Apparatus for measuring a level of a specific gas in exhaled breath

• US 9,671,389 B2
• Filed: 10/29/2010
• Issued: 06/06/2017
• Est. Priority Date: 11/03/2009
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Van Kesteren, Hans Willem
• Primary Examiner(s): Natnithithadha, Navin
• Assistant Examiner(s): WEARE, MEREDITH H
• Application Number:
  US13/503,669
• Publication Number:
  US 20120271188A1
• Time in Patent Office: 2,412 Days
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• 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: G01H 5/00 Measuring propagation velocity of ultrasonic, sonic or infrasonic waves , e.g. of pressure waves
• CPC Class Codes: G01N 2021/1704 in gases
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: G01N 2291/0215 Mixtures of three or more gases, e.g. air
• CPC Class Codes: G01N 2291/02809 Concentration of a compound, e.g. measured by a surface mass change
• CPC Class Codes: G01N 29/024 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/2425 optoacoustic fluid cells therefor
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath

Abstract

There is provided an apparatus for measuring levels of a specified gas in exhaled breath, the apparatus comprising a photoacoustic sensor for providing a measurement representative of the level of the specified gas in the exhaled air, wherein the photoacoustic sensor comprises a light source that is modulated at a first frequency; a sound speed measurement module for measuring the sound speed of the exhaled breath, wherein the sound speed measurement module operates either at a second frequency that is substantially different to the first frequency or in a pulsed mode; wherein the first frequency of the modulated light source is adjusted during exhalation in accordance with the measured speed of sound of the exhaled breath.

Claims

1. An apparatus for measuring levels of a specified gas in breath exhaled by a subject, the apparatus comprising:

a photoacoustic sensor for providing a measurement representative of the level of the specified gas in the exhaled breath, wherein the photoacoustic sensor comprises a light source that is modulated at a first frequency; and

a sound speed measurement module for measuring the sound speed of the exhaled breath, wherein the sound speed measurement module operates either at a second frequency that is substantially different to the first frequency or in a pulsed mode;

wherein the sound speed measurement module comprises a second light source and a third light source which are anti-phase modulated; and

wherein the first frequency of the modulated light source is adjusted during exhalation in accordance with the measured speed of sound of the exhaled breath.

2. An apparatus as claimed in claim 1, wherein the photoacoustic sensor comprises a resonator chamber that is operated in a plane wave mode, and wherein the first frequency of the modulated light source is adjusted in accordance with the measured speed of sound of the exhaled breath and an acoustic mode of the resonator chamber.

3. An apparatus as claimed in claim 1, wherein the sound speed measurement module operates at the second frequency.

4. An apparatus as claimed in claim 1, wherein the sound speed measurement module comprises:

wherein the apparatus is configured to provide a measurement of the specified gas and exhalation flow.

5. An apparatus as claimed in claim 1, wherein sound speed measurement module comprises:

a temperature sensor for determining the temperature of the specified gas; and

a processor for determining the sound speed in the exhaled breath and a molar mass from at least the temperature; and

wherein the apparatus is configured to provide a measurement of the specified gas and the molar mass.

6. An apparatus as claimed in claim 1, wherein the specified gas is nitric oxide.

7. An apparatus as claimed in claim 6, wherein the apparatus further comprises a converter for converting nitric oxide in the exhaled breath to nitrogen dioxide to provide a measurement sample, and wherein the photoacoustic sensor measures the levels of nitrogen dioxide in the measurement sample, the measured levels of nitrogen dioxide corresponding to the levels of nitric oxide in the exhaled breath.

8. An apparatus as claimed in claim 6, wherein the apparatus further comprises a processing unit for determining one or more parameters describing nitric oxide production in the subject'"'"'s airways based on the exhaled nitric oxide and flow patterns during one or more exhalations.

9. An apparatus as claimed in claim 6, wherein the apparatus further comprises a processing unit for determining one or more parameters describing nitric oxide production in the subject'"'"'s airways based on the exhaled nitric oxide, flow and molar mass patterns during one or more exhalations.

10. A method of measuring levels of a specified gas in exhaled breath using a photoacoustic sensor comprising a first light source modulated at a first frequency, and a sound speed measurement module comprising a second light source and a third light source which are anti-phase modulated, the method comprising:

measuring the speed of sound of the exhaled breath, with the sound speed measurement module;

adjusting the first frequency during exhalation in accordance with the speed of sound of the exhaled breath; and

using the photoacoustic sensor to provide a measurement representative of the level of the specified gas in the exhaled breath;

wherein the speed of sound is measured either at a second frequency that is substantially different to the first frequency or in a pulsed mode.

11. A method as claimed in claim 10, wherein the photoacoustic sensor provides a measurement representative of the level of the specified gas in the exhaled breath by:

passing light from the first light source through a measurement sample of the exhaled breath that is contained in a resonance chamber of the photoacoustic sensor, the light from the first light source having a wavelength in the absorption range of the specified gas; and

measuring the sound generated from the laser beam passing through the measurement sample of the exhaled breath to provide the measurement representative of the specified gas in the exhaled breath.

12. A method as claimed in claim 10, wherein the specified gas is nitric oxide and wherein the method further comprises the step of:

passing a sample of the exhaled breath through a nitric oxide to nitrogen dioxide converter to generate a measurement sample;

wherein the photoacoustic sensor measures the level of nitrogen dioxide in the measurement sample to provide the measurement representative of the level of nitric oxide in the exhaled breath.