The following is a summary of “Respiratory rate‑oxygenation (ROX) index for predicting high-flow nasal cannula failure in patients with and without COVID-19,” published in the January 2024 issue of Emergency Medicine by Kwon, et al.

The utility of the respiratory rate-oxygenation (ROX) index in predicting high-flow nasal cannula (HFNC) failure among patients with COVID-19 and acute hypoxemic respiratory failure (AHRF) may differ from that of those without COVID-19, yet such a comparison remains unexplored. For a study, researchers sought to assess the diagnostic accuracy of the ROX index for HFNC failure in patients with and without COVID-19 during acute emergency department (ED) visits.

A retrospective analysis was conducted on patients with AHRF receiving HFNC therapy in the ED between October 2020 and April 2022. The ROX index was calculated at various time points post-HFNC placement. HFNC failure, defined as subsequent intubation or death within 72 hours, was the primary outcome. Receiver operating characteristic (ROC) curves were used to evaluate the discriminative power of the ROX index for HFNC failure.

Among 448 patients with AHRF treated with HFNC in the ED, 78 (17.4%) had COVID-19. HFNC failure rates did not significantly differ between the non-COVID-19 and COVID-19 groups (29.5% vs. 33.3%, P = 0.498). The median ROX index was consistently higher in the non-COVID-19 group compared to the COVID-19 group at all time points. The prognostic accuracy of the ROX index for HFNC failure, assessed by the area under the ROC curve, was generally higher in the COVID-19 group (0.73–0.83) than in the non-COVID-19 group (0.62–0.75). The optimal timing for the highest prognostic value of the ROX index for HFNC failure was at 4 hours for the non-COVID-19 group, while in the COVID-19 group, its performance remained consistent from 1 to 6 hours. The optimal cutoff values were 6.48 and 5.79 for the non-COVID-19 and COVID-19 groups.

The ROX index demonstrated acceptable discriminative power for predicting HFNC failure in patients with AHRF, regardless of COVID-19 status in the ED. However, the higher ROX index thresholds compared to prior studies involving intensive care unit (ICU) patients underscore the importance of vigilant monitoring and establishing new thresholds for non-ICU admitted patients.

Reference: sciencedirect.com/science/article/abs/pii/S0735675723005107