High-Flow Nasal Cannula: The Challenge of Studying What Cannot Be Measured

As the number 1 reason for hospitalization of infants, bronchiolitis is a commonly encountered and studied pediatric illness.¹  Despite decades of research, the recommended treatment remains supportive care.¹  Delivery of heated and humidified air through a high-flow nasal cannula (HFNC) to support work of breathing has become common after initial single-center observational studies suggested HFNC might provide some positive pressure and reduce mechanical ventilation rates.^2–4  However, these studies were poorly adjusted for confounding factors and focused mainly on outcomes in patients already in the ICU, rather than on clinical outcomes when HFNC was used outside the ICU.^2–4  Since that time, randomized controlled trials comparing early use of HFNC to standard nasal cannula failed to demonstrate improvements in clinical outcomes.^5–7  Furthermore, the widespread adoption of HFNC outside the ICU has coincided with paradoxical increases in ICU utilization, noninvasive ventilation rates,...