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

RATIONALE AND OBJECTIVES. The use of carbon dioxide (CO2) as a vascular con trast agent has increased significantly since the introduction of digital s ubtraction angiography, To optimize the injection of CO2 for digital subtra ction angiography, we evaluated the gas dispersion patterns from differing catheter designs, gas flow dynamics, and the influence of vessel size and i nclination on luminal gas filling. METHODS. A circulatory system model was constructed and perfused with 36% g lycerin solution at a rate of 1.08 to 1.13 liters per minutes (pulse rate 7 2 beats/minute, pressure 90-111 mm Hg). Fifty milliliters of CO2 was rapidl y 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 digitall y in a cross-table lateral projection. The dispersal patterns of gas bubble s from the halo, pigtail, and end-hole catheters were evaluated as well as the degree of luminal gas filling. RESULTS. The halo and end-hole catheters produced continuous gas flow with homogeneous density. The pigtail catheter produced smaller bubbles with inh omogeneous density. Luminal gas filling was incomplete, with a residual flu id 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 w ith the 15.9-mm tube. With an inclination of 0 degrees to 15 degrees, gas f illing was significantly improved for the larger tubes. On dispersal, CO2 b ubbles rapidly coalesced and moved forward along the anterior aspect of the tube. The frontal motion of the bubble was parabolic in configuration. CONCLUSIONS. The halo and end-hole catheters provide more homogeneous gas d ensity than the pigtail catheter, Gas filling was incomplete regardless of catheter design, vessel size, or inclination. Inclination improves gas fill ing in vessels >12.7 mm in diameter.