Laser Self-Mixing Sensors for Biological Sensing

• US 20100081940A1
• 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 8,532,751 B2
• Time in Patent Office: Days
• US Class Current: 600/479
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 7/4916 using self-mixing in the laser cavity

Abstract

According to embodiments, systems, devices, and methods for biological sensing with laser self-mixing sensors are disclosed. In one embodiment, one or more self-mixed laser Doppler signals may be used to detect blood flow velocity or blood vessel wall velocity. In one embodiment, a blood vessel wall compliance may be derived from the blood vessel wall velocity. In one embodiment, blood pressure may be calculated based at least in part on blood flow velocity or based at least in part on blood flow velocity and blood vessel compliance. In one embodiment, common mode noise may be removed from one or more laser signals.

Claims

1. A method for monitoring blood pressure, comprising:

receiving a first self-mixed laser Doppler signal, wherein the first laser signal represents at least in part a flow velocity of blood through a blood vessel;

deriving, based at least in part on the first laser signal, the blood flow velocity; and

calculating, based at least in part on the derived flow velocity, a blood pressure value.

2. The method of claim 1, wherein a first frequency shift is determined at least in part from the first self-mixed laser Doppler signal and wherein the flow velocity is determined at least in part from the first frequency shift.

3. The method of claim 1, wherein a visual or auditory signal representing the amplitude of the first self-mixed laser Doppler signal is output.

4. The method of claim 1, further comprising:

receiving a second self-mixed laser Doppler signal, wherein the second laser signal represents at least in part the movement of the blood vessel wall; and

deriving a compliance of the blood vessel wall based at least in part on the second laser signal, and

wherein calculating the blood pressure value comprises calculating the blood pressure value based at least in part on the derived flow velocity and the derived compliance.

5. The method of claim 4, wherein the first and second laser signals are converted to a first and second electric signal, common-mode noise is removed from the first electric signal to form a first modified electric signal, common-mode noise is removed from the second electric signal to form a second modified electric signal, and the first and second modified electric signals are used to determine at least in part the blood flow velocity and the compliance of the blood vessel wall.

6. The method of claim 4, wherein a first frequency shift is determined at least in part from the first self-mixed laser Doppler signal and a second frequency shift is determined at least in part from the second self-mixed laser Doppler signal, and wherein the flow velocity is determined at least in part from the first frequency shift and the blood vessel wall compliance is determined at least in part from the second frequency shift.

7. The method of claim 4, wherein a visual or auditory signal representing the amplitude of the first self-mixed laser Doppler signal, the second self-mixed laser Doppler signal, or a combination of the first and second self-mixed laser Doppler signal is output.

8. A method for determining blood vessel compliance, comprising:

receiving a self-mixed laser Doppler signal, wherein the laser signal represents at least in part the movement of the blood vessel wall; and

deriving, based at least in part on the laser signal, a compliance of the blood vessel wall.

9. The method of claim 8, wherein a frequency shift is determined at least in part from the self-mixed laser Doppler signal, and wherein the blood vessel wall compliance is determined at least in part from the frequency shift.

10. The method of claim 8, wherein a visual or auditory signal representing the amplitude of the self-mixed laser Doppler signal is output.

11. A device for monitoring blood pressure, the device comprising:

a processor capable of

receiving a first signal, wherein the first signal represents at least in part a flow velocity of blood through a blood vessel;

deriving, based at least in part on the first signal, the blood flow velocity; and

calculating, based at least in part on the derived flow velocity, a blood pressure value.

12. The device of claim 11, wherein the processor is further capable of:

deriving at least in part a first frequency shift from the first signal; and

deriving at least in part the flow velocity from the first frequency shift.

13. The device of claim 11, further comprising a notifier capable of outputting a visual or auditory signal representing the amplitude of the first signal.

14. The device of claim 11, wherein the processor is further capable of receiving a second signal, wherein the second signal represents at least in part the movement of a blood vessel wall;

and

deriving, based at least in part on the second signal, the compliance of the blood vessel wall, and

wherein calculating the blood pressure value comprises calculating the blood pressure value based at least in part on the derived flow velocity and the derived compliance.

15. The device of claim 14, further comprising:

a filter module, capable of;

removing common noise from the first signal to form a first modified signal;

removing common noise from the second signal to form a second modified signal, and

wherein the processor is further capable of determining the blood flow velocity and the compliance of the blood vessel wall based at least in part on the first and second modified signals.

16. The device of claim 14, wherein the processor is further capable of:

deriving a first frequency shift at least in part from the first signal;

deriving a second frequency shift at least in part from the second signal;

deriving the flow velocity at least in part from the first frequency shift; and

deriving the blood vessel wall compliance at least in part from the second frequency shift.

17. The device of claim 14, further comprising a notifier capable of outputting a visual or auditory signal representing the amplitude of the first signal, the second signal, or a combination of the first and second signals.

18. A device for determining blood vessel wall compliance, the device comprising:

a processor capable of

receiving a signal, wherein the signal represents at least in part the movement of a blood vessel wall; and

deriving, based at least in part on the signal, the compliance of the blood vessel wall.

19. The device of claim 18, further comprising:

a filter module, capable of;

removing common noise from the signal to form a modified signal,

wherein the processor is further capable of determining the blood vessel compliance based at least in part on the modified signal.

20. The device of claim 18, wherein the processor is further capable of:

deriving at least in part a frequency shift from the signal; and

deriving at least in part the blood vessel wall compliance from the frequency shift.

21. The device of claim 18, further comprising a notifier capable of outputting a visual or auditory signal representing the amplitude of the signal.

22. A computer readable medium storing computer executable instructions, which, when executed by a processor, cause the processor to carry out a method comprising:

receiving a first self-mixed laser Doppler signal, wherein the first laser signal represents at least in part a flow velocity of blood through a blood vessel;

deriving, based at least in part on the first laser signal, the blood flow velocity; and

calculating, based at least in part on the derived flow velocity, a blood pressure value.

23. The computer readable medium of claim 22, wherein a first frequency shift is determined at least in part from the first self-mixed laser Doppler signal and wherein the flow velocity is determined at least in part from the first frequency shift.

24. The computer readable medium of claim 22, wherein a visual or auditory signal representing the amplitude of the first self-mixed laser Doppler signal is output.

25. The computer readable medium of claim 22, wherein the method further comprises:

receiving a second self-mixed laser Doppler signal, wherein the second laser signal represents at least in part the movement of the blood vessel wall; and

deriving, based at least in part on the second laser signal, a compliance of the blood vessel wall, and

wherein calculating the blood pressure value comprises calculating the blood pressure value based at least in part on the derived flow velocity and the derived compliance.

26. The computer readable medium of claim 25, wherein the first and second laser signals are converted to a first and second electric signals, common-mode noise is removed from the first electric signal to form a first modified electric signal, common-mode noise is removed from the second electric signal to form a second modified electric signal, and the first and second modified electric signals are used to determine at least in part the blood flow velocity and the compliance of the blood vessel wall.

27. The computer readable medium of claim 25, wherein a first frequency shift is determined at least in part from the first self-mixed laser Doppler signal and a second frequency shift is determined at least in part from the second self-mixed laser Doppler signal, and wherein the flow velocity is determined at least in part from the first frequency shift and the blood vessel wall compliance is determined at least in part from the second frequency shift.

28. The computer readable medium of claim 25, wherein a visual or auditory signal representing the amplitude of the first self-mixed laser Doppler signal, the second self-mixed laser Doppler signal, or a combination of the first and second self-mixed laser Doppler signal is output.

29. A computer readable medium storing computer executable instructions, which, when executed by a processor, cause the processor to carry out a method comprising:

receiving a self-mixed laser Doppler signal, wherein the laser signal represents at least in part the movement of the blood vessel wall; and

deriving, based at least in part on the laser signal, a compliance of the blood vessel wall.

30. The computer readable medium of claim 29, wherein a frequency shift is determined at least in part from the self-mixed laser Doppler signal, and wherein the blood vessel wall compliance is determined at least in part from the frequency shift.

31. The computer readable medium of claim 29, wherein a visual or auditory signal representing the amplitude of the self-mixed laser Doppler signal is output.