Extracorporeal Blood Circuit Core Temperature Estimation
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Solution Overview
Problem
Existing extracorporeal blood treatment systems face challenges in accurately measuring and controlling patient core temperature due to heat transfer issues along the blood circuit, particularly when temperature sensors are remote from the patient, leading to inaccuracies in temperature estimation.
Innovation Solution
A method that measures blood temperature at two different flow rates and uses a thermal model to calculate the core temperature, assuming a constant heat transfer rate, and iteratively refines the estimate using ambient temperature calculations, allowing for accurate core temperature estimation and correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors are placed remote from the patient in the blood circuit, then device complexity and ease of operation are improved, but measurement precision deteriorates due to heat transfer along the blood circuit
Solution Approach 1:
The patent introduces an intermediary computational model that acts as a mediator between the remote temperature sensor and the actual patient core temperature. The model uses measured blood temperature, blood flow rate, and thermal properties of the blood circuit as inputs to calculate the unknown patient core temperature, effectively bridging the gap created by remote sensor placement without requiring complex hardware modifications.
Solution Approach 2:
The patent replaces the direct mechanical/physical contact measurement approach (placing sensor at patient access) with a computational/algorithmic approach. Instead of relying on direct thermal contact, the system uses mathematical modeling and calculations based on thermal conduction principles to infer core temperature from remote measurements, substituting physical proximity with computational intelligence.
2Ease of operation
If temperature sensors are placed remote from the patient, then ease of operation is improved, but measurement precision deteriorates due to heat loss or gain in the blood circuit
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors blood temperature at the remote sensor location and uses this information to iteratively refine the core temperature estimate. The calculated core temperature feeds back into the thermal model to improve subsequent measurements, allowing the system to compensate for heat transfer effects dynamically and maintain high measurement precision despite remote sensor placement.
Solution Approach 2:
The patent changes the measurement parameters by introducing blood flow rate as a critical variable in the temperature calculation. By measuring temperature at multiple flow rates and using the thermal model to account for flow-dependent heat transfer, the system transforms a potentially inaccurate single-point measurement into a precise multi-parameter estimation, improving accuracy while maintaining ease of operation.
3Loss of time
If blood flow rate is increased to improve measurement response time, then productivity is improved, but measurement precision deteriorates due to reduced heat transfer effect
Solution Approach 1:
The patent applies partial action by using multiple discrete flow rate measurements rather than continuous high-flow measurement. The system temporarily adjusts flow to specific levels for measurement purposes, then returns to normal operation, achieving sufficient measurement speed without subjecting the patient to excessive or continuously high blood flow rates that would reduce thermal effects and measurement accuracy.
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 enables precise core temperature measurement and control, even with remote temperature sensors, by accounting for heat transfer variations and ambient temperature fluctuations, improving patient temperature management during treatments.
Implementation Method 1
heat transfer between the blood and the external environment of the blood circuit
Implementation Method 2
heat transfer rate is the same for two flow rate conditions
Implementation Method 3
heat transfer coefficients which are influenced by external forced convection as well as thermally-driven natural convection
Data Source
Figure 1~3A
Figure 3B~3C
Figure 3D~3E
AI summary
A core temperature measurement may be made by varying the heat transfer dynamics of a blood circuit and fitting parameters of a blood circuit heat transfer configuration to measurements under the varied conditions. Then the input temperature of the patient core can be extracted from the model and a current temperature measurement remote from the patient core and optionally other measurements such as blood flow rate.