Prediction of Mortality in COVID-19 Patients Using Diagnostic Value of SaO2/FiO2 and PaO2/FiO2 Ratios at Hospital Admission: A Retrospective Cohort Study

Background: Approximately 20% of COVID-19 patients have an arterial blood oxygen partial pressure to fractional inspired oxygen concentration ratio (PaO2/FiO2) of less than 300. Objective: To analyze the diagnostic value of oxygen saturation of arterial blood (SaO2)/FiO2 and PaO2/FiO2 ratios measured upon hospital admission for predicting mortality in COVID-19 patients. Methods: A retrospective cohort study was conducted at two hospitals in the Central Region of Brazil, involving 199 COVID-19 patients hospitalized from March to August 2020. Data were collected from medical records. Respiratory markers were obtained from blood gas analysis and pulse oximetry measurements taken upon admission. Receiver Operating Characteristic curves were constructed to assess the accuracy of the studied ratios in predicting mortality among the analyzed patients. Results: There were 33 deaths among the total hospitalized COVID-19 patients. Among those with available data on PaO2/FiO2 and SaO2/FiO2 measured upon admission, 22 (20.6%) deaths occurred. Notably, the severity of ARDS correlated with an increased risk of death (p=0.001) within this subgroup. Patients who died had lower PaO2/FiO2 and SaO2/FiO2 ratios compared to survivors. Both PaO2/FiO2 and SaO2/FiO2 ratios measured upon hospital admission were accurate parameters for predicting mortality in COVID-19 patients. The cutoff point of 280 for PaO2/FiO2 and 290 for SaO2/FiO2 showed satisfactory sensitivity in predicting death among the analyzed patients. Conclusion: SaO2/FiO2 and PaO2/FiO2 ratios measured upon hospital admission exhibited good sensitivity and accuracy in predicting mortality in hospitalized COVID-19 patients. This finding may prove valuable in guiding future pandemic decision-making in healthcare practice and contributing to oxygen management for both non-invasive and invasive ventilation.