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

Abstract

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 significantly 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.

Keywords: Acute injury; ETCO2; End-tidal capnography; Prehospital triage; Shock; Trauma triage.