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.