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Biomedical subjects

M Oshikawa

Publications and source records attributed to M Oshikawa.

12 recordsLinked to original sources
PubMed2001

Application of indirect flow rate measurement using motor driving signals to a centrifugal blood pump with an integrated motor.

The method of measuring the flow rate of a centrifugal blood pump from the input electric power, which will be indispensable for the long-term use of such devices, was developed and was applied to the direct-driven centrifugal blood pump that has been developed by our research group. The accuracy was evaluated in a chronic animal experiment using an adult goat. The results demonstrated that this method carries the sufficient potential of the instantaneous monitoring method, but errors due to electromagnetic and mechanical losses were not determined always precisely. The detection of adverse phenomena such as the obstruction of the inlet cannula was also possible from the estimated value of the flow rate and its waveform pattern.

Animals↗
PubMed2000

Bose-Einstein condensation of dilute magnons in TlCuCl3.

The recent observation [A. Oosawa et al., J. Phys. Condens. Matter 11, 265 (1999)] of the field-induced Neel ordering in the spin-gap magnetic compound TlCuCl3 is interpreted as a Bose-Einstein condensation of magnons. A Hartree-Fock-type calculation based on this picture is shown to describe the temperature dependence of the magnetization well.

Journal Article↗
PubMed2000

Commensurability, excitation gap, and topology in quantum many-particle systems on a periodic lattice

In combination with Laughlin's treatment of the quantized Hall conductivity, the Lieb-Schultz-Mattis argument is extended to quantum many-particle systems (including quantum spin systems) with a conserved particle number on a periodic lattice in arbitrary dimensions. Regardless of dimensionality, interaction strength, and particle statistics (Bose or Fermi), a finite excitation gap is possible only when the particle number per unit cell of the ground state is an integer.

Journal Article↗
PubMed2000

Sensorless controlling method for a continuous flow left ventricular assist device.

We originated a novel control strategy for a continuous flow left ventricular assist device (LVAD). We examined our method by acute animal experiments to change the left ventricular (LV) contractility or LV end-diastolic pressure (LVEDP). To estimate the pump pulsatility without any specific sensor, we calculated the index of current amplitude (ICA) from motor current waveform. The ICA had a peak point (t-i point) that corresponded closely with the turning point from partial to total assistance, and a trough (s-i point) that corresponded with the beginning point of ventricular collapse. The pump flow at the t-i point (Qt-i) had no component of flow regurgitation. In the evaluation of the effects of preload LVEDP, afterload (mAoP), and contractility (max LV dp/dt), we found that preload was the only parameter that significantly influenced Qt-i. We concluded that our method could well control continuous flow LVAD by preventing reversed flow and ventricular collapse.

Animals↗
PubMed2000

Control strategy for biventricular assistance with mixed-flow pumps.

A left ventricular assist device (LVAD) is an effective method to rescue severe heart failure. Although some require a biventricular assist, the control method for the biventricular assist device (BVAD) with a rotary pump is rarely shown. The objective of this study was to investigate the strategy for controlling BVAD with rotary pumps by in vivo studies. Using 5 piglets, we set a BVAD through a left thoracotomy and made global ischemia for 30 min by clamping the base of the ascending aorta. After unclamping, the analysis of pumping performance acted for 6 h reperfusion. We set the target flow of the LVAD and set the right ventricular assist device (RVAD) speed limit as less than when the atrial collapse occurs. To detect the ventricular collapse without any specific sensor, we calculated the index of current amplitude from motor current waveform and simultaneous mean current value. In all cases, over 6 h of observation was performed, and the RVAD was weaned almost automatically.

Analysis of Variance↗
PubMed1998

In vitro performance of a centrifugal, a mixed flow, and an axial flow blood pump.

We specially devised 3 types of turbo pumps, a centrifugal pump (CFP), a mixed flow pump (MFP), and an axial flow pump (AFP), and analyzed their in vitro performance. The common structural design elements were an impeller diameter of 20 mm and sealless magnet couple driving. In vitro tests were carried out using heparinized fresh bovine blood. The hemolysis was comprehensively evaluated at 7-16 points by changing the flow rate and pressure head (mapping of hemolytic property). The maximum efficiency (motor output to pump output) was 44.9% at 7,000 rpm, 3.17 L/min, 191 mm Hg in the CFP; 66.3% at 7,000 rpm, 6.9 L/min, 136 mm Hg in the MFP; and 20.6% at 9,000 rpm, 5.54 L/min, 74 mm Hg in the AFP, respectively. The minimum normalized index of hemolysis (NIH) (g/100 L) was 0.038 at 5,000 rpm, 4.60 L/min, 38 mm Hg in the CFP; 0.010 at 7,000 rpm, 8.22 L/min, 100 mm Hg in the MFP; and 0.033 at 7,000 rpm, 2.84 L/min, 48 mm Hg in the AFP, respectively. The best efficiency and NIH were achieved in the MFP.

Animals↗
PubMed1990

[Case report of the superior approach for correction of the supracardiac type of total anomalous pulmonary venous drainage (TAPVD) in the neonatal period].

An eleven-day-old newborn with cyanosis and respiratory distress was admitted. Intubation and catecholamine administration had already done. Blood pressure was 80/50 mmHg, heart rate was 160/min. Urine volume was only 7 ml per 4 hours with diuretics. The diagnosis of supracardiac type of TAPVD was done by echo cardiography. Without cardiac catheterization, emergent operation was performed. After median sternotomy, the mobilization of the aorta was done. Under cardiopulmonary bypass the aorta was retracted to the left, the superior vena cava to the right and the common pulmonary venous trunk (CPV) was identified through the transverse sinus. Parallel incision were made in the left atrium and CPV, and extended to the vertical vein. An anastomosis using continuous suture was fashioned. She had a good postoperative course. The superior approach through the transverse sinus affords excellent exposure of the CPV and left atrium in situ in the neonatal period, if the mobilization of the aorta is completed, and the heart is not compressed or displaced. This approach is useful for supracardiac type of TAPVD.

Female↗
PubMedDate not supplied

Detection of total assist and sucking points based on the pulsatility of a continuous flow artificial heart: in vivo evaluation.

Our novel control strategy for a continuous flow artificial heart by detecting the total assist and sucking points based on pump pulsatility was evaluated in acute animal experiments using beagle dogs and our mixed flow pump. The pump was installed as a left ventricular (LV) bypass through a left thoracotomy. To change LV contractility, the left coronary arteries were occluded for 30 min, followed by a 120 min reperfusion. To change LV end diastolic pressure (LVEDP), dextran solution was rapidly infused. To estimate the pump pulsatility without any specific sensor, we calculated the index of current amplitude (ICA), which was obtained from the amplitude of the motor current waveform divided by the simultaneous mean value. To investigate the basic characteristics of the ICA, the pump speed was changed temporarily from 2,300 rpm to 5,000 rpm. In 92% of all measurements, the ICA plotted against the pump speed had a peak point (t-point) that corresponded highly with the turning point from partial to total assistance. The ICA also had a trough (s-point) that corresponded with the beginning of severe sucking in most cases. Only preload significantly influenced pump flow rate at the t-point from among preload (LVEDP), afterload (SAoP), and contractility (max LV dP/dt), by which we can simulate Starling's law of the natural heart. We concluded that a continuous flow artificial heart could be well controlled by detecting the t-point and s-point.

Animals↗
PubMedDate not supplied

Detection of total assist and sucking points based on pulsatility of a continuous flow artificial heart: in vitro evaluation.

We investigated the basic characteristics of the pulsatility of motor current with an in vitro mock circuit that consists of a sac-type pulsatile pump (simulating the natural left ventricle), three reservoirs, and our mixed flow pump (MFP). There are three alternatives at the inlet of the MFP: 1) the left atrium (LA), 2) the left ventricle (LV), and 3) both (LALV). The motor current waveform was monitored. The pump speed of the MFP was changed from 0 to 7,000 rpm. We calculated the index of motor current amplitude (ICA), which was obtained from the amplitude of the motor current waveform divided by the simultaneous mean value. The ICA plotted against the pump speed had a peak point (t-point) that highly corresponded with the turning point from partial to total left heart assistance. The ICA also had a second specific point (s-point) that corresponded with the beginning of severe sucking. In LV and LALV aortic bypass, t- and s-points could clearly be detected. In LA aortic bypass, however, early and severe sucking occurred, and t- and s-points were not manifest. These data suggest that the assist status of continuous flow artificial heart can be estimated by detecting the t- and s-points.

Blood Flow Velocity↗