• compare the rate of admission to hospital between the study and control groups [ Time Frame: 1 hour after treatment ends ] [ Designated as safety issue: No ]
  

• change in the RDAI between study entry and post-treatment. [ Time Frame: 1 hour after treatment ends ] [ Designated as safety issue: No ]
  

Patients presenting to the Emergency Room (ER) or out-patient department with a diagnosis of moderately severe bronchiolitis (as defined by inclusion/exclusion criteria below) will be approached for entry into the study. After the initial routine assessment by the ER medical and nursing staff, informed consent will be obtained and the infant will be randomized to receive treatment in a double-blinded fashion with 4 ml of nebulized study solution containing 1 mg salbutamol (bronchodilator) plus either 3% hypertonic saline (HS, study group) or 0.9% saline (NS, control group) every 20 minutes for a total of 3 doses. After an observation period of 1 hour following the last dose, the infant will be reassessed by the attending physician in the ER for disposition (admit, discharge home, remain in ER for further treatment) at which point the infant's active involvement in the study will end. All subsequent therapy, if needed, will be at the sole discretion of the attending physician. The family of each recruited subject will be contacted by phone 7 days later to assess resolution of symptoms or the presence of any unexpected adverse effects.

Clinical response to the above treatment will also be determined independently by the study physician or designate utilizing a standardized respiratory scoring system, the Respiratory Distress Assessment Instrument (RDAI), at study entry and after the post-treatment observation period. The primary outcome measure is to compare the rate of admission to hospital between the study and control groups. A secondary outcome measure will involve the assessment of change in the RDAI between study entry and post-treatment.

The infant will remain in the ER throughout the study period and receive standard ongoing monitoring by the nursing staff. In the unlikely event of significant clinical worsening during this period, the ER physician on duty will be notified to assess and intervene as he/she feels appropriate. The site study investigator will be immediately notified of all such occurrences by the research assistant involved.

The study will be conducted over a single bronchiolitis season from November 1, 2008 to April 1, 2009. There will be 2 study sites as listed below with the name of the study site director.

• Royal Victoria Hospital of Barrie (Emergency Department), Barrie ON (B.A. Kuzik, MD, FRCP (lead investigator))
• Kingston General Hospital (Emergency Department) and Hotel Dieu Hospital (Emergency Department, Children's Outpatient Centre), Kingston ON (M. P. Flavin, MB, MRCP, FRCP)