Water exchange versus carbon dioxide insufflation in unsedated colonoscopy: a multicenter randomized controlled trial

Background and study aims: Compared with air insufflation, water exchange and carbon dioxide (CO₂) insufflation have been shown to reduce colonoscopy discomfort; however, head-to-head studies of the two methods are lacking. We aimed to compare water exchange and CO₂ insufflation directly with regard to pain during primary unsedated colonoscopy.

Methods: Patients willing to undergo unsedated colonoscopy at three centers in Norway and Poland were randomized 1:1 to water exchange or CO₂ insufflation during colonoscope insertion. Patients were blinded to group allocation. The primary end point was the proportion of patients reporting moderate or severe procedural pain on a 4-point verbal rating scale (VRS-4) at discharge. Secondary outcomes included the proportion of patients reporting no pain on the VRS-4.

Results: A total of 473 patients were randomized. A discharge pain questionnaire was completed by 226 of 234 patients (97 %) in the water exchange group versus 226 of 239 patients (95 %) in the CO₂ group (P = 0.37). Moderate or severe pain was reported by 47 of 226 patients (21 %) in the water exchange group versus 60 of 226 patients (27 %) in the CO₂ group (P = 0.15). No pain was reported by 100 of 226 patients (44 %) and 69 of 226 patients (31 %) in the water exchange and CO₂ groups, respectively (P = 0.003). On-demand sedation was used in 15 patients (6 %) in each group (P = 0.95).

Conclusions: There was no significant reduction in moderate or severe pain in a comparison of water exchange with CO₂ insufflation. The secondary outcome of no pain was significantly more frequent in the water exchange group. 

Clinical trials registry number: NCT01633333.

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