JP2005021347A - Sphygmomanometer and method for measuring blood pressure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sphygmomanometer which measures blood pressure consecutively and noninvasively without causing discomfort to a patient or a subject. <P>SOLUTION: The sphygmomanometer is provided with: a thickness measuring part 11 for continuously measuring the thickness of a blood vessel wall by a noninvastive method; a thickness variation arithmetic part 12 for obtaining the variation of the thickness of a blood vessel wall from the measurement result of the thickness measuring part 11; and a blood pressure variation arithmetic part 13 for continuously obtaining the blood pressure variation of blood flowing through a blood vessel confined by the blood vessel wall from the thickness variation arithmetic part 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sphygmomanometer and a blood pressure measurement method.
[0002]
[Prior art]
The auscultation method (Korotkoff method) is the most well-known method for noninvasively measuring a person's blood pressure. According to this method, a pressure band (cuff) is attached to the upper arm, air is sent in to compress the blood vessel, and then the doctor and nurse gradually release the pressure band while the doctor and nurse hear the blood vessel sound. Check with (microphone). When the blood that has been stopped by the compression of the pressurization zone begins to flow intermittently along with the heartbeat, a characteristic sound called “Korotkoff sound” begins to be heard and then disappears. The blood pressure is obtained by reading the blood pressure values at the time of occurrence and disappearance of the “Korotkoff sound” from the pressure gauge as the maximum blood pressure value and the minimum blood pressure value, respectively.
[0003]
According to this method, there is an advantage that blood pressure can be easily measured because a device requiring a power source is not used. However, there are problems that measurement errors due to individual differences and experiences of the measurer are likely to occur, and depending on the surrounding noise, it is difficult to hear the Korotkoff sound.
[0004]
In order to solve these problems, an electronic sphygmomanometer has been developed and has been widely used in recent years. An electronic sphygmomanometer automatically executes a measurement procedure by an auscultation method, and air is sent to a pressurizing zone and air is released from the pressurizing zone mechanically. At this time, a pressure pulse wave that is a change in air pressure in the pressurization zone is measured, and a pressure when the pressure pulse wave suddenly increases and a pressure when the pressure pulse wave rapidly decreases are obtained as a maximum blood pressure and a minimum blood pressure, respectively. Such a detection method is called the OSIO geometric method.
[0005]
According to the electronic sphygmomanometer, it is possible to eliminate measurement errors due to individual differences and experience of the measurer, and it is possible to perform measurement regardless of ambient noise. Since it is easy to measure at regular intervals, it is possible to periodically measure the blood pressure of a patient during surgery or a patient who is being cared for by an ICU after surgery.
[0006]
However, since these conventional methods all use a pressure band, it takes a relatively long time to fill the pressure band with air and release the filled air. In general, it takes about several tens of seconds for one measurement. For this reason, these conventional methods are not suitable when it is necessary to know blood pressure in real time, such as surgery for a patient in a serious condition.
[0007]
In addition, the portion where the pressure band can be attached is limited to the upper arm or the like, and there is a possibility that the subject may feel uncomfortable by pressing the upper arm. The blood vessels of the arm with a pressure band may stop blood flow intermittently due to the pressure band, so pressurization is necessary when performing intravenous infusions for the purpose of administering drugs to patients during surgery. There also arises a problem that infusion cannot be performed on the arm wearing the belt.
[0008]
On the other hand, an ultrasonic diagnostic apparatus is conventionally used as a medical measurement apparatus that places little burden on a subject or a patient. By irradiating an ultrasonic wave from outside the body using an ultrasonic diagnostic apparatus, it is possible to obtain shape information, motion information, or quality information of the tissue in the body without causing pain to the subject.
[0009]
Using this feature, a blood pressure measurement method using ultrasonic waves has been proposed. For example, Patent Document 1 simultaneously measures the shape of at least two blood vessel cross-sections on an artery using ultrasonic waves, obtains blood flow velocity and pulse wave transmission velocity from the temporal change in cross-sectional area, and calculates blood pressure by calculation. Is disclosed.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-76233
[Patent Document 2]
Japanese Patent Laid-Open No. 10-5226
[Patent Document 3]
Japanese Utility Model Publication No. 6-9616
[0011]
[Problems to be solved by the invention]
According to the method described in Patent Document 1, it is necessary to simultaneously measure the cross-sectional shapes of at least two blood vessels on the artery using ultrasonic waves. For this reason, it is necessary to use at least two or more ultrasonic probes (or sensors).
[0012]
However, the ultrasonic waves transmitted from two or more ultrasonic probes are irradiated perpendicularly to the blood vessel, and the two ultrasonic probes are applied to the blood vessel so that the vertical cross section of the blood vessel can be measured accurately. It is generally difficult to fix. Further, since the number of probes is two or more, it is difficult to bring each probe into contact with the human body under optimum conditions. Since the number of probes increases, the cost of the apparatus also increases.
[0013]
An object of the present invention is to solve such a problem and to provide a blood pressure monitor and a blood pressure measurement method capable of measuring a blood pressure value in real time without causing discomfort to a patient or a subject.
[0014]
[Means for Solving the Problems]
A sphygmomanometer according to the present invention includes a thickness measuring unit that continuously measures the thickness of a blood vessel wall by a non-invasive method, and a thickness change that determines a thickness change amount of the blood vessel wall from the measurement result of the thickness measuring unit. A volume calculation unit; and a blood pressure change amount calculation unit that continuously obtains a blood pressure change amount of blood flowing through the blood vessel defined by the blood vessel wall from the thickness change amount calculation unit.
[0015]
In a preferred embodiment, the sphygmomanometer acquires a maximum blood pressure value, a minimum blood pressure value, or an average blood pressure value of the blood, and continuously calculates a blood pressure value based on the acquired value.
[0016]
In a preferred embodiment, the sphygmomanometer further includes a blood pressure measurement unit for obtaining a maximum blood pressure value, a minimum blood pressure value, or an average blood pressure value, and the blood pressure measurement unit causes the maximum blood pressure value, the minimum blood pressure value, or the average blood pressure value to be obtained. Get the value.
[0017]
In a preferred embodiment, the thickness measurement unit includes a transmission unit that drives an ultrasonic probe for transmitting an ultrasonic transmission wave to the measurement object including the blood vessel wall, and an ultrasonic reflection from the measurement object. A reception unit that receives a wave; a phase detection unit that detects a phase of the reflected ultrasonic wave; and a thickness calculation unit that determines a thickness of the blood vessel wall from the phase-detected signal.
[0018]
In a preferred embodiment, the blood pressure change amount calculation unit includes the thickness of the blood vessel wall obtained by the thickness measurement unit, the thickness change amount of the blood vessel wall obtained by the thickness change amount calculation unit, and A blood pressure change amount is obtained based on the elastic modulus of the blood vessel wall.
[0019]
The blood pressure measurement method of the present invention includes a step of continuously measuring the thickness of a blood vessel wall by a non-invasive method, a step of obtaining a change in thickness of the blood vessel wall from a measurement result of the thickness measurement unit, and the thickness A step of continuously obtaining a blood pressure change amount of the blood flowing through the blood vessel defined by the blood vessel wall from the thickness change amount calculation unit.
[0020]
In a preferred embodiment, the blood pressure measurement method acquires a maximum blood pressure value, a minimum blood pressure value, or an average blood pressure value of the blood, and continuously calculates a blood pressure value based on the acquired value.
[0021]
In a preferred embodiment, the step of measuring the thickness of the blood vessel includes a step of driving an ultrasonic probe for transmitting an ultrasonic wave to the measurement object including the blood vessel wall, and an ultrasonic wave from the measurement object. Receiving a reflected sound wave; phase detecting the reflected ultrasonic wave; and determining a thickness of the blood vessel wall from the phase-detected signal.
[0022]
In a preferred embodiment, the step of determining the blood pressure change amount is obtained based on the thickness of the blood vessel wall, the thickness change amount of the blood vessel wall, and the elastic modulus of the blood vessel wall.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The blood pressure is the pressure applied to the blood vessel wall by the blood flowing in the blood vessel, and generally refers to the blood pressure of the artery. The blood is pushed out to the blood vessels throughout the body by the pumping action of the heart. When the heart contracts, blood is pumped out into the blood vessel, and the pressure that the blood vessel receives from the blood is maximized. The blood pressure at this time is called the maximum blood pressure. Also, when the heart expands, the pressure that the blood vessels receive from the blood is minimal. The blood pressure at this time is called the minimum blood pressure.
[0024]
The upper part of FIG. 1 is a graph showing a temporal change in blood pressure, and the lower part is a graph showing a temporal change in thickness of the arterial vascular wall. The time axes of the two graphs correspond. As shown in FIG. 1, blood pressure increases when the heart contracts. At this time, since the blood vessel is expanded by receiving high pressure, the thickness of the blood vessel wall is reduced. When the heart expands, the blood pressure decreases and the pressure on the blood vessels decreases. For this reason, the thickness of the blood vessel wall increases. Assuming that the maximum value of the thickness of the blood vessel wall is hd, the amount of change in thickness is Δh (t), and the elastic modulus in the radial direction of the blood vessel wall is E, the blood pressure change amount Δp (t) is expressed by the following equation (1). Satisfy the relationship.
[0025]
Δp (t) = E · Δh (t) / hd (1)
[0026]
Accordingly, it is possible to obtain the blood pressure change amount in real time by continuously obtaining the change in the thickness of the blood vessel wall, and the sphygmomanometer of the present invention obtains the blood pressure change amount based on such a principle. .
[0027]
In the sphygmomanometer of the present invention, as means for continuously measuring the thickness of the blood vessel wall, a thickness measuring device using light such as a coherence visible or near infrared laser, ultrasonic waves, X-rays, electromagnetic waves, etc. A thickness measuring device using can be used. In particular, in order not to give pain or discomfort to the patient or subject, it is preferable to use a device that is non-invasive and can determine the thickness of the blood vessel wall without compressing the blood vessel. Moreover, it is preferable that the apparatus can measure the thickness of the blood vessel wall in real time with sufficient accuracy. Hereinafter, specific embodiments of the present invention will be described.
[0028]
(First embodiment)
FIG. 2 is a block diagram showing a first embodiment of the sphygmomanometer according to the present invention. The sphygmomanometer 51 includes a thickness measurement unit 11 that measures the thickness of the blood vessel wall, a thickness change amount calculation unit 12 that obtains a change in thickness of the blood vessel wall from the measurement result of the thickness measurement unit 11, and a thickness change. A blood pressure change amount calculation unit 13 that continuously obtains a blood pressure change amount of blood flowing through the blood vessel defined by the blood vessel wall from the calculation result of the amount calculation unit 12; Moreover, the microcomputer 14 which controls these each parts is also provided.
[0029]
In the present embodiment, the thickness measurement unit 11 uses an ultrasonic measurement device that measures the thickness of the blood vessel wall using ultrasonic waves. This ultrasonic measuring apparatus uses both the amplitude and phase of the detection signal by the method disclosed in Patent Document 2, determines the instantaneous position of the object by the constrained least square method, and performs highly accurate phase tracking. By doing so, the thickness of the blood vessel wall can be measured in real time and with sufficient accuracy.
[0030]
As shown in FIG. 2, the thickness measurement unit 11 includes an ultrasonic probe 15, an ultrasonic measurement control unit 16, and a thickness calculation unit 17. As the ultrasonic probe 15, for example, one used for an ultrasonic diagnostic apparatus can be adopted, and the size of the probe is 1 cm × 5 cm. The ultrasonic probe 15 has a plurality of ultrasonic transducers (ultrasonic transducer group) arranged in an array.
[0031]
FIG. 3 is a block diagram specifically showing the configuration of the thickness measuring unit 11. The ultrasonic measurement control unit 16 includes a transmission unit 18, a reception unit 19, a delay time control unit 20, a phase detection unit 21, and a filter 22. The transmission unit 18 gives a predetermined drive pulse signal to the ultrasonic probe 15. The ultrasonic transmission wave transmitted from the ultrasonic probe 15 by the drive pulse is reflected in the living body, and the generated ultrasonic reflected wave is received by the ultrasonic probe 15. The ultrasonic reflected wave received by the ultrasonic probe 15 is amplified by the receiving unit 19. The receiver 19 includes an A / D converter, and the ultrasonic reflected wave amplified in the receiver 19 is converted into a digital signal.
[0032]
The delay time control unit 20 is connected to the transmission unit 18 and the reception unit 19 and controls the delay time of the drive pulse signal given from the transmission unit 18 to the ultrasonic transducer group of the ultrasonic probe 15. Thereby, the direction of the acoustic line of the ultrasonic beam of the ultrasonic transmission wave transmitted from the ultrasonic probe 15 and the depth of focus are changed. Further, by controlling the delay time of the ultrasonic reflected wave signal received by the ultrasonic probe 15 and amplified by the receiving unit 19, the direction of the acoustic line of the received ultrasonic wave can be changed. The output of the delay time control unit 20 is input to the phase detection unit 21.
[0033]
The phase detector 21 performs phase detection on the received reflected wave signal that is delay-controlled by the delay time controller 20 and separates the received reflected wave signal into a real part signal and an imaginary part signal. The separated real part signal and imaginary part signal are input to the filter unit 22. The filter unit 22 removes reflection components other than tissue motion. The delay time control unit 20 and the phase detection unit 21 can be configured by software or hardware.
[0034]
The thickness calculator 17 includes an exercise speed calculator 23, a position calculator 24, and an interval calculator 25. Using the real part signal and the imaginary part signal of the phase-detected signal, the movement speed calculation unit 23 obtains the movement speed of the target biological tissue, and integrates the movement speed obtained by the position calculation unit 24 to obtain the biological tissue. Can be determined. The interval calculation unit 25 calculates a thickness (distance) by calculating a difference between two positions selected from the positions of the living tissue calculated by the position calculation unit 24. In the present invention, the thickness of the blood vessel wall is obtained by calculating the difference between the position of the inner surface and the outer surface of the blood vessel wall.
[0035]
As shown in FIG. 2, the thickness change amount calculation unit 12 sequentially receives the thickness of the blood vessel wall from the interval calculation unit 25, compares the thickness received immediately before with the current thickness, and calculates the thickness change amount. Ask. The blood pressure change amount calculation unit 13 performs the calculation shown in Expression (1) to obtain the blood change amount. Although not shown in FIG. 1, the blood change amount obtained by the blood pressure change amount calculation unit 13 is displayed as a graph or a numerical value on the image display device via a microcomputer or an appropriate interface. The thickness calculator 17, the thickness change calculator 12 and the blood pressure change calculator 13 can be configured by software or hardware.
[0036]
Next, the operation and usage of the sphygmomanometer 51 will be described. As shown in FIG. 2, the ultrasonic probe 15 is brought into contact with the body surface 1 of the living body 3 including the blood vessel (artery) to be measured. The sphygmomanometer 51 of the present invention can measure the blood pressure in any part of the human body. A gel or the like may be interposed between the ultrasonic probe 15 and the body surface 1 so that the ultrasonic wave efficiently propagates between the ultrasonic probe 15 and the living body 3. Further, the ultrasonic probe 15 may be fixed to a living body with a bandage.
[0037]
First, a plurality of drive pulse signals whose delay times are controlled by the delay time control unit 20 are output from the transmission unit 18, and the ultrasonic probe 15 converts each drive pulse signal into an ultrasonic transmission wave and transmits the ultrasonic wave. A wave is transmitted to the living body 3. The ultrasonic transmission wave propagates along the acoustic line 6 and across the arterial blood vessel 4 in the living body 3. The ultrasonic waves are reflected at each part of the living body 3 according to the propagation, but the ultrasonic waves are largely reflected at the boundary between the outer surface of the blood vessel 4 and the living body 3 and the boundary between the inner surface of the blood vessel 4 and the blood 7 flowing through the blood vessel 4. Such a boundary occurs in the blood vessel front wall 5 close to the body surface 1 side and the blood vessel rear wall 10 located on the inner side of the living body 3. The blood pressure can be measured by measuring any blood vessel wall. In the present embodiment, the reflected waves generated at the boundary 5 a between the outer surface of the blood vessel 4 and the living body 3 in the blood vessel front wall 5 and the boundary 5 b between the inner surface of the blood vessel 4 and the blood 7 flowing through the blood vessel 4 are measured.
[0038]
The ultrasonic reflected wave is received by the ultrasonic probe 15 and converted into an electric signal. The received reflected wave signal received by the receiver 19 is input to the phase detector 21 via the delay time controller 20. The delay time control unit 20 controls the delay time for each drive pulse signal using delay time data based on the deflection angle and focal depth of the acoustic lines of the ultrasonic transmission wave and the reception wave set in advance.
[0039]
The phase detector 21 performs phase detection on the received reflected wave signal and separates it into a real part signal and an imaginary part signal. From the real part signal and the imaginary part signal, a reflected wave component other than the motion speed of the tissue is removed by the filter 22 and is input to the thickness calculator 17.
[0040]
The motion speed calculator 23 of the thickness calculator 17 determines the motion speed of the boundary 5a and the boundary 5b based on the real part signal and the imaginary part signal of the received reflected wave signal subjected to phase detection. Specifically, when the reflected wave signal at time t of the boundary 5a is r (t), the amplitude of the reflected wave signal in the reflected wave signal r (t) and the reflected wave signal r (t + Δt) after a minute time Δt is Under the constraint that only the phase and the reflection position change without changing, the phase difference is obtained by the least square method so that the waveform matching error between the reflected wave signals r (t) and r (t + Δt) is minimized. . From this phase difference, the motion speed V (t) of the boundary 5a can be obtained. The reflected wave signal obtained from the boundary 5b is also processed by the same calculation to obtain the motion speed V ′ (t). The position calculation unit 24 integrates the movement speed obtained by the movement speed calculation unit 23 to obtain the positions P (t) and P ′ (t) of the boundary 5a and the boundary 5b. The space | interval calculating part 25 calculates | requires thickness T (t) by calculating | requiring these differences.
[0041]
The thickness change amount calculation unit 12 sequentially receives the thickness T (t) from the thickness calculation unit 17, and is a thickness that is a difference between the immediately previous thickness T (t−Δt) and the current thickness T (t). The amount of change Δh (t) is obtained.
[0042]
In obtaining the thickness change amount Δh (t), the maximum value hd of the thickness T (t) is obtained immediately after the start of measurement, and thereafter, in order to reduce the calculation load, the motion speeds V and V ′ Δh (t) may be obtained by integrating the difference ΔV.
[0043]
The blood pressure change amount calculation unit 13 obtains the blood pressure change amount according to the equation (1). For this purpose, the maximum value hd of the vascular wall thickness T (t) is received from the thickness calculator 17, and the blood pressure is changed by substituting the thickness variation Δh (t), hd and the elastic modulus E into the equation (1). A change amount Δp (t) is obtained. When the elastic modulus E of the patient or the subject under test whose blood pressure is being measured is known, the value may be used, and the average elastic modulus E of the human body at the site being measured may be used. Further, the elastic modulus E of a patient or a subject under blood pressure measurement may be obtained in real time using another device such as an ultrasonic diagnostic device, and the value may be used. When the elastic modulus E is updated in real time, an elastic modulus measuring device may be provided in the sphygmomanometer 51.
[0044]
The value that can be directly measured by the sphygmomanometer 51 of the present embodiment is the blood pressure change amount. For example, for a patient undergoing surgery, an ultrasonic probe 15 is attached to a body part that does not get in the way during surgery, such as the patient's upper arm, thigh, or neck, and the patient's blood pressure changes. Measure continuously with the sphygmomanometer 51. According to the sphygmomanometer 51 of the present embodiment, the blood pressure change amount can be measured twice per heart beat of the heart. That is, the blood pressure change can be known within about 1 second, and the blood pressure change can be measured in real time in a true sense. For this reason, if a patient's blood pressure change is monitored on the basis of the blood pressure before an operation, it can be immediately known that the patient's condition has suddenly changed due to a sudden change in blood pressure during the operation. As a result, it becomes possible to quickly detect a serious condition change and to quickly take appropriate measures against the condition change.
[0045]
In addition, since blood pressure changes are determined by noninvasively measuring the thickness of the blood vessel wall, it is not necessary to press the body with a pressure band, reducing physical discomfort and pain given to patients and subjects. Can do. The measurement of the thickness of the blood vessel wall is not limited to the place where the conventional pressure band is attached, and can be selected from various places where the thickness of the blood vessel wall of the artery can be measured.
[0046]
For this reason, for example, even if the arm is attached to a probe or the like, the blood vessel is not subjected to compression, and a catheter for administering a drug can be inserted into the arm.
[0047]
In the diagnosis based on the blood pressure change amount, the maximum value Δpmax (so-called “blood pressure range”) of the blood pressure change amount may be important. When it is desired to obtain the blood pressure change maximum value Δpmax, the thickness change amount calculation unit 12 obtains the maximum value Δhmax of the subject's thickness change during one heartbeat, and the blood pressure change amount calculation unit 13 obtains the following formula (2 ) To calculate the blood pressure change maximum value Δpmax.
[0048]
Δpmax = E · Δhmax / hd (2)
[0049]
It is known that the elastic modulus of the blood vessel wall has non-linearity due to the influence of viscosity, and changes with time as arteriosclerosis progresses. Therefore, when the blood pressure change amount or the maximum value of the blood pressure change amount is obtained using the relationship of the formula (1) or the formula (2), the more accurate blood pressure change amount is obtained by updating the elastic modulus used for the calculation in real time. be able to. However, one of the features obtained by the sphygmomanometer of the present invention is that changes in blood pressure can be measured in real time, and in applications where such features are emphasized, the immediacy of blood pressure changes is more accurate than accurate blood pressure values. is important. Therefore, the features of the present invention can be fully utilized without updating the elastic modulus in real time.
[0050]
(Second Embodiment)
FIG. 4 is a block diagram showing a second embodiment of the sphygmomanometer according to the present invention. The sphygmomanometer 52 is different from the first embodiment in that the sphygmomanometer 52 includes the systolic blood pressure measuring device 30 and the blood pressure calculating unit 31, and can measure the maximal blood pressure, the diastolic blood pressure, and the average blood pressure in real time. In FIG. 4, the same components as those in the first embodiment are denoted by the same reference numerals.
[0051]
In the sphygmomanometer 52, the blood pressure change amount calculation unit 13 performs the calculation shown in Expression (2) to obtain Δpmax that is the maximum value of the blood pressure change amount during one heartbeat. This value is sent to the blood calculation unit 31. In addition, the systolic blood pressure measuring device 30 determines the systolic blood pressure ps. As the systolic blood pressure measurement device 30, for example, the device shown in Document 3 can be used. This apparatus uses an ultrasonic probe and a piezoelectric sensor to obtain a maximum blood pressure value. The systolic blood pressure obtained from the systolic blood pressure measuring device 30 is sent to the blood pressure calculating unit 31.
[0052]
When the maximum blood pressure, the minimum blood pressure, and the average blood pressure are ps, pd, and pave, respectively, the following relationship holds between the maximum value Δpmax of the blood pressure change amount and these values.
[0053]
Δpmax = ps−pd
pave = (ps + 2pd) / 3 (3)
[0054]
Therefore, the minimum blood pressure pd and the average blood pressure pave can be obtained from the maximum blood pressure ps and the maximum value Δpmax of the blood pressure change amount by the following equation (4).
[0055]
pd = ps−Δpmax
pave = ps− (2/3) Δpmax (4)
[0056]
Thus, if the maximum value Δpmax and the maximum blood pressure ps of the blood pressure change amount are measured, the minimum blood pressure pd and the average blood pressure pave can be obtained.
[0057]
The blood pressure change amount calculation unit 13 continuously obtains the blood pressure change amount or the maximum value of the blood pressure change amount during the measurement for the patient or the subject. Once the minimum blood pressure and the average blood pressure are obtained, these values can be continuously obtained without using the maximum blood pressure by the maximum blood pressure measurement device 30 thereafter.
[0058]
Therefore, for example, the systolic blood pressure measuring device 30 and the blood pressure computing device 31 may not be electrically connected, and the measurer inputs the value of the systolic blood pressure measured using the systolic blood pressure measuring device to the sphygmomanometer 52. Thus, the maximum blood pressure, the minimum blood pressure, and the average blood pressure may be obtained.
[0059]
Further, as apparent from the equation (3), instead of using the systolic blood pressure measuring device 30, a diastolic blood pressure measuring device or an average blood pressure measuring device is used, and the minimum blood pressure value or the average blood pressure value and the maximum value of the blood pressure change amount are used. You may ask for maximum blood pressure.
[0060]
According to the present embodiment, in addition to the features described in the first embodiment, the blood pressure value can also be obtained in real time. For this reason, it becomes possible to grasp | ascertain the condition of the patient during an operation more correctly, for example.
[0061]
(First Experiment Example)
An experiment example in which the pressure change of water pulsating in the silicon tube is obtained using the sphygmomanometer 51 of the first embodiment will be described with reference to FIG.
[0062]
The silicone tube 41 is connected to the pulsation pump 43 by a pipe 42. The water 44 discharged from the pulsation pump 43 has a pulsation component, and the thickness of the wall of the silicone tube 41 varies depending on the strength of the pulsation. The silicone tube 41 is installed in a water tank 46 filled with water 45.
[0063]
The pressure change of the water in the silicone tube 41 is measured using a sphygmomanometer 51. The ultrasonic wave transmitted from the ultrasonic probe 15 of the sphygmomanometer 51 is strongly reflected at the boundary between the silicone tube 41 and the water 45 and the boundary between the silicone tube 41 and the water 44 and is received by the ultrasonic probe 15. The The obtained signal is transmitted to the main body of the sphygmomanometer 51. The sphygmomanometer 51 measures the wall thickness change amount of the silicone tube 41, and obtains the static pressure change amount Δp (t) based on the measurement result. The static pressure change amount Δp (t) is sent to the personal computer 49 for data processing. FIG. 6 is a graph showing the obtained Δp (t). In this experimental example, the driving frequency of the pulsating pump 43 is 3.1 Hz, the wall thickness of the silicone tube 31 at no load is 1.7 mm, and the elastic modulus of the silicone tube 31 is 2400 kPa.
[0064]
On the other hand, the pressure sensor 47 is installed in the silicon tube 41, and the static pressure in the silicone tube 41 is measured in real time by detecting the output of the pressure sensor 47 with the pressure measuring device 48. FIG. 7 is a graph showing the static pressure change amount Δp (t) measured by the pressure measuring device 41.
[0065]
As is apparent from FIGS. 6 and 7, the two graphs are in good agreement. From this, it can be seen that the amount of change in the static pressure in the silicone tube 31 can be obtained by determining the amount of change in the thickness of the wall of the silicone tube 31. In particular, although the period of pulsation is short (about 3 Hz), the timings indicating the maximum pressure and the minimum pressure are almost the same in the two graphs. This indicates that by using the sphygmomanometer 51, the blood pressure change amount can be obtained correctly in real time.
[0066]
(Second experiment example)
In this experimental example, the sphygmomanometer 51 was used, the posterior wall of the human carotid artery was used as the measurement target, the amount of change in the thickness of the vascular wall of the carotid artery was measured, and the maximum value of the change in blood pressure in the carotid artery was obtained.
[0067]
The test subject was a 35-year-old male, the maximum value hd of the carotid artery thickness of the test subject was 2.5 mm, and the maximum thickness change amount Δhmax was 39 μm. When 500 kPa was used as the radial elastic modulus E of the blood vessel wall, the blood pressure change maximum value Δpmax was calculated to be 7.8 kPa (58 mmHg).
[0068]
Simultaneously with the measurement by the sphygmomanometer 51, the blood pressure of the upper arm was measured using a cuff sphygmomanometer. According to the measurement results, the maximum blood pressure was 131 mmHg, the minimum blood pressure was 77 mmHg, and the maximum value Δpmax of the blood pressure change amount was 54 mmHg, that is, 7.2 kPa. In general, it is known that a measurement error of several mmHg may occur in measurement with a cuff type sphygmomanometer. Therefore, the sphygmomanometer of the present invention has a measurement error equal to or higher than that of a conventional cuff sphygmomanometer. I can say that.
[0069]
【The invention's effect】
According to the sphygmomanometer and the blood pressure measurement method of the present invention, blood pressure can be continuously and non-invasively measured without causing discomfort to the patient or subject.
[Brief description of the drawings]
FIG. 1 is a graph showing temporal changes in blood pressure of blood flowing through a blood vessel and a change in thickness of a blood vessel wall.
FIG. 2 is a block diagram showing a first embodiment of a sphygmomanometer according to the present invention.
3 is a block diagram showing a configuration of a thickness measuring unit of the sphygmomanometer shown in FIG. 2. FIG.
FIG. 4 is a block diagram showing a second embodiment of a sphygmomanometer according to the present invention.
5 is a block diagram illustrating an experimental example for measuring the pressure of a liquid in a pulsating silicon tube using the sphygmomanometer shown in FIG. 2. FIG.
6 is a graph showing the amount of pressure change measured by a sphygmomanometer in the experimental example shown in FIG.
7 is a graph showing a pressure change amount measured by a pressure measuring device in the experimental example shown in FIG.
[Explanation of symbols]
1 body surface
3 living body
4 Blood vessels
5 blood vessel front wall
6 acoustic lines
7 Blood
10 Blood vessel rear wall
11 Thickness measurement section
12 Thickness change calculation unit
13 Blood pressure change calculation unit
14 Microcomputer
15 Ultrasonic probe
16 Ultrasonic measurement controller
17 Thickness calculator
18 Transmitter
19 Receiver
20 Delay time controller
21 Phase detector
22 Filter section
23 Motion speed calculator
24 Position calculator
25 Interval calculation unit
30 systolic blood pressure measuring device
41 Silicone tube
42 Piping
43 Pulsating pump
44 water
45 water
46 Aquarium
47 Pressure sensor
48 Pressure measuring device
49 PC
51, 52 Blood pressure monitor

Claims (9)

A thickness measurement unit that continuously measures the thickness of the blood vessel wall by a non-invasive method;
A thickness change amount calculating unit for determining a thickness change amount of the blood vessel wall from the measurement result of the thickness measuring unit;
A blood pressure change amount calculating unit that continuously obtains a blood pressure change amount of blood flowing through a blood vessel defined by the blood vessel wall from the thickness change amount calculating unit;
Sphygmomanometer equipped with. The sphygmomanometer according to claim 1, wherein a maximum blood pressure value, a minimum blood pressure value, or an average blood pressure value of the blood is acquired, and the blood pressure value is continuously obtained based on the acquired value. The blood pressure according to claim 2, further comprising a blood pressure measurement unit that obtains a maximum blood pressure value, a minimum blood pressure value, or an average blood pressure value, and the blood pressure measurement unit acquires the maximum blood pressure value, the minimum blood pressure value, or the average blood pressure value. Total. The thickness measuring unit is
A transmitter for driving an ultrasonic probe for transmitting an ultrasonic transmission wave to a measurement object including the blood vessel wall;
A receiver for receiving an ultrasonic wave reflected from the measurement object;
A phase detector for detecting the phase of the reflected ultrasonic wave;
The sphygmomanometer according to any one of claims 1 to 3, further comprising: a thickness calculator that obtains a thickness of the blood vessel wall from the phase-detected signal. The blood pressure change amount calculation unit calculates the thickness of the blood vessel wall obtained by the thickness measurement unit, the thickness change amount of the blood vessel wall obtained by the thickness change amount calculation unit, and the elastic modulus of the blood vessel wall. The sphygmomanometer according to claim 1, wherein the blood pressure change amount is obtained based on the blood pressure change amount. Continuously measuring the thickness of the vessel wall by a non-invasive method;
Obtaining a change in thickness of the blood vessel wall from the measurement result of the thickness measurement unit;
Continuously obtaining a blood pressure change amount of blood flowing through a blood vessel defined by the blood vessel wall from the thickness change amount calculating unit;
Blood pressure measurement method. The blood pressure measurement method according to claim 6, wherein a maximum blood pressure value, a minimum blood pressure value, or an average blood pressure value of the blood is acquired, and the blood pressure value is continuously obtained based on the acquired value. Measuring the thickness of the blood vessel comprises:
Driving an ultrasonic probe for transmitting an ultrasonic transmission wave to a measurement object including the blood vessel wall;
Receiving an ultrasonic reflected wave from the measurement object;
Phase detecting the ultrasonic reflected wave; and
Determining the thickness of the vessel wall from the phase detected signal;
The blood pressure measurement method according to claim 6 or 7, comprising: The blood pressure measurement method according to any one of claims 6 to 8, wherein the step of obtaining the blood pressure change amount is obtained based on a thickness of the blood vessel wall, a thickness change amount of the blood vessel wall, and an elastic modulus of the blood vessel wall. .

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