Dialysis Machine Flow Balance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Haemodialysis machines face inaccuracies in flow balance due to manufacturing tolerances in pumps and valves, leading to unacceptable mass transfer errors, which are exacerbated by varying blood line pressures and compliant structures in the fluid pathway.
Innovation Solution
A dialysis device with a controller that monitors blood line pressures and adjusts the dialysate distribution pump's pressure proportionally to maintain flow balance, using a flow balance pump with chambers and valves to manage fluid flow and reduce errors by controlling hydraulic resistance and valve closure pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If manufacturing tolerances in pumps are reduced to improve flow balance accuracy, then manufacturing precision improves, but device complexity and cost increase
Solution Approach 1:
The patent implements a feedback control system where a flow sensor continuously measures the actual flow rate from the pump, and a controller adjusts the pump operation to compensate for deviations from the target flow rate. This closed-loop feedback mechanism eliminates the need for ultra-precise manufacturing tolerances while maintaining accurate flow balance.
Solution Approach 2:
The system dynamically changes operational parameters (pump speed, valve timing) based on real-time flow measurements. By adjusting these parameters during operation rather than relying on fixed manufacturing precision, the system achieves accurate flow control without requiring excessively tight manufacturing tolerances.
2Measurement precision
If valve switching is implemented to balance pump tolerance errors, then flow balance accuracy improves, but device complexity increases due to additional valves
Solution Approach 1:
The patent makes the existing pump valves perform multiple functions: they control both the direction of fluid flow and the timing of flow distribution. By programming the controller to operate these valves in different sequences and durations, the system achieves flow balancing without requiring dedicated balancing valves, thus avoiding additional hardware complexity.
Solution Approach 2:
The patent replaces mechanical flow balancing mechanisms (such as fixed orifice plates or mechanical valve linkages) with an electronically controlled valve system. The controller uses electronic timing and duration control to achieve flow balance, eliminating the need for complex mechanical coupling between valves while maintaining precision.
3Adaptability or versatility
If compliant structures are used in the fluid pathway to accommodate pressure variations, then adaptability improves, but flow balance accuracy deteriorates due to varying swept volume
Solution Approach 1:
The flow sensor provides real-time feedback on the actual flow rate, allowing the controller to compensate for volume variations caused by compliant structure deformation. The system continuously monitors and adjusts for the elastic expansion and contraction of tubing and chamber walls, maintaining accurate flow balance despite pressure-induced volume changes.
Solution Approach 2:
The compliant structures naturally accommodate pressure variations through their elastic properties, and the system uses this self-adjusting behavior beneficially. The controller learns and compensates for the specific compliance characteristics of each component, turning the passive elastic response into an active compensation mechanism that maintains flow accuracy.
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
This solution significantly reduces flow balance errors by normalizing the variation in compliant structures' swept volume, improving the accuracy and effectiveness of dialysis treatments.
Implementation Method 1
a pressure sensor in the arterial and/or venous blood line, the sensor operably connected to the controller such that the controller receives a signal from the sensor representative of the pressure in the arterial and/or venous blood line
Implementation Method 2
the controller monitors the signal from the sensor in the arterial and/or venous blood line and controls the pressure of the dialysate in the inlet line of the dialysate distribution pump
Implementation Method 3
The action of dialysis across the membrane is achieved primarily by a combination of diffusion (the migration of molecules by random motion from a region of higher concentration to a region of lower concentration), and convection
Implementation Method 4
The action of dialysis across the membrane is achieved primarily by a combination of diffusion and convection (solute movement that results from bulk movement of solvent, usually in response to differences in hydrostatic pressure)
Implementation Method 5
The semi permeable membrane filters the waste products and excess fluid from the blood into the dialysate solution. The membrane allows the waste and a controlled volume of fluid to permeate into the dialysate whilst preventing the loss of larger more desirable molecules
Implementation Method 6
Fluid removal (otherwise known as ultrafiltration) is achieved by reducing the hydrostatic pressure of the dialysate side of the membrane, or increasing the hydrostatic pressure on the blood side, thereby causing free water to move across the membrane along the pressure gradient
Data Source
AI summary
A dialysis machine which monitors the pressure of blood entering and leaving a patient's body using several sensors (37, 39) and adapts the pressure of a dialysate solution feed to compensate for compliances in the dialysate fluid flow path. As a consequence, better flow balance is maintained throughout dialysis treatment leading to a more uniform removal of waste materials from the blood.