Method and system for measuring lactate levels in vivo

• US 20060234386A1
• Filed: 04/30/2004
• Published: 10/19/2006
• Est. Priority Date: 04/30/2003
• Status: Abandoned Application

• Current Assignee: McGill University
• Original Assignee: McGill University
• Inventors: Burns, David H., Lands, Larry, Lafrance, Denis
• Application Number:
  US10/554,698
• Publication Number:
  US 20060234386A1
• Time in Patent Office: Days
• US Class Current: 436/94
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/027 Control of working procedures of a spectrometer; Failure detection; Bandwidth calculation
• CPC Class Codes: G01J 3/427 Dual wavelengths spectrometry
• CPC Class Codes: G01J 3/44 Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
• CPC Class Codes: G01J 3/453 by correlation of the amplitudes
• CPC Class Codes: G01N 2021/3148 using three or more wavelengths
• CPC Class Codes: G01N 2021/3595 using FTIR
• CPC Class Codes: G01N 21/359 using near infrared light
• CPC Class Codes: G01N 21/4738 Diffuse reflection precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration, e.g. also for testing fluids, fibrous materials
• CPC Class Codes: G01N 21/65 Raman scattering
• CPC Class Codes: G01N 2201/0618 Halogene sources
• CPC Class Codes: G01N 2201/0627 Use of several LED's for spectral resolution
• CPC Class Codes: G01N 2201/0636 Reflectors
• CPC Class Codes: G01N 2201/129 Using chemometrical methods
• CPC Class Codes: G01N 2201/1293 resolving multicomponent spectra
• CPC Class Codes: Y10T 436/143333 : Saccharide [e.g., DNA, etc.]

Abstract

There is described a system and method for the in vivo determination of lactate levels in blood using Near-Infrared Spectroscopy (NIRS) and/or Near-infrared Raman Spectroscopy (NIR-RAMAN). The method teaches measuring lactate in vivo comprising: optically coupling a body part with a light source and a light detector the body part having tissues comprising blood vessels; injecting near-infrared (NIR) light at one or a plurality of wavelengths in the body part; detecting, as a function of blood volume variations in the body part, light exiting the body part at at least the plurality of wavelengths to generate an optical signal; and processing the optical signal as a function of the blood volume variations to obtain a lactate level in blood.

Claims

1. A method for measuring lactate in vivo comprising:

optically coupling a body part with a light source and a light detector said body part having tissues comprising blood vessels;

injecting near-infrared (NIR) light at a plurality of wavelengths in said body part;

detecting, as a function of blood volume variations in said body part, light exiting said body part at at least said plurality of wavelengths to generate an optical signal;

processing said optical signal as a function of said blood volume variations to obtain a lactate level in blood.

2. A method for measuring lactate in vivo comprising:

optically coupling a body part with a light source and a light detector said body part having tissues comprising blood vessels;

injecting NIR light at one wavelength in said body part;

detecting, as a function of blood volume variations in said body part, light exiting said body part at a plurality of wavelengths to generate an optical signal due to a Raman shift from lactate;

processing said optical signal as a function of said blood volume variations to obtain a lactate level in blood.

3. A method for measuring lactate in vivo comprising:

optically coupling a body part with a light source and a light detector said body part having tissues comprising blood vessels;

injecting near-infrared (NIR) light one or more wavelengths in said body part;

detecting, as a function of blood volume variations in said body part, light exiting said body part at a plurality of wavelengths to generate an optical signal;

processing said optical signal as a function of said blood volume variations to obtain a lactate level in blood, said processing comprising;

a) determining a regression calibration coefficient vector for each of said plurality of wavelengths;

b) obtaining a scalar product from said calibration coefficient vector and an amplitude of each of said plurality of wavelengths.

4. The method as claimed in claim 3, wherein said plurality of wavelengths have an absorption coefficient that is substantially independent of water concentration.

5. The method as claimed in claim 4, wherein said injecting and said detecting is synchronized with changes in blood volume in said body part.

6. The method as claimed in claim 5 wherein said changes in blood volumes are due to cardiac cycle.

7. The method as claimed in claim 6 wherein said lactate level is a relative level between systolic and diastolic parts of said cardiac cycle.

8. The method as claimed in claim 3, wherein said injecting and said detecting produces a time-varying optical signal, said time-varying optical signal being a function of changes of blood volume in said body part.

9. The method as claimed in claim 8, wherein said changes in blood volumes are due to cardiac cycles.

10. The method as claimed in claim 9, wherein said detecting comprises detecting light at said plurality of wavelengths to generate said time-varying optical signals and a steady state signal and wherein a ratio of said time varying optical signals and said steady state signal is obtained to thereby producing a relative signal substantially reflecting said lactate level in blood.

11. The method as claimed in claim 3, wherein said body part is a digit comprising a nail and a nail bed.

12. The method as claimed in claim 11, wherein said NIR light is injected through said nail.

13. The method as claimed in claim 12, wherein said exiting light is detected though said nail bed.

14. The method as claimed in claim 13, wherein said illuminating comprises:

a) immobilizing said digit in a sample compartment; and

b) directing said NIR light on said nail.

15. The method as claimed in claim 14, wherein said plurality of wavelengths is at least four.

16. The method as claimed in claim 15, wherein said light detected is at a same wavelength as said light injected, and the wavelengths are 1680 nm, 1690 nm, 1710 nm and 1725 nm.

17. The method as claimed in claim 16, wherein a reference optical signal is subtracted from said optical signal.

18. The method as claimed in claim 3, further comprising:

activating an alarm when said lactate level differs from a predetermined level indicative of an abnormal lactate-dependent condition; and

taking at least one corrective action in response to said abnormal lactate-dependent condition.

19. The method as claimed in claim 18, wherein said abnormal lactate-dependent condition is high lactate level in an exercising subject and wherein said corrective action comprises stopping said subject from exercising.

20. The method as claimed in claim 18, wherein said abnormal lactate-dependent condition is a clinical condition in a subject selected from myocardial infarction, cardiac arrest, circulatory failure, emergency trauma.

21. A system for measuring in vivo lactate levels comprising:

a NIR light source;

a source coupler optically coupling said light source to a body part;

detector coupler optically coupling said body part to a detector for measuring light exiting '"'"'said body part and producing an optical signal;

processor receiving said optical signal and generating a measured lactate level value; and

a monitoring device comparing said measured lactate level value with at least one predetermined lactate value, and

triggering a signal perceptible by a user when said compared values are within a predetermined range.

22. The system as claimed in claim 21, wherein said processor determines said predetermined wavelengths.

23. The system as claimed in claim 22, further comprising a wavelengths selector selecting said source wavelengths and said detector operating wavelengths.

24. The system as claimed in claim 23, further comprising a synchronizer synchronizing said measuring with a desired event.

25. The system as claimed in claim 24, wherein said event is cardiac cycle.

26. The system as claimed in claim 25, wherein said synchronizer is operationally coupled to an electrocardiograph.