The ROX index as a predictor of high-flow nasal cannula outcome in pneumonia patients with acute hypoxemic respiratory failure: a systematic review and meta-analysis

Abstract

Background: The respiratory rate-oxygenation (ROX) index has been increasingly applied to predict the outcome of high-flow nasal cannula (HFNC) in pneumonia patients with acute hypoxemic respiratory failure (AHRF). However, its diagnostic accuracy for the HFNC outcome has not yet been systematically assessed. This meta-analysis sought to evaluate the predictive performance of the ROC index for the successful weaning from HFNC in pneumonia patients with AHRF.

Methods: A literature search was conducted on electronic databases through February 12, 2022, to retrieve studies that investigated the diagnostic accuracy of the ROC index for the outcome of HFNC application in pneumonia patients with AHRF. The area under the hierarchical summary receiver operating characteristic curve (AUHSROC) was estimated as the primary measure of diagnostic accuracy due to the varied cutoff values of the index. We observed the distribution of the cutoff values and estimated the optimal threshold with corresponding 95% confidential interval (CI).

Results: Thirteen observational studies comprising 1751 patients were included, of whom 1003 (57.3%) successfully weaned from HFNC. The ROC index exhibits good performance for predicting the successful weaning from HFNC in pneumonia patients with AHRF, with an AUHSROC of 0.81 (95% CI 0.77-0.84), a pooled sensitivity of 0.71 (95% CI 0.64-0.78), and a pooled specificity of 0.78 (95% CI 0.70-0.84). The cutoff values of the ROX index were nearly conically symmetrically distributed; most data were centered between 4.5 and 6.0, and the mean and median values were 4.8 (95% CI 4.2-5.4) and 5.3 (95% CI 4.2-5.5), respectively. Moreover, the AUHSROC in the subgroup of measurement within 6 h after commencing HFNC was comparable to that in the subgroup of measurement during 6-12 h. The stratified analyses also suggested that the ROC index was a reliable predictor of HFNC success in pneumonia patients with coronavirus disease 2019.

Conclusions: In pneumonia patients with AHRF, the ROX index measured within 12 h after HFNC initiation is a good predictor of successful weaning from HFNC. The range of 4.2-5.4 may represent the optimal confidence interval for the prediction of HFNC outcome.

Keywords: Acute respiratory failure; High flow nasal cannula; Intubation; Pneumonia; ROX index.

Fig. 1

Flowchart of the study selection in this study. HFNC high-flow nasal cannula, NIV non-invasive ventilation

Fig. 2

HSROC curve of the ROX index for predicting the successful weaning from HFNC. The area under the hierarchical summary receiver operating curve was 0.81 (95% CI 0.77–0.84). The size of the circles indicates the weight of each individual study. HSROC hierarchical summary receiver operating characteristic, ROX respiratory rate-oxygenation, HFNC high-flow nasal cannula

Fig. 3

Forest plot of sensitivity and specificity of the ROX index for predicting the successful weaning from HFNC. ROX respiratory rate-oxygenation, HFNC high-flow nasal cannula

Fig. 4

Scatter plot of the cut-off values of the ROX index. The cutoff values were nearly conically symmetrically distributed and most data were centered between 4.5 and 6.0. ROX respiratory rate-oxygenation