title: Utility of initial prehospital end-tidal carbon dioxide measurements to predict poor outcomes in adult asthmatic patients.
abstract: OBJECTIVE
  To 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.
  
  
  METHODS
  This 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).
  
  
  RESULTS
  We 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.
  
  
  CONCLUSIONS
  Extreme (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.
authors.forename: Roxanne
authors.initials: R
authors.lastname: Nagurka
authors.forename: Samuel
authors.initials: S
authors.lastname: Bechmann
authors.forename: William
authors.initials: W
authors.lastname: Gluckman
authors.forename: Sandra R
authors.initials: SR
authors.lastname: Scott
authors.forename: Scott
authors.initials: S
authors.lastname: Compton
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Lamba
mesh_terms: D000328:Adult; D001249:Asthma / Q000145:classification / Q000175:diagnosis*; D001784:Blood Gas Analysis / Q000295:instrumentation / Q000379:methods*; D002245:Carbon Dioxide / Q000032:analysis*; D004632:Emergency Medical Services / Q000379:methods / Q000592:standards* / Q000706:statistics & numerical data; D005260:Female; D006786:Hospitals, Urban / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013990:Tidal Volume
chemical_list: D002245:Carbon Dioxide