JP4117211B2 - Vascular elasticity measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vascular elasticity measuring apparatus capable of obtaining an arteriosclerosis index of a blood vessel at the time of blood pressure measurement by a noninvasive method.
[0002]
[Prior art]
It is known that the cause of heart disease (such as myocardial infarction), which is the second leading cause of death in Japanese, and cerebrovascular disorder (such as stroke), which is the third leading cause, is vascular arteriosclerosis. Curing has become a familiar issue for us.
[0003]
However, it is difficult to know the index of arteriosclerosis at home, and it is necessary to have a specialized examination at the hospital, so healthy people and those without subjective symptoms should first take such examinations voluntarily. Do not think. This potentially causes various diseases to progress, and in the worst case, it is too late.
[0004]
Therefore, it is easy to know the degree and tendency of arteriosclerosis and know about arteriosclerosis easily and easily at home or outpatient visits without measuring detailed numerical values of arteriosclerosis indicators at hospital special examinations etc. The need for opportunity is increasing.
[0005]
Conventionally, in the process of measuring blood pressure by a non-invasive method, there has been an apparatus capable of obtaining an arteriosclerosis index, that is, an elastic characteristic of a blood vessel simultaneously with blood pressure (see, for example, Patent Document 1 and Patent Document 2). .
[0006]
[Patent Document 1]
Japanese Patent No. 3184349
[Patent Document 2]
JP-A-8-66377
[0007]
[Problems to be solved by the invention]
However, the devices disclosed in Patent Document 1 and Patent Document 2 require a separate device to be attached to the finger of the person to be measured in addition to the components of the conventional blood pressure monitor. There has been a trouble of developing.
[0008]
Also, from the viewpoint of the person being measured, there is no custom of measuring only the elastic properties of blood vessels at home, and in addition to the cuff (armband) necessary to measure blood pressure, the device must be attached to the finger. Due to the hassle of having to do this, devices like this tend to be shunned.
[0009]
[Means for Solving the Problems]
Therefore, in view of the above problems, the present inventor does not add anything to the hardware configuration of a sphygmomanometer of an existing method (hereinafter referred to as a pulse wave detection method) that uses a cuff to obtain blood pressure from a pulse wave. In addition, a blood vessel elasticity measuring device that can easily and easily obtain an index of vascular arteriosclerosis simultaneously with blood pressure at the time of outpatient visit is realized.
[0010]
The invention of claim 1 includes a cuff for compressing a part of a living body, cuff pressure control means for controlling the cuff pressure Po of the cuff, detection means for detecting a pressure signal in the cuff, and the cuff pressure control means. A pulse wave extraction means for detecting a pulse wave Δp by subtracting the cuff pressure Po from a signal detected by the detection means in the process of pressure reduction or pressurization control of the cuff at, and the cuff pressure control means About at least one period or two to three periods before and after detecting the pulse wave Δp Reference waveform storage means for maintaining the cuff pressure Po at a predetermined pressure and storing the waveform of the signal detected by the detection means at that time as a reference waveform pi, and blood pressure calculation for calculating the minimum blood pressure Pd and the maximum blood pressure Ps Means, and ΔP calculation means for obtaining an internal / external pressure difference ΔP which is a difference between the intravascular pressure Pi and the cuff pressure Po by converting the reference waveform pi into units by the minimum blood pressure Pd and the maximum blood pressure Ps. , In the process of detecting the pulse wave Δp, the signal detected by the detection means, Elastic characteristic function Vo / Po obtained from cuff pressure Po and volume Vo And Boyle Charles' Law Po × V0 = (Po + ΔP) × (V0−ΔV) By applying ΔV, ΔV calculating means for obtaining the volume change ΔV of the cuff by converting from a pressure unit to a volume unit, the volume change ΔV of the cuff, and the internal / external pressure difference ΔP, For each detected pulse wave in the range from at least systolic blood pressure Ps to diastolic blood pressure Pd It is a vascular elasticity measuring device having a vascular elasticity or a comparison means for obtaining an arteriosclerosis index corresponding to the vascular elasticity by comparison.
[0011]
According to the first aspect of the present invention, not only blood pressure but also an index of arteriosclerosis can be obtained simply by attaching a cuff to the subject.
[0012]
The invention of claim 2 The reference waveform pi is converted into units by the minimum blood pressure Pd and the maximum blood pressure Ps to obtain an intravascular pressure Pi, and ΔP calculating means for obtaining an internal / external pressure difference ΔP which is a difference between the intravascular pressure Pi and the cuff pressure Po is the reference After the amplitude of the reference waveform pi stored in the waveform storage means is corrected by the minimum blood pressure Pd and the maximum blood pressure Ps, the internal / external pressure difference ΔP is calculated by a method using the intravascular pressure Pi that is repeatedly generated repeatedly. Vascular elasticity measuring device
[0013]
According to the second aspect of the present invention, an index of arteriosclerosis can be obtained without making the person to be measured conscious and in almost the same time as blood pressure measurement.
[0020]
Invention of Claim 3 Is
The vascular elasticity obtained by the comparison means or the arteriosclerosis index corresponding to the vascular elasticity is shown as a related figure such as a two-dimensional graph, the slope value of the relevant figure, and the degree of arteriosclerosis corresponding to the slope value. It is a vascular elasticity measuring device which has a display means to display by at least 1 or more of a rank.
[0021]
Invention of Claim 3 Thus, the blood vessel elastic modulus and the arteriosclerosis index can be easily shown to the subject by graphs, numerical values, ranks, and the like.
[0022]
Invention of Claim 4 Is
The display means is a vascular elasticity measuring device that displays the vascular elasticity or any combination of the arteriosclerosis index corresponding to the vascular elasticity, the minimum blood pressure Pd, and the maximum blood pressure Ps simultaneously or alternately.
[0023]
Invention of Claim 4 Thus, in addition to the arteriosclerosis index, the systolic blood pressure Ps and the systolic blood pressure Pd are also displayed simultaneously or alternately, thereby making it easier to use for various diagnoses.
[0024]
Invention of Claim 5 Is
The cuff, the cuff pressure control means, the detection means, and the pulse wave extraction means are a blood vessel elasticity measurement device shared with a pulse wave detection type sphygmomanometer.
[0025]
Invention of Claim 5 Thus, the arteriosclerosis index measurement function is added to the sphygmomanometer simply by changing the display part and internal program of the sphygmomanometer of the conventional pulse wave detection method, thereby reducing the development cost. Furthermore, since it is not necessary to measure separately for blood pressure measurement and arteriosclerosis index measurement, the measurement time is almost the same as the conventional blood pressure measurement time, which is efficient.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Before describing the embodiment of the present invention in detail, as a reference, the measurement principle of an oscillometric sphygmomanometer, which is an aspect of a pulse wave detection method for calculating blood pressure from a pulse wave, will be described.
[0027]
The reason for explaining the measurement principle of the sphygmomanometer of the pulse wave detection method is that the use of the cuff and the detection of the pulse wave are indispensable for measuring the blood vessel elasticity according to the present invention. This is because it is most efficient with few hardware changes. However, the calculation of the systolic blood pressure Ps and the diastolic blood pressure Pd required in the present invention is not necessarily required by the pulse wave detection method.
[0028]
The oscillometric sphygmomanometer described below is currently most popular regardless of whether it is for home use or for business use, but the sphygmomanometer of the pulse wave detection type has a plurality other than the oscillometric type, The oscillometric method is only one aspect.
[0029]
1 includes a cuff 11, a detection unit 110, a cuff pressure control unit 13, a full waveform storage unit 15, a pulse wave extraction unit 17, a pulse wave amplitude calculation unit 19, and a blood pressure calculation unit 21. Is included. These are means generally included in a sphygmomanometer of a pulse wave detection method (oscillometric method).
[0030]
The cuff 11 is an arm band containing a bag made of an elastic material such as rubber, similar to those conventionally used for blood pressure measurement, and is wound around the upper arm or lower limb of the subject.
[0031]
The detection means 110 is a means for detecting the pressure in the cuff 11. The detection means 110 is generally constituted by a pressure sensor or the like and is fixed inside the cuff 11, but need not be a pressure sensor as long as it detects pressure.
[0032]
The cuff pressure control means 13 is a means for controlling the pressure in the cuff 11. Hereinafter, the pressure controlled by the cuff pressure control means 13 is referred to as cuff pressure Po. The cuff pressure control means 13 applies air or the like to the rubber bag in the cuff 11 via the pressurizing pump 130 so that the cuff pressure Po becomes higher than the intravascular blood pressure in the body of the measurement subject at the start of measurement. The cuff pressure control means 13 stops the pressurization when the cuff 11 presses the measurement site and blocks the blood flow in the body. Thereafter, the cuff pressure Po is gradually decreased by controlling the air in the cuff 11 to flow through the exhaust valve 131. There is also a method of measuring the blood pressure in the process of increasing the cuff pressure Po.
[0033]
First, in a process of gradually decreasing the cuff pressure Po from a state in which the measurement site is compressed by the cuff 11 and the blood vessel immediately below is crushed, blood starts to flow around the maximum blood pressure Ps, and the minimum blood pressure Pd In the vicinity, it is known to flow without being affected by the cuff pressure Po.
[0034]
In the process of changing the cuff pressure Po, the oscillometric sphygmomanometer produces a minute pressure fluctuation (hereinafter referred to as a pulse wave Δp) caused by the vibration of the blood vessel wall in synchronization with the pulsation of the heart. ), The maximum blood pressure Ps, the minimum blood pressure Pd, and the average blood pressure Pa are determined.
[0035]
Therefore, in the detection means 110, a signal (Po + Δp) obtained by superimposing the minute pulse wave Δp on the cuff pressure Po is obtained as shown in the upper part of the graph of FIG.
[0036]
All waveform storage means 15 is means for storing signals detected by the detection means 110.
[0037]
The pulse wave extraction means 17 subtracts the cuff pressure Po from the signal detected by the detection means 110 in the process of decreasing or increasing the cuff pressure Po (that is, reducing or increasing the cuff 11), and the pulse wave Δp It is a means to detect only. The lower part of the graph of FIG. 2 is a signal obtained by enlarging the vertical axis of the pulse wave Δp detected by the pulse wave extraction means 17. Note that the detected pulse wave Δp is appropriately subjected to amplification, waveform shaping, noise removal, etc., in order to perform subsequent processing smoothly.
[0038]
The pulse wave amplitude calculating means 19 is means for calculating the amplitude for each period of the pulse wave Δp (synonymous with the beat, hereinafter the same) (hereinafter also simply referred to as each pulse wave Δp). The amplitude is usually obtained by dividing the maximum value-minimum value or the maximum value-minimum value of the pulse wave Δp by 2 for each period.
[0039]
The blood pressure calculation means 21 is a means for obtaining one or more of the maximum blood pressure Ps, the minimum blood pressure Pd, and the average blood pressure Pa from the amplitude calculated by the pulse wave amplitude calculation means 19.
[0040]
That is, in the oscillometric method, the cuff pressure Po at the point (A in FIG. 2) where the amplitude of the pulse wave Δp suddenly increases during the pressure reduction or pressurization process of the cuff 11 is the maximum blood pressure Ps, and the amplitude of the pulse wave Δp is The cuff pressure Po at the point of sudden decrease (B in FIG. 2) is the minimum blood pressure Pd, and the cuff pressure Po at the point (C in FIG. 2) at which the amplitude of the pulse wave Δp is maximum is the average blood pressure Pa.
[0041]
Therefore, the blood pressure calculation means 21 calculates the maximum blood pressure Ps and the minimum blood pressure Pd by differentiating each amplitude of the pulse wave Δp and comparing the degree of increase / decrease with a prescribed value, etc. Then, the average blood pressure Pa is calculated.
[0042]
It should be noted that blood pressure determination methods and determination criteria vary from company to company, and whether it is implemented as a circuit using electronic components or a CPU program varies depending on the application. In addition, it is well known that blood pressure can be measured in the same manner as the pressurization process, not the pressure reduction process of the cuff 11. Therefore, it does not matter whether the cuff 11 is pressurized or depressurized when measuring the vascular elasticity of the present invention.
[0043]
In addition, the blood vessel elasticity measuring device 1 requires the maximum blood pressure Ps and the minimum blood pressure Pd obtained by the blood pressure calculating means 21 in order to obtain the blood vessel elasticity, but the embodiment of the blood pressure calculating means 21 is the oscilloscope described here. It is not limited to the metric method.
[0044]
Next, the measurement principle of vascular elasticity using the vascular elasticity measuring apparatus 1 of the present invention will be described. In the present invention, as will be described in detail later, a pulse wave detected during the decompression or pressurization process of the cuff 11 is used.
[0045]
That is, the pulse wave Δp detected by the pulse wave extracting means 17 can be used simultaneously for both blood pressure measurement and blood vessel elasticity measurement of the present invention. It can be shared with the vascular elasticity measuring device 1 of the invention. Therefore, it is not necessary to separately measure and store the pulse wave and other signals for blood pressure measurement and vascular elasticity measurement. Of course, the pressurization and depressurization control of the cuff 11 for detecting the pulse wave Δp may be performed only once, and the measurement time as a whole is almost the same as the time for measuring only the blood pressure with a conventional sphygmomanometer. Measurement can be performed.
[0046]
In the blood vessel, in order to circulate blood in the body, pressure is generated by periodically repeating the minimum blood pressure Pd and the maximum blood pressure Ps in synchronization with the heartbeat, and this pressure is called an intravascular pressure Pi. . That is blood pressure.
[0047]
When the cuff pressure Po, which is a pressure applied to the blood vessel wall from the outside, is set to be equal to or higher than the intravascular pressure Pi, the blood vessel is crushed and blood flow is prevented. When the cuff pressure Po is gradually lowered, the blood vessel expands due to the force of the intravascular pressure Pi that is intended to send blood into the blood vessel.
[0048]
Due to the expansion of the blood vessel, the blood vessel wall compresses the volume of the cuff 11 (synonymous with volume, hereinafter the same). The degree of compression of the volume of the cuff 11 varies depending on the relationship between the internal / external pressure difference ΔP (= cuff pressure Po−intravascular pressure Pi) and the degree of expansion of the blood vessel wall at that pressure, that is, the elastic characteristics of the blood vessel. For example, the blood vessel wall of a measurement subject with a hard blood vessel is poorly expandable, and vibration of the blood vessel wall does not sufficiently compress the cuff 11, but the blood vessel wall of the measurement subject with a soft blood vessel changes the volume of the cuff 11. Has enough flexibility to affect ΔV.
[0049]
Therefore, ΔP / ΔV (or ΔV / ΔP), which is a ratio between the internal / external pressure difference ΔP and the volume change ΔV of the cuff 11, is referred to as a blood vessel elastic modulus, which is generally used as an index of arteriosclerosis. In order to obtain the internal / external pressure difference ΔP and the volume change ΔV of the cuff 11, the following configuration is adopted in the present invention.
[0050]
That is, the vascular elasticity measuring device 1 in FIG. 1 includes a reference waveform storage unit 25, a ΔP calculation unit 27, a ΔV calculation unit 29, a comparison unit 31, and a display unit 23 in addition to the constituent units described in the blood pressure measurement principle. Yes. These additional means can be dealt with by adding and changing the electronic circuit of the blood pressure monitor of the pulse wave detection type, but can also be dealt with only by changing the program of the CPU. In that case, since the metal mold | die, board | substrate, etc. which are used with the conventional blood pressure meter can be used as it is except changing the display part of the display means 23, there exists a merit that the cost of a hardware surface does not start.
[0051]
When the cuff pressure control unit 13 sets the cuff pressure Po to a constant value equal to or lower than the minimum blood pressure Pd, the reference waveform storage unit 25 generates a waveform of a signal detected by the detection unit 110 for at least one cycle or two to three cycles. This means stores the waveform itself or a waveform obtained by averaging the stored waveforms as a reference waveform pi of the intravascular pressure Pi. This reference waveform pi is used by the ΔP calculating means 27 described later.
[0052]
Since the reference waveform pi is stored for only a short time before and after the pulse wave extraction means 17 detects the pulse wave Δp, the person to be measured does not need to be particularly aware that the blood vessel elasticity is being measured.
[0053]
FIG. 2 shows an example of the reference waveform pi of the intravascular pressure Pi detected by the detection means 110. Since one period may not be stable, it is desirable to store several periods and average them as shown in FIG. 2 if possible to improve measurement accuracy.
[0054]
The ΔP calculating means 27 is a means for calculating the internal / external pressure difference ΔP by the following procedure.
[0055]
A detailed configuration diagram of the ΔP calculating means 27 is shown in FIG. The ΔP calculation unit 27 includes an internal pressure value conversion unit 270, a repetitive waveform generation unit 271, and a calculation unit 272.
[0056]
The internal pressure value conversion means 270 converts the pressure value at each time point of the reference waveform pi stored in the reference waveform storage means 25 into the external pressure using the maximum blood pressure Ps and the minimum blood pressure Pd measured by the blood pressure calculation means 21. It is means for converting from a corresponding value to a value corresponding to the intravascular pressure Pi. Originally, as described above, the intravascular pressure Pi is a signal that periodically repeats the maximum blood pressure Ps and the minimum blood pressure Pd, whereas the pressure value of the reference waveform pi detected by the detection unit 110 is only This is because the pressure value in the cuff 11, that is, only the external pressure, not the intravascular pressure Pi.
[0057]
Specifically, as shown in the graph of FIG. 2, the systolic blood pressure Ps is applied to the maximum value ps of the reference waveform pi at the maximum peak point (pimax) of the reference waveform pi, and the minimum blood pressure Pd is set to the minimum peak point (pimin). Is applied to the minimum value pd of the reference waveform pi. Then, the pressure value at each time point of the reference waveform pi is converted into a pressure value corresponding to the intravascular pressure Pi using the relationship that the ratio of Ps-Pd and ps-pd is equal at any time point of the waveform.
[0058]
For example, the original reference waveform pi (t) detected by the detecting means 110 is
pi (t) = ((ps−pd) / 2) · sin (t) (1)
If the function Pi (t) is converted into a value corresponding to the intravascular pressure Pi,
Pi (t) = ((Ps−Pd) / (ps−pd)) · pi (t) (2)
It is represented by
[0059]
The repetitive waveform generating means 271 is means for continuously generating a reference waveform pi for one cycle whose value has been converted by the internal pressure value converting means 270 to obtain a pseudo intravascular pressure Pi. The reason why it is necessary to continuously generate is to compare the time series signal of the volume change ΔV of the cuff 11 with the comparison means 31 later.
[0060]
The calculating means 272 is a means for subtracting the cuff pressure Po obtained from the cuff pressure control means 13 and the intravascular pressure Pi generated by the repeated waveform generating means 271 to calculate the internal / external pressure difference ΔP = Po−Pi. 2 corresponds to the cuff pressure Po, and this cuff pressure Po can be known from the control contents of the cuff pressure control means 13.
[0061]
The ΔV calculating means 29 is a means for calculating the volume change ΔV of the cuff 11 from the signal detected by the detecting means 110 in the process of detecting the pulse wave Δp by the pulse wave extracting means 17 according to the following procedure.
[0062]
A detailed configuration diagram of the ΔV calculating means 29 is shown in FIG. The ΔV calculation unit 29 includes a time axis normalization unit 290, a calculation unit A291, a calculation unit B292, a cuff characteristic correction unit 293, a calculation unit C294, and a calculation unit D295.
[0063]
The time axis normalization means 290 is means for normalizing the time axis of the pulse wave Δp detected by the pulse wave extraction means 17 in accordance with the cycle of the intravascular pressure Pi, and compressing or expanding the waveform of the divided pulse wave Δp. This is because, later, the pulse wave Δp converted into the volume change ΔV of the cuff 11 is compared with the internal / external pressure difference ΔP (that is, Po−Pi) for each pulse wave Δp.
[0064]
Normally, the cycle of the pulse wave Δp is synchronized with the heartbeat and is at a constant interval, and therefore is substantially the same as the cycle of the intravascular pressure Pi. However, in the case of arrhythmia, the cycle is slightly different for each pulse wave Δp. Therefore, it is necessary to adjust the time axis to the cycle of the intravascular pressure Pi (reference waveform pi).
[0065]
Instead of matching the time axis of the pulse wave Δp with the time axis of the intravascular pressure Pi, conversely, the reference waveform pi is repeatedly generated by the waveform generating means 271 so as to match the time axis of the detected pulse wave Δp. However, it plays the same role as the time axis normalization means 290.
[0066]
The arithmetic means A291 is a means for adding the pulse wave Δp normalized by the time axis normalization means 290 and the cuff pressure Po. If the time axis is not normalized, the result obtained by the calculation means A291 is a signal detected by the detection means 110 in the process of detecting the pulse wave Δp, that is, Po + Δp itself. A291 can be omitted.
[0067]
The calculating means B292 is means for dividing Po + Δp, which is the result of the calculating means A291, and the cuff pressure Po.
[0068]
The cuff characteristic correcting unit 293 is a unit that converts the cuff pressure Po into a volume unit in consideration of the elastic characteristic of the cuff 11.
[0069]
In the first place, since the unit of the signal detected by the detecting means 110 is only a pressure unit, it is necessary to convert the volume change ΔV of the cuff 11 into a volume unit.
[0070]
Since the cuff 11 is made of an elastic material, the cuff pressure Po and the volume Vo of the cuff 11 have a relationship via the elastic coefficient of the cuff 11 as shown in the elastic characteristics of FIG. 5, and the cuff pressure is Po. The volume of the cuff 11 at the time is expressed by a function Vo (Po). In the present embodiment, this function is non-linear as shown in FIG. 5, but a linear approximation may be used as the elastic characteristic of the cuff 11 depending on the application and speeding up. The elastic characteristics of the cuff 11 are prepared in advance in the program of the blood vessel elasticity measuring device 1.
[0071]
The calculating means C294 is a means for dividing Vo (Po), which is the volume unit converted value of the cuff pressure Po calculated by the cuff characteristic correcting means 293, and (Po + Δp) / Po which is the result of the calculating means B292.
[0072]
In the present invention, the Boyle's law is established in a short period between the pressure in the cuff 11 (signal detected by the detecting means 110) that changes with the volume change of the cuff 11 and the volume of the cuff 11. It shall be. Assuming that the increase in the cuff pressure Po due to the increase ΔV from the volume Vo of the cuff 11 at a certain time is Δp,
Po · Vo = (Po + Δp) · (Vo−ΔV) (3)
Is established. Po + Δp is equal to a signal detected by the detecting means 110, that is, a signal in which the pulse wave Δp is superimposed on the cuff pressure Po.
[0073]
Furthermore, in Equation (3), if Vo is Vo (Po),
Po · Vo (Po) = (Po + Δp) · (Vo (Po) −ΔV) (4)
It becomes.
[0074]
Therefore, when the expression (4) is applied to the division result of the calculation means C294, the result of the calculation means C294 becomes Vo (Po) −ΔV.
[0075]
The calculating means D295 is a means for subtracting Vo (Po) and Vo (Po) −ΔV that is the result of the calculating means C294. The result is ΔV, that is, the volume change of the cuff 11 is obtained.
[0076]
Returning to the configuration diagram of FIG. 1, the comparison means 31 is a means for comparing the internal / external pressure difference ΔP calculated by the ΔP calculation means 27 with the volume change ΔV of the cuff 11 calculated by the ΔV calculation means 29. Thereby, the blood vessel elastic modulus which is the ratio of ΔP and ΔV can be obtained. Here, in the pulse wave detection process in the pulse wave extraction means 17, all pulse waves in the section from the point determined as the maximum blood pressure Ps to the point determined as the minimum blood pressure Pd are compared for each pulse wave Δp. To do.
[0077]
In the present embodiment, the reference waveform pi, the minimum blood pressure Pd, and the maximum blood pressure Ps are required to determine the internal / external pressure difference ΔP, and the pulse wave Δp is required to determine the volume change ΔV of the cuff 11. This is as described above. Therefore, for example, when the cuff 11 is controlled twice, the reference waveform pi, the minimum blood pressure Pd, and the maximum blood pressure Ps are measured during the first control, and the internal / external pressure difference ΔP is calculated for each cuff pressure Po. If the pulse wave Δp for measuring arteriosclerosis is detected at the second control, the volume change ΔV of the cuff 11 is sequentially calculated and compared by the comparison means 31 while detecting the pulse wave Δp at the second time. Therefore, it is not always necessary to store the signal by the entire waveform storage means 15. In this case, since the minimum blood pressure Pd and the maximum blood pressure Ps have already been measured for the first time, the cuff pressure 11 may be increased to the maximum blood pressure Ps of the measurement subject when the cuff 11 is controlled for the second time. The subject is not burdened.
[0078]
Furthermore, if the cuff 11 can be controlled a plurality of times, the reference waveform pi measured for a plurality of times is averaged, and a more accurate arteriosclerosis measurement can be performed.
[0079]
The display means 23 is a means for displaying vascular elasticity, that is, an index of arteriosclerosis, which is a comparison result of the comparison means 31. The comparison result can be expressed in a related diagram such as a two-dimensional graph of ΔP and ΔV, or the slope of ΔP and ΔV may be calculated and displayed, or the degree of arteriosclerosis may be ranked. The rank corresponding to the obtained numerical value may be displayed.
[0080]
[Example 1]
Next, specific embodiments of the present invention will be described in detail with reference to the configuration diagrams of FIGS. 1, 3, and 4 and the graph of FIG.
[0081]
The cuff 11 is wound around the upper arm or the lower limb of the person to be measured, and the cuff pressure control means 13 pressurizes the cuff 11 to a pressure that prevents the blood flow of the person to be measured (maximum blood pressure Ps or more). Thereafter, the cuff pressure Po is gradually decreased under the control of the cuff pressure control means 13.
[0082]
The all waveform storage means 15 stores the signal detected by the detection means 110 in the process of decreasing the cuff pressure Po. The pulse wave extracting means 17 sequentially detects the pulse wave Δp by subtracting the cuff pressure Po from this signal. Further, the pulse wave amplitude calculating means 19 calculates the amplitude of the detected pulse wave Δp.
[0083]
The blood pressure calculation means 21 determines the maximum blood pressure Ps and the minimum blood pressure Pd based on the calculated amplitude. Here, the average blood pressure Pa may also be calculated.
[0084]
When the cuff pressure Po reaches the minimum blood pressure Pd, the cuff pressure control means 13 does not end the control of the cuff pressure Po but maintains the cuff pressure Po at a constant pressure equal to or lower than the minimum blood pressure Pd. At this time, the signal detected by the detection means 110 is stored in the reference waveform storage means 25 as the reference waveform pi of the intravascular pressure Pi. However, since the reference waveform pi only needs to be stored for one period or two to three periods, the storage is short, and the measurement time is almost the same as when only blood pressure is measured. Further, the person to be measured is not particularly aware that the blood vessel elasticity is being measured.
[0085]
The ΔP calculating means 27 calculates the internal / external pressure difference ΔP using the measured maximum blood pressure Ps, the minimum blood pressure Pd, the reference waveform pi of the intravascular pressure Pi, and the cuff pressure Po known from the cuff pressure control means 13.
[0086]
The ΔV calculating unit 29 calculates the volume change ΔV of the cuff 11 using the detected pulse wave Δp, the cuff pressure Po, and the elastic characteristics of the cuff 11 stored in advance. Note that the calculation method of ΔP and ΔV is as described in the embodiment of the invention, and thus the description thereof is omitted.
[0087]
The comparison means 31 takes the internal / external pressure difference ΔP as the X-axis and the volume change ΔV of the cuff 11 as the Y-axis, and shows a related chart generally called a Lissajous figure, showing the total pulse wave from the maximum blood pressure Ps to the minimum blood pressure Pd. Record for the entire duration of the leg. Thereby, graphs as shown in FIGS. 6 and 7 are generated. FIG. 6 is a graph of a measurement subject whose blood vessels are hard, and FIG. 7 is a graph of a measurement subject whose blood vessels are soft.
[0088]
According to FIG. 6 and FIG. 7, the degree of arteriosclerosis can be easily evaluated since the X-axis internal / external pressure difference ΔP is near 0 and the slopes of the respective graphs are different. That is, in these figures, when the inclination is gentle, it is determined that the blood vessel is hard, and when the inclination is steep, it is determined that the blood vessel is soft.
[0089]
The inclination may be used as the blood vessel elasticity, and the numerical value may be displayed by the display means 23, or the degree of arteriosclerosis may be ranked and the rank corresponding to the obtained numerical value may be displayed. Further, if there is room in the display space, the Lissajous figure of FIGS. 6 and 7 may be displayed as it is.
[0090]
Furthermore, if the measured systolic blood pressure Ps, diastolic blood pressure Pd, and mean blood pressure Pa are also displayed simultaneously or alternately with the index of arteriosclerosis, the measurement subject can know various information at a time, Useful for diagnosis.
[0091]
Here, a method for reducing the storage capacity of the apparatus and displaying a higher-speed measurement result will be described below. For each of the reference waveform pi stored in the reference waveform storage means 25 and the pulse wave Δp detected by the pulse wave extraction means 17, the amplitude is calculated for each pulse wave Δp. In FIG. 4 and FIG. 4, ΔP and ΔV are calculated and compared.
[0092]
That is, since the comparison is not performed for the whole time for all the pulse wave sections but for the representative points for each pulse wave Δp, high-speed measurement is possible. The result is shown in FIG. In the graph of FIG. 8, an example in which the blood vessel is hard (Hard), normal (Normal), and soft (Soft) is shown in order from the top. From the inclination of the graph of FIG. 8, the difference between the case where the blood vessel is hard and the case where the blood vessel is soft is obvious at a glance, which is sufficient to know the degree of arteriosclerosis as a simple measurement result, and is measured at high speed.
[0093]
In addition to using the calculated amplitude as a representative point for each pulse wave Δp, a peak value (minimum value, maximum value) or a sample at an arbitrary point is extracted for each pulse wave Δp, and also from the reference waveform pi. Samples may be extracted at similar points, and the samples at each point may be compared. The number of samples to be extracted can be arbitrarily changed according to the application and the degree of speeding up. In addition, when extracting a plurality of samples, it is desirable that the time axis of the reference waveform pi or the pulse wave Δp is compressed / expanded by the time axis normalization means 290 in accordance with any time axis.
[0094]
[Example 2]
Next, an example in which Example 1 is further simplified and an index of arteriosclerosis is obtained will be described.
[0095]
FIG. 9 shows a configuration diagram of the vascular elasticity measuring device 5 of the present embodiment. The difference from FIG. 1 which is the configuration diagram of the first embodiment is that FIG. 9 does not include means relating to calculation of the internal / external pressure difference ΔP, that is, blood pressure calculation means 21, reference waveform storage means 25, and ΔP calculation means 27. is there.
[0096]
That is, in Example 1, the internal / external pressure difference ΔP is cuff pressure Po−intravascular pressure Pi, and the internal / external pressure difference ΔP is compared with the volume change ΔV of the cuff 11 to obtain an index of arteriosclerosis. The comparison means 51 can grasp the tendency of arteriosclerosis by comparing the cuff pressure Po itself with the volume change ΔV of the cuff 11.
[0097]
Normally, in the measurement process of blood pressure and vascular elasticity according to the present invention, the cuff pressure Po decreases with a substantially constant slope from the maximum blood pressure Ps to the minimum blood pressure Pd (or the minimum blood pressure Pd) under the control of the cuff pressure control means 13. To a maximum blood pressure Ps with a substantially constant slope). On the other hand, since the intravascular pressure Pi is a waveform that periodically repeats between the maximum blood pressure Ps and the minimum blood pressure Pd, the value of the internal / external pressure difference ΔP is a pulse wave Δp as in the Lissajous figures of FIGS. This cycle is not particularly necessary when it is desired to easily know the degree of arteriosclerosis.
[0098]
Even if the internal pressure Pi between the internal and external pressures Pi is approximated to the cuff pressure Po by ignoring the intravascular pressure Pi of the periodic waveform, which is the cause of this change, it has been determined that there is no problem in knowing the degree of arteriosclerosis. This is the present embodiment.
[0099]
Therefore, in this embodiment, it is only necessary to know the volume change ΔV and the cuff pressure Po of the cuff 11, it is not necessary to store the reference waveform pi necessary for calculating the internal / external pressure difference ΔP in the first embodiment, and the pulse wave Since it is not necessary to compare the Δp waveform with the reference waveform pi, it is not necessary to standardize the time axis.
[0100]
The calculation method of the volume change ΔV of the cuff 11 is the same as that obtained by deleting the time axis normalization means 290 from the detailed configuration diagram of FIG. 4 described in the first embodiment. The calculation method in each calculation unit and the correction method in the cuff characteristic correction unit 293 are the same as those described in the embodiment and Example 1 of the invention, and thus description thereof is omitted.
[0101]
The pulse wave amplitude calculating means 19 calculates the amplitude of each pulse wave Δp, the volume change ΔV of the cuff 11 calculated for each amplitude is taken on the vertical axis, and the cuff pressure Po at that time is taken on the horizontal axis. 10 graphs. Even from this graph, the difference in the tendency of arteriosclerosis is obvious from the difference in each inclination.
[0102]
In this embodiment, it is not necessary to memorize the reference waveform pi and calculate the systolic blood pressure Ps and the systolic blood pressure Pd. Therefore, in the blood pressure measurement process, the pulse wave Δp is detected almost in real time in real time. Graphs and numerical values can be displayed, and the display speed can be increased.
[0103]
In the vascular elasticity measuring device 5 of FIG. 9, the pulse wave amplitude calculating means 19 calculates the amplitude of each pulse wave Δp and obtains the volume change ΔV of the cuff corresponding to each, but in addition to the amplitude, Any point may be sampled. Furthermore, if there is a margin in the storage capacity, the subsequent calculation processing may be performed for the entire time of all the pulse waves.
[0104]
When the vascular elasticity measuring device 5 of FIG. 9 has the ΔP calculating means 27, the reference waveform pi that should be detected by the reference waveform storing means 25 is set as a fixed value, and the internal pressure value is converted by the minimum blood pressure Pd and the maximum blood pressure Ps. The internal / external pressure difference ΔP, which is the difference from the cuff pressure Po, may be calculated. This eliminates the need to store the reference waveform pi.
[0105]
Further, assuming that the elastic characteristic of the cuff 11 is linear (the cuff pressure Po and the volume Vo of the cuff 11 are in a proportional relationship), it is not necessary to convert the pressure value of each pulse wave Δp into the volume change ΔV of the cuff 11, Even if the amplitude of each pulse wave Δp or the value of an arbitrary point is compared with the cuff pressure Po at that time, a graph similar to FIG. 10 can be obtained. At this time, if the reference waveform pi, the minimum blood pressure Pd, and the maximum blood pressure Ps are measured, the internal / external pressure difference ΔP may be obtained and the pulse wave Δp and the internal / external pressure difference ΔP may be compared.
[0106]
Further, instead of the volume change ΔV of the cuff 11, a differential value that is a time change amount of the amplitude of the pulse wave Δp may be calculated and compared with the cuff pressure Po. This method is the simplest and suitable for obtaining an index of arteriosclerosis at high speed.
[0107]
【The invention's effect】
According to the present invention, an index of arteriosclerosis can be easily and easily obtained at high speed without attaching to the body of the subject other than the cuff necessary for measuring blood pressure.
[0108]
It is efficient because the blood vessel elasticity can be measured simultaneously with the blood pressure measurement by the pulse wave detection method. The subject can know both the blood pressure and the index of arteriosclerosis without being conscious of measuring the vascular elasticity, which is useful for comprehensive diagnosis. If a healthy person gets a habit of measuring blood pressure on a daily basis, it will lead to early detection and prevention of arteriosclerosis.
[0109]
It is possible to change the specifications to display the arteriosclerosis index only by changing the CPU program without changing the hardware configuration other than the display unit of the blood pressure monitor of the pulse wave detection method using the conventional cuff. As a result, development costs are reduced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an example of a blood vessel elasticity measuring apparatus according to the present invention.
FIG. 2 is a graph showing a cuff pressure Po, a waveform of a pulse wave Δp, and a reference waveform pi of an intravascular pressure Pi.
FIG. 3 is a block diagram showing an example of ΔP calculating means.
FIG. 4 is a configuration diagram showing an example of ΔV calculation means.
FIG. 5 is a graph showing cuff elastic characteristics.
FIG. 6 is an example of a graph showing blood vessel elasticity of a measurement subject with hard blood vessels.
FIG. 7 is an example of a graph showing blood vessel elasticity of a measurement subject whose blood vessels are soft.
FIG. 8 is another example of a graph showing vascular elasticity.
FIG. 9 is a configuration diagram showing another example of the vascular elasticity measuring device of the present invention.
FIG. 10 is another example of a graph showing vascular elasticity.
[Explanation of symbols]
1: Vascular elasticity measuring device
11: Cuff
110: Detection means
13: Cuff pressure control means
130: Pressurizing pump
131: Exhaust valve
15: All waveform storage means
17: Pulse wave extraction means
19: Pulse wave amplitude calculation means
21: Blood pressure calculation means
23: Display means
25: Reference waveform storage means
27: ΔP calculation means
270: Internal pressure value conversion means
271: Repetitive waveform generating means
272: Calculation means
29: ΔV calculation means
290: Time axis normalization means
291: Calculation means A
292: Calculation means B
293: Cuff characteristic correcting means
294: Calculation means C
295: Calculation means D
31: Comparison means
5: Vascular elasticity measuring device
51: Comparison means

Claims (5)

A cuff that compresses a part of the living body,
Cuff pressure control means for controlling the cuff pressure Po of the cuff;
Detecting means for detecting a pressure signal in the cuff;
A pulse wave extraction means for detecting a pulse wave Δp by subtracting the cuff pressure Po from a signal detected by the detection means in the process of pressure reduction or pressurization control of the cuff by the cuff pressure control means;
The cuff pressure Po is maintained at a predetermined pressure for at least one period or two to three periods before and after the pulse wave Δp is detected by the cuff pressure control means, and the waveform of the signal detected by the detection means at that time is used as a reference Reference waveform storage means for storing as waveform pi;
Blood pressure calculating means for calculating the minimum blood pressure Pd and the maximum blood pressure Ps;
ΔP calculation means for obtaining the internal / external pressure difference ΔP, which is the difference between the internal blood pressure Pi and the cuff pressure Po, by converting the reference waveform pi into units by the minimum blood pressure Pd and the maximum blood pressure Ps to obtain the internal blood pressure Pi;
In the process of detecting the pulse wave Δp, the signal detected by the detection means is obtained from the elastic characteristic function Vo / Po obtained from the cuff pressure Po and the volume Vo and the Boyle's law Po × V0 = (Po + ΔP) × (V0−ΔV) , ΔV calculation means for obtaining a volume change ΔV of the cuff by converting from a pressure unit to a volume unit;
By comparing the volume change ΔV of the cuff and the internal / external pressure difference ΔP for each detected pulse wave in the range of at least the maximum blood pressure Ps to the minimum blood pressure Pd, arteriosclerosis corresponding to vascular elasticity or vascular elasticity Comparison means for obtaining an index,
A blood vessel elasticity measuring device comprising: ΔP calculation means for obtaining the internal / external pressure difference ΔP, which is the difference between the intravascular pressure Pi and the cuff pressure Po, by converting the reference waveform pi into units by the minimum blood pressure Pd and the maximum blood pressure Ps to obtain the internal blood pressure Pi,
After the amplitude of the reference waveform pi stored in the reference waveform storage means is corrected by the minimum blood pressure Pd and the maximum blood pressure Ps, the internal / external pressure difference ΔP is calculated by a method using the intravascular pressure Pi that is continuously repeatedly generated. The vascular elasticity measuring device according to claim 1. The vascular elasticity obtained by the comparison means or the arteriosclerosis index corresponding to the vascular elasticity is shown in a related diagram such as a two-dimensional graph, the slope value of the relevant diagram, and the degree of arteriosclerosis corresponding to the slope value. Display means for displaying at least one of the ranks
The vascular elasticity measuring device according to claim 1, wherein the device has a vascular elasticity measuring device. The display means includes
Any combination of the vascular elasticity or the arteriosclerosis index corresponding to the vascular elasticity, the minimum blood pressure Pd, and the maximum blood pressure Ps is displayed simultaneously or alternately.
The vascular elasticity measuring device according to claim 3. The cuff, the cuff pressure control means, the detection means, and the pulse wave extraction means are:
Shared with sphygmomanometer with pulse wave detection method
The vascular elasticity measuring device according to any one of claims 1 to 4, wherein

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