The investigators will assess the evolution of hospital admission rates and the length of hospital stay in two hospitals that use 5.85% nebulized hypertonic saline for the treatment of bronchiolitis and in two hospital that do not use these nebulizations. If nebulized hypertonic saline is effective in this setting, then the hospitalization rates and length of stay should be lower during the year of hypertonic saline use compared to two previous years when this therapy was not used. These parameters would not be modified in centers that do not use hypertonic saline.