A model study of vascular microbubble transport in pulsatile blood flow through bifurcating vessels

Abstract

The behavior of long gas bubbles suspended in liquid flowing through bifurcating vessel network was investigated experimentally and theoretically as a model of vascular bubble transport. This work is motivated by a developmental gas embolotherapy in which perflurocarbon microbubbles are selectively formed in vivo and subsequently lodge to occlude blood flow to tumors. The bubbles originate from encapsulated liquid droplets that are small enough to pass through capillaries, allowing intravenous injection. The homogeneity of tumor necrosis depends on the transport and lodging of emboli. A bench top experimental model was used to explore the effects of flow pulsatility, heart rate, gravity, and bifurcation roll angle on bubble splitting and lodging. A corresponding time‐dependent one‐dimensional theoretical model was also developed. At a bifurcation roll angle of 45‐degrees, the most distinct difference in splitting ratios between three physiologic frequencies (1, 1.5, 2 Hz) was observed. As roll angle increased, lodged bubble volume in the first generation channel increased while bubble volume beyond the second bifurcation proportionately decreased. The results elucidate the effects of pulsatile flow and suggest the potential of gas embolotherapy to occlude blood flow to tumors. These finding are also relevant to air embolism.This work was supported by NIH grant R01EB006476.