Partial Arc Journal Bearings for Blood Pump Hemolysis Reduction
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Solution Overview
Problem
Current ventricular assist devices (VADs) face challenges such as large size leading to tissue displacement, bacterial colonization, extensive adhesions, high shear stresses causing hemolysis, and thrombosis formation, which can result in reduced patient viability and increased morbidity.
Innovation Solution
A rotary dynamic blood pump with a unique partial arc journal bearing configuration, where the bearings are located in the main blood flow stream and supported by magnetic loading, minimizing blood exposure to shear stresses and reducing thrombosis risk through continuous blood washing and wear-free fluid film support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional journal bearings with full circumference bushings are used, then structural support is improved, but blood exposure to shear stresses increases causing hemolysis and thrombosis
Solution Approach 1:
The bushing is segmented into a partial arc configuration rather than a full circumference, creating discrete bearing surfaces that reduce the area exposed to blood flow while maintaining necessary structural support. This segmentation allows blood to flow through the bearing region with minimal contact time and reduced shear stress exposure.
Solution Approach 2:
The patent applies partial arc journal bearings that provide only the minimum necessary bearing surface area required for structural support, rather than full circumference bushings. This partial action reduces blood-bearing surface contact while maintaining adequate mechanical support for the rotor.
2Productivity
If larger VAD devices are used to provide adequate output, then pumping capacity is improved, but tissue displacement and bacterial colonization risk increase
Solution Approach 1:
The patent changes the bearing configuration parameter from full circumference to partial arc, which reduces the overall device size and blood contact area while maintaining pumping capacity. This parameter change allows for a more compact device design that minimizes tissue displacement and infection risk.
3Stability of the object's composition
If more extensive blood contact surfaces are used in bearings, then structural stability is improved, but thrombosis formation increases
Solution Approach 1:
The bearing surface is segmented into a partial arc configuration that provides structural stability through concentrated bearing surfaces while minimizing the total area in contact with blood. This reduces thrombosis formation risk by limiting the surface area where blood can stagnate or form clots.
Solution Approach 2:
The partial arc bearing design allows blood to flow through the bearing region more quickly with reduced contact time, skipping over potential thrombosis formation zones. The open arc configuration creates flow paths that prevent blood stagnation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design provides reduced red cell destruction, improved heat removal, and lower thrombosis risk, resulting in a smaller, more durable, and less invasive circulatory support device with minimal surgical invasiveness and reduced risk of infection, suitable for a wide range of patient sizes and applications.
Implementation Method 1
magnetic rings that exert a net radial force on the rotating assembly that maintains the rotating assembly seated in the partial arc journal bearings
Implementation Method 2
small hydrodynamic bearings located at the front (i.e., upstream) and the rear (i.e., downstream) ends of the pump. The bearings are configured as journal bearings
Implementation Method 3
the bearings are located in a significant blood flow stream of the device, and the unloaded side of the bearing left open to the blood flow
Data Source
Figure 1~2
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Figure 6~7
AI summary
A blood pump (10) includes a pump housing (30) having a pump inlet (16) and a pump outlet (18) spaced apart along a longitudinally extending central pump axis (28). The blood pump (10) also includes a rotating assembly (100) comprising an impeller (104). The blood pump (10) further includes partial arc journal bearings (160, 180) that support the rotating assembly (100) for rotation in the housing (30). The rotating assembly (100) is rotatable relative to the housing (30) to pump blood from the pump inlet (16) to the pump outlet (18).