JP2021023615A - Pulse pressure estimation device, pulse pressure estimation system, pulse pressure estimation method, and control program - Google Patents

Abstract

To estimate pulse pressure of a living body in a non-contact manner with a simple configuration.SOLUTION: A pulse pressure estimation device comprises: a heartbeat signal extraction unit (11) that from a radio wave reflected by a body surface of a living body, extracts a heartbeat signal (S) having a period (ppi) resulting from heartbeat of the living body, a systolic peak (P1) indicating systolic blood pressure of a heart of the living body, and a reflection wave peak (P2) caused by a blood flow driven by systole of the heart being reflected by a blood vessel; and a pulse pressure estimation unit (16) that estimates pulse pressure (ΔP) of the living body on the basis of a pulse wave propagation time (ti-t'i) from the systolic peak (P1) to the reflection wave peak (P2), the period (ppi) of the heartbeat signal (S), and amplitude (ai) of the heartbeat signal (S).SELECTED DRAWING: Figure 1

Description

The present invention relates to a pulse pressure estimation device, a pulse pressure estimation system, a pulse pressure estimation method, and a control program for estimating a pulse pressure of a living body without contacting the living body.

The pulse wave velocity (PWV) and the amount of change in blood vessel diameter in the living body are calculated from the heartbeat signal based on the radio wave reflected by the body surface of the living body, and the square of the pulse wave velocity is multiplied by the amount of change in the blood vessel diameter. A pulse pressure estimation device for estimating the pulse pressure of the living body by multiplying by is known as a prior art (Patent Document 1).

This pulse pressure estimation device calculates the pulse wave velocity between the measurement positions based on the heartbeat signals measured at a plurality of different positions of the living body.

Japanese Unexamined Patent Publication No. 2016-150065 (published on August 22, 2016)

However, in the prior art as described above, it is necessary to acquire the heartbeat signals measured at a plurality of different positions in the living body in order to calculate the pulse wave velocity. Therefore, it becomes necessary to provide a plurality of non-contact sensors, and there is a problem that the configuration becomes complicated.

One aspect of the present invention is to realize a pulse pressure estimation device, a pulse pressure estimation system, a pulse pressure estimation method, and a control program capable of estimating the pulse pressure of a living body in a non-contact manner with a simple configuration. To do.

In order to solve the above problems, the pulse pressure estimation device according to one aspect of the present invention uses the radio waves reflected by the body surface of the living body to obtain the cycle caused by the heartbeat of the living body and the systole of the heart of the living body. Extraction of a heartbeat signal having a systolic peak indicating blood pressure and a reflected wave peak indicating the hardness of blood vessels based on the reflected waves generated by the contraction of the heart and the blood flow ejected by the blood vessels. A unit, an estimation unit that estimates the pulse pressure of the living body based on the pulse wave propagation time from the systolic peak to the reflected wave peak, the period of the heartbeat signal, and the amplitude of the heartbeat signal. It is characterized by being prepared.

According to this feature, a single heartbeat signal is used because the pulse pressure of the living body is estimated based on the pulse wave propagation time from the systolic peak to the reflected wave peak, the heartbeat signal cycle, and the heartbeat signal amplitude. The pulse pressure of the living body can be estimated based only on. Therefore, with a simple configuration, the pulse pressure of the living body can be estimated without contact.

In the pulse pressure estimation device according to one aspect of the present invention, the estimation unit represents t1i: the time when the systolic peak occurs, t2i: the time when the reflected wave peak occurs, and ppi: the time for one heartbeat. Let the cycle of the heartbeat signal, ai: the amplitude of the heartbeat signal representing the change in blood flow accompanying the change in the cardiac output of the living body, and dp: the pulse pressure of the living body.

It is preferable to estimate the pulse pressure of the living body based on the above.

With this configuration, the pulse pressure of the living body is estimated based on the multiplication result of the square of the ratio of the pulse wave propagation time from the systolic peak to the reflected wave peak and the period of the heartbeat signal and the amplitude of the heartbeat signal. The pulse pressure of a living body can be estimated based on only a single heartbeat signal.

In the pulse pressure estimation device according to one aspect of the present invention, it is preferable that the estimation unit estimates the pulse pressure of the living body for each cycle of the heartbeat signal.

With this configuration, it can be suitably applied to applications such as continuous monitoring of the pulse pressure value of the measurement target person.

In the pulse pressure estimation device according to one aspect of the present invention, it is preferable that the radio wave is a microwave.

With this configuration, since the reflected wave reflected by the living body also contains information on the extensibility and rigidity of the blood vessel, the pulse pressure of the living body can be estimated by the microwave in a non-contact manner.

In order to solve the above problems, the pulse pressure estimation system according to one aspect of the present invention includes a non-contact sensor that detects radio waves reflected by the body surface of a living body and a pulse pressure estimation device according to one aspect of the present invention. The extraction unit of the pulse pressure estimation device extracts the heartbeat signal from the radio wave detected by the non-contact sensor.

According to this feature, a single heartbeat signal is used because the pulse pressure of the living body is estimated based on the pulse wave propagation time from the systolic peak to the reflected wave peak, the heartbeat signal cycle, and the heartbeat signal amplitude. The pulse pressure of the living body can be estimated based only on. Therefore, with a simple configuration, the pulse pressure of the living body can be estimated without contact.

In the pulse pressure estimation system according to one aspect of the present invention, it is preferable to further include an irradiation device that irradiates the radio wave toward the body surface of the living body.

With this configuration, radio waves can be reflected by the body surface of a living body.

In the pulse pressure estimation system according to one aspect of the present invention, it is preferable that the non-contact sensor and the irradiation device are integrally configured.

With this configuration, since the non-contact sensor and the irradiation device are integrated, the configuration of the pulse pressure estimation system becomes even simpler.

In order to solve the above problems, the pulse pressure estimation method according to one aspect of the present invention is based on the radio waves reflected by the body surface of the living body, the cycle caused by the heartbeat of the living body and the systole of the heart of the living body. Extraction of a heartbeat signal having a systolic peak indicating blood pressure and a reflected wave peak indicating the hardness of blood vessels based on the reflected waves generated by the contraction of the heart and the blood flow ejected by the blood vessels. Includes a step and an estimation step of estimating the pulse pressure of the living body based on the pulse wave propagation time from the systolic peak to the reflected wave peak, the period of the heartbeat signal, and the amplitude of the heartbeat signal. It is characterized by doing.

The pulse pressure estimation method according to one aspect of the present invention further includes a detection step of detecting radio waves reflected by the body surface of the living body, and the extraction step includes the heartbeat signal from the radio waves detected by the detection step. It is preferable to extract.

In order to solve the above problems, the control program according to one aspect of the present invention is a control program for operating a computer as a pulse pressure estimation device according to one aspect of the present invention, and is the extraction unit and the estimation. Make the computer function as a department.

According to one aspect of the present invention, the pulse pressure of a living body can be estimated in a non-contact manner with a simple configuration.

It is a waveform diagram which shows the time-dependent change of a human blood pressure value schematically. It is a figure explaining the mode of measuring the pulse pressure using the pulse pressure estimation system which concerns on one Embodiment of this invention. It is a block diagram which shows an example of the schematic structure of the said pulse pressure estimation system. It is a figure which shows the example of the position of the body surface of a living body which is irradiated with radio waves by the said pulse pressure estimation system. It is a waveform diagram which shows an example of the waveform data of the heartbeat signal extracted from the said radio wave by the said pulse pressure estimation system. It is a figure which shows the parameter about the formula of Bramwell-Hill. It is a waveform diagram which shows an example of the waveform data of the heartbeat signal used by the said pulse pressure estimation system for estimation of a pulse pressure. It is a flowchart which shows an example of the pulse pressure estimation process executed by the said pulse pressure estimation system. It is a flowchart which shows an example of the parameter calculation process in the said pulse pressure estimation process. It is a waveform diagram which shows the correlation between the pulse pressure of a living body estimated by the said pulse pressure estimation system, and the pulse pressure of a living body measured by a continuous sphygmomanometer.

Hereinafter, one embodiment of the present invention will be described in detail. In the following description, an example in which the target of pulse pressure measurement is a human will be described, but it is also possible to target an animal (living body) other than a human.

(Relationship between blood pressure and pulse pressure)
As a general blood pressure measurement method, a direct method and an indirect method are known. The direct method, also called an open method, is a method of directly and continuously measuring the internal pressure of a subject's arteries. Specifically, a catheter is introduced into the blood vessel of the subject, and a small amount of antiplatelet coagulant (heparin, etc.) for suppressing blood coagulation is injected into the blood vessel, and a part of blood is injected into the catheter from inside the blood vessel. It is a method of leading to blood pressure measurement. This direct method is used for blood pressure monitoring during surgery because the measured blood pressure value is highly reliable. However, it is not a blood pressure measurement method that can be easily performed at other than medical institutions (for example, at home), and it is necessary to pay attention to hygiene when implementing this method, which may cause complications. The analysis is also complicated.

On the other hand, the indirect method is also called a non-invasive method, and there are a method of measuring the blood pressure of a subject discontinuously and a method of measuring the blood pressure continuously. Non-continuous measurement methods include auscultation (Korotkoff), vibration (oscilometric), and ultrasonic Doppler methods, and continuous measurement methods include tonometer (tonometry) and volume. Compensation method can be mentioned. This indirect method is basically an active method in which an external force is applied by contacting the subject's body during measurement.

That is, the indirect method is based on the idea that the pressure applied when the blood flow that was stopped at the time of decompression reappears corresponds to the blood pressure. For this reason, the indirect method includes a step of pressurizing the blood vessels of the subject to create a state in which blood flow is stopped, and then gradually reducing the pressure until blood flow occurs. Cuffs and manchettes are known as devices that apply pressure to a part of the subject's body. The indirect method is used for sphygmomanometers that automatically measure blood pressure, and sphygmomanometers that use the indirect method are easy and do not require medical expertise, and are easy to use for health examinations and daily health at home. Widely used for management and other purposes.

Here, the relationship between blood pressure and pulse pressure will be briefly described with reference to FIG. FIG. 1 is a waveform diagram schematically showing changes over time in human blood pressure values. Blood pressure is caused by the beating of the heart and rises during systole and falls during diastole. Therefore, the change with time of the blood pressure value becomes a periodic change as shown in the figure.

In this waveform, referred to as the maximum value of the blood pressure in one cycle systolic blood pressure (maximum blood pressure), in FIG. 3, is indicated as P _h. On the other hand, it is referred to as diastolic blood pressure the minimum value of blood pressure in one cycle (minimum blood pressure), in FIG. 3, is indicated as P _l. In addition, the pulse pressure ΔP is
ΔP ₌ P h -P _l
Is calculated as. Pulse pressure ΔP is used as an index of arteriosclerosis occurring in large blood vessels.

Here, blood pressure is sensitive to changes in the subject's emotions, as is known as a phenomenon called "white coat hypertension," in which blood pressure shows an abnormal value in front of a nurse or doctor at a hospital or health center. Change. Therefore, when measuring the blood pressure of a subject, it is ideally considered that the subject is unaware that the blood pressure is being measured.

However, a subject who undergoes blood pressure measurement by the indirect method has a cuff or a manchette attached to a part of the body such as a fingertip or an upper arm, pressurizes the part of the body, and operates during blood pressure measurement. You will hear the sounds produced by the pump and servomotor. In addition, congestion may occur in the area compressed by the cuff pressure, which imposes a burden on hypertensive patients and the elderly. Furthermore, it may be difficult to attach the cuff depending on the skin condition of the subject. Therefore, the above-mentioned indirect method cannot be said to be an ideal blood pressure measurement method because the blood pressure cannot be measured without causing the subject to feel stress.

The present embodiment provides a pulse pressure estimation system 100 capable of estimating the pulse pressure of a subject with a simple configuration without causing the subject to feel stress.

(Pulse pressure estimation method using the pulse pressure estimation system 100)
FIG. 2 is a diagram illustrating a state of measuring pulse pressure using the pulse pressure estimation system 100 according to the embodiment of the present invention. The pulse pressure estimation system 100 includes a single microwave sensor 3 (non-contact sensor) and a pulse pressure estimation device 10.

In the pulse pressure estimation system 100, the measurement target person is irradiated with microwaves from the microwave sensor 3. Then, the microwave sensor 3 receives the sensor signal including the reflected wave reflected by the microwave emitted by itself on the body surface of the measurement target person and outputs the sensor signal to the pulse pressure estimation device 10. After that, the pulse pressure estimation device 10 estimates the pulse pressure of the measurement target person by analyzing the sensor signal output from the microwave sensor 3.

In this way, the pulse pressure estimation system 100 estimates the pulse pressure using the sensor signal obtained by irradiation with microwaves. The microwave is not visible, passes through the mattress, the clothes of the measurement target, etc., and the sensor signal can be obtained even if it is irradiated from a position some distance from the measurement target. The microwave sensor 3 can be arranged below the mattress as described above.

This makes it possible to measure the pulse pressure of the person to be measured lying on the mattress, without being aware that the person to be measured is measuring the pulse pressure (during microwave irradiation). Therefore, the pulse pressure can be estimated without giving stress to the person to be measured. Further, since the pulse pressure can be continuously estimated, it can be used, for example, for monitoring the pulse pressure fluctuation during sleep of the measurement target person. The posture of the person to be measured is not limited to this. For example, the person to be measured may be sitting on a chair or the like, or may be standing.

(Configuration example of pulse pressure estimation system 100)
Subsequently, a more detailed configuration of the pulse pressure estimation system 100 will be described with reference to FIG. FIG. 3 is a block diagram showing an example of a schematic configuration of the pulse pressure estimation system 100. As shown in FIG. 2, the pulse pressure estimation system 100 includes a microwave sensor 3, a display device 5, and a pulse pressure estimation device 10.

The microwave sensor 3 is a microwave radar that emits microwaves and detects a sensor signal including a reflected wave reflected by a measurement target person. The sensor signal detected by the microwave sensor 3 is sent to the pulse pressure estimation device 10 by wireless or wire communication. The output waveform is not particularly limited, and for example, a continuous wave (CW) radar, an FMCW radar, a pulse radar, or a Doppler radar can be applied as the microwave sensor 3. Further, the wavelength is not particularly limited, and an electromagnetic wave in a frequency band corresponding to a microwave having a wavelength of 0.1 mm to 1 m can be applied. Further, the output of the microwave is not particularly limited, and a microwave of any output may be used. However, considering the effect on the body of the person to be measured, it is desirable to set an upper limit value according to the frequency and output the output below the upper limit value. For example, when using a microwave having a frequency of 10 GHz or more, it is preferable to use a microwave having a frequency of 10 mW or less.

The microwave sensor 3 may irradiate the trunk of the measurement target with microwaves and receive the sensor signal from the trunk, or may emit the microwave toward the peripheral portion of the measurement target. It may be irradiated and receive a sensor signal from the peripheral portion. In this way, a single microwave sensor 3 is provided in the pulse pressure estimation system 100.

Examples of the trunk include the back or the periphery of the thorax, and examples of the peripheral portion include limbs (arms, hands, feet, legs). For example, as in the example of FIG. 2, when the measurement target person is lying on the mattress on his / her back, the microwave sensor 3 may be placed directly under the back, or the legs or arms. The microwave sensor 3 may be arranged directly under the.

The display device 5 displays the pulse pressure calculated by the pulse pressure estimation system 100. A touch panel may be laminated on the display surface of the display device 5.

(Configuration example of pulse pressure estimation device 10)
Next, the configuration of the pulse pressure estimation device 10 will be described. As shown in FIG. 3, the pulse pressure estimation device 10 includes a control unit 1 that controls the pulse pressure estimation device 10 in an integrated manner and a storage unit 2 that stores various data used in the pulse pressure estimation device 10. I have. The control unit 1 includes a heartbeat signal extraction unit 11, a blood flow change amount calculation unit 12, a pulse wave propagation time calculation unit 13, and a pulse pressure estimation unit 16.

FIG. 4 is a diagram showing an example of the position of the body surface of a living body to which radio waves are irradiated by the pulse pressure estimation system 100. The microwave sensor 3 receives the radio wave reflected by the portion (radial crest) indicated by the arrow A in FIG.

FIG. 5 is a waveform diagram showing an example of waveform data of the heartbeat signal S extracted from the radio wave.

The heartbeat signal extraction unit 11 extracts the heartbeat signal S shown in FIG. 5 from the sensor signal received from the microwave sensor 3. For example, by performing a filter process such as a bandpass that extracts a frequency of about 0.8 Hz to 3 Hz, which is characteristic of the heartbeat, contained in the sensor signal, the heartbeat signal S having a waveform correlated with the heartbeat is extracted from the sensor signal. It is possible to do. The heartbeat signal S is a signal including a waveform corresponding to a cycle caused by the heartbeat of the person to be measured. The method for extracting the heartbeat signal S is not limited to the filter processing, and any method may be used. Further, the voltage value of the heartbeat signal may be amplified by, for example, a DC amplifier or the like so that the pulse pressure estimation described later can be facilitated.

Blood heartbeat signal extraction unit 11 heartbeat signal S extracted by the that the period pp _i caused by the biological heart, the systolic peak P1 showing a systolic blood pressure of the living heart, a heart was ejected by contracting It has a reflected wave peak P2 indicating the hardness of the blood vessel based on the reflected wave generated by the flow being reflected by the blood vessel. The change in the generation time of the reflected wave peak P2 indicates the change in the hardness of the blood vessel.

_{The blood flow change amount calculation unit 12 calculates the amplitude ai} of the heartbeat signal S representing the blood flow change amount based on the heartbeat signal S.

Pulse transit time calculation unit 13, based on the heartbeat signal S, calculates the pulse wave propagation time until the reflected wave peak P2 a _{(t i -t'} i) from systolic peak P1.

Pulse pressure estimating unit 16, the pulse wave propagation time from the systolic peak P1 to the reflected wave peak P2 and _{(t i -t'} i), and the period pp _i of the heartbeat signal S, into an amplitude _{a i} of the heartbeat signal S Based on this, the pulse pressure ΔP of the living body is estimated. The details of this estimation method will be described later. The pulse pressure ΔP estimated by the pulse pressure estimation unit 16 has a correlation with the actual pulse pressure and can be used for the same purpose as the pulse pressure value measured by the conventional method. However, this estimated pulse pressure ΔP is an index for grasping the relative fluctuation of the pulse pressure, and is basically the same as the pulse pressure value measured by the conventional method unless processing such as calibration is performed. The unit (mmHg) does not have the same value.

As described above, the pulse pressure estimation system 100 irradiates the measurement target person with microwaves from the microwave sensor 3 and detects the sensor signal which is the reflected microwaves. Then, the pulse pressure estimation device 10 extracts the heartbeat signal S from the sensor signal, and estimates the pulse pressure ΔP based on the extracted heartbeat signal S. As a result, according to the pulse pressure estimation system 100, the pulse pressure ΔP can be estimated without contacting the measurement target person or even being noticed by the measurement target person. Therefore, the pulse pressure ΔP can be estimated without exerting mental and physical stress on the measurement subject.

As described with reference to FIG. 1, the pulse pressure ΔP is biological data that correlates with the blood pressure, and when the blood pressure increases or decreases, the pulse pressure ΔP also increases or decreases. Therefore, for example, in clinical practice, the pulse pressure ΔP estimated by the pulse pressure estimation device 10 is used for the same purpose as the blood pressure value measured by a conventional sphygmomanometer (administration of a pressor agent when the pulse pressure value decreases, etc.). can do.

(About the Bramwell-Hill equation)
As a mathematical formula related to the pulse pressure ΔP, the Bramwell-Hill equation shown in the following (Equation 1) is known. In the following (Equation 1), ΔP is the pulse pressure, ρ is the blood density, PWV is the pulse wave velocity (Pulse Wave Velocity), D is the inner diameter of the artery, and ΔD is the amount of change thereof.

Here, the parameters related to the above mathematical formula will be described with reference to FIG. FIG. 6 is a diagram showing parameters related to the Bramwell-Hill equation. As shown in the figure, minute changes occur periodically in the cross section of blood vessels (arteries). More specifically, at the lower left point in the figure, the inner diameter of the blood vessel was D, the tensile stress σ of the blood vessel wall, and the blood pressure P, but at the lower right point in the figure, the blood vessel diameter was D + dD, and the tension was high. The stress changes to σ + dσ, and the blood pressure changes to P + dP (d is synonymous with Δ).

Here, PWV can be expressed by parameters of the elastic modulus E of the blood vessel, the wall thickness c (constant value) of the blood vessel, the inner diameter D, and the blood density ρ. Of these parameters, the elastic modulus E of blood vessels is useful as an index indicating the degree of arterial wall sclerosis, but cannot be easily measured like blood pressure and pulse pressure. Therefore, the above (Equation 1) has been used for the purpose of obtaining the elastic modulus E of a blood vessel by substituting parameters such as pulse pressure measured by a conventional method.

(Structure of heart rate signal S)
FIG. 7 is a diagram showing an example of waveform data of the heartbeat signal S. The vertical axis V of the waveform data indicates the voltage value of the heartbeat signal S, and the horizontal axis t indicates the time (seconds).

Such waveform data is acquired by the heartbeat signal extraction unit 11 performing a filter process such as a bandpass on the sensor signal received by the microwave sensor 3.

As shown in the figure, from the sensor signal obtained by radiating microwaves toward the skin of the measurement target from the microwave sensor 3 arranged outside the body of the measurement target, the period caused by the beating of the heart A heartbeat signal S having a typical waveform is obtained. In the figure, three cycles of i to (i + 2) are shown.

Each of these cycles corresponds to a one-beat heartbeat, and the waveform of one cycle has a large amplitude and convex peak (systolic peak P1) and a smaller amplitude than the systolic peak P1 and is convex. A peak (reflected wave peak P2) is included. This reflected wave peak P2 is considered to be a reflected wave generated by the reflection of blood flow from the heart in a blood vessel, and may appear in continuously measured pulse pressure or a pulse wave.

(Pulse pressure estimation method)
Microwave sensor 3 heartbeat signal S extracted by the heartbeat signal extraction unit 11 from the detected radio wave, as shown in FIG. 5, the period pp _i caused by the biological heart, biological cardiac systolic blood pressure It has a systolic peak P1 shown and a reflected wave peak P2 generated by the blood flow ejected by contraction of the heart of a living body being reflected by a blood vessel.

Heartbeat signal S has further pulse transit time from the systolic peak P1 to the reflected wave peak P2 and _{(t i -t'} i), the amplitude _{a i.}

t _i represents the time of occurrence of the systolic peak P1. _t'i denotes the time of occurrence of the reflected wave peak P2. The cycle pp _i represents the time for one heartbeat. The amplitude _ai represents a change in blood flow associated with a change in cardiac output of the living body.

Pulse transit time _{(t i -t'} i) represents the organic change in defect of the blood vessel or hardening.

Pulse pressure estimation unit 16 may periodically pp _i acquired from the heartbeat signal S, a pulse wave propagation time calculated by the pulse wave propagation time calculating section _{13 (t} i -t' i), and the blood flow change calculator 12 The pulse pressure ΔP is estimated by substituting the three values of the _{calculated amplitude ai} of the heartbeat signal S into the following estimation formula (Equation 3).

The periodic pp _i, pulse transit time _(t i _-t' i), and the three values of the amplitude _{a i,} heart extracted from the radio waves reflected by the site (radial edge) indicated by arrow A in FIG. 4 Obtained from signal S.

From Bramwell-Hill (Equation 1), parameters that can be assumed to be constant in a short time are excluded, and Bramwell-Hill (Equation 1) is expanded to leave only the parameters directly related to blood pressure fluctuation (Equation 2). ..

Then, when the measured position is constant, because the propagation distance from the heart is constant, the pulse wave propagation velocity PWV, indicated by the pulse wave propagation time _(t i -t' _i), the amount of change ΔD of the inner diameter of the artery (Equation 2) can be expanded to (Equation 3) shown by the _{amplitude ai} , which represents the change in blood flow due to the change in the pulse rate of the heart of the living body.

Then, to deploy the pulse wave propagation velocity PWV, expressed as a percentage of the pulse wave propagation time _{(t i -t'} i) the period pp _i (Equation 4). The ratio of the pulse wave propagation time and _(t i -t' _i) the period pp _i is the rate of change of generation time in the one beat of the reflected wave caused by the blood flow from the heart is reflected by the blood vessel Shown.

Originally, when expanded from (Equation 1) of Bramwell-Hill, the above (Equation 3) is obtained. Since the pulse pressure estimating apparatus 10 according to the embodiment that is for the purpose of monitoring the relative change in blood pressure, calculating the pulse pressure ΔP as the rate of change in one beat of the pulse wave propagation time _(t i -t' _i) Therefore, the pulse pressure estimation unit 16 estimates the pulse pressure ΔP by the above (Equation 4). Actually, the pulse pressure ΔP can be estimated by the above (Equation 3).

(Pulse wave propagation velocity PWV, the validity of deploying the ratio of the pulse wave propagation time _{(t i -t'} i) the period pp _i)
The percentage change in the pulse wave propagation time of the occurrence time of the reflected wave peak _P2 (t i -t' _i) to the period pp _i which represents the length of one beat is, assuming a relative change, the pulse wave propagation velocity PWV It is assumed that the change is equivalent to that of.

For example, the ratio of the pulse wave propagation time and the period at the start of measurement _{((t i -t' i) /} pp i) . Relative to the ratio of time of a certain time from the time of the start of measurement has elapsed ((t _i -t' _i) / pp _i) changes in proportion to the hardness of the blood vessel. When the blood vessel becomes stiff, the value of this ratio becomes smaller than that at the start of measurement, and the blood pressure rises. On the contrary, when the blood vessel becomes soft, the value of this ratio becomes large and the blood pressure decreases.

Thus, the pulse wave propagation velocity PWV, there is a validity to expand the ratio of the pulse wave propagation time _{(t i -t'} i) a period pp _i.

_{(Relevance of setting the amplitude ai} of the heartbeat signal S as the amount of change ΔD in the inner diameter of the artery)
Blood pressure changes periodically as shown in FIG. 1 in response to fluctuations in cardiac output. It is also known that its value is affected by cardiac power, arterial wall elasticity, peripheral vascular resistance, and personal characteristics. In addition, it is known that these effects are reflected in the pulse wave waveform, that is, the pulse wave contains blood pressure information, and there is a blood pressure estimation method using the pulse wave as described above. ..

Then, according to the research by the inventors of the present application, it was found that the reflected wave (the above-mentioned sensor signal) reflected by the microwave in a human (or other animal) also contains information on the extensibility and rigidity of blood vessels. I came. The mechanism by which blood pressure information is included in the sensor signal has not been completely elucidated, but minute movements on the body surface (body surface fine movement) are reflected in the sensor signal, so that the sensor signal contains blood pressure. It is presumed that information will be included.

Here, the increase in cardiac output is related to the increase in cardiac output in the heart, and as the cardiac output increases, the pressure applied to the blood vessel wall increases and the blood vessel diameter expands. Then, it is considered that such an increase in pressure applied to the blood vessel wall and an increase in blood vessel diameter are reflected in the reflected wave of the microwave. _{Therefore, it is considered that the amplitude ai} of the heartbeat signal S extracted from the reflected wave of the microwave is a value reflecting the increase / decrease in the blood vessel diameter. That is, it is considered that the value of the heartbeat signal S increases as the pressure applied to the blood vessel wall increases and the blood vessel diameter expands, and the heartbeat signal S also reaches its maximum when the blood vessel diameter reaches its maximum. _{Therefore, it is appropriate to use the amplitude ai} of the heartbeat signal S as the change amount ΔD of the inner diameter of the artery and to use the peak height of the heartbeat signal S as the blood vessel diameter D.

(Flow of pulse pressure estimation processing by pulse pressure estimation system 100)
Next, the flow of the pulse pressure estimation process (pulse pressure estimation method) by the pulse pressure estimation system 100 will be described with reference to FIG. FIG. 8 is a flowchart showing an example of pulse pressure estimation processing.

In step S1, the microwave sensor 3 of the pulse pressure estimation system 100 transmits microwaves to the measurement target person. In step S2, the microwave sensor 3 detects a signal reflected by the measurement target person by the transmitted microwave as a sensor signal, and transmits the sensor signal to the pulse pressure estimation device 10.

In step S3, the heartbeat signal extraction unit 11 of the pulse pressure estimation device 10 acquires the sensor signal received from the microwave sensor 3 and extracts the heartbeat signal S from the sensor signal using, for example, a bandpass filter.

In step S4, the sensor signal is analyzed to calculate each parameter used for pulse pressure estimation. The parameter calculation process will be described in detail later.

In step S5, the pulse pressure estimation unit 16 of the pulse pressure estimation device 10 substitutes the parameter calculated in step S4 into the above-mentioned (Equation 3) stored in the storage unit 2 to estimate the pulse pressure ΔP. To do. Further, in step S6, the pulse pressure estimation unit 16 outputs the pulse pressure ΔP obtained by the estimation to the display device 5 and displays it.

(Flow of parameter calculation process)
Subsequently, the flow of the parameter calculation process performed in step S4 of FIG. 8 will be described with reference to FIG. FIG. 9 is a flowchart showing an example of the parameter calculation process.

Blood flow change calculator 12 analyzes the waveform data of the heartbeat signal S, to identify the period pp _i of the waveform, the maximum value D _s of the systolic peak P1 of the waveform included in one cycle pp _i identified And the minimum value D _d are specified. Then, the difference between the maximum value D _s and the minimum value D _{d is calculated as the amplitude ai} of the heartbeat signal S representing the amount of change in blood flow accompanying the change in stroke amount corresponding to the amount of change in blood vessel diameter ΔD (step S10). Then, the blood flow change amount calculation unit 12 notifies the pulse pressure estimation unit 16 of _{the calculated amplitude ai of the heartbeat signal S.}

Further, the pulse wave propagation time calculating unit 13 analyzes the waveform data of the heartbeat signal S, the time to identify the period pp _i of the waveform, systolic peak P1 of the waveform included in the specified period pp _i generated t pulse transit time from _i to time _t'i of reflected wave peak P2 is generated to calculate the _{(t i -t'} i) _(step S11). Then, the calculated pulse wave propagation time _{(t i -t'} i) notifies the pulse pressure estimating unit 16.

Although FIG. 9 shows an example in which the process of step S11 is performed after the process of step S10, the process of step S11 may be performed first, or these processes may be performed in parallel. ..

(Accuracy of pulse pressure estimation system 100)
Hereinafter, the correlation between the pulse pressure ΔP estimated by the pulse pressure estimation system 100 and the pulse pressure measured by the conventional method will be described with reference to FIG. FIG. 10 is a waveform diagram showing the correlation between the pulse pressure ΔP of the living body estimated by the pulse pressure estimation system 100 and the pulse pressure of the living body measured by the continuous blood pressure monitor. The vertical axis shows the normalized pulse pressure value, and the horizontal axis shows the time (seconds).

By actively straining it closes the glottis, muscle tension increases and intra-abdominal pressure increase occurs, the Valsalva test raising-lowering blood pressure of the subject _{S A · S B · S C} · S D · S E · S F 6 It was carried out for the name, and the measured value (Reference) by the conventional continuous blood pressure monitor was compared with the estimated value (Rstimated Value) by the estimation method according to the present embodiment. This Valsalva test is a test method for confirming whether changes in blood pressure due to vascular fluctuations can be monitored during a sphygmomanometer test.

As shown in the above (Table 1), between the values measured by the conventional continuous sphygmomanometer and the values estimated by the estimation method according to the present embodiment, all subjects S _A , S _B , S _C , S _D , S _A relatively high correlation was confirmed in E / S _F. Then, as shown in the graph of FIG. 10, it was found that the estimated value (Rstimated Value) by the estimation method according to the present embodiment changes with time in the same manner as the pulse pressure value by the conventional continuous blood pressure monitor. ..

As described above, the pulse pressure ΔP estimated by the pulse pressure estimation system 100 has an extremely high correlation with the pulse pressure value measured by the conventional method, although it is not necessary to touch the measurement target person at all. Since the pulse pressure ΔP estimated by the pulse pressure estimation system 100 changes with time in the same manner as the pulse pressure value measured by the conventional method, it is used for continuous monitoring of the pulse pressure value of the measurement target person. It can be seen that can also be suitably applied.

Further, the pulse pressure ΔP estimated by the pulse pressure estimation system 100 indicates a relative pulse pressure value, and as described above, it correlates with the pulse pressure value measured by the conventional method. Therefore, by calibrating the pulse pressure ΔP estimated by the pulse pressure estimation system 100, the absolute pulse pressure value (unit is mmHg, which is the same value as the pulse pressure value measured by the conventional method). It is also possible to calculate the value).

In the data of FIG. 10, first, the pulse pressure ΔP estimated by the pulse pressure estimation system 100 for the measurement target person is calculated, the pulse pressure value is measured by the conventional method, and then the exercise load is applied to the measurement target person. After that, the pulse pressure ΔP was estimated again and the pulse pressure value was measured by the conventional method. In addition, a sphygmomanometer using a cuff was used to measure the pulse pressure value by the conventional method.

(About the heart rate signal S to be used)
In the above, an example of using the heartbeat signal S extracted from the sensor signal detected by the microwave sensor 3 has been described, but the heartbeat signal S used for estimating the correlation with the pulse pressure is a cycle caused by the heartbeat of the measurement target person. It is not limited to this example as long as it is a signal having a typical waveform.

For example, it is also possible to estimate the above-mentioned pulse pressure ΔP using a pulse wave signal. In this case, the pulse wave signal may be detected by using the pulse wave sensor instead of the microwave sensor 3. The pulse wave sensor to be used is not particularly limited as long as it can detect the pulse wave signal, but for example, the fingertip of the person to be measured is irradiated with LED light, and the reflected light (or transmitted light) is used to irradiate the pulse wave. A photoelectric (volume) pulse wave sensor that detects fluctuations in the light may be used. By using such a sensor, the heartbeat signal S can be obtained in a non-invasive manner without using a cuff or the like.

Incidentally, the pulse wave signal, since the blood pressure as well as the waveform (see Fig. 1), the period pp i of the parameters (heartbeat signal S in the same operation as the present _embodiment, the amplitude a _i of the heartbeat signal _S, a pulse wave propagation time _(t i _-t' i)) can be calculated. Then, by using these parameters, the pulse pressure ΔP can be estimated.

(Other examples of parameters)
In the present embodiment, an example of estimating the pulse pressure ΔP is multiplied by the amplitude a _i of the heartbeat signal S to the square of the ratio of the pulse wave propagation time _(t i -t' _i) a period pp _i, calculated The parameter to be used may be any parameter that correlates with the pulse pressure, and is not limited to this example. For example, for pulse waves, velocity pulse waves (first derivative), acceleration pulse waves (second derivative), and the like are used for diagnosis. Therefore, first derivative and the multiplication result between the amplitude a _i of the squared and heartbeat signal S of the ratio of the pulse wave propagation time _(t i -t' _i) a period pp _i, also associated with blood pressure, such as second derivative There is a possibility that it can be used as medical information, and such a value may be calculated as a parameter correlated with pulse pressure.

(Example of realization by software)
The control block (particularly the control unit 1) of the pulse pressure estimation device 10 may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by using a CPU (Central Processing Unit). It may be realized by software.

In the latter case, the pulse pressure estimation device 10 is a CPU that executes instructions of a program that is software that realizes each function, and a ROM (Read Only Memory) in which the program and various data are readablely recorded by a computer (or CPU). ) Or a storage device (these are referred to as "recording media"), a RAM (Random Access Memory) for developing the above program, and the like. Then, the object of the present invention is achieved by the computer (or CPU) reading the program from the recording medium and executing the program. As the recording medium, a "non-temporary tangible medium", for example, a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. Further, the program may be supplied to the computer via an arbitrary transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. The present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the above program is embodied by electronic transmission.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

3 Microwave sensor (non-contact sensor, irradiation device)
11 Heart rate signal extraction unit (extraction unit)
16 Pulse pressure estimation part (estimation part)
10 the time of occurrence of the pulse pressure estimating device 100 pulse pressure estimating system P1 systolic peak P2 reflected wave peak pp _i periodic S heartbeat signal _{a i} amplitude ΔP pulse pressure _{t i} the occurrence of peak systolic P1 time _{t i} 'reflected wave peak P2

Claims (10)

From the radio waves reflected by the body surface of the living body, the cycle caused by the heartbeat of the living body, the systolic peak indicating the systolic blood pressure of the heart of the living body, and the blood flow ejected by the contraction of the heart are blood vessels. An extraction unit that extracts a heartbeat signal having a reflected wave peak indicating the hardness of a blood vessel based on the reflected wave generated by being reflected by
It is provided with an estimation unit that estimates the pulse pressure of the living body based on the pulse wave propagation time from the systolic peak to the reflected wave peak, the period of the heartbeat signal, and the amplitude of the heartbeat signal. A characteristic pulse pressure estimation device. The estimation unit
t _i: time of occurrence of the systolic peak,
t _i ': the time of occurrence of the reflected wave peak,
pp _i : The cycle of the heartbeat signal representing the time for one beat of the heartbeat,
a _i : The amplitude of the heartbeat signal representing the change in blood flow accompanying the change in the cardiac output of the living body,
ΔP: Pulse pressure of the living body,
Then

The pulse pressure estimation device according to claim 1, wherein the pulse pressure of the living body is estimated based on the above. The pulse pressure estimation device according to claim 1, wherein the estimation unit estimates the pulse pressure of the living body for each cycle of the heartbeat signal. The pulse pressure estimation device according to claim 1, wherein the radio wave is a microwave. A non-contact sensor that detects radio waves reflected by the body surface of a living body,
The pulse pressure estimation device according to any one of claims 1 to 4 is provided.
A pulse pressure estimation system, wherein the extraction unit of the pulse pressure estimation device extracts the heartbeat signal from a radio wave detected by the non-contact sensor. The pulse pressure estimation system according to claim 5, further comprising an irradiation device that irradiates the radio wave toward the body surface of the living body. The pulse pressure estimation system according to claim 6, wherein the non-contact sensor and the irradiation device are integrally formed. From the radio waves reflected by the body surface of the living body, the cycle caused by the heartbeat of the living body, the systolic peak indicating the systolic blood pressure of the heart of the living body, and the blood flow ejected by the contraction of the heart are blood vessels. An extraction step of extracting a heartbeat signal having a reflected wave peak indicating the hardness of a blood vessel based on a reflected wave generated by being reflected by
It includes an estimation step of estimating the pulse pressure of the living body based on the pulse wave propagation time from the systolic peak to the reflected wave peak, the period of the heartbeat signal, and the amplitude of the heartbeat signal. A characteristic pulse pressure estimation method. Further including a detection step of detecting radio waves reflected by the body surface of the living body,
The pulse pressure estimation method according to claim 8, wherein the extraction step extracts the heartbeat signal from the radio wave detected by the detection step. A control program for operating a computer as the pulse pressure estimation device according to claim 1, wherein the computer functions as the extraction unit and the estimation unit.

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