It has been reported that carbon dioxide (CO2) insufflation can reduce patient pain and abdominal discomfort during and after colonoscopy. Its safety and efficacy during colonoscopy even under sedation has been already assessed in some earlier trials. Air insufflation is still the standard method, however, because of a lack of suitable equipment and continued technical improvement in colonoscopy.

In laparoscopic surgery, CO2 insufflation is widely applied and safely used with the patient under general anesthesia. CO2 insufflation is also applied for CT colonography for reduction of discomfort during or after procedure.2 During endoscopic procedure for colorectal neoplasia resection, however, long procedural time may increase not only the degree of discomfort during and after the procedure but also the risk of perforation. In addition to laparoscopic surgery, CO2 insufflation has also been applied to other endoscopic procedures. Saito et al reported the application of CO2 insufflation in Endoscopic submucosal dissection (ESD) of colorectal neoplasia in a prospective study in which their average procedural time using CO2 insufflation was 90 minutes under conscious sedation with average of 5.6 mg of midazolam. When compared with control group using room air, statistically negligible difference of pCO2 was observed with significant difference in abdominal discomfort.6 Screening colonoscopy, which can be completed within 15 minutes if no lesion being detected, requires high screenee satisfaction so as to improve patient compliance. In the setting of colonoscopy after positive FOBT, the attendance rate for secondary colonoscopy was around 60 to 70 % according to the data demonstrated in previous RCT and population-based studies. With application of CO2 insufflation, further improvement of patient compliance can be anticipated.

This study aims to investigate whether use of CO2 insufflations can reduce examinee discomfort in comparison with air.