Comparison of ROX index (SpO(2)/FIO(2) ratio/respiratory rate) with a modified dynamic index incorporating PaO(2)/FIO(2) ratio and heart rate to predict high flow nasal cannula outcomes among patients with acute respiratory failure: a single centre retros

High flow nasal cannula (HFNC) is increasingly being used to support patients with acute respiratory failure (ARF) and to avoid need for intubation. However, almost one third of the patients do not respond and require escalation of respiratory support. Previously, ROX index (SpO2/FIO2 [SF] ratio/respiratory rate) has been validated among pneumonia patients to facilitate early recognition of patients likely to fail HFNC and therefore, benefit from timely interventions. However, it has been postulated that incorporation of PaO2/FIO2 (PF) ratio from arterial blood gas (ABG) analysis may better predict the outcome of HFNC compared to indices that utilizes SF ratio. Similarly, heart rate increase after HFNC therapy initiation has been found to be associated with HFNC failure. Therefore, we aimed to compare ROX index with a new modified index to predict HFNC outcomes among ARF patients. This single centre 2-year retrospective study included ARF patients of varying etiologies treated with HFNC. The modified index incorporated heart rate and substituted PF ratio for SF ratio in addition to respiratory rate. We named the index POX-HR and calculated Delta POX-HR index as the difference pre- and post-HFNC initiation POX-HR. We also recorded ROX index at the time when post-HFNC initiation ABG was done ('post-HFNC initiation ROX') and calculated Delta ROX. HFNC success was defined as no need of escalation of respiratory support or discharged to ward within 48 h of HFNC initiation, or successful wean off HFNC for at least 12 h. Evaluation was performed using area under the receiver operating characteristic curve (AUROC) and cut-offs assessed for prediction of HFNC outcomes. One hundred eleven patients were initiated on HFNC for ARF, of whom 72 patients (64.9%) had HFNC success. Patients with HFNC failure had significantly lower values for all the indices. At median of 3.33 h (IQR 1.48-7.24 h), Delta POX-HR demonstrated the best prediction accuracy (AUROC 0.813, 95% CI 0.726-0.900). A Delta POX-HR > 0.1 was significantly associated with a lower risk of HFNC failure. Our proposed modified dynamic index (Delta POX-HR) may facilitate early and accurate prediction of HFNC outcomes compared to ROX index among ARF patients of varied etiologies.

Kansal A ，Ong WJD ，Dhanvijay S ，Siosana ATP ，Padillo LM ，Tan CK ，Gulati Kansal M ，Khan FA ... -  《BMC Pulmonary Medicine》

ROX index and SpO2/FiO2 ratio for predicting high-flow nasal cannula failure in hypoxemic COVID-19 patients: A multicenter retrospective study.

Kim JH ，Baek AR ，Lee SI ，Kim WY ，Na YS ，Lee BY ，Seong GM ，Baek MS ... -  《PLoS One》

The use of respiratory rate-oxygenation index to predict failure of high-flow nasal cannula in patients with coronavirus disease 2019-associated acute respiratory distress syndrome: A retrospective study.

Patients with mild-to-moderate coronavirus disease 2019 (COVID-19)-associated acute respiratory distress syndrome (ARDS) can be treated with a high-flow nasal cannula (HFNC). The use of the respiratory rate-oxygenation (ROX) index, calculated as the ratio of oxygen saturation (SpO2)/fractional oxygen (FiO2) to respiratory rate, in the first few hours after HFNC initiation can help identify patients who fail HFNC therapy later. However, few studies have documented the use of the ROX index during the period of HFNC therapy. Therefore, we aimed to demonstrate the diagnostic performance of the ROX index when calculated throughout the HFNC therapy period and to determine the best cut-off point for predicting HFNC failure. We conducted a retrospective study of patients with COVID-19-associated ARDS who commenced HFNC at the Faculty of Medicine Vajira Hospital, Navamindradhiraj University, Thailand, between April 1 and August 30, 2021. We calculated the ROX index every 4 h throughout the HFNC therapy period and defined HFNC failure as a subsequent endotracheal tube intubation. The performance of the ROX index was analyzed using the area under the receiver operating characteristic curve (AUC). We applied the ROX index ≤ 4.88 to predict HFNC failure and obtained a new ROX cut-off point using Youden's method. In total, 212 patients with COVID-19 treated with HFNC were included in the study. Of these, 81 patients (38.2%) experienced HFNC failure. The ROX index ≤ 4.88 demonstrated a reasonable performance in predicting HFNC failure (AUC, 0.77; 95% confidence interval [CI], 0.72-0.83; p<0.001). However, compared with the original cut-off point of ≤ 4.88, the new ROX index cut-off point of ≤ 5.84 delivered optimal performance (AUC, 0.84; 95% CI, 0.79-0.88; p<0.001), with a significantly better discriminative ability (p = 0.007). In conclusion, a ROX index ≤ 5.84 was found to be optimal for predicting HFNC failure in patients with COVID-19-associated ARDS.

Poopipatpab S ，Nuchpramool P ，Phairatwet P ，Lertwattanachai T ，Trongtrakul K ... -  《PLoS One》

Prediction of high-flow nasal cannula outcomes at the early phase using the modified respiratory rate oxygenation index.

This study was designed to explore the early predictive value of the respiratory rate oxygenation (ROX) index modified by PaO2 (mROX) in high-flow nasal cannula (HFNC) therapy in patients with acute hypoxemia respiratory failure (AHRF). Seventy-five patients with AHRF treated with HFNC were retrospectively reviewed. Respiratory parameters at baseline and 2 h after HFNC initiation were analyzed. The predictive value of the ROX (ratio of pulse oximetry/FIO2 to respiratory rate) and mROX (ratio of arterial oxygen /FIO2 to respiratory rate) indices with two variations by adding heart rate to each index (ROX-HR and mROX-HR) was evaluated. HFNC therapy failed in 24 patients, who had significantly higher intensive care unit (ICU) mortality and longer ICU stay. Both the ROX and mROX indices at 2 h after HFNC initiation can predict the risk of intubation after HFNC. Two hours after HFNC initiation, the mROX index had a higher area under the receiver operating characteristic curve (AUROC) for predicting HFNC success than the ROX index. Besides, baseline mROX index of greater than 7.1 showed a specificity of 100% for HFNC success. The mROX index may be a suitable predictor of HFNC therapy outcomes at the early phase in patients with AHRF.

Li Z ，Chen C ，Tan Z ，Yao Y ，Xing S ，Li Y ，Gao Y ，Zhao Z ，Deng Y ，Zhu M ... -  《BMC Pulmonary Medicine》

Ratio of Oxygen Saturation to Inspired Oxygen, ROX Index, Modified ROX Index to Predict High Flow Cannula Success in COVID-19 Patients: Multicenter Validation Study.

Ruangsomboon O ，Jirathanavichai S ，Phanprasert N ，Puchongmart C ，Boonmee P ，Thirawattanasoot N ，Dorongthom T ，Monsomboon A ，Praphruetkit N ... -  《-》