Conventionally, oxygen is given at 4 to 6 L/min through nasal cannula for supplementation of oxygen. The FiO2 achieved through this can be up to 0.4. Flows more than this can cause dryness to the nasal mucosa without much increase in the FiO2. High-flow nasal cannula (HFNC) uses flow up to 60 L/min. Positive end-expiratory pressure is created in the nasopharynx and it is also conducted to the lower airways. Studies have shown HFNC improves washout of CO2 and decreases respiratory rate. Patient compliance also improves due to the comfort of the cannula compared to the non-invasive ventilation through a mask.
Part of the book: Mechanical Ventilation