Role of SpO2/FiO2 Ratio and ROX Index in Predicting Early Invasive Mechanical Ventilation in COVID-19. A Pragmatic, Retrospective, Multi-Center Study.

Ana Alberdi-Iglesias,Miguel A Castro Villamor,Raúl López-Izquierdo,Carlos Del Pozo Vegas,Guillermo Ortega Rabbione,Francisco Martín-Rodríguez,Cristina Jorge-Soto,María G Núñez-Toste,Ana I Rubio-Babiano,José L Martín-Conty,Ancor Sanz-García

doi:10.3390/biomedicines9081036

Abstract

The ability of COVID-19 to compromise the respiratory system has generated a substantial proportion of critically ill patients in need of invasive mechanical ventilation (IMV). The objective of this paper was to analyze the prognostic ability of the pulse oximetry saturation/fraction of inspired oxygen ratio (SpO2/FiO2) and the ratio of SpO2/FiO2 to the respiratory rate–ROX index–as predictors of IMV in an emergency department in confirmed COVID-19 patients. A multicenter, retrospective cohort study was carried out in four provinces of Spain between March and November 2020. The discriminative power of the predictive variable was assessed through a prediction model trained using a derivation sub-cohort and evaluated by the area under the curve (AUC) of the receiver operating characteristic (ROC) on the validation sub-cohort. A total of 2040 patients were included in the study. The IMV rate was 10.1%, with an in-hospital mortality rate of 35.3%. The performance of the SpO2/FiO2 ratio was better than the ROX index–AUC = 0.801 (95% CI 0.746–0.855) and AUC = 0.725 (95% CI 0.652–0.798), respectively. In fact, a direct comparison between AUCs resulted in significant differences (p = 0.001). SpO2 to FiO2 ratio is a simple and promising non-invasive tool for predicting risk of IMV in patients infected with COVID-19, and it is realizable in emergency departments.

Highlights

Introduction distributed under the terms andCoronavirus disease 2019 (COVID-19) has caused a major disruption in the normal operations of healthcare systems, demanding a reorientation of all routine care towards strategic medicine [1,2]
We found that the SpO2/fraction of inspired oxygen (FiO2) ratio had better accuracy than the ROX index in predicting invasive mechanical ventilation (IMV)
We demonstrated the prognostic value of SpO2/FiO2 in COVID-19 patients where its decreasing trajectory was directly associated with age and an increased risk of deterioration and mortality

Summary

Introduction

Introduction distributed under the terms andCoronavirus disease 2019 (COVID-19) has caused a major disruption in the normal operations of healthcare systems, demanding a reorientation of all routine care towards strategic medicine [1,2]. One of the primary challenges during the current pandemic has been the assessment of a large pool of patients affected by a new disease with no conditions of the Creative Commons. Some studies have shown that delayed intubation may even worsen [9]. These observations highlight the need to identify objective measurements of early predictors of mechanical ventilation [10,11]. Arterial blood gases can determine true oxygenation status but, in the current pandemic situation, non-invasive solutions are needed to guide actions as early as during hospital triage [12,13]

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