Development of Optical Sensing System for Noninvasive and Dynamic Monitoring of Thrombogenic Process

We developed a compact optical sensing system to monitor thrombogenic process noninvasively and dynamically by attaching a sensor on a blood circulating tubing. The system monitors the process for normal, erythrocyte aggregation, emboli, and thrombus formation stages with a continuously measured backscattered light. The system consists of an optical sensing unit, which has an 810-nm-wavelength chip light-emitting diode (LED) and a photodiode, and real-time monitoring software. The erythrocyte aggregation is verified by using the baseline transition of optical intensity, which is influenced by the apparent low number of red blood cells in erythrocyte-aggregated situation. Meanwhile, the emboli are evaluated by counting light-detected microembolic signals (LMES) induced by the flowing emboli. The performance of the system was evaluated using in vitro experiments with eight bovine blood samples. We performed optical sensing during thrombogenic process, which was intentionally generated by controlling the ratio of sodium citrate and calcium chloride solution. The activated whole blood clotting time (ACT) has gradually decreased in the process. The optical baseline transition has continuously increased at the beginning. After the increasing stopped, the LMES was observed. Finally, we found thrombus inside the mock-up circuit. As a result, we confirmed that our system is capable of monitoring the thrombogenic process noninvasively and dynamically.