The Association of Prehospital End-Tidal Carbon Dioxide with Survival Following Out-of-Hospital Cardiac Arrest

Abstract

Objective

End tidal carbon dioxide (ETCO₂) is often used to assess ventilation and perfusion during cardiac arrest resuscitation. However, few data exist evaluating the relationship between ETCO₂ values and mortality in the context of contemporary resuscitation practices. We aimed to explore the association between ETCO₂ and mortality following out-of-hospital cardiac arrest (OHCA).

Methods

We used the 2018–2021 ESO annual datasets to query all non-traumatic OHCA patients with attempted resuscitation. Patients with documented DNR/POLST, EMS-witnessed arrest, ROSC after bystander CPR only, or < 2 documented ETCO₂ values were excluded. The lowest and highest ETCO₂ values recorded during the total prehospital interval, in addition to the pre- and post-ROSC intervals for resuscitated patients, were calculated. Multivariable logistic regression models adjusted for age, sex, initial rhythm, witnessed status, bystander CPR, etiology, OHCA location, sodium bicarbonate administration, number of milligrams of epinephrine administered, and response interval were used to evaluate the association between measures of ETCO₂ and mortality.

Results

Hospital outcome data were available for 14,122 patients, and 2,209 (15.6%) were classified as surviving to discharge. Compared to patients with maximum prehospital ETCO₂ values of 30–40 mmHg, odds of mortality were increased for patients with maximum prehospital ETCO₂ values of <20 mmHg (aOR: 3.5 [2.1, 5,9]), 20–29 mmHg (aOR: 1.5 [1.1, 2.1]), and >50 mmHg (aOR: 1.5 [1.2, 1.8]). After 20 minutes of ETCO₂ monitoring, <12% of patients had ETCO₂ values <10 mmHg. This cutpoint was 96.7% specific and 6.9% sensitive for mortality.

Conclusion

In this dataset, both high and low ETCO₂ values were associated with increased mortality. Contemporary resuscitation practices may make low ETCO₂ values uncommon, and field termination decision algorithms should not use ETCO₂ values in isolation.

Acknowledgments

We would like to thank ESO for providing access to the data that made this study possible. In addition, we would like to recognize the efforts of the thousands of EMS clinicians across the United States who treated the patients and collected the data evaluated in this work.

Disclosure Statement

RPC and BM are employees of ESO Inc. The authors do not believe that they have any other financial or intellectual relationships that would influence the reporting of the results contained within this study.