Leslie L.J.,Aston University |
Marshall L.J.,Aston University |
Devitt A.,Aston University |
Hilton A.,Calon Cardio Technology Ltd |
Tansley G.D.,Griffith University
Artificial Organs | Year: 2013
Cell exclusion is the phenomenon whereby the hematocrit and viscosity of blood decrease in areas of high stress. While this is well known in naturally occurring Poiseuille flow in the human body, it has never previously been shown in Couette flow, which occurs in implantable devices including blood pumps. The high-shear stresses that occur in the gap between the boundaries in Couette flow are known to cause hemolysis in erythrocytes. We propose to mitigate this damage by initiating cell exclusion through the use of a spiral-groove bearing (SGB) that will provide escape routes by which the cells may separate themselves from the plasma and the high stresses in the gap. The force between two bearings (one being the SGB) in Couette flow was measured. Stained erythrocytes, along with silver spheres of similar diameter to erythrocytes, were visualized across a transparent SGB at various gap heights. A reduction in the force across the bearing for human blood, compared with fluids of comparable viscosity, was found. This indicates a reduction in the viscosity of the fluid across the bearing due to a lowered hematocrit because of cell exclusion. The corresponding images clearly show both cells and spheres being excluded from the gap by entering the grooves. This is the first time the phenomenon of cell exclusion has been shown in Couette flow. It not only furthers our understanding of how blood responds to different flows but could also lead to improvements in the future design of medical devices. © 2013, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.
Calon Cardio Technology Ltd | Date: 2013-10-17
Calon Cardio Technology Ltd. | Date: 2014-05-21
A plain bearing assembly for a cardiac pump, the plain bearing assembly comprising; a rotational portion which, in use, rotates with a cardiac pump rotor, the rotational portion configured to engage a stationary portion of a cardiac pump housing, the stationary portion comprising one or more first bearing surfaces and the rotational portion comprising one or more second bearing surfaces, the one or more second bearing surfaces configured so as to be in contact with the one or more first bearing surfaces, therein defining a bearing interface between the one or more first bearing surfaces and the one or more second bearing surfaces during rotation of the rotational portion, wherein the rotational portion comprises one or more first flow channels configured to interrupt the bearing interface and permit blood to flow between an outside of the plain bearing assembly and a center of the plain bearing assembly.
Calon Cardio Technology Ltd | Date: 2010-04-19
The pump is of an axial flow rotary pump, suitable for implantation into the human heart or vascular system, and comprises an elongate tubular casing (
Calon Cardio Technology Ltd | Date: 2012-07-18
The cardiac pump, which is suitable for implantation into a ventricle of a human heart, has a primary blood flow path through a housing, a rotatable pump member disposed within the housing for causing blood to flow along the primary flow path, the pump member being rotatably coupled to the housing about an upstream bearing and a downstream bearing. The pump member includes an impeller shroud defining a secondary flow path in fluid communication with the primary flow path. The downstream bearing comprises a rotational bearing member and a stationary bearing seat for the bearing member, there being a circumferential transition between the bearing seat and the bearing member, the circumferential transition being disposed in the secondary flow path and arranged to be washed by blood passing along the secondary flow path.