Extracorporeal Blood Temperature Sensing via Flow-Rate Thermal Modeling
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Solution Overview
Problem
Existing extracorporeal blood treatment systems face challenges in accurately measuring a patient's core temperature due to heat transfer changes in the blood circuit, making it difficult to maintain proper body temperature during treatments.
Innovation Solution
The system measures blood temperature at multiple flow rates and uses a thermal model to calculate the inlet temperature, accounting for heat transfer rates and ambient temperatures, allowing for accurate estimation of core temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a temperature sensor is placed remote from the blood inlet in the extracorporeal blood circuit, then the measurement device complexity is reduced, but the temperature measurement precision deteriorates due to heat transfer between blood and external environment
Solution Approach 1:
The system uses feedback by measuring blood temperature at multiple different flow rates and using these measurements to calculate correction factors that compensate for heat transfer effects. The controller adjusts the blood flow rate to establish different flow conditions, measures temperatures at each condition, and uses the temperature differences to determine the inlet temperature through calculation, thereby achieving accurate remote temperature measurement.
Solution Approach 2:
The system changes the flow rate parameter of blood through the extracorporeal circuit to create different flow conditions. By measuring temperature at multiple flow rates (e.g., first flow rate and second flow rate), the system can calculate the heat transfer characteristics and determine the inlet temperature. This parameter change approach allows the system to extract thermal information that would otherwise be inaccessible from a remote sensor position.
2Measurement precision
If blood flow rate is changed to multiple different flow rates for temperature measurement, then the core temperature estimation accuracy is improved, but the treatment time increases
Solution Approach 1:
The system performs temperature measurements at multiple flow rates, which is more than a single measurement would provide. By taking temperature measurements at different flow conditions (first flow rate and second flow rate), the system obtains sufficient data to calculate correction factors and determine inlet temperature accurately. This excessive measurement approach ensures accuracy while the controller manages the process efficiently.
Solution Approach 2:
The system performs preliminary temperature measurements at different flow rates to establish the thermal characteristics of the blood circuit before determining the actual inlet temperature. These preliminary measurements at controlled flow rates allow the controller to calculate heat transfer coefficients and correction factors that are then used to accurately determine the inlet temperature from remote sensor readings during actual treatment.
3Device complexity
If heat transfer between blood and external environment is not compensated, then the temperature control system simplicity is maintained, but the body temperature control reliability deteriorates
Solution Approach 1:
The system implements feedback control by measuring blood temperature at multiple flow rates, calculating the heat transfer effects based on temperature differences, and using this information to determine the actual inlet temperature. The controller uses this calculated inlet temperature as feedback to adjust the treatment parameters, ensuring reliable body temperature control despite heat transfer between blood and external environment.
Solution Approach 2:
The system replaces direct physical temperature measurement at the inlet (which would require complex positioning and insulation) with a computational approach. By measuring temperature remotely and using mathematical calculations based on multiple flow rate measurements, the system substitutes mechanical measurement challenges with computational thermodynamics, achieving reliable temperature control without direct inlet contact.
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 method provides an accurate estimation of core temperature, enabling effective temperature control during extracorporeal blood treatments and allowing for the detection of abnormal temperature conditions.
Implementation Method 1
a temperature sensor to measure a temperature of blood flowing through an attached blood circuit
Implementation Method 2
heat transfer between the blood and the external environment of the blood circuit
Implementation Method 3
heat gain or loss caused by heat transfer between the blood and the external environment
Data Source
AI summary
A patient's body temperature measurement may be made by varying the heat transfer dynamics of a fluid exiting the patient's body and fitting parameters of 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 fluid flow rate.