JP6136111B2 - Blood pressure measurement device - Google Patents

Description

  The present invention relates to a blood pressure measurement device, and more particularly to a blood pressure measurement device in which a measurement subject manually wraps a cuff around a measurement site.

  Blood pressure is one of the indices for analyzing cardiovascular diseases, and risk analysis based on blood pressure is effective in preventing cardiovascular diseases such as stroke, heart failure and myocardial infarction. Conventionally, diagnosis has been performed based on blood pressure (anytime blood pressure) measured at a medical institution such as when visiting a hospital or during a medical examination. However, recent studies have shown that blood pressure measured at home (home blood pressure) is more useful for diagnosis of cardiovascular diseases than blood pressure at any time. Accordingly, blood pressure monitors used at home have become widespread.

  Many home blood pressure monitors employ an oscillometric blood pressure measurement method. Blood pressure measurement by the oscillometric method is to wrap the cuff around a measurement site such as the upper arm, pressurize the cuff internal pressure (cuff pressure) by a predetermined pressure (for example, 30 mmHg) higher than the systolic blood pressure, and then gradually or stepwise. Reduce the cuff pressure. In this decompression process, the volume change of the artery is detected as a pressure change (pulse wave amplitude) superimposed on the cuff pressure, and the systolic blood pressure and the diastolic blood pressure are determined from the change in the pulse wave amplitude. In the oscillometric method, the blood pressure can be measured by detecting the amplitude of the pulse wave generated in the process of increasing the cuff pressure.

  In the case of a blood pressure measurement device in which a cuff is manually wrapped around a measurement site, it is necessary to appropriately wrap the cuff around the measurement site in order to accurately measure the blood pressure. Therefore, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2008-188197) and Patent Document 2 (WO 2010/089917) show methods for determining the winding strength of the cuff.

  In the method of Patent Document 1, the cuff is wound around the measurement site, the cuff wearing state is determined based on the amount of change in the cuff pressure after the blood pressure measurement is started, and a reference value for determining pass / fail of the cuff wearing state is set as the power supply voltage ( Battery voltage).

JP 2008-188197 A WO2010 / 089917

  However, in the method of Patent Document 1, the change in cuff pressure during blood pressure measurement is not only the cuff wearing state, but also the size (peripheral length) and quality (muscle quality, fat, etc.) of the measurement site, and the type of cuff (size, etc.) ), Which greatly changes depending on the surrounding environment (such as room temperature), it remains difficult to accurately detect the wearing state with reference values set without considering these factors.

  The method of Patent Document 2 calculates the pressure change in the cuff from the pressurization / depressurization time, and estimates the size of the measurement site from the time required for the pressure change in the constant cuff, thereby solving the above problem. It has been solved.

  Thus, although the method of patent document 2 estimates from the amount of cuff compliance, the difference in the amount of cuff compliance becomes smaller when the cuff pressure increases depending on the quality of the measurement site and the cuff attachment state. It is difficult to estimate the quality and quality, and it is difficult to correctly determine the degree of cuff winding. The amount of cuff compliance indicates the volume of air that is sent into the cuff necessary to pressurize per 1 mmHg.

  Therefore, an object of the present invention is to provide a blood pressure measurement device that determines a cuff winding state without depending on a change in the capacity in the cuff.

  A blood pressure measurement device according to an aspect of the present invention is a blood pressure measurement device that determines a blood pressure value from a cuff pressure of a cuff that is wound around a measurement site of a measurement subject. Adjustment means for variably adjusting the fluid amount, pressure detection means for detecting the cuff pressure, control means for variably controlling the voltage applied to the adjustment means, and voltage applied to the adjustment means In the adjustment process for variably adjusting the amount of fluid in the cuff and the voltage detection means for detecting the value, the change in the cuff pressure detected from the cuff wound around the measurement site, and the change in the cuff pressure Perimeter detection means for detecting the perimeter of the measurement site around which the cuff is wound from the pressure-voltage change relationship according to the change in the voltage value detected along with this.

  According to the present invention, the winding state of the cuff is determined without depending on the change in the capacity in the cuff.

1 is an external perspective view of a blood pressure measurement device according to the present embodiment. It is a block diagram showing the hardware constitutions of the blood pressure measurement apparatus 1 which concerns on this Embodiment. It is a functional block diagram which shows the function structure of the blood pressure measurement apparatus which concerns on this Embodiment. (A)-(C) are the block diagrams of the table which concerns on this Embodiment. It is a figure which shows typically the cuff pressure change at the time of the blood-pressure measurement which concerns on this Embodiment. It is a figure which shows typically the change of the pump voltage according to the change of the cuff pressure concerning this Embodiment. It is a figure which shows typically the change of the pump voltage according to the change of the cuff pressure concerning this Embodiment. It is a processing flowchart concerning this embodiment. It is a figure for demonstrating the modification of the process flowchart which concerns on this Embodiment. It is a figure for demonstrating the procedure which detects perimeter length in the pressure reduction process in this Embodiment. It is a figure which shows the example of a recording of the blood pressure measurement data which concerns on this Embodiment. It is a figure which shows the example of a display of the blood pressure measurement result which concerns on this Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 is an external perspective view of a blood pressure measurement device 1 according to the present embodiment. Referring to FIG. 1, blood pressure measurement device 1 includes a main body 100 and a cuff 40 that is manually wound around a measurement site (for example, a wrist) of a measurement subject. The main body 100 is attached to the cuff 40 integrally or detachably. On the surface of the main body 100, a display unit 12 made of, for example, liquid crystal and an operation unit 13 for receiving instructions from a user (a person to be measured) are arranged. The operation unit 13 includes a plurality of switches.

  As shown in FIG. 1, the blood pressure measurement device 1 according to the present embodiment will be described by taking an example in which the main body 100 is attached to the cuff 40, but is adopted in an upper arm type sphygmomanometer. The main body 100 and the cuff 40 may be connected by an air tube.

  FIG. 2 is a block diagram showing a hardware configuration of blood pressure measurement device 1 according to the present embodiment. Referring to FIG. 2, blood pressure measurement device 1 includes a cuff 40 and an air system that are attached to a blood pressure measurement site. The cuff 40 includes the air bag 20. The air bag 20 is connected to the air system via the tube 300.

  The blood pressure measurement device 1 further centrally controls the display unit 12, the operation unit 13, and each unit to perform various arithmetic processing, a CPU (Central Processing Unit) 10, a program for causing the CPU 10 to perform predetermined operations, and various types A memory 11 for storing data, a detachable battery 15 for supplying power to each unit, a timer 14 for performing a timekeeping operation, and a temperature sensor 17 for measuring an environmental temperature in which the blood pressure measuring device 1 is installed including. The memory 11 includes a non-volatile memory (for example, a flash memory) for storing the measured blood pressure. The non-volatile memory stores a table 433, a table 434, and a table 435 searched by the estimation unit 35 described later. These tables will be described later with reference to FIG.

  The operation unit 13 includes a power switch that accepts an operation for turning the power on or off, a measurement switch that accepts an operation for starting measurement, a stop switch for accepting an operation of an instruction to stop measurement, and a user (a person to be measured) A user selection switch for accepting an operation for selectively designating the user. The operation unit 13 also has a switch for receiving an operation for reading information such as measured blood pressure stored in the flash memory and displaying the information on the display unit.

  In the present embodiment, since blood pressure measurement device 1 is shared by a plurality of persons to be measured, the blood pressure measurement device 1 includes a user selection switch. However, if the blood pressure measurement device 1 is not shared, the user selection switch may be omitted. The measurement switch may also be used as a power switch. In that case, the measurement switch can be omitted.

  The air system includes a pressure sensor 21 for detecting pressure in the air bag 20 (hereinafter referred to as cuff pressure), a pump 26 for supplying air to the air bag 20 to pressurize the cuff pressure, and an air bag. It includes an exhaust valve 24 that is opened and closed to exhaust or enclose 20 air. The blood pressure measurement device 1 includes an amplifier 22 and an A / D (Analog / Digital) converter 23, a pump drive circuit 27, and an exhaust valve drive circuit 25 in relation to the air system. Here, the pump 26, the exhaust valve 24, the pump drive circuit 27, the exhaust valve drive circuit 25, and the like correspond to an adjusting unit for adjusting the cuff pressure. The pump 26 is assumed to be a rotary pump in the present embodiment, but the type of pump is not limited to the rotary pump.

  In order to accurately detect the pulse wave amplitude in blood pressure measurement, it is necessary to increase or decrease the cuff pressure at a constant speed by the pump 26 or the exhaust valve 24. Specifically, in the constant speed pressurization control or the constant speed pressure reduction control, the drive for driving the pump 26 or the exhaust valve 24 so that the average speed becomes the target speed based on the difference between the average speed and the target speed. Feedback control of voltage.

  The pump drive circuit 27 generates and outputs a drive voltage signal 273 based on a control signal from the CPU 10. The drive voltage signal 273 indicates a drive voltage applied to the pump 26 (hereinafter referred to as a pump voltage).

  The exhaust valve drive circuit 25 controls the exhaust valve 24 based on a control signal given from the CPU 10.

  An A / D (Analog / Digital) converter 16 is provided in association with the battery 15. The A / D converter 16 receives the battery voltage of the battery 15 (voltage between terminals of the battery 15), converts it into digital data, and outputs a voltage signal 513 indicating the battery voltage value to the CPU 10. As the battery 15, a non-chargeable primary battery such as a dry battery or a rechargeable secondary battery can be applied. Therefore, CPU10 can drive each part within the range of the battery voltage to detect.

The pressure sensor 21 is a capacitance-type pressure sensor, and the capacitance value changes depending on the cuff pressure.
The pressure sensor 21 outputs a signal corresponding to the cuff pressure to the amplifier 22. The amplifier 22 amplifies the signal input from the pressure sensor 21 and outputs the amplified signal to the A / D converter 23. The A / D converter 23 converts the amplified signal (analog signal) input from the amplifier 22 into a digital signal, and outputs the converted digital signal to the CPU 10. Thereby, CPU10 detects a cuff pressure. The CPU 10 detects the cuff pressure by converting the signal obtained from the A / D converter 23 into pressure.

  In addition, although the fluid supplied to the cuff 40 is air here, it is not limited to this, For example, a liquid and a gel may be sufficient. Or it is not limited to fluid, Uniform microparticles, such as a microbead, may be sufficient.

(Functional configuration)
FIG. 3 is a functional block diagram showing a functional configuration of the blood pressure measurement device 1 according to the present embodiment. The functional configuration of FIG. 3 is shown using the functions of the CPU 10 and its peripheral parts.

  Referring to FIG. 3, the CPU 10 includes an operation receiving unit 30 for receiving a user operation via the operation unit 13, a pulse wave detecting unit 31 for inputting a pressure signal from the A / D converter 23, and a pressure detecting unit. 32, a drive control unit 33 that outputs control signals to the pump drive circuit 27 and the exhaust valve drive circuit 25, a blood pressure determination unit 34 that determines a blood pressure value according to the oscillometric method, and for reading and writing (accessing) data in the memory 11 An access unit 36, an output unit 37 that controls display on the display unit 12, and an estimation unit 35 are provided.

  The estimation unit 35 detects (estimates) the circumference of the measurement site around which the cuff 40 is wound, and the winding strength detection unit 352 detects (estimates) the winding strength of the cuff 40 with respect to the measurement site. And a correction unit 353 that outputs the corrected voltage value after correcting the detected voltage value of the voltage applied to the adjustment unit. The correction by the voltage correction unit 353 indicates that the detected voltage value is variably changed according to a predetermined condition.

  The drive control unit 33 has a function of increasing / decreasing the cuff pressure according to the pressurization speed target by controlling the exhaust valve drive circuit 25 and the pump drive circuit 27 during blood pressure measurement. The drive control unit 33 transmits a control signal to the exhaust valve drive circuit 25 and the pump drive circuit 27 in order to adjust the cuff pressure. Specifically, a control signal for increasing or decreasing the cuff pressure is output. In particular, the control signal is output according to feedback control described later.

  The pulse wave detection unit 31 detects a pulse wave signal representing a change in the volume of the artery superimposed on the pressure signal from the A / D converter 23 using a filter circuit. The pressure detection unit 32 converts the pressure signal from the A / D converter 23 into a pressure value and outputs it in order to detect the cuff pressure.

  The blood pressure determination unit 34 determines the blood pressure according to the oscillometric equation. Specifically, the blood pressure is determined based on the transition of the pulse wave amplitude and the cuff pressure using the cuff pressure input from the pressure detection unit 32 during blood pressure measurement and the pulse wave detected by the pulse wave detection unit 31. . For example, the cuff pressure corresponding to the maximum value of the pulse wave amplitude is the average blood pressure, the cuff pressure corresponding to the pulse wave amplitude on the high cuff pressure side corresponding to 50% of the maximum value of the pulse wave amplitude is the systolic blood pressure, and the pulse wave. The cuff pressure corresponding to the pulse wave amplitude on the low cuff pressure side corresponding to 70% of the maximum value of the amplitude is determined as the diastolic blood pressure. The pulse rate is calculated according to a known procedure using the pulse wave signal. The acquired blood pressure value and pulse rate measurement data are displayed on the display unit 12 via the output unit 37 or stored in the memory 11 via the access unit 36. The measurement data to be displayed or stored may include the measurement time input from the timer 14, the detected winding strength or the surrounding length.

(Detection of winding strength)
The cuff 40 is a belt-like bag having a substantially rectangular shape as shown in FIG. 1, and the air bag 20 is built in the bag. In the case of winding around the measurement site, the cuff 40 is wound so that the side extending in the longitudinal direction extends along the circumference (arm circumference) of the measurement site. When the winding is completed, the cuff 40 takes a cylindrical shape along the circumference of the measurement site. In this state, when the cuff 40 is appropriately wound around the measurement site, the arm circumference and the circumference of the cylinder cross section are substantially equal, and the pressure applied to the measurement site is used for blood pressure measurement. It will be in a state of 'just' winding that is appropriate level. On the other hand, when the circumference is shorter than the arm circumference, the cuff 40 is tightly wound around the measurement site and the pressure applied to the measurement site is higher than the appropriate level. Become. On the other hand, if the length is long, the cuff 40 is loosely wound around the measurement site, and the pressure applied to the measurement site is in a 'loose' winding state lower than the appropriate level.

  When blood pressure measurement is started in such a “tight” or “loose” winding state, it is not possible to apply appropriate pressure to the artery at the measurement site, and blood pressure measurement accuracy cannot be obtained. . Therefore, in order to obtain the measurement accuracy, it is required to have a “smooth” winding that can appropriately pressurize the artery at the measurement site by the internal pressure of the cuff 40.

<Principle of detection of winding strength>
In the present embodiment, the winding strength is detected using the method described in Patent Document 2 by the applicant. That is, i) cuff pressure based on the cuff pressure of the cuff 40 manually wrapped around the measurement site and the volume change of the fluid (air in this embodiment) supplied into the air bag 20 of the cuff 40. Is detected from the atmospheric pressure P11 to the pressure P22, and ii) the fluid volume ΔV23 required until the cuff pressure changes from the pressure P22 to the pressure P33, and iii) the fluid volume ΔV12. By calculating the rate of change of ΔV23, the winding strength of the cuff 40 with respect to the measurement site is detected.

  Here, the cuff pressure-volume change relationship obtained in the process of increasing the cuff pressure is used, but the winding strength can also be detected using the cuff pressure-volume change relationship obtained in the process of reducing pressure.

  First, the detection of the cuff pressure-volume change relationship over time from the atmospheric pressure P11 to the pressure P22 and the detection of the cuff pressure-volume change relationship over time from the pressure P22 to the pressure P33 will be described.

  In a state where the cuff 40 is wound around the measurement site, the pump 26 is driven so as to have a constant discharge flow rate per unit time during a predetermined period from the start of pressurization (section (A) in FIG. 5). Pressurize. During the pressurization period, the fluid is confined in the cuff 40 by the exhaust valve 24. In this state, the volume detector detects the volume of the cuff 40 by measuring the elapsed time using the timer 14 required for the change of the cuff pressure (change from the pressure P11 to the pressure P22 or change from the pressure P22 to the pressure P33). It corresponds to.

  If it is 'just' winding, the cuff pressure increases with a certain slope from the start of pressurization. On the other hand, in the case of “tight” winding, the cuff pressure suddenly increases after the start of pressurization, and then rises with a certain inclination. In the case of 'loose' winding, the time from the start of pressurization until the cuff pressure begins to rise increases, and after the rise starts, the cuff pressure rises with a certain slope.

  That is, in the case of “just” winding, a constant pressure volume change ΔP / ΔV based only on the volume of the cuff 40 (air bag 20) is obtained regardless of the pressurization time. On the other hand, in the case of “skin” winding, it is constant immediately after the start of pressurization, but thereafter the value of the pressure volume change ΔP / ΔV decreases rapidly and then remains constant. On the other hand, in the case of 'loose' winding, the value of the pressure volume change ΔP / ΔV hardly changes for a certain period of time after the start of pressurization. Continue to take. Data indicating these characteristics is stored in the memory 11 in advance, and the winding strength detection unit 352 has the volume detection unit described above, and the volume detection is performed in the section (A) before blood pressure is measured by the pulse wave. The change in the pressure volume change ΔP / ΔV value detected using the unit is collated with the change characteristic data in the memory 11 and the winding strength is estimated (detected) based on the collation result.

  Note that the winding strength may be acquired by the measurement subject operating the operation unit 13 and inputting it. Alternatively, it may be acquired by reading the winding strength, which is the mode value, from the history of the winding strength of the measurement subject stored in the memory 11.

(Feedback control of pump 26)
When blood pressure is measured according to the oscillometric equation, the cuff pressure must be increased at a constant pressure target in order to obtain measurement accuracy. That is, at the start of blood pressure measurement, the drive control unit 33 generates a control signal indicating a voltage based on the pressurization target value and outputs the control signal to the pump drive circuit 27. Accordingly, the pump drive circuit 27 generates a drive voltage signal 273 for driving the pump 26 according to the pressurization target value, and outputs the drive voltage signal 273 to the pump 26.

  After starting pressurization according to the initial pressurization speed target, the drive control unit 33 calculates the pressurization speed of the cuff pressure based on the cuff pressure input from the pressure detection unit 32, the calculated pressurization speed, and the current pressurization The speed target is compared, a control signal indicating a voltage based on the difference between the two according to the comparison result is generated and output to the pump drive circuit 27. In this way, using the control signal, the pump 26 is feedback-controlled so that the pressurization speed becomes the pressurization speed target.

  The discharge flow rate of the pump 26 is proportional to the voltage indicated by the control signal supplied from the drive control unit 33. Therefore, the feedback control described above can be realized by changing the voltage indicated by the control signal output from the drive control unit 33.

(Changes in cuff pressure and pump voltage during pressurization)
FIG. 5 is a diagram schematically showing a change in cuff pressure during blood pressure measurement according to the embodiment of the present invention. FIG. 6 is a diagram schematically showing changes in pump voltage in accordance with changes in cuff pressure Pc in relation to FIG.

  A cuff pressure control method when blood pressure is measured in the pressurization process will be described. Referring to FIG. 5, the measurement period is divided into three sections: (A) rapid pressurization section, (B) constant speed pressurization section, and (C) rapid exhaust section.

  (A) The rapid pressurization section is from the measurement start (pressurization start) until the cuff pressure reaches the predetermined value P1.

(B) The constant velocity pressurization section is from the cuff pressure P1 to the end of blood pressure calculation.
(C) The rapid exhaust section is from the end of blood pressure calculation to the end of exhaust.

  The predetermined value P1 in FIG. 5 is a cuff pressure value for starting constant speed pressurization (pulse wave detection) by constant speed pressurization, which is lower than the lowest diastolic blood pressure (minimum blood pressure) assumed for the measurement subject. Set to a sufficiently low value. The section (B) is a section (1) from the start of constant velocity pressurization until the cuff pressure reaches a predetermined value P2, a section (2) immediately before and after the first pulse wave detection, and the subsequent cuff pressure. It includes a section (3) in which a pulse wave is detected until Pc becomes a pressurization target. Here, the predetermined value P2 is set from data such as experiments. The pressurization target is set to the systolic blood pressure (maximum blood pressure) + αmmHg (where α> 0) of the measurement subject.

  In FIG. 5, the measurement subject wraps the cuff 40 that has been sufficiently evacuated around the measurement site, and starts the pressurization operation. At the start of pressurization, the exhaust valve 24 is closed. In the section (A) after the start of pressurization, the drive voltage signal 273 indicating the constant voltage V1 is applied to the pump 26. As a result, the cuff pressure Pc rapidly rises to the predetermined value P1. In the subsequent section (B), the pump voltage is variably controlled so that constant pressure can be applied at the target pressurization speed (unit: mmHg / sec). The constant speed pressurization is continued until the cuff pressure Pc indicates a pressurization target by the feedback control described above. In the subsequent section (C), the pump 26 stops and is quickly exhausted (cuff pressure is rapidly reduced) from the air bag 20 through the tube 300 by the exhaust valve 24.

  First, in the section (A), the winding strength is detected by the winding strength detection unit 352. When the section (A) ends when the cuff pressure Pc indicates the pressure P1, the estimation unit 35 searches the table 433 in the memory 11 based on the required time of the section (A), so The voltage Vx (or Xy) is determined. Further, since the required time varies depending on the winding strength, the voltage Vx (or Xy) can be indirectly determined from the winding strength.

  Referring to FIG. 4 (A), table 433 is data acquired by experiment, and voltage 33B and winding strength 33C at the start of constant speed pressurization corresponding to each of required time 33A and required time 33A. Is stored. The estimation unit 35 reads the corresponding voltage 33B by searching the table 433 based on the required time or winding strength detected in the section (A). The drive control unit 33 of the CPU 10 generates a control signal indicating the voltage value of the voltage 33 </ b> B and outputs it to the pump drive circuit 27.

  As a result, a drive voltage signal 273 to be applied to the pump 26 at the start of constant velocity pressurization in the section (B) is generated, and the pump voltage is determined.

  The pump voltage Vx (Vy) indicated by the voltage 33B at the start of constant speed pressurization determined from the table 433 is the upper drive voltage (rated value) of the pump 26 and the time required for the section (B) (peripheral length is different) This is a value determined empirically on the basis of a predetermined constant speed pressurization rate (unit: mmHg / sec).

  The pump voltage at the start of constant speed pressurization is determined, and constant speed pressurization is started under the above feedback control.

(Ambient length detection)
In the present embodiment, attention is paid to the fact that the change in the pump voltage is more significant than the cuff capacity depending on the cuff pressure, and the pump voltage is referred to for detecting the perimeter.

  FIG. 6 schematically shows the pressure-voltage change relationship in the section (B) obtained by the inventors' experiment. The horizontal axis of the graph is the cuff pressure Pc, and the vertical axis is the pump voltage. FIG. 6 exemplifies a graph of the pressure-voltage change relationship for each peripheral length (thick and thin) when the winding strength is “perfect” winding.

  The perimeter detection unit 351 detects the perimeter in the constant speed pressurization process of the section (B). Here, even if the winding strength is the same, the air capacity in the air bag 20 differs depending on the circumferential length, so that the change in pump voltage according to the cuff pressure change in the section (B) also differs in the circumferential length. That is, as shown in FIG. 6, even if the winding strength is the same, the pump voltage when the cuff pressure Pc indicates the predetermined value P2 is different if the perimeter is different. Paying attention to this point, the perimeter is detected.

  Specifically, the perimeter detection unit 351 changes the pressure-voltage according to the change in the cuff pressure detected in the section (B) and the change in the pump voltage value detected in accordance with the change in the cuff pressure. From the relationship, the perimeter of the measurement site around which the cuff 40 is wound is detected.

  The memory 11 stores in advance a table 435 for each winding strength that is referred to in order to detect the perimeter. The data of each table 435 in the memory 11 is acquired in advance by experiments. The table 435 stores the pump voltage 35A data detected when the cuff pressure Pc indicates the predetermined value P2 and the peripheral length 35B data in association with each other.

  In operation, the perimeter detection unit 351 extracts the corresponding table 435 from the memory 11 based on the winding strength (tight winding, loose winding, tight winding) detected in the section (A). Then, by searching the extracted table 435 based on the pump voltage detected when the cuff pressure Pc indicates the predetermined value P2, the peripheral length 35B corresponding to the pump voltage 35A corresponding to the detected pump voltage is obtained from the table 435. Read from. Thereby, the perimeter is detected.

  As another detection method, the slope of the graph shown in FIG. 6, that is, the value of ((Vα−Vx) / (P2−P1)) and the value of ((Vβ−Vy) / (P2−P1)) are calculated. It may be detected from the calculated inclination. Specifically, a table in which the inclination for each winding strength is registered is stored in the memory 11. In each table, inclination values are registered in advance for each peripheral length in the case of the winding strength. By searching the table based on the detected inclination, the corresponding perimeter is read from the table. Note that the data in these tables is also acquired in advance by experiments.

(Adjustment of pump voltage by temperature)
The detected pump voltage may be corrected based on the temperature characteristics of the pump 26, more specifically, the components of the pump 26, that is, may be variably changed.

  Here, when the pump 26 is a rotary pump, the pump 26 includes, as components, an air chamber (chamber) in which an air discharge port communicating with the tube 300 and an air suction port from the outside are formed, and an air chamber And a rotor that is rotated by a drive voltage signal 273. As the rotor rotates in the air chamber, air is pushed out from the suction port to the discharge port, and is sent to the cuff 40 via the tube 300. As a result, the cuff pressure increases.

  However, since part materials such as air chambers and rotors expand depending on the ambient temperature, it is necessary to change the pump voltage according to the ambient temperature. That is, when these components are inflated, even if the pump voltage applied to the pump 26 is the same, the air volume delivered from the discharge port will be different. The volume of air that can be sent changes, and the cuff pressure also changes, which makes it difficult to accurately detect the perimeter and winding strength. In order to eliminate this, in the present embodiment, the detected pump voltage is corrected based on the temperature characteristics of the pump 26.

  To correct the pump voltage, the table 434 in FIG. 4B is referred to. Referring to FIG. 4B, table 434 stores different temperatures 34A and correction coefficients 34B corresponding to the respective temperatures 34A. The data in the table 434 is acquired in advance by experiments.

  The voltage correction unit 353 of the estimation unit 35 searches the table 434 based on the pump voltage value input from the A / D converter 28, and reads the corresponding coefficient 34B. The value of the detected pump voltage is corrected by a predetermined arithmetic expression using the read coefficient and the detected pump voltage value.

  The voltage correction unit 353 outputs the pump voltage value calculated by such correction to the surrounding length detection unit 351 and the winding strength detection unit 352. The perimeter detection unit 351 and the winding strength detection unit 352 detect the above-described perimeter length and winding strength using the pump voltage supplied from the voltage correction unit 353.

  Thereby, it becomes possible to use the pump voltage corrected according to the temperature characteristics of the pump 26, and it becomes possible to more accurately detect the peripheral length and the winding strength.

(Pump voltage adjustment based on individual pump differences)
Even in the case where the cuff pressure shows the same value, the pump voltage varies depending on the characteristics of the pump 26, more specifically, the characteristics of the components of the pump 26 depending on individual differences. The pump voltage is variably changed according to the individual difference.

  Here, attention is focused on the volume of the air chamber as one of the values indicating the characteristics due to individual differences. Even when the same pump voltage is applied, the air volume delivered to the cuff 40 is different if the volume of the air chamber is different. Therefore, in the constant speed pressurization, the pump voltage detected when the cuff pressure Pc indicates the predetermined value P2 is different due to the difference in the volume of the air chamber. Therefore, the voltage correction unit 353 variably changes the detected pump voltage based on the volume difference, and outputs the changed (corrected) pump voltage value to the surrounding length detection unit 351.

  In FIG. 7, graphs L <b> 1 and L <b> 2 according to the difference in air chamber volume are added to the graph of FIG. 6. In the constant speed pressurization process in the section (B), a one-dot chain line graph L1 (or L2) in FIG. 7 is detected based on the volume difference. The voltage correction unit 353 corrects the detected pump voltage so as to approximate the graph L1 (or L2) to a solid line graph. For this correction, the correction coefficient R is used.

  That is, the pump voltage (hereinafter referred to as the reference voltage) detected when the reference cuff pressure P3 is detected for the pump used to acquire the value of the table 435 in FIG. Stored in the memory 11. Here, the reference cuff pressure P3 is a value that satisfies the condition of (P1 <P3 <P2). Therefore, the correction coefficient R can be calculated by the equation (detected pump voltage / reference voltage at the reference cuff pressure P3) in the constant speed pressurization process.

  When the pump voltage V detected when the cuff pressure Pc indicates the predetermined value P2 in the constant speed pressurization process is input, the voltage correction unit 353 corrects the detected pump voltage by the formula of (pump voltage V × R), The corrected pump voltage value is output to the perimeter detection unit 351. Accordingly, since the perimeter detection unit 351 can search the table 435 based on the corrected pump voltage value, it can detect the perimeter independent of the characteristics of individual differences of the pump 26 (difference in the volume of the air chamber). Can do. Note that the characteristic value depending on the individual difference of the pumps 26 is not limited to the volume of the air chamber.

(flowchart)
FIG. 8 shows a process flowchart for blood pressure measurement according to the present embodiment. The process according to this flowchart is stored in advance in a predetermined storage area of the memory 11 as a program, and the blood pressure measurement process is realized by the CPU 10 reading the program from the memory 11 and executing it.

  In the measurement, it is assumed that the measurement subject has manually wrapped the cuff 40 around the measurement site in advance.

  When the measurement subject operates the switch to instruct the start of measurement, an initialization process is performed (step S202). Thereby, the air in the air bag 20 of the cuff 40 is exhausted, and the cuff pressure becomes substantially equal to the atmospheric pressure.

  Subsequently, the pump 26 is driven after the exhaust valve 24 is closed, whereby pressurization of the section (A) is started. In the section (A), the winding strength detection unit 352 detects the winding strength as described above (step S204).

  When the winding strength detection process ends, the winding strength detection result is temporarily stored in a predetermined storage area of the memory 11 via the memory access unit 150 (step S206). The temporarily stored winding strength detection result may be stored in the memory 11 in association with a blood pressure measurement result described later.

  In the constant pressure pressurization process of the section (B) after the section (A), the perimeter is detected by the perimeter detection unit 351 in the above-described procedure (step S212), and the detection result is displayed on the display unit 12 (step S213). ) And blood pressure is measured by the blood pressure determination unit 34 (step S214). Blood pressure measurement results (systolic blood pressure, diastolic blood pressure, pulse rate, etc.) are stored in the memory 11 in association with the measurement time data from the timer 14. When the blood pressure measurement is completed, a series of processing ends. Note that the measurement result may be displayed on the display unit 12, and the winding strength and circumference length detected at the time of blood pressure measurement may also be displayed to notify the measurement subject.

(Modification of flowchart)
The flowchart of FIG. 8 performs blood pressure measurement (step 214) regardless of the winding strength detected in step 204, but performs blood pressure measurement only when “tight winding” is detected. It may be changed. FIG. 9 shows a process to be added to the flowchart of FIG. 8 when making such a change.

  Referring to FIG. 9, when the blood pressure measurement is executed only when it is detected that “smooth winding” is detected, the detected winding strength is stored in memory 11 (step 206), and the winding strength is displayed. It is displayed on the part 12 (step 208). The person whose measurement is confirmed rewinds the cuff 40 around the measurement site, so that it is tight when it is confirmed as “loose” and loosely when it is confirmed as “tight”. By fixing it, you can make a perfect roll. Note that it is assumed that the person to be measured does not rewind when confirming that it is “perfect”.

  If the CPU 10 determines that “loose” or “tight” has been detected from the output of the winding strength detection unit 352 (NO in step S210), the CPU 10 stops the pump 26 and opens the exhaust valve 24, so that the inside of the cuff 40 All the air in the air bag 20 is exhausted (step S215). Thereby, the blood pressure measurement is stopped (forcedly ended). The user can smoothly rewind.

  When rewinding, the user operates the measurement start switch of the operation unit 13 again. The CPU 100 determines whether or not the measurement start switch is operated by the user from the output of the operation receiving unit 30 (step S216).

  If it is determined that the switch has been operated (YES in step S216), the process returns to step S204 to start blood pressure measurement, and the winding strength detection process (step S204) is similarly performed. If it is not determined that the switch has been operated (NO in step S216), the blood pressure measurement is not performed and the series of processes ends.

(Detection of perimeter during decompression process)
In the above description, the peripheral length is detected in the pressurizing process. However, the peripheral length may be detected in the process of reducing the cuff pressure. FIG. 10 is a diagram for explaining the procedure for detecting the perimeter in the decompression process in the present embodiment. First, a method for driving the exhaust valve 24 will be described.

Exhaust Valve Drive Method The exhaust valve drive circuit 25 controls the opening / closing operation of the exhaust valve 24 by electromagnetic induction based on a control signal from the drive control unit 33. The exhaust valve 24 has a valve body made of a resin material. The valve body is located at the opening on the exhaust valve 24 side communicating with the tube 300. The exhaust valve drive circuit 25 freely moves the exhaust valve 24 by electromagnetic force in accordance with a voltage (hereinafter referred to as a valve control voltage) indicated by a control signal from the drive control unit 33. By moving the valve body in conjunction with the movement of the exhaust valve 24, the amount of air exhausted from the opening is adjusted.

  Specifically, the drive control unit 33 determines a valve control voltage such that the pressure reduction speed becomes a predetermined target speed in the same manner as the feedback control of the pump 26 described above, and sends a control signal to the exhaust valve drive circuit 25. Is output. The exhaust valve drive circuit 25 generates an electromagnetic force according to the valve control voltage from the drive control unit 33. The exhaust valve 24 moves freely by electromagnetic force, and in conjunction with the movement of the exhaust valve 24, the valve body moves so as to approach / separate the opening side, and the movement causes the feed from the exhaust valve 24 side to the opening part. The amount of pressure is variably adjusted. Thereby, the amount of air exhausted from the air bag 20 through the opening is adjusted, and the decompression speed is changed variably.

  Here, the exhaust valve 24 moves so that the amount of pressure supplied to the opening increases as a higher valve control voltage is applied, and operates to reduce the amount of exhaust from the opening. That is, it operates so that the opening is closed.

  In this way, the decompression process is performed by controlling the movement of the valve body with respect to the opening. Further, in the depressurization process, the quick exhaust is performed by moving the valve body sufficiently away from the opening. In the pressurization process described above, the valve body is in a fully closed state in contact with the opening.

  FIG. 10 is a graph showing the relationship between the cuff pressure change and the valve control voltage change during the pressure reduction process in the case of tight winding. The vertical axis of the graph represents the valve control voltage, and the horizontal axis represents the cuff pressure Pc.

  Referring to FIG. 10, when it is determined that the cuff pressure Pc has reached the pressurization target, the drive control unit 33 stops the pump 26 and applies a predetermined valve control voltage to the exhaust valve drive circuit 25. Then start exhausting.

  In operation, the CPU 10 applies a predetermined valve control voltage to the exhaust valve 24 so that the cuff pressure Pc is increased from the pressurization target based on the output from the pressure detection unit 32, for example, κ1 (κ1> 0) mmHg. When it is determined that the pressure has been reduced, the valve control voltage Vp at the start of constant speed pressure reduction is determined based on the time required for the pressure reduction measured by the timer 14. The valve control voltage Vp can be determined by searching a table similar to the table 433 for the pressurization process.

  When the valve control voltage Vp at the start of constant speed decompression is determined, constant speed decompression is started. That is, the valve control voltage is variably changed by feedback control so that the cuff pressure Pc is reduced at a constant target speed. The valve control voltage applied to the exhaust valve drive circuit 25 when the cuff pressure Pc indicates a predetermined value P2a (for example, a value reduced by κ2 (κ> 0) mmHg from the pressurization target) in the constant speed depressurization process. Peripheral length is estimated from the relationship between Vq and a cuff pressure-voltage relationship between a predetermined cuff pressure change (κ1 (mmHg) to κ2 (mmHg)) and a change in valve control voltage according to the cuff pressure change (Vp−Vq). . Also in the estimation of the perimeter, a perimeter can be detected by storing a table according to the table 435 in the memory 11 and searching this table.

  In FIG. 10, the cuff pressure-voltage relationship is shown in each case where the perimeter is “thin” and “thick” under tight winding. When the perimeter is thick, the volume of the air bag 20 in the wound state becomes larger than that when it is thin. For this reason, if the pressure is reduced at the same speed as that of the thin case, the thicker one decreases the amount of pressure supplied to the opening and increases the exhaust amount. Therefore, the valve control voltage decreases more quickly when the perimeter is thin or thick (see FIG. 10). Therefore, the perimeter detection unit 351 acquires the data of the graph of FIG. 10 using the memory 11 from the cuff pressure detected by the pressure detection unit 32 and the valve control voltage determined by the drive control unit 33. The perimeter can be estimated from the slope of the graph.

  Further, since the valve body of the exhaust valve 24 is a resin material, the degree of expansion varies depending on the ambient temperature around the blood pressure measurement device 1. Therefore, the valve control voltage according to the temperature applied by the pump 26 is also corrected for the exhaust valve 24.

  In the above-described embodiment, the blood pressure measurement is performed in the constant speed pressurization process. However, the blood pressure measurement may be performed in the constant speed depressurization process instead of the constant speed pressurization process.

  In this embodiment, the pump voltage and the valve control voltage are acquired by searching a table, but may be calculated from a predetermined arithmetic expression.

(Measurement data storage example)
FIG. 11 is a diagram showing a table 394 of the memory 11 for recording data relating to blood pressure measurement according to the present embodiment. Referring to FIG. 11, the table 394 stores blood pressure measurement data in record units. To do. Each record includes ID (identification) data 39E for uniquely identifying the record, data 39F for identifying a person to be measured (user), measurement date / time data 39G, blood pressure values (systolic blood pressure data SBP and Data 39H including diastolic blood pressure data DBP) and pulse rate data PLS, wearing state of the cuff 40 at the measurement site, that is, data 39I indicating winding strength and data 39J of measurement conditions. The measurement condition indicated by the data 39J indicates the perimeter of the measurement site around which the cuff 40 is wound during the blood pressure measurement of the corresponding data 39H. The perimeter is indicated by either “L” or “M”. “L” indicates that the perimeter is relatively long. Here, there is a relationship of M <L.

  The manner of storing blood pressure measurement data in the table 394 is not limited to record units as shown in FIG. What is necessary is just the aspect by which the detected data 39E-39J are linked | related and recorded whenever a blood pressure is measured.

(Display example)
FIG. 12 is a diagram showing a display example of blood pressure measurement results according to the present embodiment. Referring to FIG. 12, output unit 37 causes display unit 12 to output, as a measurement result, winding strength data 40B, systolic blood pressure, diastolic blood pressure and pulse rate data 40C, and peripheral length data 40D. And the date and time of measurement are displayed on the same screen. In FIG. 12, the data 40 </ b> B indicates that the winding strength is appropriate (“perfect” winding) by characters “GOOD”. Also, the detected perimeter (size M, L) is displayed by the data 40D.

  As described above, in the present embodiment, the winding state (winding) of the cuff 40 using the control voltage for the pump 26 or the exhaust valve 24 which is the cuff pressure adjusting unit is not dependent on the change in the capacity in the cuff. Attached strength and perimeter).

  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.

  26 pump, 27 pump drive circuit, 31 pulse wave detection unit, 32 pressure detection unit, 33 drive control unit, 34 blood pressure determination unit, 35 estimation unit, 100 electronic sphygmomanometer, 273 drive voltage signal, 351 circumference length detection unit, 352 Winding strength detection unit, 433, 434, 435 table.

Claims (9)

A blood pressure measurement device that determines a blood pressure value from a cuff pressure of a cuff wound around a measurement site of a measurement subject,
Adjusting means for variably adjusting the amount of fluid in the cuff by applying a voltage;
Pressure detecting means for detecting the cuff pressure;
Control means for variably controlling the voltage applied to the adjusting means;
Voltage detection means for detecting a voltage value applied to the adjustment means;
In the adjustment process for variably adjusting the amount of fluid in the cuff at a predetermined constant constant velocity, a change in the cuff pressure detected from the cuff wound around the measurement site and a change in the cuff pressure A blood pressure measuring device comprising: a perimeter detecting means for detecting a perimeter of a measurement site around which the cuff is wound based on a pressure-voltage change relationship according to a voltage value change detected along with the perimeter. A winding strength acquisition means for acquiring the winding strength of the cuff with respect to the measurement site;
The perimeter detection means is
The blood pressure measurement device according to claim 1, wherein a perimeter of a measurement site around which the cuff is wound is detected from the obtained winding strength and the pressure-voltage change. The winding strength acquisition means is
Means for detecting the volume of the cuff;
In the adjustment process, prior to the detection of the perimeter, a change in the cuff pressure detected from a cuff wound around the measurement site, and a change in the cuff volume detected in accordance with the change in the cuff pressure, The blood pressure measurement device according to claim 2, further comprising: a winding strength detecting unit that detects a winding strength of the cuff.   The perimeter detection means is detected when the cuff pressure detected from the cuff wound around the measurement site shows a predetermined pressure in the adjustment process of variably adjusting the amount of fluid in the cuff. The blood pressure measurement device according to claim 1 or 2, wherein a peripheral length of a measurement site around which the cuff is wound is detected from a voltage value. Means for changing the voltage value detected by the voltage detection means variably using a predetermined condition;
The blood pressure measurement device according to claim 1 or 2, wherein the pressure-voltage change relationship is indicated by the voltage value after the change.   The blood pressure measurement device according to claim 5, wherein the predetermined condition indicates an ambient temperature around the blood pressure measurement device.   The blood pressure measurement device according to claim 5, wherein the predetermined condition indicates a characteristic value due to an individual difference of the adjusting means. A blood pressure measurement device that determines a blood pressure value from a cuff pressure of a cuff wound around a measurement site of a measurement subject,
Adjusting means for variably adjusting the amount of fluid in the cuff by applying a voltage;
Pressure detecting means for detecting the cuff pressure;
Control means for variably controlling the voltage applied to the adjusting means;
Voltage detection means for detecting a voltage value applied to the adjustment means;
In the adjustment process of variably adjusting the amount of fluid in the cuff at a predetermined constant target speed by the adjustment means, the cuff pressure detected from the cuff wound around the measurement site is a predetermined pressure. A blood pressure measuring device , comprising: a perimeter detecting means for detecting a perimeter of a measurement site around which the cuff is wound from a voltage value detected when indicating cuff. The adjusting means includes means for supplying fluid into the cuff to pressurize the cuff pressure;
The blood pressure measurement device according to claim 8, wherein the adjusting step includes a step of supplying fluid into the cuff at the predetermined constant target speed by means of supplying the fluid.

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