The Difference between Arterial and End-tidal Carbon Dioxide Tension in Anesthetized Patients with Reduced Functional Residual Capacity

Park, Jung Won; Jung, Wol Sun; Kim, Jong Uk; Park, Pyung Hwan; Lee, Dong Myung

Abstract

BACKGROUND
It has been known that arterial carbon dioxide tension is 4~5 mmHg higher than end-tidal carbon dioxide tension in healthy adults during general anesthesia. But negative arterial to end-tidal PCO2 difference was reported in pregnant patients undergoing cesarean section. The purpose of this study was to elucidate the difference between arterial and end-tidal PCO2 in anesthetized patients with reduced functional residual capacity.
METHODS
90 patients were divided into 3 groups i.e. control group (n=30), obese group (n=20, body weight more than 20% greater than ideal weight), pregnant group (n=40). All patients had no cardiac or respiratory abnormalities and never smoked. Arterial blood gas analysis and measurement of end-tidal PCO2 were done 20 minutes after induction of anesthesia in control and obese group and just before uterine incision and 20 minutes after fetal delivery in pregnant group.
RESULTS
There were significant correlations between arterial and end-tidal PCO2 in all groups. The incidences of negative arterial to end-tidal PCO2 difference were 10% in control group, 40% in obese group, 42.5% in pregnant group (p<0.05).
CONCLUSION
From this study, it is concluded that patients with reduced functional residual capacity have more incidences of negativity than normal patients in the values of arterial to end-tidal PCO2 difference during general anesthesia. So when the tight control of PaCO2 is required in patients with reduced FRC, we recommend to measure PaCO2 for better anesthetic management.