Pulse wave detecting device and method therefor

• US 20060224054A1
• Filed: 09/23/2005
• Published: 10/05/2006
• Est. Priority Date: 03/30/2005
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Moriya, Akihisa, Suzuki, Takuji, Ouchi, Kazushige
• Granted Patent: US 7,470,235 B2
• Time in Patent Office: Days
• US Class Current: 600/310
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light

Abstract

A pulse wave measuring apparatus can determine an optimum combination of a pair of light-emitting element and light-receiving element out of plural light-emitting elements and plural light-receiving elements on a real time basis according to a difference of signal intensity of a pulse wave signal from the light-receiving element and always measure an stable pulse wave of a wrist artery robustly.

Claims

1. A measuring apparatus for detecting a pulse wave signal indicating a change in a blood flow in the blood vessel of a patient by using light, comprising:

a sensor module including a plurality of light-emitting elements to irradiate the blood vessel, and a plurality of light-receiving elements to receive reflected light as a pulse wave signal from the blood vessel, each element being attached on the surface of the patient;

a processor for light emission that causes the plural light-emitting elements to emit light one after another;

an autocorrelation value calculating processor that calculates autocorrelation values of respective pulse wave signals corresponding to respective combinations of the light-emitting elements, which have emitted light, and the light-receiving elements, which have received light, respectively; and

an optimum position identifying processor that selects a combination of a light-emitting element and a light-receiving element, which has outputted a pulse wave signal with a highest autocorrelation value among the respective autocorrelation values, as an optimum combination.

2. A measuring apparatus according to claim 1, wherein the autocorrelation value calculating processor slices waveforms of pulse wave signals in an arbitrary period from the pulse wave signals, respectively, and obtains an autocorrelation between the sliced waveforms and the pulse wave signals to thereby calculate autocorrelation values of the respective pulse wave signals.

3. A measuring apparatus according to claim 2, wherein the arbitrary period includes a pulse wave of at least one beat.

4. A measuring apparatus according to claim 1, wherein

the processor for light emission causes one light-emitting element to emit light,

the plurality of light-emitting elements receive reflected light based on the emitted light,

the optimum position identifying processor performs first selection for selecting a light-emitting element, which has a pulse wave signal with highest signal intensity among pulse wave signals from the plurality of light-receiving elements, as a light-receiving element of an optimum combination corresponding to the one light-emitting element, and

the autocorrelation value calculating processor calculates autocorrelation values of the respective pulse wave signals of the light-emitting element and the light-receiving element combined by the first selection.

5. A measuring apparatus according to claim 1, wherein the optimum position identifying processor extracts pulse wave signals, which have autocorrelation values equal to or higher than a predetermined threshold value among the respective autocorrelation values, and selects a pulse wave signal, which has a highest autocorrelation value, out of the extracted pulse wave signals.

6. A measuring apparatus according to claim 1, wherein, in selecting an optimum combination again after an optimum combination of a light-emitting element and a light-receiving element is determined by the optimum position identifying processor, the processor for light emission causes a light-emitting element near the light-emitting element selected as the light-emitting of the optimum combination.

7. A measuring apparatus according to claim 1, wherein

the plurality of light-emitting elements and the plurality of light-receiving elements are provided on a side of the sensor module attached to the surface of the organism,

the plurality of light-emitting elements are arranged in one row, and

the plurality of light-receiving elements are arranged in one row and in parallel to the plurality of light-emitting elements.

8. A measuring apparatus according to claim 1, wherein

the plurality of light-emitting elements and the plurality of light-receiving elements are provided on a side of the sensor module attached to the surface of the organism,

the plurality of light-emitting elements are arranged in one row in a horizontal direction, and

the plurality of light-receiving elements are arranged in one row in the horizontal direction, in parallel to the plural light-emitting elements, and in a state in which the plural light-receiving elements deviate in the horizontal direction with respect to the respective light-emitting elements.

9. A measuring apparatus according to claim 1, wherein

the plurality of light-emitting elements and the plurality of light-receiving elements are provided on a side of the sensor module attached to the surface of the organism, and

the plurality of light-emitting elements and the plurality of light-receiving elements are arranged alternately in one row in a horizontal direction and the row in the horizontal direction is arranged in plurality of stages in a vertical direction.

10. The measuring apparatus according to claim 1, wherein the sensor module is attached to a wrist or a neck of the patient.

11. A measuring apparatus according to claim 1, wherein

the sensor module is attached to an ankle of the patient, and

the sensor module is curved to fit a shape of the ankle.

12. A measuring method of detecting a pulse wave signal indicating a change in a blood flow in the blood vessel of a patient by using light, comprising:

causing the plurality of light-emitting elements provided in the sensor module to emit light one after another;

calculating autocorrelation values of respective pulse wave signals corresponding to respective combinations of the light-emitting elements, which have emitted light, and the light-receiving elements, which have received light, respectively; and

selecting a combination of a light-emitting element and a light-receiving element, which has outputted a pulse wave signal with a highest autocorrelation value among the respective autocorrelation values, as an optimum combination.

13. A program that realizes, with a computer, a measuring method of detecting a pulse wave signal indicating a change in a blood flow in the blood vessel of patient by using light, the program realizing:

a light-emitting function of causing the plurality of light-emitting elements provided in the sensor module to emit light one after another;

an input function of inputting respective pulse wave signals outputted from the plural light-emitting elements provided in the sensor module;

an autocorrelation value calculating function of calculating autocorrelation values of respective pulse wave signals corresponding to respective combinations of the light-emitting elements, which have emitted light, and the light-receiving elements, which have received light, respectively; and

an optimum position identifying function of selecting a combination of a light-emitting element and a light-receiving element, which has outputted a pulse wave signal with a highest autocorrelation value among the respective autocorrelation values, as an optimum combination.