The value of ETCO2 measurement for COPD patients in the emergency department

We aimed to determine the value of sidestream end-tidal carbon dioxide (SS-ETCO2) measurement in patients with chronic obstructive pulmonary disease (COPD) in the emergency department. Cross-sectional associations between ETCO2 and PaCO2 were examined in the study. This prospective cross-sectional study has been carried out over a 3-month period in a tertiary care university hospital emergency department with an annual census of 75 000 visits. During the study period, simultaneous SS-ETCO2 measurement using a Medlab Cap 10 sidestream capnograph was performed on every COPD patient requiring arterial blood gas analysis. The demographics, diagnosis, vital signs, laboratory test results and clinical outcomes of the patients were recorded. SS-ETCO2 measurement and arterial blood gas analysis were carried out on 118 patients. Mean arterial PCO2 levels were 43.24±14.73 and mean ETCO2 levels were 34.23±10.86 mmHg. Agreement between PCO2 and ETCO2 measurements was 8.4 mmHg and a precision of 11.1 mmHg.As there is only a moderate correlation between PCO2 and ETCO2 levels in COPD patients, ETCO2 measurement should not be considered as a part of the decision-making process to predict PaCO2 level in COPD patients.