RESUMEN
BACKGROUND: [Formula: see text] may be a reliable noninvasive alternative to the [Formula: see text] index. Furthermore, the ROX index (ie, the ratio of [Formula: see text] to breathing frequency) has been validated to predict high-flow nasal cannula failure in subjects under spontaneous breathing. However, these indices have not been tested in subjects with COVID-19 receiving invasive mechanical ventilation. This study aims to verify the correlation between both the ROX index and [Formula: see text] with [Formula: see text] and the ratio of [Formula: see text] to breathing frequency, and to determine the accuracy of the indices that use [Formula: see text] for the prediction of extubation failure in subjects with COVID-19. METHODS: A prospective cohort study was conducted from May 15, 2020, to June 15, 2020, with subjects with COVID-19 on invasive mechanical ventilation. Indices using [Formula: see text] in the formula were compared to those using [Formula: see text]. Additionally, the performance of the indices in predicting extubation failure was evaluated. RESULTS: This study included 69 subjects age 64.8 ± 14.6 y. There were no differences between the median values of the indices, including between the ROX index and [Formula: see text] to breathing frequency (P = .40) or between [Formula: see text] and [Formula: see text] (P = .83). When comparing the ROX index with the [Formula: see text] index to breathing frequency, they were found to be strongly correlated (R2 = 0.75 [95% CI 0.6763-0.8152], P < .001). The comparison of [Formula: see text] with [Formula: see text] revealed R2 = 0.70 (95% CI 0.563-0.749, P < .001). The area under the receiver operating characteristic curve for the ROX index to determine extubation failure was 0.74 (P = .01), whereas for [Formula: see text] it was 0.78 (P < .001). CONCLUSIONS: The indices presented a good correlation in subjects with COVID-19 on invasive mechanical ventilation, and both the ROX index and [Formula: see text] can discriminate extubation failure in this population.
