Background: Prolonged ventilation is associated with a high risk of death. This study investigated both patient-level and hospital-level risk factors for in-hospital mortality in patients ventilated for more than 24 hours.
Methods: The analyses were conducted in the framework of a German national multicenter retrospective cohort study. Patient and hospital characteristics were examined using descriptive statistics. Risk factors of in-hospital mortality were analyzed using multilevel robust Poisson regressions for binary outcomes. Potential effect modifications were examined by stratified analyses.
Results: The sample includes 95 672 cases of patients ventilated >24 hours in 163 hospitals covering the period 2016 to 2017. According to the results of multilevel Poisson regressions, main patient-level risk factors for in-hospital mortality were age (per year relative risk [RR] = 1.021, 95% CI = 1.020-1.023), stroke (RR = 1.459; 95% CI = 1.361-1.563), emergency case admission (RR = 1.273, 95% CI = 1.156-1.403), and transfer from another hospital (RR = 1.169, 95% CI = 1.084-1.261). The individual risk of in-hospital death was positively associated with hospital size (RR of hospitals with 600-799 beds vs <100 beds = 1.412, 95% CI = 1.095-1.820) and negatively related to cumulated ventilation patient time (per 1000 days RR = 0.995, 95% CI = 0.993-0.996). University hospital status was identified as an effect modifier, particularly with regard to the patients' admission reasons. The RR of in-hospital death in patients admitted after transfer from another hospital was higher in university hospitals (RR = 1.456, 95% CI = 1.298-1.634) compared to nonuniversity hospitals (RR = 1.077, 95% CI = 1.019-1.139). Likewise, patients admitted as emergency case had a higher relative risk in university hospitals (RR = 1.619, 95% CI = 1.359-1.929) than in nonuniversity hospitals (RR = 1.141, 95% CI = 1.080-1.205).
Conclusion: By providing evidence on multiple patient-level and hospital-level risk factors for in-hospital mortality in patients ventilated for more than 24 hours, this large multicenter study has main implications for quality assessment of clinical care and the adequate specification of risk adjustment models. The revealed effect modifications indicate the relevance of stratified analyses.
Keywords: cohort study; hospital mortality; multilevel analysis; regression analysis; risk factors; ventilation.