End-tidal carbon dioxide as a predictor of mortality in trauma patients: A systematic review and meta-analysis.

Abstract

End-tidal carbon dioxide (ETCO₂) is a noninvasive marker reflecting the interplay of ventilation, perfusion, and metabolism. Its prognostic value as a predictor for mortality in trauma patients remains variably defined across prehospital and emergency department (ED) settings. We conducted a systematic review and meta-analysis. PubMed, SCOPUS, Cochrane Library, Web of Science, and EMBASE were searched from inception to February 2025, with an update in July 2025. Eligible studies enrolled trauma patients with reported ETCO₂ and stratified outcomes by low versus normal/high ETCO₂ (as defined by the original authors). The primary outcome was all-cause mortality; the secondary outcome was receipt of any blood transfusion. Random-effects models generated pooled odds ratios (ORs) with 95% confidence intervals (CIs). Heterogeneity, sensitivity, publication bias, and moderator/meta-regression analyses were performed. Eight observational studies (n= 2,407) met the inclusion criteria: three prospective Emergency Department-based and 5 retrospective prehospital cohorts. All studies were based in the United States. Overall, 732 (30%) patients had low ETCO₂. Low ETCO₂ was associated with significantly higher mortality (21.8% vs. 12.0%); pooled OR 9.59 (95% CI: 3.35-27.49; P<0.001). Findings were robust to one-study-removed sensitivity analyses (OR range 5.88-15.23). Prospective ED studies demonstrated lower heterogeneity (I²≈28%) than retrospective studies (I²≈83%). Thresholds defining "low" ETCO₂ varied (≤30-≤33 mm Hg). Meta-regression showed higher initial systolic blood pressure correlated with lower mortality odds (corr. coeff. -0.101; 95% CI: -0.17 to -0.029; P=0.0054). Four studies reporting transfusion showed higher odds with low ETCO₂ (7.4% vs. 1.3%); pooled OR: 3.32 (95% CI: 2.12-6.15; P<0.001). Low ETCO2 is strongly associated with increased mortality and transfusion in the trauma population. Given its low cost and noninvasive nature, prehospital and Emergency department ETCO2 measurement and use for risk stratification should be considered. Standardized thresholds for low, normal, and high ETCO2 and prospective studies are needed to optimize clinical implementation. (J Trauma Acute Care Surg. 2026;00:00-00. Copyright © 2026 Wolters Kluwer Health, Inc. All rights reserved.). Systematic Review/Meta-analysis; Level III.