Cynthia Karam1, Ahmad Oseili1, Fadia M. Shebbo1,2, Mohamad Fakih1, Mohamad F. El-Khatib1

1Department of Anesthesiology and Pain Medicine, American University of Beirut, Beirut, Lebanon
2Department of Epidemiology, American University of Beirut, Beirut, Lebanon

Keywords: COVID‑19, emergency department, high‑flow nasal cannula, hypoxemia, ratio of oxygen saturation index, severe hypoxemic respiratory failure


OBJECTIVES: High flow nasal cannula (HFNC) oxygen therapy has been used as an initial ventilatory support for coronavirus disease 2019 (COVID 19) patients with mixed levels of acute hypoxemic respiratory failure (AHRF). However, the effectiveness of HFNC when used as initial ventilatory support in COVID 19 patients with severe AHRF exclusively is not well documented. Ratio of oxygen saturation (ROX) index (ROX = [SpO2 /fraction of inspired oxygen]/respiratory rate) was shown to predict the outcome of HFNC in intensive care unit patients. Our study aimed to evaluate the utility of the ROX index for predicting HFNC therapy success/failure in COVID 19 patients with severe AHRF when HFNC is used as the first line of ventilatory support.

METHODS: Retrospective study in 67 COVID 19 patients with severe AHRF receiving HFNC in the emergency department at a tertiary care academic medical center. ROX index was determined at 0, 2, 6, 12, and 24 h of HFNC onset. The need to escalate to noninvasive or invasive ventilatory support was documented. The receiver operating characteristic curves were performed and areas under the curves (AUCs) were calculated to evaluate the accuracy of ROX index for differentiating between patients who will succeed or fail HFNC therapy.

RESULTS: HFNC therapy was successful in 19 patients (28.1%) and failed in 48 patients (71.6%). ROX index after 6 h of HFNC initiation had the best predictive capacity for the outcome of HFNC therapy (AUC = 0.78). ROX index >4.4 at 6 h of HFNC onset was significantly associated with HFNC success/failure.

CONCLUSION: ROX index at 6 h after initiating HFNC therapy in COVID 19 patients with severe AHRF has a good predictive capacity for HFNC success/failure.

How to cite this article: Karam C, Oseili A, Shebbo FM, Fakih M, El-Khatib MF. Ratio of oxygen saturation index for predicting high‑flow nasal cannula outcomes in emergency department for COVID-19 patients with severe hypoxemia: Aretrospective study. Turk J Emerg Med 2024;24(1):41-7.

Ethics Committee Approval

This study was approved by the Institutional Review Board at the American University of Beirut, Beirut, Lebanon (IRB# BIO‑2021‑0318). IRB approval date: November 25, 2021.

Author Contributions

All authors had full access to the data, contributed to the study, reviewed, edited, and approved the final version for publication, and were responsible for its accuracy and integrity.

Conflict of Interest

None Declared.

Financial Disclosure