Prediction of Extubation Failure in COVID-19

BACKGROUND: S-pO2/F-IO2 may be a reliable noninvasive alternative to the P-aO2/F-IO2 index. Furthermore, the ROX index (ie, the ratio of S-pO2/F-IO2 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 S-pO2/F-IO2 with P-aO2/F-IO2 and the ratio of P-aO2/F-IO2 to breathing frequency, and to determine the accuracy of the indices that use S-pO2 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 S-pO2 in the formula were compared to those using P-aO2. 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 P-aO2/F-IO2 to breathing frequency (P = .40) or between P-aO2/F-IO2 and S-pO2/F-IO2 (P = .83). When comparing the ROX index with the P-aO2/F-IO2 index to breathing frequency, they were found to be strongly correlated (R-2 = 0.75 [95% CI 0.6763-0.8152], P < .001). The comparison of P-aO2/F-IO2 with S-pO2/F-IO2 revealed R-2 = 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 S-pO2/F-IO2 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 S-pO2/F-IO2 can discriminate extubation failure in this population.