Non-occluding Pump Shutdown Sequence for Extracorporeal Blood Treatment
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Solution Overview
Problem
Non-occluding pumps in extracorporeal blood treatment apparatuses pose a risk of uncontrolled fluid flow, particularly blood flow in reverse direction, when shut off or reduced in speed, due to the absence of occlusion bodies.
Innovation Solution
Implementing a time-delayed shut-off or reduction in pump speed, accompanied by controlled shut-off elements and pressure management using ventilation valves or ultrafiltration devices, to prevent reverse flow by creating excess pressure in the fluid system before opening shut-off elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-occluding pump is shut off or reduced in speed, then productivity is improved (treatment can be paused or adjusted), but reliability deteriorates (risk of uncontrolled reverse flow)
Solution Approach 1:
The patent applies preliminary action by closing shut-off elements before shutting off or reducing pump speed. This sequence ensures that the fluid pathway is sealed in advance, preventing any potential reverse flow that could occur when the pump stops or slows down. The control unit coordinates this preliminary closure action to maintain reliability while allowing productivity adjustments.
2Ease of operation
If non-occluding pump is used, then ease of operation is improved (no occlusion bodies to manage), but reliability deteriorates (no inherent reverse flow prevention)
Solution Approach 1:
The patent introduces shut-off elements as intermediary components that provide reverse flow prevention without requiring modification to the pump structure itself. These elements act as mediators between the simple non-occluding pump and the reliability requirement, enabling the pump to maintain its operational simplicity while ensuring controlled fluid directionality through the coordinated action of shut-off elements and timing control.
3Loss of time
If pump is shut off immediately, then time is saved (no delay), but harmful factors increase (excess pressure buildup causing uncontrolled flow)
Solution Approach 1:
The patent applies preliminary action by closing shut-off elements before pump shutdown, which allows the system to manage pressure buildup proactively. This preliminary closure enables controlled pressure equalization through alternative pathways (such as ventilation valves or ultrafiltration) before the pump stops, preventing harmful excess pressure from developing while accepting a minimal, controlled time delay.
Solution Approach 2:
The patent converts the potentially harmful excess pressure into a beneficial control mechanism by using it to drive fluid through alternative pathways (ventilation, ultrafiltration) that safely relieve pressure. The controlled pressure buildup becomes a driving force for pressure equalization rather than a harmful effect, eliminating uncontrolled reverse flow while maintaining system safety.
Data Source
AI summary
An extracorporeal blood treatment apparatus having a fluid system and a pump for conveying fluid in the fluid system, wherein the pump is a non-occluding pump, and a method for shutting off or reducing the speed of rotation of a non-occluding pump in a fluid system of an extracorporeal blood treatment apparatus. The apparatus and the method are characterized in that before the speed of rotation is reduced or the pump is shut off, the fluid flow into the feed line and out of the discharge line is first interrupted, and after a predetermined time interval after interruption of the fluid flow has elapsed, the speed of rotation of the pump is reduced or the pump is shut off. The time-delayed shut-off of the pump prevents a reverse flow of fluid, particularly of blood into the arterial blood line, even in the absence of occlusion. As a result of the time-delayed shut-off or reduction in the speed of rotation of the pump, however, an excess pressure is produced in the fluid system. Therefore the blood treatment apparatus and the method provide for counter-measures to prevent uncontrolled fluid flow when the shut-off elements are opened, due to the excess pressure.