Bubble Counter for Measurement of Air Bubbles During Thoracic Stent-Graft Deployment in a Flow Model

BACKGROUND: The aim of our study was to describe and validate the use of a bubble counter in an aortic flow model assessing the distribution of air bubbles in the supra-aortic vessel during thoracic stent-graft deployment.

MATERIALS AND METHODS: In an aortic flow model made by glass, identical tubular thoracic stent grafts (Zenith TX2 ProForm; Cook Medical, Bjaeverskov, Denmark) were deployed distal to the left subclavian artery. Four steps were defined during deployment: (1) introduction of the stent graft in the arch; (2) deployment of the stent graft; (3) proximal release of the stent graft; and (4) retrieval of the introduction system. On both sides, the common carotid and the vertebral artery were connected together, and the air bubbles were measured with one bubble counter probe per side. The number of air bubbles, as well as their size and distribution, is analyzed during these four steps for the left and right sides with a bubble counter.

RESULTS: Ten thoracic stent grafts were included in the study. The total number of air bubbles measured during all steps was significantly higher on the left side (1091 ± 255 versus 545 ± 288, P < 0.00001). During the third step, significantly higher numbers of bubbles were observed on the left side (P = 0.0000001) compared with the right side. The analysis of all bubbles by size revealed that a higher number of bubbles ranged 100-200 μm (P < 0.02) and 200-300 μm (P < 0.03) on the left side. Small bubbles were observed during all steps of deployment, whereas large bubbles appeared more commonly during the second and third steps.

CONCLUSIONS: A significant number of air bubbles are released during deployment of tubular thoracic stent grafts distally of the left subclavian artery in an aortic flow model. The distribution of air bubbles is bilateral with a higher number of air bubbles released on the left side.