Nasal high flow: physiology, efficacy and safety in the acute care setting, a narrative review

Tommaso Mauri,1,2 Yu-Mei Wang,3 Francesca Dalla Corte,4 Nadia Corcione,1 Elena Spinelli,1 Antonio Pesenti1,21Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, University of Milan, Milan, Italy; 2Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy; 3Department of Critical Care Medicine, Beijing Tiantan Hospital, Capital Medical University, Beijing, People’s Republic of China; 4Department of Morphology, Surgery and Experimental Medicine, Azienda Ospedaliera-Universitaria Arcispedale Sant’Anna, University of Ferrara, Ferrara, ItalyAbstract: Nasal high flow (NHF) is a promising novel oxygen delivery device, whose mechanisms of action offer some beneficial effects over conventional oxygen systems. It is considered to have a number of physiological effects: it improves oxygenation, dynamic lung compliance, homogeneity and end expiratory lung volume; it decreases anatomical dead space and generates a positive airway pressure that can reduce respiratory rate, the work of breathing, and enhance patient comfort. NHF has been used as a prophylactic tool or as a treatment device mostly in patients with acute hypoxemic respiratory failure such as pre-oxygenation before intubation, immunocompromised patients and acute heart failure. Moreover, there is some evidence that NHF could be used during procedural sedation. Finally, NHF was deemed to be effective in chronic obstructive pulmonary disease patients with its positive end expiratory pressure effects and dead-space washout. However, careful monitoring is crucial to maximize NHF settings aimed at maximizing patient comfort while limiting the risk of delayed intubation. The present review presents the most updated evidence for NHF use in the adult acute care setting with the goal of providing clinicians with useful insights on the physiologic effects, main clinical indications, and safety issues of NHF treatment.Keywords: nasal high flow, physiological effects, positive end-expiratory, acute respiratory failure, oxygenation therap