High-flow oxygen cannula: a very effective method to correct severe hypoxemia

Nasal high-flow (NHF) oxygen administration through a cannula is a simple and very effective way to correct severe hypoxemia. Initially developed in neonatal units, the system has been more recently adapted for use in adults. Several systems are now available, delivering warm, humidified oxygen at flows of up to 60 L/min. In addition to low costs and ease of application, NHF has several distinct features. First, the high flow rates can flush expired CO₂ from the upper airways and reduce dead space. Second, it creates a small continuous positive airway pressure (CPAP), typically of 2-4 cmH₂O. Third, the high flow, which exceeds the peak inspiratory flow of the patient, can limit the entrainment of room air during inspiration, and can thus provide a more stable oxygen concentration in the inspired gases. Fourth, the heated, humidified oxygen administered at high flow rates may help to prevent the stagnation of secretions and the formation of atelectasis. These features contribute to make the system particularly well-tolerated by patients with severe respiratory failure. Maggiore et al. (1) recently showed that use of NHF after extubation resulted in better oxygenation than with Venturi mask oxygen therapy for the same set FiO₂, and was associated with better patient comfort, fewer desaturations and interface displacements, and a lower reintubation rate.