Dialyzer Recirculation Measurement via Substitution Flow Bolus
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Solution Overview
Problem
Current methods for measuring fistula and cardiopulmonary recirculation in extracorporeal blood treatment devices cannot distinguish between the two components of total recirculation, limiting the accuracy of dialysis efficiency assessment.
Innovation Solution
A device that changes the substitution rate and flow rate of liquid through the dialyzer membrane to create a temporary 'bolus' in the extracorporeal blood circuit, allowing for rapid measurement of fistula recirculation without interfering with cardiopulmonary recirculation, which is then calculated from the total recirculation measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current measurement methods are used to determine total recirculation, then the overall recirculation rate can be measured, but the individual components (fistula recirculation and cardiopulmonary recirculation) cannot be distinguished
Solution Approach 1:
The measurement process is segmented into two distinct phases: a first measurement phase that captures only fistula recirculation by creating a temporary bolus through substitution fluid interruption, and a second measurement phase that captures total recirculation including both fistula and cardiopulmonary components. This segmentation allows the individual components to be differentiated and calculated separately.
Solution Approach 2:
Before measuring total recirculation, the method performs a preliminary measurement of fistula recirculation by temporarily interrupting the substitution fluid supply. This preliminary action isolates the fistula recirculation component, which is then subtracted from the total recirculation measurement to determine the cardiopulmonary recirculation portion.
2Speed
If a temporary bolus is created by changing substitution rate and membrane flow rate, then rapid fistula recirculation measurement is enabled, but the measurement process becomes more complex
Solution Approach 1:
The substitution fluid supply is periodically interrupted for a predetermined time interval to create a temporary bolus effect. This periodic action allows the measurement system to capture fistula recirculation separately from cardiopulmonary recirculation, enabling rapid differentiation of the two components through timed measurement phases.
Solution Approach 2:
The flow rate through the dialyzer membrane is dynamically adjusted during the measurement process. By temporarily changing the substitution rate and membrane flow rate, the system creates a dynamic bolus condition that accelerates fistula recirculation detection, allowing faster measurement without requiring permanent structural modifications.
3Loss of time
If substitution fluid supply is interrupted to create a bolus, then fistula recirculation can be measured rapidly, but the treatment continuity is temporarily disrupted
Solution Approach 1:
The substitution fluid supply is interrupted only partially and temporarily for a predetermined short time interval, just enough to create the necessary bolus effect for measurement. This partial interruption minimizes the disruption to treatment continuity while still achieving the goal of rapid fistula recirculation measurement.
Solution Approach 2:
The blood pump continues to operate continuously throughout the measurement process, maintaining blood flow through the dialyzer. Additionally, the substitution fluid supply is restored immediately after the measurement interval, ensuring that the useful treatment action continues without significant interruption despite the temporary bolus creation.
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
Enables quick and accurate determination of fistula recirculation, allowing for separate quantification of fistula and cardiopulmonary recirculation, thereby improving the assessment of dialysis efficiency and vascular access quality.
Implementation Method 1
the transport of smaller molecular substances through the dialyzer membrane is essentially determined by the concentration differences (diffusion) between the dialysis fluid and the blood
Implementation Method 2
in hemofiltration (HF) substances dissolved in the plasma water, especially higher molecular weight substances, are effectively removed by a high fluid flow (convection) through the dialyzer membrane
Implementation Method 3
the patient's blood flows through the blood chamber. A semipermeable membrane separates the blood chamber and the dialysis fluid chamber
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a method and an apparatus for determining the percentage of fistula circulation and/or cardiopulmonary recirculation relative to the total fistula recirculation and cardiopulmonary recirculation during an extracorporeal blood treatment in which substitution liquid is fed to the blood at a specific substitution rate upstream or downstream of the first chamber (3) of the dialyzer (1) or filter, while liquid is withdrawn from the blood at a specific flow rate via the membrane (2) of the dialyzer (1) or filter. The method according to the invention and the apparatus according to the invention are characterized in that the substitution rate Qs is modified by a predefined amount upstream of downstream of the dialyzer or filter while the flow rate QFM of the liquid that is withdrawn through the dialyzer membrane is modified. The blood volume RBV(t) or a variable correlated with the blood volume, e.g. the hematocrit Hct(t), is determined before and after modifying the substitution rate or the flow rate of the liquid withdrawn through the dialyzer or filter membrane in order to calculate fistula recirculation RAon the basis of the blood volume or the hematocrit. In addition, the sum R of fistula recirculation (RA) and cardiopulmonary recirculation (RCP) is determined. The percentage of fistula recirculation (RA) and/or cardiopulmonary recirculation (RCP) relative to the total fistula recirculation (RA) and/or cardiopulmonary recirculation (RCP) is calculated from the determined fistula recirculation (RA) and the sum R of fistula recirculation (RA) and cardiopulmonary recirculation (RCP).