Delta ROX index as a dynamic predictor of respiratory exacerbation in acute cervical spinal cord injury: A retrospective study.

Abstract

Respiratory complications following cervical spinal cord injury (CSCI) are a major cause of morbidity and mortality. Although several risk factors have been identified, quantitative predictors for respiratory deterioration are limited. The respiratory rate-oxygenation (ROX) index, defined as the ratio of oxygen saturation (SpO2)/fraction of inspired oxygen (FiO2) to respiratory rate, has been validated for predicting outcomes in respiratory failure. Because the ROX index is a quantitative indicator that sensitively reflects temporal changes in respiratory status, we hypothesized that variations in the ROX index (delta ROX) could serve as a predictor of respiratory exacerbation (RE) in patients with CSCI. This study aimed to evaluate the association between delta ROX and RE in patients with CSCI. A single-center, retrospective observational study was conducted at a major trauma center in Japan between 2012 and 2023. Adult patients (aged ≥18 years) admitted to the intensive care unit (ICU) with traumatic CSCI were eligible. The primary outcome was RE requiring intubation within 7 days. The ROX index was calculated at each time point (2, 6, 12, 18, and 24 h after admission). The delta ROX index was defined as the ratio of the ROX index at each time point to the ROX index at ICU admission. Among 54 eligible patients, 7 (13%) developed RE. The delta ROX index showed significant differences between the RE and control groups at 12 (0.69 vs. 1.27, p = 0.016), 18 (0.81 vs. 1.29, p = 0.005), and 24 h (0.73 vs. 1.33, p = 0.004). Receiver operating characteristic analysis demonstrated the highest predictive value at 24 h (area under the curve 0.94, 95% CI 0.87-1.00). The delta ROX index may serve as a valuable predictor of RE in patients with CSCI. A decreasing trend in the ROX index during the first 24 h of ICU admission was associated with an increased risk of respiratory deterioration, potentially enabling earlier respiratory intervention. These findings suggest that the delta ROX index provides a dynamic, quantitative measure that may help identify patients at increased risk.