Dialysis Recirculation Measurement via Flow Rate Variation
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Solution Overview
Problem
Current methods for measuring recirculation during extracorporeal blood treatment, such as thermodilution, cannot differentiate between fistula recirculation and cardiopulmonary recirculation without reversing blood flow, limiting their ability to assess the quality of vascular access and dialysis efficiency effectively.
Innovation Solution
A device that determines fistula recirculation and cardiopulmonary recirculation by measuring the change in blood flow rates, using temperature changes induced by a temperature bolus in the dialysis fluid, allowing for non-invasive calculation of these components without reversing blood flow, utilizing known methods like thermodilution for data analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermodilution method is used to measure recirculation, then recirculation can be measured, but fistula recirculation and cardiopulmonary recirculation cannot be differentiated
Solution Approach 1:
The patent segments the total recirculation measurement into two distinct components: fistula recirculation and cardiopulmonary recirculation. By performing measurements at different blood flow rates (first blood flow rate and second blood flow rate) and using the differences to calculate separate recirculation fractions, the method divides the mixed recirculation signal into identifiable parts, enabling differentiation between the two types of recirculation while maintaining measurement precision.
2Loss of information
If blood flow is reversed to measure recirculation components, then differentiation is possible, but the procedure becomes more complex and time-consuming
Solution Approach 1:
The patent applies dynamics by varying the blood flow rate through the dialyzer during measurements. Instead of reversing blood flow direction, the system dynamically adjusts flow rates between a first blood flow rate and a second blood flow rate. This dynamic approach allows the system to capture different recirculation characteristics at different flow conditions, enabling component differentiation without the complexity of flow reversal procedures.
3Measurement precision
If multiple measurements at different blood flow rates are taken, then recirculation components can be differentiated, but measurement time increases
Solution Approach 1:
The patent ensures continuity of useful action by performing recirculation measurements during the ongoing dialysis treatment without interrupting blood flow or requiring additional procedural steps. The system continuously monitors temperature changes in the dialysate at different blood flow rates, allowing recirculation component differentiation to occur seamlessly within the existing treatment timeline, thereby minimizing time loss while maintaining measurement precision.
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 accurate determination of fistula and cardiopulmonary recirculation fractions, improving the assessment of vascular access quality and dialysis efficiency by providing separate measurements for each component, thus enhancing the monitoring of dialysis treatments.
Implementation Method 1
A method for recirculation measurement known as thermodilution is known from EDTNA-ERCA Journal 19, 6 (1993). In the known method, a short-term drop in temperature is initiated in the dialysis fluid circuit, which is transferred to the venous branch of the extracorporeal circuit and leads to a detectable jump in temperature in the arterial branch of the extracorporeal circuit when recirculation occurs.
Data Source
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AI summary
The invention relates to a method for determining the recirculation in a fistula and/or the cardiopulmonary recirculation part during an extracorporeal blood treatment, according to which the blood to be treated flows in an extracorporeal blood circuit (I) through a blood chamber (8) of a dialyser (6) split by a semi-permeable membrane (7) into the blood chamber and a dialysis liquid chamber (9), and dialysis liquid flows in a dialysis liquid path (II) through the dialysis liquid chamber of the dialyser. The invention also relates to a device for determining the recirculation in a fistula and/or the cardiopulmonary recirculation part, and to a blood treatment device comprising a device for determining the fistula recirculation and/or the cardiopulmonary recirculation part. The method and device according to the invention are based on the fact that the sum of the fistula recirculation (RA) and the cardiopulmonary recirculation part (RCP), i.e. the total recirculation (R), is determined for two blood flow rates which differ from each other. The fistula recirculation and/or the cardiopulmonary recirculation part are then determined from the recirculation for the two blood flow rates. The first recirculation measurement is carried out for a high blood flow (QBH) for which a fistula recirculation can occur, while the second measurement is carried out for a low blood flow (QBL) for which a fistula recirculation does not occur. These two measuring values form the basis of the determination of the fistula recirculation and/or the cardiopulmonary recirculation part.