High Flow Nasal Oxygen (HFNO), swallowing and dysphagia in adults: A narrative review with implications for ICU clinical practice and future research.

The use of high flow nasal oxygen (HFNO) in clinical practice is increasing with robust evidence of its respiratory benefits. Swallowing is known to be heavily coordinated with breathing, in addition to sharing a physical pathway in the upper airway. Applying HFNO via these spaces may also have an impact on the swallowing process. Yet, there is a lack of literature regarding the effect of HFNO on swallowing and on dysphagia. This narrative review aims to summarise the existing literature, draw conclusions on important clinical questions where possible and set the scene for future research. A database search was conducted on 24/01/2024 across CINAHL, Medline and Embase. Due to paucity of literature, studies with adult participants within and outside of ICU were included, and references cross-checked. Conference abstracts were also included. The search was repeated on 5/6/2024. Twelve articles were included in direct data comparison, in addition to studies examining the biomedical effect of HFNO that is, the impact of HFNO on the physiology of the oropharynx and swallow function. The authors conclude that whilst studies are limited in numbers and some results controversial, indications are that HFNO may demand adaptations to swallowing and some patients may not have this capability to adapt. HFNO should not be a barrier to a swallow assessment, irrespective of flow rate and the decision to assess should be based on overall patient presentation, as with any other population. Instrumental swallowing assessment is recommended to confirm any detrimental or beneficial impact of HFNO on swallow function. Robust research and guidelines are needed.