Blood Circuit Thermal Modeling for Remote Core Temperature Sensing
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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 variations in the blood circuit, especially when temperature sensors are located remotely from the patient, leading to inaccuracies in temperature readings.
Innovation Solution
A method that involves measuring blood temperature at different flow rates and using thermal models to calculate the core temperature, incorporating heat transfer coefficients and ambient temperature estimation, allowing for recursive calculations to refine the inlet temperature estimation and correct for heat exchange biases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors are located remotely from the patient in the blood circuit, then the system can measure blood temperature, but the temperature readings become inaccurate due to heat transfer variations in 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 patient's core temperature. The model uses measured blood temperature, flow rate data, and thermal parameters to calculate and infer the core temperature that would exist if a sensor were placed directly at the patient's core, thereby eliminating the need for complex sensor placement while maintaining measurement accuracy
Solution Approach 2:
The patent replaces the mechanical approach of placing temperature sensors directly at the patient's core with a computational/algorithmic system. Instead of using physical sensors at the measurement location, the system uses mathematical models and processing to substitute for the physical measurement, converting a direct physical measurement problem into an indirect computational inference problem
2Measurement precision
If temperature sensors are placed close to the patient to improve measurement accuracy, then temperature readings are more accurate, but the system cannot account for heat exchange between blood and external environment in the blood circuit
Solution Approach 1:
The patent converts the harmful effect of heat transfer between blood and external environment into a beneficial measurement tool. By measuring the temperature difference caused by heat exchange and combining it with flow rate data, the system uses this previously problematic heat transfer to calculate and infer the original core temperature, turning an interference factor into a useful diagnostic parameter
Solution Approach 2:
The system implements a feedback mechanism where the measured temperature at the remote sensor is continuously compared with the calculated core temperature. This feedback loop allows the system to adjust and refine its measurements and calculations, using the temperature differential information to improve the accuracy of core temperature estimation while accounting for environmental heat transfer effects
3Measurement precision
If multiple temperature measurements are taken at different flow rates to calculate core temperature, then accurate core temperature estimation is achieved, but the treatment time increases due to multiple measurements
Solution Approach 1:
The patent applies preliminary action by performing temperature measurements at different flow rates during the initial setup phase or at convenient intervals rather than continuously during the entire treatment. The system establishes the thermal model parameters in advance, allowing for accurate core temperature estimation without requiring multiple measurements throughout the treatment duration, thereby minimizing time loss
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 accurate estimation of patient core temperature, even with remote temperature sensors, by accounting for heat transfer variations, thus improving temperature control and detection of abnormal conditions during treatments.
Implementation Method 1
a temperature sensor remote from the inlet... measure a blood inlet temperature... using a sensor that is remote from the inlet
Implementation Method 2
heat transfer between the blood and the external environment of the blood circuit... the blood cools within the tube
Data Source
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.