METHOD AND APPARATUS FOR MONITORING A LEVEL OF A GASEOUS SPECIES OF INTEREST
First Claim
1. A detector configured to monitor a level of a gaseous molecular species within a flow of breathable gas, the detector comprising:
- a first source configured to emit mid-infrared electromagnetic radiation;
a second source configured to emit near-infrared electromagnetic radiation;
source optics configured to combine mid-infrared electromagnetic radiation emitted by the first source and near-infrared electromagnetic radiation emitted by the second source into a coaxial beam, and to direct the coaxial beam across a flow path of a flow of breathable gas that communicates with an airway of a subject;
sensor optics configured to receive electromagnetic radiation in the coaxial beam that has traversed the flow path, and to divide the received electromagnetic radiation into first radiation that includes mid-infrared electromagnetic radiation and second radiation that includes near-infrared electromagnetic radiation;
a first radiation sensor configured to receive the first radiation, and to generate output signals conveying information related to a parameter of the mid-infrared electromagnetic radiation in the first radiation;
a second radiation sensor configured to receive the second radiation, and to generate output signals conveying information related to a parameter of the near-infrared electromagnetic radiation in the second radiation; and
a processor configured to determine a level of a gaseous molecular species within the flow of breathable gas in the flow path based on the output signals generated by the first radiation sensor and the second radiation sensor such that the output signals generated by the second radiation sensor are implemented to compensate optical loss through the flow path.
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Abstract
Gas measurement detectector configured to monitor a level of a gaseous molecular species within a flow path (18) of a flow of breathable gas that communicates with an airway of a subject is performed by infrared spectroscopy. Rather than using an individual source (20) to generate electromagnetic radiation at reference and measurement wavelengths, a near-infrared electromagnetic radiation source (22) is used to generate reference electromagnetic radiation. The detector comprising: a first source (20) configured to emit mid-infrared electromagnetic radiation; a second source (22) configured to emit near-infrared electromagnetic radiation; source optics (24) configured to combine mid-infrared and near-infrared electromagnetic radiation emitted by the first and second source into a coaxial beam, and to direct the coaxial beam across the flow path (18); sensor optics (38) configured to receive electromagnetic radiation in the coaxial beam that has traversed the flow path (18), and to divide the received electromagnetic radiation into first radiation that includes mid-infrared electromagnetic radiation and second radiation that includes near-infrared electromagnetic radiation; a first radiation sensor (40) configured to receive the first radiation, and to generate output signals conveying information related to a parameter of the mid-infrared electromagnetic radiation in the first radiation; a second radiation sensor (42) configured to receive the second radiation, and to generate output signals conveying information related to a parameter of the near-infrared electromagnetic radiation in the second radiation; and a processor (36) configured to determine a level of a gaseous molecular species within the flow of breathable gas in the flow path based on the output signals generated by the first radiation sensor (40) and the second radiation sensor (42) such that the output signals generated by the second radiation sensor (42) are implemented to compensate optical loss through the flow path. Preferably fluctuations in irradiance of the source (20) generating the electromagnetic radiation at the measurement wavelength is compensated for based on a measurement of resistance through the source (20).
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Citations
15 Claims
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1. A detector configured to monitor a level of a gaseous molecular species within a flow of breathable gas, the detector comprising:
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a first source configured to emit mid-infrared electromagnetic radiation; a second source configured to emit near-infrared electromagnetic radiation; source optics configured to combine mid-infrared electromagnetic radiation emitted by the first source and near-infrared electromagnetic radiation emitted by the second source into a coaxial beam, and to direct the coaxial beam across a flow path of a flow of breathable gas that communicates with an airway of a subject; sensor optics configured to receive electromagnetic radiation in the coaxial beam that has traversed the flow path, and to divide the received electromagnetic radiation into first radiation that includes mid-infrared electromagnetic radiation and second radiation that includes near-infrared electromagnetic radiation; a first radiation sensor configured to receive the first radiation, and to generate output signals conveying information related to a parameter of the mid-infrared electromagnetic radiation in the first radiation; a second radiation sensor configured to receive the second radiation, and to generate output signals conveying information related to a parameter of the near-infrared electromagnetic radiation in the second radiation; and a processor configured to determine a level of a gaseous molecular species within the flow of breathable gas in the flow path based on the output signals generated by the first radiation sensor and the second radiation sensor such that the output signals generated by the second radiation sensor are implemented to compensate optical loss through the flow path. - View Dependent Claims (2, 3, 4, 5)
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6. A method of monitoring a level of a gaseous molecular species within a flow of breathable gas with a detector that includes a first source, a second source, source optics, sensor optics, a first radiation sensor, a second radiation sensor, and a processor, the method comprising:
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emitting mid-infrared electromagnetic radiation from the first source; emitting near-infrared electromagnetic radiation from the second source; combining, with the source optics, mid-infrared electromagnetic radiation emitted by the first source and near-infrared electromagnetic radiation emitted by the second source into a coaxial beam; directing, with the source optics, the coaxial beam across a flow path of the flow of breathable gas that communicates with an airway of a subject; dividing, with the sensor optics, electromagnetic radiation in the coaxial beam that has traversed the flow path into first radiation that includes mid-infrared electromagnetic radiation and second radiation that includes near-infrared electromagnetic radiation; generating, with the first radiation sensor, output signals conveying information related to a parameter of the mid-infrared electromagnetic radiation in the first radiation; generating, with the second radiation sensor, output signals conveying information related to a parameter of the near-infrared electromagnetic radiation in the second radiation; and determining, by the processor, a level of a gaseous molecular species within the flow of breathable gas in the flow path based on the output signals generated by the first radiation sensor and the second radiation sensor such that the output signals generated by the second radiation sensor are implemented to compensate optical loss through the flow path. - View Dependent Claims (7, 8, 9, 10)
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11. A system for monitoring a level of a gaseous molecular species within a flow of breathable gas, the system comprising:
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means for emitting mid-infrared electromagnetic radiation; means for emitting near-infrared electromagnetic radiation; means for combining emitted mid-infrared electromagnetic radiation and emitted near-infrared electromagnetic radiation into a coaxial beam; means for directing the coaxial beam across a flow path of the flow of breathable gas that communicates with an airway of a subject; means for dividing electromagnetic radiation in the coaxial beam that has traversed the flow path into first radiation that includes mid-infrared electromagnetic radiation and second radiation that includes near-infrared electromagnetic radiation; means for generating output signals conveying information related to a parameter of the mid-infrared electromagnetic radiation in the first radiation; means for generating output signals conveying information related to a parameter of the near-infrared electromagnetic radiation in the second radiation; and means for determining a level of a gaseous molecular species within the flow of breathable gas in the flow path based on the output signals generated by the first radiation sensor and the second radiation sensor such that the output signals generated by the second radiation sensor are implemented to compensate optical loss through the flow path. - View Dependent Claims (12, 13, 14, 15)
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Specification