US20110257540A1

US20110257540A1 - Electronic sphygmomanometer and blood pressure measuring method

Info

Publication number: US20110257540A1
Application number: US13/167,536
Authority: US
Inventors: Yukiya Sawanoi; Chisato Uesaka
Original assignee: Omron Healthcare Co Ltd
Current assignee: Omron Healthcare Co Ltd
Priority date: 2008-12-26
Filing date: 2011-06-23
Publication date: 2011-10-20
Also published as: JP5187402B2; DE112009003806B4; DE112009003803T5; RU2011131065A; JPWO2010073692A1; US20110251501A1; RU2011131072A; JPWO2010073684A1; CN102265295A; RU2517797C2; WO2010073690A1; CN102264287A; JPWO2010073685A1; JPWO2010073690A1; CN102264288B; JPWO2010073691A1; RU2516870C2; RU2522969C2; DE112009003801T5; US20110238326A1

Abstract

An electronic sphygmomanometer includes a central processing unit (CPU) that calculates a blood pressure calculation parameter by executing a predetermined calculation using a constant set in advance with respect to a change in a pressure pulse wave amplitude indicating a volume change of an artery at the time of blood pressure measurement. The CPU separately acquires measurement state related information related to a state of a user and/or a state of the cuff at the time of blood pressure measurement. When the measurement state related information is acquired, the CPU corrects the blood pressure calculation parameter by correcting the constant based on the measurement state related information.

Description

TECHNICAL FIELD

The present invention relates to an electronic sphygmomanometer including a cuff to be attached to a blood pressure measurement site and a blood pressure calculation unit for calculating a blood pressure value from a cuff pressure, and a blood pressure measuring method using the same.

BACKGROUND ART

A blood pressure is one type of index for analyzing a circulatory disease. Performing risk analysis based on the blood pressure is effective in preventing cardiovascular related disease such as apoplexy, cardiac arrest, and cardiac infarction. Conventionally, a diagnosis for performing the risk analysis is made from the blood pressure (occasional blood pressure) measured in medical institutions at the time of hospital visits and checkups. However, it is recognized from recent research that the blood pressure (home blood pressure) measured at home is more useful in diagnosing the circulatory disease than the occasional blood pressure. Accompanied therewith, the sphygmomanometer used at home is being widely used.
Most of the electronic sphygmomanometers currently being widely used use a blood pressure calculation algorithm of an oscillometric method. In the oscillometric method, a cuff is wrapped around a measurement site such as an upper arm and pressurized up to a predetermined pressure, and then depressurized gradually or in a step-wise manner. The oscillometric method is a method of detecting a change in arterial volume that occurs in the middle of depressurization as a pressure change (pressure pulse wave amplitude) superimposed on the cuff pressure, and applying a predetermined algorithm on the change in pressure pulse wave amplitude to determine the systolic blood pressure and the diastolic blood pressure. Generally, a point where the pressure pulse wave amplitude suddenly becomes large obtained during the depressurization is approximated as the systolic blood pressure, and a point where the pressure pulse wave amplitude suddenly becomes small is approximated as the diastolic blood pressure. Various algorithms have been reviewed to detect such points.
For example, as shown in FIG. 9 and the following [Equation 1], a value obtained by multiplying a predetermined ratio (first constant α, second constant β) set in advance to a maximum value of the pressure pulse wave amplitude is set as a blood pressure calculation parameter, and a cuff pressure at which the pressure pulse wave amplitude that matches (or is closest to) the relevant parameter is obtained and is calculated as the blood pressure value (see Patent Document 1).
Systolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×α
Diastolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×β [Equation 1]
Patent Document 1: Japanese Unexamined Patent Publication No. 3-81375

SUMMARY OF INVENTION

However, there is no theoretical evidence that the point where the pressure pulse wave amplitude suddenly changes matches the systolic blood pressure and the diastolic blood pressure. Thus, the first and second constants (α, β) for determining the blood pressure calculation parameter had to be experimentally or statistically determined based on a change pattern (hereinafter referred to as “envelope curve”) of a great number of blood pressure values and pressure pulse wave amplitudes. Conventionally, the first constant α is a fixed value of about 0.5, and the second constant β is a fixed value of about 0.7, regardless of a state of a user and/or a state of a cuff at the time of the blood pressure measurement.
With respect to a pressure pulse wave that forms the envelope curve, the pressure pulse wave amplitude is obtained by detecting a volume change of an artery transmitted to the cuff attached to the measurement site as a pressure change. The pressure pulse wave amplitude is thus subjected to the influence of the properties of the cuff. One of the properties of the cuff is an air flow rate (hereinafter referred to as cuff compliance) necessary for changing the pressure in the cuff (hereinafter referred to as cuff pressure) by 1 mmHg as shown in the graph of FIG. 10. As shown in FIG. 10, the cuff compliance becomes smaller as the cuff pressure becomes higher. Therefore, if a constant pulse wave amplitude is provided to the cuff without depending on the cuff pressure, the amplitude is detected large as the cuff pressure becomes higher, as shown in FIG. 11.
For example, when measuring two users having different blood pressures with a change in pressure pulse wave amplitude of the same envelope curve shape, the pressure pulse wave amplitude, that is, the shape of the envelope curve detected by the sphygmomanometer, differs depending on the blood pressure. Thus, there is difference in measurement accuracy depending on the blood pressure.
A state in which an artery B of an arm A of a user is compressed with a cuff 2101 will be described with reference to FIG. 12. As shown in FIG. 12, when the cuff pressure is pressurized to greater than or equal to a predetermined pressure of a blood pressure measurement range, the pressure of the central part of the cuff 2101 is sufficiently transmitted to the artery B, so that the artery B is completely pressure closed.
However, the artery B is not completely pressure closed because the pressure of the end of the cuff 2101 is not sufficiently transmitted to the artery B. This depends on the structure of the cuff 2101, where the portion where the artery B is not pressure closed always forms in the generally used cuff structure. A blood flow exists at a portion where the artery is not pressure closed corresponding to the heart side of the cuff 2101, and hence, the volume change of the artery B occurs and the pressure pulse wave caused thereby is detected. In Patent Document 1, such a pressure pulse wave is referred to as the background pulse wave. Due to the existence of the background pulse wave, the systolic blood pressure is detected in excess, and the diastolic blood pressure is detected in underestimation in [Equation 1].
In a conventional art disclosed in Patent Document 1, [Equation 1] is changed to the following [Equation 2]. An offset correction value (third constant ζ) indicating the component of the background pulse wave is added to the value obtained by multiplying a predetermined ratio (first constant α) set in advance to the maximum value of the pressure pulse wave amplitude to calculate the systolic blood pressure calculation parameter, and an offset correction value (fourth constant η) indicating the component of the background pulse wave is added to the value obtained by multiplying a predetermined ratio (second constant β) set in advance to the maximum value of the pressure pulse wave amplitude to calculate the diastolic blood pressure calculation parameter.
Systolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×α+ζ
Diastolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×β+η [Equation 2]
[Equation 2] is based on the presumption that the background pulse wave is constant without depending on the state of the user and/or the state of the cuff 2101 at the time of the blood pressure measurement such as the attribute of the user (peripheral length, blood pressure of the arm A), the size or the cuff pressure of the cuff 2101, and the like.
However, it is recognized that the background pulse wave changes by various states at the time of the blood pressure measurement. For example, if the cuff pressure is raised, a width in which the artery B is pressure closed becomes wider as shown in FIG. 12. Accompanied therewith, a width in which the background pulse wave generates becomes narrow if the artery B is not pressure closed, whereby the level of the background pulse wave detected as a result becomes small, as shown in the graph of FIG. 13.
The pressure pulse wave amplitude changes depending on the dynamical properties (arterial volume change involved in the arterial inner-outer pressure difference) of the artery B of the user. For example, a person with soft artery B has a large amplitude thereof, whereas a person with advanced arterial sclerosis has a small amplitude thereof (see FIG. 14). Therefore, the background pulse wave also changes depending on the dynamical properties.
If the systolic blood pressure and the diastolic blood pressure are determined by [Equation 2] in which the component of the background pulse wave is defined as constant, the blood pressure is determined in underestimation or in excess depending on the user.
Therefore, one or more embodiments of the present invention provides an electronic sphygmomanometer and a blood pressure measuring method for correcting a constant based on measurement state related information when executing a predetermined operation using the constant set in advance with respect to change in a pressure pulse wave amplitude indicating the volume change of the artery at the time of the blood pressure measurement to accurately acquire the blood pressure value using the acquired data, thereby enhancing the satisfaction level of the user.
According to one or more embodiments of the present invention, an electronic sphygmomanometer includes a cuff to be attached to a blood pressure measurement site, pressurization and depressurization means for adjusting a pressure to apply on the cuff, pressure detection means for detecting a pressure in the cuff, blood pressure calculation means for calculating a blood pressure value from a cuff pressure, recording means for recording the blood pressure value, and operation means for performing an operation such as blood pressure measurement; wherein the blood pressure calculation means has a configuration adapted to calculate a blood pressure calculation parameter based on a predetermined calculation of multiplying a constant with respect to a maximum value of a pressure pulse wave amplitude indicating volume change of an artery at the time of blood pressure measurement; the electronic sphygmomanometer further includes information acquiring means for separately acquiring measurement state related information related to a state of a user and/or a state of the cuff at the time of blood pressure measurement, and correction means for correcting the blood pressure calculation parameter by correcting the constant based on the measurement state related information when the measurement state related information is acquired by the information acquiring means; the information acquiring means has a configuration adapted to acquire information of temporarily determined blood pressure value as the measurement state related information related to the state of the user; and the correction means has a configuration adapted to correct the first and second constants based on the temporarily determined blood pressure value.
According to one or more embodiments of the present invention, the measurement state related information related to the state of the user may include information related to the blood pressure value of the user at the time of the measurement, maximum value of the pressure pulse wave amplitude, information related to the measurement site, disease information of the user, and age information of the user.
According to one or more embodiments of the present invention, the measurement state related information related to the state of the cuff may include in addition to the information of the maximum value of the cuff pressure at the time of the blood pressure measurement and the wrapping strength of the cuff, cuff specification information such as a size and a type of the cuff.
According to one or more embodiments of the present invention, an optimum blood pressure calculation parameter can be set for every state of the user and/or the state of the cuff at the time of the blood pressure measurement, and the measurement error can be reduced.
The temporarily determined blood pressure value can be temporarily determined during depressurization by a standard blood pressure calculation parameter.
The temporarily determined blood pressure value can be temporarily determined during pressurization by a standard blood pressure calculation parameter.
The temporarily determined blood pressure value can be the blood pressure value recorded in the recording means.
According to one or more embodiments of the present invention, the optimum blood pressure calculation parameter can be set for every blood pressure value of the user, and the measurement error can be reduced.
According to one or more embodiments of the present invention, the blood pressure calculation means has a configuration adapted to calculate a systolic blood pressure calculation parameter based on a predetermined calculation of multiplying a first constant to a maximum value of the pressure pulse wave amplitude, and adding a third constant related to a component of a background pulse wave generated when the pressure of the cuff is pressurized to a predetermined pressure outside a blood pressure value measurement range, and calculate a diastolic blood pressure calculation parameter based on a predetermined calculation of multiplying a second constant to the maximum value of the pressure pulse wave amplitude and adding a fourth constant related to a component of the background pulse wave; and the correction means corrects the third and fourth constants based on the measurement state related information.
According to one or more embodiments of the present invention, the third and fourth constants related to the component of the background pulse wave can be corrected for every state of the user and/or the state of the cuff at the time of the blood pressure measurement, so that an accurate blood pressure value can be calculated while suppressing the influence of error caused by the component of the background pulse wave.
According to one or more embodiments of the present invention, the information acquiring means may have a configuration adapted to acquire information of a temporarily determined blood pressure value as the measurement state related information related to the state of the user; and the correction means may have a configuration adapted to correct the first and second constants or the third and fourth constants based on the temporarily determined blood pressure value.
According to one or more embodiments of the present invention, the information acquiring means may have a configuration adapted to acquire information of a maximum value of the cuff pressure as the measurement state related information; and the correction means may have a configuration adapted to correct the first and second constants or the third and fourth constants based on the maximum value of the cuff pressure.
According to one or more embodiments of the present invention, the information acquiring means may have a configuration adapted to acquire information of a maximum value of the pressure pulse wave amplitude as the measurement state related information related to the state of the user; and the correction means may have a configuration adapted to correct the third and fourth constants based on the maximum value of the pressure pulse wave amplitude.
According to one or more embodiments of the present invention, the information acquiring means may have a configuration adapted to acquire information of a wrapping strength of the cuff as the measurement state related information; and the correction means may have a configuration adapted to correct the third and fourth constants based on the information of the wrapping strength of the cuff.
According to one or more embodiments of the present invention, the information acquiring means may have a configuration adapted to acquire cuff specification information related to a size and/or a type of the cuff as the measurement state related information; and the correction means may have a configuration adapted to correct the third and fourth constants based on the cuff specification information.
According to one or more embodiments of the present invention, the information acquiring means may have a configuration adapted to acquire information related to a measurement site of the user as the measurement state related information; and the correction means may have a configuration adapted to correct the third and fourth constants based on the information related to the measurement site of the user.
The information related to the measurement site of the user may include information such as peripheral length and quality of the measurement site.
The quality of the measurement site may include body fat percentage, subcutaneous fat percentage, or BMI.
According to one or more embodiments of the present invention, the information acquiring means may have a configuration adapted to acquire disease information of the user as the measurement state related information; and the correction means may have a configuration adapted to correct the third and fourth constants based on the disease information of the user.
According to one or more embodiments of the present invention, the information acquiring means may have a configuration adapted to acquire age information of the user as the measurement state related information; and the correction means may have a configuration adapted to correct the third and fourth constants based on the age information of the user.
According to one or more embodiments of the present invention, the information acquiring means may have a configuration adapted to acquire the measurement state related information based on detection of change in an inner pressure of the cuff.
According to one or more embodiments of the present invention, input means for permitting input of the measurement state related information by the user may be further arranged; wherein the information acquiring means may have a configuration adapted to acquire the measurement state related information inputted before the start of the blood pressure measurement.
One or more embodiments of the present invention relates to a blood pressure measurement method for adjusting a pressure to apply on a cuff when the cuff is attached to a blood pressure measurement site with pressurization and depressurization means, and calculating a blood pressure value with blood pressure calculation means based on the cuff pressure detected by pressure detection means; the method may include the steps of calculating a blood pressure calculation parameter by executing a predetermined calculation using a constant set in advance with respect to a maximum value of a pressure pulse wave amplitude indicating volume change of an artery at the time of blood pressure measurement in the blood pressure calculation means; separately acquiring measurement state related information related to a state of a user and/or a state of the cuff at the time of blood pressure measurement with information acquiring means; and correcting the blood pressure calculation parameter by correcting the constant with correction means based on the measurement state related information when the measurement state related information is acquired by the information acquiring means, wherein the step of calculating the blood pressure calculation parameter by the blood pressure calculation means includes calculating the blood pressure calculation parameter based on a predetermined calculation of multiplying the constant to the maximum value of the pressure pulse wave amplitude, and the step of correcting by the correction means includes acquiring information of temporarily determined blood pressure value as the measurement state related information related to the state of the user by the information acquiring means, and correcting the constant based on the temporarily determined blood pressure value.
According to one or more embodiments of the present invention, the optimum blood pressure calculation parameter can be set for every state of the user and/or the state of the cuff at the time of the blood pressure measurement, and the measurement error can be reduced.
Moreover, according to one or more embodiments of the present invention, the optimum blood pressure calculation parameter can be set for every blood pressure value of the user, and the process of reducing the measurement error can be executed.
According to one or more embodiments of the present invention, the step of calculating the blood pressure calculation parameter by the blood pressure calculation means may include calculating a systolic blood pressure calculation parameter based on a predetermined calculation of multiplying a first constant to a maximum value of the pressure pulse wave amplitude and adding a third constant related to a component of a background pulse wave, and calculating a diastolic blood pressure calculation parameter based on a predetermined calculation of multiplying a second constant to the maximum value of the pressure pulse wave amplitude and adding a fourth constant related to a component of the background pulse wave; and the step of correcting by the correction means may include correcting the third and fourth constants based on the measurement state related information.
According to one or more embodiments of the present invention, the third and fourth constants related to the component of the background pulse wave can be corrected for every state of the user and/or the state of the cuff at the time of the blood pressure measurement, so that a process of calculating an accurate blood pressure value can be executed while suppressing the influence of error caused by the component of the background pulse wave.
According to one or more embodiments of the present invention, the electronic sphygmomanometer and the blood pressure measuring method for accurately acquiring the blood pressure value using the acquired data are provided, so that the satisfaction level of the user can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of an electronic sphygmomanometer of a first embodiment.

FIG. 2 is a flowchart showing a blood pressure measurement operation according to the first embodiment.

FIG. 3 is a table showing a ratio for determining blood pressure calculation parameters for standard and for every temporary average blood pressure value.

FIG. 4 is a flowchart showing another example of the blood pressure measurement operation according to the first embodiment.

FIG. 5 is a flowchart showing another example of the blood pressure measurement operation according to the first embodiment.

FIG. 6 is a flowchart showing a blood pressure measurement operation according to a second embodiment.

FIG. 7 is a view showing a state when an artery of an arm of a user is compressed with a cuff, and is a view describing a relationship between a background pulse wave and a peripheral length of a measurement site of the user.

FIG. 8 is a view showing a state when an artery of an arm of the user is compressed with the cuff, and is a view describing the relationship between the background pulse wave and the size of the cuff.

FIG. 9 is a graph describing a blood pressure calculation algorithm example of an oscillometric type sphygmomanometer.

FIG. 10 is a graph showing an example of a property (cuff compliance) of the cuff.

FIG. 11 is a graph showing an example of a pressure pulse wave amplitude detected by the sphygmomanometer when a constant pulse wave amplitude is inputted.

FIG. 12 is a view showing a state when the artery of the arm of the user is compressed with the cuff, and is a view describing the relationship between the background pulse wave and the blood pressure value.

FIG. 13 is a graph showing properties of the background pulse wave amplitude.

FIG. 14 is a graph showing an example of dynamic properties of the artery.

DETAILED DESCRIPTION OF INVENTION

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment

First, a first embodiment in which a blood pressure calculation parameter is optimized for every blood pressure value of a user will be described.
As shown in FIG. 1, an electronic sphygmomanometer 2100 of a first embodiment includes a cuff 2101, an air tube 2102, a pressure sensor 2103, a pump 2104, a valve 2105, an oscillation circuit 2111, a pump drive circuit 2112, a valve drive circuit 2113, a timing unit 2115, a power supply 2116, a CPU 2120, a display unit 2121, a memory (for processing) 2122, a memory (for recording) 2123, an operation unit 2130, an interface 2171, and an external memory 2172.
FIG. 1 is a block diagram showing a configuration of the electronic sphygmomanometer 2100 of the first embodiment.
The cuff 2101 is a band shaped member that is connected to the air tube 2102 and that is attached to a blood pressure measurement site of the user to pressurize by air pressure.
The pressure sensor 2103 is an electrostatic capacitance type pressure sensor, in which a capacitance value changes according to the pressure in the cuff (cuff pressure).
The pump 2104 and the valve 2105 apply pressure to the cuff and adjust (control) the pressure in the cuff.
The oscillation circuit 2111 outputs a signal of the frequency corresponding to the capacitance value of the pressure sensor 2103.
The pump drive circuit 2112 and the valve drive circuit 2113 drive the pump 2104 and the valve 2105, respectively.
The timing unit 2115 is a device for timing the current date and time, and transmitting the timed date and time to the CPU 2120 as necessary.
The power supply 2116 supplies power to each configuring unit.
The CPU 2120 executes the control of the pump 2104, the valve 2105, the display unit 2121, the memories 2122, 2123, the operation unit 2130, and the interface 2171, the blood pressure determination process and the management of the recording values.
The display unit 2121 is configured by a display device such as a liquid crystal screen, and displays the blood pressure value according to a signal transmitted from the CPU 2120.
The memory (for processing) 2122 stores a ratio (to be described later) for determining blood pressure calculation parameter and a control program of the sphygmomanometer.
The memory (for recording) 2123 stores the blood pressure value, and stores the date and time, the user, and the measurement values in association to each other as necessary.
The operation unit 2130 is configured by a power supply switch 2131, a measurement switch 2132, a stop switch 2133, a record call out switch 2141, and a user selection switch 2142, and permits the operation input such as power ON/OFF of the sphygmomanometer and start of the measurement, and transmits the inputted input signal to the CPU 2120.
The interface 2171 records/reads out the blood pressure to and from the external memory 2171 according to the control of the CPU 2120.
The blood pressure measurement operation using the electronic sphygmomanometer 2100 configured as above will be described according to the flowchart of FIG. 2.
FIG. 2 is a flowchart showing the blood pressure measurement operation in the first embodiment.
First, when the power supply is turned ON by the operation of the power supply switch 2131 (power supply SW) (step S2101), the CPU 2120 executes the initialization process of the operation memory of the sphygmomanometer and performs the 0 mmHg adjustment of the pressure sensor 2103 (step S2102).
After the initialization process is finished, the cuff 2101 is wrapped around the measurement site of the user, the user is selected (step S2103) and the measurement switch 2132 (measurement SW) is pushed (step S2104), so that the CPU 2120 pressurizes the cuff pressure up to a predetermined pressure by the pump 2104 (step S2105 to step S2106), and gradually depressurizes the cuff pressure by the valve 2105 (step S2107).
The CPU 2120 extracts the pressure change component involved in the volume change of the artery superimposed on the cuff pressure obtained during the depressurization, and calculates a temporary blood pressure value by a predetermined calculation (step S2108). After the temporary blood pressure value is calculated (step S2109), the CPU 2120 opens the valve 2105 and exhausts the air of the cuff. The CPU 2120 optimizes the blood pressure calculation parameter by the calculated temporary blood pressure value (step S2110), and calculates the blood pressure value using the optimized blood pressure calculation parameter (step S2111). The CPU 2120 displays the calculated blood pressure value on the display unit 2121 (step S2112), and records the same in the memory (for recording) 2123 in association with the measurement date and time, and the user (step S2113).
The process from step S2105 to step S2111 will be specifically described centering on the optimization process (step S2110) of the blood pressure calculation parameter.
As shown in the table of FIG. 3, the memory (for processing) 2122 records ratios α, β for determining blood pressure calculation parameter (systolic blood pressure calculation parameter, and diastolic blood pressure calculation parameter) for standard and for every temporary blood pressure value.
FIG. 3 is a table showing the ratios (α, β) for determining blood pressure calculation parameters classified according to the standard and temporary average blood pressure values.
The CPU 2120 for executing step S2108 in FIG. 2 calculates the temporary systolic blood pressure calculation parameter and the temporary diastolic blood pressure calculation parameter by multiplying the ratios α, β (first and second constants) for determining standard blood pressure calculation parameter to the maximum value of the pressure pulse wave amplitude, thereby calculating the temporary blood pressure value (temporary diastolic blood pressure, temporary systolic blood pressure). The ratio α (first constant) for determining temporary systolic blood pressure calculation parameter is set to 0.5 (50%), and the ratio β (second constant) for determining temporary diastolic blood pressure calculation parameter is set to 0.7 (70%). After the temporary systolic blood pressure calculation parameter and the temporary diastolic blood pressure calculation parameter are calculated, the CPU 2120 calculates the temporary average blood pressure value with the following equation.
Temporary average blood pressure value=temporary diastolic blood pressure+(temporary systolic blood pressure−temporary diastolic blood pressure)/3 [Equation 3]
After executing steps S2109 to S2110, the CPU 2120 determines the ratios α, β for determining blood pressure calculation parameters corresponding to the temporary average blood pressure value based on FIG. 3, determines the blood pressure calculation parameter obtained by multiplying the ratios α, β to the maximum value of the pressure pulse wave amplitude as the optimized blood pressure calculation parameter, and uses the optimized blood pressure calculation parameter to again carry out the blood pressure calculation in step S2111.
In the present embodiment, the temporary average blood pressure value is divided into a plurality of (e.g., three) sections for every predetermined range, where the ratio α for determining systolic blood pressure calculation parameter and the ratio β for determining diastolic blood pressure calculation parameter are set in advance for each section.
For the ratio α, the section smaller than 100 mmHg is the largest or 55%, and the ratio α becomes smaller as the temporary average blood pressure value becomes greater. For example, it is the smallest or 45% in the section of greater than or equal to 150 mmHg.
For the ratio β, on the other hand, the section of the section smaller than 100 mmHg is the smallest or 60%, and the ratio β becomes greater as the temporary average blood pressure value becomes greater. For example, it is the largest or 80% in the section of greater than or equal to 150 mmHg.
As described above, the ratios α,β are classified based on the temporary average blood pressure value, but may be classified based on any of the temporary systolic blood pressure value and the temporary diastolic blood pressure value, or two or more of the plurality of blood pressure values.
Furthermore, the ratios may be classified with the cuff pressure at which the pulse wave amplitude becomes a maximum value.
Moreover, the blood pressure calculation parameter may be calculated with the following equation using any of the temporary systolic blood pressure, the temporary diastolic blood pressure, temporary average blood pressure, and the cuff pressure at which to become the maximum value of the pulse wave amplitude.
Systolic blood pressure calculation parameter P_SBP=Ψ×P ² +ω×P+ε
Diastolic blood pressure calculation parameter P_DBP=δ×P ² +π×P+ρ [Equation 4]
Here, P indicates any of the temporary systolic blood pressure, the temporary diastolic blood pressure, temporary average blood pressure, or the cuff pressure at which to become the maximum value of the pulse wave amplitude, and Ψ, ω, ε, δ, π, ρ each indicate a predetermined coefficient determined by the cuff compliance.
An embodiment in which the temporarily determined blood pressure value is temporarily determined during pressurization by the standard blood pressure calculation parameter will be described according to a flowchart of FIG. 4 as another example of the blood pressure measurement operation.
FIG. 4 is a flowchart showing one example of the blood pressure measurement operation in the first embodiment. In each embodiment described below, the calculation in the CPU 2120 mainly differs, but the hardware configuration of the electronic sphygmomanometer 2100 is substantially similar to the embodiment described above, and hence, the configuration of each unit will be described using the reference numerals of FIG. 1.
First, when the power supply switch 2131 of the sphygmomanometer is pushed (step S2121), the CPU 2120 initializes the operation memory of the sphygmomanometer, and carries out 0 mmHg adjustment of the pressure sensor 2103 (step S2122).
The user whose blood pressure is to be measured is then selected (step S2123), and the measurement switch 2132 is pushed (step S2124), so that the CPU 2120 gradually pressurizes the cuff pressure with the pump 2104 (step S2125). The CPU 2120 extracts the pressure change component involved in the volume change of the artery superimposed on the cuff pressure obtained during pressurization, and calculates the temporary blood pressure value through a predetermined calculation (step S2126). After pressurizing up to a predetermined pressure (step S2127), the CPU 2120 optimizes the blood pressure calculation parameter with the temporary blood pressure value calculated during pressurization (step S2128).
The CPU 2120 then gradually depressurizes the cuff pressure with the valve 2105 (step S2129). The CPU 2120 extracts the pressure change component involved in the volume change of the artery superimposed on the cuff pressure obtained during depressurization, and calculates the blood pressure value through a predetermined calculation using the optimized blood pressure calculation parameter (step S2130). After calculating the blood pressure value (step S2131), the CPU 2120 opens the valve 2105 to exhaust the air in the cuff. The CPU 2120 displays the calculated blood pressure value on the display unit 2121 (step S2132), and records the same in the memory (for recording) 2123 in association with the measurement date and time and the user (step S2133).
The optimization process of the blood pressure calculation parameter is the process similar to the process described above, and thus, the description thereof will not be given.
An embodiment in which the temporarily determined blood pressure value is the blood pressure value recorded in the memory (for recording) 2123 will now be described according to a flowchart of FIG. 5 as another example of the blood pressure measurement operation.
FIG. 5 is a flowchart showing one example of the blood pressure measurement operation in the first embodiment.
When the power supply switch 2131 of the sphygmomanometer is pushed (step S2141), the CPU 2120 initializes the operation memory of the sphygmomanometer, and carries out 0 mmHg adjustment of the pressure sensor 2103 (step S2142).
The user whose blood pressure is to be measured is then selected (step S2143), and the measurement switch 2132 is pushed (step S2144), so that the CPU 2120 reads out the immediate recording value of the selected user from the memory (for recording) 2123 (step S2145), and optimizes the blood pressure calculation parameter based on such a recording value (step S2146).
The CPU 2120 then gradually pressurizes the cuff pressure with the pump 2104 (step S2147). After pressurizing up to a predetermined pressure (step S2148), the CPU 2120 gradually depressurizes the cuff pressure with the valve 2105 (step S2149).
The CPU 2120 extracts the pressure change component involved in the volume change of the artery superimposed on the cuff pressure obtained during depressurization, and calculates the blood pressure value through a predetermined calculation using the optimized blood pressure calculation parameter (step S2150). After calculating the blood pressure value (step S2151: YES), the CPU 2120 opens the valve 2105 to exhaust the air in the cuff. The CPU 2120 displays the calculated blood pressure value on the display unit 2121 (step S2152), and records the same in the memory (for recording) 2123 in association with the measurement date and time and the user (step S2153).
The optimization process of the blood pressure calculation parameter is the process similar to the process described above, and thus the description thereof will not be given.
The recording value used to optimize the blood pressure calculation parameter may be an average value or a representative value of two or more immediate recording values.
The recording value may use a value recorded in an external recording medium (external memory 2172 such as USB memory) or a personal computer, or a server via the Internet.
As described above, according to one or more embodiments of the present invention, an electronic sphygmomanometer 2100 includes biological information acquiring means for measuring a blood pressure value, recording means (memory 2123) for recording the blood pressure value, means (memory 2122) for storing a ratio for determining blood pressure calculation parameters and a control program of a sphygmomanometer, operation means (operation unit 2130) for carrying out operations such as blood pressure measurement, correction means (CPU 2120) for correcting the blood pressure value acquired by the biological information acquiring means based on measurement state related information related to the state of the user and/or the state of the cuff 2101 at the time of the blood pressure measurement, and output means (display unit 2121) for outputting the corrected information (blood pressure value) after the correction, the biological information acquiring means including a cuff 2101 to be attached to a blood pressure measurement site, pressurization and depressurization means 2104, 2105 for adjusting the pressure to apply on the cuff 2101, pressure detection means (pressure sensor 2103) for detecting a pressure in the cuff, and blood pressure calculation means (CPU 2120) for calculating a blood pressure value from the cuff pressure, wherein the blood pressure calculation means (CPU 2120) is adapted to calculate the blood pressure calculation parameter based on a predetermined calculation of multiplying a ratio α serving as a first constant and a ratio β serving as a second constant set in advance with respect to a maximum value (change) of a pressure pulse wave amplitude indicating a volume change of an artery at the time of the blood pressure measurement; and includes information acquiring means (CPU 2120 for executing steps S2108, S2126, S2145) for acquiring information of the temporarily determined blood pressure value for the measurement state related information of the user; and the correction means (CPU 2120 for executing steps S2110, S2128, S2146) is adapted to correct the blood pressure calculation parameter by correcting the ratios α, β based on the temporarily determined blood pressure value.
According to the configuration described above, an optimum blood pressure calculation parameter is set for every blood pressure value of the user, and the measurement error can be reduced.

Second Embodiment

A second embodiment in which an offset correction value (third and fourth constants) related to the component of the background pulse wave is corrected by a measurement state related information related to the state of the user and/or the state of the cuff 2101 at the time of the blood pressure measurement to reduce the measurement error will be described according to a flowchart of FIG. 6.
FIG. 6 is a flowchart showing one example of the blood pressure measurement operation in the second embodiment.
First, when the power supply switch 2131 of the sphygmomanometer is pushed (step S2161), the CPU 2120 initializes the operation memory of the sphygmomanometer, and carries out 0 mmHg adjustment of the pressure sensor 2103 (step S2162).
The user whose blood pressure is to be measured is then selected (step S2163), and the measurement switch 2132 is pushed (step S2164), so that the CPU 2120 gradually pressurizes the cuff pressure with the pump 2104 (step S2165 to step S2166), and gradually depressurizes the cuff pressure with the valve 2105 (step S2167).
The CPU 2120 extracts the pressure change component involved in the volume change of the artery superimposed on the cuff pressure obtained during depressurization, and calculates the temporary systolic blood pressure value and the temporary diastolic blood pressure value through a predetermined calculation shown in the following [Equation 5] (step S2168).
T_AmpSys=maximum value of pressure pulse wave amplitude×α+ζtsys
T_AmpDia=maximum value of pressure pulse wave amplitude×β+ηtdia [Equation 5]
Here, T_AmpSys in [Equation 5] is the temporary systolic blood pressure calculation parameter, and T_AmpDia is the temporary diastolic blood pressure calculation parameter. Furthermore, ζtsys and ηtdia are offset correction values (third and fourth constants) related to the component of the background pulse wave generated when the pressure in the cuff 2101 is pressurized to a predetermined pressure outside the blood pressure value measurement range, and are values determined through experiment in advance.
The CPU 2120 determines the cuff pressure at a point the T_AmpSys calculated in step S2168 intersects the envelope curve shown in FIG. 9 as the temporary systolic blood pressure value, and the cuff pressure at a point the T_AmpDia calculated in step S2168 intersects the envelope curve shown in FIG. 9 as the temporary diastolic blood pressure value.
The CPU 2120 then corrects the offset correction value ζ (third constant) and the offset correction value η (fourth constant) related to the component of the background pulse wave in [Equation 5] with the temporary systolic blood pressure value and the temporary diastolic blood pressure value determined in step S2168. As shown in FIG. 13, the component of the background pulse wave becomes smaller as the cuff pressure becomes higher, so that the offset correction value is corrected through a predetermined calculation shown in the following [Equation 6] (step S2169).
ζ=ζtsys+temporary systolic blood pressure value×θ
η=ηtdia+temporary diastolic blood pressure value×ι [Equation 6]
Here, θ and ι in [Equation 6] are values determined through experiment in advance.
The CPU 2120 calculates the systolic blood pressure calculation parameter and the diastolic blood pressure calculation parameter through a predetermined calculation shown in the following [Equation 7] in which ζ, η corrected in step S2169 are replaced with ζtsys, ηtdia of [Equation 5] and optimizes the same (step S2170).
Systolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×α+ζ
Diastolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×β+η [Equation 7]
Similar to the case of the temporary systolic blood pressure value and the temporary diastolic blood pressure value, the CPU 2120 determines the cuff pressure at a point the systolic blood pressure calculation parameter and the diastolic blood pressure calculation parameter calculated in step S2170 intersect the envelope curve as the systolic blood pressure value and the diastolic blood pressure value (step S2171).
The CPU 2120 displays the calculated blood pressure value on the display unit 2121 (step S2172), and records the same in the memory (for recording) 2123 in association with the measurement date and time and the user (step S2173).
As described above, according to one or more embodiments of the present invention, an electronic sphygmomanometer 2100 includes biological information acquiring means for measuring a blood pressure value, recording means (memory 2123) for recording the blood pressure value, means (memory 2122) for storing a control program of the sphygmomanometer, operation means (operation unit 2130) for performing operations such as blood pressure measurement, correction means (CPU 2120) for correcting the blood pressure value based on a component of a background pulse wave generated when the pressure of a cuff 2101 is pressurized to a predetermined pressure outside a blood pressure value measurement range, and output means (display unit 2121) for outputting corrected information (blood pressure value) after the correction, the biological information acquiring means including a cuff 2101 to be attached to a blood pressure measurement site, pressurization and depressurization means 2104, 2105 for adjusting pressure to apply on the cuff 2101, pressure detection means (pressure sensor 2103) for detecting a pressure in the cuff, and blood pressure calculation means (CPU 2120) for calculating the blood pressure value from the cuff pressure; wherein the blood pressure calculation means (CPU 2120) is adapted to multiply a ratio α serving as a first constant set in advance with respect to a maximum value (change) of a pressure pulse wave amplitude indicating a volume change of an artery at the time of the blood pressure measurement and calculate a systolic blood pressure calculation parameter based on a predetermined calculation of adding an offset correction value ζ serving as a third constant related to the component of the background pulse wave, and also multiply a ratio β serving as a second constant set in advance with respect to a maximum value (change) of the pressure pulse wave amplitude and calculate a diastolic blood pressure calculation parameter based on a predetermined calculation of adding an offset correction value η serving as a fourth constant related to the component of the background pulse wave, and includes information acquiring means (CPU 2120 that executes step S2168) for acquiring information of a temporary systolic blood pressure value and a temporary diastolic blood pressure value as measurement state related information related to the state of the user at the time of the blood pressure measurement; and the correction means (CPU 2120 that executes step S2169) is adapted to correct the blood pressure calculation parameters by correcting the offset correction values ζ, η of the blood pressure value based on the information of the temporary systolic blood pressure value and the temporary diastolic blood pressure value.
According to one or more embodiments of the present invention, the offset correction values ζ, η related to the component of the background pulse wave can be corrected for every state (blood pressure value of the user in the present embodiment) of the user at the time of the blood pressure measurement, so that an accurate blood pressure value can be calculated while suppressing the influence of error caused by the component of the background pulse wave.
In the above description, the offset correction values (third and fourth constants) are determined by multiplying a predetermined ratio with respect to the temporary systolic blood pressure value and the temporary diastolic blood pressure value, but an offset correction value determination (for determining third and fourth constants) table corresponding to the temporary systolic blood pressure value and the temporary diastolic blood pressure value may be stored in the memory 2123 of the electronic sphygmomanometer 2100, and the offset correction values (third and fourth constants) may be read out from the table.
An embodiment of correcting the offset correction value based on the maximum value of the cuff pressure will now be described as another example of the blood pressure measurement operation.
Generally, the determination method of the blood pressure value of an oscillometric method includes the following.
First, there is a method (hereinafter referred to as depressurization measuring method) of determining the blood pressure value during the depressurization of the cuff pressure, in which depressurization measuring method, the cuff pressure is pressurized to a pressure higher than a predetermined pressure, where a point the pressure pulse wave amplitude rapidly increases while the cuff pressure is gradually depressurized is determined as the systolic blood pressure value, and a point the pressure pulse wave rapidly decreases while the cuff pressure is further gradually depressurized is determined as the diastolic blood pressure value.
There is also a method (hereinafter referred to as pressurization measuring method) of determining the blood pressure value during the pressurization of the cuff 2101, in which pressurization measuring method, the cuff is gradually pressurized, and a point the pressure pulse wave amplitude rapidly increases in the process is determined as the diastolic blood pressure value, and a point the pressure pulse wave rapidly decreases while the cuff pressure is gradually depressurized is determined as the systolic blood pressure value.
In the case of the depressurization measuring method, the cuff pressure is pressurized to a pressure higher by a predetermined pressure (e.g., 30 mmHg) than the measurement range, where the pressure value thereof is defined as a cuff pressure maximum value Pcmax in the present embodiment. In the blood pressure measurement device of the pressurization measuring method, pressurization is carried out until the pressure pulse wave amplitude information necessary for determining the systolic blood pressure value is detected while gradually pressurizing the cuff pressure. After the systolic blood pressure value is determined, the pressurization is stopped, and the cuff pressure is rapidly depressurized with the valve 2105, where the cuff pressure immediately before the start of the depressurization is defined as a cuff pressure maximum value Pcmax in the present embodiment.
In the present embodiment, the CPU 2120 corrects the offset correction values ζ, η indicating the component of the background pulse wave through a predetermined calculation shown in the following [Equation 8] based on the Pcmax. In the present embodiment, the offset correction values ζ, η are corrected using the offset correction values ζtsys, ηtdia shown in [Equation 5], as shown in the following [Equation 8].
ζ=ζtsys+Pcmax×κ
η=ηtdia+Pcmax×λ [Equation 8]
Here, κ and λ in [Equation 8] are values determined through experiment in advance. In the present embodiment, the offset correction values ζ, η corrected with [Equation 8] are applied to [Equation 7], similar to the embodiment shown in FIG. 6, to calculate and optimize the systolic blood pressure calculation parameter and the diastolic blood pressure calculation parameter thereby determining the blood pressure value.
In the present embodiment, the offset correction value determination (third and fourth constant determination) table in which the offset correction value and the Pcmax are corresponded may be recorded in advance in the memory 2123 of the electronic sphygmomanometer 2100, and the offset correction values (third and fourth constants) may be read out from the table.
Therefore, an accurate blood pressure value can be calculated while suppressing the influence of the error caused by the difference in the maximum value Pcmax of the cuff pressure by correcting the offset correction values ζ, η based on the information of the maximum value Pcmax of the cuff pressure.
An embodiment of correcting the offset correction value based on the maximum value of the pressure pulse wave amplitude will now be described as another example of the blood pressure measurement operation.
In the present embodiment, the cuff pressure at a point the pressure pulse wave amplitude becomes a maximum (AmpMax) is defined as Pcamp in the envelope curve shown in FIG. 9. The CPU 2120 corrects the offset correction values ζ, η indicating the component of the background pulse wave according to a predetermined calculation shown in the following [Equation 9] based on the Pcamp.
ζ=ζtsys+Pcamp×μ
η=ηtdia+Pcamp×ν [Equation 9]
Here, μ and ν in [Equation 9] are values determined through experiments in advance. The optimization process of the blood pressure calculation parameter herein is the process similar to the process described above, and thus the description thereof will not be given.
In the present embodiment, the offset correction value determination (third and fourth constant determination) table in which the offset correction value and the Pcamp are corresponded may be recorded in advance in the memory 2123 of the electronic sphygmomanometer 2100, and the offset correction values may be read out from the table.
Therefore, an accurate blood pressure value can be calculated while suppressing the influence of the error caused by the difference in the maximum value of the pressure pulse wave amplitude by correcting the offset correction values ζ, η based on the information of the Pcamp or the cuff pressure at the point the pressure pulse wave amplitude becomes a maximum (AmpMax).
Next, an embodiment of correcting the offset correction values based on the wrapping strength of the cuff 2101 will be described as another example of the blood pressure measurement operation.
In the case of the electronic sphygmomanometer 2100, as compared to the case when the cuff 2101 is appropriately wrapped around the measurement site such as the arm A (see FIG. 12) so as not to form a space, a great amount of air needs to be flowed into the air bladder in the cuff 2101 to apply the same pressure to the measurement site when a space is formed between the measurement site and the cuff 2101.
As described above, the pressure pulse wave amplitude detects the volume change of the cuff 2101 that occurs with the volume change of the artery B (see FIG. 12) as the pressure change, and hence the pressure pulse wave amplitude changes by the air volume in the cuff 2101, even if it is the volume change of the same artery, where the pressure pulse wave amplitude becomes smaller the greater the air volume. Therefore, the component of the background pulse wave changes according to the wrapping strength of the cuff 2101.
The offset correction values of [Equation 7] thus need to be corrected based on the wrapping strength of the cuff 2101. In the present embodiment, the CPU 2120 calculates the systolic blood pressure calculation parameter and the diastolic blood pressure calculation parameter through a predetermined calculation shown in the following [Equation 10] in which the correction by the manner of wrapping the cuff 2101 is added to [Equation 7], and optimizes the same. In other words, in the present embodiment, a predetermined ratio ξ is multiplied to the offset correction value ζ to correct the same, and a predetermined ratio σ is multiplied to the offset correction value η to correct the same.
Systolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×α+ζ×ξ
Diastolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×β+η×σ [Equation 10]
Here, ξ and σ in [Equation 10] are values determined through experiments in advance. Such values may be determined through a method of recording the offset correction value determination (third and fourth constant correction) table in which the values are corresponded with the wrapping strength of the cuff 2101 in the memory 2123 of the electronic sphygmomanometer 2100 in advance and reading out the values from the table.
The wrapping strength of the cuff 2101 may be detected by the proportion of the change in cuff pressure when pressurizing the cuff 2101 using the known technique described Japanese Unexamined Patent Publication No. 62-84738, Japanese Unexamined Patent Publication No. 5-62538, and Japanese Patent No. 4134234.
Therefore, by correcting the offset correction values ζ, η based on the information of the wrapping strength of the cuff 2101, an accurate blood pressure value can be calculated while suppressing the influence of the error caused by the difference in air volume in the cuff 2101 that occurs from the difference in the wrapping strength.
An embodiment of correcting the offset correction values based on specifications (size) of the cuff 2101 will now be described as another example of the blood pressure measurement operation.
In the case of the electronic sphygmomanometer 2100, the attenuation of the pressure transmission to the artery B becomes greater the longer the peripheral length of the measurement site. Therefore, the cuff 2101 of an appropriate size needs to be selected according to the peripheral length of the measurement site to carry out accurate blood pressure measurement. In other words, the width (direction orthogonal to the peripheral direction of the measurement site) and the length (peripheral direction of the measurement site) of the cuff 2101 need to be longer the longer the peripheral length of the measurement site. The width and the length of the cuff suitable for the peripheral length of the measurement site are advised/recommended in WHO (World Health Organization) or the like.
As the size (width, length) of the size 2101 becomes longer the longer the peripheral length of the measurement site, the size of the air bladder in the cuff 2101 also becomes greater therewith. Therefore, the pressure pulse wave amplitude to be detected becomes smaller when the size of the cuff 2101 becomes greater, so that the component of the background pulse wave also becomes smaller (see FIG. 7).
Therefore, the offset correction values of [Equation 7] need to be corrected with the size of the cuff 2101. In the present embodiment, the CPU 2120 calculates the systolic blood pressure calculation parameter and the diastolic blood pressure calculation parameter through a predetermined calculation shown in the following [Equation 11] in which the correction by the size of the cuff 2101 is added to [Equation 7], and optimizes the same. In other words, in the present embodiment, a predetermined ratio τ is multiplied to the offset correction value ζ correct the same, and a predetermined ratio υ is multiplied to the offset correction value η to correct the same.
Systolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×α+ζ×τ
Diastolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×β+η×υ [Equation 11]
Here, τ and υ in [Equation 11] are values determined through experiments in advance. Such values may be determined through a method of recording the offset correction value determination (third and fourth constant correction) table in which the values are corresponded with the size of the cuff 2101 in the memory 2123 of the electronic sphygmomanometer 2100 in advance and reading out the values from the table.
Therefore, an accurate blood pressure value can be calculated while suppressing the influence of the error caused by the difference in size of the air bladder in the cuff 2101 by correcting the offset correction values ζ, η based on the information of the size of the cuff 2101.
The size of the cuff 2101 may be inputted before the measurement with a switch, the switch being arranged in the input unit such as the operation unit 2130, or may be automatically detected by arranging a sensor for detecting the size of the cuff 2101 at the connecting portion with the cuff 2101 of the main body of the electronic sphygmomanometer 2100.
By arranging a switch in the input unit such as the operation unit 2130, and enabling various types of information such as the size of the cuff 2101 to be inputted before the measurement, various types of information necessary for the calculation of the blood pressure value can be easily acquired in advance, and the time required for the blood pressure measurement can be shortened.
As the air volume to be flowed into the cuff 2101 until a predetermined cuff pressure is reached becomes large in accordance with the increase in the size of the cuff 2101, the elapsed time thereof also becomes longer. Therefore, the time until the predetermined cuff pressure is reached may be measured based on the change in the cuff pressure in one blood pressure measurement, and the size of the cuff 2101 may be detected based on such time.
Therefore, various types of information can be acquired with a simple configuration without separately arranging the input unit, the sensor or the like for inputting various types of information necessary for the calculation of the blood pressure value such as the size of the cuff 2101.
The case of correcting the offset correction values ζ, η based on the information related to the size of the cuff 2101 of the information related to the specifications of the cuff 2101 has been described, but the correction may also be carried out based on the information related to the type such as structure and material of the information related to the specifications of the cuff 2101. For example, with respect to the cuff in which the structure of the air bladder in the cuff 2101 is a single structure like a balloon and the cuff in which a gore structure is provided at the side surface of the air bladder as described in Japanese Patent No. 3747917, the volume of air to be flowed into the air bladder so that the cuff 2101 reaches the predetermined inner pressure is greater for the latter cuff. Furthermore, the volume of air to be flowed into the air bladder so that the cuff 2101 reaches the predetermined inner pressure is greater the softer the material of the air bladder in the cuff 2101.
In contrast, by correcting the offset correction values ζ, η based on the information related to the type of the cuff 2101, an accurate blood pressure value can be calculated while suppressing the influence of the error caused by the difference in the air volume by the type of the cuff 2101.
As described above, the size of the cuff 2101 used for the measurement becomes greater the longer the peripheral length of the measurement site. Therefore, the offset correction values (third and fourth constants) of [Equation 11] may be corrected by the peripheral length of the measurement site based on the fact that the component of the background pulse wave changes in accordance with the size of the cuff 2101 as shown in FIG. 8. Thus, an accurate blood pressure value can be calculated while suppressing the influence of the error caused by the difference in the size of the cuff 2101.
The expansion of the air bladder in the cuff 2101 becomes greater the softer the quality of the measurement site. In this case, a state same as the state in which there is a space between the measurement site and the cuff 2101 is realized, and the pressure pulse wave amplitude becomes small. Therefore, the correction may be carried out by the quality of the measurement site. An accurate blood pressure value thus can be calculated while suppressing the influence of the error caused by the difference in the expansion of the air bladder of the cuff 2101.
In this case, the peripheral length or the quality of the measurement site may be inputted from the input unit such as the operation unit 2130, or the time until reaching the predetermined cuff pressure may be measured based on the change in the cuff pressure in one blood pressure measurement and the peripheral length or the quality may be detected based on such time. The input of the quality of the measurement site may be substituted with BMI (Body Mass Index), body fat percentage, or the like. For example, determination is made that a great amount of fat exists at the measurement site if the body fat percentage is large, and correction can be made assuming the quality of the measurement site is soft.
Therefore, the information related to the measurement site can be acquired with a simple configuration without separately arranging the input unit, the sensor or the like for inputting various types of information related to the measurement site.
An embodiment of correcting the offset correction values based on the user information inputted before the start of the blood pressure measurement will now be described as another example of the blood pressure measurement operation.
In the case of the electronic sphygmomanometer 2100, the shape of the envelope curve shown in FIG. 9 is determined in accordance with the dynamical properties of the artery. FIG. 14 is a graph showing an example of the dynamical properties of the artery, where one of the factors for determining the dynamical properties of the artery as shown in FIG. 14 includes arterial elasticity. The elasticity of the artery depends on the age and the disease (particularly arterial sclerosis), and the arterial elasticity becomes harder with aging and advancement in disease. When the arterial elasticity becomes hard, the artery is almost impossible to be pressure closed even if it is compressed with the cuff 2101, and thus, the background pulse wave exists until the cuff pressure becomes high compared to a person with soft arterial elasticity.
The age and disease information are inputted in advance, and the offset correction values ζ, η of [Equation 7] are corrected with the age and disease information. In the present embodiment, the input of the age and disease information is permitted with the input unit such as the operation unit 2130, and the CPU 2120 calculates the systolic blood pressure calculation parameter and the diastolic blood pressure calculation parameter through a predetermined calculation shown in the following [Equation 12] in which the correction based on the inputted age and disease information is added to [Equation 7], and optimizes the same. In other words, in the present embodiment, a predetermined ratio φ is multiplied to the offset correction value ζ to correct the same, and a predetermined ratio χ is multiplied to the offset correction value η to correct the same.
Systolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×α+ζ×φ
Diastolic blood pressure calculation parameter=maximum value of pressure pulse wave amplitude×β+η×χ [Equation 12]
Here, φ and χ in [Equation 12] are values determined through experiments in advance. Such values may be determined through a method of recording the offset correction value determination table in which the values are corresponded with the age and disease information in the memory 2123 of the electronic sphygmomanometer 2100 in advance and reading out the values from the table.
The age and disease information may be inputted by the operation unit 2130 at the start of the measurement. The user and the age or disease information may be recorded in the memory 2123 in association with each other, and the information may be read from the memory 2123 by selecting the user by the operation unit 2130 at the start of the measurement. The age and disease information may be recorded in a medium such as the external memory 2172, and the information may be read out at the start of the measurement.
In the case of the present embodiment, the time until reaching a predetermined cuff pressure is measured based on the change in the cuff pressure in one blood pressure measurement, the elasticity of the artery B of the user is detected based on the time, and the disease information (in this case, information of arterial sclerosis) may be acquired based on the detection result.
Therefore, an accurate blood pressure value can be calculated while suppressing the influence of the error caused by the difference in elasticity of the artery B by correcting the offset correction values ζ, η based on the age and disease information of the user.
Embodiments of the present invention are not limited only to the configuration of the above-described embodiments, and a great number of embodiments can be realized.
For example, the electronic sphygmomanometer 2100 may be configured to download an appropriate parameter, threshold value, algorithm, or the like from a dedicated server to expand the function. In this case, the version of the software may be upgraded with the hardware as is, or optimization can be easily realized by the user himself/herself.
The function expansion of the electronic sphygmomanometer 2100 may be executed from a user terminal such as a personal computer possessed by the user without using the server. In this case, the parameter, the threshold value, the algorithm, and the like may be downloaded from a recording medium such as a CD-ROM.
The electronic sphygmomanometer 2100 may be directly and communicably connected wirelessly or by wire to other biological information acquiring device such as a body composition meter, a pedometer, or an electronic thermometer. In this case as well, data may be mutually transmitted and received to enhance the individual accuracy.
Embodiments of the present invention can be used in an electronic sphygmomanometer adopting an oscillometric method that uses a cuff.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

DESCRIPTION OF REFERENCE NUMERALS

2100 electronic sphygmomanometer
2101 cuff
2103 pressure sensor
2104 pump
2105 valve
2120 CPU
2121 display unit
2122 memory (for processing)
2123 memory (for recording)
2130 operation unit

Claims

1. An electronic sphygmomanometer comprising:

a cuff to be attached to a blood pressure measurement site;

pressurization and depressurization means for adjusting a pressure to apply on the cuff;

pressure detection means for detecting a pressure in the cuff;

blood pressure calculation means for calculating a blood pressure value from a cuff pressure;

recording means for recording the blood pressure value; and

operation means for performing a blood pressure measurement;

wherein the blood pressure calculation means comprises a configuration that calculates a blood pressure calculation parameter based on a predetermined calculation of multiplying a constant with respect to a maximum value of a pressure pulse wave amplitude indicating a volume change of an artery at a time of blood pressure measurement, and

wherein the electronic sphygmomanometer further comprises:

information acquiring means for separately acquiring measurement state related information related to a state of a user and/or a state of the cuff at the time of blood pressure measurement; and

correction means for correcting the blood pressure calculation parameter by correcting the constant based on the measurement state related information when the measurement state related information is acquired by the information acquiring means,

wherein the information acquiring means comprises a configuration that acquires information of a temporarily determined blood pressure value as the measurement state related information related to the state of the user, and

wherein the correction means comprises a configuration that corrects the constant based on the temporarily determined blood pressure value.

2. The electronic sphygmomanometer according to claim 1,

wherein the blood pressure calculation means comprises a configuration that calculates a systolic blood pressure calculation parameter based on a predetermined calculation of multiplying a first constant to a maximum value of the pressure pulse wave amplitude, and adding a third constant related to a component of a background pulse wave generated when the pressure of the cuff is pressurized to a predetermined pressure outside a blood pressure value measurement range,

wherein the blood pressure calculation means comprises a configuration that calculates a diastolic blood pressure calculation parameter based on a predetermined calculation of multiplying a second constant to the maximum value of the pressure pulse wave amplitude and adding a fourth constant related to a component of the background pulse wave, and

wherein the correction means corrects the third and fourth constants based on the measurement state related information.

3. The electronic sphygmomanometer according to claim 2,

wherein the correction means comprises a configuration that corrects the first and second constants or the third and fourth constants based on the temporarily determined blood pressure value.

4. The electronic sphygmomanometer according to claim 2,

wherein the information acquiring means comprises a configuration that acquires information of a maximum value of the cuff pressure as the measurement state related information, and

wherein the correction means comprises a configuration that corrects the first and second constants or the third and fourth constants based on the maximum value of the cuff pressure.

5. The electronic sphygmomanometer according to claim 2,

wherein the information acquiring means comprises a configuration that acquires information of a maximum value of the pressure pulse wave amplitude as the measurement state related information related to the state of the user, and

wherein the correction means comprises a configuration that corrects the first and second constants or the third and fourth constants based on the maximum value of the pressure pulse wave amplitude.

6. The electronic sphygmomanometer according to claim 2,

wherein the information acquiring means comprises a configuration that acquires information of a wrapping strength of the cuff as the measurement state related information, and

wherein the correction means comprises a configuration that corrects the first and second constants or the third and fourth constants based on the information of the wrapping strength of the cuff.

7. The electronic sphygmomanometer according to claim 2,

wherein the information acquiring means comprises a configuration that acquires cuff specification information related to a size and/or a type of the cuff as the measurement state related information, and

wherein the correction means comprises a configuration that corrects the first and second constants or the third and fourth constants based on the cuff specification information.

8. The electronic sphygmomanometer according to claim 2,

wherein the information acquiring means comprises a configuration that acquires information related to a measurement site of the user as the measurement state related information, and

wherein the correction means comprises a configuration that corrects the first and second constants or the third and fourth constants based on the information related to the measurement site of the user.

9. The electronic sphygmomanometer according to claim 2,

wherein the information acquiring means comprises a configuration that acquires disease information of the user as the measurement state related information, and

wherein the correction means comprises a configuration that corrects the first and second constants or the third and fourth constants based on the disease information of the user.

10. The electronic sphygmomanometer according to claim 2,

wherein the information acquiring means comprises a configuration that acquires age information of the user as the measurement state related information, and

wherein the correction means comprises a configuration that corrects the first and second constants or the third and fourth constants based on the age information of the user.

11. The electronic sphygmomanometer according to claim 2,

wherein the information acquiring means comprises a configuration that acquires the measurement state related information based on a detection of a change in an inner pressure of the cuff.

12. The electronic sphygmomanometer according to claim 2, further comprising:

input means for permitting input of the measurement state related information by the user;

wherein the information acquiring means comprises a configuration that acquires the measurement state related information inputted before the start of the blood pressure measurement.

13. A blood pressure measurement method for adjusting a pressure to apply on a cuff when the cuff is attached to a blood pressure measurement site with pressurization and depressurization means, and calculating a blood pressure value with blood pressure calculation means based on the cuff pressure detected by pressure detection means, the method comprising the steps of:

calculating a blood pressure calculation parameter by executing a predetermined calculation using a constant set in advance with respect to a maximum value of a pressure pulse wave amplitude indicating a volume change of an artery at a time of blood pressure measurement in the blood pressure calculation means;

separately acquiring measurement state related information related to a state of a user and/or a state of the cuff at the time of blood pressure measurement with information acquiring means; and

correcting the blood pressure calculation parameter by correcting the constant with correction means based on the measurement state related information when the measurement state related information is acquired by the information acquiring means,

wherein the step of calculating the blood pressure calculation parameter by the blood pressure calculation means comprises calculating the blood pressure calculation parameter based on a predetermined calculation of multiplying the constant to the maximum value of the pressure pulse wave amplitude, and

wherein the step of correcting by the correction means comprises:

acquiring information of a temporarily determined blood pressure value as the measurement state related information related to the state of the user by the information acquiring means; and

correcting the constant based on the temporarily determined blood pressure value.

14. The blood pressure measurement method according to claim 13,

wherein the step of calculating the blood pressure calculation parameter by the blood pressure calculation means further comprises:

calculating a systolic blood pressure calculation parameter based on a predetermined calculation of multiplying a first constant to a maximum value of the pressure pulse wave amplitude and adding a third constant related to a component of a background pulse wave; and

calculating a diastolic blood pressure calculation parameter based on a predetermined calculation of multiplying a second constant to the maximum value of the pressure pulse wave amplitude and adding a fourth constant related to a component of the background pulse wave, and

wherein the step of correcting by the correction means comprises correcting the third and fourth constants based on the measurement state related information.