Physiopathological rationale of using high-flow nasal therapy in the acute and chronic setting: A narrative review

Chronic lung disease and admissions due to acute respiratory failure (ARF) are becoming increasingly common. Consequently, there is a growing focus on optimizing respiratory support, particularly non-invasive respiratory support, to manage these conditions. High flow nasal therapy (HFNT) is a noninvasive technique where humidified and heated gas is delivered through the nose to the airways via small dedicated nasal prongs at flows that are higher than the rates usually applied during conventional oxygen therapy. HFNT enables to deliver different inspired oxygen fractions ranging from 0.21 to 1. Despite having only recently become available, the use of HFNT in the adult population is quite widespread in several clinical settings. The respiratory effects of HNFT in patients with respiratory failure may be particularly relevant for clinicians. In this narrative review, we discuss the main pathophysiological mechanism and rationale for using HFNT in the acute and chronic setting.