Respiratory Support Modalities in the ICU Setting

Definitions and Terminology

High flow nasal cannula (HFNC) is defined as a respiratory support device that delivers heated and humidified oxygen at high flow rates (up to 60 L/min) through a nasal cannula interface, as defined by the American Thoracic Society 3, 4
HFNC is also referred to as HFNO (high-flow nasal oxygen) or HHHFNC (heated, humidified high-flow nasal cannula) in some clinical contexts, according to the American College of Chest Physicians 2
In pediatric settings, HFNC is specifically defined as flow delivered at ≥1 L/kg/min for patients up to 10 kg and ≥10 L/min for patients above 10 kg, as recommended by the American Academy of Pediatrics 2
Nasal CPAP is defined as positive pressure with a single continuous distending pressure delivered without an artificial airway via an interface that aims to provide an occlusive fit, as defined by the American College of Chest Physicians 2

HFNC is categorized as a form of noninvasive respiratory support distinct from both conventional oxygen therapy and noninvasive ventilation, according to the European Respiratory Society 5, 4
Nasal CPAP is classified as a form of noninvasive ventilation (NIV) in the ICU, though some literature uses NIV and CPAP terminology interchangeably, as noted by the American College of Chest Physicians 1, 2
The key distinction in ICU terminology is that HFNC delivers high flow without requiring an occlusive interface, while nasal CPAP delivers continuous positive pressure through an occlusive nasal interface, as highlighted by the American College of Chest Physicians 2

Nasal CPAP is documented with pressure level (cmH₂O) and FiO₂ parameters, as recommended by the American College of Chest Physicians 2