Carbon Dioxide Insufflation or Warm-Water Infusion Versus Standard Air Insufflation for Unsedated Colonoscopy: A Randomized Controlled Trial

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The increasing demand for colonoscopy has renewed the interest for unsedated procedures. Alternative techniques, such as carbon dioxide insufflation and warm-water infusion, have been advocated to improve patient tolerance for colonoscopy in comparison with air insufflation.


The aim of this study was to evaluate the benefits of carbon dioxide insufflation and warm-water irrigation over air insufflation in unsedated patients.


This study was a randomized, controlled trial.


This study was conducted at a nonacademic single center.


Consecutive outpatients agreeing to start colonoscopy without premedication were included.


Patients were assigned to either carbon dioxide insufflation, warm-water irrigation, or air insufflation colonoscopy insertion phase. Sedation/analgesia were administered on patient request if significant pain or discomfort occurred.


The primary outcome measured was the percentage of patients requiring sedation/analgesia. Pain and tolerance scores were assessed at discharge by using a 100-mm visual analog scale.


Three hundred forty-one subjects (115 in the carbon dioxide, 113 in the warm-water, and 113 in the air group) were enrolled. Intention-to-treat analysis showed that the proportion of patients requesting sedation/analgesia during colonoscopy was 15.5% in the carbon dioxide group, 13.2% in the warm-water group, and 25.6% in the air group (p = 0.04 carbon dioxide vs air; p = 0.03 warm water vs air). Median (interquartile range) scores for pain were 30 (10–50), 28 (15–50), and 46 (22–62) in the carbon dioxide, warm-water, and air groups (carbon dioxide vs air, p < 0.01; warm water vs air, p < 0.01); corresponding figures for tolerance were 20 (5–30), 19 (5–36), and 28 (10–50) (carbon dioxide vs air, p < 0.01; warm water vs air, p < 0.01).


This investigation was limited because it was a single-center study and the endoscopists were not blinded to randomization.


Carbon dioxide insufflation was associated with a decrease in the proportion of patients requesting on-demand sedation, improved patient tolerance, and decreased colonoscopy-related pain in comparison with air insufflation. The findings regarding warm-water irrigation confirmed the previously reported advantages, so that warm-water irrigation and carbon dioxide insufflation could represent competitive strategies for colonoscopy in unsedated patients.

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