High-flow oxygen therapy via nasal cannula provides positive pressure support to the oropharynx, creating positive end-expiratory pressure in the lower airway. This effect is similar to that of continuous positive airway pressure ventilation, which exerts a force to keep the alveolar airways from collapsing due to increased surface tension during expiration.

High-flow oxygen therapy via nasal cannula is applied in cases of patients with acute hypoxemic respiratory failure, postoperative respiratory failure, acute pulmonary edema, acute heart failure, sleep apnea... with good results. However, this therapy also has many limitations.

High-flow nasal cannula oxygen therapy can significantly reduce both mortality and intubation rates in immunocompromised patients with acute respiratory failure, improving dyspnea and comfort in patients presenting to the emergency department with dyspnea and/or hypoxemia.