de Andrade Filho PH, de Assis Brasil ES, Costa LG, et al. - Studies have described a possible value of SpO2/ FiO2 as a reliable noninvasive alternative to the PaO2/FiO2 index and the predictive value of the ROX index (ie, the ratio of SpO2/FiO2 to breathing frequency) for high-flow nasal cannula failure in individuals under spontaneous breathing. A prospective cohort study of individuals with COVID-19 on invasive mechanical ventilation was performed with the aim to verify the association between both the ROX index and SpO2/FiO2 with PaO2/FiO2 and the ratio of PaO2/FiO2 to breathing frequency, as well as to examine the accuracy of the indices that use SpO2 for the prediction of extubation failure in individuals with COVID-19. A total of 69 individuals aged 64.8 ± 14.6 y were included. Findings revealed good correlation of the indices in individuals with COVID-19 on invasive mechanical ventilation, and both the ROX index and SpO2/FiO2 can distinguish extubation failure in this population.