Objective: The investigators aimed to compare the heated humidified high-flow nasal cannula (HHHFNC) flow rate of 1-L/kg/min (1L) with 2-L/kg/min (2L) in patients with severe bronchiolitis presenting to the pediatric emergency department.

Study design: The investigators performed a study in which all patients were allocated to receive these two flow rates. The primary outcome was admitted as treatment failure, which was defined as a clinical escalation in respiratory status. Secondary outcomes covered a decrease of respiratory rate (RR), heart rate (HR), the clinical respiratory score (CRS), rise of peripheral capillary oxygen saturation (SpO2) and rates of weaning, intubation and intensive care unit (ICU) admission.

Keywords: Bronchiolitis, Emergency department, High-flow nasal cannula, Flow rate

Inclusion Criteria:

• Clinical diagnosis of severe bronchiolitis
• Must be less than 24 months
• Must have presented to the emergency department

Exclusion Criteria:

• Immediate invasive ventilation and/or intensive care unit admission
• Congenital heart disease,
• Chronic lung disease
• Neuromuscular disease
• Netabolic disease
• Craniofacial anomalies
• Immunocompromised
• Bacterial pneumonia
• Pneumothorax
• Nasal trauma

All patients with a clinical diagnosis of severe bronchiolitis, aged less than 24 months and presenting to the emergency department