Accuracy of <scp>PaO</scp>₂/<scp>FiO</scp>₂ calculated from <scp>SpO</scp>₂ for severity assessment in ED patients with pneumonia

Abstract

The Ellis equation was more accurate than the Rice equation for estimating PaO2 /FiO2 , especially at higher levels of P/F ratio. Estimation of PaO2 /FiO2 from SpO2 is accurate enough for initial oxygenation assessment. Ellis and Rice equations could misclassify 20% and 30% of patients, respectively, at higher levels of PaO2 /FiO2 . For patients with abnormal oxygenation falling near thresholds for clinical decision making, arterial blood gas measurement preferably on room air is more accurate.