Bronchiolitis is the most common lower respiratory tract infection to affect infants and toddlers. High-risk patients include infants younger than 3 months, premature infants, children with immunodeficiency, children with underlying cardiopulmonary or neuromuscular disease, or infants prone to apnea, severe respiratory distress, and respiratory failure. Bronchiolitis is a self-limited disease in healthy infants and children. Treatment is usually symptomatic, and the goal of therapy is to maintain adequate oxygenation and hydration. Use of a high-flow nasal cannula is becoming common for children with severe bronchiolitis.