Study on combining the ROX index and VOX index to predict the timing of tracheal intubation in patients with acute hypoxemic respiratory failure

doi:10.3969/j.issn.1674-490X.2026.05.002

Abstract

Abstract: Objective To investigate the predictive value of the ROX index(SpO₂/FiO₂/RR)combined with the VOX index(SpO₂/FiO₂/VT)for the timing of endotracheal intubation in patients with acute hypoxemic respiratory failure(AHRF). Methods A total of 107 patients with acute hypoxemic respiratory failure(AHRF)admitted to the Emergency Intensive Care Unit of the Affiliated Hospital of Hebei University from April 2024 to April 2026 were enrolled. Based on whether they received invasive mechanical ventilation via endotracheal intubation during hospitalization, the patients were divided into an intubation group(n=54)and a non-intubation group(n=53). General data of the two groups were compared, as well as the ROX index and VOX index—measured before intubation in the intubation group and the worst value during hospitalization in the non-intubation group. Multivariate logistic regression analysis was used to identify independent risk factors for endotracheal intubation in AHRF patients. Receiver operating characteristic(ROC)curves were employed to evaluate the predictive performance of the ROX index, the VOX index, and their combination, and the optimal cutoff values were determined.Results There were no statistically significant differences between the two groups in terms of sex, age, medical history, or admission levels of white blood cell count, hemoglobin, platelet count, and prothrombin time(P>0.05). Patients in the intubation group had higher alanine aminotransferase and respiratory rate(RR)than those in the non intubation group, while pulse oxygen saturation(SpO₂), arterial partial pressure of oxygen(PaO₂), arterial partial pressure of carbon dioxide(PaCO₂), oxygenation index(PaO₂/FiO₂), ROX index, and VOX index were lower in the intubation group(P<0.05). Multivariate logistic regression analysis showed that the ROX index(OR=0.672, 95%CI: 0.451-0.991, P<0.05)and the VOX index(OR=0.351, 95% CI: 0.150-0.906, P<0.05)were influencing factors for the need for endotracheal intubation in AHRF patients. ROC curve analysis revealed that the areas under the curve(AUC)for the ROX index, the VOX index, and their combination in predicting endotracheal intubation were 0.710, 0.800, and 0.900, respectively. The AUC of the combined model was significantly greater than that of either single index(P<0.05), and the optimal cutoff values were 3.752, 21.031, and 0.420, respectively. After internal validation by Bootstrap, the bias corrected AUC was 0.890, indicating good model stability.Conclusion The ROX index and VOX index are effective indicators for predicting the need for endotracheal intubation in patients with AHRF. Their combined use significantly improves predictive performance and helps clinicians more accurately determine the optimal timing for endotracheal intubation.

Key words: ROX index, VOX index, hypoxemic respiratory failure, endotracheal intubation

CLC Number:

Ju Hailong, Zhang Lingling, Li Jianqi, Zhang Hongqiang. Study on combining the ROX index and VOX index to predict the timing of tracheal intubation in patients with acute hypoxemic respiratory failure[J]. Journal of Hebei Medical College for Continuing Education, 2026, 43(5): 12-19.

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