The treating clinician in the ED contacted the principal investigator within an hour of an eligible patient's arrival. The pharmacy department maintained a box in the ED holding sequentially numbered, previously randomized concealed envelopes containing either the study (7% HS) or control (0.9% saline) medication. After initial screening and assessment and after consent was obtained, the patient was administered the medication via nebulization driven by 6 L/min O2 flow. Research personnel, the treating physician, and staff who performed the BSS were kept blinded throughout the process. Bronchiolitis severity scores were recorded prior to administering aerosols, after administering the aerosol, and again once the treating clinician determined the final disposition of the patient.