A comparison of transcutaneous and end-tidal measurements of CO2 tension in laparoscopic surgery

ABSTRACT

BACKGROUND: In laparoscopic surgery with pneumoperitoneum, end-tidal CO2 (PeTCO2) monitoring may inaccurately estimate PaCO2 due to ventilation/perfusion mismatch. This study assessed the clinical usefulness and accuracy of transcutaneous CO2 (PtCCO2) monitoring during laparoscopic surgery. METHODS: Thirty-two patients with ASA physical status 1 requiring laparoscopic surgery were recruited. We measured PaCO2, PeTCO2, and PtCCO2 before and 20 min after pneumoperitoneum. To compare differences in PeTCO2/PaCO2 and PtCCO2/PaCO2, we determined bias values (mean difference between values) and precision (standard deviation of bias) with a Bland-Altman plot and compared them with a Student's t-test. RESULTS: Bias and precision values of PeTCO2/PaCO2 and PtCCO2/PaCO2 were 6.6 +/- 2.0 mmHg, 1.2 +/- 2.8 mmHg before pneumoperitoneum and 8.5 +/- 2.8 mmHg, 2.1 +/- 4.5 mmHg 20 min after pneumoperitoneum. PtCCO2/PaCO2 differences were significantly smaller than PeTCO2/PaCO2 differences (P< 0.05). CONCLUSIONS: In laparoscopic surgery, PtCCO2 monitoring is more accurate than PeTCO2 monitoring for assessing PaCO2 levels.