Wavelength-Division Multiplexing In A Multi-Wavelength Photon Density Wave System

• US 20110071371A1
• Filed: 09/21/2009
• Published: 03/24/2011
• Est. Priority Date: 09/21/2009
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: McKenna, Edward M., Li, Youzhi, Lin, Andy S.
• Granted Patent: US 8,494,604 B2
• Time in Patent Office: Days
• US Class Current: 600/310
• CPC Class Codes: A61B 2562/223 Optical cables therefor
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/14551 for measuring blood gases

Abstract

Multi-wavelength photon density wave medical systems, methods, and devices are provided. In one embodiment, a multi-wavelength photon density wave patient monitor includes multiple light sources, a driving circuit, a fiber coupler, a sensor cable connector, a wavelength demultiplexer, detectors, and data processing circuitry. The driving circuit may modulate the light sources to produce several single-wavelength input photon density wave signals, which the fiber coupler may join into a multi-wavelength input signal. The sensor cable connector may provide this multi-wavelength input signal to a sensor attached to the patient and receive a multi-wavelength output signal. The wavelength demultiplexer may separate the multi-wavelength output signal into single-wavelength output signals for detection by the detectors. Based on a comparison of one of the single-wavelength output signals to a corresponding one of the single-wavelength input signals, the data processing circuitry may determine a physiological parameter of the patient.

Claims

1. A patient monitor comprising:

one or more light sources capable of emitting a respective plurality of wavelengths of light;

a driving circuit capable of modulating the one or more light sources at modulation frequencies sufficient to produce resolvable photon density waves in a patient to produce a plurality of single-wavelength input photon density wave signals;

a fiber coupler capable of combining the plurality of single-wavelength input photon density wave signals into a multi-wavelength input photon density wave signal;

a sensor cable connector capable of providing the multi-wavelength input photon density wave signal to a first optical cable coupled to a medical sensor attached to the patient and capable of receiving a multi-wavelength output photon density wave signal from a second optical cable coupled to the medical sensor;

a wavelength demultiplexer capable of separating the multi-wavelength output photon density wave signal into a plurality of single-wavelength output photon density wave signals that correspond respectively to the plurality of single-wavelength input photon density wave signals; and

data processing circuitry capable of determining a physiological parameter of the patient based at least in part on a comparison of one of the plurality of single-wavelength output photon density wave signals to a corresponding one of the plurality of single-wavelength input photon density wave signals.

2. The patient monitor of claim 1, wherein the one or more light sources comprise one or more laser diodes capable of being modulated at modulation frequencies sufficient to produce resolvable photon density waves in the patient.

3. The patient monitor of claim 1, wherein the driving circuit is capable of modulating the one or more light sources at modulation frequencies between 50 MHz and 3 GHz.

4. The patient monitor of claim 1, wherein the driving circuit is capable of modulating the one or more light sources at different respective modulation frequencies.

5. The patient monitor of claim 1, wherein the wavelength demultiplexer comprises an optical filter, grating, and/or a combination thereof.

6. The patient monitor of claim 1, wherein the data processing circuitry is capable of determining an absorption property of the patient based at least in part on a change in amplitude between the one of the plurality of single-wavelength output photon density wave signals and the corresponding one of the plurality of single-wavelength input photon density wave signals.

7. The patient monitor of claim 1, wherein the data processing circuitry is capable of determining a scattering property of the patient based at least in part on a change in phase between the one of the plurality of single-wavelength output photon density wave signals and the corresponding one of the plurality of single-wavelength input photon density wave signals.

8. A system comprising:

a sensor having an emitter output and a detector input, wherein the emitter output is configured to pass an input multi-wavelength photon density wave signal into a patient and wherein the detector input is configured to receive an output multi-wavelength photon density wave signal from the patient resulting from the passing of the input multi-wavelength photon density wave signal through pulsatile tissue of the patient;

a sensor cable coupled to the sensor and having a first optical cable capable of transmitting the input multi-wavelength photon density wave signal to the sensor and having a second optical cable capable of receiving the output multi-wavelength photon density wave signal; and

a patient monitor capable of coupling to the sensor cable, generating the input multi-wavelength photon density wave signal by modulating a plurality of light sources at modulation frequencies sufficient to produce resolvable photon density waves in the pulsatile tissue of the patient to produce a plurality of input photon density wave signals, and coupling the plurality of input photon density wave signals together into the first optical cable of the sensor cable.

9. The system of claim 8, wherein the sensor is a transmission-type, reflectance-type sensor, and/or a combination thereof.

10. The system of claim 8, wherein the sensor cable comprises no greater than two optical cables.

11. The system of claim 8, wherein the sensor cable comprises a length containing essentially only optical cables.

12. The system of claim 8, wherein the plurality of light sources comprises a red light source, a near infrared source, an infrared light source, and/or any combination thereof.

13. The system of claim 8, wherein the plurality of light sources comprises a red light source, a far red light source, and an infrared light source.

14. The system of claim 8, wherein the patient monitor is capable of receiving and demultiplexing the output multi-wavelength photon density wave signal to obtain a plurality of output photon density wave signals that corresponds respectively to the plurality of input photon density wave signals.

15. The system of claim 14, wherein the patient monitor is capable of determining a physiological parameter of the patient based at least in part on a comparison of one of the plurality of output photon density wave signals to a corresponding one of the plurality of input photon density wave signals.

16. The system of claim 14, wherein the patient monitor is capable of determining a physiological parameter of the patient based at least in part on a perceived change in phase between one of the of the plurality of output photon density wave signals and a corresponding one of the plurality of input photon density wave signals.

17. The system of claim 14, wherein the patient monitor is capable of determining a physiological parameter of the patient based at least in part on a perceived change in amplitude between one of the of the plurality of output photon density wave signals and a corresponding one of the plurality of input photon density wave signals.

18. A method comprising:

simultaneously modulating two light sources of different wavelengths at one or more respective modulation frequencies sufficient to produce resolvable photon density waves in pulsatile tissue of a patient to produce two input photon density wave signals;

combining the two input photon density wave signals into a first optical cable;

emitting the two input photon density wave signals through the pulsatile tissue of the patient using a sensor coupled to the first optical cable and attached to the patient;

receiving two output photon density wave signals that result when the two input photon density wave signals are emitted through the pulsatile tissue of the patient into a second optical cable using the sensor attached to the patient;

demultiplexing the two output photon density wave signals from the second optical cable; and

comparing phases of the two output photon density wave signals to respective phases of the two input photon density wave signals to determine scattering properties of the pulsatile tissue of the patient using phase detection circuitry and data processing circuitry.

19. The method of claim 18, wherein the two light sources are modulated at different respective modulation frequencies.

20. The method of claim 18, comprising comparing amplitudes of the two output photon density wave signals to respective amplitudes of the two input photon density wave signals to determine absorption properties of the pulsatile tissue of the patient using amplitude detection circuitry and the data processing circuitry.