Non-invasive measurement method of blood hematocrit for management of extracorporeal circulation

Determination of blood volume is important for safer management of extracorporeal circulation apparatuses in detection of adverse events such as hypotension, bleeding and failure of a pump. It is known that the hematocrit depends on blood volume in an extracorporeal circulation. The purpose of this study is to develop a non-invasive and continuous hematocrit measurement method to determine blood volume for safer management of extracorporeal circulation apparatuses, and to verify the effectiveness in in-vitro blood experiments. We have developed an optical measurement method which corrects measurement errors using dual wavelength and detector model without considering an isosbestic point of red blood cell and plasma. In addition, we have improved the proposed method by maximizing the difference of optical path lengths. Based on those methods, a measurement system has been developed. In in-vitro experiments, the optimal couple of emitter-detector distances has been indicated by comparing indexes of optical path length in each emitter-detector distance. Then, we have performed the hematocrit measurement experiment with change of blood flow. As a result, we could measure hematocrit with smaller errors on medical tubing. Therefore, we have confirmed the effectiveness of the developed method.