The role of carbon dioxide insufflation in colonoscopy: a systematic review and meta-analysis

Background and study aims: Insufflation of the intestinal tract, usually with room air, is necessary to improve visualization during colonoscopy. However, most patients complain of bowel distension and abdominal pain afterwards. Recently, carbon dioxide (CO2) rather than air insufflation has been used. We aimed to evaluate the efficiency, safety, and comfort of colonoscopy CO2 insufflation, with systematic review and meta-analysis of published randomized controlled trials (RCTs). Methods: Databases including PubMed, EMBASE, the Cochrane Library, the Science Citation Index, and important meeting abstracts were searched and evaluated by two reviewers independently. Results: Nine RCT studies involving 1577 patients were analyzed. There was significant heterogeneity for some major results; we analyzed these using a random-effects model. Meta-analysis showed fewer patients with abdominal pain in the CO2 group during the procedure (relative risk [RR] 0.77, 95% confidence intervals [CI] 0.62-0.96), and post procedure at 1 hour (0.26, 0.16-0.43), 6 hours (0.36, 0.20-0.64), and 24 hours (0.53, 0.31-0.91). The number needed to treat (NNT) during the procedure was 7; post procedure, the NNT at 1 hour was 2, at 6 hours it was 3, and at 24 hours it was 12. Compared with air, CO2 insufflation was associated with less passage of flatus post procedurally, at 1 hour (RR 0.09, 95 % CI 0.03-0.24) and 6 hours (0.30, 0.14-0.62). There were no significant differences between the two groups regarding safety, gas volume, and cecal intubation rate. Conclusions: Insufflation with CO2 in colonoscopy could decrease abdominal discomfort during and following the procedure, without any additional adverse reactions, warranting routine clinical use.