Non-Invasive Analyte Sensor Thermal Equilibrium Control
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Solution Overview
Problem
Existing non-invasive sensors for measuring blood gas partial pressures, such as CO2, often cause skin burns and unwanted vasodilation due to heating, and can interfere with perfusion measurements, particularly in clinical situations where minimizing heat influence is crucial.
Innovation Solution
An apparatus with a thermally conductive part and a thermal sensor to maintain thermal equilibrium between the tissue and the analyte sensor, using a controller to minimize temperature differences and prevent heat flow, allowing for accurate CO2 measurements without heating the skin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor contact surface is heated to 40-44°C to achieve local vasodilation and arterialization of the capillary bed for accurate CO2 measurement, then the measurement precision of arterial CO2 values is improved, but the risk of skin burns and unwanted side effects increases
Solution Approach 1:
A thermally insulating layer is introduced as an intermediary between the heating element and the skin tissue. This layer allows controlled heat transfer to achieve the necessary temperature for accurate CO2 measurement while preventing excessive heat from causing skin burns. The insulating layer acts as a mediator that regulates the thermal interaction between the sensor and the patient's skin.
2Measurement precision
If the skin is heated to create local vasodilation for accurate blood gas measurement, then the measurement precision of arterial CO2 values is improved, but the skin structure is altered and perfusion measurement becomes compromised
Solution Approach 1:
The heating temperature is made dynamically adjustable rather than fixed. The system can adapt the heating level based on real-time feedback from temperature sensors and perfusion measurements, allowing the skin structure to maintain its natural state while still achieving sufficient warmth for accurate blood gas measurement. This dynamic control prevents excessive vasodilation that would alter skin structure.
3Measurement precision
If heating is applied to enhance tissue perfusion for better sensor contact, then the measurement precision is improved, but the energy consumption increases and heat removal capability is compromised in certain clinical conditions
Solution Approach 1:
A feedback control system is implemented where temperature sensors continuously monitor the skin temperature and perfusion levels, and this information is fed back to the heating element controller. The system automatically adjusts the heating power to maintain optimal measurement conditions without excessive energy consumption. This feedback mechanism ensures heating is applied only when and where necessary, reducing overall energy usage.
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 prevents skin burns and maintains high accuracy in blood gas measurements while minimizing the influence on local perfusion, allowing for continuous monitoring without altering tissue perfusion.
Implementation Method 1
a first thermally conductive part and a first thermal sensor disposed at the first thermally conductive part, the first thermally conductive part being adapted for thermally connecting with the tissue of a patient
Implementation Method 2
controlling the power supplied to the heater so as to minimize a temperature difference between the temperatures determined by the first and second thermal sensors to maintain a thermal equilibrium between the tissue and the second thermally conductive part
Implementation Method 3
the first thermal sensor being operable to determine a temperature indicative of a temperature at a location on a surface of a tissue of a patient
Implementation Method 4
an analyte sensor operable to generate a sensor signal indicative of a concentration of the analyte
Data Source
Figure 1~3
Figure 4A~4B
Figure 5
AI summary
A sensor and an apparatus for non-invasive measurement of an analyte concentration, the apparatus comprising: a first thermal sensor (106) operable to determine a temperature indicative of a temperature at a location on a skin (122) of a subject, an analyte sensor (103) operable to generate a measurement indicative of a concentration of the analyte, a heater (109); a controller (216) operable to receive a temperature signal from at least the first thermal sensor and to adjust the heater to maintain a thermal equilibrium at said location on the skin; and a processor (213) configured to convert the measurement to a calculated analyte concentration value at a predetermined temperature.