Assessment of the SpO2/FiO2 ratio as a tool for hypoxemia screening in the emergency department

Abstract

We assessed the performance of the ratio of peripheral arterial oxygen saturation to the inspired fraction of oxygen (SpO 2 /FiO 2) to predict the ratio of partial pressure arterial oxygen to the fraction of inspired oxygen (PaO 2 /FiO 2) among patients admitted to our emergency department (ED) during the SARS-CoV-2 outbreak. Methods: We retrospectively studied patients admitted to an academic-level ED in France who were undergoing a joint measurement of SpO 2 and arterial blood gas. We compared SpO 2 with SaO 2 and evaluated performance of the SpO 2 /FiO 2 ratio for the prediction of 300 and 400 mmHg PaO 2 /FiO 2 cutoff values in COVID-19 positive and negative subgroups using receiver-operating characteristic (ROC) curves. Results: During the study period from February to April 2020, a total of 430 arterial samples were analyzed and collected from 395 patients. The area under the ROC curves of the SpO 2 /FiO 2 ratio was 0.918 (CI 95% 0.885-0.950) and 0.901 (CI 95% 0.872-0.930) for PaO 2 /FiO 2 thresholds of 300 and 400 mmHg, respectively. The positive predictive value (PPV) of an SpO 2 /FiO 2 threshold of 350 for PaO 2 /FiO 2 inferior to 300 mmHg was 0.88 (CI95% 0.84-0.91), whereas the negative predictive value (NPV) of the SpO 2 /FiO 2 threshold of 470 for PaO 2 /FiO 2 inferior to 400 mmHg was 0.89 (CI95% 0.75-0.96). No significant differences were found between the subgroups. Conclusions: The SpO 2 /FiO 2 ratio may be a reliable tool for hypoxemia screening among patients admitted to the ED, particularly during the SARS-CoV-2 outbreak.

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

“…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. These results support those published by Lu et al and Catoire et al [19,20].…”

“…On the other hand, prepandemic studies showed that, in acute hypoxemic respiratory failure [31], the value of the SpO2/FiO2 ratio serves as control during noninvasive mechanical ventilation [32], or as a proxy measure for the calculation of the sepsis-related organ failure assessment score when partial pressure of oxygen in arterial blood is not available [33]; however, evidence related to COVID-19 is more limited. In this sense, Catoire et al has suggested that the SpO2/FiO2 ratio is a reliable tool for hypoxemia screening in triage among patients admitted to the ED with respiratory symptoms [20]. Likewise, Lu et al have shown that it could be used to improve the early adjustment of treatments-such as non-invasive or invasive ventilators, high-flow nasal cannula oxygen therapy, and extracorporeal membrane oxygenation-in the ICU [19].…”

“…A study has suggested that the SpO2/FiO2 ratio could be used as a prognostic marker in the management of COVID-19 patients, with the objective of early improvement in the adjustment of treatments in the intensive care unit (ICU) [19]. It has also been evaluated as a possible index for triage upon admission of patients admitted for acute respiratory symptoms, particularly in the case of suspected COVID-19 [20]. Moreover, if respiratory rate is available, ROX index, (SpO2/FiO2)/respiratory rate) can also be obtained [15,21]; its implementation is an additional tool to help emergency services assess the clinical severity of COVID-19 patients, and it also serves as a safety measure during hospital discharges (10).…”

A randomized pilot study using calcitriol in hospitalized COVID-19 patients

“…[ 11 ] Moreover, SaO2/FIO2 is commonly used as an end point in clinical trials for patients with COVID-19, with success and is considered an accurate predictor of PaO2/FIO2 ratio. [ 10 ] ARDS severity when measure by PaO2/FiO2 is classified as mild if 200-300, moderate if 100-200, and severe is less than 100. SaO2/FIO2 ratios of 181 and 235 corresponded approximately to PaO2/FIO2 ratios of 300 and 200, respectively [ 12 ].…”

“…The peripheral arterial oxygenation was completed with SpO2 pulse oximeter. The validity of this measure as a surrogate for the pressure arterial oxygen to the fraction of inspired oxygen (PaO 2 /FiO 2 ) ratio has been demonstrated in numerous studies [ 10 ]…”