Sensor unit

Abstract

To provide a sensor unit capable of easily calculating a pulse wave propagation speed as compared to a case where a sensor is attached to a plurality of parts of a body surface.SOLUTION: A sensor unit includes: a flexible support body; a core material that is mounted to at least a part of the flexible support body; a long sensor that is arranged in the core material; an acquisition part that acquires a plurality of output waves from an output signal derived from a heart rate, the output signal being emitted from the sensor when a shape change of at least one part of a body surface is transmitted to the sensor; and a calculation part that calculates a pulse wave propagation speed from a difference in a reference time of the output wave calculated from arithmetic processing on the plurality of output waves.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a sensor unit that calculates pulse wave velocity. [Background technology]

[0002] Patent Document 1 discloses a technique for measuring pulse wave velocity by attaching sensors to multiple parts of the body surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-164301 Summary of the Invention [Problem to be solved by the invention]

[0004] The task of attaching sensors to the body surface becomes more time-consuming as the number of sensors to be attached increases. An object of the present disclosure is to provide a sensor unit that can calculate the pulse wave velocity more easily than when sensors are attached to multiple parts of the body surface. [Means for solving the problem]

[0005] The sensor unit of the first aspect comprises a flexible support, a core material attached to at least a portion of the flexible support, a long sensor disposed in the core material, an acquisition unit that acquires multiple output waves from an output signal derived from a heartbeat that is emitted from the sensor when shape fluctuations of at least one part of the body surface are transmitted to the sensor, and a calculation unit that calculates pulse wave velocity from the difference in reference times of the output waves calculated by arithmetic processing of the multiple output waves.

[0006] The sensor unit of the second aspect has the same configuration as the first aspect, and is arranged so that the sensor intersects with the direction in which the blood vessels of the subject run.

[0007] The sensor unit of the third aspect has the same configuration as the second aspect, but in addition, the sensor is wound around the core material.

[0008] The sensor unit of the fourth aspect has the same configuration as the third aspect, and further has a structure in which a plurality of the core materials around which the sensors are wound are attached in parallel to the flexible support body.

[0009] The sensor unit of the fifth aspect has the same configuration as the second aspect, but the surface of the core material is curved.

[0010] The sensor unit of the sixth aspect has the same configuration as the fifth aspect, but further has a depression formed on the surface of the core material.

[0011] The sensor unit of a seventh aspect has the same configuration as the first aspect, and further has the calculation section calculates the difference in the reference time from the phase difference of the plurality of output waves and the frequencies of the plurality of output waves.

[0012] The sensor unit of an eighth aspect has the same configuration as the first aspect, and further, the sensor includes an organic piezoelectric material.

[0013] The sensor unit of the ninth aspect has the same configuration as the eighth aspect, and further, the organic piezoelectric material contains a helical chiral polymer having optical activity.

[0014] The sensor unit of a tenth aspect has the same configuration as the ninth aspect, and further, the helical chiral polymer contains polylactic acid.

[0015] The sensor unit of an eleventh aspect has the same configuration as the first aspect, and further comprises: a long conductor; and a long piezoelectric element wound spirally in one direction around the conductor.

[0016] A sensor unit according to a twelfth aspect has the same configuration as that of the first aspect, and further, the sensor is a string-like sensor having a coaxial line structure.

[0017] The sensor unit of the thirteenth aspect has the same configuration as the first aspect, and the multiple output waves include at least one of a vibration signal related to a vibration signal obtained by extracting vibration components in a first frequency range from a signal obtained by removing DC components from a source signal directly output from the sensor, and then passing the extracted signal through a band-pass filter of a second frequency range, and a direct signal related to a direct signal obtained by passing the source signal directly through a band-pass filter of the second frequency range.

[0018] The sensor unit of the 14th aspect has the same configuration as the 13th aspect, and the second frequency range is from twice the upper limit of a predetermined heart rate to twice the lower limit of the predetermined heart rate.

[0019] A sensor unit according to a fourteenth aspect has the same configuration as the first aspect, and further, the plurality of output waves include a fundamental wave, a subharmonic, or a harmonic of a heart sound measured by the sensor. [Effects of the Invention]

[0020] The sensor unit according to the present disclosure can calculate the pulse wave velocity more easily than when sensors are attached to multiple parts of the body surface. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 2 is a diagram showing a schematic configuration of a sensor unit according to the present embodiment. [Figure 2] FIG. 1 is a diagram illustrating a schematic configuration of a calculation device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a schematic diagram of a mounting body in the sensor unit of FIG. 1. [Figure 4] FIG. 4 is a schematic diagram showing the attachment of FIG. 3 from a different angle. [Figure 5] 1 is a diagram showing a schematic configuration of a sensor according to an embodiment of the present invention; [Figure 6] 4 is a schematic diagram showing the position where the attachment of FIG. 3 is attached. FIG. [Figure 7] 4 is a schematic diagram showing a state in which the wearable device of FIG. 3 is worn on the wrist. FIG. [Figure 8] FIG. 8 is a schematic diagram showing the state of FIG. 7 from a different angle. [Figure 9A] FIG. 2 is a schematic diagram showing a first example of a state in which a sensor is attached to a core material. [Figure 9B] FIG. 10 is a schematic diagram showing a second example of a state in which a sensor is attached to a core material. [Figure 9C] FIG. 10 is a schematic diagram showing a third example of a state in which a sensor is attached to a core material. [Figure 9D] FIG. 10 is a schematic diagram showing a first modified example of a method for fixing a sensor to a core material. [Figure 9E] FIG. 10 is a schematic diagram showing a second modified example of a method for fixing a sensor to a core material. [Figure 9F] FIG. 2 is a schematic diagram of the core materials arranged side by side. [Figure 9G] FIG. 10 is a schematic diagram showing a first modified example of the shape of the core material. [Figure 9H] FIG. 10 is a schematic diagram showing a second modified example of the shape of the core material. [Figure 10] FIG. 2 is a schematic diagram showing an example of a main force wave according to the present embodiment. [Figure 11] 10 is a flowchart showing the flow of a calculation process performed by the sensor unit according to the present embodiment. [Figure 12] 4 is a graph showing the results of measuring a direct signal and a vibration signal measured by the sensor unit of the first embodiment. [Figure 13] 10 is a graph showing the results of measuring a direct signal and a vibration signal measured by the sensor unit of the second embodiment. [Figure 14A] FIG. 10 is a schematic diagram of a sensor of a comparative example. [Figure 14B] FIG. 14B is a schematic diagram showing the sensor of FIG. 14A from the direction of the arrow. [Figure 15] 10 is a graph showing the results of measuring a direct signal and a vibration signal measured by a sensor unit of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0022] The sensor unit 10 according to an embodiment of the present disclosure will be described below. Note that reference numerals commonly used in multiple drawings indicate common components or parts even if no specific explanation is given for each drawing. Furthermore, the dimensions and proportions of each part shown in the drawings do not necessarily correspond to the dimensions and proportions of the actual product. Furthermore, the dimensional relationships and proportions between the drawings may differ.

[0023] 1 is a diagram showing a schematic configuration of a sensor unit 10. As shown in FIG. 1, the sensor unit 10 includes a calculation device 20, a wearable body 50 having a sensor 30, and an AD converter 40.

[0024] The AD converter 40 converts the analog signal input by the sensor 30 into a digital signal. Then, the AD converter 40 outputs the converted digital signal to the calculation device 20. The AD converter 40 is provided with an input terminal for inputting the analog signal, and the sensor 30 is electrically connected to the input terminal.

[0025] Next, a description will be given of the hardware configuration of the calculation device 20. In this embodiment, a personal computer is used as the calculation device 20. However, the present invention is not limited to this example. For example, the calculation device 20 may be any device capable of calculating the pulse wave velocity, such as a server or a smartphone.

[0026] 2, the calculation device 20 includes a CPU 21 (Central Processing Unit), a ROM 22 (Read Only Memory), a RAM 23 (Random Access Memory), a storage unit 24, and an input / output I / F (Interface) 27. Each component is connected to each other via a bus 28 so as to be able to communicate with each other.

[0027] The CPU 21 is a central processing unit that executes various programs and controls each part. That is, the CPU 21 reads programs from the ROM 22 or the storage unit 24 and executes the programs using the RAM 23 as a work area. The CPU 21 controls each of the above components and performs various arithmetic processing in accordance with the programs recorded in the ROM 22 or the storage unit 24.

[0028] The ROM 22 stores various programs and various data. The RAM 23 serves as a working area for temporarily storing programs or data.

[0029] The storage unit 24 is configured by a storage device such as a hard disk drive (HDD), a solid state drive (SSD), or a flash memory, and stores various programs and various data.

[0030] The storage unit 24 stores a calculation program 24A for causing the CPU 21 of the calculation device 20 to function as a functional configuration shown in Fig. 11, which will be described later. When executing the calculation program 24A, the calculation device 20 executes processing based on the calculation program 24A using the hardware resources shown in Fig. 2.

[0031] The input / output I / F 27 is an interface for communicating with the AD converter 40, etc. The AD converter 40 is connected to the calculation device 20 of this embodiment via the input / output I / F 27.

[0032] 2 has, as functional components, an acquisition unit 21A and a calculation unit 21B, as shown in Fig. 1. Each functional component is realized by the CPU 21 reading and executing a calculation program 24A stored in the storage unit 24. The acquisition unit 21A and the calculation unit 21B will be described in detail later.

[0033] 3 and 4 are schematic diagrams of the wearing body 50 in the sensor unit of Fig. 1. The wearing body 50 includes a flexible support 51, a core material 52 attached to at least a portion of the flexible support 51, and an elongated sensor 30 disposed on the core material 52. In other words, the wearing body 50 is formed as a wristband.

[0034] Flexible support 51 is made of a cloth band. A roughly semi-cylindrical core material 52 is attached to one location on flexible support 51 along the width direction of flexible support 51, with long sensor 30 wound around core material 52. By winding sensor 30 around core material 52 in this way, sensor 30 comes into contact with the subject's body surface at multiple locations.

[0035] The sensor 30 according to this embodiment is a sensor that generates an electrical displacement in response to strain caused by an external force. Examples of the electrical displacement include an amount of charge, a voltage, and a resistance. The sensor 30 is, for example, a piezoelectric sensor. Specifically, the sensor 30 measures an output signal derived from the heart from one part of the body surface.

[0036] 5, the sensor 30 according to this embodiment is a string-like sensor including a long conductor 30A, a long piezoelectric body 30B spirally wound in one direction around the conductor 30A, and an adhesive layer (not shown). Note that the sensor 30 may also include an external conductor disposed around the outer periphery of the piezoelectric body 30B, in addition to the conductor 30A, the piezoelectric body 30B, and the adhesive layer. The provision of the external conductor enables electrostatic shielding, thereby suppressing voltage changes in the conductor 30A due to the influence of external static electricity.

[0037] The adhesive layer is disposed between the conductor 30A and the piezoelectric body 30B. As a result, in the sensor 30 according to this embodiment, even if tension is applied in the longitudinal direction of the sensor 30, the relative positions of the piezoelectric body 30B and the conductor 30A do not shift.

[0038] The conductor 30A and the piezoelectric element 30B are coaxially arranged in this order from the center outward, so that the sensor 30 is a string-like sensor with a coaxial line structure.

[0039] The conductor 30A is preferably a signal line conductor. The signal line conductor is a conductor for efficiently detecting an electrical signal from the piezoelectric body 30B. Specifically, the signal line conductor is a conductor for detecting a voltage signal (charge signal) corresponding to the applied tension when tension is applied to the sensor 30.

[0040] The conductor 30A is preferably a good electrical conductor, and can be, for example, a copper wire, an aluminum wire, a stainless steel wire, a metal wire coated with an insulating film, a carbon fiber, a resin fiber integrated with a carbon fiber, a tinsel wire, an organic conductive material, etc. A tinsel wire is a fiber with copper foil wound in a spiral.

[0041] 5, the piezoelectric element 30B is spirally wound in one direction along the outer peripheral surface of the conductor 30A from one end to the other at a spiral angle β1 so as to have no gaps. The "spiral angle β1" refers to the angle between the axial direction AX of the conductor 30A and the arrangement direction of the piezoelectric element 30B relative to the axial direction of the conductor 30A.

[0042] 5, the piezoelectric body 30B is wound counterclockwise around the conductor 30A. Specifically, when the sensor 30 is viewed from one axial end of the conductor 30A (the right end in the case of FIG. 5), the piezoelectric body 30B is wound counterclockwise from the front side to the back side of the conductor 30A. The method of winding the piezoelectric body 30B around the conductor 30A is not limited to the example described above. For example, the piezoelectric body 30B may be wound clockwise around the conductor 30A, or may be wound to wrap around the conductor 30A.

[0043] Furthermore, the piezoelectric body 30B is long (for example, ribbon-shaped, wire-shaped, or thin-film-shaped) from the viewpoint of ease of winding. However, this is not limiting. The piezoelectric body 30B may have any shape as long as it can be wound around the conductor 30A.

[0044] Furthermore, the piezoelectric element 30B according to this embodiment includes an organic piezoelectric material. The organic piezoelectric material according to this embodiment includes a helical chiral polymer having optical activity. A helical chiral polymer having optical activity refers to a polymer having a helical molecular structure and having molecular optical activity. Examples of helical chiral polymers having optical activity include polylactic acid-based polymers, synthetic polypeptides, cellulose derivatives, polypropylene oxide, and poly(β-hydroxybutyric acid). The helical chiral polymer according to this embodiment includes polylactic acid (PLA).

[0045] 5, the main orientation direction of the optically active helical chiral polymer contained in the piezoelectric body 30B is indicated by a double-headed arrow D2. That is, the main orientation direction of the optically active helical chiral polymer and the arrangement direction of the piezoelectric body 30B (the length direction of the piezoelectric body 30B) are substantially parallel to each other.

[0046] The term "substantially parallel" refers to a relationship in which the main orientation direction of the optically active helical chiral polymer and the arrangement direction of the piezoelectric body 30B can be seen as parallel at a glance. Specifically, "substantially parallel" refers to a relationship in which the angle between the main orientation direction of the optically active helical chiral polymer and the arrangement direction of the piezoelectric body 30B is less than 10 degrees.

[0047] The organic piezoelectric material may also contain an optically active polypeptide. An optically active polypeptide refers to a polypeptide that has an asymmetric carbon atom and has a bias in the abundance of optical isomers. From the viewpoint of piezoelectricity and strength, the optically active polypeptide preferably has a β-sheet structure. Examples of optically active polypeptides include optically active animal proteins. Examples of animal proteins include fibroin and spider silk protein. Examples of fibers made of animal proteins include silk and spider silk.

[0048] Organic piezoelectric materials may also include polyvinylidene fluoride (PVDF), silk fibers, and the like.

[0049] 3 and 4 is attached to the human body. A blood vessel (artery A) runs between bone B and tendon T on the thumb side, on the wrist side of crease W at the boundary between the palm and wrist. The running direction of this blood vessel and the longitudinal direction of flexible support body 51 coincide when wearing attachment 50 on the wrist.

[0050] 7 and 8 are schematic diagrams showing the state in which the wearing body 50 of FIG. 3 is worn on the wrist. That is, the ridge line of the core material 52 is pressed against the running direction of the blood vessels shown in FIG. 6, and then the flexible support body 51 is wrapped around the wrist to wear the wearing body 50 on the wrist. At this time, the running direction of the sensor 30 wound around the core material 52 intersects with the running direction of the blood vessels. It is desirable to wind the sensor 30 around the core material 52 so that the running direction of the sensor 30 forms an angle of 90° or close to 90° with the running direction of the blood vessels.

[0051] 9A to 9C are schematic diagrams showing examples of a state in which sensor 30 is attached to core material 52. Core material 52 has a semi-cylindrical shape, with the surface that comes into contact with the human body being a convex curved surface and the surface that comes into contact with flexible support 51 being a flat surface. Core material 52 may be made of a material with a relatively low elastic modulus (e.g., 10 MPa) such as low-resilience urethane resin, or may be made of a material with a relatively high elastic modulus (e.g., 1.3 GPa) such as acrylic resin. The elastic modulus of core material 52 may be in the range of 5 MPa to 300 GPa. Attaching sensor 30 to such core material 52 increases the amplitude of the signal obtained by sensor 30, which is expected to improve noise resistance.

[0052] 9A, the sensor 30 is preferably wound so that the running direction is perpendicular to the longitudinal direction of the core material 52. Alternatively, as shown in FIG. 9B, the sensor 30 may be wound around the core material 52 by folding back at the side edge 31. Furthermore, as shown in FIG. 9C, the sensor 30 may be attached in a state where it is embedded in the core material 52.

[0053] The sensor 30 may simply be wound around the surface of the core material 52, or may be fixed to the surface of the core material 52 with adhesive tape 32 as shown in Fig. 9D, or may be sewn to the surface of the core material 52 with thread 33 as shown in Fig. 9E. Furthermore, as shown in Fig. 9F, a plurality of core materials 52 (two in the figure) around which the sensor 30 is wound may be attached in parallel to the flexible support body 51. The sensors 30 attached to the two core materials 52 may be a single wire, or separate sensors 30 may be attached to each core material 52 to extract two independent signal systems.

[0054] As shown in FIG. 9G, the elastic modulus can be reduced by providing a cavity 53 in the core material 52. Alternatively, as shown in FIG. 9H, a plurality of depressions 54 may be provided along the longitudinal direction on the surface of the core material 52. By wrapping the linear sensor 30 around the depressions 54 as shown in FIG. 9A or 9B, the amount of physical change in the sensor 30 can be increased by the amount of the depressions 54, which is expected to make the sensor 30 more susceptible to distortion due to vibration. Alternatively, the sensor 30 can be embedded in the depressions 54, which can reduce the discomfort felt when worn on the wrist.

[0055] 1 acquires a plurality of output waves related to an output signal derived from the heart, which is measured from the body surface by the sensor 30. In other words, the acquisition unit 21A acquires a plurality of output waves from the output signal derived from the heartbeat, which is emitted from the sensor 30 when a shape change of at least one part of the body surface is transmitted to the sensor 30.

[0056] In this embodiment, a vibration signal and a direct signal are applied as the multiple output waves. The vibration signal is a wave related to a vibration signal obtained by further passing an SCG (Seismocardiogram) signal, which is obtained by extracting vibration components in a first frequency range from a source signal wave directly output from the sensor 30 and removing the DC component, through a band-pass filter of a second frequency range. For example, a moving average filter is used to remove the DC component from the source signal. The direct signal is a wave related to a direct signal obtained by directly passing the source signal through a band-pass filter of the second frequency range.

[0057] In this embodiment, the first frequency range is a frequency range that is predetermined by a user or administrator of the calculation device 20. For example, the first frequency range is from 4 [Hz] to 11 [Hz]. Note that the first frequency range is different from the second frequency range.

[0058] In this embodiment, the second frequency range is set to a value between twice the upper limit of a predetermined heart rate and twice the lower limit of the predetermined heart rate. For example, if the predetermined heart rate is set to a value between 40 and 150 beats per minute (specifically, 0.67 and 2.50 beats per second), the second frequency range is set to a value between 1.34 [Hz] and 5.00 [Hz]. However, this is not limiting. A frequency range previously set by a user or administrator of the calculation device 20 may also be used as the second frequency range.

[0059] The multiple output waves are not limited to vibration signals and direct signals. For example, the multiple output waves may include the fundamental wave, subharmonics, or harmonics of the heart sounds measured by the sensor 30. In this case, for example, the acquisition unit 21A acquires the fundamental wave, subharmonics, or harmonics of the heart sounds, and the vibration signal or direct signal. In other words, the multiple output waves may include at least one of the vibration signal and the direct signal.

[0060] The calculation unit 21B, which is a functional configuration of the CPU 21 of the calculation device 20 shown in FIG. 1, calculates the pulse wave velocity from the difference between the reference times of the multiple output waves (in this embodiment, the vibration signal and the direct signal) acquired by the acquisition unit 21A by performing arithmetic processing.

[0061] Specifically, calculation unit 21B calculates a phase difference ΔP between the vibration signal and the direct signal by cross-spectral analysis, cross-correlation analysis, or the like. Then, calculation unit 21B calculates the difference between the reference times of the vibration signal and the direct signal from the phase difference ΔP and the frequencies f of the vibration signal and the direct signal. Specifically, calculation unit 21B calculates the difference between the reference times of the vibration signal and the direct signal by dividing the phase difference ΔP by the angular velocity 2πf calculated from the frequency f. That is, in this embodiment, the reference time is the time when the vibration signal and the direct signal reach their peak values, or the time when the vibration signal and the direct signal reach their extreme values. However, this is not limited to this example. The reference time may also be the time when the vibration signal and the direct signal reach an inflection point, or the like.

[0062] Note that the calculation unit 21B may calculate the difference between the reference times of the vibration signal and the direct signal by passing the vibration signal and the direct signal through a frequency filter using a moving average method or the like. In this case, a high-pass filter, a low-pass filter, a band-pass filter, or the like may be applied as the frequency filter, or a filter other than these filters that makes the characteristics of the vibration signal and the direct signal easier to understand may also be applied.

[0063] FIG. 10 shows an example of an output wave when the sensor 30 measures the output signal for three seconds. In FIG. 10, the vertical axis represents the magnitude of the output signal, and the horizontal axis represents time. The top row of FIG. 10 shows the output wave related to the source signal, the second row from the top of FIG. 10 shows the output wave related to the SCG signal, the third row from the top of FIG. 10 shows the vibration signal, and the bottom row of FIG. 10 shows the direct signal. In FIG. 10, the double arrows indicate the difference in reference time between the vibration signal and the direct signal.

[0064] Calculation unit 21B calculates the pulse wave velocity from the calculated difference between the reference times. In this embodiment, the pulse wave velocity is determined to be inversely proportional to the difference between the reference times. For example, calculation unit 21B calculates the pulse wave velocity by dividing the distance L from the measurement point of sensor 30 to the heart by the difference between the reference times. However, this is not a limitation. It is sufficient that the pulse wave velocity is determined to be slower the greater the difference between the reference times and faster the smaller the difference between the reference times.

[0065] Here, the difference in reference time between the vibration signal and the direct signal is considered to reflect the difference in speed at which vibrations caused by heartbeats in the first frequency range and the second frequency range travel through the body. Specifically, the difference in reference time between the vibration signal and the direct signal is considered to reflect the difference in time it takes for the vibration signal and the direct signal to reach the measurement point of the sensor 30, which is caused by the difference in speed.

[0066] Specifically, the vibration signal propagates as a compression wave (in other words, a P wave) that propagates regardless of the type of tissue, such as bone, muscle, fat, and body fluid. On the other hand, the direct signal is thought to be caused by the propagation of the torsion of the tissue itself. Specifically, the direct signal is a wave that propagates as deformation of the arterial wall, and is thought to be a torsion wave (in other words, an S wave) that appears as a change in the volume of the blood vessel at the measurement point. Therefore, the phase difference between the vibration signal and the direct signal, i.e., the difference in the reference time between the vibration signal and the direct signal, is thought to be related to the change in the propagation time of the direct signal due to the stiffness of the blood vessel.

[0067] Therefore, the relationship between the phase difference Lag between the vibration signal and the direct signal and the pulse wave propagation time PTT was investigated using the vibration signal and direct signal measured every 10 seconds and the time from the R wave of the electrocardiogram to the peak of the direct signal. The relationship between the phase difference Lag and the pulse wave propagation time PTT was found to be expressed by equation (1). In equation (1), the correlation coefficient is 0.5. The pulse wave propagation time PTT is the value obtained by dividing the distance L from the measurement point of the sensor 30 to the heart by the pulse wave velocity. Therefore, it was found that if the acquisition unit 21A can acquire multiple clear output waves, the calculation unit 21B can calculate the pulse wave velocity of the blood vessels from the difference in propagation velocity due to the frequency of the output signal.

[0068] PTT = 223 + 0.47 × Lag (1)

[0069] The calculation unit 21B may calculate the pulse wave transit time PTT using the time from the time of the first heart sound acquired from the sensor 30 to the reference time of the direct signal as a variable. The calculation unit 21B may then calculate the pulse wave velocity by dividing the distance L by the pulse wave transit time PTT. Specifically, the calculation unit 21B calculates the pulse wave transit time PTT using equation (2). The pre-ejection time is the time from the closure of the mitral valve to the start of ejection into the aorta.

[0070] PTT = Reference time of direct signal - (Time of first heart sound + Pre-ejection time) - (Distance L / Speed ​​of sound in tissue) (2)

[0071] The calculation unit 21B calculates the relative blood pressure level from the calculated pulse wave velocity. The unit of the relative blood pressure level in this embodiment is not limited to [mmHg], which is a common unit of blood pressure measurement. In this embodiment, the relative blood pressure level is determined to be proportional to the pulse wave velocity. This is because, when arteriosclerosis, a cause of hypertension, occurs, the pulse wave is not absorbed by the vascular wall, and the pulse wave velocity becomes faster. Also, in a person without hypertension, the blood vessels are elastic, and the pulse wave is absorbed by the vascular wall, so the pulse wave velocity becomes relatively slow. However, this is not limited to this example. The relative blood pressure level may be determined to be higher as the pulse wave velocity increases and lower as the pulse wave velocity decreases. Note that the calculation unit 21B may also calculate the vascular age, the relative level of arteriosclerosis, and the like from the calculated pulse wave velocity.

[0072] 11 is a flowchart showing the flow of calculation processing performed by the calculation device 20. The calculation processing is performed by the CPU 21 reading out the calculation program 24A from the storage unit 24, expanding it in the RAM 23, and executing it. Note that the calculation processing corresponds to processing executed by a computer according to the calculation method according to this embodiment.

[0073] 11, the CPU 21 acquires a plurality of output waves. In this embodiment, the CPU 21 acquires a vibration signal and a direct signal derived from the heart, which are measured by the sensor 30 from the body surface.

[0074] In step S102, the CPU 21 calculates the phase difference ΔP between the vibration signal and the direct signal. In this embodiment, the CPU 21 calculates the phase difference ΔP by cross-spectral analysis, cross-correlation analysis, or the like.

[0075] In step S103, CPU 21 calculates the difference between the reference times of the vibration signal and the direct signal from the phase difference ΔP and the frequency f. In this embodiment, CPU 21 calculates the difference between the reference times of the vibration signal and the direct signal by dividing the phase difference ΔP by the angular velocity 2πf calculated from the frequency f.

[0076] In step S104, the CPU 21 calculates the pulse wave velocity from the difference between the reference times. In this embodiment, the CPU 21 calculates the pulse wave velocity by dividing the distance L by the difference between the reference times.

[0077] In step S105, the CPU 21 calculates the relative blood pressure level from the pulse wave velocity. In this embodiment, the CPU 21 calculates the relative blood pressure level so that it is proportional to the pulse wave velocity. Then, the calculation process ends.

[0078] In the above embodiment, the calculation device 20 calculates the relative level of blood pressure from the pulse wave velocity. However, this is not limiting. The calculation device 20 may calculate only the pulse wave velocity without calculating the relative level of blood pressure.

[0079] In the above embodiment, the CPU 21 did not output the calculated pulse wave velocity and the relative height of blood pressure. However, this is not limited to this example. For example, if the calculation device 20 has a display unit such as a liquid crystal display, the CPU 21 may display at least one of the calculated pulse wave velocity and the relative height of blood pressure on the display unit. Furthermore, the CPU 21 may output at least one of the calculated pulse wave velocity and the relative height of blood pressure to a display device, a speaker, or the like.

[0080] Furthermore, the calculation process executed by the CPU 21 after reading the software (program) in the above embodiment may be executed by various processors other than a CPU. Examples of such processors include programmable logic devices (PLDs) whose circuit configuration can be changed after fabrication, such as field-programmable gate arrays (FPGAs), and dedicated electrical circuits, such as application-specific integrated circuits (ASICs), which are processors with circuit configurations specifically designed to execute specific processes. The calculation process may be executed by one of these various processors, or by a combination of two or more processors of the same or different types (e.g., multiple FPGAs, or a combination of a CPU and an FPGA). The hardware structure of these various processors is, more specifically, an electrical circuit that combines circuit elements such as semiconductor devices.

[0081] In the above embodiment, the calculation program 24A is pre-stored (installed) in the storage unit 24, but the present invention is not limited to this. The calculation program 24A may be provided in a form recorded on a recording medium such as a CD-ROM (Compact Disk Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), or a USB (Universal Serial Bus) memory. The calculation program 24A may also be downloaded from an external device via a network. [Example]

[0082] FIG. 12 is a graph showing the direct signal (dashed line) and vibration signal (solid line) measured by the sensor unit 10 according to the first embodiment. In this embodiment, a low-resilience urethane resin with an elastic modulus of 10 MPa was used as the material for the core material 52, and the sensor 30 was wound around this as shown in FIG. 9A and attached to a flexible support body 51 to form the attachment body 50. As a result, a phase difference was observed between the direct signal and the vibration signal, suggesting that blood pressure estimation is possible. Furthermore, since the signal amplitude was larger than in the comparative example (see FIG. 15) described below, improved noise resistance is also expected.

[0083] FIG. 13 is a graph showing the direct signal (dashed line) and vibration signal (solid line) measured by the sensor unit 10 according to the second embodiment. In this embodiment, an acrylic resin with an elastic modulus of 1.3 GPa was used as the material for the core material 52, and the sensor 30 was wound around this as shown in FIG. 9A and attached to a flexible support 51 to form the attachment 50. As a result, a phase difference was also observed between the direct signal and the vibration signal, suggesting that blood pressure estimation is possible. Furthermore, since the elastic modulus of the core material 52 in this embodiment was greater than that of the first embodiment, the signal amplitude was smaller than that of the first embodiment. However, the amplitude was larger than that of the comparative example (see FIG. 15), which will be described later, and therefore improved noise resistance is expected.

[0084] 14A and 14B are schematic diagrams showing the shape of sensor 30 according to a comparative example. Note that Fig. 14B shows Fig. 14A from the direction of the arrow. In the comparative example, core material 52 was not used, and sensor 30 was fixed to substrate 60 so as to run along it as shown in Fig. 14B, and this was attached to flexible support 51 to be used as mounting body 50.

[0085] Figure 15 is a graph showing the direct signal (dashed line) and vibration signal (solid line) measured by the sensor unit 10 according to this comparative example. A phase difference is observed between the direct signal and the vibration signal in the comparative example, so it appears possible to estimate blood pressure. However, due to the absence of the core material 52, the signal amplitude is smaller than in the examples, suggesting weaker noise resistance.

[0086] As described above, the sensor unit 10 of the present disclosure is an integrated unit in which the sensor 30 is wound around the core material 52, and does not directly measure pressure mechanically using the sensor. Furthermore, the sensor unit 10 of the present disclosure measures pressure by contacting the sensor 30 integrated with the core material 52 with the artery, without directly attaching the sensor 30 to the body surface, and can therefore measure pressure even over clothing.

[0087] Furthermore, since strain is detected by the core material 52 around which the sensor 30 is wound, the amplitude of the signal can be increased, the signal / noise ratio is improved, and improved noise resistance can also be expected. [Explanation of symbols]

[0088] 10 Sensor Unit 21A Acquisition Department 21B Calculation part 30 sensors 51 Flexible support 52 Core material 54 hollow

Claims

1. a flexible support; a core material attached to at least a portion of the flexible support; an elongated sensor disposed in the core material; an acquisition unit that acquires a plurality of output waves from an output signal derived from a heartbeat, the output signal being emitted from the sensor when a shape change in at least one part of the body surface is transmitted to the sensor; a calculation unit that calculates a pulse wave velocity from a difference between reference times of the output waves calculated by arithmetic processing of the plurality of output waves; A sensor unit comprising:

2. The sensor unit according to claim 1 , wherein the sensor is disposed in the core material so as to intersect with the direction in which the blood vessels of the subject run.

3. The sensor unit according to claim 2 , wherein the sensor is wound around the core material.

4. 4. The sensor unit according to claim 3, wherein a plurality of the core members around which the sensors are wound are attached in parallel to the flexible support member.

5. The sensor unit according to claim 2 , wherein the surface of the core material is formed as a curved surface.

6. 6. The sensor unit according to claim 5, wherein a depression is formed in the surface of the core material.

7. The sensor unit according to claim 1 , wherein the calculation section calculates the difference in the reference time from a phase difference between the plurality of output waves and a frequency of the plurality of output waves.

8. The sensor unit of claim 1 , wherein the sensor comprises an organic piezoelectric material.

9. The sensor unit according to claim 8 , wherein the organic piezoelectric material includes a helical chiral polymer having optical activity.

10. The sensor unit according to claim 9 , wherein the helical chiral polymer comprises polylactic acid.

11. The sensor A long conductor; a long piezoelectric body wound spirally in one direction around the conductor; The sensor unit of claim 1 , comprising:

12. 2. The sensor unit according to claim 1, wherein the sensor is a string-like sensor having a coaxial line structure.

13. The plurality of output waves are: a vibration signal obtained by extracting a vibration component in a first frequency range from a source signal directly output from the sensor and removing a DC component from the source signal, and then passing the extracted signal through a band-pass filter in a second frequency range; and a direct signal obtained by directly passing the source signal through a band-pass filter of the second frequency range; and The sensor unit according to claim 1 , comprising at least one of:

14. 14. The sensor unit according to claim 13, wherein the second frequency range is from twice the upper limit of a predetermined heart rate to twice the lower limit of the predetermined heart rate.

15. The sensor unit of claim 1 , wherein the plurality of output waves includes a fundamental, a subharmonic, or a harmonic of a heart sound measured by the sensor.

16. The sensor unit according to claim 1 , wherein the pulse wave velocity is determined to be inversely proportional to the difference between the reference times.

17. The sensor unit according to claim 1 , wherein a computer executes a process for calculating a relative level of blood pressure from the pulse wave velocity.

Images