System and Method for Photon Density Wave Pulse Oximetry and Pulse Hemometry

• US 20100081899A1
• Filed: 09/30/2008
• Published: 04/01/2010
• Est. Priority Date: 09/30/2008
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: McKenna, Edward M.
• Granted Patent: US 8,386,000 B2
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7228 Signal modulation applied to the input signal sent to patient or subject; demodulation to recover the physiological signal modulation H03C

Abstract

Present embodiments are directed to a system and method capable of modulating light at a modulation frequency, wherein the modulation frequency is somewhere above about 50 MHz and below about 3 GHz, to generate photon density waves in a medium, detecting relative amplitude changes and phase shifts in the photon density waves, and detecting and graphically indicating a physiologic value related to scattering particles in the medium based on the phase shifts.

Claims

1. A monitoring system, comprising:

an emitter capable of emitting light into tissue;

a modulator capable of modulating the light to generate photon density waves at a modulation frequency, wherein the modulation frequency is somewhere above about 50 MHz and below about 3 GHz;

a detector capable of detecting relative characteristics of the photon density waves including amplitude changes and phase shifts;

a processor capable of making determinations relating to a value of a physiologic parameter of the tissue based on the phase shifts; and

a display feature capable of presenting the value of the physiologic parameter to a user.

2. The system of claim 1, wherein the processor is capable of rejecting or accepting the determined value of the physiologic parameter based on whether calculations based on the relative characteristics are complimentary.

3. The system of claim 1, wherein the modulator is capable of modulating the light at the modulation frequency somewhere above approximately 100 MHz and below approximately 1 GHz.

4. The system of claim 1, wherein the processor is capable of calculating an estimated number of scattering particles in the tissue based on detected phase shifts.

5. The system of claim 1, comprising a plurality of emitters, wherein the modulator is capable of modulating light from the plurality of emitters to sweep the tissue with a plurality of modulation frequencies.

6. The system of claim 1, wherein the modulator comprises a DVD R/W driver circuit.

7. The system of claim 1, comprising a plurality of emitters capable of establishing a phased array and a second calculation component capable of utilizing the phased array to identify a region of the tissue rich with pulsatile signals and/or a region of the tissue with low saturation.

8. The system of claim 1, comprising a noise detection feature capable of identifying noise artifacts based on a defined range of calculated values based on the amplitude changes and phase shifts.

9. The system of claim 1, wherein the modulator is capable of establishing a phased array of photon density waves for use in pulse oximetry and hemometry techniques.

13. The method of claim 1, comprising identifying regions of low saturation based on the phased array of photon density waves.

10. A method, comprising:

modulating light at a modulation frequency that is within a range between 100 MHz and 3 GHz to generate photon density waves in a medium;

detecting relative amplitude changes and phase shifts in the photon density waves; and

detecting and graphically indicating a physiologic value related to scattering particles in the medium based on the phase shifts.

11. The method of claim 10, comprising modulating multiple light emissions to generate a phased array of photon density waves.

12. The method of claim 11, comprising identifying regions rich with pulsatile signals based on the phased array of photon density waves.

14. The method of claim 10, comprising sweeping the modulation frequency through a range from 500 MHz to 1 GHz.

15. A method, comprising:

emitting light from a plurality of light sources into a medium;

modulating the light from the plurality of light sources at different frequencies to generate photon density waves, wherein the different frequencies are approximately 100 MHz to 1 GHz;

coordinating the modulation of the plurality of light sources to establish coordinated wave characteristics; and

calculating values for physiologic features of the medium based on detection of relative characteristics of the photon density waves after passing through the medium.

16. The method of claim 15, comprising identifying noise based on whether the coordinated wave characteristics are within a defined physiologic regime.

17. The method of claim 15, wherein the coordinated wave characteristics comprise focused wave intensity in a specified region of the medium.

18. The method of claim 15, comprising sweeping the medium with a plurality of modulation frequencies to facilitate calibration.

19. Application instructions stored on a tangible computer-readable medium, the application instructions comprising:

code capable of controlling modulation of light at a modulation frequency to generate photon density waves in a medium, wherein the modulation frequency is somewhere above about 100 MHz and below about 3 GHz;

code capable of facilitating detection of relative amplitude changes and phase shifts in the photon density waves; and

code capable of identifying and graphically indicating a physiologic value related to scattering particles in the medium based on the phase shifts.

20. The application instructions of claim 19, comprising code capable of calculating a value related to a number of scattering particles in the medium based on the phase shifts.

21. The application instructions of claim 19, comprising code capable of controlling modulation of multiple light emissions to generate a phased array of photon density waves.