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

• US 20110071373A1
• 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: Li, Youzhi, Lin, Andy S., McKenna, Edward M.
• Granted Patent: US 8,788,001 B2
• Time in Patent Office: Days
• US Class Current: 600/324
• 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 system may include a sensor, a sensor cable, and a patient monitor. The sensor may have an emitter output and a detector input configured to pass a multi-wavelength photon density wave input signal into a patient and receive a resulting multi-wavelength photon density wave output signal. The sensor cable may couple to the sensor using two optical cables for transmitting and receiving the multi-wavelength photon density wave signals. The patient monitor may couple to the sensor cable and generate several time-division multiplexed single-wavelength input signals by modulating one or more light sources at a frequency sufficient to produce resolvable photon density waves. By combining the several time-division multiplexed single-wavelength input signals into one of the optical cables of the sensor cable, the patient monitor may generate the multi-wavelength photon density wave input signal.

Claims

1. A system comprising:

a patient monitor capable of generating a multi-wavelength photon density wave input signal by modulating one or more light sources at one or more modulation frequencies sufficient to produce resolvable photon density waves in pulsatile tissue of a patient, receiving a multi-wavelength photon density wave output signal resulting after the multi-wavelength photon density wave input signal is passed through the pulsatile tissue of the patient, and determining a scattering property and an absorption property of the pulsatile tissue of the patient based at least in part on a comparison between the multi-wavelength photon density wave output signal and the multi-wavelength photon density wave input signal;

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

a sensor cable coupled to the sensor and having a first optical cable capable of transmitting the multi-wavelength photon density wave input signal from the patient monitor to the sensor and having a second optical cable capable of transmitting the multi-wavelength photon density wave output signal from the sensor to the patient monitor.

2. The system of claim 1, wherein the sensor is a transmission-type sensor, a reflectance-type sensor, and/or a combination thereof.

3. The system of claim 1, wherein the sensor cable comprises no more than two optical cables.

4. The system of claim 1, wherein the sensor cable comprises only one or more optical cables.

5. The system of claim 1, wherein the one or more light sources comprise a red light source and/or an infrared light source and/or a near infrared light source, or any combination thereof.

6. The system of claim 1, wherein the patient monitor is capable of generating the multi-wavelength photon density wave input signal by generating and time-division multiplexing a plurality of single-wavelength photon density wave input signals.

7. The system of claim 6, wherein the patient monitor is capable of time-division demultiplexing the multi-wavelength photon density wave output signal to obtain a plurality of single-wavelength photon density wave output signals that corresponds respectively to the plurality of time-division multiplexed single-wavelength photon density wave input signals.

8. The system of claim 7, 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 single-wavelength photon density wave output signals to a corresponding one of the plurality of time-division multiplexed single-wavelength photon density wave input signals.

9. The system of claim 7, wherein the patient monitor is capable of determining a physiological parameter of the patient based at least in part on a change in phase between one of the plurality of single-wavelength photon density wave output signals and a corresponding one of the plurality of time-division multiplexed single-wavelength photon density wave input signals.

10. The system of claim 7, wherein the patient monitor is capable of determining a physiological parameter of the patient based at least in part on a change in amplitude between one of the plurality of single-wavelength photon density wave output signals and a corresponding one of the plurality of time-division multiplexed single-wavelength photon density wave input signals.

11. A patient monitor comprising:

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

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

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

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

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

12. The patient monitor of claim 11, wherein the one or more light sources comprise one or more laser diodes.

13. The patient monitor of claim 11, wherein the driving circuit is capable of modulating the one or more of light sources at modulation frequencies between 50 MHz and 3 GHz.

14. The patient monitor of claim 11, wherein the driving circuit is capable of modulating the one or more light sources such that each of the plurality of single-wavelength photon density wave input signals has a different respective modulation frequency.

15. The patient monitor of claim 11, 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 photon density wave output signals and the corresponding one of the plurality of single-wavelength photon density wave input signals.

16. The patient monitor of claim 11, wherein the data processing circuitry is capable of determining an 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.

17. A method comprising:

generating a first photon density wave signal by modulating a light source of a first wavelength using a driving circuit;

emitting the first photon density wave input signal through the pulsatile tissue of the patient for a first period of time using a sensor coupled to an input optical cable and attached to the patient;

receiving a first photon density wave output signal that results when the first photon density wave input signal is emitted through the pulsatile tissue of the patient into an output optical cable using the sensor attached to the patient;

generating a second photon density wave signal by modulating a light source of second wavelength at the modulation frequency using the driving circuit;

emitting the second photon density wave input signal through the pulsatile tissue of the patient for a second period of time using the sensor coupled to the input optical cable and attached to the patient, wherein the first period of time and the second period of time do not overlap;

receiving a second photon density wave output signal that results when the second photon density wave input signal is emitted through the pulsatile tissue of the patient into the output optical cable using the sensor attached to the patient; and

comparing phases and/or amplitudes of the first and second photon density wave output signals to respective phases of the first and second photon density wave input signals to determine a scattering property and/or an absorption property of the pulsatile tissue of the patient using phase detection circuitry, signal processing circuitry, and/or data processing circuitry.

18. The method of claim 17, wherein the second photon density wave signal is emitted for the second period of time, wherein the second period of time begins immediately after the first period of time or following a dark period after the first period of time.

19. The method of claim 18, wherein the second photon density wave signal is emitted for the second period of time, wherein the second period of time and the first period of time are sufficiently brief such that substantially no perceptible change in the pulsatile tissue of the patient has occurred between the start of the first period of time and the start of the second period of time.

20. The method of claim 17, wherein the second photon density wave signal is emitted for the second period of time, wherein the second period of time occupies the same quantity of time as the first period of time.