Is pulse oximeter a reliable tool for non-critically ill patients with COVID-19?

Gürün Kaya, Aslihan; Öz, Miraç; Akdemir Kalkan, Irem; Gülten, Ezgi; Çinar, Güle; Azap, Alpay; Kaya, Akin

INTRODUCTION: Guidelines recommend using a pulse oximeter rather than arterial blood gas (ABG) for COVID-19 patients. However, significant differences can be observed between oxygen saturation measured by pulse oximetry (SpO2 ) and arterial oxygen saturation (SaO2 ) in some clinical conditions. We aimed to assess the reliability of pulse oximeter in patients with COVID-19 METHODS: We retrospectively reviewed ABG analyses and SpO2 levels measured simultaneously with ABG in patients hospitalized in COVID-19 wards. RESULTS: We categorized total 117 patients into two groups; in whom the difference between SpO2 and SaO2 was ≤4% (acceptable difference) and >4% (large difference). Large difference group exhibited higher neutrophil count, C-reactive protein, ferritin, fibrinogen, D-dimer and lower lymphocyte count. Multivariate analyses revealed that increased fibrinogen, increased ferritin and decreased lymphocyte count were independent risk factors for large difference between SpO2 and SaO2 . The total study group demonstrated the negative bias of 4.02% with the limits of agreement of -9.22% to 1.17%. The bias became significantly higher in patients with higher ferritin, fibrinogen levels and lower lymphocyte count. CONCLUSION: Pulse oximeters may not be sufficient to assess actual oxygen saturation especially in COVID-19 patients with high ferritin and fibrinogen levels and low lymphocyte count low SpO2 measurements.