Method of optical measurements for determining various parameters of the patient's blood

• US 20040176671A1
• Filed: 03/22/2004
• Published: 09/09/2004
• Est. Priority Date: 12/22/1999
• Status: Active Grant

• Current Assignee: OrSense Ltd.
• Original Assignee: OrSense Ltd.
• Inventors: Shvartsman, Leonid, Fine, Ilya
• Granted Patent: US 7,043,289 B2
• Time in Patent Office: Days
• US Class Current: 600/322
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• 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 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6825 Hand
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: G01N 2015/0092 Monitoring flocculation or agglomeration
• CPC Class Codes: G01N 2015/012 Red blood cells

Abstract

A method for optical measurements of desired parameters of the patient'"'"'s blood is presented. A state of the blood flow cessation is provided within a measurement region and maintained during a predetermined time period. Measurement sessions are performed within this predetermined time period. Each measurement session includes at least two measurements with different wavelengths of incident light. Obtained measured data is representative of the time dependence of light response of the blood in the measurement region. The analyses of the measured data enables the determination of the desired blood parameters extracted from optical characteristics associated with the erythrocytes aggregation process during the state of the blood flow cessation.

Claims

1. A method of optical measurements of at least one desired parameter of a patient'"'"'s blood, comprising:

providing a state of blood flow cessation of the patient'"'"'s blood within a measurement region, and maintaining the blood-flow cessation state during a predetermined time period;

performing measurement sessions within said predetermined time period, each measurement session including at least two measurements with different wavelengths of incident light, and obtaining measured data representative of the time dependence of light response of the blood in the measurement region;

analyzing the measured data for determining said at least one desired parameter, extracted from optical characteristics associated with erythrocytes aggregation process during the state of the blood flow cessation.

2. The method according to claim 1, wherein said state of the blood flow cessation in the measurement region is provided by applying an occlusion mode to the patient'"'"'s blood perfused fleshy medium.

3. The method according to claim 2, wherein the application of the occlusion mode comprises the application of over-systolic pressure to the patient'"'"'s blood perfused fleshy medium at a location upstream of said measurements region with respect to the direction of the normal blood flow in the patient'"'"'s body.

4. The method according to claim 3, and also comprising the step of preliminary optical measurements for detecting the existence of the blood flow cessation state.

5. The method according to claim 2, wherein said predetermined period of time is insufficient for irreversible changes to occur in the fleshy medium.

6. The method according to claim 5, wherein said predetermined period of time is from one second to several minutes.

7. The method according to claim 1, wherein said state of the blood flow cessation in the measurement region is provided by applying an occlusion mode to the flow of the patient'"'"'s blood sample into a cuvette, said measurement region being located in the cuvette.

8. The method according to claim 1, wherein the analyzing of the measured data comprises the step of:

determining a Rouleaux Geometry Factor (RGF) characterizing the changes of the light response of blood in the state of blood flow cessation as the function of time and wavelengths of the incident radiation, associated with the erythrocytes'"'"' aggregation.

9. The method according to claim 8, wherein the determination of the RGF comprises:

determining a ratio Δ

(log T)/Δ

t as the function of wavelength λ

obtained from the several measurement sessions with the different wavelengths, Δ

t being a preset time interval of said predetermined period of time; and

determining a cut-off wavelength corresponding to the condition Δ

(log T)/Δ

t=0.

10. The method according to claim 8, wherein the determination of the RGF comprises:

determining a ratio or Δ

T/Δ

t as the function of wavelength λ

obtained from the several measurement sessions with the different wavelengths, Δ

t being a preset time interval of said predetermined period of time; and

determining a cut-off wavelength is that corresponding to the condition or Δ

T/Δ

t=0.

11. The method according to claim 9, wherein said preset time interval is an asymptotic time interval characterized by relatively slow changes of the light response signal with time, as compared to an initial time interval of said predetermined period of time.

12. The method according to claim 9, wherein said desired parameter to be determined is an evaluated value of a parameter (n_Hb−

n_pl) for said patient, wherein n_Hb is the refraction index of hemoglobin in erythrocyte, and n_pl is the refraction index of plasma.

13. The method according to claim 12, wherein the evaluation of the parameter (n_Hb−

n_pl) comprises the utilization of theoretical data representative of a scattering function K(x(n_Hb−

n_pl)), wherein x=2π

a/λ

, a being the effective size of erythrocyte.

14. The method according to claim 1, wherein the analyzing of the measured data comprises the steps of:

determining a parametric slope, said at least two wavelengths being selected in accordance with said desired parameter to be determined; and

using reference data in the form of a calibration curve of the parametric slope as a function of values of the desired parameter.

15. The method according to claim 14, wherein the determination of the parametric slope comprises the determination of a function T_λ

2(T<sub>λ

2</sub>), wherein T<sub>λ

2</sub> and T<sub>λ

1</sub> are the measured data corresponding to the wavelengths λ

₂ and λ

₁ of the incident radiation, respectively, the function T<sub>λ

2</sub>(T<sub>λ

1</sub>) being determined for a preset time interval of said predetermined time period.

16. The method according to claim 14, wherein the determination of the parametric slope comprises the determination of a function log T_λ

2(log T<sub>λ

2</sub>), wherein T<sub>λ

2</sub> and T<sub>λ

1</sub> are the measured data corresponding to the wavelengths λ

₂ and λ

₁ of the incident radiation, respectively, the function T<sub>λ

2</sub>(T<sub>λ

2</sub>) being determined for a preset time interval of said predetermined time period.

17. The method according to claim 15, wherein said preset time interval is an initial time interval characterized by relatively strong changes of the light response signal with time, as compared to a next, asymptotic time interval of said predetermined period of time.

18. The method according to claim 15, wherein said preset time interval is an asymptotic time interval characterized by relatively slow changes of the light response signal with time, as compared to an initial time interval of said predetermined period of time.

19. A method of optical measurements of desired parameters of the patient'"'"'s blood extracted from optical characteristics associated with erythrocytes aggregation process during the state of the blood flow cessation, comprising:

providing the state of the blood flow cessation within a measurement region, and maintaining the blood-flow cessation state during a predetermined time period;

performing measurement sessions within said predetermined time period, each measurement session including at least two measurements with different wavelengths of incident light, and obtaining measured data representative of the time dependence of light response of the blood in the measurement region;

analyzing the measured data for determining said at least one desired parameter, by determining at least one parametric slope value and a Rouleaux Geometry Factor (RGF) for said patient, the RGF characterizing the changes of the light response of blood at the state of the blood flow cessation as the function of time and wavelengths of the incident radiation, associated with the erythrocytes'"'"' aggregation.

20. A method of optical measurements of at least one desired parameter of blood of a specific patient extracted from optical characteristics associated with erythrocytes aggregation process during the state of the blood flow cessation, comprising:

providing reference data in the form of a function describing diffraction effects on particles, K(x(n_Hb−

n_H2O), wherein x=2π

a/λ

;

a is the size of erythrocyte, n_Hb is the refraction index of hemoglobin and n_pl is the refraction index of water, λ

is the wavelength of incident radiation;

providing the state of the blood flow cessation and maintaining said state during a predetermined period of time;

performing measurement sessions within said predetermined time period, each measurement session including several measurements with different wavelengths of incident radiation, and obtaining measured data representative of the time dependence of light response signals;

analyzing the measured data for determining a Rouleaux Geometry Factor (RGF) for the specific patient, the RGF characterizing the changes of the light response of blood at the state of the blood flow cessation as the function of time and wavelengths of the incident radiation, associated with the erythrocytes'"'"' aggregation.