Study participants
We retrospectively reviewed patients hospitalized in the COVID-19 wards
of Ankara University Faculty of Medicine from 1 September 2020 to 31
January 2021. Among patients with confirmed COVID-19 infection based on
a positive real-time reverse transcriptase-polymerase chain reaction
(RT-PCR) testing, the patients whose ABG was sampled during their
hospitalization and simultaneously SpO2 measurement by
pulse oximetry was recorded were enrolled in the study. The following
patients were excluded from the study: patients with hypotension (mean
arterial pressure< 65 mmHg); patients with hypothermia (body
temperature < 35 0C); patients with low
hemoglobin level (Hb<10 gr/dL); patients with hematological
malignancy; patients with peripheral vascular disease; patients who had
been under long-term oxygen therapy due to chronic respiratory failure,
patients with connective tissue disease that can affect skin thickness
and peripheral vascular structures, patients with methemoglobinemia, and
patients with missing laboratory data. The study was approved by the
Human Research Ethics Committee of Ankara University
(16.02.21/12-129-21).