• Sarah Lee, W Pierre L Bradley, David J Brewster, Rani Chahal, Laurence Poon, Reny Segal, Savas Totonidis, David Tsang, and Mark Ng.
• Department of Anaesthesia, Pain and Perioperative Medicine, 1891Box Hill Hospital, Box Hill Hospital, Melbourne, Australia.
• Anaesth Intensive Care. 2021 Jul 1; 49 (4): 268-274.

AbstractThe use of high flow nasal oxygen in the care of COVID-19-positive adult patients remains an area of contention. Early guidelines have discouraged the use of high flow nasal oxygen therapy in this setting due to the risk of viral spread to healthcare workers. However, there is the need to balance the relative risks of increased aerosol generation and virus transmission to healthcare workers against the role high flow nasal oxygen has in reducing hypoxaemia when managing the airway in high-risk patients during intubation or sedation procedures. The authors of this article undertook a narrative review to present results from several recent papers. Surrogate outcome studies suggest that the risk of high flow nasal oxygen in dispersing aerosol-sized particles is probably not as great as first perceived. Smoke laser-visualisation experiments and particle counter studies suggest that the generation and dispersion of bio-aerosols via high flow nasal oxygen with flow rates up to 60 l/min is similar to standard oxygen therapies. The risk appears to be similar to oxygen supplementation via a Hudson mask at 15 l/min and significantly less than low flow nasal prong oxygen 1-5 l/min, nasal continuous positive airway pressure with ill-fitting masks, bilevel positive airway pressure, or from a coughing patient. However, given the limited safety data, we recommend a cautious approach. For intubation in the COVID-positive or suspected COVID-positive patient we support the use of high flow nasal oxygen to extend time to desaturation in the at-risk groups, which include the morbidly obese, those with predicted difficult airways and patients with significant hypoxaemia, ensuring well-fitted high flow nasal oxygen prongs with staff wearing full personal protective equipment. For sedation cases, we support the use of high flow nasal oxygen when there is an elevated risk of hypoxaemia (e.g. bariatric endoscopy or prone-positioned procedures), but recommend securing the airway with a cuffed endotracheal tube for the longer duration procedures when theatre staff remain in close proximity to the upper airway, or considering the use of a surgical mask to reduce the risk of exhaled particle dispersion.

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