Correlation of SpO2/FiO2 Ratio and PaO2/FiO2 Ratio in Hypoxemic Patient While Breathing in Room Air
1 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Phramongkutklao Hospital, Bangkok, Thailand
Affiliation : Nittha Oer-areemitr MD1, Kunchit Piyavechviratana MD1
Background : Hypoxemia is a common situation and arterial blood gas [ABG] analysis is the standard tool for diagnosing hypoxemia.
PaO2/FiO2 [P/F] ratio is a crucial parameter to identify degree of hypoxemia but ABG machine is required. Pulse oximetry is a tool
to evaluate oxygenation of patients, it is non-invasive, rapid, and widely available.
Objective : To evaluate the correlation between SpO2/FiO2 [S/F] and PaO2/FiO2 [P/F] ratio.
Materials and Methods : The present report was an observational study in the hypoxemic patients who need ABG analysis at room
air, SpO2 were also recorded at the same time of arterial puncture. The correlation and linear regression analysis were analyzed to
(cid:976)ind the relationship between P/F and S/F ratio.
Results : One hundred seventy-nine patients were enrolled . The mean PaO2 and SpO2 were 64.43±10.8 and 89.63±5.22, respectively.
The mean P/F and S/F were 306.79±51.45 and 426.82±24.86. The correlation between P/F and S/F was signi(cid:976)icant (r = 0.771),
p-value was <0.0001, the equation as calculated P/F = -375 + 1.6 (S/F); r = 0.771 and r2 = 0.595.
Conclusion : S/F from pulse oximetry was signi(cid:976)icantly correlated with P/F from ABG analysis but the exact equation was not as
good enough to estimate P/F calculated from the S/F of the pulse oximetry.
Keywords : Correlation PaO2/FiO2, SpO2/FiO2
