Effects of carbon dioxide insufflation during direct cholangioscopy on biliary pressures and vital parameters: a pilot study in porcine models

Background and Aims Direct per-oral cholangioscopy allows endoscopic visualization of the biliary tract. Insufflation with carbon dioxide (CO 2 ) is an alternative to saline solution irrigation during direct cholangioscopy. There are no data on maximal CO 2 insufflation in direct cholangioscopy without causing biliary barotrauma or fatal gas embolism. We aimed to evaluate the safety of increasing CO 2 insufflation in direct cholangioscopy without causing biliary barotrauma or fatal gas embolism. Methods This was an in vivo animal study. Four domestic pigs, under general endotracheal anesthesia, were used. The first animal was used to validate the feasibility of direct cholangioscopy and biliary pressure measurements, after which all animals underwent laparotomy, insertion of a pressure transducer in the cystic duct, and direct transpapillary placement of the cholangioscope. The common bile duct (CBD) and cystic duct were ligated to contain the instilled gas and exclusively expose the biliary tree. Insufflation of CO 2 started at 200 mL/min and was continuously increased until there was evidence of bile duct rupture (as measured by a drop in intraductal pressures) or instability of vital signs (hypotension, bradycardia, bradypnea, O 2 desaturation). Necropsy was performed on all animals to assess the liver and biliary system for evidence of barotrauma. Results CO 2 was insufflated up to 8 L/min without causing bile duct rupture or instability in vital signs despite increasing CBD pressure with insufflation. There was significant correlation between CO 2 flow with partial pressure of CO 2 in arterial blood (PaCO 2 ) (coefficient, 0.96-1.00; P 2 (EtCO 2 ) (coefficient, 0.94-1.00; P 2 did not correlate with the amount of CO 2 flow. There was no evidence of hepatic or biliary barotrauma on necropsy. Conclusions This pilot experience in porcine models suggests that CO 2 insufflation is safe for direct cholangioscopy and does not result in biliary barotrauma or vital signs instability.