The use of carbon dioxide gas to displace flowing blood during angioscopy.

Carbon dioxide (CO2) gas is a safe and effective arterial contrast agent that images arteries by displacing blood. The use of CO2 gas to displace blood during angioscopy may improve intraoperative angioscopy and allow percutaneous angioscopy. To study this, 46 angioscopic evaluations in the femoral arteries of four dogs were done without inflow occlusion. The ability of CO2 gas to clear the flowing blood was compared to a high-pressure infusion of saline solution. Carbon dioxide gas successfully displaced flowing blood in 20 of 25 evaluations (80%) as compared to three of 21 evaluations (14%) with infusion of saline solution (p less than 0.0001). After the CO2 gas infusion was stopped, the image remained clear for 9 +/- 1 seconds. When saline was used, the image was clear only as long as the infusion was continued. The quality of clear images for the two media were similar through the eyepiece of the angioscope, but images observed through the motion picture camera had better contrast and depth of field in CO2 gas. The use of a CO2 gas infusion can clear the field of flowing blood without the risk of volume overloading and potentially allow performance of a successful percutaneous angioscopy.