Carbon dioxide insufflation attenuates parietal blood flow obstruction in distended colon - Potential advantages of carbon dioxide insufflated colonoscopy

Background: Bowel distention after colonoscopy has been considered as a cause of blood flow disturbance. Carbon dioxide (CO2) with its higher absorbability and vasodilating effect, may reduce parietal blood flow disturbance of distended colon when used for intraluminal insufflation instead of air. The purpose of this study was to assess parietal blood flow of the colon distended with intraluminal air/CO2 insufflation. Methods: A 5-cm segment of rat colon was insufflated with either air (air group) or CO, (CO, group). Two insufflation methods were employed: temporary insufflation Lip to an intraluminal pressure of 60 mmHg and continuous insufflation at a pressure of 5, 15, and 30 mmHg. Bowel distention and parietal blood flow measured by laser Doppler imaging were evaluated. Results: For temporary insufflation, bowel distention was prolonged in the air group, whereas it rapidly resolved in the CO, group. Parietal blood flow decreased in both groups; however, it recovered within 5 min in the CO2, group. For continuous insufflation, under 5 mmHg insufflation, blood flow decreased in the air group, whereas it increased in the CO2 group. Blood flow decreased in both groups under 15 mmHg insufflation; however, it decreased less in the CO, group. There was a reverse relationship between insufflation pressure and blood flow difference. Inhibition of nitric oxide synthase, ATP-sensitive K+ channel, or heme oxygenase was ineffective against a CO2-induced increase in blood flow. Conclusion: CO, insufflation preserved parietal blood flow not only by rapid resolution of bowel distention but also by its potential vasodilative effect.