title: Can quantitative capnometry differentiate between cardiac and obstructive causes of respiratory distress?
abstract: OBJECTIVE
  To determine whether quantitative measurement of end-tidal carbon dioxide (ETCO2) can differentiate between cardiac and obstructive causes of respiratory distress.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Emergency department (ED) of a tertiary care hospital.
  
  
  METHODS
  Adult patients who presented to the ED with moderate-to-severe dyspnea. Patients were excluded if they were unable to cooperate with the performance of peak expiratory flow rate (PEFR) or ETCO2 tests, were younger than 18 years of age, or had received prehospital intervention for their respiratory distress.
  
  
  METHODS
  Physicians obtained an ETCO2 level and PEFR prior to ED pharmacologic intervention. A hand-held capnometer with digital read-out was used to obtain the ETCO2 level. The patient's age, sex, initial vital signs, breath sounds and medication history, the presence or absence of diaphoresis and/or orthopnea, the duration of symptoms, the chest radiograph interpretation, and final diagnosis were also recorded.
  
  
  RESULTS
  Forty-two patients were eligible for inclusion in the analysis. The mean ETCO2 level was 31.1+/-9.4 mm Hg; the mean PEFR was 161.3+/-53.1 L/min. The ETCO2 levels for pulmonary edema/congestive heart failure (CHF) patients differed significantly from those of asthma/COPD patients (27.1+/-7.8 mm Hg vs 33.4+/-9.6 mm Hg; p=0.0375). However, no single ETCO2 level was found to be a reliable predictor of diagnosis.
  
  
  CONCLUSIONS
  ETCO2 levels for pulmonary edema/CHF patients differ significantly from those of asthma/COPD patients. However, no single ETCO2 level reliably differentiates between the two disease processes.
authors.affiliation: Department of Emergency Medicine, East Carolina University School of Medicine, Greenville, NC, USA.
authors.forename: L H
authors.initials: LH
authors.lastname: Brown
authors.forename: J E
authors.initials: JE
authors.lastname: Gough
authors.forename: R H
authors.initials: RH
authors.lastname: Seim
mesh_terms: D000328:Adult; D000368:Aged; D000402:Airway Obstruction / Q000150:complications* / Q000175:diagnosis; D001249:Asthma / Q000150:complications / Q000175:diagnosis; D001794:Blood Pressure / Q000502:physiology; D019296:Capnography; D002245:Carbon Dioxide / Q000378:metabolism; D016009:Chi-Square Distribution; D004417:Dyspnea / Q000175:diagnosis / Q000209:etiology*; D005260:Female; D005544:Forecasting; D006331:Heart Diseases / Q000150:complications* / Q000175:diagnosis; D006333:Heart Failure / Q000150:complications / Q000175:diagnosis; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000150:complications / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate / Q000502:physiology; D011446:Prospective Studies; D011654:Pulmonary Edema / Q000150:complications / Q000175:diagnosis; D013902:Radiography, Thoracic; D015203:Reproducibility of Results; D012119:Respiration / Q000502:physiology; D012131:Respiratory Insufficiency / Q000175:diagnosis / Q000209:etiology; D012135:Respiratory Sounds / Q000503:physiopathology; D013546:Sweating / Q000502:physiology; D013990:Tidal Volume; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide