Concordance between capnography and capnia in adults admitted for acute dyspnea in an ED

Am J Emerg Med. 2010 Jul;28(6):711-4. doi: 10.1016/j.ajem.2009.04.028. Epub 2010 Mar 25.


Background: End-tidal carbon dioxide pressure (etCO(2)) is widely used in anaesthesia and critical care in intubated patients. The aim of our preliminary study was to evaluate the feasibility of a simple device to predict capnia in spontaneously breathing patients in an emergency department (ED).

Patients and methods: This study was a prospective, nonblind study performed in our teaching hospital ED. We included nonintubated patients with dyspnea (> or =18 years) requiring measurement of arterial blood gases, as ordered by the emergency physician in charge. There were no exclusion criteria. End-tidal CO(2) was measured by an easy-to-use device connected to a microstream capnometer, which gave a continuous measurement and graphical display of the etCO(2) level of a patient's exhaled breath.

Results: A total of 43 patients (48 measurements) were included, and the majority had pneumonia (n = 12), acute cardiac failure (n = 8), asthma (n = 7), or chronic obstructive pulmonary disease exacerbation (n = 6). Using simple linear regression, the correlation between etCO(2) and Paco(2) was good (R = 0.82). However, 18 measurements (38%) had a difference between etCO(2) and Paco(2) of 10 mm Hg or more. The mean difference between the Paco(2) and etCO(2) levels was 8 mm Hg. Using the Bland and Altman matrix, the limits of agreement were -10 to +26 mm Hg.

Conclusion: In our preliminary study, etCO(2) using a microstream method does not seem to accurately predict Paco(2) in patients presenting to an ED for acute dyspnea.

Publication types

  • Controlled Clinical Trial

MeSH terms

  • Adult
  • Aged
  • Blood Gas Analysis
  • Capnography / instrumentation*
  • Dyspnea / blood*
  • Dyspnea / etiology
  • Emergency Service, Hospital*
  • Feasibility Studies
  • Female
  • Humans
  • Hypercapnia / blood
  • Hypercapnia / diagnosis*
  • Hypercapnia / etiology
  • Lung Diseases, Obstructive / blood*
  • Lung Diseases, Obstructive / complications*
  • Lung Diseases, Obstructive / diagnosis
  • Male
  • Middle Aged
  • Prospective Studies
  • Tidal Volume