[Value of modified ROX index in predicting the outcome of patients with acute respiratory distress syndrome due to SARS-CoV-2 infection treated with high-flow nasal cannula oxygen therapy].

Objective: To investigate the value of the modified ROX (mROX) index in predicting the outcome of patients with acute respiratory distress syndrome (ARDS) due to SARS-CoV-2 infection treated with high-flow nasal cannula oxygen therapy (HFNC).

Methods: A retrospective observational study was conducted, including 57 patients with ARDS caused by SARS-CoV-2 infection who required HFNC treatment in the intensive care unit (ICU) of the Lanzhou University Second Hospital from December 2022 to June 2023. The patients were divided into HFNC failure group and HFNC success group according to whether they were successfully weaned from HFNC. Laboratory tests, acute physiology and chronic health evaluation II (APACHE II), and sequential organ failure assessment (SOFA) in the first 24 hours of ICU admission were recorded in both groups, vital signs and arterial blood gas analysis immediately and after 6 hours of HFNC treatment, treatment regimen, length of ICU stay, and total length of hospital stay were recorded in both groups, and patients' outcomes at 28 days and 90 days were followed up by telephone. Univariate analysis was used to analyze the above indexes, and the significant indexes were included in the binary multivariate Logistic regression analysis to analyze the influencing factors of HFNC failure in patients. Kaplan-Meier survival curves were plotted to analyze the 28-day and 90-day outcomes of patients in both groups. Receiver operator characteristic curve (ROC curve) was plotted to analyze the value of treatment 6-hour mROX index and 6-hour ROX index in predicting the success of HFNC.

Results: A total of 57 patients with ARDS due to SARS-CoV-2 infection were enrolled, including 34 patients in the HFNC success group and 23 patients in the HFNC failure group. Procalcitonin (PCT), C-reactive protein (CRP), interleukin-6 (IL-6), lactic acid (Lac) and the proportion of vasopressors, the proportion of continuous renal replacement therapy (CRRT), the APACHE II score and the SOFA score, the respiratory rate (RR) immediately and 6 hours after treatment were significantly higher in the HFNC failure group compared with the HFNC success group. The length of ICU stay was significantly longer, and oxygenation index (PaO₂/FiO₂) at the time of treatment, and pulse oxygen saturation (SpO₂), arterial partial pressure of oxygen (PaO₂), ROX index, and mROX index at the time of treatment and at 6 hours after treatment were significantly lower in the HFNC failure group compared with the HFNC success group (all P < 0.05). Kaplan-Meier survival curves showed that the 28-day cumulative survival rates (100% vs. 26.1%) and 90-day cumulative survival rates (85.3% vs. 21.7%) of patients in the HFNC success group were significantly higher than those in the HFNC failure group (both P < 0.001). On binary multivariate Logistic regression analysis, Lac [odds ratio (OR) = 0.129, 95% confidence interval (95%CI) was 0.020-0.824], SOFA score (OR = 0.382, 95%CI was 0.158-0.925), 6-hour ROX index (OR = 0.099, 95%CI was 0.011-0.920), and 6-hour mROX index (OR = 23.703, 95%CI was 1.415-396.947) were associated with HFNC treatment outcome (all P < 0.05). ROC curve analysis showed that the area under the ROC curve (AUC) of the 6-hour mROX index and the 6-hour ROX index for predicting the success of HFNC were both higher (0.809 and 0.714, respectively), and the AUC of 6-hour mROX index was significantly higher than that of 6-hour ROX index (P < 0.01), and the sensitivity was 88.2% and the specificity was 52.2% when the cut-off value of 6-hour mROX index was 4.5.

Conclusions: The predictive value of the 6-hour mROX index in the treatment of patients with ARDS caused by SARS-CoV-2 infection is higher than that of the 6-hour ROX index, and the 6-hour mROX index is greater than 4.5, which is more likely to predict the success of HFNC treatment.