Patient selection Informed consent was obtained from a parent or legal guardian of each patient enrolled in the study. Patients age 6 weeks to ≤ 18 months presenting to the ED between October and March over a 2-year period (2010-2012) with bronchiolitis (defined as viral respiratory illness and first episode of wheeze) and a BSS score of ≥ 4 were eligible for the study. Exclusion criteria were a previous history of wheezing; diagnosis of asthma; any use of bronchodilators within 2 h of presentation; gestational age ≤ 34 weeks; history of congenital heart disease, chronic pulmonary or chronic renal disease; oxygen saturation of ≤ 85% at the time of recruitment; severe disease requiring intensive care unit admission, or inability to obtain informed consent. Depending on the availability of the principal investigator (a pediatric emergency medicine fellow), a convenience sample was used to recruit patients. The ED physicians and staff were notified of the fellow's hours of availability by way of a call schedule that was posted in the ED.