The use of the high-flow nasal cannula (HFNC) for oxygen therapy in patients with acute hypoxemic respiratory failure has increased dramatically in recent years, owing to the numerous advantages it has over the other modalities. The respiratory rate-oxygenation (ROX) index was created as a monitoring tool for the appropriate use of the HFNC. It is gaining popularity as a critical monitoring tool due to its non-invasive nature and the ability to be performed at the bedside. To write this review we searched for the original peer-reviewed journal articles using search engines such as Cochrane Library, Google Scholar, and PubMed for evidence of the utility of this index in clinical practice. Despite having many advantages as well as limitations, the ROX index has been shown to have a moderate but useful predictive value/capacity and diagnostic accuracy in detecting HFNC-assisted oxygen therapy failure or success. Further high-quality prospective studies and trials might bring more clarity regarding performance under variable flow rates of HFNC, the acquisition time intervals, cut-off value/limit, and standardization of the index. The ROX index being a non-invasive, simple, and bedside tool could prove a very promising tool to assess the effectiveness, progress and outcome of the HFNC therapy.

Acute hypoxemic respiratory failure

COVID-19

High-flow nasal cannula

ROX index

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