Blood Delivery Pump Flow Rate Calibration via Priming Correction
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Solution Overview
Problem
Current methods for calibrating blood delivery pumps in renal replacement therapies are time-consuming, inaccurate, and prone to errors due to production batch variations in disposable tubing, especially when dealing with negative inlet pressures that can cause tube deformation and air bubble issues during priming.
Innovation Solution
A method involving a fluid-filled container connected to the blood treatment apparatus, where the pump is primed at a theoretical delivery rate, and a correction factor is determined by measuring fluid loss during this process, allowing for accurate calibration and adjustment of the pump's flow rate before therapy, independent of air bubble removal and tube deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods are used to determine pump flow rate, then measurement can be performed, but the process is time-consuming and inaccurate due to production batch variations in tubing
Solution Approach 1:
The patent applies preliminary action by performing calibration during the mandatory priming process itself. The method measures the actual volume delivered by the pump during priming (when the blood line is being filled with fluid) and uses this measurement to calculate a correction factor. This eliminates the need for separate calibration steps, as the calibration is performed in advance as part of the setup procedure, thereby reducing calibration time while maintaining accuracy.
Solution Approach 2:
The patent implements feedback by measuring the actual fluid volume delivered during priming and using this measurement to calculate a correction factor that adjusts the theoretical delivery rate. The system continuously monitors the relationship between pump runtime and actual volume delivered, and uses this feedback to compensate for manufacturing variations in tubing dimensions, ensuring accurate flow rate measurement throughout operation.
2Measurement precision
If calibration is performed during priming with air bubble removal, then flow rate can be measured, but tube deformation from negative pressure causes measurement errors
Solution Approach 1:
The patent extracts the calibration measurement from the problematic air bubble removal phase and performs it during the fluid-filled priming phase instead. By measuring volume delivery when the line is being filled with priming fluid (before air bubbles are present and before negative pressure causes tube collapse), the method obtains accurate baseline data for calculating the correction factor without the interference of tube deformation.
Solution Approach 2:
The calibration measurement is performed as a preliminary action during the initial fluid filling phase of priming, before negative pressure conditions develop. The system captures the relationship between pump runtime and volume delivered when the tubing is still plump and stable, then uses this preliminary measurement to establish the correction factor that compensates for subsequent tube deformation during actual blood pumping.
3Ease of manufacture
If peristaltic pump with disposable tubing is used, then blood delivery is achieved, but production batch variations cause flow rate errors
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the pump's delivery rate parameter based on measured performance. Instead of relying on fixed theoretical values that assume perfect tubing dimensions, the system measures actual volume delivered during priming and uses this information to calculate a correction factor. This correction factor modifies the relationship between pump speed and actual flow rate, compensating for manufacturing variations in each batch of disposable tubing.
Data Source
AI summary
Flow rate of a blood delivery pump of a blood treatment apparatus is determined and adjusted by connecting a fluid filled container with an extracorporeal blood line of the blood treatment apparatus, performing a priming step to prime the extracorporeal blood line by driving the blood delivery pump at a predetermined theoretical delivery rate to deliver fluid from the filled container into the extracorporeal blood line, determining the loss of fluid of the fluid filled container due to delivery of fluid into the extracorporeal blood line during priming, and determining a correction factor by comparison of a value for an amount of fluid delivered under the theoretical delivery rate with a value for the amount of fluid actually delivered.