• Arnav Agarwal, John Basmaji, Fiona Muttalib, David Granton, Dipayan Chaudhuri, Devin Chetan, Malini Hu, Shannon M Fernando, Kimia Honarmand, Layla Bakaa, Sonia Brar, Bram Rochwerg, Neill K Adhikari, Francois Lamontagne, Srinivas Murthy, HuiDavid S CDSCDepartment of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, Hong Kong, SAR, China.Stanley Ho, Center for Emerging Infectious Diseases, The Chinese University of Hong Kong, Shatin, Hong Kong, SAR, China., Charles Gomersall, Samira Mubareka, Janet V Diaz, BurnsKaren E AKEAUnity Health Toronto - St. Michael's Hospital, Toronto, ON, Canada.University of Toronto, Toronto, ON, Canada.Li Ka Shing Knowledge Institute, Toronto, ON, Canada., Rachel Couban, Quazi Ibrahim, Gordon H Guyatt, and Per O Vandvik.
• Department of Medicine, University of Toronto, Toronto, ON, Canada.
• Can J Anaesth. 2020 Sep 1; 67 (9): 121712481217-1248.

PurposeWe conducted two World Health Organization-commissioned reviews to inform use of high-flow nasal cannula (HFNC) in patients with coronavirus disease (COVID-19). We synthesized the evidence regarding efficacy and safety (review 1), as well as risks of droplet dispersion, aerosol generation, and associated transmission (review 2) of viral products.SourceLiterature searches were performed in Ovid MEDLINE, Embase, Web of Science, Chinese databases, and medRxiv. Review 1: we synthesized results from randomized-controlled trials (RCTs) comparing HFNC to conventional oxygen therapy (COT) in critically ill patients with acute hypoxemic respiratory failure. Review 2: we narratively summarized findings from studies evaluating droplet dispersion, aerosol generation, or infection transmission associated with HFNC. For both reviews, paired reviewers independently conducted screening, data extraction, and risk of bias assessment. We evaluated certainty of evidence using GRADE methodology.Principal FindingsNo eligible studies included COVID-19 patients. Review 1: 12 RCTs (n = 1,989 patients) provided low-certainty evidence that HFNC may reduce invasive ventilation (relative risk [RR], 0.85; 95% confidence interval [CI], 0.74 to 0.99) and escalation of oxygen therapy (RR, 0.71; 95% CI, 0.51 to 0.98) in patients with respiratory failure. Results provided no support for differences in mortality (moderate certainty), or in-hospital or intensive care length of stay (moderate and low certainty, respectively). Review 2: four studies evaluating droplet dispersion and three evaluating aerosol generation and dispersion provided very low certainty evidence. Two simulation studies and a crossover study showed mixed findings regarding the effect of HFNC on droplet dispersion. Although two simulation studies reported no associated increase in aerosol dispersion, one reported that higher flow rates were associated with increased regions of aerosol density.ConclusionsHigh-flow nasal cannula may reduce the need for invasive ventilation and escalation of therapy compared with COT in COVID-19 patients with acute hypoxemic respiratory failure. This benefit must be balanced against the unknown risk of airborne transmission.

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