JP6584297B2 - Pulse wave measuring device and pulse wave measuring method - Google Patents

Description

  The present invention relates to a pulse wave measuring device and a pulse wave measuring method capable of measuring a pulse wave of a living body with high accuracy.

  Currently, pulse wave measurement devices are not only used for medical devices that perform cardiovascular function diagnosis, but also detect driver drowsiness and physical condition, manage sports training status, or watch the elderly and disease prognosis (sudden changes in medical condition and physical condition). Wide range of applications such as monitoring of abnormalities) are expected.

  Various methods for measuring a pulse wave have been proposed, and methods for measuring a pulse wave by detecting a pressure pulse wave are known. A pressure pulse wave is a pressure wave transmitted to an arterial blood vessel, and can be detected based on a change in the surface of a living body such as skin. However, in order to detect the pressure pulse wave, it is necessary to attach a device capable of detecting a minute displacement on the surface of the living body to the corresponding position of the artery on the surface of the living body, for example, with a constant pressure.

  For this reason, the device can be mounted even if the position of the artery is not accurately grasped, and the pressure pulse wave can be reliably detected even if a position shift between the device and the artery occurs due to the operation of the measurement object. There is known a pulse wave measuring device provided with a plurality of pressure detection elements (see Patent Document 1).

JP 2004-222847 A

  However, in order to accurately detect the pressure pulse wave in a situation where the measurement target is operable, first, a high-resolution pressure detection element (pressure sensor) is pressed against the vicinity of the artery on the living body surface at a constant pressure. However, in this case, a pressurizing mechanism or the like for pressing the pressure detecting element against the surface of the living body is required, which increases the size of the pulse wave measuring device and restricts the operation of the measurement target. There was a problem that it ended up

  Furthermore, since all of the plurality of pressure detection elements are driven, noise caused by the operation of the measurement target is removed from the data output from each pressure detection element, and only the information on the pressure pulse wave is extracted. Furthermore, processing for selecting pressure pulse wave information with high signal strength and reliability is required. However, the pressure pulse wave information varies greatly depending on individual differences and circumstances, so the selection conditions are vague and wide. Therefore, if only the pressure pulse wave information with high signal strength and reliability is selected from a plurality of pressure pulse wave information, a complicated processing circuit and a large-capacity memory are required, and the pulse wave measuring device is complicated. Will lead to an increase in size and size.

  Accordingly, the present invention has been made to solve the above problems, and an object thereof is to provide a pulse wave measuring apparatus and a pulse wave measuring method capable of accurately measuring a pulse wave while corresponding to simplification and miniaturization. To do.

In order to solve the above problems, in the present invention,
A pulse wave measuring device that measures a pulse wave by calculating a displacement of a living body surface, and outputs a signal relating to a cavity disposed opposite to the living body surface and a differential pressure between an inner pressure and an outer pressure of the cavity. A plurality of pulse wave detectors having a differential pressure sensor and a membrane-type vibrator that varies the volume inside the cavity, and an arithmetic processing unit that calculates the displacement of the living body surface based on the output of the differential pressure sensor The arithmetic processing unit includes:
A separation unit that separates an output signal of the differential pressure sensor based on a drive signal of the membrane-type vibrator and outputs information based on displacement of the living body surface as an output signal, and an output signal of the separation unit Selecting a specific pulse wave detection unit from the plurality of pulse wave detection units based on an output signal of the differential pressure calculation unit and a differential pressure calculation unit for calculating a differential pressure between the internal pressure and the external pressure of the cavity And a pulse wave is measured by calculating the displacement of the surface of the living body based on the output of the specific pulse wave detection unit selected by the selection unit.

  Further, it is preferable that the selection unit selects, as the specific pulse wave detection unit, a pulse wave detection unit having the largest output signal intensity of the differential pressure output unit from the plurality of pulse wave detection units.

  In addition, the arithmetic processing unit is configured to calculate an internal pressure of the cavity based on the differential pressure and an external pressure calculated in the specific pulse wave detection unit, and based on the differential pressure. The number of moles of air in the cavity is calculated based on the number of moles of air flow that calculates the number of moles of air flowing in and out of the cavity, and the number of moles of flow calculated by the number of moles of air flow And a volume calculation unit for calculating the volume in the cavity based on the number of air moles calculated by the air mole number calculation unit and the internal pressure of the cavity calculated by the cavity internal pressure calculation unit, It is preferable to provide a displacement calculation unit that calculates the displacement of the living body surface based on the volume in the cavity calculated by the volume calculation unit.

  In addition, the arithmetic processing unit has a circulation mole number database unit that stores the circulation mole number of the air corresponding to the differential pressure as a database, and the air circulation mole number calculation unit is included in the circulation mole number database section. Based on this, it is preferable to extract the number of moles of air flow according to the magnitude of the differential pressure calculated by the differential pressure calculation unit.

  Further, the circulation mole number database part is generated by calculating a relationship between a pressure difference inside and outside the cavity and a circulation amount of air, and calculating the number of moles of air circulation based on the relationship and the differential pressure. It is preferable.

  In addition, it has an air temperature acquisition unit that acquires temperature information of air flowing inside and outside the cavity, and the air mole number calculation unit calculates the number of air moles in the cavity based on the temperature information and the flow mole number. It is preferable.

  Moreover, it is preferable that a flexible contact surface is provided in a region of the cavity that faces the biological surface.

  In addition, it is preferable to have a reference pulse wave detector that does not deform the volume of the cavity due to the displacement of the living body surface.

  In addition, the differential pressure sensor is provided so as to block a part of the cavity, and cantilever which bends and deforms according to a differential pressure between the internal pressure and the external pressure of the cavity, and a displacement according to the deformation of the cantilever. It is preferable to have a displacement measuring unit that measures

  In the pulse wave measurement method according to the present invention, a cavity disposed opposite to the surface of the living body, a differential pressure sensor that outputs a signal related to a differential pressure between the internal pressure and the external pressure of the cavity, and a volume inside the cavity are determined. A pulse wave measuring method for measuring a pulse wave by calculating a displacement of the living body surface using a plurality of pulse wave detectors having a membrane-type vibrator to be fluctuated, comprising: A separation step of separating an output signal of the differential pressure sensor based on a drive signal and outputting information based on displacement of the living body surface as an output signal, and an internal pressure of the cavity based on the output signal of the separation step A differential pressure calculation step for outputting a differential pressure output signal relating to a differential pressure between the external pressure and the external pressure, and a specific pulse wave detection from the plurality of pulse wave detection units based on the output signal of the differential pressure calculation step And a selection step of selecting, based on an output of the particular pulse wave detector that is selected by said selection step, to calculate the displacement of the living body surface and measuring the pulse wave.

  In the selection step, it is preferable that a pulse wave detection unit having the largest output signal intensity of the differential pressure output unit is selected as the specific pulse wave detection unit from the plurality of pulse wave detection units.

  Further, when calculating the displacement of the living body surface based on the output of the specific pulse wave detection unit selected in the selection step, the differential pressure and the external atmospheric pressure calculated in the specific pulse wave detection unit are calculated. A cavity internal pressure calculating step for calculating the internal pressure of the cavity based on the differential pressure, an air circulation mole number calculating step for calculating a flow molar number of air flowing inside and outside the cavity based on the differential pressure, and the air Based on the flow mole number calculated in the flow mole number calculation step, the air mole number calculation step for calculating the air mole number in the cavity, the air mole number calculated in the air mole number calculation step, and the air pressure calculation in the cavity A volume calculating step for calculating a volume in the cavity based on an internal pressure of the cavity calculated in the step; and the volume calculation. A displacement calculating step of calculating the displacement of the living body surface based on the volume of the calculated cavity by step, it is preferable that comprises.

  Further, in the air circulation mole number calculation step, the magnitude of the differential pressure calculated by the differential pressure calculation step based on a circulation mole number database storing the circulation mole number of the air corresponding to the differential pressure as a database. It is preferable to extract the number of moles of air flow according to the above.

  Further, the flow mole number database is generated by calculating a relationship between a pressure difference inside and outside the cavity and a flow amount of air, and calculating the air flow mole number based on the relationship and the differential pressure. Is preferred.

  Preferably, the method has an air temperature acquisition step of acquiring temperature information of the air, and the step of calculating the number of moles of air preferably calculates the number of moles of air in the cavity based on the temperature information and the number of moles of flow.

  In addition, it is preferable to have a reference pulse wave detection step in which the volume of the cavity is not deformed by the displacement of the living body surface.

  Also, at least the separation step, the differential pressure calculation step, the cavity internal pressure calculation step, the air circulation mole number calculation step, the air mole number calculation step, the volume calculation step, and the displacement calculation step. It is preferable to have an iterative processing step that repeatedly executes

  Further, it is preferable that the repetitive processing step is executed every set predetermined time.

  Preferably, in the differential pressure calculating step, each of the differential pressure output signals for each predetermined time is stored in a storage device, and the differential pressure for each predetermined time is obtained based on the stored differential pressure output signal. It is.

  Further, it is preferable that the selecting step is executed after the differential pressure output signal output in the differential pressure calculating step is continuously lower than a predetermined signal strength reference value for a predetermined time. is there.

  As described above, according to the present invention, it is possible to provide a pulse wave measuring device capable of accurately measuring a pulse wave while corresponding to simplification and miniaturization.

It is a mimetic diagram showing a schematic structure of pulse wave measuring device 1 concerning a 1st embodiment of the present invention. It is a block diagram of pulse wave measuring device 1 concerning a 1st embodiment of the present invention. It is a schematic diagram which shows schematic structure of the pulse wave detection part 5 in the 1st Embodiment of this invention. It is a schematic diagram explaining operation | movement of the pulse-wave detection part 5 in the 1st Embodiment of this invention. It is a schematic diagram explaining operation | movement of the pulse-wave detection part 5 in the 1st Embodiment of this invention. It is a flowchart which shows the flow of the function of the pulse-wave measuring apparatus 1 which concerns on the 1st Embodiment of this invention. It is a block diagram of pulse wave measuring device 201 concerning a 2nd embodiment of the present invention. It is a schematic diagram which shows schematic structure of the pulse-wave detection part 205 which concerns on the 2nd Embodiment of this invention. It is a schematic block diagram of the reference pulse wave detection part 215 in the 2nd Embodiment of this invention.

  Hereinafter, embodiments of a pulse wave measuring device and a pulse wave measuring method according to the present invention will be described with reference to the drawings.

(First embodiment)
(overall structure)
FIG. 1 shows a configuration of a pulse wave measuring apparatus 1 according to the first embodiment of the present invention.
In the present embodiment, the pulse wave measuring device 1 has a form similar to a wristwatch, and includes a device main body 3 and a band 2 fixed to a side surface of the device main body 3.

  The band 2 is composed of, for example, an annular elastic material or the like, and the apparatus main body 3 is attached so as to be in close contact with the user's skin 4. In addition, although demonstrated using the human skin 4 here as a biological body surface, the measuring object which can use the pulse-wave measuring apparatus which concerns on this invention is not restricted to a human. It is also possible to use animal skin or the like as the surface of the living body, and to close the apparatus main body 3 to the surface of the living body.

  The apparatus main body 3 has a plurality of pulse wave detectors 5 in the lower part (skin 4 side in the figure), a ventilation hole 6 for communicating the pulse wave detectors 5 and the outside air in the apparatus main body 3, and a later-described And a control board 7 (control unit) on which elements having various functions are mounted.

  The pulse wave detection unit 5 includes a recess 51 formed on the outside of the apparatus body 3 and on the skin 4 side, a differential pressure sensor 52, and a membrane type vibrator 53. That is, the concave portion 51 is disposed opposite to the skin 4, and thereby the cavity 54 (FIG. 3) is formed by the concave portion 51 and the skin 4.

  Further, a differential pressure sensor 52 and a membrane-type vibrator 53 are provided on one surface of the cavity 54 formed by the recess 51 and the skin 4 (surface opposite to the skin 4). The structure and function of each component will be described in detail later. Further, the differential pressure sensor 52 and the membrane-type vibrator 53 have an electrical connection with the control board 7 mounted inside the apparatus main body 3.

  FIG. 2 shows a block diagram of the pulse wave measuring apparatus 1. In addition to the differential pressure sensor 52 and the membrane transducer 53, the pulse wave measuring device 1 includes a control unit 71 provided on the control board 7, a power source 72, a storage unit 73, an arithmetic processing unit 74, and a display. Part 75.

The control unit 71 includes, for example, a CPU, a ROM, and the like, and comprehensively controls driving of the entire apparatus body 3.
The power source 72 is, for example, a power source including various primary batteries such as dry batteries and secondary batteries such as batteries, and supplies power to each unit included in the apparatus main body 3.
The storage unit 73 includes, for example, various non-volatile memories and stores a drive program executed by the control unit 71 and the arithmetic processing unit, various data, and a reference table described later.

The arithmetic processing unit 74 separates the drive signal of the membrane-type vibrator 53 from the output signal of the differential pressure sensor 52 and the specific processing most suitable for detecting a pulse wave from the output signal of the separation unit 11. And a selection unit 12 that selects the pulse wave detection unit 5.
Further, based on the output signal from the pulse wave detection unit 5 selected by the selection unit 12, the differential pressure calculation that calculates the differential pressure between the internal pressure and the external pressure of the cavity 54 from the signal output through the separation unit 11. Unit 13, cavity internal pressure calculation unit 14 for calculating the internal pressure of cavity 54, air circulation mole number calculation unit 15 for calculating the number of moles of air flowing through cavity 54, and the number of moles of air in cavity 54. It has an air mole number calculation unit 16 to calculate, a volume calculation unit 17 to calculate the volume of the cavity 54, and a displacement calculation unit 18 to calculate the displacement of the skin due to pulsation. The function of each unit included in the arithmetic processing unit 74 will be described in detail later (on the displacement calculation flow).

(Structure of pulse wave detector)
With reference to FIG. 3, the structure of the pulse-wave detection part 5 is demonstrated. 3A is a plan view of the pulse wave detector 5, and FIG. 3B is a cross-sectional view taken along the plane AA shown in FIG. 3A.

  The pulse wave detection unit 5 includes a recess 51, a differential pressure sensor 52, and a membrane type vibrator 53. When the pulse wave measuring device 1 is mounted, the bottom surface of the recess 51 and the skin 4 are in pressure contact. As a result, a cavity 54 that is a space surrounded by the recess 51 and the skin 4 is formed.

  The differential pressure sensor 52 is configured by a substantially U-shaped cantilever in which a thin plate-like membrane 57 provided on the upper surface of the recess 51 is cut out from two substantially U-shaped gaps 55. For this reason, when the pulse wave measuring device 1 is mounted, the differential pressure sensor 52 is provided on one surface of the cavity 54 formed by the contact between the skin 4 and the recess 51.

The differential pressure sensor 52 is electrically connected to the control board 7 via two electrodes 56.
The differential pressure sensor 52 is a substantially U-shaped thin plate made of extremely thin Si of about 300 nm, for example, and is fixed at the U-shaped tip. The differential pressure sensor 52 has a size of about 100 microns on one side, for example, and bends due to the differential pressure if there is a slight difference between the upper and lower atmospheric pressures. Since the vicinity of the fixed end of the differential pressure sensor 52 functions as a piezoresistor by doping impurities such as P (phosphorus) only in the vicinity of the upper surface, a remarkable piezoresistive effect is exhibited. In addition, air flows inside and outside the cavity 54 through the gap 55 and the vent hole 6 around the differential pressure sensor 52. Since only one end of the differential pressure sensor 52 is fixed, the differential pressure sensor 52 can be bent even with a slight force as compared with a diaphragm sensor that is fixed at the entire periphery, and functions as a highly sensitive differential pressure sensor.

  The membrane-type vibrator 53 is provided in the vicinity of the outer periphery of the membrane 57 provided on the upper surface of the recess 51. Similar to the differential pressure sensor 52, when the pulse wave measuring device 1 is mounted, the membrane 57 is provided on one surface opposite to the skin 4 of the cavity 54 formed by the contact between the skin 4 and the recess 51.

  The membrane-type vibrator 53 is made of, for example, a piezoelectric element or a piezoelectric thin film, and expands and contracts according to a given potential. Further, since the membrane 57 is made of, for example, thin Si of several tens of μm or less, the membrane 57 vibrates in the thickness direction by the expansion and contraction operation of the membrane type vibrator 53. Thereby, the membrane-type vibrator 53 has a function of exciting the membrane 57 and changing the volume of the cavity 54.

(Operation of pulse wave detector)
Next, with reference to FIGS. 4 and 5, the operation of the pulse wave detector 5, particularly the operations of the membrane transducer 53 and the differential pressure sensor 52 will be described. 4 and 5 are cross-sectional views of the pulse wave detection unit 5. Note that the volume, pressure, and number of moles of air inside the cavity 54 are V, Pin, and N, respectively, for example, V (0), Pin (0), and N, respectively, to indicate values at time T0. It is expressed as (0) and indicates a physical quantity at each time.

  First, FIG. 4 shows an operation of the membrane vibrator 53 and a cross-sectional view of the pulse wave detector 5 at that time. 4A shows the initial state at time T0, FIG. 4B shows the time after time T0, time T1 when the membrane-type vibrator 53 contracts, and FIG. 4C shows the membrane-type vibrator 53 after time T1. Each shows a cross-section at time T2 when is extended.

  Here, as shown in FIG. 4B, when the membrane-type vibrator 53 contracts at time T1, the membrane 57 is deformed upward. Then, the volume V inside the cavity increases and the atmospheric pressure Pin decreases. As a result, the differential pressure sensor 52 bends downward due to the differential pressure between the atmospheric pressure Pin and the external atmospheric pressure. Then, the electric resistance value of the piezoresistive element built in the differential pressure sensor 52 changes. This is converted into a signal corresponding to the amount of deflection of the differential pressure sensor 52 by the electrically connected control board 7.

Further, as shown in FIG. 4C, when the membrane-type vibrator 53 expands at time T2, the membrane 57 is deformed downward. Then, the volume V inside the cavity decreases and the atmospheric pressure Pin increases. As a result, the differential pressure sensor 52 bends upward due to the differential pressure between the atmospheric pressure Pin and the external atmospheric pressure. Then, the electrical resistance value of the piezoresistive element built in the differential pressure sensor 52 changes in the opposite direction to that at time T1. This is converted into a signal corresponding to the amount of deflection of the differential pressure sensor 52 by the electrically connected control board 7.
Therefore, an output signal is obtained from the differential pressure sensor 52 via the control board 7 in a form synchronized with the expansion / contraction of the membrane type vibrator 53.

  Next, the operation of the differential pressure sensor and the movement of the skin 4 due to the pulsation of the artery will be described with reference to FIG. FIG. 5A shows a cross section at time T0 representing the initial state, and FIG. 5B shows a cross section at time T3 when pulsation occurs under the skin 4 after time T0.

  Here, as shown in FIG. 5 (b), it is assumed that the skin 4 is displaced downward at time T1 due to the pulsation of the underlying artery. Then, the volume V inside the cavity 54 increases and the atmospheric pressure Pin decreases. As a result, the differential pressure sensor 52 bends downward due to the differential pressure between the atmospheric pressure Pin and the external atmospheric pressure. Then, the electric resistance value of the piezoresistive element built in the differential pressure sensor 52 changes. This is converted into a signal corresponding to the amount of deflection of the differential pressure sensor 52 by the electrically connected control board 7.

  Here, it is assumed that the expansion / contraction operation of the membrane-type vibrator 53 and the displacement of the skin 4 are performed simultaneously. In this case, the volume change due to the operation of the membrane vibrator 53 and the volume change due to the displacement of the skin 4 occur simultaneously, and an output signal of the differential pressure sensor 52 corresponding to the added volume change can be obtained. Become.

  Since the operation of the membrane type vibrator 53 is known from the drive signal of the membrane type vibrator 53, the output signal (differential pressure output signal) of the differential pressure sensor 52 due to the volume change caused by the operation of the membrane type vibrator 53 is obtained in advance. be able to. For this reason, it is possible to extract only the output signal corresponding to the volume change due to the displacement of the skin 4 from the added output signal of the differential pressure sensor 52. More simply, when the membrane-type vibrator 53 is driven at a constant frequency faster than the pulse wave (displacement of the skin 4), a frequency filter is applied to the output signal of the differential pressure sensor 52, so that the membrane-type vibrator The signal due to the operation and the signal due to the pulse wave can be separated. Thus, by separating from the output signal of the differential pressure sensor 52, only the displacement signal of the skin 4 can be extracted.

  The relationship between the deflection amount of the differential pressure sensor 52 calculated from the extracted displacement signal of the skin 4 and the pressure difference (differential pressure) inside and outside the cavity 54 is measured in advance as a “piezoresistance value and differential pressure reference table”. And stored in the storage unit 73. Therefore, the differential pressure calculation unit 13 can calculate the differential pressure from the output signal of the differential pressure sensor 5 and the reference table of the storage unit 13.

  Further, when the pressure Pin in the cavity 54 decreases, air flows from the outside air into the cavity 54. At this time, the amount of the inflow of the air expressed in moles is ΔN. Thus, when the skin 4 is displaced, V, Pin, and N all change. Similar to the above-described reference table, the relationship between the differential pressure calculated from the output signal due to the displacement of the skin 4 and ΔN is determined based on the experiment in which the flowmeter is incorporated in the pulse wave measuring device 1 or the displacement of the differential pressure sensor 52 and the air. It may be acquired in advance by a computer simulation in which the inflow / outflow relationship is coupled and stored in the circulation mole number database section of the storage section 73 as a “reference table of differential pressure and air inflow amount” (database). According to this, after calculating the differential pressure, it is possible to extract an appropriate ΔN from the circulation mole number database part, so that the processing can be simplified and speeded up.

(Displacement calculation flow)
Next, the flow of displacement calculation of the skin 4 by the pulse wave measurement device 1 according to the first embodiment of the present invention will be described with reference to an explanatory diagram (flowchart) shown in FIG.

  First, based on the output signals of each of the plurality of pulse wave detectors 57, the selector 12 detects specific pulse waves in which there is no air leakage from the cavity 54 and the skin 4 is most significantly displaced based on arterial pulsations. A selection step for selecting the part 57 is performed (STEP 0).

  Next, the volume V (0) in the cavity 54 is approximately known from the design dimension of the recess 51, and the pressure Pin (0) in the cavity 54 is the same as the external air pressure. , The air mole number calculation unit 14 obtains the mole number N (0) = Pin (0) V (0) / RK from the gas state equation PV = NRK using the temperature K (STEP 1). The temperature K and the atmospheric pressure are based on a control signal from the control unit 71, and are a thermometer (not shown) connected to the pulse wave measuring device 1 or provided in the pulse wave measuring device 1 or a pressure for measuring absolute pressure. A sensor (not shown) may be transmitted as an electric signal to the arithmetic processing unit 74 (the number of moles of air calculating unit 16).

  Next, after the pulse wave measuring device 1 starts measuring displacement, the skin 4 is displaced by pulsation at time T3, the differential pressure sensor 52 is deflected, and a signal related to the piezoresistance value is output to the arithmetic processing unit 74 ( (Step 2).

  Next, the differential pressure calculation unit 13 refers to the “piezoresistance value and differential pressure reference table” stored in the storage unit 73 and calculates the differential pressure from the piezoresistance value. Further, the cavity internal pressure calculation unit 14 calculates the pressure Pin (3) that is the internal pressure of the cavity 54 by subtracting the calculated differential pressure from the external pressure assuming that the external air pressure is constant (STEP 3).

  Next, the air circulation mole number calculating unit 15 refers to the “reference table of differential pressure and air inflow amount” stored in the storage unit 73 and calculates the air inflow amount ΔN from the differential pressure calculated in STEP 3. (STEP 4). Here, as described above, the “reference table of the differential pressure and the air inflow amount” has, for example, the value (mol / sec) of the air inflow amount Q per unit time corresponding to the value (Pa) of the differential pressure ΔP. The database is made according to the magnitude of the differential pressure ΔP.

  Next, the air mole number calculation unit 16 adds the air inflow amount ΔN calculated in STEP 4 to the air mole number N (0) at time T0, so that the air mole number N (( 3) is calculated (STEP 5).

  Next, the volume calculation unit 17 substitutes Pin (3) calculated in STEP 3 and N (3) calculated in STEP 5 into the gas state equation again, so that the volume V (3 in the cavity 54 ) Is calculated (STEP 6).

  Next, the displacement calculation unit 18 divides the volume change (V (3) −V (0)) by the cross-sectional area of the cavity 54 because the cross-sectional area of the cavity 54 does not change if the recess 51 itself is not deformed. Thus, the displacement of the skin 4 is calculated (STEP 7).

  Then, the control unit 71 determines whether or not to continue the measurement (STEP 8), and when it is determined that the measurement is to be continued (Y in STEP 8), the control processing unit 74 continues to repeatedly execute the processing from step 2 and does not continue. If it is determined that this is the case (N of STEP 8), this process is terminated. This repeated process is referred to as a repeated process step. In addition, this repetitive processing step may be executed every set predetermined time.

  In STEP 4, the air circulation mole number calculation unit 15 calculates the air inflow amount Q per unit time and the time interval (when the air inflow amount ΔN is calculated from the above-mentioned “reference table of differential pressure and air inflow amount”. T3-T0) is integrated. This step time can be set as needed.If the time is shortened, the amount of calculation increases, but a high-accuracy result can be obtained.If the length is shortened, the accuracy is reduced, but it can be calculated in a short time. Set.

  Further, the arithmetic processing unit 74 replaces the processing procedure of the flowchart shown in FIG. 6 and repeatedly obtains the piezoresistance value (STEP 2) for a predetermined time before storing the result data in the storage unit 73. Alternatively, the piezoresistance value may be sequentially read from the storage unit 73 and the processing after STEP3 may be performed.

  Further, when the arithmetic processing unit 74 determines that the state in which the acquired piezoresistance value is less than the predetermined value continues for a predetermined time when acquiring the piezoresistance value (STEP 2), the determination time point May be time T0, and the processing after STEP1 may be executed. That is, the processing after STEP 1 may be executed after the differential pressure output signal output in the differential pressure calculating step continues for a predetermined time period lower than the predetermined signal strength reference value.

  In addition, the processing itself may be performed for each output signal at the same time, or by temporarily storing the output signal of the differential pressure sensor in a memory for a certain period of time. Although the obtained result is the same, it is only necessary to select whether real-time pressure pulse wave information is necessary or whether information update with a certain time delay may be performed, depending on the method of using the pressure pulse wave information.

(Pulse wave detector selection method)
The selection step of the pulse wave detector 57 described in STEP 0 in FIG. 6 will be described.
The plurality of pulse wave detectors 5 provided in the pulse wave measuring device 1 take three states when worn. First, the concave portion 51 and the skin 4 are in close contact with each other, and the skin 4 is displaced by the pulsation of the artery below the skin 4. Second, the concave portion 51 and the skin 4 are in close contact with each other, but there is no artery under the skin 4 and the skin 4 is not displaced. Thirdly, the recess 51 and the skin 4 are not in close contact with each other, and the cavity 54 is not formed. The pulse wave detection unit 5 necessary for pulse wave measurement is of the first classification, and it is necessary to select only this.

  First, the membrane type vibrator 53 of the pulse wave detector 57 is expanded and contracted, and the output signal of the differential pressure sensor 52 at that time is measured. At this time, the pulse wave detection unit 57 that cannot obtain the output signal of the differential pressure sensor 52 according to the operation of the membrane vibrator 53 is the third classification, and there is a gap between the recess 51 and the skin 4. Therefore, the cavity 54 is not formed, and the displacement of the skin 4 cannot be detected by the differential pressure sensor 52. Therefore, such a pulse wave detector 57 is excluded from the output signal detection.

  Next, it is determined whether there is skin displacement (arterial pulsation under the skin) of the pulse wave detection unit that can obtain the output signal of the differential pressure sensor 52 synchronized with the operation of the membrane transducer 53. First, if the output signal of the differential pressure sensor 52 is separated by using the separation unit 11 to exclude the signal due to the operation of the membrane vibrator 53, the output signal of the differential pressure sensor 52 corresponding to the displacement of the skin 4 is separated. It is possible to take out only. Here, since the frequency band of the pulse can be roughly determined by the living body to be attached, the pulse wave detection unit 5 having an amplitude larger than a predetermined value is determined by filtering the extracted output signal of the differential pressure sensor 52 in the frequency component band of the pulse. To do. That is, the pulse wave detection unit 5 that outputs a signal intensity greater than a predetermined threshold value is selected as the specific pulse wave detection unit 5. Here, the pulse wave detection unit 5 having a signal intensity larger than the threshold and having the highest signal intensity is set as the specific pulse wave detection unit, but a plurality of pulse wave detection units larger than the threshold are set as the specific pulse wave detection units. You may choose.

As a result, only the pulse wave detector 5 of the third category can be selected and its output signal can be used.
Driving only the membrane-type vibrator 53 of the pulse wave detection unit 5 selected as a specific pulse wave detection unit and its differential pressure sensor 52, taking out the output signal of the differential pressure sensor 52, and performing the above-described displacement calculation flow Thus, the displacement (pulse wave) of the skin can be measured. Here, using a method such as adding and using the signals of the differential pressure sensor 52 to be used, adding and using only a predetermined number of signals from the larger amplitude, or using an output signal having the largest amplitude. The output signal can be determined and the process can proceed to STEP1 in FIG.

  As described above, since the pulse wave detection unit 5 from which the skin fluctuation (pulse wave) is remarkably obtained can be selected among the plurality of pulse wave detection units 5, the pulse is detected with a simple configuration without setting the wearing position strictly. Waves can be accurately measured. Even if the pulse wave cannot be measured from the selected pulse wave detector 5 due to body movement or the like, the pulse wave can be continuously measured by selecting the pulse wave detector 5 again.

  Further, since the pulse wave detector 5 under conditions that can be measured can be selected by driving the membrane-type vibrator 53, the number of signals to be processed can be reduced, and the load of signal processing and the amount of memory used can be reduced. Become. For this reason, size reduction of the pulse wave measuring apparatus 1 is realizable.

  As described above, according to the pulse wave measuring apparatus 1 according to the present embodiment, the pulse wave can be accurately measured without specifying the skin region in which the pulsation of the artery can be detected in advance, so that it can be easily attached and the pressure pulse wave is surely obtained. Can continue to be detected. Further, when the skin 4 is slightly displaced due to pulsation, it is obtained as an electric resistance value of piezoresistance generated by the deflection of the differential pressure sensor 52, and the inflow / outflow amount of air between the outside air and the cavity 54 is taken into consideration. The displacement of the skin 4 can be calculated by solving the equation of state of the gas introduced. Further, according to the pulse wave measuring device 1, by using the differential pressure sensor 52 having only one end fixed, it can be greatly bent even with a slight differential pressure, and thus high sensitivity detection is possible. At the same time, by separating the output signal of the differential pressure sensor 52 based on the drive signal of the membrane transducer 53, a highly sensitive and accurate pulse wave measurement method can be realized.

(Second Embodiment)
Next, the pulse wave measurement device 201 according to the second embodiment of the present invention will be described. FIG. 7 is a block diagram illustrating a configuration of the pulse wave measurement device 201 according to the present embodiment. FIG. 8 shows a pulse wave detection unit 205 constituting the pulse wave measurement device 201 according to the present embodiment.

  The pulse wave measuring device 201 of the present embodiment is different from the first embodiment described above in that the pulse wave measuring device 201 includes a pulse wave detecting unit 211 and a pulse wave calculating device 212, and communication provided in both of them. This is the point where information is transmitted between the units 76. That is, the pulse wave detector 211 is provided on the measurement target, and the pulse wave calculation device 212 is provided at a position separated from the measurement target. Furthermore, one surface forming the cavity 54 of the pulse wave detection unit 205 is not the skin 4.

Details will be described below.
A pulse wave measurement device 201 shown in FIG. 7 includes a pulse wave detection device 211 and a pulse wave calculation device 212. The pulse wave detection device 211 includes a pulse wave detection unit 205, a control unit 71, a power source 72, and a communication unit 76. The pulse wave calculation device 212 includes a power source 72, a storage unit 73, a calculation processing unit 74, and a communication unit 76.
The communication unit 76 has a function of wirelessly or wiredly communicating pulse wave information, a command to the control unit 71, and the like between the pulse wave detection device 211 and the pulse wave calculation device 212.

  FIG. 8 shows a detailed configuration of the pulse wave measuring device 201. At the same time as providing a plurality of pulse wave detection units 205 in the apparatus main body 3 according to the present embodiment, the pulse wave detection unit 205 has a configuration in which a contact surface 252 is provided on a surface in contact with the skin 4. For this reason, the cavity 54 is configured to be covered with the housing 251, the contact surface 252, the differential pressure sensor 52, and the membrane 57. Note that the contact surface 252 is made of, for example, a thin film of resin or the like, and when pressed against the skin 4, the contact surface 252 deforms and adheres to the unevenness of the skin 4 surface.

  On the other hand, unlike the pulse wave detection unit in the first embodiment, the volume of the cavity 54 varies depending on the driving of the membrane vibrator 53 even if it is not in contact with the skin 4. Output signal is obtained. The output signal of the differential pressure sensor 52 is transmitted to the calculation processing unit 74 of the pulse wave calculation device 212 via the communication unit 76.

  Here, based on the frequency of the drive signal of the membrane transducer 53, the separation unit 11 separates and outputs the output signal of the differential pressure sensor 52, and only the skin displacement due to pulsation is taken out. Therefore, similarly to the first embodiment, the calculation processing unit 74 can select the pulse wave detection unit 205 that can detect the displacement of the skin from the plurality of pulse wave detection units 205.

  The information of the selected pulse wave detection unit 205 is transmitted again to the control unit 71 of the pulse wave detection device 211 via the communication unit 76, and only the output signal from the selected pulse wave detection unit 205 is continued. , It continues to be transmitted to the pulse wave calculation device 212. As described above, it is possible to calculate pulse wave information from the transmitted output signal of the pulse wave detector 205 and continuously measure the pulse wave.

  On the other hand, the control unit 71 controls the power source 72 of the pulse wave detection device 211 via the communication unit 76 so as to interrupt the power supply to the pulse wave detection unit 205 that has not been selected. When pulse wave information cannot be obtained from the selected pulse wave detection unit 205, the arithmetic processing unit 74 instructs the control unit 71 to supply power to all the pulse wave detection units 205 via the communication unit 76.

  Then, the selection of the pulse wave detection unit 205 from which the pulse wave information is obtained again and the skin displacement calculation flow are performed. As a result, pulse wave information can be obtained continuously using a plurality of pulse wave detectors, and at the same time, power saving can be realized.

  Furthermore, since the contact wave 252 is provided in the pulse wave detection unit 205, the differential pressure sensor 52 and the membrane 57 are separated from the external environment. Damage can be avoided.

  On the other hand, since the cavity 54 of this embodiment is a substantially closed space, there is a possibility that the differential pressure sensor 52 may detect a change in the external air pressure. This can be avoided by providing one reference pulse wave detector 215 shown in FIG. The reference pulse wave detection unit 215 includes a cavity 54 surrounded by a casing 251, a wall surface 253, a membrane 57, and a differential pressure sensor 52.

  Since the wall surface 253 is made of a material that is not easily deformed, such as a thermoplastic resin, as in the case 251, even if the reference pulse wave detector 251 is pressed against the skin 4, the volume of the cavity 54 is displaced by the displacement of the skin 4. Will not be deformed. For this reason, since the differential pressure sensor 52 communicates with the outside air through the vent hole 6, the differential pressure between the outside air pressure and the cavity 54 is measured, but the inside pressure of the cavity 54 follows the fluctuation of the outside air pressure. Therefore, the output signal of the differential pressure sensor 52 indicates a change in the external air pressure.

  Therefore, by calculating the difference between the output signal of the reference pulse wave detection unit 251 from the output signal of the pulse wave detection unit 205, the fluctuation component of the external atmospheric pressure can be excluded from the output signal of the pulse wave detection unit 205. Only the pulse wave component can be extracted.

In the first embodiment, the pulse wave measuring device that is mounted on the wrist and measures the pulse wave is shown. In the present embodiment, pulse waves can be measured as long as the arteries are in pressure contact with a portion other than the wrist so that the volume of the cavity 54 varies in the vicinity of the skin. For example, the apparatus main body 3 is attached to the vicinity of the ankle, the back of the knee, the wrist, etc. with an adhesive tape, or the apparatus main body 3 is formed into a mat-like structure made of a flexible material, and directly on the apparatus main body 3. Configuration to lie down and measure the pulse wave, configuration to install the device body 3 at a place that is in close contact with the skin, such as a hat, sun visor, glasses, etc., configuration to measure the pulse wave by pressing against the temple portion, configuration to wrap around the neck portion, etc. Can be considered.
Furthermore, by configuring the pulse wave measuring device 201 with the pulse wave detecting device 211 and the pulse wave calculating device 212, it is possible to reduce the size of the structure attached to or pressed against the living body, and to suppress the continuous pulse wave without suppressing the operation. Measurement is possible.

  As described above, according to the pulse wave measuring device according to the present embodiment, it is easy to mount and can be downsized, and it is possible to reliably detect the pressure pulse wave and to avoid damage due to intrusion of moisture. It is possible to improve the performance and life. In addition, the influence of fluctuations in the external air pressure can be eliminated, and more accurate pulse wave measurement can be realized.

1, 201 Pulse wave measurement device 2 Band 3 Device body 4 Skin 5, 205 Pulse wave detection unit 6 Vent 7 Control substrate 11 Separation unit 12 Selection unit 13 Differential pressure calculation unit 14 Cavity pressure calculation unit 15 Calculation of moles of air flow Unit 16 Number of moles calculation unit 17 Volume calculation unit 18 Displacement calculation unit 51 Concave portion 52 Differential pressure sensor 53 Membrane transducer 54 Cavity 55 Gap 56 Electrode 57 Membrane 71 Control unit 72 Power source 73 Storage unit 74 Operation processing unit 75 Display unit 76 Communication unit 211 Pulse wave detection device 212 Pulse wave calculation device 215 Reference pulse wave detection unit 251 Housing 252 Contact surface 253 Wall surface V Volume inside cavity 54 P Pressure inside cavity 54 Number of moles of air inside cavity 54 STEP0-8 Each step of the pulse wave measurement method according to the first embodiment of the present invention

Claims (18)

A pulse wave measuring device that measures a pulse wave by calculating a displacement of a living body surface,
A plurality of cavities disposed opposite to the surface of the living body, a differential pressure sensor that outputs a signal relating to a differential pressure between the internal pressure and the external pressure of the cavity, and a membrane type vibrator that varies the volume inside the cavity. A pulse wave detector of
An arithmetic processing unit that calculates the displacement of the living body surface based on the output of the differential pressure sensor;
With
The arithmetic processing unit includes:
A separation unit that separates an output signal of the differential pressure sensor based on a drive signal of the membrane-type vibrator, and outputs information based on the displacement of the living body surface as an output signal;
A differential pressure calculation unit that calculates a differential pressure between the internal pressure and the external pressure of the cavity based on the output signal of the separation unit;
A selection unit that selects a specific pulse wave detection unit from the plurality of pulse wave detection units based on an output signal of the differential pressure calculation unit;
The selection unit selects, as the specific pulse wave detection unit, a pulse wave detection unit having the largest output signal intensity of the differential pressure calculation unit from the plurality of pulse wave detection units,
A pulse wave measuring device that measures a pulse wave by calculating a displacement of the living body surface based on an output of the specific pulse wave detecting unit selected by the selecting unit. The arithmetic processing unit includes:
A cavity internal pressure calculation unit that calculates an internal pressure of the cavity based on the differential pressure and external pressure calculated in the specific pulse wave detection unit;
Based on the differential pressure, an air circulation mole number calculation unit for calculating the air circulation mole number flowing inside and outside the cavity;
Based on the flow mole number calculated by the air flow mole number calculation section, the air mole number calculation section for calculating the air mole number in the cavity;
Based on the number of air moles calculated by the air mole number calculation unit and the internal pressure of the cavity calculated by the cavity internal pressure calculation unit, a volume calculation unit that calculates the volume in the cavity;
A displacement calculator that calculates the displacement of the living body surface based on the volume in the cavity calculated by the volume calculator;
The pulse wave measuring device according to claim 1, further comprising: The arithmetic processing unit has a circulation mole number database unit that stores the air circulation mole number corresponding to the differential pressure as a database,
The air flow mole number calculation unit extracts the air flow mole number corresponding to the magnitude of the differential pressure calculated by the differential pressure calculation unit based on the flow mole number database unit. Item 3. The pulse wave measuring device according to Item 2 . The circulation mole number database unit is generated by calculating a relationship between a pressure difference inside and outside the cavity and a circulation amount of air, and calculating the number of moles of air circulation based on the relationship and the differential pressure. The pulse wave measuring device according to claim 3 . Having an air temperature acquisition unit for acquiring temperature information of air flowing inside and outside the cavity;
The pulse wave measurement according to any one of claims 2 to 4 , wherein the air mole number calculation unit calculates the air mole number in the cavity based on the temperature information and the flow mole number. apparatus. Wherein in a region facing the living body surface in the cavity flexible, according to any one of claim 1 to 5, characterized in that the contact surface in contact with the biological surface is provided Pulse wave measuring device. The pulse wave measuring device according to any one of claims 1 to 6 , further comprising a reference pulse wave detecting unit in which the volume of the cavity is not deformed by the displacement of the living body surface. The differential pressure sensor is
A cantilever that is provided so as to block a part of the cavity, and that bends and deforms according to a differential pressure between an internal pressure and an external pressure of the cavity;
A displacement measuring unit for measuring displacement according to the bending deformation of the cantilever;
The pulse wave measuring device according to any one of claims 1 to 7 , wherein A plurality of cavities disposed opposite to the surface of the living body, a differential pressure sensor that outputs a signal related to a differential pressure between the internal pressure and the external pressure of the cavity, and a membrane-type vibrator that varies the volume inside the cavity. A pulse wave measurement method for measuring a pulse wave by calculating a displacement of the living body surface using a pulse wave detector,
A separation step of separating an output signal of the differential pressure sensor based on a drive signal of the membrane-type vibrator and outputting information based on displacement of the living body surface as an output signal;
Based on the output signal of the separation step, a differential pressure calculation step for outputting a differential pressure output signal related to the differential pressure between the internal pressure and the external pressure of the cavity;
A selection step of selecting a specific pulse wave detection unit from the plurality of pulse wave detection units based on an output signal of the differential pressure calculation step;
In the selection step, the pulse wave detection unit having the largest output signal intensity of the differential pressure output signal is selected as the specific pulse wave detection unit from the plurality of pulse wave detection units,
A pulse wave measuring method, wherein a pulse wave is measured by calculating a displacement of a living body surface based on an output of the specific pulse wave detecting unit selected in the selecting step. Based on the output of the specific pulse wave detection unit selected by the selection step, when calculating the displacement of the living body surface,
A cavity internal pressure calculating step for calculating an internal pressure of the cavity based on the differential pressure and the external air pressure calculated in the specific pulse wave detection unit;
Based on the differential pressure, an air circulation mole number calculating step for calculating an air circulation mole number flowing inside and outside the cavity;
Based on the flow mole number calculated in the air flow mole number calculation step, the air mole number calculation step for calculating the air mole number in the cavity;
Based on the number of moles of air calculated in the step of calculating the number of air moles and the internal pressure of the cavity calculated in the step of calculating pressure in the cavity, a volume calculating step of calculating the volume in the cavity;
A displacement calculating step for calculating the displacement of the living body surface based on the volume in the cavity calculated by the volume calculating step;
The pulse wave measuring method according to claim 9 , further comprising: In the air flow mole number calculation step, the flow pressure mole number database corresponding to the differential pressure and the flow mole number database stored as a database according to the magnitude of the differential pressure calculated by the differential pressure calculation step. The pulse wave measuring method according to claim 10 , wherein the number of moles of air flow is extracted. The flow mole number database is generated by calculating a relationship between a pressure difference inside and outside the cavity and a flow amount of air, and calculating the air flow mole number based on the relationship and the differential pressure. The pulse wave measuring method according to claim 11 . An air temperature acquisition step of acquiring temperature information of air flowing inside and outside the cavity;
The pulse wave measurement according to any one of claims 10 to 12 , wherein in the step of calculating the number of moles of air, the number of moles of air in the cavity is calculated based on the temperature information and the number of moles of flow. Method. At least the separation step, the differential pressure calculation step, the intracavity pressure calculation step, the air flow mole number calculation step, the air mole number calculation step, the volume calculation step, and the displacement calculation step, The pulse wave measuring method according to claim 10 , further comprising: a repetitive processing step of repeatedly executing the step. The pulse wave measuring method according to claim 9, further comprising a reference pulse wave detecting step in which a volume of the cavity is not deformed by the displacement of the living body surface. The pulse wave measuring method according to claim 14 , wherein the repetitive processing step is executed every set predetermined time. In the differential pressure calculating step, each of the differential pressure output signals for each predetermined time is stored in a storage device, and the differential pressure for each predetermined time is obtained based on the stored differential pressure output signal. The pulse wave measuring method according to any one of claims 9 to 16 . The selecting step is performed after the differential pressure output signal output in the differential pressure calculating step is continuously lower than a predetermined signal strength reference value for a predetermined time. The pulse wave measuring method according to any one of claims 9 to 17 .

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