A Continuous, Real-Time Coagulation State Monitor for ECMO Patients

For patients undergoing extracorporeal membrane oxygenation (ECMO), clot formation is a critical complication requiring high-risk circuit changes. Blood tests used to assess clotting risk may be drawn only four times a day, potentially missing key information that could inform physician intervention. To mitigate these risks, we designed a device that integrates ultrasound imaging and impedance sensing for continuous, real-time monitoring of blood coagulability (the blood's likelihood to clot). Our design features a tubing adaptor housing two gold probes and an etched region containing a safe concentration of kaolin, a coagulation promoter, which localizes small-scale clot formation in a single detectable region. An ultrasound probe attached to the adaptor captures images at this location for further processing by a computer vision image segmentation algorithm that tracks changes in clot thickness over time. Concurrently, an impedance sensor measures resistive and capacitive changes in the blood during coagulation using the gold probes. The ac voltage input is minimized to prevent electrochemical reactions or shock. The output signal is filtered and analyzed using a lock-in amplifier to extract precise impedance changes that show preliminary correlation with coagulation blood test markers. By integrating these sensors, our system demonstrates preliminary real-time, in-circuit coagulation monitoring, making strides toward overcoming the current limitations of intermittent blood testing with the ultimate goal of improving patient safety in ECMO therapy.