Apparatus and method for respiratory monitoring

• US 5,800,360 A
• Filed: 06/07/1995
• Issued: 09/01/1998
• Est. Priority Date: 02/11/1992
• Status: Expired due to Term

• Current Assignee: Spectrum Medical Technologies, Inc.
• Original Assignee: Spectrum Medical Technologies, Inc.
• Inventors: Baker, Steven P., Muskin, R. Bennett, Kisner, Roger A.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US08/474,457
• Time in Patent Office: 1,182 Days
• Field of Search: 128/719, 128/920, 600/532
• US Class Current: 600/532
• CPC Class Codes: G08B 13/19 using infrared-radiation detection systems G08B13/194 takes precedence

Abstract

A passive, non-invasive, non-contacting apparatus and method for monitoring the respiration of a subject within a monitored environment is disclosed. The apparatus generally comprises a pair of sensors which detect changes in infrared energy. The first sensor detects changes in infrared energy which signifies and corresponds to changes in the monitored environments of a component to be monitored and generates a first signal. The second sensor detects changes in infrared energy which signifies reference infrared energy in the monitored environment and generates a second signal. A processing system converts the first and second signals into a third signal which signifies the concentration of the monitored component in the monitored environment. The monitored components may be CO₂ H₂ O or a constituent of exhaled breath such as a ketone, amino acid, insulin or pintane. In another embodiment of the invention changes in blood pH may be monitored by adding an additional sensor. Micromotion of the subject'"'"'s body may also be monitored in yet another embodiment through the use of a single sensor together with an appropriate processing system. Imaging techniques may be employed to accomplish high resolution monitoring of the monitored environment.

Claims

1. A non-invasive, non-contacting apparatus having imaging optics for determining changes in amounts of a respiratory component present in a predetermined spatial volume intermediate said apparatus and a surface of size determined by the imaged field of view of said optics by detection of infrared energy emitted by said surface or present in said volume and transiting said volume to said apparatus, the apparatus comprising:

first sensor means having a plurality of first sensor elements disposed a distance from said surface substantially equivalent to the object length of said optics for sensing infrared energy emitted by said surface or present in said volume and transiting at least a part of said volume to said first sensor means, for imaging the spatial intensity distribution of infrared energy emitted by said surface or present in said volume and transiting at least a part of said volume to said first sensor means, producing a first image having a plurality of pixels in two-dimensional alignment, wherein at least one of said first sensor elements produces a first signal which indicates the presence or absence of radiation in a first range of wavelengths incident on the elements, said first range of wavelengths including wavelengths to which a respiratory gas of interest is responsive;

second sensor means having a plurality of second sensor elements disposed a distance from said surface substantially equivalent to the object length of said optics for sensing infrared energy emitted by said surface or present in said volume and transiting at least a part of said volume to said second sensor means at substantially the same time as the infrared energy sensed by said first sensor means, for imaging the spatial intensity distribution of infrared energy emitted by said surface or present in said volume and transiting at least a part of said volume to said second sensor means producing a second image having a plurality of pixels in two-dimensional alignment, wherein said second sensor elements produce a second signal which indicates the presence or absence of radiation in a second range of wavelengths incident on the elements which is substantially nonoverlapping with said first range of wavelengths;

wherein said first and second images substantially temporally and spatially overlap; and

processing means for processing said first and second images to produce a third image having a plurality of pixels in two-dimensional alignment representing a change in the amount of a respiratory component in said volume, said processing means further comprising means for compensating said first matrix of signals by said second matrix of signals so as to reduce effects on said third matrix of signals of changes in the infrared emissions of said surface or present in said volume.

2. The apparatus as described in claim 1, wherein said respiratory component is CO₂ and said first range of wavelengths comprises wavelengths at which CO₂ is absorptive.

3. The apparatus as described in claim 1, wherein said respiratory component is H₂ O and said first range of wavelengths comprises wavelengths at which H₂ O is absorptive.

4. The apparatus as described in claim 1, wherein said respiratory component is a gas selected from the group consisting of a ketone, amino acid, insulin, and pintane, and said first range of wavelengths comprises wavelengths at which said selected gas is absorptive.

5. The apparatus as described in claim 1, further comprising optical means for restricting infrared energy impinging on said first and second sensor elements to infrared energy emitted by said surface or present in said volume.

6. The apparatus as described in claim 5, wherein said optical means comprise an aperture.

7. The apparatus as described in claim 5, wherein said optical means comprise a lens.

8. The apparatus as described in claim 5, wherein said optical means comprise a mirror.

9. The apparatus as described in claim 1, wherein said first or second sensor means comprise a bandpass filter.

10. The apparatus as described in claim 1, wherein said first or second sensor means comprise a bandstop filter.

11. The apparatus as described in claim 1, wherein said processing means comprise means for producing said third image as a function of the difference between said first and second images.

12. The apparatus as described in claim 1, wherein said processing means further comprise means for producing said third image by means of applying non-linear mathematical functions to said first or second images.

13. The apparatus as described in claim 1, wherein said processing means further comprise means for providing said third image by means of an artificial neural network or fuzzy logic system.

14. A passive, non-invasive, non-contacting apparatus for monitoring the respiration of a subject in a monitored environment, the apparatus comprising:

first sensor means for detecting changes in infrared energy signifying and corresponding to changes in concentration in said monitored environment of a respiration component to be monitored, said first sensor means comprising a plurality of first sensor elements, each of said first sensor elements first sensors having an instantaneous field of view comprising at least a portion of the monitored environment, a first optical filter for receiving and filtering said infrared energy to produce first filtered infrared energy comprised of a first range of infrared wavelengths that includes wavelengths of infrared energy absorbed by the respiration component to be monitored, and means for producing a first plurality of signals arranged two-dimensionally from said first sensor elements corresponding to the first filtered infrared energy passed by said first optical filter;

second sensor means for detecting changes in infrared energy signifying reference infrared energy in said monitored environment, said second sensor means comprising a plurality of second sensor elements, each of said second sensor elements having an instantaneous field of view comprising at least a portion of the monitored environment, a second optical filter for receiving and filtering said infrared energy to produce second filtered infrared energy comprised of a second range of infrared wavelengths that includes wavelengths of infrared energy different from wavelengths comprising said first selected range of infrared wavelengths, and means for producing a second plurality of signals arranged two-dimensionally from said second sensor elements corresponding to the second filtered infrared energy passed by said second optical filter;

means for directing infrared energy received from the monitored environment onto said first and second sensor means; and

means for processing signals in the first and second pluralities of signals to produce one or more signals corresponding to changes in concentration of said monitored component within the monitored environment.

15. The apparatus as described in claim 14, wherein said means for directing comprises at least one reflector for receiving and reflecting infrared energy from the monitored environment, and at least one optical lens for receiving and directing the reflected infrared energy onto said first and second sensor means.

16. The apparatus as described in claim 15, wherein said at least one reflector comprises at least one moving reflector of infrared energy.

17. The apparatus as described in claim 14, further comprising means for scanning the instantaneous fields of view of said first and second elements to produce the first and second pluralities of signals.

18. The apparatus as described in claim 14, wherein said respiratory component is CO₂, and wherein each of said one or more first sensors comprises a lead-selenium element sensitive to infrared energy of wavelengths approximating 3.9 microns, and each of said one or more second sensors comprises a lead-selenium element sensitive to infrared energy of wavelengths approximating 4.28 microns.

19. The apparatus as described in claim 14, further comprising means for imaging said first and second pluralities of signals to produce first and second images of the monitored environment.

20. The apparatus as described in claim 19, wherein said first and second images substantially temporally and spatially overlap.

21. The apparatus as described in claim 14, wherein said first sensor elements comprise a plurality of first sensors arranged into a first one-dimensional matrix of sensors, and said second sensor elements comprise a plurality of second sensors arranged into a second one-dimensional matrix of sensors.

22. The apparatus as described in claim 21, further comprising means for scanning said first and second one-dimensional matrices of sensors to produce the first and second matrices of signals.

23. The apparatus as described in claim 14, wherein said first sensor elements comprise a plurality of first sensor elements arranged into a first two-dimensional matrix of sensors having a first composite field of view of the monitored environment equal to the sum of the instantaneous fields of view of each of the first sensor elements, and said second sensor elements comprise a plurality of second sensor elements arranged into a second two-dimensional matrix of sensors having a second composite field of view of the monitored environment equal to the sum of the instantaneous fields of each of the second sensor elements.

24. The apparatus as described in claim 23, wherein said means for directing is further operable to scan the first and second composite fields of view of said first and second two-dimensional matrices of sensors to produce the first and second pluralities of signals.

25. The apparatus as described in claim 24, wherein said means for directing comprises at least one reflector for receiving and reflecting infrared energy from the monitored environment, and at least one optical lens for receiving and directing the reflected infrared energy onto said first and second sensor means.

26. The apparatus as described in claim 25, wherein said first and second two-dimensional matrices of sensors are positioned to receive reflected infrared energy from each portion of the monitored environment at different times, said apparatus further comprising means for substantially temporally aligning said first and second composite fields of view.

27. The apparatus as described in claim 14, further comprising means for cooling said first and second sensor elements to increase their sensitivity.

28. The apparatus as described in claim 14, further comprising means for chopping said infrared energy to increase the sensitivity of said first and second sensor elements.

29. The apparatus as described in claim 14, wherein said means for processing further comprise means for producing an alarm when a threshold change in the concentration of said monitored component in the monitored environment is detected.

30. A passive, non-invasive, non-contacting apparatus for monitoring the respiration of a subject having a system of organs subserving a respiration function producing CO₂ in a monitored environment, said apparatus comprising:

first sensor means in operative communication with said monitored environment, said first sensor means detecting changes in infrared energy signifying and corresponding to changes in the concentration of CO₂ in said monitored environment, said first sensor means generating a first plurality of signals arranged two-dimensionally to form a first image;

second sensor means in operative communication with said monitored environment, said second sensor means detecting changes in infrared energy signifying reference infrared energy in said monitored environment, said second sensor means generating a second plurality of signals arranged two-dimensionally to form a second image; and

a processing system which converts said first and second images into a third image, said third image signifying the concentration of CO₂ in the monitored environment.

31. The apparatus as described in claim 30, wherein said processing system further comprises a filter associated with one of said sensor means which filters from said second signal a component attributable to motion in the monitored environment.

32. The apparatus as described in claim 30, wherein said second sensor means detects changes in infrared energy in a detection range both within and outside the detection range of said first sensor means.

33. The apparatus as described in claim 30, wherein said second sensor means detects changes in infrared energy in a detection range only outside the detection range of said first sensor means.

34. The apparatus as described in claim 30, wherein said first sensor means detects changes in infrared energy in a detection range both within and outside the detection range of said second sensor means.

35. A passive, non-invasive, non-contacting method for monitoring the respiration of a subject having a system of organs subserving a respiration function producing CO₂ in a monitored environment, said method comprising the steps of:

detecting changes in signal infrared energy comprising a first range of wavelengths, said changes in signal infrared energy corresponding to changes in the concentration of CO₂ in said monitored environment;

generating a first plurality of signals in two-dimensional alignment from detected changes in signal infrared energy;

detecting changes in reference infrared energy comprising a second range of wavelengths which are substantially nonoverlapping with said first range of wavelengths;

generating a second plurality of signals in two-dimensional alignment from detected changes in reference infrared energy;

converting said first and second pluralities of signals into a third plurality of signals in two-dimensional alignment representing the concentration of CO₂ present in the monitored environment;

detecting changes in infrared energy in the monitored environment in the absorption wavelength of H₂ O; and

generating a fourth plurality of signals in two-dimensional alignment signifying and corresponding to changes in the concentration in the monitored environment of H₂ O vapor.

36. A passive, non-invasive, non-contacting apparatus for monitoring respiration of a subject having a system of organs subserving a respiration function producing CO₂ in a monitored environment to provide a concentration of CO₂ in the monitored environment, said apparatus comprising:

a first sensor in operative communication with said monitored environment, said first sensor detecting changes in infrared energy which transits said monitored environment, said changes in infrared energy signifying and corresponding to changes in the CO₂ concentration in said monitored environment, said first sensor producing a first signal;

a second sensor in operative communication with said monitored environment, said second sensor detecting changes in infrared energy which transits substantially the same monitored environment as infrared energy detected by said first sensor, said changes in infrared energy signifying reference infrared energy in said monitored environment, said second sensor producing a second signal; and

a processing system which converts said first and second signals into a third signal, said third signal signifying the concentration of CO₂ in the monitored environment.

37. Apparatus in accordance with claim 36, wherein said processing system further comprises a filter associated with one of said sensors which filters from said second signal a component attributable to motion in the detection region.

38. A passive, non-invasive, non-contacting apparatus for monitoring respiration of a subject having a system of organs subserving a respiration function producing CO₂ in a monitored environment to provide a concentration of CO₂ in the monitored environment, said apparatus comprising:

a first sensor in operative communication with said monitored environment, said first sensor detecting changes in infrared energy signifying and corresponding to changes in the concentration in said monitored environment of a component to be monitored, said first sensor generating a first signal;

wherein said first sensor detects changes in infrared energy in a first detection range within the monitored environment;

a second sensor in operative communication with said monitored environment, said second sensor detecting changes in infrared energy signifying reference infrared energy in said monitored environment, said second sensor generating a second signal,

wherein said second sensor detects changes in infrared energy in a second detection range that is both within and outside the first detection range of said first sensor; and

a processing system which converts said first and second signals into a third signal, said third signal signifying the concentration of the monitored component in the monitored environment.

39. A passive, non-invasive, non-contacting apparatus for monitoring respiration of a subject having a system of organs subserving a respiration function, said apparatus comprising:

a first sensor in operative communication with said monitored environment, said first sensor detecting changes in infrared energy signifying and corresponding to changes in the concentration in said monitored environment of a component to be monitored, said first sensor generating a first signal;

wherein said first sensor detects changes in infrared energy in a first detection range within the monitored environment;

a second sensor in operative communication with said monitored environment, said second sensor detecting changes in infrared energy within a second detection range signifying reference infrared energy in said monitored environment, said second sensor generating a second signal,

wherein said first sensor detects changes in infrared energy in a first detection range that is both within and outside the second detection range of said second sensor; and

a processing system which converts said first and second signals into a third signal, said third signal signifying the concentration of the monitored component in the monitored environment.

40. A passive, non-contacting, non-invasive method for monitoring respiration of a subject having a system of organs subserving a respiration function producing CO₂ in a monitored environment to provide a concentration of CO₂ in the monitored environment, said method comprising the steps of:

detecting changes in infrared energy wherein said changes signify and correspond to changes in the concentration in said monitored environment of CO₂ ;

generating a first signal from said changes in infrared energy of CO₂ in the monitored environment;

detecting changes in infrared energy signifying reference infrared energy in said monitored environment;

generating a second signal from said changes in the reference infrared energy;

converting said first and second signals into a third signal signifying the concentration of CO₂ in the monitored environment;

detecting changes in infrared energy in the monitored environment in the absorption wavelength of H₂ O; and

generating a fourth signal signifying and corresponding to changes in the concentration in the monitored environment of H₂ O vapor.

41. The method of claim 40, further comprising the steps of deriving a ratio of said third and fourth signals signifying and corresponding to changes in blood pH of the subject in the monitored environment.

42. A passive, non-invasive, non-contacting method for monitoring the respiration of a subject having a system of organs subserving a respiration function producing CO₂ in a monitored environment, said method comprising the steps of:

detecting changes in signal infrared energy comprising a first range of wavelengths, said changes in signal infrared energy corresponding to changes in the concentration of CO₂ in said monitored environment;

generating a first plurality of signals in two-dimensional alignment from detected changes in signal infrared energy;

detecting changes in reference infrared energy comprising a second range of wavelengths which are substantially nonoverlapping with said first range of wavelengths;

generating a second plurality of signals in two-dimensional alignment from detected changes in reference infrared energy; and

converting said first and second pluralities of signals into a third plurality of signals in two-dimensional alignment representing the concentration of CO₂ present in the monitored environment.

43. A passive, non-invasive, non-contacting method for monitoring the respiration of a subject having a system of organs subserving a respiration function producing a respiratory component in a monitored environment, said method comprising the steps of:

detecting changes in signal infrared energy comprising a first range of wavelengths, said changes in signal infrared energy corresponding to changes in the concentration of a respiratory component in said monitored environment;

generating a first plurality of signals in two-dimensional alignment from detected changes in signal infrared energy;

detecting changes in reference infrared energy comprising a second range of wavelengths which are substantially nonoverlapping with said first range of wavelengths;

generating a second plurality of signals in two-dimensional alignment from detected changes in reference infrared energy; and

converting said first and second pluralities of signals into a third plurality of signals in two-dimensional alignment representing the concentration of the respiratory component present in the monitored environment.