Dialysis Fluid Uremic Toxin Detection via pH-Dependent Spectral Subtraction

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Solution Overview

Problem

Current dialysis technologies face challenges in quantitatively determining the concentration of uremic toxins like creatinine and uric acid in dialysis fluid, especially when their absorption bands overlap, leading to inaccurate measurement of dialysis quality and nutritional status assessment.

Innovation Solution

The method involves using an optical absorption sensor to detect extinction signals at different pH values, generating a processing signal by subtracting spectra recorded at these pH values, allowing for the accurate determination of uremic toxin concentrations without enzymes or reagents, utilizing the pH-dependent absorption properties of substances to isolate creatinine and uric acid concentrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If optical absorption sensors are used to measure uremic toxin concentrations, then measurement capability is provided, but measurement precision deteriorates when absorption bands overlap

Engineering Contradiction:
Improveconcentration determination accuracyVSAvoidabsorption band overlap
Core Design Contradiction:
Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent applies dynamics by changing the pH value of the dialysis fluid dynamically during measurement. By adjusting pH between 6.8-7.4, the absorption characteristics of uremic toxins like creatinine and uric acid change, allowing differentiation of their overlapping absorption bands through multiple measurements at different pH levels

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent changes the pH parameter of the dialysis fluid to alter the absorption properties of uremic toxins. By measuring absorption at different pH values, the system can distinguish between overlapping absorption bands of different substances, thereby improving measurement precision without requiring complex multi-wavelength sensors

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If enzymes or reagents are used to determine creatinine concentration, then measurement specificity improves, but device complexity and cost increase

Engineering Contradiction:
Improvecreatinine concentration accuracyVSAvoidenzyme or reagent system
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent employs self-service by utilizing the inherent pH-dependent absorption properties of uremic toxins themselves for identification and measurement. No external enzymes, reagents, or additional chemicals are required - the system uses the natural spectral characteristics of the analytes combined with pH adjustment to achieve specific identification and quantification

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces biochemical measurement systems (enzymes, reagents) with a physical-chemical approach using optical absorption spectroscopy combined with pH control. This substitution eliminates the need for biological components while achieving equivalent or superior measurement capability through physical property manipulation

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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

This approach provides high measurement accuracy for creatinine and uric acid concentrations in dialysis fluid, enabling effective monitoring of dialysis quality and nutritional status without the need for enzymes or expensive multi-wave absorption sensors.

Implementation Method 1

Some uremic toxins absorb light in the range between 190 nm and 350 nm. This absorption can be used to determine the concentration of uremic toxins in the discharge dialysis fluid. Light absorption can be measured using optical sensors, such as optical absorption sensors

Methodology Applied
Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

By changing a pH value of the dialysis fluid and/or removed body fluid and/or excreted body fluid and/or urine and generating a processing signal from spectra recorded at the different pH values, it is possible to determine the concentration of selected substances, in particular creatinine and/or uric acid, dissolved in the dialysis fluid and/or removed body fluid and/or excreted body fluid and/or urine

Methodology Applied
Scientific EffectpH-dependent absorption: Absorption (EM radiation)

Data Source

PatentEP2942614B1Device and device control method for quantitatively determining the concentration of selected substances in a liquid filtered out of a patient's body
Publication Date: 2021.01.20 B BRAUN AVITUM
  • EP2942614B1 patent drawingFigure 1~2
  • EP2942614B1 patent drawingFigure 3
  • EP2942614B1 patent drawingFigure 4

AI summary

To determine a substance in excreted/removed fluid or used dialysis fluid, and in particular to determine a quality measure for dialysis, preferably the concentration of selected pollutants, and/or to determine a total amount of uremic toxins removed during dialysis with a dialysis device (1), the analysis device according to the invention and the device control method employed comprise the following: detection of at least one first extinction signal of the excreted/removed fluid or the used dialysis fluid at at least one predetermined analysis wavelength at a defined first pH value of the fluid by an absorption sensor (10), setting of a second pH value of the fluid that differs from the first pH value by a pH setting device (9; 13;15) Detection of at least one second extinction signal of the liquid at at least one predetermined analysis wavelength at the second pH value by the absorption sensor (10), processing/comparison of the two extinction signals for the first and second pH values ​​and determination of an absolute concentration of the substance dissolved in the liquid.;