Association between ROX index with 28-day mortality in sepsis: A retrospective cohort study

Abstract

Abstract Background: The ROX index (peripheral oxygen saturation / fraction of inspired oxygen to respiratory rate) can help clinicians assessing patients' conditions. The purpose of this study was to evaluate the effects of time-weighted average ROX (ROX-TWA) index on short-term mortality in sepsis patients. Methods: In this retrospective study, clinical data of patients diagnosed as sepsis was extracted from the Medical Information Mart for Intensive Care (MIMIC)-III database (version 1.4). The septic patients were further categorized by quartiles of their ROX-TWA levels. The associations between ROX-TWA levels and 28-day mortality were assessed using multivariable Cox proportional hazards model and verified by two-piecewise linear regression model. Main results: By smooth curve fitting, we find that a non-linear relationship between ROX-TWA index and 28-day mortality in sepsis patients, and inflection point was 8. The risk of developing mortality decreased significantly with an increase in ROX-TWA value until plateaued at a level of 8 (HR 0.75 (0.71, 0.80), P<0.001). Moreover. Subgroup analysis showed, a similar relationship between ROX-TWA index and 28-day mortality in patients using or not using mechanical ventilator. Conclusion: The relationship between ROX-TWA index and 28-day mortality in sepsis patients is non-linear. ROX-TWA index is an independent risk factor of 28-day mortality in sepsis patients when ROX-TWA is less than 8.