(IP093) Benchtop Model for In Vitro Verification and Validation of Blood Velocity Monitoring Devices

Objectives: Blood velocity measurements are a critical tool in vascular surgery. Technology is advancing beyond standard measurements obtained in the vascular laboratory by ultrasound to novel devices for patients to use at home or implantable devices. Development of these technology platforms requires extensive benchtop testing prior to in vivo testing. The aim of this study is the development of a benchtop model that can replicate the rheology of blood flow permitting use as a research, validation or training tool.

Methods: Bypass graft phantoms with increasing levels of axisymmetric stenosis (0%, 40%, 65%, 75%) were designed using computer aided design software (SolidWorks Corporation, Waltham, MA) and fabricated in Onyx using additive manufacturing (3D Markforged). Phantoms were then embedded in gelatin for ultrasound compatibility. Subsequently, phantoms were incorporated into a circuit attached to a peristaltic pump and instrumented for pressure proximal and distal, and flow proximal to the stenosis. Ultrasonography was used to derive velocities using pulse wave doppler. Data was collected in Lab Chart (ADinstruments, Sydney) and post processing was done with Python 3.12 (Python Software Foundation, Wilmington, Delaware).

Results: The slope of the Pressure-Flow relationship increased dramatically with increasing stenosis degree, consistent with the expected increase in resistance. Regardless of stenosis degree, the Pressure-Flow relationship was approximately linear at flows < 100 mL/min, indicating laminar flow. At higher flow rates, a non-linear increase was observed, suggesting onset of turbulence. With regards to duplex ultrasound, images were successfully obtained through gelatin and the print material, permitting the measurements of peak flow velocities that correlated with the pump flow rate.

Conclusions: We have successfully developed a benchtop model that incorporates gelatin impregnated 3D printing, blood mimicking fluid, and ultrasound capabilities, that can be further used to recapitulate a number of rheological perturbations. This model is suitable for research, validation and training, as it closely mimics physiological properties of the blood and the vascular anatomy.