Blood sugar level measuring apparatus

• US 6,954,661 B2
• Filed: 08/15/2003
• Issued: 10/11/2005
• Est. Priority Date: 06/23/2003
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Cho, Ok-Kyung, Kim, Yoon-Ok
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): Kremer, Matthew
• Application Number:
  US10/641,262
• Publication Number:
  US 20040260165A1
• Time in Patent Office: 788 Days
• Field of Search: 600/316, 600322-323, 600/365, 600/326
• US Class Current: 600/316
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters

Abstract

Blood sugar levels are measured non-invasively based on temperature measurement. Measured blood sugar levels are corrected using blood oxygen saturation and blood flow volume. The measurement data is further stabilized by taking into consideration the influences of interfering substances on blood oxygen saturation.

Claims

1. A blood sugar level measuring apparatus comprising:

(1) a heat amount measuring unit for measuring a plurality of temperatures derived from a body surface in order to obtain information used for calculating the amount of convective heat transfer and the amount of radiation heat transfer concerning the dissipation of heat from the body surface;

(2) a blood flow volume measuring unit for obtaining information concerning the volume of blood flow, the blood flow volume measuring unit comprising a body-surface contact unit, an adjacent-temperature detector disposed adjacent to the body-surface contact unit, an indirect-temperature detector for detecting the temperature at a position distanced away from the body-surface contact unit, and a heat conducting member connecting the body-surface contact unit with the indirect-temperature detector;

(3) an optical measuring unit for obtaining the hemoglobin concentration and hemoglobin oxygen saturation in blood, the unit including a light source for generating light of at least three different wavelengths, an optical system for irradiating the body surface with light emitted by the light source, and at least three different photodetectors for detecting the light that has been shone on the body surface;

(4) a storage unit for storing relationships between individual parameters corresponding to the plurality of temperatures, blood flow volume, hemoglobin concentration and hemoglobin oxygen saturation in blood, and blood sugar levels;

(5) a computing unit for converting measurement values provided by the heat amount measuring unit, the blood flow volume measuring unit, and the optical measuring unit into parameters, and computing a blood sugar level by applying the parameters to the relationships stored in the storage unit; and

(6) a display unit for displaying the blood sugar level computed by the computing unit.

2. The blood sugar level measuring apparatus according to claim 1, the photodetectors include a first photodetector for detecting light reflected by the body surface, a second photodetector for detecting light scattered by the body surface, and a third photodetector for detecting light that has penetrated into the skin through the body surface and that has exited from the body surface.

3. The blood sugar level measuring apparatus according to claim 2, wherein the light source comprises a plurality of light-emitting diodes that emit light with different wavelengths, and wherein the optical system includes a first optical fiber for transmitting the light emitted by the light-emitting diodes to an irradiated portion on the body surface, and a second optical fiber for transmitting the light with which the body surface has been irradiated to the first, second and third photodetectors.

4. The blood sugar level measuring apparatus according to claim 3, wherein the tip of the optical fiber transmitting the light to the third photodetector is disposed at a location so as to be in contact with the body surface when in use.

5. The blood sugar level measuring apparatus according to claim 2, wherein the light source produces light of a wavelength at which the molar absorbance coefficients of the oxy-hemoglobin and deoxy-hemoglobin are equal, light of a first wavelength for detecting the difference in absorbance between the oxy-hemoglobin and deoxy-hemoglobin, and light of a wavelength that is absorbed by bilirubin.

6. The blood sugar level measuring apparatus according to claim 5, wherein light is produced that has a wavelength that is absorbed by turbidity in blood or by melanin pigment.

7. The blood sugar level measuring apparatus according to claim 5 or 6, wherein light of a second wavelength is produced for detecting the difference in absorbance between the oxy-hemoglobin and deoxy-hemoglobin.

8. The blood sugar level measuring apparatus according to claim 5, wherein the light of the individual wavelengths with which the body surface has been irradiated is detected by the second photodetector.

9. The blood sugar level measuring apparatus according to claim 8, wherein the computing unit corrects measurement errors due to the body surface roughness using a ratio of the absorbance measured by the first photodetector and that measured by the second photodetector.

10. The blood sugar level measuring apparatus according to claim 8, wherein the computing unit corrects measurement errors due to skin thickness using the intensity of light measured by the third detector.

11. The blood sugar level measuring apparatus according to claim 10, wherein the computing unit makes the correction by taking a ratio between the absorbance of light that has entered a standard substance with a known thickness and that has exited therefrom as measured in advance by the third detector and the absorbance measured by the third detector.

12. The blood sugar level measuring apparatus according to claim 2, wherein the light that has penetrated into the skin via the body surface and that has exited via the body surface is transmitted from an exit portion to the third photodetector via an optical path with light-blocking surroundings.

13. The blood sugar level measuring apparatus according to claim 1, wherein the heat amount measuring unit comprises an ambient temperature detector for measuring the ambient temperature, and a radiation heat detector for measuring the heat radiated from the body surface.

14. The blood sugar level measuring apparatus according to claim 1, wherein the computing unit estimates the blood flow volume by measuring the amount of heat transfer from the body surface to the heat conducting member by monitoring a chronological variation of the temperatures detected by the adjacent-temperature detector and the indirect-temperature detector, and estimates the blood flow volume based on the amount of heat transfer.

15. A blood sugar level measuring apparatus comprising:

an ambient temperature detector for measuring the ambient temperature;

a body-surface contact unit to be brought into contact with a body surface;

a radiation temperature detector for measuring the radiation heat from the body surface;

an adjacent-temperature detector disposed adjacent to the body-surface contact unit;

an indirect-temperature detector for detecting the temperature at a position distanced away from the body-surface contact unit;

a heat conducting member connecting the body-surface contact unit with the indirect-temperature detector;

a light source for producing light of at least three different wavelengths consisting of 810 nm, 950 nm, and a third wavelength;

an optical system for irradiating the body surface with the light emitted by the light source;

at least three different photodetectors for detecting the light with which the body surface has been irradiated;

a storage unit for storing the relationships between individual outputs from the ambient temperature detector, radiation temperature detector, adjacent-temperature detector, indirect-temperature detector and the at least three different photodetectors, and blood sugar levels;

a computing unit for calculating a blood sugar level using the individual outputs with reference to made to the relationships stored in the storage unit; and

a display unit for displaying the blood sugar level calculated by the computing unit.

16. The blood sugar level measuring apparatus according to claim 15, wherein the third wavelength is selected from the group consisting of 450 nm, 660 nm, 520 nm, and 880 nm.

17. The blood sugar level measuring apparatus according to claim 15, wherein the light source produces light of a fourth wavelength which is used in combination with the third wavelength, wherein the two wavelengths to be combined are selected from the group consisting of 450 nm, 660 nm, 520 nm, and 880 nm.

18. The blood sugar level measuring apparatus according to claim 15, wherein the light source produces light of a fourth and a fifth wavelength which are used in combination with the third wavelength, wherein the three wavelengths to be combined are selected from the group consisting of 450 nm, 660 nm, 520 nm, and 880 nm.

19. The blood sugar level measuring apparatus according to claim 15, wherein at least one of the photodetectors detects light that has penetrated into the skin through the body surface and that has exited from an exit portion via an optical path having light-blocking surroundings.