Photon density wave pulse oximetry and pulse hemometry

• US 9,277,888 B2
• Filed: 02/12/2013
• Issued: 03/08/2016
• Est. Priority Date: 09/30/2008
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: McKenna, Edward M.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US13/764,947
• Publication Number:
  US 20130197331A1
• Time in Patent Office: 1,120 Days
• Field of Search: 600/310, 600/322, 600/323, 600/336, 600/473, 600/476
• US Class Current: 1/1
• 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 to at least one modulation frequency selected based on at least one blood parameter of a medium being monitored to generate photon density waves in a medium, detecting relative amplitude changes and phase shifts in the photon density waves, and determining at least one blood parameter related to scattering particles in the medium based on the phase shifts.

Claims

1. A monitoring system, comprising:

an emitter configured to emit light into tissue;

a modulator configured to modulate the light to at least one modulation frequency selected based on at least one blood parameter of the tissue being monitored to generate photon density waves in the tissue;

a detector configured to detect characteristics of the photon density waves comprising phase shifts;

a processor configured to determine a value of the at least one blood parameter of the tissue based on at least the phase shifts, and to calculate an estimated number of scattering particles in the tissue based on detected phase shifts.

2. The system of claim 1, wherein the modulator is configured to modulate the light to generate a first photon density wave of a first modulation frequency selected based on at least one absorbing property of the tissue, and wherein the modulator is configured to modulate the light to generate a second photon density wave of a second modulation frequency selected based on at least one scattering property of the tissue.

3. The system of claim 1, wherein the modulator is configured to modulate the light above approximately 50 MHz and below approximately 3 GHz.

4. The system of claim 1, comprising a plurality of emitters, wherein the modulator is configured to modulate light from the plurality of emitters to sweep the tissue with a plurality of modulation frequencies.

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

6. The system of claim 1, comprising a plurality of emitters configured to establish a phased array and comprising a second calculation component configured to utilize the phased array to identify a region of the tissue rich with pulsatile signals or a region of the tissue with low saturation.

7. The system of claim 1, comprising the detector configured to detect characteristics of the photon density waves comprising amplitude changes, and comprising a noise detection feature configured to identify noise artifacts based on a predefined range of calculated values based on the amplitude changes and phase shifts.

8. The system of claim 1, wherein the modulator is configured to establish a phased array of photon density waves for use in pulse oximetry and hemometry techniques.

9. A method, comprising:

modulating light to at least one modulation frequency selected based on at least one blood parameter of a medium being monitored to generate photon density waves in the medium;

detecting phase shifts in the photon density waves;

determining a value of the at least one blood parameter related to the scattering particles in the medium based on the phase shifts; and

calculating an estimated number of scattering particles in the tissue based on detected phase shifts.

10. The method of claim 9, comprising modulating multiple light emissions to generate a phased array of photon density waves.

11. The method of claim 10, comprising identifying regions rich with pulsatile signals based on the phased array of photon density waves.

12. The method of claim 10, comprising identifying regions of low saturation based on the phased array of photon density waves.

13. The method of claim 10, comprising modulating the light to generate a first photon density wave of a first modulation frequency selected based on at least one absorbing property of the tissue, and modulating the light to generate a second photon density wave of a second modulation frequency selected based on at least one scattering property of the tissue.

14. A monitoring system, comprising:

an emitter configured to emit light from a plurality of light sources into a medium;

a modulator configured to modulate the light from the plurality of light sources at different frequencies selected based on at least one blood parameter of the medium being monitored to generate photon density waves;

a processing system configured to coordinate the modulation of the plurality of light sources to establish coordinated wave characteristics; and

the processing system configured to determine a value for the at least one blood parameter of the medium based on at least detection of relative characteristics of the photon density waves after passing through the medium, and to calculate an estimated number of scattering particles in the tissue based on detected phase shifts.

15. The method of claim 14, wherein the processing system is configured to identify noise based on whether the coordinated wave characteristics are within a predefined physiologic regime.

16. The method of claim 14, wherein the coordinated wave characteristics comprise focused wave intensity in a specified region of the medium.

17. The method of claim 14, wherein the modulator is configured to sweep the medium with a plurality of modulation frequencies to facilitate calibration.

18. One or more non-transitory computer-readable media having stored thereon program instructions to facilitate the monitoring of blood parameters, wherein the program instructions, when executed by a computing system, direct the computing system to at least:

control modulation of light to at least one modulation frequency selected based on at least one blood parameter of tissue to generate photon density waves in a medium;

facilitate detection of phase shifts in the photon density waves;

identify a value of the at least one blood parameter related to the scattering particles in the medium based on the phase shifts; and

calculate an estimated number of scattering particles in the tissue based on detected phase shifts.

19. The one or more non-transitory computer-readable media of claim 18, wherein the program instructions further direct the computing system to calculate a value related to a number of scattering particles in the medium based on at least the phase shifts.