Blood Pump Membrane Speed Control for Hemolysis Reduction
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Solution Overview
Problem
Existing extracorporeal blood pumps cause hemolysis, leading to reduced hematocrit levels and increased need for erythropoietin administration, particularly problematic for patients with low hematocrit levels due to medical conditions like end-stage renal failure, where blood cell integrity is crucial for effective oxygen transport and separation during treatments like dialysis and apheresis.
Innovation Solution
A blood pump design featuring a cartridge with a concave recess and a flexible membrane forming a pump chamber, where the membrane moves between maximum and minimum volumes under controlled speed by a driver mechanism, reducing shear forces and fluid pressure spikes to minimize blood cell damage, utilizing a controller and proportional valve system to manage fluid flow and valve operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If peristaltic type pumps are used to pump blood in extracorporeal circulation, then the pumps are reliable and accepted within the medical industry, but they cause hemolysis resulting in lowered hematocrit level
Solution Approach 1:
The patent replaces the peristaltic mechanical pumping system with a membrane-based volumetric pumping system. The membrane pump chamber expands and contracts to move blood, eliminating the peristaltic squeezing action that causes hemolysis while maintaining reliable blood circulation in extracorporeal circuits
Solution Approach 2:
The patent changes the fundamental pumping mechanism from peristaltic compression to controlled membrane displacement. By adjusting membrane position between first and second positions, the system achieves reliable blood pumping with reduced shear forces and minimal hemolysis
2Productivity
If the membrane moves quickly between positions to pump blood effectively, then blood flow is maintained, but shear forces on blood cells increase causing damage
Solution Approach 1:
The patent implements dynamic control of membrane movement speed during the pumping cycle. The membrane moves at variable speeds - faster during bulk transport and slower during critical phases - to optimize both blood flow rate and cell protection, preventing damage from excessive shear forces
Solution Approach 2:
The membrane undergoes periodic expansion and contraction cycles between first and second positions. This periodic motion creates controlled blood flow while allowing the membrane to move at optimized speeds during each cycle, balancing productivity with blood cell protection
3Productivity
If the membrane stops abruptly at maximum or minimum volume positions, then pumping action is complete, but fluid pressure spikes occur reducing effectiveness
Solution Approach 1:
The controller initiates membrane movement in advance of the previous stroke completion. By starting the return movement before the membrane fully stops at maximum or minimum volume, the system prevents abrupt pressure spikes and maintains smooth, continuous blood flow while preserving pumping efficiency
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 solution effectively reduces blood cell damage by minimizing shear forces and fluid pressure spikes, thereby minimizing hemolysis and maintaining blood cell integrity during extracorporeal treatments, reducing the need for erythropoietin and ensuring effective oxygen transport.
Implementation Method 1
a flexible membrane covering said recess, the concave recess and flexible membrane forming a pump chamber... said driver operable to move the flexible membrane in a first direction into the recess to, in use, pump blood from the chamber
Implementation Method 2
the speed at which it is moving reduces as it approaches the surface of the concave recess. By reducing the speed of the membrane as it approaches the surface of the concave recess shear forces acting on the blood cells as they accelerate through the reducing gap between the membrane and the surface of the concave recess are reduced
Implementation Method 3
the pump driver mechanism comprises drive fluid for applying fluid pressure to the membrane to move it between the first and second positions
Data Source
Figure 1
Figure 2
AI summary
Ablood pump 2 comprising: a cartridge 4 having a concave recess 8 therein having a surface, and a flexible membrane 0 covering said recess, the concave recess and flexible membrane forming a pump chamber 12 having an inlet 14 and an outlet 16 wherein: said flexible membrane is movable between a first position, separated from said surface wherein in such position the pump chamber has a maximum volume, and a second position, substantially adjacent said surface such that in said second position the pump chamber has a minimum volume, a pump driver mechanism 18 arranged to interface with the cartridge, said driver operable to move the flexible membrane in a first direction into the recess to, in use, pump blood from the chamber and operable to move the flexible membrane in a second direction away from the recess to, in use, draw blood into said chamber;and wherein the pump driver controls the movement of the flexible membrane in the first direction such that the speed at which it is moving reduces as it approaches the surface of the concave recess.