Biomedical subjects

T Jikuya

Publications and source records attributed to T Jikuya.

75 records · Page 5Linked to original sources

PubMedDate not supplied

Fluid dynamic characteristics of monopivot magnetic suspension blood pumps.

A monopivot magnetic suspension blood pump is a centrifugal pump under development with a magnetic suspension and a ceramic pivot to support the impeller with minimum contact. The pump size has been reduced by implementing a direct impeller drive mechanism in place of a magnetic coupling and motor. Flow visualization studies revealed that high shear, which seems to be closely related to hemolysis, concentrates in boundary layers near the walls. This implies that fluid dynamic shear can be reduced not by widening the gap, but by reducing the impeller velocity. Therefore, compared with the results of the previous semi-open curved vane impeller model, impeller velocity was reduced by 30% with a closed impeller having radial straight vanes, and smaller impeller/housing gaps. The volute shape around the impeller tip was also changed such that the outflow from the impeller enters along the center plane of the volute. To examine the effect of the improvements, hemolysis testing was conducted and found that the newly developed closed impeller model generated a lower level of hemolysis than the previous semi-open impeller model.

Animals↗

PubMedDate not supplied

Method of noninvasive and continuous hemolysis/thrombogenesis measurement by laser photometry during artificial heart development.

The purpose of this research is to propose and develop a method to measure hemolysis and thrombogenesis non invasively and continuously to aid in development of an artificial heart. Generally, the optical absorption rate of hemoglobin is influenced by oxygen saturation except at the isosbestic point, which is not influenced by oxygen saturation. The authors, therefore, used an 805 nm laser diode, an optical spectrum analyzer to obtain greater accuracy. An experimental blood circuit system was constructed using a Bio-Pump, Tygon tubing, a soft shell reservoir, and an optical measurement system. Experimental settings for monitoring hemolysis were as follows; blood volume 200 ml, blood flow 6 L/min, and afterload 200 mmHg. Blood was sampled six times (0, 30, 60, 120, 180, and 240 min), and hemolysis in each sampled was measured using a colorimetric method. Comparing continuous laser measurement data with the sample data, an adequate correlation is obtained, proving that the dynamic trend of hemolysis could be continuously measured. Furthermore, to analyze the process of thrombogenesis, simple experiments were performed using blood neutralized by protamine. As a result, the authors could see the process of thrombogenesis as it occurred and could confirm that this method is able to dynamically detect hemolysis and thrombogenesis.

Biomedical Engineering↗

PubMedDate not supplied

Species differences in erythrocyte mechanical fragility: comparison of human, bovine, and ovine cells.

The erythrocyte destruction rate under constant shear stress was measured to clarify species differences in red blood cell (RBC) mechanical fragility between human, bovine, and ovine cells. Blood was collected from healthy donors by venipuncture. RBC age fractionation was performed by high speed centrifugation (20 min at 12,000 g). Relatively young, middle, and old age RBCs was suspended in Dulbecco's phosphate buffered saline to adjust the hematocrit to 35%. Uniform shear stress was applied to each sample contained in a concavo-convex Couette flow testing machine. Young and old aged samples were exposed to 300 dyne-sec-cm2 for 0 and 15 min. Middle aged samples were exposed to 300 dyne-sec-cm2 for 0, 5, 10 and 15 min. Liberated hemoglobin was estimated by tetramethylbenzidine colorimetric measurement and the erythrocyte destruction rate was calculated. Older samples had a higher hemolysis rate than younger samples in every species. The destruction under constant shear stress is approximately linear in time. Mechanical fragility of ovine and bovine RBCs was 1.8 and 0.5 times as large as human RBCs, respectively. These values could serve as universal standards when extrapolating animal hemolysis data for any blood pump to predict its safety and biocompatibility in human clinical trials.

Animals↗