Kiyoshi Naemura

Comparison of the closing dynamics of mechanical prosthetic heart valves.

To compare the closing dynamics of mechanical tilting disk prosthetic heart valves (OmniScience 25 [OS25], Medtronic-Hall 25 [MH25], Bjork-Shiley Monostrut 29 [BS29] and bileaflet valves (CarboMedics 29 [GM29]) in the mitral position, an x-ray high speed video camera (XHVC) and a mechanical mock circulator were used. From the continuous images taken with the XHVC, the starting point of closing and the period during closing (PDC) were measured. Pressures and flow rate were recorded at 500 Hz synchronously with the XHVC. A pressure difference across the valves at the onset of closing (dpc) was newly introduced to compare the closing response. Using 60 and 100 bpm, the following results were obtained: 1) the CM29 had less PDC and maximum backflow rate than the BS29; 2) the dpc and the PDC at 100 bpm were larger than those at 60 bpm; 3) the dpc of the MH25 was the lowest; and 4) the PDC of the CM29 was the shortest. With regard to the effect of valve design on closing dynamics, it was shown that: 1) less momentum of inertia of the occluder and disk traveling angle resulted in lower dpc and shorter PDC, and 2) the higher the dpc and the PDC became, the larger the maximum backflow rate that was generated, and 3) low final closing speed will be achieved for small disk travelling angle ASAIO Journal 1997;43:M401-M404.

Development of a Wearable Muscle Sound Sensing Unit and Application for Muscle Fatigue Measurement

This chapter presents the development of a new wearable muscle sound sensing unit for the core device of the wearable information system for human healthcare (WISH) and evaluation of its ability to sense muscle fatigue in daily life. Muscle sound produces a micro-vibration, which can be measured on skin surface during skeletal muscle contraction. Muscle sound as well as electrocardiogram and body acceleration can be measured simultaneously. Fatigue of the biceps brachii after exhaustion due to isometric contraction was examined as an application for muscle sound sensing in daily life. Amplitude of muscle sound is too small to measure during dynamic motion like arm swinging or walking. Body acceleration becomes noise for muscle sound sensing. Subtraction of two acceleration sensors is thought to be effective for noise reduction. Future study will be performed in order to construct a personal area network composed of wireless sensors that will process signals using a 1/f fluctuation of muscle sound.