Pump Stroke Volume Calibration Using Optical Volume Measurement
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Solution Overview
Problem
Existing fluid processing systems face inaccuracies in stroke volume calibration due to instability in weight scales, environmental factors, and pump performance changes during procedures, leading to deviations in product volumes and reduced accuracy.
Innovation Solution
A fluid processing device with a volume measurement system and a controller that continuously monitors and adjusts pump operation by calculating standard deviations of volume changes, determining correct system operation, and applying correction factors to maintain accurate stroke volumes and fluid processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If weight scale snapshots are taken to calculate correction factors, then volume accuracy can be improved, but procedure disruption and time increase occur when stability issues arise
Solution Approach 1:
The patent replaces the mechanical weight scale system with an optical volume measurement system. The optical system continuously measures fluid volume in containers without physical contact, eliminating the need for mechanical weight measurements that are susceptible to instability from high flow rates, environmental factors, and procedural disruptions. This substitution maintains measurement precision while eliminating the need to pause procedures for stability checks.
Solution Approach 2:
The patent implements continuous volume measurement throughout the entire apheresis procedure using optical sensors, rather than taking intermittent snapshots with weight scales. The system continuously monitors fluid volume in all containers (blood, platelet-rich plasma, platelet-poor plasma, and waste) and calculates correction factors in real-time, ensuring that volume accuracy is maintained without procedure disruption at any stage of the process.
2Measurement precision
If calibration is performed during priming stage, then initial accuracy can be established, but inaccuracies during fluid processing cannot be accounted for
Solution Approach 1:
The patent performs preliminary volume measurement and correction factor calculation during the priming stage using optical sensors to establish an initial baseline. However, the system does not rely solely on this preliminary calibration. Instead, it continuously measures volume throughout the entire procedure and updates correction factors as needed, ensuring that both initial accuracy and ongoing accuracy during fluid processing are maintained.
Solution Approach 2:
The patent implements continuous feedback by monitoring actual fluid volume changes during the apheresis procedure and comparing them against target volumes. The optical measurement system provides real-time feedback on volume deviations caused by pump tubing stretching, sheeting deformation, or other processing variations. The controller uses this feedback to dynamically calculate and apply correction factors, ensuring accurate results throughout the entire procedure rather than only during priming.
3Device complexity
If limited flow rates are used for calibration, then calculation simplicity is maintained, but representativeness of all potential flow rates is reduced
Solution Approach 1:
The patent eliminates the need for discrete calibration flow rate steps by implementing continuous volume measurement throughout the apheresis procedure. The optical sensors continuously monitor fluid volume at all operating flow rates, providing an ongoing dataset that naturally represents the full range of flow conditions encountered during the procedure. This continuous measurement approach maintains calculation simplicity while achieving comprehensive representativeness of all potential flow rates.
Data Source
AI summary
Systems and methods are provided for dynamic calibration and correction of the stroke volume of a pump. During a fluid processing procedure, the change in volume of a fluid in a container associated with a volume measurement system is calculated for a plurality of time periods. The standard deviation of the plurality of changes in volume is calculated, with it being determined that the volume measurement system is operating correctly when the standard deviation is below a target threshold. Upon determining that the volume measurement system is operating correctly, the stroke volume of the pump is calculated and a target change in volume of the fluid in the container is compared to an actual change in volume. When there is a difference between the two changes in volume, a correction factor is calculated, with the operation of the pump being adjusted based at least in part on the correction factor.