Method and apparatus for monitoring a level of a gaseous species of interest

• US 10,458,903 B2
• Filed: 01/14/2014
• Issued: 10/29/2019
• Est. Priority Date: 01/17/2013
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Jiang, Zhi-Xing, Pierry, Anthony
• Primary Examiner(s): Remaly, Mark D
• Application Number:
  US14/761,506
• Publication Number:
  US 20150338340A1
• Time in Patent Office: 2,114 Days
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves
• CPC Class Codes: A61B 5/082 Evaluation by breath analysis, e.g. determination of the chemical composition of exhaled breath A61B5/083, A61B5/091 take precedence
• CPC Class Codes: A61M 2016/102 Measuring a parameter of the content of the delivered gas
• CPC Class Codes: A61M 2016/103 the CO2 concentration
• CPC Class Codes: A61M 2205/3313 used specific wavelengths
• CPC Class Codes: G01J 3/108 for measurement in the infrared range
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 2021/3181 using LEDs
• CPC Class Codes: G01N 2021/8578 Gaseous flow IR analysers G01N21/8507
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 21/359 using near infrared light
• CPC Class Codes: G01N 2201/0612 Laser diodes
• CPC Class Codes: G01N 2201/062 LED's
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath

Abstract

A gas measurement detector includes first and second sources emitting mid- and near-infrared electromagnetic radiation respectively; source optics combining mid- and near-infrared electromagnetic radiation emitted by the first and second sources into a coaxial beam directed across a flow path of a flow of breathable gas; sensor optics 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; first and second radiation sensors generating output signals conveying information related to a parameter of the mid-infrared electromagnetic radiation in the first radiation and a parameter of the near-infrared electromagnetic radiation in the second radiation, respectively; and a processor determining a level of a gaseous molecular species based on the output signals with the output signals generated by the second radiation sensor compensating optical loss through the flow path.

Claims

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;

wherein the gaseous molecular species is carbon dioxide, nitrous oxide, water vapor, or anesthetic gas.

2. The detector of claim 1, further comprising a source monitoring apparatus configured to generate output signals conveying information related to electrical resistance through the first source, and wherein the processor is further configured such that the determination of the level of the gaseous molecular species is further based on the output signals generated by the source monitoring apparatus to account for the electrical resistance through the first source.

3. The detector of claim 2, wherein determining the level of the gaseous molecular species based on the output signals generated by the source monitoring apparatus effectively adjusts the level determination for the irradiance of the first source.

4. The detector of claim 1, wherein the second radiation sensor includes a photodiode.

5. The detector of claim 4, wherein the first radiation sensor includes a PbSe substrate, a pyrometer, or a thermopile.

6. The detector of claim 5, wherein the second radiation sensor includes the photodiode comprising an InGaAs or Ge photodiode.

7. The detector of claim 1, wherein the second source includes at least one of a light emitting diode or a laser diode.

8. The detector of claim 1, wherein:

the first radiation sensor is configured to generate the output signals conveying information related to an intensity of the mid-infrared electromagnetic radiation in the first radiation;

the second radiation sensor is configured to generate the output signals conveying information related to an intensity of the near-infrared electromagnetic radiation in the second radiation; and

the processor is configured to determine the level of the 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 including normalizing the intensity of the mid-infrared electromagnetic radiation in the first radiation using the intensity of the near-infrared electromagnetic radiation in the second radiation to compensate optical loss through the flow path.

9. 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:

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.

10. The method of claim 9, wherein the detector further includes a source monitoring apparatus, wherein the method further comprises generating, with the source monitoring apparatus, output signals conveying information related to electrical resistance through the first source, and wherein the determination of the level of the gaseous molecular species is further based on the output signals generated by the source monitoring apparatus to account for the electrical resistance through the first source.

11. The method of claim 10, wherein determining the level of the gaseous molecular species based on the output signals generated by the source monitoring apparatus effectively adjusts the level determination for the irradiance of the first source.

12. The method of claim 9, wherein the second radiation sensor includes a photodiode.

13. The method of claim 9, wherein the second source includes at least one of a light emitting diode or a laser diode.

14. The method of claim 9, wherein:

the output signals conveying information related to a parameter of the mid-infrared electromagnetic radiation in the first radiation include output signals conveying information related to an intensity of the mid-infrared electromagnetic radiation in the first radiation;

the output signals conveying information related to a parameter of the near-infrared electromagnetic radiation in the second radiation include output signals conveying information related to an intensity of the near-infrared electromagnetic radiation in the second radiation; and

the level of the gaseous molecular species within the flow of breathable gas in the flow path is determined based on the output signals generated by the first radiation sensor and the second radiation sensor including normalizing the intensity of the mid-infrared electromagnetic radiation in the first radiation using the intensity of the near-infrared electromagnetic radiation in the second radiation to compensate optical loss through the flow path.

15. The method of claim 9, wherein the gaseous molecular species is carbon dioxide, nitrous oxide, or water vapor.

16. A detector configured to monitor a level of a gaseous molecular species within a flow of breathable gas, the system 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 directed across a flow path of the flow of breathable gas that communicates with an airway of a subject;

sensor optics configured to divide 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;

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 carbon dioxide 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.

17. The detector of claim 16, further comprising:

a source monitoring apparatus configured to generate output signals conveying information related to electrical resistance through the first source,

wherein the processor is further configured such that the determination of the level of carbon dioxide is further based on the output signals generated by the source monitoring apparatus to account for the electrical resistance through the first source.

18. The detector of claim 17, wherein determining the level of carbon dioxide based on the output signals generated by the source monitoring apparatus effectively adjusts the level determination for the irradiance of the first source.

19. The detector of claim 16, wherein the second radiation sensor includes a photodiode.

20. The detector of claim 16, wherein the second source includes at least one of a light emitting diode or a laser diode.