Water infused surface protection for central venous catheters
Sutherland, David Wesley
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Central venous catheters (CVCs) are semi-permanent implants that provide vascular access for various life-saving procedures, despite increased patient risk due to high rates of thrombotic occlusion and biofilm formation. The majority of CVC complications are caused by fibrin sheath formation, initiated by protein adsorption on the device surface upon exposure to blood. Current solutions are passive and ineffective at preventing these failure modes and treatment options are limited and often harmful to the patient. This dissertation presents the development and characterization of an active fluid mechanics-based mechanism that reduces the resistance to flow, predictably prevents the adsorption of biologic material, and provides targeted delivery of active agents to prolong patency and reduce complication rates in clinical CVCs. Water Infused Surface Protection (WISP) is a replenishing core-annular flow created by infusing fluid across a porous lumen wall, forming a protective boundary layer at the CVC surface. A model benchtop device capable of creating the WISP flow in an in vitro setting was developed and validated. Validation was performed using lubrication theory to compare experimental results to an adapted core-annular Navier-Stokes solution and a CFD model. The validated in vitro device was used to demonstrate the ability of the WISP technology to reduce protein adsorption on a model CVC surface, as well as allow for characterization of additional WISP performance mechanics. These mechanics include the continued protection of the lumen surface over extended time scales, the delivery and increased efficiency of clinically relevant anticoagulants to the lumen surface, and the removal of pre-adsorbed material. To analyze the boundary layer stability while scaling the WISP technology to clinically relevant flow rates, a novel imaging and analysis technique was developed capable of visualizing micron scale flow patterns through opaque materials using x-ray microscopy. This technique was used to characterize the stability of the core-annular interface at clinical Reynolds numbers. Comparison of these results to blood flow experiments suggested the separation of blood from the CVC wall under these conditions. These results were used to design and fabricate a single lumen clinical WISP prototype CVC that demonstrated a 98% reduction in protein adsorption.
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