Water Exchange and CO2 Insufflation with Abdominal Compression Device to Reduce Manual Assistance

For participants randomized to the intervention group, the back brace support belt, Maxbelt (me3 type, Nippon Sigmax Co., Tokyo, Japan), will be applied around the circumference of the lower abdomen. Five sizes of Maxbelt will be employed in this study. According to the manufacturer, the ultra small-size (XS-size) belt will be used in those patients with an abdominal circumference of 55 cm-65 cm, the small-size (S-size) belt will be used in those patients with an abdominal circumference of 65 cm-75 cm, the medium-size (M-size) belt will be used for a circumference of 75 cm-85 cm, the large-size (L-size) belt will be used for a circumference of 85 cm-95 cm, and the ultra large-size (XL-size) will be used for a circumference of 95 cm-105 cm. Once applied, participants will be asked to assess and confirm that the belt is fastened tightly but not uncomfortably.

The study coordinator will fit the sham device in a private bay alone with the patient. For participants randomized to the sham control group, a larger-sized Maxbelt with loose fitting will be used as a sham device. The L-size Maxbelt will be used in those patients with an abdominal circumference of 55 cm-71 cm, the XL-size Maxbelt will be used in in those patients with an abdominal circumference of 72 cm-88 cm, and the 2 XL-size Maxbelt will be used in in those patients with abdominal circumference 89 cm-105 cm.

In those patients assigned to the water exchange (WE) group, the air pump will be turned off during the insertion phase of colonoscopy, while the colon is irrigated with warm-to-touch distilled water or half normal saline using a flushing pump. The WE approach involves the simultaneous infusion of water to facilitate luminal expansion and suction of unclean water during insertion. Any encountered air pockets will be aspirated to ensure optimal WE maneuvers in salvage cleaning.