Abstract
BACKGROUND: Volume OXygenation (VOX) index has good efficacy in predicting the failure of high-flow nasal cannula therapy. However, its predictive value for treatment failure in patients receiving noninvasive ventilation (NIV) remains uncertain. METHODS: Patients who underwent early NIV treatment were grouped based on their 2-h NIV VOX Youden index. The low-risk group consisted of patients with a VOX value > 20.45 (n = 188), while the high-risk group included those with a VOX value ≤ 20.45 (n = 200). Baseline data and arterial blood gas values were collected at 2, 12, and 24 h after NIV initiation. RESULTS: Compared to the low-risk group, the high-risk group exhibited higher SOFA scores, respiratory rates, and heart rates, along with a lower oxygenation index (P/F) (all p < 0.05). Following NIV treatment, the low-risk group showed a more significant increase in P/F values at 2 h, 12 h, and 24 h after NIV initiation. The low-risk group showed a lower VT and MV (minute ventilation volume) at 2 h, 12 h, and 24 h of NIV (p < 0.05). Moreover, the low-risk group had a lower intubation rate (7.98% vs. 77%, p < 0.05) and mortality rate (4.79% vs. 17.5%, p < 0.05). At 2 h of NIV, the area under the receiver operating characteristic curve for predicting NIV failure using the VOX index was 0.843 (95% CI 0.805-0.882). Using a VOX value threshold of 20.45 to predict NIV failure, the sensitivity was 69.1%, and the specificity was 94.4%. Furthermore, a VOX value ≤ 20.45 was identified as an independent risk factor for tracheal intubation and death. CONCLUSIONS: VOX index shows promise to serve as an effective evaluation index to predict early NIV efficacy in patients with AHRF; a VOX value > 20.45 after 2 h of NIV treatment can better predict improvements in hypoxia, respiratory drive, and NIV outcomes, guide early tracheal intubation in cases of NIV failure, and have a certain predictive effect on patient outcomes.