The ROX index can be a useful tool for the triage evaluation of COVID‐19 patients with dyspnoea

Abstract

Aim To assess whether the application of a non‐invasive tool, such as ratio of oxygen saturation (ROX) index, during triage can identify patients with COVID‐19 at high risk of developing acute respiratory distress syndrome (ARDS). Design A multi‐centre, observational, retrospective study. Methods Only COVID‐19 positive patients who required an emergency department evaluation for dyspnoea were considered. The primary objective of the study was to compare the ROX value obtained during triage with the medical diagnosis of ARDS and intubation in 72 h of the triage evaluation. The ROX index value was also compared with objective outcomes, such as the pressure of arterial O2 (PaO2)/fraction of inspired oxygen (FiO2) ratio and the lung parenchyma volume involved in COVID‐19‐related inflammatory processes, based on 3D reconstructions of chest computed tomography (CT). Results During the study period, from 20 March 2020 until 31 May 2020, a total of 273 patients with confirmed SARS‐CoV‐2 infection were enrolled. The predictive ability of ROX for the risk of developing ARDS in 72 h after triage evaluation was associated with an area under the receiver operating characteristic (AUROC) of 0.845 (0.797–0.892, p < 0.001), whereas the AUROC value was 0.727 (0.634–0.821, p < 0.001) for the risk of intubation. ROX values were strongly correlated with PaO2/FiO2 values (r = 0.650, p < 0.001), decreased ROX values were associated with increased percentages of lung involvement based on 3D CT reconstruction (r = −0.371, p < 0.001). Conclusion The ROX index showed a good ability to identify triage patients at high evolutionary risk. Correlations with objective but more invasive indicators (PaO2/FiO2 and CT) confirmed the important role of ROX in identifying COVID‐19 patients with extensive pathological processes. Impact During the difficult triage evaluation of COVID‐19 patients, the ROX index can help the nurse to identify the real severity of the patient. The triage systems could integrate the ROX in the rapid patient assessment to stratify patients more accurately.

Correlation of non-invasive oxygenation parameters with paO2/FiO2 ratio in patients with COVID-19 associated ARDS

“…To the best of our knowledge, only a few papers exploring the correlation between S/F and P/F ratio have been published, and none of them covering COVID-19 patients [3] , [4] , [5] . A recently published study has investigated the correlation between ROX index and P/F ratio in patients with SARS-CoV-2 infection, and the pooled results are consistent with our ones (R = 0.650, p < 0.001) [6] . In all the tests we performed, S/F ratio showed a better correlation than ROX index with P/F ratio; this seems likely related to a wide dispersion of RR values because of the phenomenon of silent hypoxemia, well described in CARDS [7] .…”

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

“…In our study, the SF ratios after HFNC initiation had an acceptable predictive power (AUC: 0.762 and 0.733). Hu et al [ 23 ] reported that both the ROX index at 6 h and the SF and PF ratios at 6 h are accurate predictors of HFNC failure (AUC: SF ratio of 0.786 and PF ratio of 0.749). Arterial blood gas analysis cannot be performed frequently because COVID-19 patients are isolated in a closed room and the number of healthcare personnel is limited.…”

“…Arterial blood gas analysis cannot be performed frequently because COVID-19 patients are isolated in a closed room and the number of healthcare personnel is limited. Moreover, respiratory rate may be difficult to objectively monitor because the accuracy of respiratory rate measurements by healthcare professionals is suboptimal [ 23 ]. On the other hand, the SF ratio can be calculated by objectively measuring pulse oximetry and FiO 2 ; therefore, we suggest that SF ratios can be a useful tool for predicting intubation in COVID-19 patients.…”

Silent hypoxia is not an identifiable characteristic in patients with COVID-19 infection

“…The ROX index, initially designed to predict failure of non-invasive oxygenation in ICU and so utilising only bedside observations, has been applied to patients with COVID-19 in ICU to assess the severity of their hypoxic respiratory failure [17][18][19][20]23] and in correlation with radiological findings [24], with values ranging from 3 [25] to 5.99 [23] (including the non-COVID discriminator of 4.99 [26]) being considered the optimal cut-off to signify requirement for intubation in the ICU setting. By considering ROX as a marker of respiratory response to relative hypoxaemia, our study not only supports the use of this index in predicting adverse outcomes in ICU, but suggests that it may have utility for detecting patients outside of ICU at risk of deterioration with exaggerated respiratory responses to lower degrees of relative hypoxaemia, as it can be derived in a straightforward manner from nursing observations.…”