Gas dynamics in CO2 angiography: in vitro evaluation in a circulatory system model

The use of carbon dioxide (CO2) as a vascular contrast agent has increased significantly since the introduction of digital subtraction angiography. To optimize the injection of CO2 for digital subtraction angiography, we evaluated the gas dispersion patterns from differing catheter designs, gas flow dynamics, and the influence of vessel size and inclination on luminal gas filling.

A circulatory system model was constructed and perfused with 36% glycerin solution at a rate of 1.08 to 1.13 liters per minutes (pulse rate 72 beats/minute, pressure 90-111 mm Hg). Fifty milliliters of CO2 was rapidly injected into the vascular tube of the model (diameter 6.4-15.9 mm) at an inclination of 0 degrees to 45 degrees via a catheter, and imaged digitally in a cross-table lateral projection. The dispersal patterns of gas bubbles from the halo, pigtail, and end-hole catheters were evaluated as well as the degree of luminal gas filling.

The halo and end-hole catheters produced continuous gas flow with homogeneous density. The pigtail catheter produced smaller bubbles with inhomogeneous density. Luminal gas filling was incomplete, with a residual fluid level posteriorly regardless of the size and inclination of the tube. At 0 degrees inclination, gas filling was greater with the 6.4-mm tube than with the 15.9-mm tube. With an inclination of 0 degrees to 15 degrees, gas filling was significantly improved for the larger tubes. On dispersal, CO2 bubbles rapidly coalesced and moved forward along the anterior aspect of the tube. The frontal motion of the bubble was parabolic in configuration.

The halo and end-hole catheters provide more homogeneous gas density than the pigtail catheter. Gas filling was incomplete regardless of catheter design, vessel size, or inclination. Inclination improves gas filling in vessels > 12.7 mm in diameter.