Performance of the ROX index in predicting high flow nasal cannula failure in COVID-19 patients: a systematic review and meta-analysis

Abstract

COVID-19 patients with acute hypoxemic respiratory failure (AHRF) benefit from high flow nasal cannula (HFNC) oxygen therapy. However, delays in initiating invasive ventilation after HFNC failure are associated with poorer outcomes. The respiratory oxygenation (ROX) index, combining SpO2/FiO2 and respiratory rate, can predict HFNC failure. This meta-analysis evaluated the optimal ROX index cut-offs in predicting HFNC failure among COVID-19 patients at different measurement timings and clinical settings. Three databases were searched for eligible papers. From each study, we reconstructed the confusion matrices at different cut-offs, fitted linear mixed models to estimate the ROX index distribution function, and derived the area under the summary receiver operator characteristic curve (sAUC) and optimal cut-offs to predict HFNC failure. 24 studies containing 4790 patients were included. Overall sAUC was 0.771 (95% CI: 0.666–0.847) (optimal cut-off: 5.23, sensitivity: 0.732, specificity: 0.690). The cut-off values to achieve 80%, 90% sensitivity, 80%, 90% specificity were 5.70, 6.69, 4.45, 3.37, respectively. We stratified the analysis by ROX measurement time and estimated optimal cut-offs and cut-offs to achieve 80% sensitivity and specificity. For 2–6 h and 6–12 h post-HFNC initiation, we propose the use of 80% specific cut-offs to rule in HFNC failure of < 5.33 and < 3.69, respectively. For 12–24 h post-HFNC initiation, we propose the use of the 80% sensitive cut-off of > 6.07 to rule out HFNC failure. Our analysis confirms the overall utility of the ROX index in risk stratification of COVID-19 patients with AHRF receiving HFNC and provides potentially useful cut-offs for different times from HFNC initiation.

Factors related to mortality of patients with COVID-19 who are admitted to the ICU: Prognostic mortality factors of COVID-19 patients

“…These results may be due to the fact that in most hospital centers the use of NIV was reserved for the most severely ill patients, whereas virtually all patients requiring ICU admission were started on HFNO therapy. Consistent with the scientific literature, [29][30][31] those patients requiring IMV had higher mortality rates, which was quite expected, as these patients were the most severely ill.…”

Latest developments in early diagnosis and specific treatment of severe influenza infection

“…The ratio of oxygen saturation (ROX) index, which combines oxygenation (SpO 2 /FiO 2 ) and work of breathing, [ 109 , 110 ] predicts the failure of HFNCO 2 therapy in patients with acute respiratory failure, particularly in those with COVID-19 pneumonia. [ 111 , 112 ] The ROX index might be clinically useful because it requires few data points and is easy to calculate at the bedside. Nevertheless, this index cannot replace close bedside observation of critically ill patients with respiratory failure.…”