Blood Circuit Temperature Modeling for Core Temperature Accuracy
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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 involving multiple flow rate measurements and thermal modeling to calculate the patient's core temperature by accounting for heat transfer rates and ambient temperature, using equations such as Tp = Tc1 * F1 - Tc2 * F2 / (F1 - F2), and iterative refinement with log mean temperature difference (LMTD) to correct for temperature changes along the blood circuit.
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 heat transfer between the blood and external environment causes temperature changes that lead to measurement inaccuracies
Solution Approach 1:
The system measures blood temperature at multiple different flow rates to obtain multiple temperature readings. By changing the flow rate parameter and collecting corresponding temperature data, the system can calculate the heat transfer rate and determine the actual core temperature through mathematical relationships, thereby resolving the measurement inaccuracy caused by heat transfer in the blood circuit
Solution Approach 2:
The system uses the temperature readings obtained at different flow rates as feedback to calculate the heat transfer rate between the blood circuit and external environment. This calculated heat transfer information is then used to correct the temperature measurements and accurately determine the patient's core temperature, forming a closed-loop feedback mechanism that compensates for heat transfer effects
2Measurement precision
If multiple flow rate measurements are taken to calculate core temperature, then measurement accuracy improves, but measurement time and system complexity increase
Solution Approach 1:
The system takes measurements at multiple flow rates (excessive action) to ensure accurate determination of the heat transfer rate and core temperature. By performing more measurements than a single-point measurement would require, the system obtains sufficient data to calculate temperature corrections accurately, accepting the additional time investment as necessary for achieving precise core temperature determination
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 allows for accurate estimation of core temperature, enabling effective temperature control and detection of abnormalities, such as fever, while minimizing the impact of heat exchange in the tubing on temperature measurements.
Implementation Method 1
a temperature sensor remote from the inlet measures a temperature of the blood flowing through the blood circuit
Implementation Method 2
heat gain or loss caused by heat transfer between the blood and the external environment of the blood circuit
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.