• Aslıhan Gürün Kaya, Miraç Öz, İrem Akdemir Kalkan, Ezgi Gülten, Güle Çınar, Alpay Azap, and Akın Kaya.
• Department of Chest Diseases, Ankara University Faculty of Medicine, Ankara, Turkey.
• Int. J. Clin. Pract. 2021 Dec 1; 75 (12): e14983.

IntroductionGuidelines 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 the pulse oximeter in patients with COVID-19.MethodsWe retrospectively reviewed ABG analyses and SpO2 levels measured simultaneously with ABG in patients hospitalised in COVID-19 wards.ResultsWe categorised total 117 patients into two groups, in whom the difference between SpO2 and SaO2 was ≤4% (acceptable difference) and >4% (large difference). A 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 a 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.ConclusionPulse 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 with low SpO2 measurements.© 2021 John Wiley & Sons Ltd.

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