Nonlinear association between admission oxygen partial pressure and in-hospital and one-year all-cause mortality in patients with coronavirus disease pneumonia: A retrospective cohort study

Background: This study investigated the correlation between admission partial pressure of arterial oxygen (PaO 2 ) levels and both in-hospital mortality and 1-year all-cause mortality among patients diagnosed with coronavirus disease (COVID-19) pneumonia. Methods: This retrospective cohort study included patients with COVID-19 pneumonia admitted to the First Hospital of Jinzhou Medical University. Restricted cubic spline regression and logistic regression analyses were employed to assess the relation between PaO 2 levels and the risk of in-hospital mortality and all-cause mortality within 1 year. Subgroup analyses were performed, stratified by age, sex, presence of cardiac disease, diabetes, hypertension, whether supplemental oxygen was provided during arterial blood gas analysis, and severity of pneumonia. Results: The study included 737 participants with in-hospital and 1-year all-cause mortality rates of 15.7% and 26.7%, respectively. Restricted cubic spline analysis revealed an L-shaped association between admission PaO 2 levels and in-hospital mortality ( P nonlinear <0.001) and a U-shaped relation with 1-year all-cause mortality ( P nonlinear <0.001), with a nadir risk of 82 mmHg. Threshold analyses indicated an odds ratio of 0.931 (95% confidence interval (CI): 0.91–0.952) for in-hospital mortality and 0.951 (95% CI: 0.933–0.969) for 1-year all-cause mortality when PaO 2 was <82 mmHg. Conversely, when PaO 2 was ≥82 mmHg, the odds ratio for in-hospital mortality was 1.022 (95% CI: 0.991–1.055), and for 1-year all-cause mortality was 1.029 (95% CI: 1.004–1.054). Conclusions: This study revealed a nonlinear relation between PaO 2 levels at admission and both in-hospital mortality and 1-year all-cause mortality in patients with COVID-19 pneumonia, with a notable inflection point observed at approximately 82 mmHg.