• Elizabeth McLellan, Karen Lam, Elizabeth Behringer, Vincent Chan, Didem Bozak, Nicholas Mitsakakis, and Anahi Perlas.
• Department of Anesthesia and Pain Management, Toronto Western Hospital, University Health Network, Toronto, ON, Canada; Royal Brisbane and Women's Hospital, Brisbane, Australia.
• Br J Anaesth. 2020 Jul 1; 125 (1): e75-e80.

BackgroundHigh-flow, heated, and humidified nasal oxygen therapy (HFNO) is frequently used in critical care and perioperative settings for a range of clinical applications. Much of the benefit of HFNO is attributed to generation of modest levels of positive airway pressure. Concern has been raised that this positive airway pressure may cause gastric insufflation, potentially increasing the risk of regurgitation and aspiration in an unprotected airway.MethodsA prospective, interventional, assessor-blinded study was undertaken to evaluate the effects of HFNO on gastric content and gastric distension in healthy fasted adult volunteers assessed by ultrasonography. The primary outcome was the volume of gastric secretions. The secondary outcomes were the incidence of gastric air insufflation and the distribution of gastric antral grades.ResultsSixty subjects were enrolled. No subject was found to have air gastric distension either at baseline or after treatment with HFNO. All subjects had either a Grade 0 or Grade 1 antrum, with similar distribution of antral grades and similar volume of gastric secretions before and after treatment with HFNO.ConclusionsThere was no evidence that treatment with HFNO at flow rates of up to 70 L min-1 for 30 min resulted in gastric distension or an increase in gastric secretions in healthy individuals breathing spontaneously. The generalisability of these findings to subjects under anaesthesia and patients with incompetence of the lower oesophageal sphincter or impaired gastric emptying requires further investigation.Clinical Trial RegistrationNCT03134937.Copyright © 2020 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.

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