Sensor and method for measuring respiratory gas properties
AssigneeSendsor GmbH
InventorsDieter Helmut Dill, Matthias Maurberger, Alexander Scholz
Life of this patent
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Abstract
A sensor and method for measuring respiratory gas properties are presented. A thermal conductivity sensor is used to measure the thermal conductivity of a gas with unknown composition and/or mass flow rate at different temperatures. The measured thermal conductivities at different temperatures are compared with known thermal conductivities of gases at different temperatures. In an exemplary application the sensor and method are installed in a tube to determine a mass of respiratory air flowing through the tube and a concentration of CO2 therein.
Claims19
A respiratory gas sensing system, comprising:
- a thermal conductivity sensor disposed within a respiratory flow path including
- a first thermal conductivity sensing element comprising a first meander-shaped resistive wire having a plurality of first turns and
- a second thermal conductivity sensing element comprising a second meander-shaped resistive wire having a plurality of second turns,
- the first turns and the second turns being arranged adjacent to a common enveloping circle;
- and
- a processing module operatively connected to the thermal conductivity sensor,
- wherein the processing module measures a first thermal conductivity of a respiratory gas by operating the first thermal conductivity sensing element at a first temperature and
- wherein the processing module measures a second thermal conductivity of the respiratory gas by operating the second thermal conductivity sensing element at a second temperature, the second temperature being higher than the first temperature, and
- wherein operating the conductivity sensing elements includes applying electric power thereto and determining a voltage associated with the electric power required to maintain the respective temperature, and
- wherein the processing module determines a concentration of carbon dioxide within the respiratory gas in response to the measured first thermal conductivity and the measured second thermal conductivity.
A respiratory gas sensing system, comprising:
- a thermal conductivity sensor disposed within a respiratory flow path;
- and
- a processing module operatively connected to the thermal conductivity sensor,
- wherein the thermal conductivity sensor comprises:
- two outer thermal conductivity sensing elements, each comprising a first meander-shaped resistive wire having a plurality of first turns;
- and
- an inner thermal conductivity sensing element arranged between the two outer thermal conductivity sensing elements comprising a second meander-shaped resistive wire having a plurality of second turns,
- the first turns and the second turns being arranged adjacent to a common enveloping circle;
- and
- wherein the processing module measures a first thermal conductivity of a respiratory gas by operating the two outer thermal conductivity sensing elements at a first temperature and
- wherein the processing module measures a second thermal conductivity of the respiratory gas by operating the inner thermal conductivity sensing element at a second temperature, the second temperature being higher than the first temperature, and
- wherein operating the conductivity sensing elements includes applying electric power thereto and determining a voltage associated with the electric power required to maintain the respective temperature, and
- wherein the processing module determines a concentration of carbon dioxide within the respiratory gas in response to the measured first thermal conductivity and the measured second thermal conductivity.
Dependencies are inferred from the claim text.