Understanding erythrocyte behavior, especially changes in hematocrit in narrow gaps of mechanical circulatory support devices, is important to decrease the pump-derived hemolysis. The present study aimed to propose and evaluate a method of calculating hematocrit in narrow gaps using a high-speed microscope and a laser confocal displacement meter. We calculated hematocrit based on scatter theory and erythrocyte occupancy, mean corpuscular volume, clearance gap, and modeled cross-sectional areas of erythrocytes. The method was initially validated using bovine blood with hematocrit ≤ 1.0% and a comparison of the cross-sectional area modeling. Hematocrit in a spiral groove bearing of a blood pump was then evaluated using bovine blood with hematocrit of 1.0%. As the result, hematocrit calculated using this method was essentially equal to that of the test blood when the circulatory cross-sectional area modeling of biconcave erythrocyte was used. We confirmed that the new method could calculate hematocrit ≤ 1.0% in gaps ≤ 50 μm wide.

Thrombus formation on biomaterial surfaces with microstructures is complicated and not fully understood. We assumed that the micro-stagnation generated around microstructures is one factor to enhance thrombus formation. In our prediction, the micro-flow around microstructures causes blood components to adhere physically in a low Reynolds number region. The objective of this study is to investigate the micro-flow around three-dimensional micro-geometric structures and the aspects of physical adhesion affected by the micro-flow. Flow simulation and quantitative assessment of adhesion rates around micro-columns was conducted as a basic study. The particle pathlines and average shear rate around a column were calculated through computational fluid dynamics analysis. The simulation showed that low shear rate distribution caused by flow-stagnation is generated around a column, even if it is in micro-flow in a low Reynolds number region. Physical adhesion tests using micro-beads showed that the average adhesion rate around the column was higher than that in the neighboring plane area. A low shear rate region generated by microstructures may increase the potential for adhesion of substances, which enhances thrombus formation even when the scale of flow is of the order of micrometers.

We have developed a small, thin, maglev ventricular assist device that can be implanted under the thorax muscle layer like a pacemaker. A cascade pump with inlet and outlet ports in the same plane and a radial type self-bearing motor are used to reduce the axial thickness of the device. The radial position of a levitated impeller and its rotation are actively controlled by the radial type self-bearing motor. Axial position and tilt motion are stabilized passively with self-restoring permanent magnets. Motion of the levitated impeller is measured by using two eddy current sensors, and three laser displacement sensors are used to evaluate the motion. Transient computational fluid dynamics analysis was conducted to estimate the hydrodynamic force on the levitated impeller. The motion of the levitated impeller is small in comparison with the range of motion. Estimated hydrodynamic force is also small. It was confirmed that device levitation did not fail due to hydrodynamic force. The axial position and tilt motion of the levitated impeller are adequately supported in passive stability.

The purpose of this study establishes an evaluation of correlation between the gait and the structure of the knee- brace (CB-brace) for K-OA. The optical 3D motion capture analysis system was used for gait analysis. In advance, we confirmed the fit of the knee brace and the ratio of the medial compartment by two measurement methods.One confirmed the ratio of the medial compartment of the knee by measuring the gap between the center of the knee joint and Mikulicz line while another carried out gait analysis without wearing and while wearing knee-brace. The extent of the knee pain of the each subject can be objectively evaluated by referring to the visual analogue scale (VAS) for each trial. We measured the structure characteristic of the knee-brace attached 8makers on arm support during gait. The results showed ① The angle change amount of each arm. ② The distance between the top of each arm and the joint. ③ The posture change of the knee brace by the degree of the rotation angle of the X, Y, Z axis by the orthosis coordinate system. In conclusion, we evaluated the correlation of the knee-orthosis structure during gait.