Sample conditioning and environmental control techniques for gas sensor

• US 20050240115A1
• Filed: 02/07/2005
• Published: 10/27/2005
• Est. Priority Date: 07/23/2002
• Status: Active Grant

• Current Assignee: Aerocrine AB (Circassia Group Plc)
• Original Assignee: Aperon Biosystems Corp. (Circassia Group Plc)
• Inventors: Fay, Jonathan, Anvar, David, Parikh, Bhairavi, Hammerman, John, Stone, James, Nason, Kevin
• Granted Patent: US 7,352,465 B2
• Time in Patent Office: Days
• US Class Current: 600/532
• CPC Class Codes: A61B 5/097 Devices for facilitating collection of breath or for directing breath into or through measuring devices
• CPC Class Codes: G01N 2021/3545 Disposition for compensating effect of interfering gases
• CPC Class Codes: G01N 33/497 of gaseous biological material, e.g. breath

Abstract

The present invention is a system and method of conditioning the sample and surrounding environment of an exhaled breath sensor. It includes (i) using a particular molecular sieve for a triple purpose: (a) maintaining the sensor at a constant relative humidity during storage, (b) equilibrating the incoming breath stream to the same relative humidity as the sensor, and (c) eliminating the analyte from the environment around the sensor during storage. The present invention also includes removal of interfering components from the exhaled breath, such as carbon dioxide, as well as a thermal management technique.

Claims

1. A system for measuring a trace gas in exhaled breath, comprising:

a. a sensing element that is responsive to a trace gas analyte in exhaled breath; and

b. a desiccant, said desiccant placed at least partially upstream from said sensing element.

2. The system according to claim 1, wherein said desiccant is a molecular sieve.

3. The method according to claim 2, wherein said molecular sieve is size 3A.

4. The method according to claim 1, wherein said sensing element comprises cytochrome-c in a sol-gel.

5. The method according to claim 1, wherein said analyte is nitric oxide.

6. The method according to claim 1, additionally comprising a scrubber for removing an interfering substance.

7. The method according to claim 6, wherein said interfering substance is carbon dioxide.

8. The method according to claim 6, wherein said scrubber comprises activated alumina.

9. The system according to claim 1, wherein said desiccant surrounds said sensing element.

10. The system according to claim 1, additionally comprising a heater/cooler for controlling the temperature of said sensing element.

11. A method for measuring an analyte in exhaled breath, comprising:

a. providing a sensor, said sensor comprising a sensing element that is responsive to a trace gas in exhaled breath;

b. maintaining a predetermined sensor humidity level in said sensor during storage;

c. capturing an exhaled breath stream from a subject into said sensor, wherein said exhaled breath stream has a breath humidity level; and

d. conditioning said breath stream so that said breath humidity level is substantially equivalent to said predetermined sensor humidity level.

12. The method according to claim 11, wherein a molecular sieve is used in maintaining a predetermined sensor humidity level in said sensor during storage.

13. The method according to claim 11, wherein a molecular sieve is used in conditioning said breath stream so that said breath humidity level is substantially equivalent to said predetermined sensor humidity level.

14. The method according to claim 12, wherein said molecular sieve is used in conditioning said breath stream so that said breath humidity level is substantially equivalent to said predetermined sensor humidity level.

15. The method according to claim 11, additionally comprising removing said analyte from said sensor during storage.

16. The method according to claim 15, wherein a molecular sieve is used in removing said analyte from said sensor during storage.

17. The method according to claim 16, wherein said molecular sieve is used in maintaining a predetermined sensor humidity level in said sensor during storage.

18. The method according to claim 17, wherein said molecular sieve is used in conditioning said breath stream so that said breath humidity level is substantially equivalent to said predetermined sensor humidity level.

19. The method according to claim 11, wherein said analyte is nitric oxide.

20. The method according to claim 11, wherein said predetermined sensor humidity level is between 10 to 100 ppm.

21. The method according to claim 11, wherein said molecular sieve surrounds said sensing element.

22. The method according to claim 11, additionally comprising removing an interfering substance from said breath stream with a scrubber.

23. The method according to claim 22, wherein said interfering substance is carbon dioxide.

24. The method according to claim 23, wherein said scrubber comprises activated alumina.

25. A system for measuring a trace gas in exhaled breath, comprising:

a. a sensing element that is responsive to a trace gas analyte in exhaled breath; and

b. a temperature control device associated with said bioactive sensing element.

26. The system according to claim 25, wherein said temperature control device is a heater/cooler.

27. The system according to claim 26, wherein said heater/cooler maintains said exhaled breath and said sensing element at a predetermined temperature within 1.0°

C.

28. The system according to claim 27, wherein said heater maintains said gas stream and said sensing element at a predetermined temperature within 0.001°

C.

29. The system according to claim 28, wherein said predetermined temperature is approximately 20-40°

C.

30. The system according to claim 29, additionally comprising a molecular sieve at least partially upstream from said sensing element.

31. The system according to claim 30, additionally comprising a scrubber.

32. A system for measuring the concentration of an analyte in a gas, comprising

a. an exhaled breath sensor;

b. means for removing said analyte from an environment around said sensor;

c. means for substantially controlling relative humidity in said sensor;

d. means for conditioning the relative humidity in an exhaled breath sample so that said exhaled breath relative humidity is substantially equal to the relative humidity in said sensor;

e. means for removing an interferent from said exhaled breath sample; and

f. means for temperature controlling said sensor and said breath sample.