Catheter oximeter apparatus and method

• US 4,114,604 A
• Filed: 10/18/1976
• Issued: 09/19/1978
• Est. Priority Date: 10/18/1976
• Status: Expired due to Term

• Current Assignee: Robert F. Shaw, SPJohn M. Sperinde
• Original Assignee: Robert F. Shaw, SPJohn M. Sperinde
• Inventors: Shaw, Robert F., Sperinde, John M.
• Primary Examiner(s): Michell, Robert W.
• Assistant Examiner(s): Jaworski, Francis J.
• Application Number:
  US05/733,278
• Time in Patent Office: 701 Days
• Field of Search: 128/2 L, 128/2.05 F, 356/40, 356/41
• US Class Current: 600/339
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence

Abstract

An improved catheter oximeter operates on radiation at three or more different wavelengths applied to and scattered back from blood under test to provide an indication of oxygen saturation and is considerably less sensitive to accuracy-degrading variations in the blood and its environment and in the oximeter measuring system.

Claims

1. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at first, second and third radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a first output representative of the ratio of a first pair of the signals from said detector means, and for producing a second output representative of the ratio of a second pair of the signals from said detector means, the wavelengths of the radiation from said source means being such that the first ratio is independent of physiological changes of the sample blood other than oxygen saturation at a first oxygen saturation level and the second ratio is independent of physiological changes other than oxygen saturation at a second oxygen saturation level; and

first means coupled to the circuit means for receiving the first and second outputs of said circuit means and applying selected coefficients thereto to minimize the effect of varying physiological characteristics of the blood under test other than oxygen saturation, said first means producing an output representative of the algebraic combination of selectively weighted first and second outputs of said circuit means; and

second means coupled to the circuit means for receiving the first and second outputs of said circuit means and applying selected coefficients thereto to minimize the effect of varying physiological characteristics of the blood under test other than oxygen saturation, said second means producing an output representative of the algebraic combination of selectively weighted first and second outputs of said circuit means; and

means coupled to the first and second means for receiving the outputs therefrom and producing an output manifestation of the ratio of the outputs from the first and second means.

2. Apparatus as in claim 1 wherein said first and second means produce said outputs representing the polynomials A₀ + A₁ (I₁ /I₂) + A₂ (I₃ /I₂) and B₀ + B₁ (I₁ /I₂) + B₂ (I₃ /I₂) respectively where A and B coefficients are selectively weighted.

3. Apparatus as in claim 1 wherein the first wavelength is approximately 670 nanometers, the second wavelength is approximately 700 nanometers and the third wavelength is approximately 800 nanometers.

4. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at first, second and third radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a first output representative of the ratio of a first pair of the signals from said detector means, and for producing a second output representative of the ratio of a second pair of the signals from said detector means; and

first means coupled to the circuit means for producing an output representative of the algebraic combination of selectively weighted first and second outputs and square of one of the first and second outputs;

second means coupled to the circuit means for producing an output representative of the algebraic combination of selectively weighted first and second outputs and square of one of said first and second outputs; and

means coupled to the first and second means and responsive to said outputs therefrom for producing an output manifestation of the ratio of said outputs.

5. Apparatus as in claim 4 wherein said first and second means produce said outputs representative additionally of algebraic combinations with selectively weighted reference outputs.

6. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at a plurality of radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a plurality of outputs each representative of the ratio of a respective pair of the signals from said detector means;

first means coupled to the circuit means for producing corresponding resultant signals from at least one output multiplied in value by an output a selected number of times and for producing an output representative of the sum of all selectively weighted resultant signals; and

means coupled to the first means and responsive to said output therefrom for producing an output manifestation of oxygen saturation.

7. Apparatus as in claiam 6 wherein the output of said first means its representative additionally of algebraic combinations with selectively weighted reference outputs.

8. A method of determining oxygen saturation of blood comprising the steps of:

producing electro-magnetic radiation at three different wavebands;

coupling the radiation at each of the wavebands to blood under test;

detecting radiation at each of the wavebands received back from blood under test for producing a corresponding electrical signal representative of the intensity of the radiation received back from the blood under test at the respective waveband;

producing a first output representative of the ratio of one pair of electrical signals;

producing a second output representative of the ratio of another pair of said electrical signals;

producing third and fourth outputs representative of the algebraic combination of selectively weighted first and second outputs; and

producing an output manifestation of oxygen saturation as the ratio of said third output and said fourth output.

9. A method of determining oxygen saturation of blood comprising the steps of:

producing electro-magnetic radiation at three different wavebands;

coupling the radiation at each of the wavebands to blood under test;

detecting radiation at each of the wavebands received back from blood under test for producing a corresponding electrical signed representative of the intensity of the radiation received back from the blood under test at the respective waveband;

producing a first output representative of the ratio of one pair of said electrical signals;

producing a second output representative of the ratio of another pair of said electrical signals;

producing a third output representative of the algebraic combination of selectively weighted first output and second output and square of one of the first and second outputs;

producing a fourth output representative of the algebraic combination of selectively weighted first output and second output and square of one of the first and second outputs; and

producing an output manifestation of oxygen saturation as the ratio of said third output and said fourth output.

10. A method of determining oxygen saturation of blood comprising the steps of:

producing electro-magnetic radiation at a plurality of different radiation wavelengths;

coupling the radiation at each of the respective wavelengths to the blood under test;

detecting the radiation at each of the wavelengths received back from the blood under test for producing signals representative of the intensities of the radiation received back from the blood under test at the respective wavelengths;

producing a plurality of outputs each representative of the ratio of a respective pair of said signals;

producing corresponding resultant signals from each output multiplied in value by an output a selected number of times;

producing an output representative of the sum of all selectively weighted resultant signals; and

producing an output manifestation of oxygen saturation as the ratio of selected sums of resultant signals.

11. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at first, second and third radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a first output representative of the ratio of a first pair of the signals from said detector means, and for producing a second output representative of the ratio of a second pair of the signals from said detector means;

first means coupled to the circuit means for receiving the outputs therefrom and for weighting said outputs by applying coefficients thereto, wherein the algebraic sum of said coefficients substantially equals zero, to produce an output representative of the algebraic combination of selectively weighted first and second outputs from said circuit means; and

second means coupled to the circuit means for receiving the outputs therefrom and for weighting said outputs by applying coefficients thereto, wherein the algebraic sum of said coefficients substantially equals zero, to produce an output representative of the algebraic combination of selectively weighted first and second outputs from said circuit means; and

means coupled to the first and second means and responsive to said outputs therefrom for producing an output manifestation of the ratio of said outputs.

12. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at first, second and third radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a first output representative of the ratio of a first pair of the signals from said detector means, and for producing a second output representative of the ratio of a second pair of the signals from said detector means;

first means coupled to the circuit means for receiving the outputs therefrom and for weighting said outputs by applying coefficients thereto, wherein the algebraic sum of said coefficients substantially equals zero, to produce an output representative of the algebraic combination of selectively weighted first and second outputs and square of one of said first and second outputs from said circuit means;

second means coupled to the circuit means for receiving the outputs therefrom and for weighting said outputs by applying coefficients thereto, wherein the algebraic sum of said coefficients substantially equals zero, to produce an output representative of the algebraic combination of selectively weighted first and second outputs and square of one of said first and second outputs from said circuit means; and

means coupled to the first and second means and responsive to said outputs therefrom for producing an output manifestation of the ratio of said outputs.

13. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at a plurality of radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a plurality of outputs each respective of the ratio of a respective pair of the signals from said detector means;

first means coupled to the circuit means for receiving the outputs therefrom, raising at least some of said outputs to selected powers of said outputs, and for weighting said outputs by applying coefficients thereto, wherein the algebraic sum of said coefficients substantially equals zero, to produce an output representative of the algebraic combination thereof;

second means coupled to the circuit means for receiving the outputs therefrom, raising at least some of said outputs to selected powers of said outputs, and for weighting said outputs by applying coefficients thereto, wherein the algebraic sum of said coefficients substantially equals zero, to produce an output representative of the algebraic combination thereof; and

means coupled to the first and second means and responsive to said outputs therefrom for producing an output manifestation of the ratio of said outputs.

14. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at first, second and third radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a first output representative of the ratio of a first pair of the signals from said detector means, and for producing a second output representative of the ratio of a second pair of the signals from said detector means; and

first means coupled to the circuit means for producing an output representative of the algebraic combination of selectively weighted first and second outputs;

second means coupled to the circuit means for producing an output representative of the algebraic combination of selectively weighted first and second outputs;

output means coupled to the first and second means and responsive to said outputs therefrom for producing an output manifestation of the ratio of said outputs of the first and second means; and

the outputs of said circuit means being selectively weighted by amplifier gain and circuit component values of said first and second means to cause the partial derivative of said output manifestation of said output means with respect to the first output of said circuit means to be approximately zero near one extreme of the range of oxygen saturation to be measured, and to cause the partial derivative of the output manifestation of said output means with respect to the second output of said circuit means to be approximately zero near the other extreme of the range of values of oxygen saturation to be measured.

15. Apparatus for determining oxygen saturation of blood comprising:

source means producing electro-magnetic radiation at first, second and third radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a first output representative of the ratio of a first pair of the signals from said detector means, and for producing a second output representative of the ratio of a second pair of the signals from said detector means;

the first, second and third wavelengths of the source means having values to cause the cumulative dependence of the ratio of resultant signals of a first pair of wavelengths as represented by the first output of said circuit means upon variations in physiologic parameters other than oxygen saturation to be minimized near one extreme of the range of values of oxygen saturation to be measured and to cause the cumulative dependence of the ratio of resultant signals at a second pair of wavelengths as representated by the second output of said circuit means upon variations in physiologic parameters other than oxygen saturation to be minimized near the other extreme of the range of values of oxygen saturation to be measured;

first means coupled to the circuit means for producing an output representative of the algebraic combination of selectively weighted first and second outputs;

second means coupled to the circuit means for producing an output representative of the algebraic combination of selectively weighted first and second outputs; and

means coupled to the first and second means and responsive to said outputs therefrom for producing an output manifestation of the ratio of said outputs.

16. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at first, second and third radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detecor means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a first output representative of the ratio of a first pair of the signals from said detector means, and for producing a second output representative of the ratio of a second pair of the signals from said detector means; and

first means coupled to the circuit means for producing an output representative of the algebraic combination of selectively weighted first and second outputs and square of one of the first and second outputs;

second means coupled to the circuit means for producing an output representative of the algebraic combination of selectively weighted first and second outputs and square of one of said first and second outputs;

means coupled to the first and second means and responsive to said outputs therefrom for producing an output manifestation of the ratio of said outputs; and

the outputs of said circuit means being selectively weighted by amplifier gain and circuit component values of said first and second means to cause the partial derivative of said output manifestation of said output means with respect to the first output of said circuit means to be approximately zero near one extreme of the range of oxygen saturation to be measured, and to cause the partial derivative of the output manifestation of said output means with respect to the second output of said circuit means to be approximately zero near the other extreme of the range of values of oxygen saturation to be measured.

17. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at first, second and third radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a first output representative of the ratio of a first pair of the signals from said detector means, and for producing a second output representative of the ratio of a second pair of the signals from said detector means;

the first, second and third wavelengths of the souce means having values to cause the cumulative dependence of the ratio of resultant signals of a first pair of wavelengths as represented by the first output of said circuit means upon variations in physiologic parameters other than oxygen saturation to be minimized near one extreme of the range of values of oxygen saturation to be measured and to cause the cumulative dependence of the ratio of resultant signals at a second pair of wavelengths as represented by the second output of said circuit means upon variations in physiologic parameters other than oxygen saturation to be minimized near the other extreme of the range of values of oxygen saturation to be measured;

first means coupled to the circuit means for producing an output representative of the algebraic combination of selectively weighted first and second outputs and square of one of the first and second outputs;

second means coupled to the circuit means for producing an output representative of the algebraic combination of selectively weighted first and second outputs and square of one of said first and second outputs; and

means coupled to the first and second means and responsive to said outputs therefrom for producing an output manifestation of the ratio of said outputs.

18. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at a plurality of radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities and the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a plurality of outputs each representative of the ratio of a respective pair of the signals from said detector means;

first means coupled to the circuit means for producing corresponding resultant signals from at least one output multiplied in value by an output a selected number of times and for producing an output representative of the sum of all selectively weighted resultant signals; and

second means coupled to the circuit means for producing corresponding resultant signals for at least one output multiplied in value by an output a selected number of times and for producing an output representative of the sum of all selectively weighted resultant signals;

means coupled to the first and second means and responsive to said outputs therefrom for producing an output manifestation of the ratio of said outputs; and

the outputs of said circuit means being selectively weighted by amplifier gain and circuit component values of said first and second means to cause the partial derivative of said output manifestation of said output means with respect to the first output of said circuit means to be approximately zero near one extreme of the range of oxygen saturation to be measured, and to cause the partial derivative of the output manifestation of said output means with respect to the second output of said circuit means to be approximately zero near the other extreme of the range of values of oxygen saturation to be measured.

19. Apparatus for determining oxygen saturation of blood comprising:

source means for producing electro-magnetic radiation at a plurality of radiation wavelengths;

means coupled to the source means for supplying the radiation therefrom to blood under test with incident intensities at the respective wavelengths;

detector means disposed to receive radiation from the blood under test altered from the incident intensities of the respective wavelengths by the optical properties of the blood under test for producing signals representative of the intensities of the radiation received thereby at the respective wavelengths;

circuit means coupled to the detector means for producing a plurality of outputs each representative of the ratio of a respective pair of the signals from said detector means;

the radiation wavelengths of said source means being selected to cause the cumulative dependence of the ratios of resultant signals of respective pairs of wavelengths, represented by respective outputs of said circuit means, upon variations in physiologic parameters other than oxygen saturation to be minimized near respective different values in the range of values of oxygen saturation to be measured;

first means coupled to the circuit means for producing corresponding resultant signals from at least one output multiplied in value by an output a selected number of times and for producing an output representative of the sum of all selectively weighted resultant signals; and

means coupled to the first means and responsive to said output therefrom for producing an output manifestation of oxygen saturation.