Abstract: Objective To investigate the correlation between arterial partial pressure of CO2 (PaCO2) and end expiratory tidal
partial pressure of CO2 (Pet-CO2) in morbidly obese patients during anesthesia for laparoscopic gastric bypass surgery.
Methods Forty morbidly obese patients with a body mass index (BMI) between 35 and 50 kg/m2 underwent laparoscopic
gastric bypass surgery under general anesthesia. PaCO2 and Pet-CO2 were measured after intubation and before induction of
pneumoperitoneum (T0), at 30 min (T1), 60 min (T2), and 120 min (T3) during pneumoperitoneum, and at 30 min (T4) and 60 min
(T5) after deflation. Results At each time point of measurement, Pet-CO2 was lower than PaCO2 in all the patients. PaCO2 and
Pet-CO2 were positively correlated before, during, and after pneumoperitoneum (P<0.05). At a moderate pressure of CO2
pneumoperitoneum (16 mmHg), the level of correlation between PaCO2 and Pet-CO2 at T1, T2, and T3 differed from that before
and after post-pneumoperitoneum. Conclusion PaCO2 and Pet-CO2 are closely correlated during a moderate CO2
pneumoperitoneum in morbidly obese patients undergoing laparoscopic gastric bypass surgery.