OXIMETER AND METHOD FOR IN VIVO DETERMINATION OF OXYGEN SATURATION IN BLOOD USING THREE OR MORE DIFFERENT WAVELENGTHS

• US 3,638,640 A
• Filed: 11/01/1967
• Issued: 02/01/1972
• Est. Priority Date: 11/01/1967
• Status: Expired due to Term

• Current Assignee: Robert F. Shaw
• Sponsoring Entity: Robert F. Shaw
• Inventors: Shaw, Robert F.
• Primary Examiner(s): Kamm, William E.
• Time in USPTO: 1553 Days
• Field of Search: 128/2,2.1,2.5D,2.5F,2.5M,2.5P,2.5PR 356/39-41,176-178,180,181,186,206
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14552 : Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/6815 : Ear
• CPC Class Codes: A61B 5/6838 : Clamps or clips
• CPC Class Codes: G01N 2021/3148 : using three or more wavelengths
• CPC Class Codes: G01N 21/314 : with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427

Abstract

Oximeter method and apparatus uses a test appliance that includes a source for directing radiation into skin tissue or other blood-confining container at three or more wavelengths and a detector for sensing the radiation intensity emanating from the skin tissue or other container at each wavelength. The oximeter method and apparatus also uses circuitry for combining the detector outputs in a predetermined manner to provide an indication of the oxygen saturation of the blood independently of position or movement of the test appliance on the patient and without first calibrating the indication on each patient.

Claims

1. Apparatus for determining the oxygen saturation of blood in the tissues of animal bodies in which variations occur in the optical measurement geometry and from which the blood cannot be removed for the purpose of making reference radiation intensity measurements, the apparatus comprising:

source means for producing electromagnetic radiation at at first, second and third radiation wavelengths and being disposed to supply incident radiation to the measurement site on the body at the plurality of wavelengths for producing output radiation from the body with intensities at the respective wavelengths that are altered from the incident intensities at such wavelengths by substantially the same conditions of the optical measurement geometry, the body and the blood present therein;

detector means for receiving said output radiation at each of said plurality of wavelengths for producing at least three electrical outputs which are representative only of the intensities of the output radiation at the respective wavelengths as altered from the corresponding incident intensities by the condItions of the optical measurement geometry, the body and the blood present therein at the measurement site; and

circuit means connected to the detector means to receive the electrical outputs produced thereby in response to said output radiation for simultaneously combining all of said electrical outputs to produce therefrom an indication of the oxygen saturation of the blood present in the body at the measurement site substantially independently of changes in the optical measurement geometry.

2. Apparatus as in claim 1 comprising:

radiant-energy diffusing means interposed between said source means and the body for providing radiation thereto diffused over a given area of irradiation; and

said detector means includes an aperture of area substantially smaller than said given area of diffused irradiation for receiving said output radiation therethrough from said body.

3. Apparatus as in claim 1 wherein:

said circuit means includes network means connected to receive said electrical outputs produced by said detector means for producing the logarithm of each of said electrical outputs and for linearly combining with selected weighting factors the logarithms of all of said electrical outputs to provide an output indicative of the oxygen saturation of blood in the body.

4. Apparatus as in claim 1 wherein variations occur in the concentration of a wavelength-dependent, radiation-absorbing substance present in the body tissue or the blood therein at the measurement site and wherein:

said source means of electromagnetic radiation provides radiation the body and blood contained therein at the measurement site at at least first, second, third and fourth radiation wavelengths; and

said detector means receives said output radiation at each of said plurality of wavelengths for producing at least four electrical outputs which are representative only of the intensities of the output radiation at the respective radiation wavelengths with the substance and the blood present at the measurement site.

5. Apparatus as in claim 4 comprising:

radiant-energy diffusing means interposed between said source means and the body for providing radiation thereto diffused over a given area of irradiation; and

said detector means includes an aperture of area substantially smaller than said given area of diffused irradiation for receiving said output radiation therethrough from said body.

6. Apparatus as in claim 4 wherein:

said circuit means includes network means connected to receive said electrical outputs produced by said detector means for producing the logarithm of each of said electrical outputs and for linearly combining with selected weighting factors the logarithms of all of said electrical outputs to provide an output indicative of the oxygen saturation of blood in the body.

7. Apparatus as in claim 4 wherein variations occur in the concentration of a wavelength-dependent, radiation-absorbing substance present in the tissue and also occur in the concentration of a wavelength-dependent, radiation-absorbing substance present in the blood within the body in addition to oxyhemoglobin and reduced hemoglobin and wherein:

said source means of electromagnetic radiation provides radiation to the body and blood contained therein at the measurement site at at least first, second, third, fourth and fifth radiation wavelengths; and

said detector means receives said output radiation at each of said plurality of wavelengths for producing at least five electrical outputs which are representative only of the intensities of the output radiation at the respective radiation wavelengths with the substances and the blood present at the measurement site.

8. Apparatus as in claim 7 comprising:

radiant-energy diffusing means interposed between said source means and the body at said measurement site for providing said incident radiation to the body diffused over a given area of irradiation; and

said detector means includes an aperture of areA substantially smaller than said given area of diffused irradiation for receiving said output radiation therethrough from said body.

9. Apparatus as in claim 7 wherein:

said circuit means includes network means connected to receive said electrical outputs produced by said detector means for producing the logarithm of each of said electrical outputs and for linearly combining with selected weighting factors the logarithms of all of said electrical outputs to provide an output indicative of the oxygen saturation of blood in the body.

10. Apparatus as in claim 1 wherein said detector means is positioned with respect to said source means for receiving the output radiation from said body substantially only in the mode of radiation transmission through the body and the blood therein.

11. Apparatus as in claim 1 wherein said detector means is positioned with respect to said source means for receiving said output radiation from said body substantially only in the mode of radiation scattering back from the body and the blood therein.

12. Apparatus as in claim 1 wherein said circuit means includes:

a first network connected to the detector means for receiving said electrical outputs for simultaneously combining all of said electrical outputs produced by said detector means for producing a first output indicative of the quantity of oxyhemoglobin present in the blood at the measurement site;

a second network connected to the detector means for receiving said electrical outputs for simultaneously combining all of said electrical outputs produced by said detector means for producing a second output indicative of the total quantity of oxyhemoglobin and reduced hemoglobin present in the blood at the measurement site; and

a third network connected to receive said first and second outputs for producing an output indication of oxygen saturation as the ratio of the first output to the second output.

13. Apparatus as in claim 12 wherein said detector means includes a gain-logarithmic amplifier for producing said electrical outputs, each indicative of the logarithm of the intensity of the output radiation received by the detector means at the respective one of the radiation wavelengths with blood present at the measurement site;

said first network includes means for linearly altering said electrical outputs by a first set of weighting factors and for simultaneously linearly combining all of the electrical outputs weighted by said first set of factors to produce said first output; and

said second network includes means for linearly altering said electrical outputs by a second set of weighting factors and for simultaneously linearly combining all of the electrical outputs weight by said second set of factors to produce said second output.

14. Apparatus as in claim 12 comprising:

radiant-energy diffusing means interposed between said source means and the body at said measurement site for providing said incident radiation to the body diffused over a given area of irradiation; and

said detector means includes an aperture of area substantially smaller than said given area of diffused irradiation for receiving said output radiation therethrough from said body.

15. Apparatus for determining the concentration of a selected wavelength-dependent, radiation-absorbing constituent present with other wavelength-dependent, radiation-absorbing constituents at measurement sites in animals bodies in which variations occur in the optical measurement geometry and from which such selected constituent cannot be excluded for the purpose of making reference radiation intensity measurements, the apparatus comprising:

source means for producing electromagnetic radiation at at least first, second and third radiation wavelengths and being disposed to supply incident radiation to the measurement site on the body at the plurality of wavelengths for producing output radiation from the body with intensities at the respective wavelengths that are altered from the Incident intensities at such wavelengths by substantially the same conditions of the optical measurement geometry, the body and the wavelength-dependent, radiation-absorbing constituents present therein;

detector means for receiving said output radiation at each of said plurality of wavelengths for producing at least three electrical outputs which are representative only of the intensities of the output radiation at the respective wavelengths as altered from the corresponding incident intensities by the conditions of the optical measurement geometry, the body and the wavelength-dependent, radiation-absorbing constituents present therein at the measurement site; and

circuit means connected to the detector means to receive the electrical outputs produced thereby in response to said output radiation for simultaneously combining all of said electrical outputs to produce therefrom an indication of the quantity of said selected constituent present in the body at the measurement site substantially independently of changes in the optical measurement geometry.

16. Apparatus as in claim 15 wherein:

said detector means is disposed with respect to said source means to receive said output radiation from the body substantially only in the mode of radiation transmission through the body.

17. Apparatus as in claim 15 wherein said detector means is positioned with respect to said source means for receiving said output radiation from the body substantially only in the mode of radiation scattered back from the body and the blood therein at the measurement site.

18. Apparatus as in claim 15 comprising:

radiant-energy diffusing means interposed between said source means and the body for providing said incident radiation to the body diffused over a given area of irradiation; and

said detector means includes an aperture of area substantially smaller than said given area of diffused irradiation for receiving said output radiation therethrough from said body.

19. Apparatus as in claim 15 wherein:

said circuit means includes network means connected to receive said electrical outputs produced by said detector means for producing the logarithm of each of said electrical outputs and for linearly combining with selected weighting factors the logarithms of all of said electrical outputs to provide an output indicative of the quantity of said selected constituent.

20. Apparatus as in claim 15 wherein variations occur in the concentration of an additional wavelength-dependent, radiation-absorbing substance present in the body tissue or the blood therein at the measurement site and wherein:

said source means of electromagnetic radiation provides to the body containing the selected constituent at the measurement site at at least first, second, third and fourth radiation wavelengths; and

said detector means receives said output radiation at each of said plurality of wavelengths for producing at least four electrical outputs which are representative only of the intensities of the output radiation at the respective radiation wavelengths in the presence of the substance at the measurement site.

21. Apparatus as in claim 20 comprising:

radiant-energy diffusing means interposed between said source means and the body for providing said incident radiation to the system diffused over a given area of irradiation; and

said detector means includes an aperture of area substantially smaller than said given area of diffused irradiation for receiving said output radiation therethrough from said body.

22. Apparatus as in claim 20 wherein:

said circuit means includes network means connected to receive said electrical outputs produced by said detector means for producing the logarithm of each of said electrical outputs and for linearly combining with selected weighting factors the logarithms of all of said electrical outputs to provide an output indicative of the quantity of said selected constituent.

23. Apparatus as in claim 15 wherein variaTions occur in the concentration of a wavelength-dependent, radiation-absorbing substance present in the tissue, and also occur in the concentration of a wavelength-dependent, radiation-absorbing substance present in the blood within the body in addition to oxyhemoglobin and reduced hemoglobin, and wherein:

said source means of electromagnetic radiation provides radiation to the body containing the selected constituent at the measurement site at at least first, second, third, fourth and fifth radiation wavelengths; and

said detector means receives said output radiation at each of said plurality of wavelengths for producing at least five electrical outputs which are representative only of the intensities of the output radiation at the respective radiation wavelengths in the presence of the tissue and blood substances at the measurement site.

24. Apparatus as in claim 23 comprising:

radiant-energy diffusing means interposed between said source means and the body at said measurement site for providing said incident radiation to the body diffused over a given area of irradiation; and

said detector means includes an aperture of area substantially smaller than given area of diffused irradiation for receiving said output radiation therethrough from said body.

25. Apparatus as in claim 23 wherein:

said circuit means includes network means connected to receive said electrical outputs produced by said detector means for producing the logarithm of each of said electrical outputs and for linearly combining with selected weighting factors the logarithms of all of said electrical outputs to provide an output indicative of the quantity of said selected constituent.

26. Apparatus for determining the concentration of a wavelength-dependent, radiation-absorbing substance present in a system in which the optical geometry of measurement varies from system to system or within a given system, and the concentration of other wavelength-dependent, radiation-absorbing substances may vary from system to system or within a given system, and the substance of interest is not removed from the system for purposes of reference radiation intensity measurements of the system in the absence of the substances of interest, the apparatus comprising:

source means of electromagnetic radiation for supplying incident radiation to the system including the substance of interest at a total number of selected radiation wavelengths equal to at least one plus the number of wavelength-dependent, radiation-absorbing substances including the substance of interest which vary in concentration in the system under test for producing output radiation emanating from the system with intensities at the respective wavelengths that are altered from the incident intensities at such wavelengths by substantially the same conditions of the optical measurement geometry and the substances present in the system under test;

detector means for receiving said output radiation at each of said radiation wavelengths for producing a corresponding number of electrical outputs which are representative only of the intensities of the output radiation at the respective wavelengths as altered from the corresponding incident intensities by the conditions of the optical measurement geometry and the substances present in the system under test; and

circuit means connected to the detector means to receive the electrical outputs produced thereby in response to said output radiation for simultaneously combining all of said electrical outputs to produce therefrom an indication of the concentration of said selected substance present in the system substantially independently of changes in the optical measurement geometry.

27. Apparatus as in claim 26 comprising:

radiant-energy diffusing means interposed between the source means and said system for providing said incident radiation to the system diffused over a given area of irradiation; and

said detector means includes an aperture of area substantially smaller Than said given area of diffused irradiation for receiving said output radiation therethrough from said system.

28. Apparatus as in claim 26 wherein:

said circuit means includes network means connected to receive said electrical outputs produced by said detector means for producing the logarithm of each of said electrical outputs and for linearly combining with selected weighting factors the logarithms of all of said electrical outputs to provide an output indicative of the concentration of said selected substance.

29. Apparatus as in claim 26 wherein:

said detector means is disposed with respect to said source means to receive the output radiation substantially only in the mode of radiation scattering back from said system.

30. Apparatus as in claim 26 wherein:

said detector means is positioned with respect to said source means for receiving the output radiation from the system under test substantially only in the mode of radiation transmission through the system.

31. Method of determining the concentration of a selected wavelength-dependent, radiation-absorbing constituent present with other wavelength-dependent, radiation-absorbing constituents in a multiconstituent system under test in which variations occur in the optical measurement geometry and from which the selected constituent is not excluded for the purpose of making reference radiation intensity measurements, the method comprising the steps of:

supplying incident electromagnetic radiation to the multiconstituent system at a total plural number of radiation wavelengths equal to at least one plus the number of wavelength-dependent, radiation-absorbing constituents which vary in concentration in the system under test for producing output radiation emanating from the system with intensities at the respective wavelengths that are altered from the incident intensities at such wavelengths by substantially the same conditions of the optical measurement geometry and the multiconstituent system;

producing a corresponding plural number of electrical outputs which are representative only of the intensities of the output radiation at the respective wavelengths as altered from the corresponding incident intensities by the conditions of the optical measurement geometry and the multiconstituent system under test; and

simultaneously combining all of said electrical outputs produced in response to said output radiation for producing therefrom an indication of the quantity of said selected constituent present in the multiconstituent system substantially independently of changes in the optical measurement geometry.

32. Method of continuously indicating oxygen saturation of blood in the tissues of animal bodies in which variations occur in the optical measurement geometry and from which the blood cannot be removed for the purpose of making reference radiation intensity measurements, the method comprising the steps of:

supplying incident electromagnetic radiation to a measurement site on the body at at least first, second and third radiation wavelengths for producing output radiation emanating from the body with intensities at the respective wavelengths that are altered from the incident intensities at such wavelengths by substantially the same conditions of the optical measurement geometry, the body and blood present therein;

producing at least three electrical outputs which are representative only of the intensities of the output radiation at the respective wavelengths as altered from the corresponding incident intensities by the conditions of the optical measurement geometry, the body and the blood present therein at the measurement site; and

simultaneously combining all of said electrical outputs produced in response to said output radiation for producing therefrom an indication of the oxygen saturation of the blood present in the body at the measurement site substantially independently of changes in the optical measurement geometry.

33. The method as in claim 32 wherein the step of combining the signals includes:

converting all the electrical outputs to logarithmic outputs;

forming a pair of indicator outputs, each as a selected simultaneous linear combination of all the logarithmic outputs; and

producing the indication of oxygen saturation at the measurement site as the ratio of the pair of indicator outputs.

34. Method as in claim 50 wherein the step of supplying incident electromagnetic radiation includes supplying the radiation to the body diffused over a given area of irradiation;

and in the step of producing said electrical outputs, the electrical outputs are formed in response only to the output radiation within an area substantially smaller than said given area of irradiation.

35. In the method as in claim 32 wherein variations occur in the concentration of wavelength-dependent, radiation-abosrbing substance present in the body tissue or the blood therein, the step of supplying incident electromagnetic radiation includes supplying such radiation at at least first, second, third and fourth radiation wavelengths for producing the output radiation emanating from the body with intensities at the respective wavelengths that are altered from the incident intensities at such wavelengths by substantially the same conditions of the optical measurement geometry, the body and the substance and blood present therein;

and the step of producing electrical outputs includes producing at least four electrical outputs which are representative only of the intensities of the output radiation at the respective wavelengths as altered from the corresponding incident intensities by the conditions of the optical measurement geometry, the body and the substance and blood present therein.

36. In the method of claim 32 wherein variations in the concentration of a wavelength-dependent, radiation-absorbing substance present in the body tissue and also occur in the concentration of a wavelength-dependent, radiation-absorbing substance present in the blood within the body in addition to oxyhemoglobin and reduced hemoglobin, the step of supplying incident electromagnetic radiation includes supplying such radiation at at least first, second, third, fourth and fifth radiation wavelengths for producing the output radiation emanating from the body with intensities at the respective wavelengths that are altered from the incident intensities at such wavelengths by substantially the same conditions of the optical measurement geometry, the body, blood and substances present therein;

and the stop of producing electrical outputs includes producing at least five electrical outputs which are representative only of the intensities of the output radiation at the respective wavelengths as altered from the corresponding incident intensities by the conditions of the optical measurement geometry, the body, blood and substances present therein.