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

Abstract

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.

COVID-19 pneumonia: pathophysiology and management

“…Another obvious advantage of HFNC is its ability to deliver gas flows that match the patient's mean inspiratory flow generated with high respiratory drive, therefore making it possible to supply oxygen at the set F IO 2 [ 73 ]. The additional advantages of dead space washout, air warming and humidification can reduce airway resistance and further decrease respiratory effort [ 74 ]. It is important to note, though, that the use of HFNC during the pandemic has been highly variable and influenced by three main factors: 1) inconsistent advice from different societies and guidelines, some of which discouraged the use of HFNC; 2) concerns regarding the high oxygen demand of these devices, potentially leading to exhaustion of the hospital's supply of oxygen; and 3) risk of viral spreading.…”

The utility of high-flow nasal oxygen for severe COVID-19 pneumonia in a resource-constrained setting: A multi-centre prospective observational study

“…High-flow nasal oxygen (HFNO) is delivered by an air/oxygen blender, an active humidifier, a single heated circuit, and a nasal interface. It delivers adequately heated and humidified medical gas at flow-rates of up to 60 L/min, and is considered to have a number of physiological benefits, including the reduction of anatomical dead space and work of breathing, the provision of a constant fraction of inspired oxygen with adequate humidification and a degree of positive end-expiratory pressure (PEEP) [ 5 , 6 ]. Although HFNO was originally utilised in neonatology, its use has extended to adult critical care [6] .…”

High-flow nasal oxygen therapy in the treatment of acute respiratory failure in severe COVID-19 pneumonia: a prospective observational study

“…The HFNO therapy involves delivery of oxygenated gas, heated and humidified to body conditions, via a nasal cannula at a maximum flow up to 80 l/min. [7,8] The therapy is believed to have numerous benefits, including adequate humidification, reduction of anatomical dead space and work of breathing, as well as an increase in end-expiratory lung volume thanks to the provision of positive end-expiratory pressure. During the past years, its use has extended in the critical care setting to the treatment of hypoxemic ARF after extubation and in the postoperative period in high-risk or obese patients.…”