Device for measuring light absorption materials in blood

• US 6,453,184 B1
• Filed: 09/13/2000
• Issued: 09/17/2002
• Est. Priority Date: 09/13/1999
• Status: Active Grant

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Ozawa, Hideo, Hyogo, Mitsushi, Ukawa, Teiji
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): Kremer, Matthew J.
• Application Number:
  US09/661,199
• Time in Patent Office: 734 Days
• Field of Search: 600/309, 600/310, 600/322, 600/324, 600/330, 600/336, 356/39-42
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14551 for measuring blood gases

Abstract

A red light and an infrared light which are emitted from a light emitting portion 2 are transmitted through a fingertip 4 of a subject and are converted into electric signals by a light receiving portion 3. The respective signals are separated and amplified and are then sent to a CPU 8. In the CPU 8, the input signals are divided into D.C. components DC1 and DC2 and A.C. components AC1 and AC2, changes ΔA1=(AC/DC) 1 and ΔA2=(AC/DC)2 in an absorbance are calculated, high frequency components thereof are extracted, a mutual ratio Ψ is calculated, and a noise removing waveform is calculated based thereon. Based on the noise removing waveform, a pulse wave is detected, a pulse rate is calculated, a display wave form is calculated and an oxygen saturation is calculated. These are displayed through a display unit 11.

Claims

1. A device for measuring a light absorption material in blood, comprising:

light emitting means for emitting light, having a plurality of different wavelengths, onto a living tissue;

light receiving means for receiving light outputted from the light emitting means and transmitted through or reflected from the living tissue, the light receiving means outputting a signal corresponding to an intensity of the light transmitted through or reflected from the living tissue;

D.C./A.C. detecting means for obtaining a D.C. component and an A.C. component of a signal corresponding to each wavelength that is output from the light receiving means, respectively;

A.C. to D.C. ratio detecting means for obtaining an A.C. to D.C. ratio signal, which is a ratio of the A.C. component to the D.C. component for each wavelength calculated by the D.C./A.C. detecting means;

component extracting means for extracting a component from the A.C. to D.C. ratio signal having a predetermined frequency value, or a higher frequency value, for each wavelength which is obtained by the A.C. to D.C. ratio detecting means;

extracted component ratio detecting means for obtaining a ratio of extracted component signals for corresponding different wavelengths outputted from the light receiving means, which is extracted by the component extracting means; and

information detecting means for detecting information about a light absorption material in blood, based on the ratio detected by the extracted component ratio detecting means.

2. The device for measuring the light absorption material in blood according to claim 1, wherein the information detecting means detects the information about the light absorption material in blood based on a predetermined relationship among the ratio detected by the extracted component ratio detecting means and the A.C. to D.C. ratio signal detected by the A.C. to D.C. ratio detecting means, wherein an ideal signal is provided when the A.C. to D.C. ratio signal has no noise component.

3. The device for measuring a light absorption material in blood according to claim 2, further comprising:

pulse rate detecting means for detecting a pulse rate based on the ideal signal.

4. The device for measuring a light absorption material in blood according to claim 2, further comprising:

display means for displaying a waveform of the ideal signal.

5. The device for measuring the light absorption material in blood according to the claim 1, wherein said predetermined frequency value is substantially a pulsation frequency value of living tissue.

6. The device for measuring a light absorption material in blood according to claim 1, wherein the information about the light absorption material in blood is an oxygen saturation.

7. The device for measuring a light absorption material in blood according to claim 1, wherein two wavelengths are used as the different wavelengths.

8. A device for measuring a light absorption material in blood, comprising:

light emitting means for emitting light, having a plurality of different wavelengths, onto a living tissue;

light receiving means for receiving light outputted from the light emitting means and transmitted through or reflected from the living tissue, the light receiving means outputting a signal corresponding to an intensity of the light transmitted through or reflected from the living tissue;

D.C./A.C. detecting means for obtaining a D.C. component and an A.C. component of a signal corresponding to each wavelength that is output from the light receiving means;

A.C. to D.C. ratio detecting means for obtaining an A.C. to D.C. ratio signal, which is a ratio of the A.C. component to the D.C. component for each wavelength calculated by the D.C./A.C. detecting means;

noise condition deciding means for deciding at least whether a noise component included in the A.C. to D.C. ratio signal, around a predetermined frequency value or a higher frequency value, is large;

said noise condition detecting means comprising;

signal processing means for processing the A.C. to D.C. ratio signal for each wavelength which is obtained by the A.C. to D.C. ratio detecting means to detect information about a light absorption material in blood, said signal processing means comprising;

component extracting means for extracting a component from the A.C. to D.C. ratio signal having said predetermined frequency value or a higher frequency value for each wavelength which is obtained by the A.C. to D.C. ratio detecting means if the noise component for said predetermined frequency value or a higher frequency value, is large;

extracted component ratio detecting means for obtaining a ratio of extracted component signals for corresponding different wavelengths outputted from the light receiving means, which is extracted by the component extracting means; and

information detecting means for detecting information about a light absorption material in blood, based on the ratio detected by the extracted component ratio detecting means.

9. The device for measuring the light absorption material in blood according to claim 8, wherein the information detecting means detects the information about the light absorption material in blood based on a predetermined relationship among the ratio detected by the extracted component ratio detecting means and the A.C. to D.C. ratio signal detected by the A.C. to D.C. ratio detecting means, wherein an ideal signal is provided when the A.C. to D.C. ratio signal has no noise component.

10. The device for measuring a light absorption material in blood according to claim 9, further comprising:

pulse rate detecting means for detecting a pulse rate based on the ideal signal.

11. The device for measuring a light absorption material in blood according to claim 9, further comprising:

display means for displaying a wave form of the ideal signal.

12. The device for measuring a light absorption material in blood according to the claim 8, wherein said predetermined frequency value is substantially a pulsation frequency value of living tissue.

13. The device for measuring a light absorption material in blood according to claim 8, wherein the information about the light absorption material in blood is an oxygen saturation.

14. The device for measuring a light absorption material in blood according to claim 8, wherein two wavelengths are used as the different wavelengths.