Tuberc Respir Dis.  2021 Apr;84(2):125-133. 10.4046/trd.2020.0126.

The Association between Mortality and the Oxygen Saturation and Fraction of Inhaled Oxygen in Patients Requiring Oxygen Therapy due to COVID-19–Associated Pneumonia

  • 1Department of Internal Medicine, Daegu Veterans Hospital, Daegu, Korea
  • 2Department of Internal Medicine, Daegu Catholic University School of Medicine, Daegu, Korea


The coronavirus disease (COVID-19) can manifest in a range of symptoms, including both asymptomatic systems which appear nearly non-existent to the patient, all the way to the development of acute respiratory distress syndrome (ARDS). Specifically, COVID-19–associated pneumonia develops into ARDS due to the rapid progression of hypoxia, and although arterial blood gas analysis can assist in halting this deterioration, the current environment provided by the COVID-19 pandemic, which has led to an overall lack of medical resources or equipment, has made it difficult to administer such tests in a widespread manner. As a result, this study was conducted in order to determine whether the levels of oxygen saturation (SpO2) and the fraction of inhaled oxygen (FiO2) (SF ratio) can also serve as predictors of ARDS and the patient’s risk of mortality.
This was a retrospective cohort study conducted from February 2020 to Mary 2020, with the study’s subjects consisting of COVID-19 pneumonia patients who had reached a state of deterioration that required the use of oxygen therapy. Of the 100 COVID-19 pneumonia cases, we compared 59 pneumonia patients who required oxygen therapy, divided into ARDS and non-ARDS pneumonia patients who required oxygen, and then investigated the different factors which affected their mortality.
At the time of admission, the ratios of SpO2, FiO2, and SF for the ARDS group differed significantly from those of the non-ARDS pneumonia support group who required oxygen (p<0.001). With respect to the predicting of the occurrence of ARDS, the SF ratio on admission and the SF ratio at exacerbation had an area under the curve which measured to be around 85.7% and 88.8% (p<0.001). Multivariate Cox regression analysis identified that the SF ratio at exacerbation (hazard ratio [HR], 0.916; 95% confidence interval [CI], 0.846–0.991; p=0.029) and National Early Warning Score (NEWS) (HR, 1.277; 95% CI, 1.010–1.615; p=0.041) were significant predictors of mortality.
The SF ratio on admission and the SF ratio at exacerbation were strong predictors of the occurrence of ARDS, and the SF ratio at exacerbation and NEWS held a significant effect on mortality.


COVID-19; Pneumonia; Acute Respiratory Distress Syndrome; Oxygen Saturation; Mortality
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