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Biomedical subjects

I Fujimasa

Publications and source records attributed to I Fujimasa.

At least 19 recordsLinked to original sources
PubMed1991

[Artificial hearts--toward future technologies].

What are the most essential technologies for developing the implantable artificial heart in future? The first is the development of autonomic and dispersed micro actuators for acting as sarcomeres of the heart muscle. An electric motor driven artificial heart transmitted the power with belts had been developed as a preliminary mechanism. A micro actuation using noise energy has been developed for simulating the structure and the function of striate-muscle sarcomeres. The chemical energy conversion mechanism must be applied instead of the conventional electro-mechanical mechanisms, when we implant the total artificial heart permanently. As a implantable assisted artificial heart using tentatively, we have developed an axial flow pump system. The pump system acts as a systemic and a pulmonary pump produced pulsatile flow switching an axial pump output. The second is the search of biocompatible materials, which do not only mean blood compatibility but also tissue compatibility. The great masses in chest cavity have inevitably occurred infection. The autonomic and dispersed control system is the third item. We have developed a jellyfish valve with low fluid dynamical resistances for improving the pump dynamic characteristics.

Heart, Artificial↗
PubMed1989

[Automatic control of total artificial heart to simulate the hemodynamics under natural heart circulation].

We developed control system of total artificial heart (TAH) during exercise simulating the circulatory response of natural heart. The following procedures were taken to develop this system. 1) Measurement of hemodynamics and physical activity rate (PAR) of natural heart goats during treadmill exercise. 2) Estimation of cardiac output from PAR using a non-linear model. 3) Development of a pneumatic artificial heart (AH) driver with high speed controllability and a control unit to deliver CO calculated from PAR beat by beat. 4) Evaluation of the physiological condition of the TAH goat during exercise controlled by this system. Using this control method, CO of TAH goats was similar to that of natural heart goats during treadmill exercise. Hypertension was observed during exercise. This hypertension was considered to be derived from two causes. One was high inflow and outflow resistance of cannulae between AH pump and living body. The other was the disorder of peripheral circulatory control mechanism in TAH animal. Such as increased sympathetic activity, insufficient secretion of atrial natriuretic polypeptide (ANP) and decreased sensitivity of peripheral circulatory system with ANP.

Animals↗
PubMed1987

Research and development on total artificial heart in University of Tokyo.

The research and development on the total artificial heart (TAH) in the University of Tokyo can be divided chronologically into the three stages, i.e., the first stage (1959-1970); trial and error stage to find appropriate hardwares, the second stage (1970-1985); software stage to find how to control pneumatic TAH and to manage the animals, and the third stage (1985- ); final goal to develop implantable TAH for animal and human. This paper reviews the process of research and development in each stage.

Animals↗
PubMed1984

Quantitative approach to determine the application time of the left ventricular assist device.

This study was designed to establish a method for determining the optimal time of the application of the left ventricular assist device from the viewpoint of the metabolism of the vital organs. Quantitative systemic low flow states were made utilizing goats with total artificial hearts. During these experiments, arterial lactate and pyruvate values were sequentially measured. The behavior of anaerobic metabolism during low cardiac output states and in the recovery process following normalization of the cardiac output was quantitatively described and evaluated. The experimental results are summarized as follows: If a time when the decay of arterial lactate ceases at a level above the normal level by greater than 30 mg/dl is observed despite the use of intraaortic balloon pumping, that time is the exact optimal time for application of the left ventricular assist device. There is a great possibility that circulatory failure will be irreversible if left ventricular assist pumping is not initiated before the arterial lactate value increases to greater than or equal to 140 mg/dl. The method of evaluating the alteration of anaerobic metabolism described in this study is useful for determining the application time of the left ventricular assist device.

Animals↗
PubMed1984

How can the total artificial heart (TAH) patient be mobile and enjoy his life with an air driven system?

Two air driven VAD and TAH driving and control units were developed for clinical use, one to be installed at the bedside and the other to be installed in an electric wheelchair. The reliability and safety of the bedside unit were shown by long-term TAH experiments using animal models and by clinical application in conjunction with VAD. A TAH goat was safety taken on a 12 hr trip to a destination 550 km away while attached to a bedside unit. The driving and control functions of the wheelchair unit were found to be practically identical to those of the bedside unit.

Animals↗