Correlation between SpO2/FiO2 (S/F) ratio and PaO2/FiO2 (P/F) ratio in different modes of ventilation in COVID 19 positive patients in a tertiary hospital in the Philippines

<bold>Background:</bold> The COVID-19 pandemic caused millions of deaths worldwide. One of its characteristics is asymptomatic hypoxemia and often leads to fulminant ARDS causing high mortality. ABG analysis and pulse oximetry can be used to objectively determine the amount of oxygen in arterial blood. Measurement of oxygen saturation with SpO2 can be used for evaluation and control of hypoxemia. Worldwide data is available but lacks domestic data in tan-skinned population. <bold>Results:</bold> This study showed a positive correlation between P/F ratio and S/F ratio. Derived S/F threshold values of 158, 238 and 317 corresponds to P/F ratio of 100, 200 and 300 [ p <0.001] respectively with 100% sensitivity and 88% specificity. It was also inferred that P/F ratio or S/F ratio can be used in any method of oxygen supplementation (room air, nasal cannula, face mask, rebreather mask, high flow nasal insufflation, endotracheal intubation) and there is no variability in results. <bold>Conclusion:</bold> S/F ratio is a reliable non-invasive measure for ARDS which replaces ABG by pulse oximetry in any method of oxygen supplementation and tan-skinned population. Pulse oximetry can be used for early detection of severity of COVID 19-related respiratory failure thus affording prompt treatment and referral to a tertiary hospital. <fig><object-id>erj;64/suppl_68/PA3479/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>