Sterilizing Filter Pump Control Using Pressure Zones
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Solution Overview
Problem
Existing methods for maintaining sterility in blood processing systems face challenges in controlling the volume of fluid introduced due to inefficient pumping caused by variations in pump stroke volume, particularly when using negative pressure to pull fluid through a sterilizing filter.
Innovation Solution
A method and system for controlling fluid flow by managing pressure in the fluid flow circuit downstream of the sterilizing filter, using a programmable controller to adjust pump flow rates based on measured pressure zones, ensuring accurate volume control of saline introduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If negative pressure is used to pull fluid through the sterilizing filter, then sterility is maintained, but pump efficiency deteriorates due to variations in pump stroke volume
Solution Approach 1:
The system continuously monitors pressure downstream of the sterilizing filter and uses this feedback to dynamically adjust pump operation. When pressure indicates efficient pumping (within target range), the pump continues normal operation. When pressure deviates from the target range, the system adjusts pump speed or stroke volume to restore efficient operation, thereby maintaining both sterility and pump efficiency.
Solution Approach 2:
The pump operation is made dynamic rather than static. The pump speed or stroke volume is continuously adjusted based on real-time pressure conditions downstream of the filter. This dynamic adjustment allows the system to adapt to varying flow conditions and maintain optimal pumping efficiency while preserving the sterile barrier function of the filter.
2Reliability
If negative pressure is used to pull fluid through the sterilizing filter, then sterility is maintained, but fluid volume control deteriorates
Solution Approach 1:
Pressure downstream of the sterilizing filter serves as a feedback signal for controlling fluid volume. The system monitors this pressure continuously and uses it to adjust pump operation to maintain pressure within a target range that corresponds to accurate fluid volume delivery. This feedback mechanism ensures both sterility and precise volume control.
Solution Approach 2:
The system changes pump operating parameters (speed, stroke volume) based on pressure conditions to achieve precise fluid volume control. By adjusting these parameters in response to pressure feedback, the system maintains accurate control over the volume of fluid introduced into the blood processing circuit while preserving sterility through the filter.
3Reliability
If operator interaction is required to bypass automated controls for saline attachment, then sterility can be maintained, but system complexity increases
Solution Approach 1:
The system performs automatic pressure monitoring and pump adjustment without requiring operator intervention. The automated control system independently manages fluid flow through the sterilizing filter by monitoring pressure and adjusting pump operation, thereby maintaining sterility while reducing system complexity and eliminating the need for manual bypass procedures.
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 system effectively manages fluid flow to maintain sterility and accuracy in blood processing procedures, preventing inefficient pumping and ensuring consistent fluid volume delivery.
Implementation Method 1
a pump draws fluid through the tubing segment using negative pressure P
Data Source
AI summary
A method is provided for controlling fluid flow through a tubing segment is provided in which a pump draws fluid through the tubing segment using negative pressure P. The method includes the steps of: a) operating the pump at an initial commanded fluid flow rate to draw fluid through the tubing segment; b) measuring on a continuous basis the P in the tubing segment; c) determining into which of four zones the measured P falls, a first zone being where P>X1, a second zone being where X1>P>X2, a third zone where X2>P>X3, and a fourth zone where X3>P; d) if P is in the first zone for greater than a first pre-established time period, then increasing the commanded flow rate of the pump and returning to step b); e) if P is in the second zone, then continuing to operate the pump at the flow rate at which the pump is currently operated and returning to step b); f) if P is in the third zone, for greater than a second pre-established time period, then decreasing the commanded flow rate of the pump and returning to step b); and g) if P is in the fourth zone, then commanding the pump to stop. A system including a programmable controller configured to automatically perform the method is also disclosed.