Objective：To compare the accuracy of end - tidal carbon dioxide partial pressure（PETCO2）and transcutaneous carbon dioxide partial pressure（PTCCO2）in predicting arterial carbon dioxide pressure（PaCO2）in patients undergoing retroperitoneoscopic urologic surgery. Methods：Fifty patients undergoing retroperitoneoscopic urologic surgery under general anesthesia were included. Values of PaCO2，PETCO2，and PTCCO2 were measured before and 30，60，90 min after insufflation. The differences between PaCO2-PETCO2 and PaCO2-PTCCO2 were calculated. Correlation and regression analysis were conducted between PaCO2 and PETCO2，as well as between PaCO2 and PTCCO2. Bland-Altman analysis was used to assess the agreement between PaCO2 and the other two variables. Results：The absolute differences of PaCO2-PETCO2 and PaCO2-PTCCO2were（13.20 ± 4.43）mmHg and（4.35 ± 2.56）mmHg，respectively（P ＜ 0.05）. The correlation coefficient between PaCO2 and PETCO2was 0.79（r 2 =0.62，P ＜ 0.001），and between PaCO2 and PTCCO2 was 0.91（r 2 =0.83， P ＜ 0.001）. The 95% limits of agreement between PaCO2 and PETCO2 were 4.53 to 21.88 mmHg and between PaCO2 and PTCCO2 were -3.18 to 10.48 mmHg. Conclusion：PTCCO2 monitoring improves the accuracy of estimating PaCO2 in patients undergoing retroperitoneoscopic urologic surgery.
