Impact of carbon dioxide insufflation and water exchange on postcolonoscopy outcomes in patients receiving on-demand sedation: a randomized controlled trial

Background and Aims Water exchange (WE) is the least painful insertion method during colonoscopy. Its impact on postcolonoscopy discomfort has not been well-described. Carbon dioxide (CO 2 ) insufflation consistently reduced postcolonoscopy discomfort. We compared postcolonoscopy outcomes of various combinations of insertion and withdrawal techniques (insertion-withdrawal modality): WE-CO 2 , WE-air insufflation (WE-AI), and CO 2 -CO 2 . Methods A total of 240 patients undergoing on-demand sedation diagnostic colonoscopy were randomized to WE-CO 2 (n = 79), WE-AI (n = 80), CO 2 -CO 2 (n = 81), with postprocedural data collected up to 24 hours. The primary outcome was postcolonoscopy bloating. Other postcolonoscopy outcomes included pain scores, flatus and incontinence episodes, toilet use, interference with normal activities, patient satisfaction, and patient willingness to repeat the procedure. Results Demographic and procedural data were comparable. Compared with WE-AI, WE-CO 2 and CO 2 -CO 2 resulted in significantly less bloating (all P P values ranged from .008 to  P values ranged from .003 to  2 resulted in less interference with same-day activities compared with WE-AI ( P  = .043). The differences in postprocedural outcomes were significant, but the magnitude was small. Patient satisfaction and willingness to repeat the procedure were high and comparable among groups. WE was the least painful insertion technique ( P Conclusions The combination WE-CO 2 appears to be the optimal choice to decrease pain during the examination and to reduce bloating and other undesired procedural outcomes afterward. If a CO 2 insufflator is already available, it seems advisable to adopt the combination WE-CO 2 . In the absence of a CO 2 insufflator, the cost effectiveness of the addition of withdrawal CO 2 to WE in diagnostic and nondiagnostic settings needs to be critically assessed. (Clinical trial registration number: NCT02409979.)