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

Abstract

Background The ratio of oxygen saturation (ROX) index, defined as the ratio of oxygen saturation (SpO2)/fraction of inspired oxygen (FiO2) to respiratory rate, can help identify patients with hypoxemic respiratory failure at high risk for intubation following high-flow nasal cannula (HFNC) initiation; however, whether it is effective for predicting intubation in coronavirus disease 2019 (COVID-19) patients receiving HFNC remains unknown. Moreover, the SpO2/FiO2 ratio has been assessed as a prognostic marker for acute hypoxemic respiratory failure. This study aimed to determine the utility of the ROX index and the SpO2/FiO2 ratio as predictors of failure in COVID-19 patients who received HFNC. Methods This multicenter study was conducted in seven university-affiliated hospitals in Korea. Data of consecutive hospitalized patients diagnosed with COVID-19 between February 10, 2020 and February 28, 2021 were retrospectively reviewed. We calculated the ROX index and the SpO2/FiO2 ratio at 1 h, 4 h, and 12 h after HFNC initiation. The primary outcome was HFNC failure defined as the need for subsequent intubation despite HFNC application. The receiver operating characteristic curve analysis was used to evaluate discrimination of prediction models for HFNC failure. Results Of 1,565 hospitalized COVID-19 patients, 133 who received HFNC were analyzed. Among them, 63 patients (47.4%) were successfully weaned from HFNC, and 70 (52.6%) were intubated. Among patients with HFNC failure, 32 (45.7%) died. The SpO2/FiO2 ratio at 1 h after HFNC initiation was an important predictor of HFNC failure (AUC 0.762 [0.679–0.846]). The AUCs of SpO2/FiO2 ratio at 4 h and ROX indices at 1 h and 4 h were 0.733 (0.640–0.826), 0.697 (0.597–0.798), and 0.682 (0.583–0.781), respectively. Multivariable analysis showed that the patients aged ≥70 years are 3.4 times more likely to experience HFNC failure than those aged <70 years (HR 3.367 [1.358–8.349], p = 0.009). The SpO2/FiO2 ratio (HR 0.983 [0.972–0.994], p = 0.003) at 1 h was significantly associated with HFNC failure. Conclusions The SpO2/FiO2 ratio following HFNC initiation was an acceptable predictor of HFNC failure. The SpO2/FiO2 ratio may be a good prognostic marker for predicting intubation in COVID-9 patients receiving HFNC.

High flow nasal oxygen (HFNO) in the treatment of COVID-19 infection of adult patients from – An emergency perspective: A systematic review and meta-analysis

“…However, some studies have shown that SpO 2 /FiO 2 after HFNO initiation might be a good indicator of HFNO success in treating COVID-19 patients. Kim et al [ 18 ] reported that ROX index and SpO 2 /FiO 2 were acceptable predictors for HFNC failure among COVID-19 patients. Results of AUROC revealed that the ratio SpO 2 /FiO 2 at 1 and 4 hours were 0.762 (95% CI: 0.679–0.846) and 0.733 (95% CI: 0.640–0.826), respectively, signifying better prediction accuracy.…”

“… A significantly higher ROX index was recorded in the success group than the failure group (5.9 vs. 4.8, respectively.) Kim et al, 2022 [ 18 ] Multicenter retrospective Study 133 hypoxemic COVID-19 patients (79 males and 54 females) with a mean age of 70 years were analyzed HFNC oxygen therapy 12 HFNC success was observed in 63 patients, while failure was observed in 70 patients. Significantly higher ROX indices were observed in the success group than in the failure group (8.77 vs. 6.85, 9.33 vs. 7.67, 9.70 vs. 8.64 after 1, 4, and 12 hours, respectively.)…”

Persistent Hypoxemia and Biomarkers in Severe COVID-19 Pneumonia Patients Treated with Methylprednisolone

“…(40, 41) PaO 2 is derived from an arterial blood gas, gives only a "snapshot" of a patient's oxygen status, and requires direct patient contact. (41) This maybe an issue when patients are in isolation rooms and there is a need to minimize contact and conserve resources. (40) However, pulse oximetry can overestimate the oxygen saturation in patients with darker skin complexion.…”

Respiratory Rate Oxygenation (ROX) Index as Predictor of High Flow Nasal Cannula in Pediatric Patients in Pediatric Intensive Care Unit dr Cipto Mangunkusumo Hospital

“…3 A standard parameter to evaluate HFNC failure in adults is the SF ratio, which is the ratio of SpO 2 to FiO 2 . 7 Another parameter as a predictor of HFNC therapy that is widely used in adult patients is respiratory rate oxygenation (ROX) index, de ned as the ratio of SF to the respiratory rate (RR). 8 Roca et al evaluated the ROX index in the adult population with pneumonia, cut-off value > 4.88 at 12 hours after HFNC therapy, with a sensitivity of 70% and speci city of 72.4%.…”