Can mainstream end-tidal carbon dioxide measurement accurately predict the arterial carbon dioxide level of patients with acute dyspnea in ED.

OBJECTIVE This study was designed to determine whether the mainstream end-tidal carbon dioxide (ETCO2) measurement can accurately predict the partial arterial carbon dioxide (Paco2) level of patients presented to emergency department (ED) with acute dyspnea. METHODS This prospective, observational study was conducted at a university hospital ED, which serves more than 110 000 patients annually. Nonintubated adult patients presented with acute dyspnea who required arterial blood gas analysis were recruited in the study for a 6-month period between January and July 2010. Patients were asked to breathe through an airway adapter attached to the mainstream capnometer. Arterial blood gas samples were obtained simultaneously. RESULTS We included 162 patients during the study period. The mean ETCO2 level was 39.47 ± 10.84 mm Hg (minimum, 19 mm Hg; maximum, 82 mm Hg), and mean Paco2 level was 38.95 ± 12.27 mm Hg (minimum, 16 mm Hg; maximum, 94 mm Hg). There was a positive, strong, statistically significant correlation between ETCO2 and Paco2 (r = 0.911, P < .001). The Bland-Altman plot shows the mean bias ± SD between ETCO2 and Paco2 as 0.5 ± 5 mm Hg (95% confidence interval, -1.3165-0.2680) and the limits of agreement as -10.5 and +9.5 mm Hg. Eighty percent (n = 129) of the ETCO2 measurements were between the range of ±5 mm Hg. CONCLUSION Mainstream ETCO2 measurement accurately predicts the arterial Paco2 of patients presented to ED with acute dyspnea. Further studies comparing mainstream and sidestream methods in these patients are required.