VALIDATION OF NON-INVASIVE CARDIOVASCULAR MONITORING SYSTEM MAKING USE Of THE TECHNOLOGY TO REALIZE THE ENVIRONMENT OF INNER HUMAN BODY AT OUTSIDE HUMAN BODY

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This study is concerned with the validation of recently developed three kinds of typical blood pressure measurement methods such as oscillometric auto blood pressure meter, wristwatch type blood pressure meter utilizing pulse wave traveling time and photoelectric pulse wave monitor to observe blood pressure over 24 hours. We mainly focused on the relation between pulse wave traveling time and the accuracy of actual blood pressure of human body. Therefore, we took account of the effect of boundary condition simulating real situation of human blood pressure measurement.First, we designed and machined an equipment to simulate precisely the behavior of the pressure pulsation and the vibration characteristics of blood vessel of an upper arm of a human body during blood pressure measurement which consists of flexible tube, piston-crank mechanism for driving pulse wave and head tank to maintain average blood pressure. Secondly, we measured various types of pulse waveform by changing resistance of a flexible tube and constrictions. Simultaneously, we developed computer code to simulate the behavior of the blood vessel precisely based on the physical model of the collapsible tube taking account of the effect of rigidity of the tube and boundary conditions. Validity of our program was checked by experimental data using silicon tube. Then, we applied this program to human blood vessels and we first succeeded in obtaining reasonable results which can explain the trend of measured results with human arteries.Furthermore, we succeeded in formulating the method of calculation concerned with fluid structure interaction between thin flexible structure and the flowing fluid where non-linearity of the fluid force is important, which gives us the physical interpretation of the role of nonlinearity in this problem.