Prehospital ETCO₂ is predictive of death in intubated and non-intubated patients

Background: Prehospital identification of shock in trauma patients lacks accurate markers. Low end tidal carbon dioxide (ETCO2) correlates with mortality in intubated patients. The predictive value of ETCO2 obtained by nasal capnography cannula (NCC) is unknown. We hypothesized that prehospital ETCO2 values obtained by NCC and in-line ventilator circuit (ILVC) would be predictive of mortality. Methods: This was a prospective, observational, multicenter study. ETCO2 values were collected by a NCC or through ILVC. AUROCs were compared with prehospital systolic blood pressure (SBP) and shock index (SI). The Youden index defined optimal cutoffs. Results: Of 550 enrolled patients, 487 (88.5%) had ETCO2 measured through an NCC. Median age was 37 (27-52) years; 76.5% were male; median ISS was 13 (5-22). Mortality was 10.4%. Minimum prehospital ETCO2 signif-icantly predicted mortality with an AUROC of 0.76 (CI 0.69-0.84; Youden index = 22 mmHg), outperforming SBP with an AUROC of 0.68; (CI 0.62-0.74, p = 0.04) and shock index with an AUROC of 0.67 (CI 0.59-0.74, p = 0.03). Conclusion: Prehospital ETCO2 measured by non-invasive NCC or ILVC may be predictive of mortality in injured patients.