Objective The total enteroscopy rate of single-balloon enteroscopy (SBE) using air insufflation is not satisfactory, and whether carbon dioxide (CO₂) insufflation increases the total enteroscopy rate of SBE is unknown. This randomised controlled trial aimed to determine whether CO₂ insufflation facilitates the intubation depth and total enteroscopy rate of SBE.

Design A total of 214 eligible patients referred for SBE were randomised to receive either air or CO₂ insufflation, and included in the intention-to-test (ITT) analysis. In addition, 199 patients in whom enteroscopy was completed were included in the per-protocol (PP) analysis. Both the patients and endoscopists were blinded, and the intubation depth and total enteroscopy rate were defined as the primary outcomes.

Results The CO₂ group showed a superiority of intubation in the ITT analysis (oral route: 323.8±64.2 vs 238.3±68.6 cm; anal route: 261.6±74.2 vs 174.7±62.1 cm, both p<0.001), and the total enteroscopy rate (34.9% vs 17.6%, p=0.006). Similar results were obtained in a PP analysis for both outcomes. In addition, in the PP analysis, the addition of circumference after the procedure was less in the CO₂ group (0.8±0.6 vs 3.3±1.8 cm, p=0.005) for the oral route. No serious complications were reported. The overall percentage of procedures with significant pathological findings was 52.8%; the rates were 58.5% and 47.2% (p=0.100, ITT analysis) in the CO₂ and air groups, respectively.

Conclusions CO₂ insufflation improves the intubation depth and total enteroscopy rate in SBE with a good safety profile and acceptability compared with that of air, and thus is recommended for clinical utilisation.

Trial registration number ClinicalTrial.gov identifier: NCT01758900.