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

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 (>= 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 ETCO2 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. (C) 2010 Elsevier Inc. All rights reserved.