JP2012152372A - Blood pressure measurement device and blood pressure measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure blood pressure without being affected by environmental sound, in a blood pressure measurement device.SOLUTION: A cuff 150 of a sphygmomanometer is provided with a piezoelectric element 200. In the blood pressure measurement, the cuff 150 is wound around the arm A of a measured person such that the piezoelectric element 200 is positioned on an artery. The sphygmomanometer determines the blood pressure of the measured person based on a change of an output signal of the piezoelectric element 200.

Description

  The present invention relates to a blood pressure measurement device and a blood pressure measurement method, and more particularly, to a blood pressure measurement device and a blood pressure measurement method in which an air bag is wound around a measurement site and compressed during blood pressure measurement.

  In general, there are two blood pressure measurement methods: an oscillometric method and a K sound measurement method. In the oscillometric method, air is sent into an air bag enclosed in a cuff wound around the arm of the measurement subject, and blood pressure is calculated from the pressure pulse wave information of the measurement subject detected in the cuff. In the K sound measurement method, blood pressure is calculated based on Korotkoff sound (K sound) measured in the vicinity of an artery on the downstream side of the cuff (air bag).

  In the blood pressure measurement device of the K sound measurement system, a microphone for measuring K sound is provided on the downstream side of the cuff. When blood pressure is measured, air is sent into the air bag, and after the artery is closed, the air bag is gradually decompressed. Then, in the decompression process, a K sound that causes blood flow to collide with the artery wall is measured.

  For example, Patent Document 1 (Japanese Patent Publication No. 4-70011) and Patent Document 2 (Japanese Patent Application Laid-Open No. Sho 62-148641) are known as blood pressure measuring devices based on the K sound measurement method.

  In Patent Document 1, a plurality of microphones (K sound sensors) are installed in the arm circumferential direction on the downstream side of the cuff, and the output of the K sound sensor showing the largest output is selected. Thus, even when the cuff is wound around the arm in the circumferential direction, the K sound in the artery wall can be measured by any of the plurality of microphones, and blood pressure can be measured.

  In Patent Document 2, a metal thin plate having a size larger than the microphone in the arm circumferential direction is installed downstream of the cuff. The microphone is placed in contact with the metal thin plate. As a result, even when the cuff is wound in the circumferential direction of the arm and the microphone is moved away from the position corresponding to the artery wall, the K sound in the artery wall is transmitted to the microphone through the metal thin plate, so that the K sound can be measured. Blood pressure can be measured.

  In the blood pressure measurement device described above, environmental sounds other than the K sound, such as a cuff sound due to the body movement of the measurement subject, may be input to the K sound sensor in the microphone for detecting the K sound. And when the volume of the input environmental sound is large, the blood pressure may not be measured accurately depending on the detection output of the K sound sensor.

  In order to avoid such inconvenience, Patent Document 3 (Japanese Patent Laid-Open No. 61-247430) discloses a microphone (C sound microphone) for detecting a sound (C sound) generated in the cuff and a K sound. A technique for measuring blood pressure by separating the C sound from the sound detected by the K sound microphone and using the sound detected by the C sound microphone from the sound detected by the K sound microphone is disclosed. Yes.

Japanese Patent Publication No. 4-70011 Japanese Patent Laid-Open No. 62-148641 JP-A 61-247430

  However, with the technique disclosed in Patent Document 3, it is possible to separate the sound generated in the cuff from the sound detected by the K sound microphone, but separate the environmental sound generated outside the cuff. I could not. Therefore, when the volume of the environmental sound generated outside the cuff is high, it is difficult to accurately measure the K sound, and accurate blood pressure measurement may not be possible.

  The present invention has been conceived in view of such circumstances, and an object of the present invention is to enable a blood pressure measurement device to measure blood pressure without being affected by environmental sound.

  The blood pressure measurement device according to the present invention has a cuff that presses the measurement site of the measurement subject by being wound, a control unit that controls the pressure in the cuff, and a piezoelectric effect corresponding to the distortion of the surface of the measurement site. And a determining means for determining the blood pressure of the person to be measured based on a change in the output signal of the piezoelectric element due to a change in the shape of the piezoelectric element.

  The blood pressure measurement method according to the present invention is a blood pressure measurement method using a blood pressure measurement device, and the blood pressure measurement device distorts the surface of the measurement site on a cuff that presses the measurement site of the measurement subject. And a blood pressure of the measurement subject is determined based on a change in voltage of the piezoelectric element due to a change in shape of the piezoelectric element.

  According to the present invention, in the blood pressure measurement device, the blood pressure of the measurement subject is determined based on the change in shape of the piezoelectric element provided in the cuff according to the distortion of the surface of the measurement site.

  Thereby, the blood of the measurement subject can be measured without being affected by the environmental sound.

It is a perspective view which shows the external appearance of the blood pressure measuring device (blood pressure meter) of the 1st Embodiment of this invention. It is a figure which shows the state which expand | deployed the cuff of FIG. It is a figure which shows the state by which the cuff of FIG. 1 was wound around the upper arm part of the left arm of a to-be-measured person, and was being fixed. It is sectional drawing of the cuff along the IV-IV line shown in FIG. It is a figure which shows typically the hardware constitutions of the blood pressure meter of FIG. It is a figure which shows an example of the change of the surface potential of a piezoelectric element with respect to the change of the cuff pressure in the sphygmomanometer of FIG. It is a figure for demonstrating the volume of a Korotkoff sound with respect to the change of the cuff pressure at the time of blood-pressure measurement, and the voltage change of a piezoelectric element. It is a flowchart of the blood-pressure measurement process performed in the sphygmomanometer of FIG. It is a figure which shows typically the cross section of the cuff in the blood pressure meter of the 2nd Embodiment of this invention. It is a figure which shows typically the cross section of the cuff in the blood pressure meter of the 3rd Embodiment of this invention. It is a figure which shows typically the block configuration of the blood pressure meter of the 3rd Embodiment of this invention. It is a figure for demonstrating the effect of fixing of the piezoelectric element by the air bag provided in the blood pressure meter of the 3rd Embodiment of this invention. It is sectional drawing of the cuff of the comparative example for demonstrating the effect shown in FIG. It is a figure for contrasting and explaining the blood pressure measurement based on a Korotkoff sound, and the blood pressure measurement based on the detection output of a piezoelectric element. It is a figure for demonstrating the specific structure of a piezoelectric element. It is a figure which shows the structure of the blood pressure meter of a comparative example.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same.

[First Embodiment]
(Structure of blood pressure measuring device)
FIG. 1 is a perspective view showing an external appearance of a blood pressure measurement device (hereinafter referred to as “blood pressure monitor”) according to the present embodiment.

  Referring to FIG. 1, blood pressure monitor 100 mainly includes an apparatus main body 110 and a cuff 150. The apparatus main body 110 includes a display unit 114 and an operation unit 115. The display unit 114 displays the measurement result of the blood pressure value, the measurement result of the pulse wave number, and the like so as to be visible using a numerical value, a graph, or the like. For example, a liquid crystal panel is used as the display unit 114. The operation unit 115 is provided with a power button, a measurement start button, and the like, for example.

  The cuff 150 is intended to be wound around the upper arm of the left arm of the measurement subject, and has a belt-like outer shape. The cuff 150 is an air bag (air bag 151 shown in FIGS. 2 to 4) as a fluid bag for compressing the upper arm, and a bag shape as an exterior member for winding and fixing the air bag 151 around the upper arm. And a cover body 161. The air bag 151 is accommodated in a space provided inside the bag-shaped cover body 161. The detailed structure of the cuff 150 will be described later. In the present embodiment, the air bag 151 constitutes a measurement fluid bag.

  The cuff 150 and the apparatus main body 110 are connected by an air pipe 140 as a connection pipe. The air tube 140 is made of a flexible tube, one end is connected to a blood pressure measurement air system component 131 (see FIG. 5) provided in the apparatus main body 110 described later, and the other end is the air bag 151 of the cuff 150 described above. It is connected to the.

  FIG. 2 is a view showing a state where the cuff 150 is unfolded. FIG. 3 is a diagram illustrating a state in which the cuff 150 is wound around and fixed to the upper arm portion of the left arm of the measurement subject. FIG. 4 is a cross-sectional view of the cuff 150 taken along the line IV-IV shown in FIG.

  In blood pressure monitor 100 of the present embodiment, piezoelectric element 200 is provided in bag-shaped cover body 161. Then, when measuring blood pressure, the cuff 150 is wound around the arm A of the measurement subject so that the piezoelectric element 200 (a part) is positioned on the artery. For example, a mark indicating the position is attached to the bag-shaped cover body 161, and the person to be measured can refer to the mark so that the subject is positioned on the cuff 150 so that the piezoelectric element 200 is positioned on the artery. Can be wrapped around arm A.

  The piezoelectric element 200 does not need to be provided in the bag-like cover body 161 as long as it can detect distortion based on blood flow on the surface of the arm A, and is provided outside the bag-like cover body 161. Moreover, even if it is fixed with respect to the bag-shaped cover body 161, it may be provided so that attachment or detachment is possible.

  The blood pressure monitor 100 closes the artery by increasing the internal pressure of the air bag 151, and then gradually depressurizes the air bag 151, and the strain of the living body that occurs when blood flows through the artery during the decompression process, It is detected as a change in surface potential that occurs in the piezoelectric element 200. First, the piezoelectric element 200 outputs a surface potential of a piezo film (a piezo film 2001 described later) included in the piezoelectric element 200 as an output signal.

  The sphygmomanometer 100 determines the blood pressure of the measurement subject based on the change in the surface potential of the piezoelectric element 200 (the amplitude of the surface potential). The piezoelectric element 200 is preferably a thin film-like element. This is because when the cuff 150 is wound around the measurement site such as the arm A as shown in FIG. 3, the piezoelectric element 200 can be satisfactorily fitted to the measurement site.

  It is considered that the piezoelectric element 200 can be appropriately determined in an environment where the sphygmomanometer 100 is used. In addition, as an example, the dimension in the winding direction with respect to the measurement site of the cuff 150 may be about 3 to 6 cm, for example, and the dimension in the direction intersecting with the winding direction (the direction of the IV-IV line in FIG. 2). For example, about 1 to 3 cm is conceivable. Such a dimension is an example, and when the cuff 150 is wound around the measurement site, it can fit well to the measurement site, and the biological distortion caused by the blood flow in the arteries of the human body can be reduced. The size of the piezoelectric element 200 is not limited to this as long as it can be detected.

  In the present embodiment, as an example of the piezoelectric element 200, the effective length 29.9mm in the winding direction of the cuff 150, the effective length 12.19mm in the width direction (IV-IV line direction in FIG. 2), and the thickness A 0.23 mm piezo film made by MSI (Tokyo Sensor) is used. FIG. 15 is a diagram for explaining a specific configuration of the piezoelectric element 200. FIG. 15A is a plan view of the piezoelectric element, and FIG. 15B is a view for explaining a longitudinal section of the piezoelectric element 200.

  Referring to FIGS. 15A and 15B, a piezoelectric element 2001 having a piezoelectric effect is disposed inside the piezoelectric element. The capacitance of the piezo film 2001 changes when the outer shape of the piezo film 2001 is distorted according to the distortion caused by the blood flow of the living body to which the cuff 150 is attached. In the piezo film 2001, two terminal portions (terminal portions 2001A and 2001B) are formed mainly as shown in FIG. Since the terminal portion is connected to an electric circuit in the apparatus main body 110, the sphygmomanometer 100 detects a distortion of the measurement site due to blood flow by examining a change in the voltage of the electric circuit.

  In the piezoelectric element 200, as shown mainly in FIG. 15B, silver paint 2002 is applied to the upper and lower sides of the piezo film 2001, respectively, and a protective layer 2003 is formed on one surface of the piezo film. In addition, a protective film such as a resin is disposed on the other surface.

  The longitudinal dimension of the piezo film 2001 is 7.14 mm for the terminal portion described above, and 29.93 mm for the portion other than the terminal portion (effective length). The width of the piezoelectric film is 12.19 mm, and the length of the piezoelectric element 200 is 41.40 mm, the width is 15.25 mm, and the thickness is 0.23 mm.

  Returning to FIG. 4, in the cuff 150, the air bag 151 is located in the region R <b> 1 and the piezoelectric element 200 is located in the region R <b> 2 on the surface where the cuff 150 contacts the arm A. That is, the air bag 151 and the piezoelectric element 200 are arranged so that the cuff 150 does not overlap with the surface that comes into contact with the arm A which is an example of the measurement site. As a result, the distortion due to the displacement of the air bag 151 in the pressure reducing process of the air bag 151 is prevented from being transmitted to the piezoelectric element 200 as much as possible.

  In FIG. 4, the blood vessel 300 of the measurement subject is shown, and the direction of blood flow from the central side to the peripheral side of the measurement subject in the blood vessel 300 is indicated by an arrow BF1. In the cuff 150, the piezoelectric element 200 is provided adjacent to one side of the air bag 151 in a direction (IV-IV line direction) intersecting with the winding direction of the cuff 150. Thereby, as mainly shown in FIG. 3, at the time of blood pressure measurement, the piezoelectric element 200 can be installed in the cuff 150 on the downstream side with respect to the air bag 151 with respect to the arrow BF1. With such an arrangement, when the pressure inside the air bag 151 is increased to close the artery of the measurement subject, the pulsation in the artery upstream of the air bag 151 affects the change in the surface potential of the piezoelectric element 200. Can be avoided as much as possible.

  In the cuff 150, a cushion material 201 is disposed between the air bag 151 and the piezoelectric element 200. Thereby, it is comprised so that the distortion | strain in the pressure reduction process etc. of the air bag 151 may have no influence on the detection output of the piezoelectric element 200 as much as possible. In other words, the displacement of the air bladder 151 is absorbed by the cushion material 201, so that the transmission of the displacement to the piezoelectric element 200 is intended to be avoided. In addition, as a material of the cushioning material 201, for example, urethane foam, neosponge, coil spring, and leaf spring (copper phosphate, SUS) can be employed.

  Further, the cushion material 201 is fixed to the bag-shaped cover body 161. Thereby, when the cuff 150 is wound around the measurement site, the piezoelectric element 200 is more closely fixed to the measurement site by the cushion material 201. Therefore, the distortion due to the blood flow at the measurement site is more reliably transmitted to the piezoelectric element 200, whereby the distortion at the measurement site is more reliably reflected in the change in the surface potential of the piezoelectric element 200.

(Hardware configuration of blood pressure monitor)
FIG. 5 is a diagram schematically illustrating a hardware configuration of the sphygmomanometer 100.

  Referring to FIG. 5, blood pressure measurement air system component 131 for supplying or discharging air to / from air bag 151 contained in cuff 150 through air tube 140 is provided inside apparatus main body 110 of sphygmomanometer 100. Is provided. The air system component 131 for blood pressure measurement includes a pressure sensor 132 which is a pressure detecting means for detecting the pressure in the air bladder 151, and a pump 134 and a valve 135 for inflating / deflating the air bladder 151. In addition, an oscillation circuit 125, a pump drive circuit 126, and a valve drive circuit 127 are provided inside the apparatus main body 110 in association with the blood system component for blood pressure measurement 131.

  Further, the apparatus main body 110 stores a CPU (Central Processing Unit) 122 for centrally controlling and monitoring each part, a program for causing the CPU 122 to perform a predetermined operation, and various information such as a measured blood pressure value. The memory unit 123, the display unit 114 for displaying various information including blood pressure measurement results, the operation unit 115 operated to input various instructions for measurement, the CPU 122, and power to each functional block. A power supply unit 124 for supply is installed.

  The CPU 122 processes various signals from the blood pressure determination unit 122B functioning as a determination unit for determining the blood pressure value of the measurement subject based on the detection output from the piezoelectric element 200, the piezoelectric element 200, and the like. A signal processing unit 122A that functions as processing means is included. The CPU 122 realizes these functions, for example, by executing a program stored in the memory unit 123 (or a recording medium that is detachable from the apparatus main body 110).

  The pressure sensor 132 detects the pressure in the air bladder 151 (hereinafter, appropriately referred to as “cuff pressure”), and outputs a signal corresponding to the detected pressure to the oscillation circuit 125. The pump 134 supplies air to the air bladder 151. The valve 135 is opened and closed based on a signal from the CPU 122 when maintaining the pressure in the air bag 151 or discharging the air in the air bag 151. The oscillation circuit 125 outputs a signal having an oscillation frequency corresponding to the output value of the pressure sensor 132 to the CPU 122. The pump drive circuit 126 controls the drive of the pump 134 based on a control signal given from the CPU 122. The valve drive circuit 127 performs opening / closing control of the valve 135 based on a control signal given from the CPU 122.

  The apparatus main body 110 includes an amplifier 211 connected to the piezoelectric element 200 (terminal portions 2001A and 2001B) and an A / D (Analog / Digital) conversion circuit 212. The amplifier 211 appropriately amplifies the voltage value output from the piezoelectric element 200 and outputs the amplified voltage value to the A / D conversion circuit 212. The A / D conversion circuit 212 converts the analog signal introduced from the amplifier 211 into a digital signal and inputs the digital signal to the CPU 122 (signal processing unit 122A).

(Detection output of piezoelectric element)
FIG. 6 is a diagram illustrating an example of a change in the surface potential of the piezoelectric element 200 with respect to a change in the cuff pressure in the sphygmomanometer 100. In FIG. 6, the surface potential of the piezoelectric element 200 is indicated by data D1, and the cuff pressure is indicated by data D2.

  At the time of blood pressure measurement, the cuff pressure is increased to a pressure target pressure PM (predetermined pressure) at a constant speed (so that the increasing pressure per unit time is constant), and then the constant speed. The pressure is lowered to a specific pressure (for example, 30 mmHg). Here, the pressurization target value is a pressure higher than the blood pressure generally assumed as the systolic blood pressure. The specific pressure is a pressure lower than the blood pressure generally assumed as the diastolic blood pressure. The cuff pressure shown in FIG. 6 is a detection output of the pressure sensor 132 and reflects pulsation in the blood flow.

  In the process in which the cuff pressure decreases from the pressure PM, the amplitude of the surface potential (data D1) of the piezoelectric element 200 starts increasing when the cuff pressure becomes a pressure corresponding to the systolic blood pressure of the person to be measured. It increases with a decrease in cuff pressure, and decreases after taking a local maximum. Then, when the cuff pressure is reduced to the diastolic blood pressure of the measurement subject, thereafter, the amplitude of the voltage output from the piezoelectric element 200 becomes substantially constant.

  In the sphygmomanometer 100, the amplitude of the surface potential of the piezoelectric element 200 is measured in a state where the cuff pressure is adjusted to a pressure (for example, 30 mmHg) sufficiently lower than the pressure generally assumed as the diastolic blood pressure of the measurement subject, The amplitude is acquired as a reference.

  Note that the reference may be acquired by measuring the amplitude of the surface potential of the piezoelectric element 200 detected in the process in which the cuff pressure is reduced from the pressure PM. In this case, the reference needs to be acquired until the cuff pressure is set to a pressure that is considered to be sufficiently larger than the pressure generally assumed as the systolic blood pressure.

  In the sphygmomanometer 100, the CPU 122 detects the amplitude of the surface potential of the piezoelectric element 200 in the process in which the cuff pressure decreases from the pressure PM, and applies the cuff pressure when the amplitude exceeds the reference amplitude described above. Determined as the systolic blood pressure of the measurer. In addition, the CPU 122 further detects the amplitude of the surface potential of the piezoelectric element 200 even in the process where the cuff pressure further decreases. Then, the cuff pressure at which the amplitude is equal to or less than the reference amplitude is determined as the diastolic blood pressure of the measurement subject.

In FIG. 6, the amplitude acquired as a reference is indicated as V ₀ by the lines L1 and L2.

  Here, the blood pressure measured by the piezoelectric element 200 is compared with the blood pressure measured by the Korotkoff sound measurement performed conventionally.

  FIG. 7 is a diagram for explaining the volume of the Korotkoff sound (hereinafter referred to as “K sound” as appropriate) and the voltage change of the piezoelectric element with respect to the change in the cuff pressure during blood pressure measurement.

  First, in FIG. 7A, the time change of the cuff pressure is schematically shown. FIG. 7A shows a state in which the cuff pressure is controlled to increase at a constant speed to a pressure PM that is a pressurization target value and then decrease at a constant speed. FIG. 7B is a diagram schematically showing a temporal change in the volume of the Korotkoff sound detected by the microphone in the sphygmomanometer (sphygmomanometer 100X in FIG. 16) equipped with a microphone instead of the piezoelectric element 200. is there. Note that the change in volume in FIG. 7 (B) corresponds to the change in cuff pressure shown in FIG. 7 (A). In FIG. 16, blood pressure monitor 100X includes a microphone 100Y.

  As shown in FIG. 7B, when the cuff pressure is lowered after being set to PM, the volume of the K sound suddenly increases when the cuff pressure is lowered to a certain pressure. Then, as the cuff pressure decreases, the sound volume gradually increases, and after showing a maximum value, when the cuff pressure decreases to a certain pressure, the sound volume rapidly decreases.

  In general blood pressure measurement, the cuff pressure when the volume of the K sound suddenly increases in the process of decreasing the cuff pressure is determined as the systolic blood pressure of the measurement subject. Further, the cuff pressure when the cuff pressure further decreases and the volume of the K sound suddenly decreases is determined as the diastolic blood pressure.

  FIG. 7C shows a change in the surface potential of the piezoelectric element 200 corresponding to a change in the cuff pressure (FIG. 7A) in the sphygmomanometer 100. Note that the data in FIG. 7C is obtained in order that the output of the piezoelectric element 200 (surface potential of the piezo film 2001) shown as the data D1 in FIG. 6 cuts noise caused by the movement of the human body. Corresponds to a signal processed by cutting a signal having a frequency equal to or higher than (for example, 200 Hz).

As shown in FIG. 7C, the amplitude of the surface potential of the piezoelectric element 200 has a predetermined value (the value of V _{0 in} FIG. 7C) in the initial process when the cuff pressure decreases from the pressure PM. I'm taking it. In the systolic blood pressure described above, the amplitude of the surface potential of the piezoelectric element 200 increases rapidly. Then, the amplitude of the surface potential of the piezoelectric element 200 gradually increases as the cuff pressure decreases, shows a maximum value, and then rapidly decreases when the cuff pressure exceeds the diastolic blood pressure of the measurement subject. V ₀ is obtained.

  As understood from FIG. 7, the surface potential of the piezoelectric element 200 changes in the cuff pressure decreasing process as described above, with the systolic blood pressure being the boundary, and the diastolic blood pressure is the same as the volume of the K sound. The behavior changes at the border. Thereby, it can be said that measurement of the systolic blood pressure and the diastolic blood pressure of the measurement subject is possible based on the change in the surface potential of the piezoelectric element 200.

In the present embodiment, V ₀ is acquired as a reference. In the process of decreasing the cuff pressure, the cuff pressure when the detected amplitude becomes larger than a certain value with respect to V ₀ is determined as the systolic blood pressure. Thereafter, the reduction of the cuff pressure is continued, and the cuff pressure when the difference between the measured surface potential of the piezoelectric element 200 and the V ₀ becomes a specific value or less is determined as the diastolic blood pressure.

(Blood pressure measurement process)
FIG. 8 is a flowchart of the blood pressure measurement process of the sphygmomanometer 100. Hereinafter, blood pressure measurement processing executed in the sphygmomanometer 100 will be described with reference to FIG.

  Referring to FIG. 8, when an operation signal corresponding to the power SW is received by pressing a power switch (hereinafter referred to as “power SW”) of operation unit 115 (step S <b> 10), CPU 122 Each part is initialized (step S20).

  Then, the CPU 122 receives an operation signal when the user selection switch of the operation unit 115 is pressed (step S30), and the measurement switch (hereinafter referred to as “measurement SW”) of the operation unit 115 is pressed. When the operation signal is received (step S40), the CPU 122 preliminarily pressurizes the air bag 151 by supplying a predetermined amount of air to the air bag 151 (step S50). In this preliminary pressurization, for example, the air bag 151 is pressurized to the above-described specific pressure (for example, 30 mmHg).

Then, the CPU 122 acquires a reference (V _{0 in} FIGS. 6 and 7) of the amplitude of the piezoelectric element 200 at that time (step S60).

  Next, the CPU 122 pressurizes the air bladder 151 until the internal pressure reaches the pressure PM described above (steps S70 to S80). When CPU 122 determines that the internal pressure of air bag 151 has reached the above-described pressure PM (YES in step S80), CPU 122 starts depressurization of air bag 151 in step S90.

  Then, the CPU 122 executes a process for determining the blood pressure of the measurement subject by appropriately processing the change in the surface potential output from the piezoelectric element 200 in the decompression process of the air bladder 151. If it is determined that the blood pressure of the measurement subject has been determined (YES in step S110), the blood pressure is displayed on the display unit 114 (step S120). Then, the CPU 122 opens the valve 135 for a time sufficient for the internal pressure of the air bag 151 to be equal to the atmospheric pressure, and then closes the valve 135 to end the blood pressure measurement process.

  In sphygmomanometer 100 according to the present embodiment, as described with reference to FIGS. 6 and 7, the systolic blood pressure and the diastolic blood pressure of the measurement subject are measured. Accordingly, in step S110, the process proceeds to step S120 on the condition that determination of both the systolic blood pressure and the diastolic blood pressure is completed. In addition, after the cuff pressure is set to the pressure PM, even when the cuff pressure is reduced to a specific pressure generally considered to be lower than the diastolic blood pressure, the diastolic blood pressure of the measurement subject cannot be determined. May forcibly end the blood pressure measurement process.

  In the blood pressure measurement process described with reference to FIG. 8, the piezoelectric element 200 is adjusted in a state in which the cuff pressure is adjusted to a pressure (for example, 30 mmHg) that is generally sufficiently lower than the pressure assumed as the diastolic blood pressure of the measurement subject. A reference of the amplitude of the surface potential was acquired (step S60). The reference may be acquired in the process in which the cuff pressure decreases from the pressure PM, that is, after the cuff pressure is reduced in step S90. However, in this case, the acquisition of the reference needs to be acquired until the cuff pressure is set to a pressure that is generally considered to be sufficiently larger than the pressure assumed as the systolic blood pressure.

[Second Embodiment]
In the sphygmomanometer 100 of the present embodiment, a thin plate that covers the piezoelectric element is further provided to the piezoelectric element 200 in order to avoid as much as possible transmission of vibration due to expansion / contraction of the air bladder 151 to the piezoelectric element 200. .

An example of a cuff cross section of the sphygmomanometer 100 of the present embodiment is shown in FIG.
Referring to FIG. 9, in cuff 150 of sphygmomanometer 100 according to the present embodiment, piezoelectric element 200 and cushion material 201 provided to avoid the vibration of air bladder 151 being transmitted to piezoelectric element 200. Further, a thin plate 202 is disposed between the two.

As the thin plate 202, for example, a material such as copper phosphate or SUS can be employed.
In the present embodiment, the thin plate 202 is further provided between the cushion material 201 and the piezoelectric element 200, so that vibration from the air bladder 151 can be reliably prevented from being transmitted to the piezoelectric element 200, and the cuff 150 can be When wound around the measurement site, the piezoelectric element 200 can be more reliably fitted to the measurement site.

[Third Embodiment]
In the sphygmomanometer 100 of the present embodiment, an air bag for fixing the piezoelectric element 200 is provided instead of the cushion material 201 of the second embodiment.

FIG. 10 is a diagram schematically showing a cross section of the cuff 150 of the sphygmomanometer 100 of the present embodiment.
Referring to FIG. 10, in cuff 150 of the present embodiment, air bag 203 is provided instead of cushion material 201 provided in the cuff of the second embodiment shown in FIG. 9. In the present embodiment, the air bag 203 constitutes a fixing fluid bag.

FIG. 11 is a diagram schematically showing a block configuration of the sphygmomanometer according to the present embodiment.
Further, referring to FIG. 11, sphygmomanometer 100 according to the present embodiment further includes an air bag 203 in order to securely fix piezoelectric element 200 to the measurement site. In addition, inside the apparatus main body 110 of the sphygmomanometer 100 of the present embodiment, a piezoelectric element fixing air system component 310 for supplying or discharging air to the air bag 203 is provided. The piezoelectric element fixing air system component 310 includes a pressure sensor 311 for detecting the pressure in the air bag 203, a pump 312 and a valve 313 for inflating / deflating the air bag 203. In addition, an amplifier 320, an A / D conversion circuit 321, a pump drive circuit 330, and a valve drive circuit 340 are provided in the apparatus main body 110 in association with the piezoelectric element fixing air system component 310.

  The amplifier 320 appropriately amplifies the output value of the pressure sensor 311 and outputs it to the A / D conversion circuit 321. The A / D conversion circuit 321 converts the analog signal output from the amplifier 320 into a digital signal and outputs it to the CPU 122. The CPU 122 detects the internal pressure of the air bag 203 by appropriately processing the output with the signal processing unit 122A.

  The pump drive circuit 330 controls the drive of the pump 312 based on a control signal given from the CPU 122. The valve drive circuit 340 controls opening and closing of the valve 313 based on a control signal given from the CPU 122.

  In the blood pressure measurement process of the present embodiment, the CPU 122 adjusts the internal pressure of the air bladder 151 and the air bladder 203 to a pressure (for example, 30 mmHg) that is sufficiently lower than the pressure generally assumed as the diastolic blood pressure of the measurement subject. In this state, the amplitude reference of the piezoelectric element 200 is acquired (step S60).

  In the blood pressure measurement process, the internal pressure of the air bag 203 is controlled so as to be the same pressure as the air bag 151.

  The reference may be acquired in the process in which the internal pressure of the air bag 203 decreases from the pressure PM together with the cuff pressure, that is, after the cuff pressure and the pressure reduction of the air bag 203 in step S90 are started. However, in this case, the acquisition of the reference needs to be acquired until the cuff pressure is set to a pressure that is generally considered to be sufficiently larger than the pressure assumed as the systolic blood pressure.

  Further, in the blood pressure measurement process, the internal pressure of the air bag 203 is not the same pressure as that of the air bag 151 at a time other than the acquisition of the reference described above, but a predetermined pressure for fixing the piezoelectric element 200 to the measurement site. It may be controlled.

  FIG. 12 is a diagram for explaining the effect of fixing the piezoelectric element 200 by the air bag 203 provided in the present embodiment.

  FIG. 12A shows the cuff pressure at the time of blood pressure measurement in the state where the air bag 203 is provided in the cuff 150 and the internal pressure of the air bag 203 is appropriately pressurized as described with reference to FIG. It is a figure which shows the change (data D11) and the change (data D11) of the surface potential of the piezoelectric element 200 accompanying the change of the said cuff pressure.

  On the other hand, FIG. 12B shows a piezoelectric element with respect to a change in cuff pressure during blood pressure measurement in a sphygmomanometer that does not include an air bag for fixing the piezoelectric element 200 in the cuff 150, as shown in FIG. It is a figure which shows the change (data D22) of surface potential.

  Compared with the data D22 in FIG. 12B, in the data D11 in FIG. 12A, the increase in the amplitude of the surface potential of the piezoelectric element 200 is started in the process of decreasing the cuff pressure (measurement time around 22 seconds). The start of, the maximum of the amplitude, and the timing immediately before the amplitude decreases and becomes equivalent to the reference (measurement time around 28.5 seconds) are visible.

  On the other hand, in the data D22 of FIG. 12B, although it is displayed enlarged in the vertical axis direction (the interval of the potential scale on the vertical axis is reduced) with respect to FIG. The change in the amplitude according to the change in the cuff pressure, which is seen in the data D11 in FIG.

  As shown in FIG. 13, since the air bag 203 for fixing the piezoelectric element 200 to the measurement site is not provided, the piezoelectric element 200 becomes in a relatively unstable state in blood pressure measurement, and the blood of the artery It is considered that the movement of the arm A (see FIG. 3) itself other than the vibration due to the flow is included as noise.

  As described above, in the present embodiment, the piezoelectric element 200 can be more stably brought into close contact with the measurement site in the cuff 150, whereby the blood flow of the artery in the measurement site can be more reliably ensured. This is reflected in the 200 detection outputs.

[Contrast with blood pressure measurement based on Korotkoff sound against external noise]
FIG. 14 is a diagram for explaining the blood pressure measurement based on the Korotkoff sound, which is generally performed, and the blood pressure measurement based on the detection output of the piezoelectric element 200 in each embodiment described in this specification. is there.

FIG. 14A shows a change in cuff pressure during blood pressure measurement.
14 (B) and 14 (C) show the volume of the K sound detected by the microphone 100Y according to the change in the cuff pressure in the sphygmomanometer 100X (see FIG. 16) which is a comparative example of the sphygmomanometer 100. Showing change. FIG. 14B shows the result when blood pressure is measured in a situation where there is no external noise, and FIG. 14C shows the result when blood pressure is measured in a situation where external noise is relatively large. is there.

  FIG. 14D shows an example of a change in surface potential of the piezoelectric element 200 in the sphygmomanometer 100 in accordance with the change in the cuff pressure in FIG.

  Referring to FIG. 14B, in the process in which the cuff pressure is adjusted to the pressure PM and then reduced, the volume of the Korotkoff sound (the amplitude in the vertical direction of the output in FIG. 14B) is the cuff pressure. Starts increasing when the pressure drops to a pressure corresponding to systolic blood pressure, then increases with a decrease in cuff pressure, then decreases, and when the cuff pressure is set to a pressure corresponding to the diastolic blood pressure of the subject. , Decrease rapidly.

  Similarly, regarding the amplitude of the surface potential of the piezoelectric element 200 shown in FIG. 14D, when the cuff pressure decreases to a pressure corresponding to the systolic blood pressure of the measurement subject, the amplitude of the surface potential starts to increase. As the cuff pressure decreases, the amplitude increases and then decreases, and then the amplitude decreases sharply when the cuff pressure becomes a pressure corresponding to the diastolic blood pressure of the measurement subject.

  On the other hand, the volume shown in FIG. 14C is accompanied by relatively large noise during almost the entire period during which the cuff pressure changes. This is because the microphone 100Y picks up noise generated outside. Then, due to such noise, recognizing a change in volume caused by the cuff pressure being a pressure corresponding to the systolic blood pressure or diastolic blood pressure of the measurement subject is shown in FIG. Compared to FIG. 14D, it is difficult.

  That is, in blood pressure measurement, in the case of blood pressure measurement based on the detection of Korotkoff sound using a microphone, when there is no noise or relatively small in the vicinity of the blood pressure monitor 100 (blood pressure monitor 100X), refer to FIG. As described above, it is considered that relatively accurate blood pressure measurement is possible, but when a relatively large noise is generated around the sphygmomanometer 100 (sphygmomanometer 100X), the Korotkoff sound is detected. Therefore, the microphone for picking up the external noise picks up the Korotkoff sound in the detection output of the microphone.

  On the other hand, if the blood pressure measurement is based on the detection output of the piezoelectric element 200 in the sphygmomanometer 100, the piezoelectric element 200 can detect the distortion of the living body caused by the blood flow in the artery without being affected by external noise.

  Thereby, according to the blood pressure measurement using the piezoelectric element 200 described in the present specification, a relatively accurate blood pressure measurement can be performed without being affected by external noise.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. The embodiments described above are intended to be implemented in combination as much as possible.

  100 sphygmomanometer, 150 cuff, 151,203 air bag, 161 bag-shaped cover body, 200 piezoelectric element, 201 cushion material, 202 thin plate, 203 air bag, 2001 piezo film, 2001A, 2001B terminal, 2002 silver paint, 2003 protection layer.

Claims (8)

A cuff that compresses the measurement site of the person being measured by being wound,
Control means for controlling the pressure in the cuff;
A piezoelectric element having a piezoelectric effect corresponding to the distortion of the surface of the measurement site;
A blood pressure measurement apparatus comprising: a determination unit that determines a blood pressure of the measurement subject based on a change in an output signal of the piezoelectric element due to a change in shape of the piezoelectric element.   The blood pressure measurement device according to claim 1, further comprising a fixing fluid bag that expands and contracts when fluid enters and exits in order to fix the piezoelectric element. In order to compress the measurement site, it is further equipped with a measurement fluid bag that expands and contracts when the fluid enters and exits,
3. The blood pressure measurement device according to claim 1, wherein the piezoelectric element is provided on one side of a direction intersecting a direction in which the cuff is wound around the measurement site with respect to the measurement fluid bag.   The blood pressure measurement device according to claim 3, further comprising a cushion material provided between the measurement fluid bag and the piezoelectric element.   5. The plate according to claim 3, further comprising a plate body provided between the measurement fluid bag and the piezoelectric element for preventing deformation of the piezoelectric element based on displacement of the measurement fluid bag. Blood pressure measuring device. The determining means includes
Obtaining the amplitude of the output signal of the piezoelectric element as a reference amplitude when the internal pressure of the fixing fluid bag is a specific pressure lower than a first pressure or a specific pressure higher than a second pressure;
When the internal pressure of the measurement fluid bag drops from a predetermined pressure higher than the second pressure, the internal pressure of the measurement fluid bag when the amplitude of the output signal of the piezoelectric element exceeds the reference amplitude is measured. The measurement person's systolic blood pressure is determined, and the internal pressure of the measurement fluid bag when the amplitude of the output signal of the piezoelectric element falls below the reference amplitude is determined as the measurement person's diastolic blood pressure. The blood pressure measurement device according to any one of claims 1 to 5.   The blood pressure measurement device according to claim 6, wherein the first pressure is a diastolic blood pressure, and the second pressure is a systolic blood pressure. A blood pressure measurement method using a blood pressure measurement device,
The blood pressure measurement device includes a piezoelectric element that exerts a piezoelectric effect corresponding to the distortion of the surface of the measurement site on a cuff that presses the measurement site of the measurement subject when wound.
A blood pressure measurement method for determining a blood pressure of a person to be measured based on a change in voltage of the piezoelectric element due to a change in shape of the piezoelectric element.