Association between the dead space fraction and mortality in critically ill patients with acute respiratory failure: an analysis of the MIMIC-IV database

Background : Few studies have investigated the association between V _D /V _T and mortality in critically ill patients with acute respiratory failure (ARF). Objective : The primary objective of this study is to clarify the association between V _D /V _T and mortality in critically ill patients with ARF, as well as to determine its optimal predictive threshold for clinical application. Methods : This study was based on the MIMIC-IV database. The analysis using multivariable logistic regression, cox proportional hazards model, and restricted cubic splines (RCS) was used to explore the association between V _D /V _T and mortality. Results : A total of 2,254 patients were included in the study, of whom 1,709 (75.82%) died during their ICU stay. Both multivariable logistic regression and cox proportional hazards model identified V _D /V _T as the most significant predictor of ICU mortality (OR = 16.90, 95%CI: 7.38-38.69, P˂0.001; HR=9.60, 95%CI: 4.95-18.61, P˂0.001). After adjusting for covariates, the RCS analysis continued to demonstrate a significant overall association and a non-linear relationship between V _D /V _T and ICU mortality, with an identified inflection point at 0.222 for V _D /V _T . In addition, the results of the subgroup and stratified analyses were robust, and the univariate forest plot demonstrated that V _D /V _T exhibited an extremely strong association with ICU mortality, accompanied by an overall OR of 2.34 (95% CI: 1.91-2.86, p˂0.001). Conclusion : V _D /V _T is positively associated with ICU mortality in critically ill patients with ARF. And the V _D /V _T of 0.222 may serve as a potential prognostic threshold for predicting clinical outcomes in critically ill patients with ARF.