JP2016146958A - Blood pressure measuring device and blood pressure measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of blood pressure measurement by taking blood viscosity into account.SOLUTION: A blood pressure measuring device 10 includes a light emitting part 52-1 and 2 for irradiating a user 2 with irradiation light of a first wavelength and irradiation light of a second wavelength, and a light receiving part 54 for receiving light that reflects or transmits in a living body of the user 2. A blood vessel resistance calculation part 156 in a calculation part 150 calculates a blood flow rate and blood vessel resistance based on a light receiving result of the light receiving part 54 following the irradiation of the irradiation light of the first wavelength and a light receiving result of the light receiving part 54 following the irradiation of the irradiation light of the second wavelength, and calculates a blood pressure from the blood flow rate and the blood vessel resistance.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a blood pressure measuring device that measures blood pressure using light.

  At present, development of a blood pressure measuring device using ultrasonic waves or light is being promoted as a new method, not a pressure type using a cuff that is generally spread. For example, in Patent Document 1, blood flow velocity is detected using ultrasonic waves, volume pulse wave is detected using light, blood flow volume obtained from blood flow velocity, blood vessel resistance obtained from volume pulse wave, A method for measuring blood pressure is disclosed.

JP 2004-154231 A

  Patent Document 1 describes that vascular resistance is a value determined by blood viscosity and arterial diameter. However, there is no mention of how blood viscosity is taken into account when calculating vascular resistance. For this reason, blood vessel resistance is not appropriate, and blood pressure measurement accuracy may be reduced.

  The present invention has been made in view of such circumstances, and an object thereof is to improve blood pressure measurement accuracy in consideration of blood viscosity.

  According to a first aspect of the present invention, there is provided a light emitting unit that irradiates a living body with irradiation light having a first wavelength and irradiation light with a second wavelength, and light reception that receives light reflected or transmitted in the living body. Blood flow volume and vascular resistance are calculated based on the light reception result of the light receiving unit accompanying irradiation of the irradiation light of the first wavelength and the light reception result of the light receiving unit accompanying irradiation of the irradiation light of the second wavelength And a blood pressure measuring device including a calculation unit that calculates blood pressure from the blood flow volume and the vascular resistance.

  As another form, an apparatus comprising a light emitting unit that irradiates the body with irradiation light of the first wavelength and irradiation light of the second wavelength, and a light receiving unit that receives light reflected or transmitted in the living body, Calculating a blood flow volume and a vascular resistance based on a light reception result of the light receiving unit accompanying irradiation of the irradiation light of the first wavelength and a light reception result of the light receiving unit accompanying irradiation of the irradiation light of the second wavelength; The blood pressure measurement method may be configured to calculate blood pressure from the blood flow volume and the vascular resistance.

  According to the first invention and another embodiment, blood is received based on the light reception result of the light receiving unit accompanying the irradiation of the irradiation light of the first wavelength on the living body and the light reception result of the light receiving unit accompanying the irradiation of the irradiation light of the second wavelength. The flow rate and vascular resistance are calculated, and the blood pressure is calculated. As will be described later, the blood concentration determined by the result of light received by changing the wavelength is proportional to the blood viscosity, and the blood viscosity correlates with the vascular resistance. Therefore, the vascular resistance can be calculated according to the blood viscosity, and the blood pressure can be calculated using the vascular resistance, so that the blood pressure can be measured with high accuracy.

  According to a second aspect of the present invention, the calculation unit receives the light reception results of the light receiving unit during the contraction period and the expansion period accompanying the irradiation of the first wavelength, and the contraction period and the expansion period of the light receiving unit during the irradiation of the second wavelength. The blood pressure measurement device according to the first aspect of the present invention executes calculation of a blood concentration from the received light results of and calculating the vascular resistance using the blood concentration.

  According to the second invention, the blood concentration is calculated based on the light reception result of the first wavelength in the diastole and the systole and the light reception result of the second wavelength in the diastole and the systole, and the vascular resistance is calculated from the blood concentration. Can be calculated.

  According to a third aspect of the present invention, the light emitting unit includes a first light emitting unit that irradiates the irradiation light having the first wavelength, and a second light emitting unit that irradiates the irradiation light having the second wavelength. The first light emitting unit and the second light emitting unit are positioned such that the distance between the first light emitting unit and the light receiving unit satisfies the same condition as the distance between the second light emitting unit and the light receiving unit. 1 is a blood pressure measurement device according to the first or second invention;

  According to the third aspect, it is possible to irradiate the irradiation light of the first wavelength and the irradiation light of the second wavelength by the separate light emitting units whose distance from the light receiving unit satisfies the same condition.

  A fourth invention is the blood pressure measurement device according to any one of the first to third inventions, wherein the calculation unit causes the light emitting unit to sequentially perform the irradiation of the first wavelength and the irradiation of the second wavelength. is there.

  According to the fourth invention, the blood flow volume and the vascular resistance are calculated from the light reception result of the light receiving unit obtained by sequentially performing the irradiation of the irradiation light of the first wavelength and the irradiation of the irradiation light of the second wavelength. Can be calculated.

  In a fifth aspect of the invention, the first wavelength belongs to a wavelength range of 800 ± 20 [nm], and the second wavelength belongs to a wavelength range of 976 ± 20 [nm]. This is a blood pressure measuring device. The sixth invention is any one of the first to fourth aspects, wherein the first wavelength belongs to a wavelength range of 800 ± 20 [nm] and the second wavelength belongs to a wavelength range of 1196 ± 20 [nm]. This is a blood pressure measurement device according to the invention.

  According to the fifth or sixth invention, a wavelength having a relatively high absorbance due to hemoglobin can be set as the first wavelength, and a wavelength having a relatively high absorbance due to water can be set as the second wavelength.

  According to a seventh invention, the blood pressure according to any one of the first to sixth inventions, wherein the calculation unit frequency-analyzes the light received by the light-receiving unit and calculates the blood flow volume using a result of the frequency analysis. It is a measuring device.

  According to the seventh aspect of the invention, the blood flow rate can be calculated using, for example, a so-called laser Doppler technique.

The external view which shows the example of whole structure of a blood-pressure measuring apparatus. Diagram explaining the propagation of light in a living body The figure which shows an example of a volume pulse wave. The block diagram which shows the function structural example of a blood-pressure measurement apparatus. The flowchart which shows the flow of a blood-pressure measurement process. The figure which shows the apparatus structural example of the blood-pressure measuring apparatus in a modification.

  Hereinafter, an embodiment for implementing the blood pressure measurement device and the like of the present invention will be described. It should be noted that the present invention is not limited to the embodiments described below, and modes to which the present invention can be applied are not limited to the following embodiments. In the description of the drawings, the same parts are denoted by the same reference numerals.

[overall structure]
FIG. 1 is an external view showing an example of the overall configuration of a blood pressure measurement device 10 of the present embodiment. As shown in FIG. 1, the blood pressure measurement device 10 is configured as a wristwatch-type wearable device, for example, and is attached to a body part such as an arm, a leg, or a neck of a user 2 with a band 14 provided in a main body case 12. used.

  An operation switch 16, a touch panel 18, and a speaker 19 are provided on the surface of the main body case 12 (the surface facing outward when the user 2 is worn). The user 2 and the like can input various operations such as a blood pressure measurement start operation and a measurement end operation using the operation switch 16 and the touch panel 18. In addition, during the measurement, a notification sound for starting and ending the measurement, a guidance voice relating to the measurement, and the like are appropriately output from the speaker 19, and a measurement guidance screen and the like are displayed on the touch panel 18 as appropriate. .

  On the side surface of the main body case 12, a communication device 20 to which a wired cable for communicating with an external device can be attached and detached, and a reader / writer 24 for reading and writing data to and from the memory card 22 are provided. Includes a built-in rechargeable battery 26 and a control board 30. And, on the back side of the main body case 12 (the surface that comes into contact with the skin of the user 2 when worn on the user 2), the irradiation light for blood pressure measurement or the like is irradiated into the living body of the user 2 and received. A sensor module 50 is provided.

  The communication device 20 is realized by a wireless communication module and an antenna if the communication device 20 is configured to wirelessly communicate with an external device. The memory card 22 is a detachable nonvolatile memory that can rewrite data. As the memory card 22, a rewritable nonvolatile memory such as a strong derivative memory (FeRAM: Ferroelectric Random Access Memory) or a magnetoresistive memory (MRAM) can be used in addition to a flash memory.

  The charging method for the built-in battery 26 can be set as appropriate. For example, an electrical contact may be separately provided on the back side of the main body case 12, set in a cradle connected to a household power supply, and energized and charged via the cradle via the electrical contact, or a non-contact wireless Charging may be used.

  A CPU (Central Processing Unit) 32, a main memory 34, a measurement data memory 36, and a sensor module controller 40 are mounted on the control board 30. In addition, electronic parts such as a touch panel controller IC (Integrated Circuit), a power management IC, and an image processing IC are appropriately mounted.

  The main memory 34 is a storage medium that can store programs and initial setting data, and can store calculation values of the CPU 32. It is realized by appropriately using RAM (Random Access Memory), ROM (Read Only Memory), flash memory, and the like. The program and initial setting data may be stored in the memory card 22.

  The measurement data memory 36 is a rewritable nonvolatile memory and is a storage medium for storing blood pressure measurement results. As the measurement data memory 36, a rewritable nonvolatile memory such as a strong derivative memory (FeRAM) or a magnetoresistive memory (MRAM) can be used in addition to a flash memory. The measurement data may be stored in the memory card 22.

  The sensor module controller 40 is an IC or a circuit that performs the irradiation function of the irradiation light by the sensor module 50 and the light reception function of the light (transmission light) transmitted through the living body of the user 2 or the reflected light (reflection light). Have The sensor module controller 40 includes a light emission controller unit 42 formed of an IC or a circuit that individually controls light emission of the two light emitting units 52 (52-1, 52-2) included in the sensor module 50, and a light receiving unit included in the sensor module 50. And a light receiving controller unit 44 composed of an IC and a circuit for controlling the light received by 54.

  The sensor module 50 is arranged such that the light emitting surface 52 is exposed on the back surface of the main body case 12 and the light receiving surface 541 is exposed on the back surface of the main body case 12. A light receiving unit 54.

The two light emitting units 52 are each composed of a light emitting element that emits irradiation light having different wavelengths. In the present embodiment, the first light emitting unit 52-1 which is one of the light emitting units 52 irradiates the irradiation light having the first wavelength λ ₁ belonging to the wavelength range 800 ± 20 [nm]. 800 [nm] is a wavelength at which the absorptions of oxygenated hemoglobin and deoxygenated hemoglobin are approximately equal. For example, the first light emitting unit 52-1 can be realized by using a laser light source that irradiates (emits) a single wavelength laser beam within a wavelength range of 800 ± 20 [nm]. In addition, the second light emitting unit 52-2 which is the other light emitting unit 52 irradiates the irradiation light of the second wavelength λ ₂ belonging to the wavelength range 976 ± 20 [nm] including the absorption peak of water. Alternatively, the second light emitting unit 52-2, a wavelength belonging to a wavelength region including another absorption peak of water 1196 ± 20 [nm] and the second wavelength lambda _2, the second wavelength lambda ₂ of the irradiation light May be irradiated. For example, the 2nd light emission part 52-2 is realizable using the laser light source which irradiates the laser beam of the single wavelength in any one wavelength range of 976 ± 20 [nm] and 1196 ± 20 [nm]. .

Although details will be described later, in this embodiment, the blood concentration is calculated using the absorbance of hemoglobin and the absorbance of water at each of the first wavelength λ ₁ and the second wavelength λ ₂ . Therefore, as described above, _{one of} the first wavelength λ ₁ and the second wavelength λ ₂ is preferably a wavelength corresponding to the absorption wavelength of hemoglobin, and the other is a wavelength corresponding to the absorption wavelength of water.

  The light receiving unit 54 receives transmitted light and reflected light of irradiated light, and outputs a signal corresponding to the amount of received light. For example, it is realized by an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS).

  The first light emitting unit 52-1, the second light emitting unit 52-2, and the light receiving unit 54 are target blood vessels (for example, radial artery on the wrist of the user 2) that run under the attachment site of the blood pressure measurement device 10. Is positioned and disposed within the back surface of the main body case 12 according to the assumed position.

  Here, with reference to FIG. 2, focusing on the first light emitting unit 52-1, the positional relationship between the light receiving unit 54 and the target blood vessel 7 will be described. FIG. 2 is a diagram for explaining the propagation of light in the living body, and shows a cross section along the depth direction under the mounting site where the user 2 is covered with the sensor module 50. The irradiation light emitted from the first light emitting unit 52-1 enters the living body from the skin surface and diffusely reflects, and part of the light reaches the light receiving unit 54. The propagation path of the light has a so-called banana shape (region sandwiched between two arcs), and the width in the depth direction is the widest near the center. The depth (reachable depth) D of this propagation path is shallower as the interval W between the first light emitting unit 52-1 and the light receiving unit 54 is smaller, and becomes deeper as the interval W is larger.

  In order to increase the accuracy of blood pressure measurement, it is desirable that more light that has passed through the target blood vessel 7 is received by the light receiving unit 54. Therefore, when the vicinity of the center where the width in the depth direction of the light propagation path from the first light emitting unit 52-1 to the light receiving unit 54 is the widest matches the position where the target blood vessel 7 travels. Good. From this, the target blood vessel 7 is positioned approximately at the center between the first light emitting unit 52-1 and the light receiving unit 54, and the interval W is a distance corresponding to the depth D of the target blood vessel 7. The positions of the first light emitting unit 52-1 and the light receiving unit 54 are determined. For example, assuming that the depth D of the target blood vessel 7 is about 3 [mm], the interval W can be about 5 to 6 [mm].

  The position of the second light emitting unit 52-2 is similarly determined. That is, the second light emitting unit 52-2 is arranged at a position where the positional relationship between the light receiving unit 54 and the target blood vessel 7 is the same as that described with reference to FIG. 2 for the first light emitting unit 52-1. Established. Specifically, the second light emitting unit 52-2 is spaced from the light receiving unit 54 by a distance W, for example, arranged side by side in the vicinity of the first light emitting unit 52-1, as shown in FIG. Is done.

[principle]
Prior to the measurement, the blood pressure measurement device 10 is fixed with the band 14 so that the back surface of the main body case 12 is in close contact with the skin of the user 2. As a result, the light emitting surface 521 of each of the light emitting units 50-1 and 502 and the light receiving surface 541 of the light receiving unit 54 can be brought into close contact with the skin, and the reflection of the irradiated light on the skin surface and the scattering of the tissue near the skin surface. Such a factor that lowers the measurement accuracy can be suppressed.

(A) blood pressure calculation pressure P _R of, as shown in equation (1), and the blood flow Q, represented by the product of the vascular resistance R.

(B) Blood flow rate Q
The blood flow rate Q is calculated using a laser Doppler method. Specifically, frequency analysis processing by fast Fourier transform (FFT) is performed on the light reception signal from the light receiving unit 54 (a signal representing a temporal change in the amount of received light) to obtain a power spectrum (frequency spectrum). P (f) is calculated. Then, according to the equation (2), the blood flow rate Q is calculated using the calculated power spectrum P (f). In Equation (2), K _Q is a predetermined constant, f ₁ and f ₂ are the cutoff frequencies of the bandpass filter, and <I ² > is the root mean square of the intensity of the received light.

(C) Vascular resistance R
In calculating the vascular resistance R, first, a volume pulse wave is detected in order to specify the timing of the systole and diastole during one heartbeat. The blood vessel repeatedly contracts and dilates due to the pulsation of the heart, and the blood flow in the blood vessel also fluctuates accordingly. Therefore, if the irradiation light is continuously irradiated to a certain part of the blood vessel, the amount of light passing through the blood vessel changes due to the change in blood flow. FIG. 3 is a diagram illustrating an example of a volume pulse wave. As shown in FIG. 3, the volume pulse wave is a periodic function whose period is one heartbeat period of the heart, and the timing of the systole and the diastole can be specified from the periodicity. The received light signal from the light receiving unit 54 may be subjected to frequency filtering processing or smoothing processing, and then the volume pulse wave may be detected.

More specifically, the irradiation light of the first wavelength λ ₁ is emitted from the first light emitting unit 52-1. Then, to detect the volume pulse wave from the change of the amount of light received by the light receiving portion 54 due to the irradiation of the first wavelength lambda ₁ of the illumination light, to identify the timing of the systolic and diastolic blood vessels in one heartbeat. If identifying each timing, the amount of light received by the light receiving portion 54 in the systole and the first wavelength lambda ₁ of systole detected light, as a diastolic detected light intensity of the first wavelength lambda ₁ to the light receiving amount of the light receiving portion 54 in the diastole You can get it.

In addition, irradiation light of the second wavelength λ ₂ is emitted from the second light emitting unit 52-2. Then, to detect the volume pulse wave from variation of the amount of light received by the light receiving portion 54 due to the irradiation of the second wavelength lambda ₂ of the irradiation light, to identify the timing of the systolic and diastolic blood vessels in one heartbeat. If identifying each timing, the amount of light received by the light receiving portion 54 in the systole and the second wavelength lambda ₂ of the systolic detected light, as a diastolic detected light receiving amount of the second wavelength lambda ₂ of the light receiving portion 54 in the diastole You can get it.

As described below, the hemoglobin concentration (blood concentration) can be obtained from the systolic detection light amount and the diastolic detection light amount acquired at two different wavelengths λ ₁ and λ ₂ as described above.

First, when the diastole detection light quantity of the first wavelength λ ₁ is I _r (λ ₁ ) and the systolic detection light quantity of the first wavelength λ ₁ is I _r (λ ₁ ) −ΔI _r (λ ₁ ), the first wavelength diastolic absorbance _{A dia} at lambda ₁ (lambda ₁₎ in the equation (3), systolic absorbance _{A sys} at the first wavelength lambda ₁ (lambda ₁₎ can be represented respectively by formula (4). Second diastolic at the wavelength lambda ₂ absorbance _{A dia} (lambda ₂₎ and is not shown for systolic absorbance _{A sys} (λ _2), second wavelength lambda ₂ of the diastolic detected light intensity _{I r} (lambda ₂₎ and contraction It can be expressed by a similar expression using the initial detected light quantity I _r (λ ₂ ) −ΔI _r (λ ₂ ).

Equation (3), in _{(4), A dia} diastolic _{absorbance, A sys} systolic absorbance, _{I i} is the amount of incident light, _{I r} diastolic detected light _{intensity, I} r -.DELTA.I _r systole detected light, E _a is the absorption coefficient of the arterial blood [dL / g / mm], E v is the absorption coefficient of the venous blood [dL / g / mm], the absorption coefficient of _{E m} is other tissues [dL / g / mm], C a is the arterial blood concentration [g / dL] of, _{C v} concentration of venous blood [g / dL], the concentration of _{C m} is other tissue [g / dL], _{D a} is the optical path length of the diastolic arterial blood [mm], _{D a} + ΔD _a represents the optical path length [mm] of arterial blood during systole, D _v represents the optical path length [mm] of venous blood, D _m represents the optical path length [mm] of other tissues, and S represents the degree of attenuation due to scattering.

From Equation (3) and Equation (4), the absorbance difference between the systolic absorbance A _sys (λ ₁ ) and the diastolic absorbance A _dia (λ ₁ ) at the first wavelength λ ₁ is expressed by Equation (5). Can do. Similarly, the difference in absorbance between the systolic absorbance A _sys (λ ₂ ) and the diastolic absorbance A _dia (λ ₂ ) at the second wavelength λ ₂ can also be expressed by Expression (6).

Here, the absorbance of arterial blood at the first wavelength lambda ₁ is the absorbance of hemoglobin at the first wavelength lambda ₁ and (absorption _{coefficient) E Hb [dL / g /} mm], the absorbance of water (the absorption _coefficient) E w [dL / g / mm] and can be expressed by the equation (7). Similarly, the absorbance of arterial blood in the second wavelength lambda ₂ is expressed by Equation (8) using _the absorbance E _w absorbance E _Hb and water of hemoglobin in the second wavelength lambda _2. In the formulas (7) and (8), C _Hb represents the hemoglobin concentration [g / dL], and C _w represents the water concentration [g / dL].

Therefore, Expression (9) is established from Expression (5) and Expression (7). Similarly, Expression (10) is established from Expression (6) and Expression (8).

E _Hb and E _w are known because they are physical property values. However, E _Hb and E _w may be experimentally obtained for each wavelength, _{tabulated in} advance, and read out for use. Therefore, using the diastolic detection light amount and the systolic detection light amount of the first wavelength λ ₁ obtained by detecting the volume pulse wave, and the diastolic detection light amount and the systolic detection light amount of the second wavelength λ ₂ , the equation (9 ) And (10) can be used to determine the values of C _Hb ΔD _a and C _w ΔD _a . Further, the sum of C _Hb and C _w is about 100 [g / dL], and since Expression (11) is established, ΔD _a can be obtained. Therefore, C _Hb and C _w are obtained.

After _obtaining C _Hb and C _w , the blood concentration is calculated according to equation (12). Alternatively, the blood concentration may be calculated according to equation (13).

  The blood concentration calculated as described above is strictly a value proportional to the blood concentration, but is proportional to the blood viscosity. The blood viscosity correlates with the vascular resistance R. Therefore, in this embodiment, the vascular resistance R is calculated from the calculated blood concentration. For example, the correspondence between the blood concentration and the vascular resistance R is experimentally obtained and tabulated in advance (vascular resistance correspondence table). At the time of measuring blood pressure, the blood concentration is calculated as described above, and the vascular resistance R is obtained by referring to the vascular resistance correspondence table. The configuration may be such that the vascular resistance R corresponding to the blood concentration calculated from the vascular resistance correspondence table is read out, or the vascular resistance R set in the vascular resistance correspondence table is calculated by interpolation processing based on the calculated blood concentration. May be. In addition, the relationship between the blood concentration and the vascular resistance R is not limited to a table, and a relational expression between the blood concentration and the vascular resistance R may be set. And it is good also as a structure which calculates the vascular resistance R from the set relational expression using the calculated blood concentration.

[Function configuration]
FIG. 4 is a block diagram illustrating a main functional configuration example of the blood pressure measurement device 10 according to the present embodiment. As shown in FIG. 4, the blood pressure measurement device 10 includes a sensor module 50, an operation unit 110, a display unit 120, a sound output unit 130, a communication unit 140, a calculation unit 150, and a storage unit 160. .

  The operation unit 110 is realized by various switches such as a button switch, a lever switch, a dial switch, and an input device such as a touch panel, and outputs an operation signal corresponding to various operation inputs such as a measurement start operation to the calculation unit 150. To do. In FIG. 1, the operation switch 16 and the touch panel 18 correspond to this.

  The display unit 120 is realized by a display device such as an LCD (Liquid Crystal Display) or an EL display (Electroluminescence display), and displays various screens based on a display signal input from the calculation unit 150. In FIG. 1, the touch panel 18 corresponds to this. The display unit 120 displays a blood pressure measurement result and the like.

  The sound output unit 130 is a sound output device such as a speaker, and outputs various sounds based on the sound signal from the calculation unit 150. In FIG. 1, the speaker 19 corresponds to this. The sound output unit 130 appropriately outputs a notification sound at the start or end of measurement.

  The communication unit 140 is a communication device for transmitting / receiving information used inside the device to / from an external information processing device. In FIG. 1, the communication device 20 corresponds to this. As a communication method of the communication unit 140, a wired connection via a cable compliant with a predetermined communication standard, a connection connected via an intermediate device also used as a charger called a cradle, and wireless using wireless communication Various methods such as a connection type can be applied.

  The calculation unit 150 is a control device and a calculation device that comprehensively controls each unit of the blood pressure measurement device 10, and includes a microprocessor such as a CPU and a GPU (Graphic Processing Unit), an ASIC (Application Specific Integrated Circuit), and an FPGA (Field -Programmable Gate Array), IC (Integrated Circuit) memory, etc. In FIG. 1, the control board 30 corresponds to this. The calculation unit 150 includes a light emission control unit 151, a light reception control unit 152, a switching control unit 153, a blood flow rate calculation unit 154, a volume pulse wave detection unit 155, a vascular resistance calculation unit 156, and a blood pressure calculation unit 158. Including.

  The light emission control unit 151 selectively causes one of the first light emitting unit 52-1 and the second light emitting unit 52-2 to emit light. Specifically, the emission start and emission end of irradiation light, the intensity of irradiation light, and the like are controlled.

  The light reception control unit 152 controls light reception by the light reception unit 54 and performs filtering processing such as noise removal or conversion processing to a digital signal on a signal (a signal corresponding to the amount of received light) input from the light reception unit 54. Do. In the present specification, the light reception result of the light receiving unit 54 (which is a light reception signal, which can also be referred to as a detected light amount) may be the signal itself input from the light receiving unit 54 or after signal processing by the light reception control unit 152. It is good also as this signal. This is because it can be said to be a substantially equivalent signal.

  The switching control unit 153 performs control to switch the target of light emission control by the light emission control unit 151 to one of the first light emitting unit 52-1 and the second light emitting unit 52-2.

  The blood flow rate calculation unit 154 calculates the blood flow rate Q based on the light reception signal of the light receiving unit 54. That is, frequency analysis processing such as FFT is performed on the light reception signal from the light receiving unit 54 to calculate a power spectrum (frequency spectrum) P (f). Then, according to the equation (3), the blood flow rate Q is calculated using the power spectrum P (f). The calculated blood flow Q is stored in the storage unit 160 as blood flow data 163.

The volume pulse wave detector 155 detects the volume pulse wave based on the light reception signal from the light receiver 54. Specifically, the first light emitting unit 52-1 and the second light emitting unit 52-2 are caused to emit light in order via the light emission control unit 151, and the amount of light received by the light receiving unit 54 (the intensity of the light reception signal) each time. Is detected as a volume pulse wave. Thus, the volume pulse wave detected for each of the wavelengths λ ₁ and λ ₂ is stored in the storage unit 160 as volume pulse wave data 164.

The vascular resistance calculation unit 156 acquires the diastolic detection light amount and the systolic detection light amount of the first wavelength λ _{1 and} the diastolic detection light amount and the systolic detection light amount of the second wavelength λ ₂ , and the blood concentration calculation unit 157 The vascular resistance R is calculated from the blood concentration calculated using the diastolic detection light amount and the systolic detection light amount of the wavelengths λ ₁ and λ ₂ . The calculated blood concentration is stored in the storage unit 160 as blood concentration data 165, and the vascular resistance R is stored in the storage unit 160 as vascular resistance data 166. Note that the diastole detection light amount and the systolic detection light amount may be acquired not in the waveform for one heartbeat but in the waveform for a plurality of beats, and the blood concentration may be calculated using the average value.

Blood pressure calculation unit 158 calculates the blood pressure P _R from the blood flow rate Q and the vascular resistance R. Calculated blood pressure P _R is, for example associated with the measurement time, is accumulated and stored in the storage unit 160 as blood pressure data 167.

  The storage unit 160 is realized by various IC memories such as ROM, flash ROM, and RAM, and a storage medium such as a hard disk, and operates the blood pressure measurement device 10 to realize various functions provided in the blood pressure measurement device 10. Program, data used during execution of the program, processing results, and the like are stored. In FIG. 1, the main memory 34, the measurement data memory 36, and the memory card 22 mounted on the control board 30 correspond to this.

  In the storage unit 160, the calculation unit 150 includes a light emission control unit 151, a light reception control unit 152, a switching control unit 153, a blood flow rate calculation unit 154, a volume pulse wave detection unit 155, a vascular resistance calculation unit 156, and a blood pressure calculation unit 158. The blood pressure measurement program 161 for performing the blood pressure measurement process (see FIG. 5) and the vascular resistance correspondence table 162 are stored in advance. In the blood vessel resistance correspondence table 162, as described above, a correspondence relationship between the blood concentration and the blood vessel resistance R obtained by performing an experiment in advance is set. Further, the blood flow data 163, volume pulse wave data 164, blood concentration data 165, blood vessel resistance data 166, and blood pressure data 167 are stored in the storage unit 160 in the course of blood pressure measurement processing.

[Process flow]
FIG. 5 is a flowchart showing the flow of blood pressure measurement processing. Note that the processing described here can be realized by the calculation unit 150 reading and executing the blood pressure measurement program 161 from the storage unit 160. This blood pressure measurement process is started when the blood pressure measurement device 10 is attached to the body of the user 2 and a predetermined measurement start operation is input.

In this blood pressure measurement process, first, the switching control unit 153 initially sets the target of light emission control by the light emission control unit 151 in the first light emitting unit 52-1 (step S <b> 1). With this control, the light emission control unit 151 causes the first light emitting unit 52-1 to emit light and starts irradiation with the irradiation light of the first wavelength λ ₁ , and the light reception control unit 152 causes the light receiving unit 54 to receive light (step) S3). Then, the volume pulse wave detection unit 155 detects the volume pulse wave based on the light reception signal from the light receiving unit 54 and specifies the timing of the systole and the diastole in one heartbeat (step S5).

Next, the switching control unit 153 switches the target of the light emission control by the light emission control unit 151 to the second light emitting unit 52-2 (step S7). The control here, the light emission control unit 151 is a second light-emitting portion 52-2 starts irradiation of the second wavelength lambda ₂ of the irradiating light to emit light, the light reception control unit 152 causes the light to the light receiving unit 54 (step S9). Then, the volume pulse wave detection unit 155 detects the volume pulse wave based on the light reception signal from the light receiving unit 54 and specifies the timing of the systole and the diastole in one heartbeat (step S11).

Next, vascular resistance calculating section 156, the amount of light received by the light receiving portion 54 in a particular systolic and first wavelength lambda ₁ systolic detected light in the step S5, the first wavelength light reception amount of the light receiving portion 54 in the diastole acquires as diastolic detected light intensity of lambda ₁ (step S13), and the second wavelength lambda ₂ of the systolic detected light amount of received light of the light receiving portion 54 in a particular systolic at step S11, the light receiving portion 54 in the diastole acquires received light amount as the second wavelength lambda ₂ of the diastolic detected light (step S15).

Subsequently, the blood concentration calculation unit 157 detects the systolic detection light amount and diastole detection light amount of the first wavelength λ ₁ acquired in step S13 and the systolic detection light amount and diastole detection of the second wavelength λ ₂ acquired in step S15. The blood concentration is calculated using the light amount (step S17). Specifically, Equation (9), from (10) _{C Hb} [Delta] D _a, obtains a _{C w} [Delta] D _a, obtaining a _C Hb, _{C w} from the relation of formula (11). Then, the blood concentration is calculated according to equation (12). The blood concentration may be calculated according to equation (13). Thereafter, the vascular resistance calculation unit 156 refers to the vascular resistance correspondence table 162 and calculates the vascular resistance R from the blood concentration calculated in step S17 (step S19).

If the vascular resistance R is calculated, the switching control unit 153 switches the target of light emission control by the light emission control unit 151 to the first light emitting unit 52-1 (step S 21). With this control, the light emission control unit 151 causes the first light emitting unit 52-1 to emit light and starts irradiation with the irradiation light of the first wavelength λ ₁ , and the light reception control unit 152 causes the light receiving unit 54 to receive light (step) S23). Note that the switching of the light emitting unit 52 is not necessarily performed here, and by continuing the irradiation of the irradiation light by the second light emitting unit 52-2 started in step S9, the light reception result is continued in steps S25 to S25. You may use for calculation of blood flow volume and blood pressure calculation in S31.

  That is, in step S25, the blood flow rate calculation unit 154 performs a frequency analysis process such as FFT on the light reception signal from the light reception unit 54 to calculate the power spectrum P (f). Then, the blood flow rate calculation unit 154 calculates the blood flow rate Q using the power spectrum P (f) calculated in step S25 according to the equation (2) (step S27).

Then, blood pressure calculation unit 158, using the blood flow Q calculated at step S27, and the vascular resistance R calculated in step S19, calculates the blood pressure _{P R} in accordance with equation (1) (step S29). Then, the display unit 120 displays the calculated blood pressure _{P R,} and stores in the storage unit 160 (step S31).

  Thereafter, until the blood pressure measurement process is completed (step S33: NO), the process returns to step S25 and the above process is repeated to continuously measure the blood pressure. When the measurement end operation is input (step S33: YES), this process ends.

As described above, according to the blood pressure measurement device 10 of the present embodiment, the light reception result of the light receiving unit 54 associated with the irradiation of the irradiation light of the first wavelength λ _{1 and} the irradiation of the irradiation light of the second wavelength λ _2. The blood concentration can be calculated based on the light reception result of the light receiving unit 54. The blood vessel resistance R can be calculated from the blood concentration by referring to the blood vessel resistance correspondence table 162 in which the correspondence between the blood concentration and the blood vessel resistance R is set. Therefore, the vascular resistance can be calculated according to the blood viscosity, and the blood pressure can be calculated using the vascular resistance, so that the blood pressure can be measured with high accuracy.

In the embodiment described above, the first light-emitting unit 52-1 for irradiating a first wavelength lambda ₁ of the irradiated light, and a second light-emitting unit 52-2 for irradiating the second wavelength lambda ₂ of the irradiation light Although the configuration of the provided sensor module 50 has been described, the number of light emitting units is not limited to two and may be one. For example, it is also possible to provide one light emitting unit that emits irradiation light (near infrared light) in a wavelength range including the first wavelength λ ₁ and the second wavelength λ _{2 so} that the light receiving unit receives light through a spectral filter. Good. Specifically, using a spectral filter which variably settable the center wavelength of the transmission wavelength range, the center wavelength of the transmission wavelength range is set to a first wavelength range of lambda _1, or the center wavelength of the transmission wavelength is a You may make it set to the wavelength range of 2 wavelengths (lambda) ₂ .

  In the above-described embodiment, the blood pressure measurement device 10 has been described as a wristwatch-type electronic device, but may have another form. For example, an electronic apparatus having a device configuration in which the probe and the main body device are separately connected for communication may be used.

  FIG. 6 is a diagram illustrating a device configuration example of the blood pressure measurement device 10b according to the present modification. The blood pressure measurement device 10b shown in FIG. 6 includes an optical probe 60, a main body device 70, a video monitor 80, and a keyboard 90. The main unit 70 may include a video monitor 80 and a keyboard 90.

The optical probe 60 is a thin flat pad type that can be affixed to a wrist or the like that is a measurement site of the user 2, and is used by being affixed and fixed to the measurement site of the user 2. The optical probe 60 includes a first light emitting unit 52-1, a second light emitting unit 52-2, and a light receiving unit 54, and the first probe is similar to the blood pressure measuring device 10 of the above embodiment. The light emitting surface 521 of each of the light emitting unit 52-1 and the second light emitting unit 52-2 and the light receiving surface 541 of the light receiving unit 54 are fixed to the user 2 so as to be in close contact with the skin surface of the user 2. Then, the optical probe 60 selectively causes one of the first light emitting unit 52-1 and the second light emitting unit 52-2 to emit light according to the light emission control signal from the main body device 70, so that the first wavelength λ ₁ or While irradiating with irradiation light of the second wavelength λ _2, a light reception signal (light reception amount) by the light receiving unit 54 is output to the main body device 70. The optical probe 60 may be a pen type that is not a pad type that can be affixed but is held by the operator with a hand and applied to the measurement site of the user 2.

  The main unit 70 includes various microprocessors such as CPUs, GPUs, and DSPs (Digital Signal Processors), ASICs and electronic circuits, various IC memories such as VRAMs, RAMs, and ROMs, information storage media such as hard disks, and data transmission / reception between external devices. Is realized by an interface IC, a connection terminal, a power supply circuit, and the like. The main body device 70 has the functions of the calculation unit 150, the storage unit 160, and the communication unit 140 illustrated in FIG.

  The main body device 70 and the optical probe 60 are connected by wire. The main body device 70 performs light measurement using the optical probe 60 to measure (calculate) blood pressure, and display the calculation result on the video monitor 80. .

  The video monitor 80 is an image display device and is realized by a flat panel display or a touch panel display. A speaker may be incorporated as appropriate.

  The keyboard 90 is operation input means for an operator to input various operations. In the example of FIG. 6, the keyboard 90 is swingably supported by a swing arm, and is configured to be raised and used when necessary. However, the keyboard 90 is configured to be integrated with the main body device 70 or the video monitor 80 is a touch panel. It is good also as a structure which serves as the operation input means. Furthermore, other operation input devices such as a mouse and a track pad can be added.

  The operation and processing contents of the blood pressure measurement device 10b are the same as those of the blood pressure measurement device 10 of the above embodiment.

10, 10b Blood pressure measurement device, 50 sensor module, 52-1 first light emitting unit, 52-2 second light emitting unit, 54 light receiving unit, 110 operation unit, 120 display unit, 130 sound output unit, 140 communication unit, 150 arithmetic unit, 151 light emission control unit, 152 light reception control unit, 153 switching control unit, 154 blood flow rate calculation unit, 155 volume pulse wave detection unit, 156 blood vessel resistance calculation unit, 157 blood concentration calculation unit, 158 blood pressure calculation unit, 160 Storage unit, 161 Blood pressure measurement program, 162 Blood vessel resistance correspondence table, 163 Blood flow volume data, 164 Volume pulse wave data, 165 Blood concentration data, 166 Blood vessel resistance data, 167 Blood pressure data, 2 users

Claims (8)

A light emitting unit that irradiates the living body with irradiation light of the first wavelength and irradiation light of the second wavelength;
A light receiving portion for receiving light reflected or transmitted in the living body;
Calculating a blood flow volume and a vascular resistance based on a light reception result of the light receiving unit accompanying irradiation of the irradiation light of the first wavelength and a light reception result of the light receiving unit accompanying irradiation of the irradiation light of the second wavelength; A calculation unit for calculating blood pressure from the blood flow and the vascular resistance;
A blood pressure measuring device. The computing unit is
The blood concentration is calculated from the light receiving results of the light receiving unit during the systole and diastole accompanying the irradiation of the first wavelength and the light receiving results of the light receiving unit during the systole and diastole accompanying the irradiation of the second wavelength. When,
Calculating the vascular resistance using the blood concentration;
Run the
The blood pressure measurement device according to claim 1. The light emitting unit includes a first light emitting unit that emits irradiation light of the first wavelength, and a second light emitting unit that emits irradiation light of the second wavelength,
In the first light emitting unit and the second light emitting unit, the distance between the first light emitting unit and the light receiving unit satisfies the same condition as the distance between the second light emitting unit and the light receiving unit. In the position,
The blood pressure measurement device according to claim 1 or 2. The calculation unit causes the light emitting unit to sequentially perform irradiation of the first wavelength and irradiation of the second wavelength.
The blood pressure measurement device according to any one of claims 1 to 3. The first wavelength belongs to a wavelength range of 800 ± 20 [nm], and the second wavelength belongs to a wavelength range of 976 ± 20 [nm].
The blood pressure measurement device according to any one of claims 1 to 4. The first wavelength belongs to a wavelength range of 800 ± 20 [nm], and the second wavelength belongs to a wavelength range of 1196 ± 20 [nm].
The blood pressure measurement device according to any one of claims 1 to 4. The calculation unit performs frequency analysis on the light received by the light receiving unit, and calculates the blood flow using the result of the frequency analysis.
The blood pressure measurement device according to any one of claims 1 to 6. An apparatus comprising: a light emitting unit that irradiates a living body with irradiation light of a first wavelength and irradiation light of a second wavelength; and a light receiving unit that receives light reflected or transmitted in the living body.
Calculating a blood flow volume and a vascular resistance based on a light reception result of the light receiving unit accompanying irradiation of the irradiation light of the first wavelength and a light reception result of the light receiving unit accompanying irradiation of the irradiation light of the second wavelength; ,
Calculating blood pressure from the blood flow volume and the vascular resistance;
Perform blood pressure measurement method.

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