William Arpin Bachelor of Science in Biomedical Engineering Thesis Portfolio

In our study, we aimed to develop a novel method for continuous and non-invasive monitoring of blood coagulation during open heart surgeries. The goal was to reduce the reliance on bolus heparin injections by providing real-time feedback on clotting status. Leveraging Doppler velocimetry, we created a mathematical model to visualize velocity profiles of blood flow through a model heart-lung machine—an essential component in cardiac surgery that redirects blood flow while allowing surgeons unobstructed access to the heart. Our proof-of-concept testing focused on demonstrating how velocity profiles become blunter as blood clots. We analyzed frequency shifts and phase shifts. The frequency shift—from 4.09 ± 0.62 MHz to 3.21 ± 0.11 MHz —supported Doppler principles, decreasing as blood moved away from the transducer. However, due to the wide bandwidth, the wall echo frequency was different from the expected 5 MHz of the transducer, and the shift was much larger than expected. It is believed that this issue stems from the large bandwidth of the pulser. Regarding phase shift, initial observations showed none. Yet, further investigation revealed that the discrepancy resulted from a low sampling rate. By comparing velocity profiles with simulated data at 40 times the sampling rate used in the experiment, we confirmed the presence of phase shifts. Our findings pave the way for integrating this innovative approach into routine cardiac surgery practice, enhancing patient safety and surgical outcomes.