[High-flow oxygen therapy-Chances and risks].

High-flow oxygen therapy (high flow nasal cannula, HFNC), in which an oxygen-air gas mixture is applied at flow rates between 30 and 70 L/min, is a technically simple and highly effective procedure for the treatment of hypoxemic respiratory insufficiency. Furthermore, HFNC can be used during bronchoscopy for oxygenation, before intubation for preoxygenation, and after extubation to avoid reintubation. The high gas flow prevents the patient from inspiring ambient air, allowing precise adjustment of an inspiratory oxygen fraction; furthermore, a positive end-expiratory pressure is built up by a resulting dynamic pressure, mucociliary clearance is improved by humidification and warming of the air breathed and the work of breathing is reduced by flushing the upper airways. Compared with conventional oxygen therapy, aerosol formation is not increased by HFNC; therefore, this procedure can also be used for patients with coronavirus disease 2019 (COVID-19). In hypercapnic respiratory failure the data are inconclusive and in this case noninvasive ventilation should currently be preferred instead of HFNC. It is important to remember that patients treated with HFNC are critically ill and therefore require continuous monitoring. It must be ensured that an escalation of therapy, e.g. to intubation and invasive ventilation, can be performed at any time.