LAUSR

DMOX, which reflects the change of respiratory drive after HFNC, was able to distinguish HFNC failure only at 6 hours but not at 2 hours after HFNC. The AUROCwas 0.59 at 2 hours and 0.79 at 6 hours. The sensitivity and specificity were 58.6% and 93.9% at 6 hours after HFNC, respectively. However, the AUROC of VOX index, which reflects the absolute increase of respiratory drive, was much higher (0.93) at 6 hours after HFNC. On the other hand, more severe patients enrolled in our study, compared with the study by Li and colleagues (3), might be the main reason for the poor predictive value of DMOX after a short time of HFNC (2 h). Compared with the report by Li and colleagues, a higher acute physiologic assessment and chronic health evaluation II score (21 vs. 18) and a higher intubation rate (46.7% vs. 22.9%) were observed in patients in our study. Therefore, as the use of a change of MV does not provide any additional benefit in terms of prediction of HFNC failure, the use of the normal VOX index may be recommended.