Apparatus for measuring concentration of light-absorbing substance in blood

• US 20040176670A1
• Filed: 02/02/2004
• Published: 09/09/2004
• Est. Priority Date: 01/31/2003
• Status: Active Grant

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Kobayashi, Naoki, Takeda, Sunao, Takamura, Yoshiaki, Usuda, Takashi
• Granted Patent: US 7,257,433 B2
• Time in Patent Office: Days
• US Class Current: 600/322
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: G01N 2021/3144 for oxymetry

Abstract

An apparatus for measuring a concentration of a light-absorbing substance in blood is disclosed. A light emitter emits light beams to irradiate a living tissue, each of the light beams being associated with one wavelength which is absorbed by the blood. A first instrument measures first intensities of the light beams, which are to be incident on the living tissue. A second instrument measures second intensities of the light beams, which are transmitted through the living tissue. A first calculator calculates an attenuation variation ratio, which is a ratio of attenuation variations of the respective light beams due to variation of a volume of the blood caused by pulsation, based on the second intensities of the light beams. A second calculator calculates the concentration based on the first intensities, the second intensities, and the attenuation variation ratio.

Claims

1. An apparatus for measuring a concentration of a light-absorbing substance in blood, comprising:

a light emitter, which emits light beams to irradiate a living tissue, each of the light beams being associated with one wavelength which is absorbed by the blood;

a first instrument, which measures first intensities of the light beams, which are to be incident on the living tissue;

a second instrument, which measures second intensities of the light beams, which are transmitted through the living tissue;

a first calculator, which calculates an attenuation variation ratio, which is a ratio of attenuation variations of the respective light beams due to variation of a volume of the blood caused by pulsation, based on the second intensities of the light beams; and

a second calculator, which calculates the concentration based on the first intensities, the second intensities, and the attenuation variation ratio.

2. The apparatus as set forth in claim 1, wherein:

the second calculator calculates DC components of attenuations of the light beams, based on the first intensities and the second intensities; and

the second calculator obtains the concentration, based on the DC components and the attenuation variation ratio.

3. The apparatus as set forth in claim 2, wherein:

the second calculator calculates a DC attenuation ratio which is a ratio of the DC components; and

the second calculator obtains the concentration, based on the DC attenuation ratio and the attenuation variation ratio.

4. The apparatus as set forth in claim 1, wherein:

the second calculator calculates DC components of intensities of the light beams transmitted through the living tissue, based on the first intensities and the second intensities; and

the second calculator obtains the concentration, based on the DC components and the attenuation variation ratio.

5. The apparatus as set forth in claim 4, wherein:

the second calculator calculates a DC transmission ratio which is a ratio of the DC components; and

the second calculator obtains the concentration, based on the DC transmission ratio and the attenuation variation ratio.

6. The apparatus as set forth in claim 1, wherein:

the light emitter comprises light emitting elements, and a controller which controls a current value or a voltage value supplied to the light emitting elements; and

the second calculator corrects the first intensities in accordance with the current value or the voltage value.

7. The apparatus as set forth in claim 1, wherein:

the second instrument measures third intensities of the light beams which are transmitted through a phantom placed between the light emitter and the second instrument; and

the first instrument obtains the first intensities based on the third intensities.

8. The apparatus as set forth in claim 7, wherein:

the first instrument comprises a sensor which senses whether the phantom is placed between the light emitter and the second instrument; and

the first instrument begins calculation to obtain the first intensities when the sensor senses that the phantom is placed between the light emitter and the second instrument.

11. The apparatus as set forth in claim 1, wherein the light emitter emits a light beam having a wavelength which is absorbed by a living tissue other than the blood.

9. An apparatus for measuring a concentration of a light-absorbing substance in blood, comprising:

a light emitter, which emits (n) kinds of light beams to irradiate a living tissue, each of the light beams being associated with one wavelength which is absorbed by the blood;

a first instrument, which measures (n) kinds of first intensities of the light beams, which are to be incident on the living tissue;

a second instrument, which measures (n) kinds of second intensities of the light beams, which are transmitted through the living tissue;

a first calculator, which calculates, at most, (n−

1) kinds of attenuation variation ratios, which is a ratio of attenuation variations of the respective light beams due to variation of a volume of the blood caused by pulsation, based on the second intensities of the light beams; and

a second calculator, which calculates, at most, (n) kinds of DC components of attenuations of the light beams, based on the first intensities and the second intensities, and obtains the concentration based on the DC components and the attenuation variation ratio,

wherein (n) is an integer which is three or more.

12. The apparatus as set forth in claim 9, wherein the light emitter emits a light beam having a wavelength which is absorbed by a living tissue other than the blood.

10. An apparatus for measuring a concentration of a light-absorbing substance in blood, comprising:

a light emitter, which emits (n) kinds of light beams to irradiate a living tissue, each of the light beams being associated with one wavelength which is absorbed by the blood;

a first instrument, which measures (n) kinds of first intensities of the light beams, which are to be incident on the living tissue;

a second instrument, which measures (n) kinds of second intensities of the light beams, which are transmitted through the living tissue;

a first calculator, which calculates, at most, (n−

1) kinds of attenuation variation ratios, which is a ratio of attenuation variations of the respective light beams due to variation of a volume of the blood caused by pulsation, based on the second intensities of the light beams; and

a second calculator, which calculates, at most, (n) kinds of DC components of intensities of the light beams transmitted through the living tissue, based on the first intensities and the second intensities, and obtains the concentration based on the DC components and the attenuation variation ratio,

wherein (n) is an integer which is three or more.

13. The apparatus as set forth in claim 10, wherein the light emitter emits a light beam having a wavelength which is absorbed by a living tissue other than the blood.