Sphygmomanometer, blood pressure measurement method, and Korotkoff sound detection device

Abstract

The present invention is provided with a diaphragm (62) which is a part of or is connected to a tube wall of an air pipe (37d) connected to a cuff so that a fluid can flow therethrough, and which is disposed so as to receive the pressure of air within the air pipe (37d) on one surface (62a). The diaphragm (62) blocks the pressure of the air in the air pipe (37d) during the pressurization or decompression of the cuff, and transmits sound in the band of Korotkoff sound among sound transmitted through the air in the air pipe (37d) from the site to be measured through the diaphragm (62). A chamber (Cm), which includes the diaphragm (62) as a part of the peripheral wall, is provided on the other surface (62b) side of the diaphragm (62), said other surface (62b) being opposite to the one surface (62a). A portion of the peripheral wall of the chamber (Cm) other than the diaphragm (62) has a sound detection device provided facing the air within the chamber (Cm).

Description

Technical Field

[0001] The present invention relates to a sphygmomanometer and a blood pressure measuring method, and more particularly to a sphygmomanometer and a blood pressure measuring method for measuring blood pressure based on Korotkoff sounds generated at a measured part. In addition, the present invention relates to a Korotkoff sound detection device included in such a sphygmomanometer for extracting Korotkoff sounds from sounds generated at a measured part. Background Art

[0002] In the past, such a Korotkoff sound detection device (and blood pressure meter) is known to have, as disclosed in the second figure of Patent Document 1 (Japanese Patent Publication No. 58-180132), a vibrating membrane (metal membrane) that vibrates by collecting sound from a cuff that is wrapped around the upper arm of a human body and pressurized, and has a mechanical resonance point in the frequency band where Korotkoff sounds exist; and a mechanism that converts the mechanical vibration of the vibrating membrane into an electrical signal. This structure is understood to be a condenser microphone. It is described in the document that the mechanical resonance characteristics of the vibrating membrane can be used to remove noise components other than Korotkoff sounds and extract only Korotkoff sounds.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 58-180132 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, the sound generated by the measured part (broadly defined as a wave propagating in an elastic medium such as air) includes, in addition to Korotkoff sounds (frequency band: about 20 Hz to 500 Hz), pulse wave vibrations of the artery passing through the measured part, namely, pressure pulse waves (frequency band: about several tens of Hz). The frequency bands of the two overlap, and the amplitude of the pressure pulse wave is larger than the amplitude of the Korotkoff sounds. Therefore, in reality, in the structure described in Patent Document 1, there is a problem that it is difficult to extract only the Korotkoff sounds from the sound generated by the measured part.

[0008] Therefore, the present invention aims to provide a blood pressure meter and a blood pressure measurement method for measuring blood pressure based on Korotkoff sounds generated at a measured part, which can extract Korotkoff sounds from the sounds generated at the measured part with a good S / N ratio (signal to noise ratio), thereby improving the accuracy of blood pressure measurement. In addition, the present invention aims to provide a Korotkoff sound detection device included in such a blood pressure meter, which extracts Korotkoff sounds from the sounds generated at the measured part with a good S / N ratio.

[0009] Technical means of solving problems

[0010] In order to solve the above-mentioned problems, the sphygmomanometer disclosed in the present invention measures blood pressure based on Korotkoff sounds generated in the measured part, and is characterized in that:

[0011] have:

[0012] A compression cuff configured to be worn on the measured part;

[0013] Pumps;

[0014] an air pipe connecting the cuff and the pump in a manner that fluid can flow;

[0015] a pressure control unit for supplying air to the cuff through the air pipe using the pump to increase the pressure, or for discharging the air from the cuff through the air pipe to reduce the pressure, in order to compress the measured part;

[0016] a diaphragm, which is a part of a tube wall of the air pipe or connected to the tube wall and is arranged in a manner to bear the pressure of the air in the air pipe on one surface, wherein the diaphragm is configured to block the pressure of the air in the air pipe during a pressurization process or a depressurization process of the cuff performed by the pressure control unit and to allow the sound of the frequency band of the Korotkoff sound transmitted from the measured part through the air in the air pipe to pass through the diaphragm,

[0017] The chamber includes the diaphragm as a part of a peripheral wall and is arranged on the other side of the diaphragm opposite to the one side, and the sound transmitted through the diaphragm is transmitted to the air occupying the chamber.

[0018] a sound detection device disposed in a portion other than the diaphragm in the peripheral wall of the chamber facing the air in the chamber, the sound detection device receiving sound that has passed through the diaphragm via the air occupying the chamber and converting the sound into an electrical signal; and

[0019] The blood pressure calculation unit calculates the blood pressure of the measurement site based on the electrical signal.

[0020] Here, “one surface” and “the other surface” of the separator refer to both surfaces having the extension of the separator.

[0021] The arrangement of the diaphragm “connected to the tube wall” of the air pipe includes, for example, an arrangement of the diaphragm connected to the tube wall of another pipe branched from the air pipe.

[0022] In the blood pressure meter disclosed in the present invention, when the compression cuff is worn on the measured part, the pressure control unit supplies air to the cuff through the air pipe to pressurize the measured part, or discharges the air from the cuff through the air pipe to reduce the pressure. During the pressurization or decompression process of the cuff by the pressure control unit, the diaphragm bears the pressure of the air in the air pipe on one side and blocks the pressure of the air in the air pipe. On the other hand, the diaphragm allows the sound of the frequency band of the Korotkoff sound transmitted from the measured part through the air in the air pipe to pass through the diaphragm. As a result, the sound that has passed through the diaphragm is transmitted to the air occupying the chamber. The sound detection device receives the sound that has passed through the diaphragm via the air occupying the chamber and converts the sound into an electrical signal. The blood pressure calculation unit calculates the blood pressure of the measured part based on the electrical signal.

[0023] Here, in the sphygmomanometer, since the diaphragm blocks the pressure of the air in the air piping, the influence of the pulse wave vibration (frequency band; about tens of Hz) of the artery, i.e., the pressure pulse wave, can be reduced from the sound generated at the measured part. Moreover, the sound detection device receives the sound that has passed through the diaphragm via the air occupying the chamber, in other words, receives it at a position separated from the diaphragm (which directly receives the pressure pulse wave). Therefore, the influence of the pressure pulse wave can be further reduced. Thus, according to the sphygmomanometer, Korotkoff sounds can be extracted from the sound generated at the measured part with a good S / N ratio. Therefore, the accuracy of blood pressure measurement can be improved.

[0024] Assuming that the chamber is sealed, during the pressurization or decompression process of the cuff, the diaphragm bends as the pressure of the air in the air piping gradually changes, and the pressure of the air in the chamber changes. If there is such a change in pressure in the air occupying the chamber, it is not preferred, for example, when the sound detection device is a condenser microphone, because the sensitivity of the microphone changes. In addition, the dynamic range of the condenser microphone needs to be equivalent to the width of the change in cuff pressure (about 0 to 300 mmHg), so the resolution of the Korotkoff sound is reduced. In addition, it also has an adverse effect on the durability and reliability of the sound detection device.

[0025] Therefore, in one embodiment of the sphygmomanometer, it is characterized in that:

[0026] A pressure relief hole is provided in a portion other than the diaphragm in the peripheral wall of the chamber, and the pressure relief hole connects the inside and outside of the chamber in a manner that fluid can flow. The pressure relief hole functions to suppress changes in the pressure of the air in the chamber from atmospheric pressure.

[0027] In the sphygmomanometer of this embodiment, a hole for pressure relief is provided in the portion other than the diaphragm in the peripheral wall of the chamber, and the hole for pressure relief connects the inside and outside of the chamber in a manner that a fluid can flow. Therefore, during the pressurization or decompression process of the cuff, the diaphragm bends as the pressure of the air in the air piping gradually changes. When the pressure of the air in the chamber is about to change, the hole for pressure relief acts in a manner to suppress the pressure of the air in the chamber from changing from atmospheric pressure. Therefore, even if the pressure of the air in the air piping changes, it is possible to prevent the pressure change (load) from adversely affecting the sensitivity, resolution, durability, and reliability of the sound detection device.

[0028] Furthermore, as the sound detection device, not only a condenser microphone but also various types of microphones such as a dynamic microphone and a MEMS (Micro Electronics Mechanical System) microphone can be used, thereby increasing the freedom of microphone selection.

[0029] If the pressure relief hole is a wide opening, noise sound can easily enter the chamber from outside the chamber through the wide opening, and thus the S / N ratio of the Korotkoff sound may decrease.

[0030] Therefore, in one embodiment of the sphygmomanometer, it is characterized in that:

[0031] The pressure relief hole has a form of an elongated pipe or an elongated groove.

[0032] In the sphygmomanometer of this embodiment, the hole for pressure relief has a form of an elongated pipe or an elongated groove. Therefore, compared with the case where the hole for pressure relief is a wide opening, noise is less likely to enter the chamber from outside the chamber. Therefore, it is possible to prevent the S / N ratio of the Korotkoff sound from being reduced due to the hole for pressure relief.

[0033] In one embodiment of the sphygmomanometer, it is characterized in that:

[0034] A sound-insulating material having air permeability and sound-insulating properties is accommodated inside the elongated pipe or the elongated groove.

[0035] Here, as the “sound insulating material having air permeability and sound insulating properties”, porous materials such as polyurethane foam are typically mentioned.

[0036] In the sphygmomanometer of this embodiment, the sound insulation material contained in the elongated pipe or the elongated groove has air permeability. Therefore, the function of the pressure relief hole to suppress the pressure change of the air in the chamber from the atmospheric pressure is not lost due to the presence of the sound insulation material. In addition, since the sound insulation material has sound insulation properties, it is difficult for noise to enter the chamber from outside the chamber through the elongated pipe or the elongated groove compared to the case where only air exists in the elongated pipe or the elongated groove. Therefore, it is possible to prevent the S / N ratio of the Korotkoff sound from being reduced due to the pressure relief hole.

[0037] In one embodiment of the sphygmomanometer, it is characterized in that:

[0038] The diaphragm is set to have a natural vibration frequency that matches the frequency band of the Korotkoff sound.

[0039] In the blood pressure meter of this embodiment, the diaphragm is set to have a natural vibration frequency that matches the frequency band of the Korotkoff sounds. Therefore, the diaphragm can selectively transmit the sound having the frequency band of the Korotkoff sounds among the sounds transmitted from the measured part through the air in the air piping. Therefore, the S / N ratio of the Korotkoff sounds can be further improved, and the accuracy of blood pressure measurement can be further improved.

[0040] In one embodiment of the sphygmomanometer, it is characterized in that:

[0041] The chamber is set to have a resonance frequency that matches the frequency band of the Korotkoff sound.

[0042] In the blood pressure meter of this embodiment, the chamber is set to have a resonance frequency that matches the frequency band of the Korotkoff sounds. Therefore, the chamber can selectively amplify the sound having the frequency band of the Korotkoff sounds among the sounds that have passed through the diaphragm. Therefore, the S / N ratio of the Korotkoff sounds can be further improved, thereby further improving the accuracy of blood pressure measurement.

[0043] In one embodiment of the sphygmomanometer, it is characterized in that:

[0044] The diaphragm is made of synthetic resin.

[0045] In the sphygmomanometer of this embodiment, the diaphragm is made of synthetic resin, so it is lighter than when it is made of metal, and it is easier to process in the manufacturing stage.

[0046] In one embodiment of the sphygmomanometer, it is characterized in that:

[0047] The sphygmomanometer includes a threshold setting unit that sets a threshold for extracting the Korotkoff sound from the electrical signal output by the sound detection device.

[0048] The blood pressure calculation unit calculates the blood pressure of the measurement site based on only the signal exceeding the threshold value among the electrical signals.

[0049] In the blood pressure meter of this embodiment, the threshold setting unit sets a threshold for extracting the Korotkoff sounds from the electrical signal output by the sound detection device. The blood pressure calculation unit calculates the blood pressure of the measured part based only on the signal exceeding the threshold in the electrical signal. Therefore, for example, background noise can be removed from the electrical signal output by the sound detection device. Therefore, the S / N ratio of the Korotkoff sounds can be further improved, thereby further improving the accuracy of blood pressure measurement.

[0050] In another aspect, the blood pressure measurement method disclosed herein uses the sphygmomanometer to measure blood pressure based on Korotkoff sounds generated at the measured part, and is characterized in that:

[0051] When the compression cuff is worn on the measured part, the pressure control unit supplies air to the cuff through the air pipe to increase the pressure, or discharges the air from the cuff through the air pipe to reduce the pressure, in order to compress the measured part.

[0052] During the process of pressurizing or depressurizing the cuff by the pressure control unit, the diaphragm receives the pressure of the air in the air pipe on one side, blocks the pressure of the air in the air pipe, and allows the sound of the frequency band of the Korotkoff sound transmitted from the measured part through the air in the air pipe to pass through the diaphragm. As a result, the sound that has passed through the diaphragm is transmitted to the air occupying the chamber.

[0053] The sound detection device receives the sound transmitted through the diaphragm via the air occupying the chamber and converts the sound into an electrical signal,

[0054] The blood pressure calculation unit calculates the blood pressure of the measurement site based on the electrical signal.

[0055] According to the blood pressure measurement method of the present disclosure, Korotkoff sounds can be extracted from the sounds generated at the measured site with a good S / N ratio, and thus the accuracy of blood pressure measurement can be improved.

[0056] In another aspect, the Korotkoff sound detection device disclosed in the present invention is included in the sphygmomanometer, and extracts Korotkoff sounds from the sounds generated by the measured part, characterized in that:

[0057] have:

[0058] a diaphragm, which is a part of a tube wall of the air pipe or connected to the tube wall and is arranged in a manner to bear the pressure of the air in the air pipe on one surface, wherein the diaphragm is configured to block the pressure of the air in the air pipe during a pressurization process or a depressurization process of the cuff performed by the pressure control unit and to allow the sound of the frequency band of the Korotkoff sound transmitted from the measured part through the air in the air pipe to pass through the diaphragm,

[0059] The chamber includes the diaphragm as a part of a peripheral wall and is arranged on the other side of the diaphragm opposite to the one side, and the sound transmitted through the diaphragm is transmitted to the air occupying the chamber.

[0060] A sound detection device is provided in a portion other than the diaphragm in the peripheral wall of the chamber so as to face the air in the chamber, and receives sound that has passed through the diaphragm via the air occupying the chamber and converts the sound into an electrical signal.

[0061] According to the Korotkoff sound detection device of the present disclosure, it is possible to extract Korotkoff sounds from the sound generated in the measured part at a good S / N ratio.

[0062] Effects of the Invention

[0063] As described above, according to the sphygmomanometer and blood pressure measurement method disclosed in the present invention, Korotkoff sounds can be extracted from the sound generated by the measured part with a good S / N ratio, thereby improving the accuracy of blood pressure measurement. In addition, according to the Korotkoff sound detection device disclosed in the present invention, Korotkoff sounds can be extracted from the sound generated by the measured part with a good S / N ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a diagram showing a block configuration of a sphygmomanometer according to one embodiment of the present invention.

[0065] Figure 2 (A) is a perspective view showing a cross-sectional structure of a Korotkoff sound detection device included in the above-mentioned sphygmomanometer. Figure 2 (B) is a diagram showing a pattern for setting the resonance frequency of the cavity included in the above-mentioned Korotkoff sound detection device.

[0066] Figure 3 (A) Figure 3 (B) Figure 3 (C) are diagrams showing various forms of a capillary tube that forms a hole for pressure relief that connects the inside and outside of the chamber so that a fluid can flow. Figure 3 (D) means Figure 3(C) is a diagram showing the verification result of noise reduction caused by accommodating a sound insulating material inside the capillary tube shown in FIG.

[0067] Figure 4 It is a diagram showing a state in which the compression cuff of the above-mentioned blood pressure monitor is worn on the upper arm as the measurement site.

[0068] Figure 5 It is a diagram showing the flow of blood pressure measurement using the above-mentioned blood pressure monitor.

[0069] Figure 6 (A) Figure 6 (B) is a diagram schematically illustrating the operation of the Korotkoff sound detection device during blood pressure measurement.

[0070] Figure 7 This is a diagram illustrating an example of a sound signal output by the Korotkoff sound detection device in the sphygmomanometer (embodiment).

[0071] Figure 8 : is a diagram illustrating an audio signal output by a Korotkoff sound detection device according to a comparative example.

[0072] Fig. 9 (A) Fig. 9 (B) are diagrams showing modified examples of the above-mentioned pressure relief holes. DETAILED DESCRIPTION

[0073] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0074] (Schematic structure of a sphygmomanometer)

[0075] Figure 1 The frame structure of a sphygmomanometer 1 according to an embodiment of the present invention is shown. The sphygmomanometer 1 generally comprises: a compression cuff (hereinafter referred to as "cuff") 20 which is wrapped around a measured part (in this example, the upper arm) and worn; and a main body 10 which is connected to the cuff 20 via an air pipe 37 so that a fluid can flow.

[0076] The cuff 20 has a bag body 21 formed by facing an outer fabric and an inner fabric in the form of an elongated belt and sewing (or welding) the peripheral edges thereof. A fluid bag 22 for compressing a measured part is accommodated inside the bag body 21 .

[0077] The main body 10 is equipped with a control unit 110, a display 50, an operation unit 52, a memory 51, a power supply unit 53, a pressure sensor 31, a pump 32, a valve 33, and a Korotkoff sound detection device 60 for extracting Korotkoff sounds from the sound generated by the measured part. In addition, the main body 10 is equipped with an A / D conversion circuit 310 that converts the analog output from the pressure sensor 31 into a digital signal, a pump drive circuit 320 that drives the pump 32, a valve drive circuit 330 that drives the valve 33, and an A / D conversion circuit 410 that converts the analog output from the Korotkoff sound detection device 60 into a digital signal. Air pipes 37a, 37b, 37c, and 37d are connected to the pressure sensor 31, the pump 32, the valve 33, and the Korotkoff sound detection device 60, respectively, so that fluid can flow. These air pipes 37a, 37b, 37c, and 37d merge into one air pipe 37 in the main body 10, and the air pipe 37 is connected to the fluid bag 22 in the cuff 20 so that the fluid can flow. Hereinafter, the air pipes 37a, 37b, 37c, and 37d are collectively referred to as the air pipe 37 as appropriate. The output of the Korotkoff sound detection device 60 is transmitted to the A / D conversion circuit 410 as an electric signal, that is, a sound signal Ks through the wiring 71.

[0078] In this example, the display 50 includes a display and an indicator, and displays predetermined information (for example, blood pressure measurement results, etc.) in response to a control signal from the control unit 110 .

[0079] The operation unit 52 inputs an operation signal according to the user's instruction to the control unit 110. In this example, the operation unit 52 includes a measurement switch 52A for receiving an instruction to start / stop blood pressure measurement, and a memory switch 52B for receiving an instruction to call up the data of the blood pressure measurement result stored in the memory 51.

[0080] The memory 51 serves as a storage unit and stores program data for controlling the sphygmomanometer 1 , setting data for setting various functions of the sphygmomanometer 1 , and data of blood pressure measurement results, etc. The memory 51 is also used as a work memory when executing a program.

[0081] The control unit 110 includes a CPU (Central Processing Unit) and controls the overall operation of the sphygmomanometer 1. Specifically, the control unit 110 functions as a pressure control unit according to a program for controlling the sphygmomanometer 1 stored in the memory 51, and controls the driving pump 32 and the valve 33 according to an operation signal from the operation unit 52. In addition, the control unit 110 functions as a threshold setting unit and a blood pressure calculation unit, calculates the blood pressure value of the measured part based on the sound signal Ks output by the Korotkoff sound detection device 60, and controls the display 50 and the memory 51. The specific method of blood pressure measurement will be described later.

[0082] The power supply unit 53 supplies power to the control unit 110, the pressure sensor 31, the pump 32, the valve 33, the display 50, the memory 51, the A / D conversion circuits 310 and 410, the pump drive circuit 320, the valve drive circuit 330, and the microphone 40 described later. The power is supplied to the microphone 40 through the wiring 71.

[0083] The pressure sensor 31 is a piezo-resistance pressure sensor in this example, receives the pressure (referred to as "cuff pressure Pc") of the cuff 20 (the fluid bag 22 in this example) through the air pipe 37, and outputs the electrical signal value based on the change in resistance caused by the piezo-resistance effect to the control unit 110 through the A / D conversion circuit 310. The control unit 110 detects the cuff pressure Pc based on the electrical signal value from the pressure sensor 31.

[0084] In order to increase the cuff pressure Pc, the pump 32 supplies air to the fluid bag 22 through the air pipe 37. The valve 33 discharges or seals the air in the fluid bag 22 through the air pipe 37, and opens and closes to control the cuff pressure Pc. The pump drive circuit 320 drives the pump 32 based on the control signal provided by the control unit 110. The valve drive circuit 330 opens and closes the valve 33 based on the control signal provided by the control unit 110.

[0085] In this example, the Korotkoff sound detection device 60 generally includes: a housing 61 in a generally short cylindrical shape; a diaphragm 62 provided to cross the housing 61; a microphone 40 as a sound detection device; and a capillary 63 having a hole for pressure relief.

[0086] Figure 2 (A) shows a cross-sectional structure of the Korotkoff sound detection device 60. The Korotkoff sound detection device 60 has a housing 61 including a lower housing 61A and an upper housing 61B. For easy understanding, Figure 2 (A) shows a longitudinal section of the housing 61 cut in half by a vertical plane. In addition, the terms "lower", "upper", "vertical" and "horizontal" described later are for convenience of explanation, and the housing 61 can be integrally arranged in any direction within the main body 10 of the sphygmomanometer 1.

[0087] The lower housing 61A includes: a cylindrical portion 61A1, which is fitted around the air pipe 37d; a plate portion 61A2, which has a substantially rectangular plate-shaped outer shape extending horizontally from the upper end of the cylindrical portion 61A1; a recessed portion 61A3, which is provided as a circular depression with a flat bottom on the upper surface of the plate portion 61A2; and an edge portion 61A4, which extends from the end edge ( Figure 2The right side of (A) is bent and extends upward. The cylindrical portion 61A1 is airtightly fitted around the air pipe 37d. The space Cd formed by the recessed portion 61A3 on the plate portion 61A2 is connected to the air pipe 37d (air pipe 37) via the cylindrical portion 61A1 so that a fluid can flow. In this example, the horizontal dimension of the plate portion 61A2 is set to about 50 mm.

[0088] The upper shell 61B includes: a substantially rectangular plate portion 61B1 extending substantially parallel to and opposite to the plate portion 61A2 of the lower shell 61A; a dome portion 61B2 protruding upward from the plate portion 61B1 in a circular dome shape; a cylindrical portion 61B3 extending upward from the approximate center of the dome portion 61B2; and an edge portion 61B4 extending from the end edge ( Figure 2 ) is bent and extends downward. In this example, the horizontal dimension of the plate portion 61B1 is set to about 50 mm, similarly to the dimension of the plate portion 61A2 of the lower shell 61A. The horizontal position and dimension of the dome portion 61B2 are substantially consistent with the horizontal position and dimension of the recess 61A3 of the lower shell 61A. In this example, the air pipe 38 is airtightly inserted into the cylindrical portion 61B3. The microphone 40 is airtightly installed at the upper end of the air pipe 38. In addition, in this example, a capillary 63 is installed in the middle of the air pipe 38. The inner circumference of the plate portion 61B1, 61B1i, the inner edge of the dome portion 61B2 and 61B1i form a space Cm (forming a chamber described later) that is connected to the microphone 40 via the cylindrical portion 61B3 and the air pipe 38 in a manner that allows fluid to flow.

[0089] Between the plate portion 61A2 of the lower case 61A and the plate portion 61B1 of the upper case 61B, a substantially circular film-shaped diaphragm 62 is provided so as to cross-cut the space Cd and the space Cm. In this example, the peripheral edge portion 62e of the diaphragm 62 is sandwiched between the plate portion 61A2 of the lower case 61A and the plate portion 61B1 of the upper case 61B. Figure 2As shown by the arrow Bs in (A), the portion other than the peripheral portion 62e in the diaphragm 62 can vibrate up and down. The peripheral portion 62e of the diaphragm 62 can also be bonded to the plate portion 61A2 of the lower shell 61A and / or the plate portion 61B1 of the upper shell 61B by an adhesive. In this example, the diaphragm 62 is composed of a polyurethane sheet (thickness 0.3 mm) as a synthetic resin. In this example, the effective radius R of the diaphragm 62 (substantially equal to the radius in the horizontal direction of the spaces Cd and Cm) is set to R=16.5 mm. Therefore, compared with the case where the diaphragm 62 is composed of metal, it is lighter and easier to process in the manufacturing stage. In addition, in this example, the natural vibration frequency of the diaphragm 62 is set to be consistent with the frequency band of Korotkoff sounds (about 20 Hz to 500 Hz). Therefore, the diaphragm 62 can selectively transmit sounds having a frequency band of Korotkoff sounds.

[0090] The edge 61A4 of the lower case 61A and the edge 61B4 of the upper case 61B are provided to facilitate the alignment of the lower case 61A and the upper case 61B with each other in a horizontal plane when the lower case 61A and the upper case 61B are assembled. Due to these edges 61A4 and 61B4, the concave portion 61A3 of the lower case 61A and the dome portion 61B2 of the upper case 61B can be easily aligned concentrically.

[0091] In this example, the upper surface 62b of the diaphragm 62, the inner peripheral edge 61B1i of the plate portion 61B1, the inner surface 61B2i of the dome portion 61B2, the cylindrical portion 61B3, and the air pipe 38 constitute a chamber (for simplicity, represented by the same reference numeral as the space Cm). In this example, the chamber Cm is set to have a resonance frequency that matches the frequency band of Korotkoff sounds (about 20 Hz to 500 Hz).

[0092] Specifically, Figure 2 (B) shows a Helmholtz resonance mode in a case where the cylindrical portion 61B3 of the upper housing 61B and the air piping 38 are omitted and the chamber Cm is directly connected to the microphone 40 in a fluid-flowable manner (in this case, Figure 1 As shown in FIG. , the capillary 63 may be directly mounted on the dome portion 61B2 of the upper housing 61B or may be formed integrally with the dome portion 61B2. Figure 2 In (B), S represents the effective area of ​​the diaphragm 62 (the area of ​​the actual vibrating part, unit: m 2 ), V represents the internal volume of chamber Cm (unit: m 3 ), L represents the equivalent neck length (unit: m). In this case, the resonance frequency f of the cavity Cm is calculated by the following mathematical formula based on the theory of Helmholtz resonance.

[0093] f=(c / 2π)(S / VL)1 / 2 …(Eq.1)

[0094] Here, c represents the speed of sound, c≈340 m / sec. In this example, based on the formula (Eq. 1), the resonance frequency f of the cavity Cm is set to match the frequency band of Korotkoff sounds (approximately 20 Hz to 500 Hz).

[0095] Therefore, the cavity Cm can selectively amplify the sound having the frequency band of Korotkoff sound among the sounds transmitted through the diaphragm 62 .

[0096] The microphone 40 receives the sound transmitted through the diaphragm 62 via the air in the occupied chamber Cm, and converts the sound into an electrical signal, namely, a sound signal Ks. The sound signal Ks mainly includes a component representing Korotkoff sound. The sound signal Ks is transmitted to the control unit 110 via the wiring 71 and the A / D conversion circuit 410 as the output of the Korotkoff sound detection device 60.

[0097] The capillary tube 63 forming the hole for pressure relief has a cylindrical shape in this example. Figure 3 As shown in (A), a hole 63o for pressure relief is provided inside the capillary 63 to connect the inside and outside of the chamber Cm so that a fluid can flow. In this example, the hole 63o is in the form of a long and narrow pipe extending straight. In this example, the axial dimension L of the capillary 63 is set to be about several mm to several cm. In addition, the inner diameter Di of the hole 63o is set to be about 0.1 mm to several mm.

[0098] During the process of pressurization or decompression of the cuff 20, the diaphragm 62 bends as the pressure of the air in the air pipe 37 (and the space Cd) gradually changes. When the pressure of the air in the chamber Cm changes, Figure 3 As shown by arrow Ai in (A), the hole 63o allows air to flow inside and outside the chamber Cm, thereby suppressing the pressure of the air in the chamber Cm from changing from the atmospheric pressure (pressure of the gas environment) Am. Therefore, even if the pressure of the air in the air pipe 37 (and the space Cd) changes, it is possible to prevent the sensitivity, resolution, durability, and reliability of the microphone 40 from being adversely affected by the pressure change (load).

[0099] Here, the hole 63o for pressure relief is in the form of a long and narrow pipe. Therefore, compared with the case where the hole 63o is a wide opening (not shown), it is difficult for noise to enter the chamber Cm from outside the chamber Cm through the hole 63o. Therefore, it is possible to prevent the S / N ratio of Korotkoff sounds from being reduced due to the hole for pressure relief. Figure 3 In the example (A), the hole 63o is straight, but it is not limited to this. Figure 3In the capillary 63B shown in (B), the hole 63oB for pressure relief provided therein is in the form of a long and thin pipe that reciprocates in a zigzag shape. In this case, as shown by the arrow AiB, the hole 63oB acts in a manner to suppress the pressure of the air in the chamber Cm from changing from the atmospheric pressure Am by allowing the air to circulate in and out of the chamber Cm. Therefore, even if the pressure of the air in the air piping 37 (and the space Cd) changes, it is possible to prevent the sensitivity, resolution, durability, reliability, etc. of the microphone 40 from being adversely affected by the pressure change (load). Moreover, Figure 3 Compared with the example (A), noise is less likely to enter the cavity Cm from the outside of the cavity Cm through the hole 63oB. Therefore, it is possible to prevent the S / N ratio of the Korotkoff sound from being reduced by the hole for pressure relaxation.

[0100] In addition, Figure 3 In the capillary 63C shown in (C), the hole 63°C for pressure relief provided therein is in the form of a long and narrow pipe extending straightly. However, in this example, a polyurethane foam 64 as a porous material is contained inside the hole 63°C as a sound insulating material having air permeability and sound insulating properties. As indicated by the arrow AiC, the polyurethane foam 64 has air permeability. Therefore, the function of the hole 63°C to suppress the change in the pressure of the air in the chamber Cm from the atmospheric pressure Am is not lost due to the presence of the polyurethane foam 64. In addition, since the polyurethane foam 64 has sound insulating properties, it is less likely for noise to enter the chamber Cm from the outside of the chamber Cm through the hole 63°C, compared to the case where only air exists inside the hole 63°C. Therefore, it is possible to further prevent the S / N ratio of the Korotkoff sound from being reduced due to the presence of the hole 63°C. For example, Figure 3 (D) shows the result of verifying the extent to which the noise in the chamber Cm is reduced by accommodating the polyurethane foam 64 inside the hole 63°C when the axial dimension L of the capillary 63C is 2 mm and the inner diameter Di of the hole 63°C is about 0.2 mm. In this example, before the polyurethane foam 64 is accommodated inside the hole 63°C (before time tx), the background noise level (peak to peak) Ap-p in the chamber Cm is about 0.11 V. In contrast, after the polyurethane foam 64 is accommodated inside the hole 63°C (after time tx), the background noise level Ap-p in the chamber Cm is reduced to about 0.02 V. In this way, it can be verified that the presence of the polyurethane foam 64 can effectively reduce the noise in the chamber Cm.

[0101] (Blood Pressure Measurement Method)

[0102] When measuring blood pressure, Figure 4 As shown, the cuff 20 is wrapped around the user's measured part (in this example, the upper arm 90) and worn (in addition, Figure 4The inner fabric is not shown in the figure for simplicity). The artery 91 passes through the measured part 90. The sound generated by the measured part 90 includes, in addition to Korotkoff sounds (frequency band; about 20 Hz to 500 Hz), pulse wave vibrations of the artery 91 passing through the measured part 90, that is, pressure pulse waves (frequency band; about several tens of Hz) dV. The sound generated by the measured part 90 is transmitted from the space Cc formed by the fluid bag 22 to the Korotkoff sound detection device 60 (space Cd) in the main body 10 through the air piping 37.

[0103] Figure 5 The flowchart shows the operation flow when the user measures blood pressure using the blood pressure monitor 1 .

[0104] When the user instructs to start measurement using the measurement switch 52A provided on the operation unit 52 of the main body 10 while the cuff 20 is worn on the measured part, the control unit 110 performs initialization ( Figure 5 Specifically, the control unit 110 initializes the processing memory area, turns off (stops) the pump 32, and performs 0 mmHg adjustment of the pressure sensor 31 (setting the atmospheric pressure to 0 mmHg) while the valve 33 is open. Figure 6 As shown in (A) , the diaphragm 62 of the Korotkoff sound detection device 60 is in a flat state.

[0105] Next, the control unit 110 functions as a pressure control unit and closes the valve 33 ( Figure 5 Then, the pump 32 is turned on (driven) via the pump driving circuit 320 to start pressurizing the cuff 20 (fluid bag 22) (step S3). That is, the control unit 110 supplies air as a fluid from the pump 32 to the fluid bag 22 in the cuff 20 through the air piping 37. In addition, the pressure sensor 31 receives the cuff pressure Pc through the air piping 37. The control unit 110 controls the pressurization speed by the pump 32 based on the output of the pressure sensor 31.

[0106] During the pressurization process, Figure 6 As shown in (B), the diaphragm 62 of the Korotkoff sound detection device 60 receives the pressure of the air in the air pipe 37 (particularly the air pipe 37d) on one surface (the surface on the space Cd side) 62a, and bends convexly toward the other surface 62b side. As a result, the pressure of the air in the air pipe 37 is blocked. In addition, when the pressure of the air in the chamber Cm changes due to the deflection of the diaphragm 62, as shown by the arrow Ai, the hole 63o for pressure relief of the capillary 63 acts to allow air to flow inside and outside the chamber Cm, thereby suppressing the pressure of the air in the chamber Cm from changing from the atmospheric pressure Am.

[0107] Then, in Figure 5In step S4, the control unit 110 determines whether the cuff pressure Pc reaches a preset value (prescribed pressure) based on the output of the pressure sensor 31. Here, the prescribed pressure can be set to, for example, 180 mmHg in a manner that sufficiently exceeds the user's expected blood pressure value, or can be set to the user's blood pressure value measured last time plus 40 mmHg. The control unit 110 continues to pressurize until the cuff pressure Pc reaches the prescribed pressure. When the cuff pressure Pc reaches the prescribed pressure ("yes" in step S4), the pump 32 is stopped (step S5). Next, the control unit 110 gradually opens the valve 33 via the valve drive circuit 330 (step S6). As a result, the cuff pressure Pc is depressurized at a substantially constant speed.

[0108] During the decompression process, Figure 6 As shown in (B), the diaphragm 62 receives the pressure of the air in the air pipe 37 on one surface 62a, blocks the pressure of the air in the air pipe 37, and vibrates as shown by the arrow Bs, so that the sound of the frequency band of Korotkoff sound passes through the diaphragm 62. As a result, the sound that has passed through the diaphragm 62 is transmitted to the air in the occupied chamber Cm. The microphone 40 receives the sound that has passed through the diaphragm 62 through the air in the occupied chamber Cm, converts the sound into an electrical signal, that is, a sound signal Ks, and outputs it through the wiring 71.

[0109] Here, since the diaphragm 62 blocks the pressure of the air in the air piping 37, the influence of the pressure pulse wave dV, which is the pulse wave vibration of the artery 91, can be reduced from the sound generated by the measured part 90. In addition, the microphone 40 receives the sound that has passed through the diaphragm 62 via the air in the occupied chamber Cm, in other words, receives the sound that has passed through the diaphragm 62 at a position separated from the diaphragm 62 (which directly receives the pressure pulse wave). Therefore, the influence of the pressure pulse wave dV can be further reduced. As a result, the noise caused by the pressure pulse wave dV can be removed from the sound generated by the measured part 90.

[0110] In addition, the diaphragm 62 is set to have a natural vibration frequency that matches the frequency band of Korotkoff sounds, and thus, it is possible to selectively transmit the sound having the frequency band of Korotkoff sounds among the sounds transmitted from the measured portion 90 through the air in the air pipe 37 (and the space Cd). Furthermore, the chamber Cm is set to have a resonance frequency that matches the frequency band of Korotkoff sounds, and thus, it is possible to selectively amplify the sound having the frequency band of Korotkoff sounds among the sounds that have transmitted through the diaphragm 62. Therefore, the Korotkoff sounds can be extracted with a good S / N ratio.

[0111] During the decompression process, Figure 5As shown in step S7 (Korotkoff sound extraction processing), the control unit 110 obtains the sound signal Ks output by the Korotkoff sound detection device 60 (microphone 40) via the A / D conversion circuit 410, and extracts a signal representing the Korotkoff sound (referred to as "Korotkoff sound signal Kc") from the sound signal Ks.

[0112] Specifically, Figure 7 The sound signal Ks output by the Korotkoff sound detection device 60 is illustrated as an example. Figure 7 The mountain-shaped curve in represents the cuff pressure Pc. In this example, the cuff pressure Pc reaches the specified pressure of 180 mmHg about 17 seconds after the start of the pressurization, and the decompression process starts from this time point. In this example, the sound signal Ks includes a plurality of pulse-shaped Korotkoff sound signals Kc that exceed the background noise level Ap-p (about 0.02 V in this example). In this example, the control unit 110 functions as a threshold setting unit, and sets a threshold TH (about 0.06 V in this example) that exceeds the background noise level Ap-p for the sound signal Ks. Then, the control unit 110 extracts only the signal exceeding the threshold TH in the sound signal Ks as the Korotkoff sound signal Kc. Thus, the background noise can be removed from the sound signal Ks. Therefore, the S / N ratio of the above-mentioned Korotkoff sound can be further improved. In addition, under the control of the control unit 110, the memory 51 stores the amplitude of the extracted Korotkoff sound signal Kc in correspondence with the time when the Korotkoff sound signal Kc is generated.

[0113] Afterwards, in Figure 5 In step S8, the control unit 110 functions as a blood pressure calculation unit, and calculates the blood pressure of the measured part based on the Korotkoff sound signal Kc stored in the memory 51. Specifically, in the above-mentioned decompression process, the cuff pressure Pc at the time when the Korotkoff sound signal Kc first appears is determined as the systolic blood pressure SYS (Systolic Blood Pressure), and the cuff pressure Pc at the time when the Korotkoff sound signal Kc last appears is determined as the diastolic blood pressure DIA (Diastolic Blood Pressure).

[0114] After the blood pressure values ​​(systolic blood pressure SYS and diastolic blood pressure DIA) are calculated in this way ("Yes" in step S9), the control unit 110 functions as a pressure control unit, turns off the pump 32, opens the valve 33, and performs control to rapidly discharge the air in the cuff 20 (fluid bag 22) (step S10). Thereafter, the control unit 110 performs control to display the calculated blood pressure value on the display 50 and to store it in the memory 51.

[0115] As described above, according to this blood pressure measurement method, Korotkoff sounds can be extracted from the sound generated by the measurement site 90 at a good S / N ratio, and thus the accuracy of blood pressure measurement can be improved.

[0116] As a comparative example, the present inventors produced a sphygmomanometer including a Korotkoff sound detection device according to the second figure of Patent Document 1 (Japanese Patent Application Laid-Open No. 58-180132). The sphygmomanometer has the same structure as the sphygmomanometer 1 except for the Korotkoff sound detection device. Figure 8 The sound signal Ks' output by the Korotkoff sound detection device is illustrated. Figure 8 In the example of FIG. 1 , the cuff pressure Pc reaches the specified pressure of 180 mmHg about 17 seconds after the start of the pressurization, and the decompression process starts from this point in time. Figure 7 The verification result of shows that the signal corresponding to the Korotkoff sound signal Kc is buried in the noise. Therefore, in this comparative example, it can be said that it is difficult to extract only the Korotkoff sound from the sound generated at the measured part.

[0117] In addition, during the above decompression process ( Figure 5 In steps S6 to S9), as Figure 6 As shown in (B), the diaphragm 62 of the Korotkoff sound detection device 60 gradually returns from the state of being convexly bent toward the other surface 62b side. Figure 6 Thus, when the pressure of the air in the chamber Cm is about to change, as shown by the arrow Ai, the hole 63o for pressure relief of the capillary 63 acts to suppress the pressure of the air in the chamber Cm from changing from the atmospheric pressure Am by allowing the air to flow inside and outside the chamber Cm.

[0118] Therefore, not only during the pressurization process ( Figure 5 In the steps S3 to S4), even in the decompression process ( Figure 5 In steps S6 to S9), the pressure of the air in the chamber Cm can also be suppressed from changing from the atmospheric pressure Am. As a result, it is possible to prevent the sensitivity, resolution, durability, and reliability of the microphone 40 from being adversely affected by the pressure change (load) of the air in the air piping 37. In addition, as the microphone 40, not only a condenser microphone can be used, but also various types of microphones such as a dynamic microphone and a MEMS (Micro Electronics Mechanical System) microphone can be used, and the freedom of microphone selection is increased.

[0119] (Variation Example)

[0120] In the above example, the holes 63o, 63oB, and 63oC for relieving the pressure in the chamber Cm are in the form of elongated pipes provided inside the capillary tubes 63, 63B, and 63C, but the present invention is not limited thereto. Fig. 9 The elongated grooves 41d, 61B2d or Fig. 9The shape of the elongated groove 61B1d shown in (B) is shown in FIG. Fig. 9 (A) Fig. 9 In (B), the same reference numerals are given to structural members corresponding to those already described, and duplicate descriptions are omitted.

[0121] exist Fig. 9 (A) Fig. 9 In the example of the Korotkoff sound detection device 60', 60" shown in (B), relative to Figure 2 In the example of (A), the cylindrical portion 61B3 of the upper housing 61B and the air piping 38 are omitted. Instead, a through hole 61B2o is provided at the top of the dome portion 61B2 of the upper housing 61B, and further, a commercially available MEMS microphone 40A having a flat, substantially rectangular shape is mounted in close contact with the top surface of the dome portion 61B2 via the substrate 41 having the through hole 41o. The chamber Cm is connected to the microphone 40A via the through hole 61B2o of the dome portion 61B2 and the through hole 41o of the substrate 41 in a manner that allows fluid to flow. Therefore, the microphone 40A can receive the sound that has passed through the diaphragm 62 via the air occupying the chamber Cm, and convert the sound into an electrical signal, namely, a sound signal Ks, to output. In addition, the size of the microphone 40A in the plane direction (the direction in which it extends flatly) is several mm square.

[0122] exist Fig. 9 In the example of the Korotkoff sound detection device 60' shown in (A), the hole for relieving the pressure of the chamber Cm is composed of an elongated groove 61B2d formed on the top surface of the dome portion 61B2 of the upper shell 61B and an elongated groove 41d formed at a corresponding position in the lower surface (the surface in contact with the dome portion 61B2) of the substrate 41 so as to overlap with the elongated groove 61B2d. During the pressurization or decompression process of the cuff 20, the diaphragm 62 flexes as the pressure of the air in the air pipe 37 (and the space Cd) gradually changes. When the pressure of the air in the chamber Cm changes, as shown in FIG. Fig. 9 As shown by arrows AiD in (A), these elongated grooves 41d and 61B2d function to prevent the pressure of the air in the chamber Cm from changing from the atmospheric pressure Am by allowing air to flow inside and outside the chamber Cm via the through hole 61B2o of the dome portion 61B2. Therefore, even if the pressure of the air in the air pipe 37 (and the space Cd) changes, it is possible to prevent the sensitivity, resolution, durability, and reliability of the microphone 40A from being adversely affected by the pressure change (load). In addition, one of the elongated grooves 41d and 61B2d may be omitted.

[0123] exist Fig. 9In the example of the Korotkoff sound detection device 60″ shown in (B), the hole for relieving the pressure of the chamber Cm is composed of an elongated groove 61B1d formed on the lower surface (the surface in contact with the diaphragm 62) of the plate portion 61B1 of the upper shell 61B. During the pressurization or decompression process of the cuff 20, the diaphragm 62 bends as the pressure of the air in the air pipe 37 (and the space Cd) gradually changes. When the pressure of the air in the chamber Cm changes, as shown in FIG. Fig. 9 As shown by arrows AiE in (B), the elongated groove 61B1d allows air to flow inside and outside the chamber Cm, thereby suppressing the pressure of the air in the chamber Cm from changing from the atmospheric pressure Am. Therefore, even if the pressure of the air in the air pipe 37 (and the space Cd) changes, it is possible to prevent the sensitivity, resolution, durability, and reliability of the microphone 40A from being adversely affected by the pressure change (load).

[0124] In addition, you can also Fig. 9 The elongated grooves 41d, 61B2d, Fig. 9 The elongated groove 61B1d shown in (B) contains a sound insulating material (for example, polyurethane foam) having air permeability and sound insulating properties. This can prevent the S / N ratio of the Korotkoff sound from being reduced by the elongated groove 41d, 61B2d or 61B1d.

[0125] In addition, the blood pressure measurement by the sphygmomanometer 1 may be performed during the pressurization process instead of the depressurization process.

[0126] In addition, the measured part is not limited to the upper arm, and may be an upper limb other than the upper arm such as the wrist or a lower limb such as the ankle.

[0127] The above embodiments are merely illustrative, and various modifications can be made without departing from the scope of the present invention. The above multiple embodiments can be established independently, or each embodiment can be combined with each other. In addition, each feature in different embodiments can also be established independently, or the features in different embodiments can be combined with each other.

[0128] Description of reference numerals:

[0129] 1. Blood pressure monitor

[0130] 10 Main Body

[0131] 20 Cuff

[0132] 22 Fluid Bags

[0133] 31. Pressure sensor

[0134] 32 Pumps

[0135] 33 valve

[0136] 40, 40A Microphone

[0137] 41 substrate

[0138] 41d, 61B1d, 61B2d Long and narrow groove

[0139] 60, 60′, 60″ Korotkoff sound detection device

[0140] 62 Diaphragm

[0141] 63, 63A, 63B, 63C Capillaries

[0142] 63o, 63oB, 63℃ Hole for pressure relief

[0143] 64 Polyurethane foam

Claims

1. A sphygmomanometer for measuring blood pressure based on Korotkoff sounds generated at a measured part, characterized in that: have: A compression cuff configured to be worn on the measured part; Pumps; an air pipe connecting the cuff and the pump in a manner that fluid can flow; a pressure control unit for supplying air to the cuff through the air pipe using the pump to increase the pressure, or for discharging the air from the cuff through the air pipe to reduce the pressure, in order to compress the measured part; a diaphragm, which is a part of a tube wall of the air pipe or connected to the tube wall and is arranged in a manner to bear the pressure of the air in the air pipe on one surface, wherein the diaphragm is configured to block the pressure of the air in the air pipe during a pressurization process or a depressurization process of the cuff performed by the pressure control unit and to allow the sound of the frequency band of the Korotkoff sound transmitted from the measured part through the air in the air pipe to pass through the diaphragm, The chamber includes the diaphragm as a part of a peripheral wall and is arranged on the other side of the diaphragm opposite to the one side, and the sound transmitted through the diaphragm is transmitted to the air occupying the chamber. a sound detection device, disposed in a portion other than the diaphragm in the peripheral wall of the chamber facing the air in the chamber, the sound detection device receiving sound that has passed through the diaphragm via the air occupying the chamber and converting the sound into an electrical signal; as well as The blood pressure calculation unit calculates the blood pressure of the measurement site based on the electrical signal.

2. The sphygmomanometer according to claim 1, characterized in that: A pressure relief hole is provided in a portion other than the diaphragm in the peripheral wall of the chamber, and the pressure relief hole connects the inside and outside of the chamber in a manner that fluid can flow. The pressure relief hole functions to suppress changes in the pressure of the air in the chamber from atmospheric pressure.

3. The sphygmomanometer according to claim 2, characterized in that: The pressure relief hole has a form of an elongated pipe or an elongated groove.

4. The sphygmomanometer according to claim 3, characterized in that: A sound-insulating material having air permeability and sound-insulating properties is accommodated inside the elongated pipe or the elongated groove.

5. The sphygmomanometer according to any one of claims 1 to 4, characterized in that: The diaphragm is set to have a natural vibration frequency that matches the frequency band of the Korotkoff sound.

6. The sphygmomanometer according to any one of claims 1 to 4, characterized in that: The chamber is set to have a resonance frequency that matches the frequency band of the Korotkoff sound.

7. The sphygmomanometer according to any one of claims 1 to 4, characterized in that: The diaphragm is made of synthetic resin.

8. The sphygmomanometer according to any one of claims 1 to 4, characterized in that: The sphygmomanometer includes a threshold setting unit that sets a threshold for extracting the Korotkoff sound from the electrical signal output by the sound detection device. The blood pressure calculation unit calculates the blood pressure of the measurement site based on only the signal exceeding the threshold value among the electrical signals.

9. A method for measuring blood pressure, using the sphygmomanometer according to claim 1, to measure blood pressure based on Korotkoff sounds generated at a measured part, characterized in that: When the compression cuff is worn on the measured part, the pressure control unit supplies air to the cuff through the air pipe to increase the pressure, or discharges the air from the cuff through the air pipe to reduce the pressure, in order to compress the measured part. During the process of pressurizing or depressurizing the cuff by the pressure control unit, the diaphragm receives the pressure of the air in the air pipe on one side, blocks the pressure of the air in the air pipe, and allows the sound of the frequency band of the Korotkoff sound transmitted from the measured part through the air in the air pipe to pass through the diaphragm. As a result, the sound that has passed through the diaphragm is transmitted to the air occupying the chamber. The sound detection device receives the sound transmitted through the diaphragm via the air occupying the chamber and converts the sound into an electrical signal, The blood pressure calculation unit calculates the blood pressure of the measurement site based on the electrical signal.

10. A Korotkoff sound detection device, the Korotkoff sound detection device being included in the sphygmomanometer according to claim 1, and extracting Korotkoff sounds from the sounds generated by the measured part, characterized in that: have: a diaphragm, which is a part of a tube wall of the air pipe or connected to the tube wall and is arranged in a manner to bear the pressure of the air in the air pipe on one surface, wherein the diaphragm is configured to block the pressure of the air in the air pipe during a pressurization process or a depressurization process of the cuff performed by the pressure control unit and to allow the sound of the frequency band of the Korotkoff sound transmitted from the measured part through the air in the air pipe to pass through the diaphragm, The chamber includes the diaphragm as a part of a peripheral wall and is arranged on the other side of the diaphragm opposite to the one side, and the sound transmitted through the diaphragm is transmitted to the air occupying the chamber. A sound detection device is provided in a portion other than the diaphragm in the peripheral wall of the chamber so as to face the air in the chamber, and receives sound that has passed through the diaphragm via the air occupying the chamber and converts the sound into an electrical signal.

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