• Roxanne Nagurka, Samuel Bechmann, William Gluckman, Sandra R Scott, Scott Compton, and Sangeeta Lamba.
• Prehosp Emerg Care. 2014 Apr 1;18(2):180-4.

Study ObjectiveTo determine if an initial (before treatment) prehospital end-tidal carbon dioxide (EtCO2) measurement in adult, non-chronic obstructive pulmonary disease (COPD), asthmatic patients predicts patient outcomes.MethodsThis is a retrospective chart review of EtCO2 assessment data in a convenience sample of adult, asthmatic patients transported via advanced life support (ALS) units to a large, urban, academic hospital. Initial EtCO2 measurements were obtained routinely on all respiratory distress patients in the field, and emergency department physicians were unaware of the results. Data were analyzed using descriptive statistics, including percentages, means, and 95% confidence intervals (CI).ResultsWe reviewed data for prehospital initial EtCO2 measurements on 299 unique asthma patients (repeat visits by same patient were not included). Mean (SD) age was 43.1 years (12.5) and 142 (47.5%) were male. The mean EtCO2 measurement was 38.8 mmHg (SD ± 9.5; CI: 37.7-39.9; range: 14-82). Examination of initial EtCO2 measurements by deciles revealed that extreme values, in the lowest (14-28 mmHg) and highest (50-82 mmHg) deciles, experienced more markers of poor outcome than less extreme measurements. Patients were thus dichotomized by extreme (n = 59) or nonextreme (n = 240) EtCO2 measurements. More extreme patients were ultimately intubated (30.5 vs. 5.8%; p < 0.001; positive predictive value (ppv) = 30.5% ), and/or admitted to the intensive care unit (ICU) (28.8 vs. 6.7%; p <0.001; ppv = 28.8%), and/or died (5.1 vs. 0%; p = 0.007 [Fisher's exact test]; ppv = 5.1%), than nonextreme patients, respectively.ConclusionExtreme (both low and high) prehospital initial EtCO2 measurements may be associated with markers of poor patient outcomes. Future work will prospectively determine whether the addition of this information improves early recognition of severe asthma episodes beyond clinical assessment.

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