The value of ROX index in evaluating the efficacy of high-flow nasal cannula oxygen therapy in patients with COVID-19

Objective: To assess the value of the ROX index in evaluating the efficacy of highflow nasal cannula oxygen therapy (HFNC) in patients with coronavirus infected disease (COVID-19). Methods: This is a retrospective study. The included patients were diagnosed as COVID-19 in the intensive care unit (ICU) of the Cancer Center of Union Hospital affiliated to Tongji Medical College of Huazhong University of Science and Technology from February 15, 2020 to March 15, 2020. All the patients were treated by HFNC. According to whether the patient subsequently received non-invasive positive pressure ventilation or invasive positive pressure ventilation, patients were divided into the HFNC success group and the HFNC failure group. Parameters in the two groups such as basic characteristics, lactic acid, number of chest radiographs, APACHE II, lymphocyte count, baseline respiratory rate, baseline percutaneous oxygen saturation, baseline PaO2/FiO2, baseline ROX index, and ROX index after 2, 6 and 12 h HFNC treatment were analyzed with t test, Chi-square test or rank sum test. Results: A total of 57 cases were included in this study. There were no significant differences in sex, age, comorbidities, lactic acid, quadrants of chest radiograph lung infection, APACHE II, lymphocyte count, and baseline respiratory frequency, transcutaneous oxygen saturation, oxygenation index, and ROX index between the HFNC success group and the HFNC faliure group (P>0.05). Logistic regression analysis showed that ROX index after 2 h HFNC treatment (OR=0.069), ROX index after 6 h HFNC treatment (OR=0.194) and ROX index after 12 h HFNC treatment (OR=0.036) were all protective factors for the therapeutic effect of HFNC treatment in COVID-19 patients. ROC curve showed that there were significant differences in ROX index after 2 h HFNC treatment, ROX index after 6 h HFNC treatment, and ROX index after 12 h HFNC treatment (P<0.05). In the evaluation index, the area under the ROC curve of the ROX index after 2 h HFNC treatment was 0.838, the sensitivity was 64.5%, and the specificity was 100%. After 6 h HFNC treatment, the area under the ROX index ROC curve was 0.762, the sensitivity was 64.5%, and the specificity was 92.3%. After 12 h HFNC treatment, the ROX index ROC curve area was 0.866, the sensitivity was 67.7%, and the specificity was 100%. Conclusions: The ROX index can be used to evaluate the efficacy of HFNC in COVID-19 patients in a timely, simple and real-time manner. © 2021 Chinese Medical Association. All rights reserved.