Dialyzer Absorbance Monitoring for Kt/V Calculation
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Solution Overview
Problem
Current methods for determining the Kt/V value during renal replacement therapy are inefficient, prolonging treatment duration and requiring additional equipment, as they rely on recirculating dialysis fluid to establish a concentration balance, which takes significant time and exceeds measurement ranges.
Innovation Solution
A device that calculates the equilibrated Kt/V value by measuring absorbance in the dialysate and blood flow, using the dialyzer's permeability and surface area product to determine blood absorbance without recirculation, allowing for real-time monitoring without extending treatment time or increasing equipment costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dialysis fluid is recirculated to establish concentration balance for determining Kt/V value, then measurement accuracy is improved, but treatment duration is prolonged
Solution Approach 1:
The device performs preliminary calibration by measuring absorbance at multiple wavelengths to determine extinction coefficients before actual treatment. This preliminary characterization of the measuring cell and optical path enables direct calculation of concentration during treatment without requiring recirculation to establish equilibrium, thus maintaining measurement accuracy while avoiding extended treatment time
Solution Approach 2:
The invention replaces the mechanical recirculation process (physically circulating dialysis fluid to establish concentration balance) with an optical measurement system that uses absorbance spectroscopy at multiple wavelengths. This substitution allows direct determination of concentration based on optical properties, eliminating the need for time-consuming recirculation while maintaining measurement precision
2Measurement precision
If recirculation is performed multiple times during patient treatment, then concentration balance is established, but treatment time increases significantly
Solution Approach 1:
The invention replaces repeated mechanical recirculation operations with a single optical measurement approach. By measuring absorbance at multiple wavelengths and using the determined extinction coefficients, the system calculates concentration directly without requiring multiple recirculation cycles to establish and re-establish concentration balance, thereby preventing significant time loss
Solution Approach 2:
The device creates an optical copy or model of the concentration relationship by measuring absorbance at multiple wavelengths and establishing the relationship between absorbance ratios and concentration through calibration. This optical model allows direct determination of concentration during treatment without physically recirculating fluid multiple times, thus avoiding time loss while maintaining measurement accuracy
3Measurement precision
If full amount of urinary substances is measured without dilution, then measurement range is exceeded, but concentration accuracy is maintained
Solution Approach 1:
The device uses partial action by measuring absorbance at selectively chosen wavelengths where the optical density falls within the linear range of the detector. Instead of attempting to measure the full absorbance range in a single measurement, the system selects wavelengths that provide optimal signal-to-noise ratio while remaining within measurement capabilities, thus maintaining concentration accuracy without requiring additional dilution equipment
Solution Approach 2:
The invention changes the measurement parameter from total absorbance to absorbance at specific wavelengths. By measuring at multiple discrete wavelengths and using the ratios of these absorbance values, the system determines concentration without being constrained by the absolute magnitude of total absorbance. This parameter transformation allows accurate measurement of high concentrations without exceeding device measurement range or requiring additional dilution equipment
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 direct and efficient determination of the equilibrated Kt/V value during therapy, minimizing treatment duration and reducing patient burden, while maintaining accurate measurements without the need for extensive equipment upgrades.
Implementation Method 1
a measuring device (220) for determining an absorbance (A) of the dialysis liquid downstream of the dialyzer
Implementation Method 2
the waste products, including toxic substances, are carried through the membrane from the patient's blood to the dialysis fluid by diffusion and convection
Implementation Method 3
the waste products, including toxic substances, are carried through the membrane from the patient's blood to the dialysis fluid by diffusion and convection
Data Source
Figure 1
AI summary
The invention relates to a device for the extracorporeal blood treatment using a dialyzer, which is divided by a semi-permeable membrane into a first and a second chamber, wherein the first chamber is arranged in a dialysis fluid path and the second chamber can be connected to the blood circulation system of a patient by means of a blood supply line and a blood discharge line, a feed for fresh dialysis fluid, a drain for used dialysis fluid, a means for determining a flow (QBlut) in the blood supply and blood discharge line, a means for determining a flow (QDialysat) in the dialysis fluid path, and a measurement unit arranged in the drain for determining the absorbance (ADialysat) of the used dialysis fluid flowing through the drain, wherein the measurement unit has at least one radiation source and a detector system for detecting the intensity of the electromagnetic radiation. A memory, in which the formula (I) for the one absorbance (ABlut) is stored, and an arithmetic unit, with which the absorbance in the blood supply and blood discharge lines can be determined using the absorbance (ADialysat), the flow (QDialysat) and the flow (QBlut), are also provided.