Biomedical subjects

Tatsuo Tsutsui

Publications and source records attributed to Tatsuo Tsutsui.

8 recordsLinked to original sources

PubMed2005

The hemolytic characteristics of monopivot magnetic suspension blood pumps with washout holes.

The hemolytic characteristics of monopivot magnetic suspension blood pumps as a function of impeller washout hole configuration and female pivot shape are observed. The pump impellers are designed with three washout hole configurations for blood circulation, and four female pivot shapes to reduce blood stagnation and to enhance antithrombogenicity. The hemolytic characteristics of the monopivot pumps were observed to be better than those of a currently available commercial centrifugal blood pump, BP-80, and changed to be nearly equal when the female pivot shape was changed. This indicates that hemolysis in monopivot pumps is mainly caused by shear stress between the male and female pivots.

Animals↗

PubMed2004

Resonant frequency control for artificial heart using online parameter identification.

To develop effective medical care and therapeutic control using an artificial heart, a new control method has been developed. This new method can control the artificial heart effectively and can adapt to internal physiological behavior using measured physiological data; aortic pressure, aortic flow, and pump flow. This method consists of first, a second-order physiological model, which represents the internal physiological behavior by a mathematical equation; and second, an estimation method, which can identify the physiological parameters; aortic inertia, aortic resistance, aortic compliance, and peripheral resistance by a parameter identification method. It can then calculate the resonant frequency as the control signal for the artificial heart from the identified physiological model. To confirm the effectiveness, the proposed method was evaluated in a computer simulation study. This evaluation showed that the new method could estimate the physiological parameters and the resonant frequency within a 10% error. The impedance of the systemic circulation could also be reduced by this method.

Algorithms↗

PubMed2004

The most profitable use of flow visualization in the elimination of thrombus from a monopivot magnetic suspension blood pump.

The purpose of this study was to eliminate fluid dynamic causes of thrombus formation for the monopivot magnetic suspension centrifugal pump under development with the aid of flow visualization as an indirect measurement tool for animal experiments. The formation of thrombus observed in early animal experiments was successfully overcome by combining the multiple washout holes at the center into a single hole, optimizing the hole diameter, and eliminating the pivot gap. Flow visualization was used to optimize the washout hole diameter influencing the flow around the pivot. In animal experiments flow visualization showed that the contours of thrombus corresponded to shear rates of 300 s(-1) or 1300-1700 s(-1). It was found that flow visualization is a useful technique to predict locations where low shear thrombi form and to optimize the pump design in the development stage.

Animals↗

PubMed2003

Tsukuba remote monitoring system for continuous-flow artificial heart.

In order to make long-term medical treatment with the use of an artificial heart effective, we developed the Tsukuba remote monitoring system, which enables medical staff to manage the physiological condition of patients and the driving condition of the artificial heart at anytime from a remote place. This remote monitoring system has three functions: first, a remote monitoring function, which enables medical staff to monitor measured data from a remote place anytime by using not only a personal computer but also a cellular phone; second, an analyzing function, which estimates the unmeasured physiological behavior in the body based on a mathematical physiological model; and third, a warning function, which detects physiological problems and malfunction of the artificial heart by applying the if-then rule and sends a warning message to the medical staff. As a result of applying this system to animal experiments, we have confirmed the effectiveness of the proposed system.

Animals↗

PubMed2002

On-line parameter identification of systemic circulation using the delta operator.

To develop effective medical care with the artificial heart, we propose a new method, on-line parameter identification of the systemic circulation using the delta operator which can calculate the time-varying and unmeasured hemodynamics of the internal human body from some measured data: aortic pressure and total flow in real time. This method consists of first, a dynamic physiological model which is configured with the physiological parameters Ca (aortic compliance) and Rp (total peripheral resistance); and second, a system identification method using the delta operator. In the computer simulation study, we could confirm the effectiveness to identify the physiological parameters. In animal experiments with a left ventricular assist system, the physiological parameters, Ca = 1.8 (ml/mm Hg) and Rp = 0.8 (mm Hg s/ml), could be identified on-line.

Adaptation, Physiological↗

PubMed2002

Online parameter identification of second-order systemic circulation model using the delta operator.

To develop effective medical care with the artificial heart, we proposed a new method that can calculate the time varying and unmeasured hemodynamics of the human body from measured physiological data: aortic pressure, aortic flow, and pump flow in real time. This method comprises first, the second order of systemic circulation model, which consists of aortic compliance (Ca), aortic resistance (Ra), aortic inertia (L), and total peripheral resistance (Rp); and second, system identification using the delta operator. In the computer simulation, we confirmed the effectiveness of this method. During the animal experiment with the left ventricular assist system, the physiological parameters could be identified online: mean Ra = 0.04 mm Hg s/ml, mean Ca = 0.65 mm Hg/ml, mean L = 0.004 mm Hg s(2)/ml, and mean Rp = 0.3 mm Hg s/ml. This new method efficiently identified the physiological parameters, which are important not only to support the medical care but also to develop the control method adapted to the physiological behavior.

Animals↗

PubMedDate not supplied

Fractural characteristic evaluation of a microcapsule suspension using a rotational shear stressor.

We are developing microcapsule suspensions to evaluate the absolute hemolytic properties of centrifugal blood pumps. Four types of microcapsule suspensions, with maximum diameters of 100 microm or 10 microm, and membranes of polyurethane or melamine resin, were exposed to fluid dynamic shear up to 15,000 s(-1) with a rotating shear stressor developed in our laboratory. As a result, destruction was observed of only the 100 microm microcapsules. The microcapsules with polyurethane membranes broke at a high shear velocity range over 11,250 s(-1), a tendency similar to that observed using bovine blood. The microcapsules with melamine resin ruptured at approximately 7,500 s(-1). These observations could lead to determination of absolute hemolysis from shear stress occurring in centrifugal blood pumps.

Biomechanical Phenomena↗

PubMedDate not supplied

Development of built-in type and noninvasive sensor systems for smart artificial heart.

It is very important to grasp the artificial heart condition and the physiologic conditions for the implantable artificial heart. In our laboratory, a smart artificial heart (SAH) has been proposed and developed. An SAH is an artificial heart with a noninvasive sensor; it is a sensorized and intelligent artificial heart for safe and effective treatment. In this study, the following sensor systems for SAH are described: noninvasive blood temperature sensor system, noninvasive blood pressure sensor system, and noninvasive small blood flow sensor system. These noninvasive sensor systems are integrated and included around the artificial heart to evaluate these sensor systems for SAH by the mockup experiments and the animal experiments. The blood temperature could be measured stably by the temperature sensor system. Aortic pressure was estimated, and sucking condition was detected by the pressure sensor system. The blood flow was measured by the flow meter system within 10% error. As a result of these experiments, we confirmed the effectiveness of the sensor systems for SAH.

Animals↗