PROCESS AND APPARATUS FOR NON-INVASIVE, CONTINUOUS IN VIVO MEASUREMENT OF HEMATOCRIT

• US 20110077496A1
• Filed: 09/23/2010
• Published: 03/31/2011
• Est. Priority Date: 09/23/2009
• Status: Active Grant

• Current Assignee: Lightouch Medical, Inc., Syracuse University
• Original Assignee: Lightouch Medical, Inc.
• Inventors: Chaiken, Joseph
• Granted Patent: US 8,538,499 B2
• Time in Patent Office: Days
• US Class Current: 600/368
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters

Abstract

The invention provides a method and apparatus obtaining a hematocrit from a sample of in vivo tissue. The method comprises irradiating the sample with a single incident wavelength on a sample of tissue, simultaneously measuring wavelength shifted (IE) and unshifted (EE) light emitted from the tissue, and determining a relative volume of light emitted from two phases, wherein the two phases comprise a first Rayleigh and Mie scattering and fluorescent phase associated with red blood cells, and a second, non-scattering phase associated with plasma. The hematocrit is calculated from the volume of light emitted by the first phase relative to the total volume of light emitted from the first and second phases.

Claims

1. A method of obtaining a hematocrit from a sample of in vivo tissue comprising:

(a) irradiating the sample with a single incident wavelength on a sample of tissue;

(b) simultaneously measuring wavelength shifted (IE) and unshifted (EE) light emitted from the tissue; and

(c) determining a relative volume of light emitted from two phases, wherein the two phases comprise a first Rayleigh and Mie scattering and fluorescent phase associated with red blood cells, and a second, non-scattering phase associated with plasma, wherein the hematocrit is calculated from the volume of light emitted by the first phase relative to the total volume of light emitted from the first and second phases.

2. The method of claim 1, wherein the incident wavelength is 580-2500 nm.

3. The method of claim 2, wherein the incident wavelength is 785, 805 or 830 nm.

4. The method of claim 1, wherein the measuring of step (b) is at 500-1800 cm⁻

1 for shifted light, and at −

30-+10 cm<sup>−

1</sup> for unshifted light.

5. The method of claim 1, wherein the determining comprises calculating:

6. The method of claim 5, wherein the tissue is fingertip, a+b+c=0.004 and d+e+f=0.036.

7. The method of claim 1, wherein the determining comprises calculating:

8. The method of claim 7, wherein the calibration condition comprises application of pressure to the sample of tissue, wherein the pressure is greater than systolic pressure.

9. The method of claim 1, wherein the tissue is human.

10. The method of claim 1, wherein the tissue is a fingertip.

11. The method of claim 10, wherein the fingertip is pressed against an aperture of an apparatus that emits light directed at the fingertip through the aperture.

12. The method of claim 11, wherein the pressure at which the fingertip is pressed is approximately the average of the prevailing systolic and diastolic blood pressures of the subject.

13. The method of claim 5 wherein EE and IE are the AC components of the time dependent EE and IE signals.

14. The method of claim 5 wherein EE and IE are the AC components of the time dependent EE and IE signals in the bandpass of 2.5 Hz to 0.25 Hz.

15. The method of claim 5 wherein EE and IE are the DC components of the time dependent EE and IE signals.

16. The method of claim 5 wherein EE and IE are the DC components of the time dependent EE and IE signals in the bandpass of 0±

10 Hz.

17. An apparatus for obtaining a hematocrit from a sample of tissue comprising:

(a) means for irradiating the sample with a single incident wavelength on a sample of tissue;

(b) means for simultaneously measuring wavelength shifted and unshifted light emitted from the tissue;

(c) means for determining a relative volume of light emitted from two phases, wherein the two phases comprise a first predominantly Rayleigh and Mie scattering and fluorescent phase associated with red blood cells, and a second, non-scattering phase associated with plasma; and

(d) means for calculating a volume fraction of red blood cells relative to the total volume of red blood cells and plasma.

18. The apparatus of claim 17, wherein the incident wavelength is 580-2500 nm.

19. The apparatus of claim 18, wherein the incident wavelength is 785, 805 or 830 nm.

20. The apparatus of claim 17, wherein the measuring of step (b) is at 500-1800 cm⁻

1 for shifted light, and at −

30-+10 cm<sup>−

1</sup> for unshifted light.