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

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 ( I ²≈28%) than retrospective studies ( I ²≈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 ETCO 2 is strongly associated with increased mortality and transfusion in the trauma population. Given its low cost and noninvasive nature, prehospital and Emergency department ETCO 2 measurement and use for risk stratification should be considered. Standardized thresholds for low, normal, and high ETCO 2 and prospective studies are needed to optimize clinical implementation. ( J Trauma Acute Care Surg . 2026;101: 331-339. Copyright © 2026 Wolters Kluwer Health, Inc. All rights reserved.).

Systematic Review/Meta-analysis; Level III.