory status. Therefore, to identify a cohort of otherwise healthy children, by using the method described by Ralston et al,¹⁴ children with chronic illness (cardiac, pulmonary, neurologic, chromosomal, or craniofacial comorbidities) were also excluded. Patients were excluded by using International Classification of Diseases, Ninth Revision codes, and exclusions were verified by manual chart review; this methodology was reviewed by 2 study investigators to ensure accuracy.