Comparison of ROX, HROX, and delta-HR indices to predict successful weaning from high-flow oxygen therapy in hospitalized patients with COVID-19 pneumonia

Abstract

Background High-flow nasal cannula (HFNC) therapy is commonly used to treat acute respiratory failure in patients with COVID-19 pneumonia. However, predictors of successful weaning from HFNC in these patients has not been investigated. Objective To assess predictors of successful separation from HFNC in patients with COVID-19 pneumonia. Methods We conducted a retrospective cohort study at a university hospital in Thailand. Patients with COVID-19 pneumonia requiring HFNC therapy between April 2020 and June 2022 were included. ROX index was defined as the ratio of oxygen saturation (SpO2) / fraction of inspired oxygen (FiO2) to respiratory rate. Heart-ROX (HROX) index was defined as ROX multiplied by heart rate (HR) improvement. HR improvement (delta-HR) was defined as a percentage of the difference between the baseline HR and the morning HR at HFNC weaning day 1 divided by the baseline HR. Weaning success was defined as ability to sustain spontaneous breathing after separation from HFNC without any invasive or non-invasive ventilatory support for ≥48 hours or death. Results A total of 164 patients (54% male) were included. Mean age was 61.1±16.1 years. Baseline SpO2/FiO2 was 265.3±110.8. HFNC weaning success was 77.4%. The best cut-off value of ROX index to predict HFNC weaning success was 7.88 with 100% sensitivity, 97.3% specificity, and area under the ROC curve (AUC) of 0.98 (95% CI: 0.937–1.000, p<0.001). The best cut-off value of delta-HR 3.7 with 88.2% sensitivity, 75.7% specificity, and AUC of 0.83 (95% CI: 0.748–0.919, p<0.001). The best cut-off value of HROX index was 59.2 with 88.2% sensitivity, 81.1% specificity, and AUC of 0.89, (95% CI: 0.835–0.953, p<0.001). Conclusions The ROX index has the highest accuracy for predicting successful weaning off HFNC treatment in patients with COVID-19 pneumonia. While HROX and delta-HR indices can serve as alternative tools, it is recommended to verify these indices and determine the optimal cutoff value for determining separation from HFNC therapy through a large prospective cohort study.