Pulse oximeter sensor optimized for low saturation

• US 5,421,329 A
• Filed: 04/01/1994
• Issued: 06/06/1995
• Est. Priority Date: 04/01/1994
• Status: Expired due to Term

• Current Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Original Assignee: Nellcor Incorporated (Medtronic Plc)
• Inventors: Nierlich, Steve L., Mannheimer, Paul D., Ruskewicz, Stephen J., Casciani, James R.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): NASSER, ROBERT L
• Application Number:
  US08/221,911
• Time in Patent Office: 431 Days
• Field of Search: 128/633-634, 128/664-666, 356/41
• US Class Current: 600/331
• CPC Class Codes: A61B 2562/0242 for varying or adjusting the optical path length in the tissue
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1464 specially adapted for foetal tissue
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/3011 Impedance

Abstract

A pulse oximeter sensor with a light source optimized for low oxygen saturation ranges and for maximizing the immunity to perturbation induced artifact. Preferably, a red and an infrared light source are used, with the red light source having a mean wavelength between 700-790 nm. The infrared light source can have a mean wavelength as in prior art devices used on adults. The sensor of the present invention is further optimized by arranging the spacing between the light emitter and light detectors to minimize the sensitivity to perturbation induced artifact. The present invention optimizes the chosen wavelengths to achieve a closer matching of the absorption and scattering coefficient products for the red and IR light sources. This optimization gives robust readings in the presence of perturbation artifacts including force variations, tissue variations and variations in the oxygen saturation itself.

Claims

1. A method for using a pulse oximeter to measure blood oxygen saturation, comprising the steps of:

providing a sensor and a pulse oximeter;

selecting a light source for said sensor;

optimizing a wavelength spectrum of said light source for an oxygen saturation reading less than 80 percent;

placing said sensor on a patient; and

determining said blood oxygen saturation using said sensor and said pulse oximeter.

2. The method of claim 1, wherein said optimizing step is for an oxygen saturation of a fetus.

3. The method of claim 2 including optimizing said wavelength spectrum wherein the for an oxygen saturation reading less than 65 percent.

4. The method of claim 2 including optimizing said wavelength spectrum for an oxygen saturation reading greater than 15%.

5. The method of claim 4 wherein said spacing of said light source from said detector is at least 10 mm.

6. The method of claim 2 further comprising the step of:

placing a detector on said sensor;

optimizing a spacing of said light source from said detector to reduce the sensitivity of said sensor to perturbation induced artifact; and

measuring the intensity of light from said light source at said detector using reflectance of the light through said fetus.

7. The method of claim 2 wherein said light source comprises a red and an infrared light source, said optimizing step comprising using an infrared light source in a range useful for adults, and optimizing the wavelength spectrum of said red light source for a fetus.

8. The method of claim 7 wherein the mean wavelength of said red light source is between 700 and 790 nanometers.

9. The method of claim 7 wherein the spectrum of said red light source includes 735 nanometers at an intensity of at least 50% of the intensity of any other wavelengths in said spectrum.

10. The method of claim 2 wherein said optimizing step increases a depth of penetration of said light in a fetus compared to optimum penetration depth for an adult.

11. The method of claim 1 wherein said light source comprises a red and an infrared light source, each of said red and infrared light source having an extinction and a scattering coefficient for blood perfused tissue, said optimizing step comprising choosing wavelengths of said red and infrared light source whose product of their extinction and scattering coefficients form first and second values, a ratio between said first and second values being between 0.5 and 2 for a majority of the oxygen saturation reading range of 0to 65 percent.

12. The method of claim 1 wherein said optimizing step reduces the sensitivity of said determining step to artifact and decreases the sensitivity to changes in saturation.

13. A method for using a pulse oximeter to measure blood oxygen saturation in a fetus, comprising the steps of providing a sensor and a pulse oximeter;

selecting a red and an infrared light source for said sensor, said infrared light source having a wavelength spectrum useful for measuring oxygen saturation in an adult;

optimizing a wavelength spectrum of said red light source to a mean wavelength between 700 and 790 nanometers for an oxygen saturation reading between 15 and 65 percent, said optimizing increasing the immunity of a measurement of blood oxygen saturation to exsanguination artifact due to pressure of said sensor against said fetus;

placing said sensor on said fetus;

measuring an intensity of light from said light sources at a detector after reflectance through a portion of said fetus; and

determining said blood oxygen saturation using said intensity and said pulse oximeter.

14. A method for using a pulse oximeter to measure blood oxygen saturation in a fetus, comprising the steps of providing a sensor and a pulse oximeter;

selecting red and an infrared light source, each of said red and infrared light source having an extinction and a scattering coefficient for blood perfused tissue,;

optimizing a wavelength spectrum of said light sources by choosing wavelengths of said red and infrared light source whose product of their extinction and scattering coefficients form first and second values, a ratio between said first and second values being between 0.5 and 2 for a majority of the oxygen saturation reading range of 0 to 65 percent;

placing said sensor on said fetus; and

determining said blood oxygen saturation using said sensor and said pulse oximeter.