A Correlation Analysis of Peripheral Oxygen Saturation and Arterial Oxygen Saturation Among COVID-19 Patients

Background and objective It has been observed that peripheral oxygen saturation (SpO₂) measured by pulse oximeter is consistently lower than arterial oxygen saturation (SaO₂) measured directly by blood gas analysis. In this study, we aimed to evaluate the correlation between SpO₂ and SaO₂, and SpO₂ and partial pressure of oxygen (PaO₂), and compare the SpO₂/FiO₂ (SF) and PaO₂/FiO₂ (PF) ratios in patients with coronavirus disease 2019 (COVID-19). Methods In this observational study, SpO₂ was recorded and arterial blood gas analysis was performed among 70 COVID-19 patients presenting on room air (FiO₂ = 0.21). SaO₂ and PaO₂ were recorded from arterial blood gas analysis. The SF and PF ratios were then calculated. Results The strength of correlations between SpO₂ and SaO₂, and SpO₂ and PaO₂, were significant (p<0.001) and moderately positive [Pearson coefficient (r) = 0.68, 0.53]. SpO₂ value (85%), i.e., SF ratio (404.7 or below), was the best estimate for mild ARDS (acute respiratory distress syndrome) [PF ratio (300 or below)] with a sensitivity of 80.6% and specificity of 53%. Conclusion A pulse oximeter is a vital tool in the diagnosis and management of COVID-19. In our study, SpO₂ was found to have a positive correlation with SaO₂ and PaO₂ with acceptable sensitivity but low specificity in estimating mild ARDS. Therefore, pulse oximetry can be used as a tool for the early diagnosis of mild COVID-19 ARDS as per the given considerations and clinical correlation.