Automated Partial Occlusion for Truncal Hemorrhage Control

Current REBOA solutions occlude the vessel by inflating a balloon internally and creating a seal against the endothelium. By partially deflating the balloon, a reduced flow state can be accomplished to allow perfusion of distal tissue and mitigate ischemic injury, but this has been difficult to manage. Fluid dynamics show that flow restriction through an orifice is linearly proportional to its cross-sectional area. As the cross-sectional area doubles, so does the flow. However, the cross-sectional area of a circle is exponentially proportional to its radius, so small changes in diameter of a fully inflated REBOA balloon cause extreme changes in flow. Due to the compliance of the balloon and vessel wall, this makes the flow rate extremely difficult to manage at high inflation volumes (i.e. the low flow rates desired in these scenarios). Our solution changes the locus of flow control from the external surface of the occluding balloon to an interior lumen created by using a toroidal balloon. This provides higher sensitivity of flow control at lower flow rates. During Phase I, we validated the performance of the toroidal balloon concept and demonstrated its ability to maintain traction during low flow conditions, and provide highly granular flow control. We prototyped an automatic flow control system and GUI, which maintained specified flow rates within 50mL/min 88% of the time under test. We propose to refine and improve this system in Phase II, including modification of the current controller to operate in austere conditions, integration of physiologic biomarker status sensors, and confirmation of accurate performance in large animal (porcine) models.