The PaO(2)/FiO(2) is independently associated with 28-day mortality in patients with sepsis: a retrospective analysis from MIMIC-IV database

BACKGROUND: To clarify the relationship between the PaO(2)/FiO(2) and 28-day mortality in patients with sepsis. METHODS: This was a retrospective cohort study regarding MIMIC-IV database. Nineteen thousand two hundred thirty-three patients with sepsis were included in the final analysis. PaO(2)/FiO(2) was exposure variable, 28-day mortality was outcome variable. PaO(2)/FiO(2) was log-transformed as LnPaO(2)/FiO(2). Binary logistic regression was used to explore the independent effects of LnPaO(2)/FiO(2) on 28-day mortality using non-adjusted and multivariate-adjusted models. A generalized additive model (GAM) and smoothed curve fitting was used to investigate the non-linear relationship between LnPaO(2)/FiO(2) and 28-day mortality. A two-piecewise linear model was used to calculate the OR and 95% CI on either side of the inflection point. RESULTS: The relationship between LnPaO(2)/FiO(2) and risk of 28-day death in sepsis patients was U-shape. The inflection point of LnPaO(2)/FiO(2) was 5.30 (95%CI: 5.21—5.39), which indicated the inflection point of PaO(2)/FiO(2) was 200.33 mmHg (95%CI: 183.09 mmHg—219.20 mmHg). On the left of inflection point, LnPaO(2)/FiO(2) was negatively correlated with 28-day mortality (OR: 0.37, 95%CI: 0.32—0.43, p < 0.0001). On the right of inflection point, LnPaO(2)/FiO(2) was positively correlated with 28-day mortality in patients with sepsis (OR: 1.53, 95%CI: 1.31—1.80, p < 0.0001). CONCLUSIONS: In patients with sepsis, either a high or low PaO(2)/FiO(2) was associated with an increased risk of 28-day mortality. In the range of 183.09 mmHg to 219.20 mmHg, PaO(2)/FiO(2) was associated with a lower risk of 28-day death in patients with sepsis.