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 find 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 significant (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 significantly 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