Evaluation of Differences between PaCO2 and ETCO2 by Age as Measured during General Anesthesia with Patients in a Supine Position

Objective. The aim of this study was to evaluate the arterial to end-tidal partial pressure gradient of carbon dioxide according to age in the supine position during general anesthesia. Methods. From January 2001 to December 2013, we evaluated 596 patients aged ≥16 years who underwent general anesthesia in the supine position. The anesthetic charts of these 596 patients, all classified as American Society of Anesthesiologists physical status I or II, were retrospectively reviewed to investigate the accuracy of PaCO2 and ETCO2. Results. The a-ETCO2 was  mmHg for patients aged 16 to <65 years and  mmHg for patients ≥65 years. The a-ETCO2 was  mmHg for patients aged 16 to 25 years,  mmHg for patients aged 26 to 35 years,  mmHg for patients aged 36 to 45 years,  mmHg for patients aged 46 to 55 years,  mmHg for patients aged 56 to 64 years,  mmHg for patients aged 65 to 74 years, and  mmHg for patients aged 75 to 84 years. Conclusion. The arterial to end-tidal partial pressure gradient of carbon dioxide tended to increase with increasing age.