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 (SpO(2)) measured by pulse oximeter is consistently lower than arterial oxygen saturation (SaO(2)) measured directly by blood gas analysis. In this study, we aimed to evaluate the correlation between SpO(2) and SaO(2), and SpO(2) and partial pressure of oxygen (PaO(2)), and compare the SpO(2)/FiO(2 )(SF) and PaO(2)/FiO(2 )(PF) ratios in patients with coronavirus disease 2019 (COVID-19). Methods In this observational study, SpO(2 )was recorded and arterial blood gas analysis was performed among 70 COVID-19 patients presenting on room air (FiO(2 )= 0.21). SaO(2) and PaO(2) were recorded from arterial blood gas analysis. The SF and PF ratios were then calculated. Results The strength of correlations between SpO(2 )and SaO(2), and SpO(2) and PaO(2), were significant (p<0.001) and moderately positive [Pearson coefficient (r) = 0.68, 0.53]. SpO(2) 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, SpO(2) was found to have a positive correlation with SaO(2 )and PaO(2 )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.