Association between the neutrophil-to-albumin ratio and mortality in patients undergoing tracheal intubation: a retrospective cohort study

Introduction: Tracheal intubation in intensive care unit (ICU) patients is associated with significant risks, necessitating simple mortality predictors. We investigated the relationship between neutrophil percentage-to-albumin ratio (NPAR) and in-hospital and ICU mortality in intubated patients. Methods: This retrospective cohort study analyzed 1,401 intubated ICU patients from MIMIC-IV. Multivariable Cox regression and smooth curve fitting were used to assess the association between NPAR and mortality. A two-stage linear regression model and threshold analysis evaluated nonlinear relationships. Results: Among patients (mean age 62.7 ± 17.1 years; 43.6% female), NPAR exhibited a U-shaped relationship with mortality, with an inflection point at 2.2 observed in this cohort. Below this inflection point, hazard ratios (HRs) were 0.656 (95% CI: 0.492-0.875) for in-hospital mortality and 0.586 (95% CI: 0.413-0.831) for ICU mortality. Above 2.2, HRs increased to 1.187 (95% CI: 1.097-1.286) and 1.15 (95% CI: 1.047-1.264), respectively. Conclusion: NPAR demonstrates a U-shaped association with mortality in intubated ICU patients, with elevated risks above 2.2. Further large-scale studies are needed to validate these findings.