Biomedical subjects

T Yambe

Publications and source records attributed to T Yambe.

93 records · Page 6Linked to original sources

PubMedDate not supplied

The newly designed univalved artificial heart.

A univalved artificial heart (AH) powered electromagnetically in the frequency range of 1-30 Hz was developed to obtain a totally implantable AH. This small sized AH consisted of a vibrating tube, coils, magnets, and a jellyfish valve as an outlet AH valve. The fluid mechanical, hemodynamic, and hematologic properties were evaluated in a mock circulation and 10 animal experiments using adult goats. This vibrating electromagnetic AH could generate more than 10 L/min as an output volume, with 10 Hz vibration using 20 volts supplied voltage. It could also provide two kinds of flow and pressure patterns, in constant-peak and periodic-peak patterns. The values of free hemoglobin remained within acceptable limits. The authors concluded that this new type of pump was useful as a totally implantable AH, ventricular assist, or organ assist system.

Blood Flow Velocity↗

PubMedDate not supplied

Deterministic chaos in the hemodynamics of an artificial heart.

To analyze the hemodynamic parameters during prosthetic circulation as an entity, non linear mathematical techniques were used. To compare natural and prosthetic circulation, two pneumatically actuated ventricular assist devices were implanted as biventricular bypasses in chronic animal experiments using adult goats to consitute the biventricular bypass complete prosthetic circulation model with ventricular fibrillation. After implantation, these goats were placed in a cage and extubated after waking. All hemodynamic parameters with the natural circulation without biventricular bypass pumping, and the artificial circulation with biventricular bypass pumping under ventricular fibrillation were recorded under awake conditions. By the use of a non linear mathematical technique, the arterial blood pressure waveform was embedded into a four dimensional phase space and projected into three dimensional phase space. The Lyapunov numeric method is used as an adjunct to the graphic analysis of the state space. A phase portrait of the attractor showed a high dimension complex structure, with three dimensional solid torus suggesting deterministic chaos during natural circulation. However, a simple attractor, such as a limit cycle attractor, was observed during artificial circulation. Positive Lyapunov exponents during artificial circulation suggest the lower dimensional chaotic system. Thus, hemodynamic parameters during prosthetic circulation must be carefully controlled when unexpected stimuli are fed from outside.

Animals↗

PubMedDate not supplied

[Chaotic attractor of the left ventricular wall motion in normal heart healthy subject].

To analyze the entire left ventricular wall motion, not the decomposed motion, nonlinear mathematical techniques were used to describe graphically time series data for the left ventricular contraction. Time series data of the left ventricular wall motion were recorded by M-mode echocardiography, and embedded into three-dimensional phase space. The largest Lyapunov exponents, a measure of the rate of divergence in phase space, were calculated to detect the sensitive dependence on initial conditions. The reconstructed attractor of the left ventricular contraction showed a lower dimensional strange attractor, and calculation of the Lyapunov exponents indicated sensitivity to initial conditions. These results suggest that time series data of the left ventricular contraction show the characteristics of deterministic chaos. The chaotic system can provide an intelligent and flexible control system. Our results suggest that the circulatory control system, which mediates the cardiac contractility, may be a flexible dynamic compatible with deterministic chaos.

Echocardiography↗