A retrospective study has shown that the Volume OXygenation (VOX) index, assessed 2 hours after initiating non-invasive ventilation (NIV), can effectively predict treatment failure in patients with acute hypoxic respiratory failure (AHRF). A VOX value above 20.45 was associated with lower intubation and mortality rates, supporting its use as an early evaluation tool.
The study was conducted across three hospitals from September 2017 to September 2021. It included patients with AHRF who received early NIV therapy. Patients were classified into high-risk and low-risk groups based on the 2-hour VOX value and the Youden index threshold. The objective was to evaluate the VOX index's predictive performance for early identification of NIV failure.
At two hours of NIV treatment, VOX's area under the receiver operating characteristic (ROC) curve in predicting NIV failure was 0.843 (95% CI 0.805–0.882). A VOX threshold 20.45 yielded a sensitivity of 69.1% and a specificity of 94.4%. Patients in the low-risk group (VOX > 20.45) had a much lower intubation rate of 7.98% compared to 77% in the high-risk group (P < 0.05). Mortality was also significantly lower in the low-risk group (4.79% vs. 17.5%, P < 0.05).
These data support using the VOX index as a valuable early predictor of non-invasive ventilation failure in acute hypoxic respiratory failure. High specificity allows clinicians to distinguish patients likely to benefit from ongoing NIV, minimizing unnecessary escalation of care. A VOX reading above 20.45 after two hours signals low risk and may guide effective respiratory treatment decisions.
