Abstract: Objectives：To appraise whether arterial partial pressure of end—tidal carbon dioxide(PetCO2) can accurately reflect the value of arterial partial pressure of carbon oxide(PaCO2) during prolonged laparoscopic procedure and the correlation between them. Methods：40 ASA physical status I and II patients，without cardio-pulmonary dysfunction preoperatively，scheduled for elective urologic laparoscopic procedures, pneumo-peritoneum course lasted over 3 hours. After conventional induction and tracheal intubation, the values of PetCO2 and PaCO2 were observed and recorded at post-intubation, at 1, 2 and 3 hr. point post-pneumoperitoneum, right half hr. at the end of pneumo-peritoneum. Then, regression formula was built in correlation between PetCO2 and PaCO2 at different time-point. Results: A remarkable positive correlation between PetCO2 and PaCO2 was found at the point of post-intubation, 1 and 2 hr. post-pneumoperitoneum, and half hr. at the end of post-pneumoperitoneum（r=0.966，P<0.01）. But as time prolonged, the correlation between PetCO2 and PaCO2 changed badly, there was an increase in the values of both PetCO2 and PaCO2, but the increase range was much higher in PaCO2 than that of in the PetCO2 （r=0.585，P< 0.01）.Conclusions: There was a better correlative relationship in monitoring results between PetCO2 and PaCO2 during the laparoscopic procedure of urology under pneumoperitoneum with carbon oxide, which can correctly reflect the tendency of change of PaCO2 under the condition of pneumoperitoneum, that can meet clinical use, but the D-value increases and correlation went to bad between PetCO2 and PaCO2 as pneumoperitoneum duration prolonged. So,besides conventional monitoring PetCO2, respiratory parameters should be modulated in time according to the results of blood gas analysis in order to avoid hypercapnia when pneumoperitoneum duration lasted over 2 hours.

Key words: PetCO2, PaCO2, pneumoperitoneum, Urological laparoscopic surgery