WO2024057482A1

WO2024057482A1 - System and method for measuring blood vessel function

Info

Publication number: WO2024057482A1
Application number: PCT/JP2022/034563
Authority: WO
Inventors: 邦夫柏野; 允裕中野; 仁暢友池
Original assignee: 日本電信電話株式会社
Priority date: 2022-09-15
Filing date: 2022-09-15
Publication date: 2024-03-21

Abstract

This system (A1, A2, A3) for measuring blood vessel functions comprises: a cuff part (10) having a pressing section (11) wound around an arm or a leg of a subject; first sensors (21) which are provided to the cuff part (10) and disposed further toward an end side of the arm or the leg than the pressing section (11); and a calculation unit (33, 38, 40) which estimates parameters of a physical model representing a blood vessel of the subject, on the basis of an output signal from the first sensors (21) when the pressing force of the pressing section (11) has been changed.

Description

Vascular function measurement system and method

The present disclosure relates to a vascular function measurement system and method.

As society continues to age, dealing with lifestyle-related diseases among adults has become a major social issue. Particularly in the case of diseases related to hypertension, measurements of vascular function are basic and important indicators to be referred to in preventing arteriosclerosis and hypertension. Therefore, there is a need for a method and apparatus that allow subjects to easily and accurately measure vascular function. Regarding such measurement methods and devices, non-invasive and non-invasive methods that do not require infection control measures for subjects and are suitable for home medical care are desirable.

As a conventional technique for non-invasively measuring blood vessel function, for example, Patent Document 1 discloses a method of estimating blood vessel age from pulse waves. In this method, a pulse wave is detected using an optical pulse wave sensor, filter processing is performed to remove noise, and the pulse wave is differentiated once or twice to detect the peaks and troughs in the waveform. , the area between the top and the trough is calculated, an index is calculated based on the calculated area, and the blood vessel age is estimated.

Non-Patent Document 1 discloses a method for testing vascular endothelial function. Plethysmography, which is one of the methods for testing vascular endothelial function, measures changes in forearm volume with venous perfusion in the upper arm stopped, while non-invasive methods measure volume pulse waves by wrapping a cuff around the upper arm and measuring reactive congestion after avascularization is released.

Non-Patent Document 2 discloses a method of measuring blood vessel elasticity through morphological observation using ultrasound. In this method, the spatial distribution of elastic modulus within the arterial wall is measured transcutaneously by using a general-purpose medical ultrasound diagnostic device and performing special processing on the measurement data.

Japanese Patent Publication 2008-079813

However, the technique of Patent Document 1 captures the characteristics of the waveform and applies it to a template to statistically determine the vascular age, but it is not based on a physical model and cannot obtain detailed physical property parameters, so its accuracy is questionable. . The technique disclosed in Non-Patent Document 1 stops blood flow in the upper arm for a long time, which may place a heavy burden on the subject. The technology in Non-Patent Document 2 uses ultrasonic tomography to take ultrasound tomographic images in a direction perpendicular to the long axis of blood vessels, and examines how the cross-sectional shape of blood vessels changes due to blood flow and its changes. However, the medical ultrasound diagnostic equipment used is large and expensive, making it unsuitable for home medical care.

The present disclosure has been made in view of the above-mentioned circumstances. By applying blood vessels to a physical model and analyzing them, detailed physical parameters can be obtained, making it possible to measure blood vessel function with high precision. A small and inexpensive vascular function measurement system and method that can reduce the burden on the subject because the burden is only that of blood pressure measurement, and that can be used for home medical care because it is about the same size and price as a general brachial blood pressure measuring device. The purpose is to provide

In order to achieve the above object, a vascular function measuring system according to a first aspect of the present disclosure includes a cuff part having a pressurizing part wrapped around an arm or leg of a subject; A first sensor disposed closer to the distal side of the arm or leg than the pressurizing section, and a blood vessel of the subject based on the output signal of the first sensor when the pressurizing force of the pressurizing section is changed. an arithmetic unit that estimates parameters of a physical model representing .

The vascular function measuring method according to the second aspect of the present disclosure is characterized in that when the pressurizing force of the pressurizing part wrapped around the arm or leg of the subject is changed, the arm or leg An output signal of a first sensor located on the distal side is acquired, and parameters of a physical model representing the blood vessel of the subject are estimated based on the acquired output signal of the first sensor.

According to the present disclosure, it is possible to provide a vascular function measurement system and method that can measure vascular function with high precision, place less burden on the subject, and are small and inexpensive.

1 is a schematic diagram showing a vascular function measurement system according to a first embodiment of the present disclosure. FIG. 2 is a schematic diagram showing a blood vessel distribution constant circuit model. FIG. 7 is a schematic diagram showing a circuit representing one blood vessel in a first modification of the blood vessel distribution constant circuit model. FIG. 7 is a schematic diagram showing a first modification of a blood vessel distribution constant circuit model. FIG. 7 is a schematic diagram showing a circuit representing a heart valve in a second modification of the blood vessel distribution constant circuit model. FIG. 7 is a schematic diagram showing a second modification of the blood vessel distribution constant circuit model. It is a graph showing the measurement results of the sensor. FIG. 3 is a diagram comparing the frequency spectrum of the sound of blood flow and the simulation results of the calculation unit. It is a graph showing simulation results of blood vessel pressure by a calculation unit. FIG. 2 is a schematic diagram of a vascular function measurement system according to a second embodiment of the present disclosure. FIG. 3 is a schematic diagram of a vascular function measurement system according to a third embodiment of the present disclosure.

(First embodiment)
Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a vascular function measurement system according to a first embodiment of the present disclosure. The vascular function measurement system A1 of this embodiment shown in FIG. 1 is a system that measures the function of a blood vessel of a subject. More specifically, the vascular function measurement system A1 is a system that estimates parameters of a physical model representing a blood vessel of a subject and measures specific vascular function from the estimated parameters.

As shown in FIG. 1, the vascular function measurement system A1 includes a cuff part 10 that is attached to the arm of a subject and that acquires information necessary for estimating the parameters of the physical model, and a cuff part 10 that is not provided in the cuff part 10. , a third sensor 23 that is attached near the heart of the subject, and an operation control section 30 that can be operated by the user and controls the cuff section 10. Note that the subject may operate the operation control unit 30. The size of the vascular function measurement system A1 of this embodiment is comparable to that of a typical home automatic blood pressure monitor worn on the arm of a subject.

The cuff portion 10 is a sheet-like member that can be wrapped around the subject's arm (upper arm or forearm) and has a rectangular shape when expanded. The material of the cuff part 10 is not particularly limited as long as it is a flexible sheet material with low elasticity, and cloth, resin film, etc. can be used. Note that the cuff portion 10 may be attached to the leg (thigh or lower leg) of the subject. Hereinafter, when "arm" is written, it means "arm or leg".

The cuff part 10 is equipped with a holding member for maintaining the state in which it is wrapped around the subject's arm. As the holding member, a hook and loop fastener, a hook, a fixing band, etc. can be used. This holding member has enough strength to maintain fixation of the cuff part 10 to the subject's arm even when pressurized by the pressurizing part 11, which will be described later. Note that in the following description, the direction along the arm of the subject may be referred to as the long axis direction. A direction perpendicular to the long axis direction is sometimes referred to as a radial direction. The direction around the arm is sometimes referred to as the circumferential direction. The upstream side in the flow direction of the artery in the arm of the subject may be simply referred to as the upstream side. The downstream side in the flow direction may be simply referred to as the downstream side.

The cuff part 10 includes a pressurizing part 11, a first sensor 21, and a second sensor 22. The pressurizing part 11 is provided on the inner surface of the cuff part 10 when it is attached to the subject's arm. The pressurizing part 11 is a belt-shaped bag extending in the circumferential direction, and expands when fluid is supplied thereinto. In this embodiment, the fluid supplied to the pressurizing section 11 is gas (air). The radially outer side of the pressurizing part 11 is held by the cuff part 10. Therefore, when gas is supplied into the pressurizing section 11 while the cuff section 10 is attached to the subject's arm, a pressurizing force based on the expansion of the pressurizing section 11 is applied to the subject's arm. be able to. That is, by supplying gas into the pressurizing section 11, it is possible to pressurize the subject's arm and stop or restrict blood flow in the arm. The first sensor 21 and the second sensor 22 are arranged so that the pressurizing part 11 is sandwiched between them in the longitudinal direction.

The first sensor 21 is provided in the cuff part 10 and is placed closer to the distal end of the subject's arm than the pressurizing part 11 is. In other words, the first sensor 21 is arranged downstream of the pressurizing section 11 . In this embodiment, the first sensor 21 is an acoustic sensor that measures sound in the audible range (20 Hz to 20 kHz). In this embodiment, an acoustic sensor is used as the first sensor 21 to measure sound in a blood vessel (artery or vein) of the subject. However, the first sensor 21 is not limited to an acoustic sensor, and for example, a pressure sensor can be used. When the first sensor 21 is a pressure sensor, the first sensor 21 measures blood vessel pressure fluctuations. Parameters of a physical model, which will be described later, can be estimated using blood vessel pressure fluctuations or blood flow sound fluctuations.

In this embodiment, a plurality of first sensors 21 are provided side by side in the circumferential direction. Since the position of a subject's blood vessels may vary from subject to subject, there is a possibility that a single sensor may not be able to appropriately measure the sound of blood flow. Therefore, as in the present embodiment, by providing a plurality of first sensors 21 and performing measurements respectively, and using the most appropriately measured result, it is possible to stably and appropriately measure the sound of blood flow.

The second sensor 22 is provided in the cuff part 10 and is placed closer to the proximal end of the subject's arm than the pressurizing part 11 (closer to the subject's heart). In other words, the second sensor 22 is arranged upstream of the pressurizing section 11 . In this embodiment, the second sensor 22 is an acoustic sensor that measures sound in the audible range (20 Hz to 20 kHz). Similar to the first sensor 21, the second sensor 22 may be a pressure sensor capable of measuring blood vessel pressure fluctuations. Similar to the first sensor 21, in this embodiment, a plurality of second sensors 22 are provided side by side in the circumferential direction.

The third sensor 23 is attached near the subject's heart. In other words, the third sensor 23 is attached to the chest of the subject. For example, a suction member is attached to the third sensor 23, and the third sensor 23 may be attached near the heart of the subject by adhering the suction member to the chest of the subject. In this embodiment, the third sensor 23 is an acoustic sensor that measures sounds in the audible range (20 Hz to 20 kHz), and measures heart sounds of the subject. The third sensor 23 may be a pressure sensor that can measure pressure fluctuations in the subject's heart or blood vessels. The third sensor 23 may have a built-in power supply and a communication function, and may wirelessly communicate with the operation control unit 30 to exchange signals. Whether the first sensor 21, second sensor 22, and third sensor 23 are acoustic sensors or pressure sensors may be appropriately selected depending on the system to be constructed.

The operation control section 30 is connected to the cuff section 10 via a cable 12. The cable 12 of this embodiment includes a power line and a signal line for the first sensor 21 and the second sensor 22, and a pressurizing tube for supplying gas to the pressurizing section 11. The operation control unit 30 includes a pressurizing unit control unit 31, a sensor control unit 32, a calculation unit 33, a storage unit 34, a communication unit 35, an operation unit 36, and a display unit 37. .

The functions of the pressurizing section control section 31, sensor control section 32, calculation section 33, storage section 34, and communication section 35 are performed by a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Realized. Some or all of these components are hardware (circuit parts) such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), GPU (Graphics Processing Unit); (including circuitry), or may be realized by collaboration between software and hardware. The program may be stored in advance in the storage unit 34 or the like, or may be stored in a portable storage medium (non-transitory storage medium) such as a DVD or CD-ROM, and the storage medium is the operation control unit. It may be installed in the storage unit 34 by being attached to a drive device connected to the drive unit 30 . Furthermore, some or all of the functions of the pressurizing section control section 31, the sensor control section 32, the calculation section 33, the storage section 34, and the communication section 35 may be realized by the same hardware. The pressurizing section control section 31 , the sensor control section 32 , the storage section 34 , the communication section 35 , the operation section 36 , and the display section 37 are electrically connected to the calculation section 33 .

The pressurizing unit control unit 31 controls the pressurizing operation of the pressurizing unit 11 based on the command signal from the calculating unit 33. The pressurizing section control section 31 includes a gas supply section (not shown). The gas supply section is a pump or the like, and is connected to the pressurizing section 11 via the pressurizing tube of the cable 12 . The gas supply section supplies gas to the pressurizing section 11 via the pressurizing tube.

The sensor control section 32 is electrically connected to the first sensor 21 , the second sensor 22 , the third sensor 23 , and the calculation section 33 . The sensor control unit 32 includes a power source that supplies operating power to the first sensor 21 , the second sensor 22 , and the third sensor 23 , and the sensor control unit 32 , the first sensor 21 , the second sensor 22 , and the third sensor 23 . , and an input/output interface for exchanging power and signals with the arithmetic unit 33. That is, the sensor control unit 32 controls the operations of the first sensor 21 , the second sensor 22 , and the third sensor 23 based on the command signal from the calculation unit 33 , and also controls the operation of the first sensor 21 , the second sensor 22 , and The output signal of the third sensor 23 is acquired and the signal is output to the calculation section 33.

The calculation unit 33 comprehensively controls the operations of the pressurizing unit control unit 31, the sensor control unit 32, the storage unit 34, the communication unit 35, the operation unit 36, and the display unit 37. Furthermore, the calculation unit 33 estimates parameters of a physical model representing the blood vessels of the subject, and measures blood vessel function from the estimated parameters. The specific measuring method will be described later.

The storage unit 34 includes, for example, at least one of RAM (Random Access Memory), ROM (Read Only Memory), HHD (Hard Disk Drive), and SSD (Solid State Disk). The storage unit 34 stores programs executed by the calculation unit 33, measurement results of the first sensor 21, second sensor 22, and third sensor 23, parameters of the physical model estimated by the calculation unit 33, blood vessel function, etc. do.

The communication unit 35 includes an input/output interface for exchanging information with devices external to the operation control unit 30. This input/output interface exchanges information with the device external to the operation control unit 30 via a network such as the Internet or a LAN (Local Area Network). The connection method between the communication unit 35 and the network may be either a wired connection or a wireless connection. The calculation unit 33 may acquire a program stored in a server or the like connected to the network via the communication unit 35 and store it in the storage unit 34, or the calculation unit 33 may acquire a program stored in a server or the like connected to the network and store it in the storage unit 34. Parameters, blood vessel functions, etc. may be transferred to a server or the like via the communication unit 35 and the network.

The operation unit 36 is a device that receives operation commands from the user, and includes, for example, a touch panel, an input switch, and the like. The display unit 37 is a device that notifies the user of the measurement results of the vascular function measurement system A1, and includes, for example, a display, a touch panel, an LED lamp, and the like. The operation section 36 and the display section 37 may be configured by the same touch panel.

The method for measuring vascular function performed by the vascular function measurement system A1 will be described below.
The vascular function measurement system A1 of this embodiment is configured to estimate the physical model parameters of the blood vessel by measuring the sound or pressure of the artery at multiple locations in the longitudinal direction. First, while pressurizing and depressurizing with the pressurizing part 11, sounds downstream of the pressurizing part 11, sounds upstream of the pressurizing part 11, and sounds near the heart are acquired, and acoustic waveforms and sounds are obtained. Record changes in the acoustic spectrum. Sounds downstream from the pressurizing section 11 are measured by the first sensor 21, sounds upstream from the pressurizing section 11 are measured by the second sensor 22, and sounds near the heart are measured by the third sensor 23. Measured by More specifically, the calculation section 33 gives a command to the pressurizing section control section 31 based on the operation of the operation section 36 by the user. The pressurizing section control section 31 controls the gas supply section connected to the pressurizing section 11 based on the command. As a result, gas is supplied to and discharged from the pressurizing section 11, and the subject's arm is pressurized and depressurized.

Simultaneously with pressurization and depressurization by the pressurizing unit 11, measurements are performed by the first sensor 21, second sensor 22, and third sensor 23. As mentioned above, the measurement target may be sound or pressure fluctuation. Measurement results (output signals) from the first sensor 21 , second sensor 22 , and third sensor 23 are input to the calculation unit 33 via the sensor control unit 32 .

The calculation unit 33 estimates parameters of a physical model representing the blood vessel of the subject based on the output signals of the first sensor 21, the second sensor 22, and the third sensor 23. An example of the calculation performed by the calculation unit 33 is a simulation in which a physical model representing the blood vessels of the subject is applied to a distributed constant circuit model. A general electric circuit simulator can be used for this simulation. More specifically, one blood vessel extending from the left ventricle to the periphery is represented by a distributed constant circuit model with the following elements. If blood pressure corresponds to voltage and blood flow corresponds to current, a distributed constant circuit model can be expressed as shown in FIG. 2, for example.

In FIG. 2, L, R, C, G, R _CUFF , Zo, M _P , M _Q , and _MR are defined as follows.
Inductance L: A resistance component against changes in blood flow that corresponds to inertial force in blood flow.
Resistance R: A resistance component to blood flow corresponding to the friction between the blood vessel wall and blood.
Capacitance C: A component that locally accumulates blood, corresponding to an increase in the inner diameter due to elastic deformation of the blood vessel.
Conductance G: A component that eliminates local accumulation of blood, which corresponds to the reciprocal of the restoring force of elastic deformation of the blood vessel.
Pressure force R _CUFF : Pressure force generated by the pressure unit 11. R _CUFF = 0 indicates a state in which the pressure unit 11 tightens the arm or leg, and R _CUFF = ∞ indicates a state in which the pressure unit is open.
Impedance Zo: represents a state where there is no reflection at the periphery of the blood vessel and the distributed constant circuit model is terminated with matched impedance.
M _P , M _Q , M _R : Measured values by the first sensor 21, the second sensor 22, and the third sensor 23.

In the distributed constant circuit model, pressurization and depressurization by the pressurizing unit 11 corresponds to measurement while changing the value of the pressurizing force R _CUFF , and the measurement result near the heart by the third sensor 23 corresponds to the power supply voltage. . In the distributed constant circuit model of this embodiment, pulse wave propagation, reflected waves, standing waves, etc. can be simulated.

In this embodiment, the first sensor 21, the second sensor 22, and the third sensor 23 generate sounds (blood flow sounds, heart sounds, Korotkoff sounds, etc.) while gradually changing the pressurizing force R _CUFF from 0 to ∞. Measure pressure fluctuations in blood vessels. Based on this measurement result, each circuit element parameter (corresponding to the state of blood vessels) and the voltage and current at each node in the circuit (corresponding to blood pressure and blood flow) are estimated. This can be expected to be useful in health management or clinical medicine, such as estimation of blood vessel conditions.

The physical correspondence with circuit elements in the physical model of this embodiment is close to the Windkessel model shown in Non-Patent Document 3, but in this disclosure, in order to analyze the propagation of pulse waves, reflected waves, and standing waves, The important difference is that it is a distributed constant circuit. That is, the model of Non-Patent Document 3 is represented by a lumped constant circuit.

Note that in FIG. 2, the circuit diagrams are shown in one system for ease of understanding. However, in reality, blood vessels branch in the body, so the corresponding circuit diagram also branches. A first modification is shown as a circuit diagram having branches. FIG. 3 is a schematic diagram showing a circuit V representing one blood vessel in a first modification of the blood vessel distribution constant circuit model. FIG. 4 is a schematic diagram showing a first modification of the blood vessel distribution constant circuit model. The circuit diagram shown in FIG. 4 includes a plurality of circuits V. Since one circuit V represents one blood vessel, the circuit diagram in FIG. 4 represents the state in which the blood vessel branches into multiple branches within the body. More specifically, in FIG. 4, the upper plurality of circuits V represent arteries, and the lower plurality of circuits V represent veins. Simulation is possible even when the circuit diagram is branched like this. In other words, it is also possible to consider the branching of blood vessels within the body and model the whole body's blood flow dynamics in the same way.

For example, it is also possible to model a heart valve as a series and parallel connection of a diode and a resistor, and evaluate the health of the valve based on the magnitude of the resistance value. More specifically, in a circuit with diodes placed in the direction of normal blood flow, if the series resistance is small and the parallel resistance is large, the valve is healthy; if the parallel resistance is small, there is backflow, and the series resistance is large. In these cases, it can be evaluated that there is a blood flow disorder due to stenosis, etc. Furthermore, it is also possible to add a circuit with a diode arranged in the reverse flow direction to evaluate reverse flow. A second modification is shown as a circuit diagram modeling a heart valve. FIG. 5 is a schematic diagram showing a circuit representing a heart valve in a second modification of the blood vessel distribution constant circuit model. As shown in FIG. 5, a heart valve can be represented by a combination of resistors and diodes. FIG. 6 is a schematic diagram showing a second modification of the blood vessel distribution constant circuit model. As shown in FIG. 6, the heart can be represented by multiple valves (see FIG. 5), multiple variable capacitance capacitors, etc. For example, the atria and ventricles repeatedly expand and contract, so the amount of blood that can be held inside changes over time. This state can be represented by changing the capacitance of the variable capacitor over time.
Note that although the distributed constant circuit model of the present embodiment described above does not take into account the circulation effect due to smooth muscle contraction of the blood vessel itself, this smooth muscle contraction may be added as a distributed voltage source.
Further, each distribution constant may be time-varying.

FIG. 7 shows an example of observation by the first sensor 21, the second sensor 22, and the third sensor 23. The horizontal axis in FIG. 7 represents time. More specifically, it shows the sequence of time in which the upper arm is pressurized, blood flow is blocked, the pressure is gradually reduced, and the upper arm is released. In FIG. 7, from the top, the measurement results on the upstream side of the pressurizing section 11 (i.e., the measurement results of the second sensor 22), the measurement results on the downstream side of the pressurizing section 11 (i.e., the measurement results of the first sensor 21), and The measurement results near the heart (ie, the measurement results of the third sensor 23) are shown. The upper part of each measurement result is a time axis waveform, and the lower part is a spectrogram. The spectrogram on the upstream side of the pressurizing section 11 shows a water hammer sound when blood flow is blocked. Further, in the spectrogram on the downstream side of the pressurizing section 11 at the stage of gradual pressure reduction, the resonance characteristics change as the pressure is reduced and Korotkoff sounds are observed.

Due to changes in the pressurizing force of the pressurizing section 11, physical parameters change, and Korotkoff sounds are observed. FIG. 8 shows a frequency spectrum on the downstream side of the pressurizing section 11, which corresponds to resonance characteristics when Korotkoff sounds are observed. FIG. 8(a) shows the frequency spectrum in the simulation results of the output signal of the first sensor 21, and FIG. 8(b) shows the measurement results of the

sensors

21, 22, and 23. The frequency spectrum in FIG. 8(a) corresponds to the resonance characteristics within the rectangular frame shown in FIG. 8(b).

As one method for estimating the parameters of the physical model of the blood vessel corresponding to the measurement results of the sensor, the parameters may be estimated by forward simulation, for example. Specifically, the calculation unit 33 starts a simulation of the distributed constant circuit model using the trial parameters, and the simulation results and the output signals of the first sensor 21, the second sensor 22, and the third sensor 23 indicate The time axis waveform and the frequency spectrum are compared, and the parameters are determined by repeating simulation and comparison while changing the trial parameters to other values until they match with a predetermined accuracy.
Note that during forward simulation, a numerical range that a parameter should take may be set in advance, or a condition that should be satisfied between each parameter may be defined in advance. Regarding the latter, for example, the condition is that the series resistance value and the position in the longitudinal direction of the blood vessel have a linear relationship.

Various methods can be considered to determine whether the sensor measurement results and simulation results match with a predetermined accuracy. For example, to determine whether the spectra are similar to each other, the squared Euclidean distance of the spectra, the Itakura-Saito distance, the KL divergence, the comparison of polar frequencies by linear predictive analysis, etc. can be used.

As mentioned above, the sensor of this embodiment measures the sound of blood flow, but it may also measure the pressure of blood vessels. FIG. 9 shows the temporal change in pressure obtained by circuit simulation. A sensor may measure blood vessel pressure fluctuations, a corresponding simulation may be performed, and a forward simulation may be performed based on both results to estimate the parameters of the physical model.

After estimating the parameters of the physical model, a specific vascular function is derived based on the parameters. Specific vascular functions include, for example, the hardness (stiffness) of the vascular wall and the strength of elasticity (elastic coefficient) of the vascular wall. In this embodiment, the calculation unit 33 also derives the vascular function, and the vascular function may be derived from the parameters using a regression equation or a neural network model.

As described above, the vascular function measurement system A1 of the present embodiment includes the cuff section 10 having the pressurizing section 11 that is wrapped around the arm or leg of the subject, and the cuff section 10 that is provided on the cuff section 10 and that A physical model representing the blood vessels of the subject is created based on the first sensor 21 disposed at the distal side of the arm or leg and the output signal of the first sensor 21 when the pressurizing force of the pressurizing section 11 is changed. and a calculation unit 33 for estimating the parameters of. With such a configuration, it is possible to provide a small and inexpensive vascular function measurement system A1 that can measure vascular function with high precision, places less burden on the subject.

Additionally, the vascular function measurement system A1 may include a second sensor 22 that is provided in the cuff section 10 and is disposed closer to the proximal end of the arm or leg than the pressurizing section 11 is. The vascular function measurement system A1 may include a third sensor 23 attached near the heart of the subject. By using these second sensor 22 and third sensor 23, more accurate estimation can be performed.

Furthermore, the calculation unit 33 may estimate the parameters of the physical model representing the blood vessel of the subject based on the time-domain waveform and the time change of the frequency spectrum represented by the output signal of the first sensor 21.

Furthermore, when estimating the parameters of the physical model representing the blood vessel of the subject, the calculation unit 33 may perform simulation by applying the physical model to the distributed constant circuit model. The distributed circuit constant model may include an inductance L, a resistance R, a capacitance C, a conductance G, a pressurizing force R _CUFF generated by the pressurizing section 11, and an impedance Zo. In this case, inductance L is a component of resistance to changes in blood flow, which corresponds to inertial force in blood flow, and resistance R is a component of resistance to blood flow, which corresponds to friction between the blood vessel wall and the blood. , capacitance C is a component that locally accumulates blood, which corresponds to an increase in the inner diameter due to elastic deformation of the blood vessel, and conductance G is a component that locally accumulates blood, which corresponds to the reciprocal of the restoring force of elastic deformation of the blood vessel. The pressing force R _CUFF represents a state where the pressurizing part 11 tightens the arm or leg when R _CUFF = 0, and a state where the pressurizing part 11 is open when R _CUFF = ∞, and the impedance Zo is It may also represent a state in which there is no reflection at the periphery of the blood vessel and the distributed circuit constant model is terminated with matched impedance.

Further, the calculation unit 33 starts a simulation of the distributed constant circuit model using the trial parameters, and compares the simulation result with the time axis waveform and frequency spectrum indicated by the output signal of the first sensor 21, so that both of them are set to a predetermined value. The parameters may be determined by repeatedly performing simulation and comparison while changing the trial parameters to other values until they match with an accuracy of .

In addition, in the vascular function measurement method of the present embodiment, when the pressure applied by the pressurizing part 11 wrapped around the subject's arm or leg is changed, the pressure is applied to the distal side of the arm or leg rather than the pressurizing part 11. The output signal of the located first sensor 21 is acquired, and based on the acquired output signal of the first sensor 21, parameters of a physical model representing the blood vessel of the subject are estimated.

(Second embodiment)
Next, a second embodiment according to the present disclosure will be described, which has the same basic configuration as the first embodiment. Therefore, similar configurations will be given the same reference numerals and their explanations will be omitted, and only the different points will be explained. Note that the third sensor 23 is not provided in the vascular function measurement system A2 of this embodiment.

As shown in FIG. 10, the first sensor 21 in the vascular function measurement system A2 of the present embodiment includes an upstream first sensor 21a disposed downstream of the pressurizing section 11, and a downstream side of the upstream first sensor 21a. and a first downstream sensor 21b disposed on the side. A plurality of the first upstream sensors 21a and the first downstream sensors 21b are provided, and are arranged side by side in the circumferential direction. In the longitudinal direction, the pressurizing part 11, the first upstream sensor 21a, and the first downstream sensor 21b are arranged in order from the upstream side to the downstream side.

The second sensor 22 of the present embodiment includes a second downstream sensor 22a disposed upstream of the pressurizing part 11, a second upstream sensor 22b disposed upstream of the second downstream sensor 22a, Equipped with A plurality of downstream second sensors 22a and a plurality of upstream second sensors 22b are provided, and are arranged in parallel in the circumferential direction. In the longitudinal direction, the upstream second sensor 22b, the downstream second sensor 22a, and the pressurizing part 11 are arranged in order from the upstream side to the downstream side.
With such a configuration, the sensors are arranged at more locations in the long axis direction, so that highly accurate estimation can be performed.

(Third embodiment)
Next, a third embodiment according to the present disclosure will be described, which has the same basic configuration as the first embodiment. For this reason, similar configurations are given the same reference numerals and explanations thereof will be omitted, and only the different points will be explained.
In this embodiment, as shown in FIG. 11, the operation control unit 30 includes a first calculation unit 38 instead of the calculation unit 33 of the first embodiment, and the vascular function measurement system A3 includes a second calculation unit 40. Equipped with The structural configurations of the first arithmetic unit 38 and the second arithmetic unit 40 are similar to the arithmetic unit 33 of the first embodiment. The second calculation unit 40 is constructed in a server or the like connected to a network such as a LAN or the Internet, and is configured to be able to communicate with the communication unit 35 via the network. The connection between the second arithmetic unit 40 and the communication unit 35 may be either a wired connection or a wireless connection.

The combined functions of the first calculation section 38 and the second calculation section 40 of this embodiment correspond to the functions of the calculation section 33 of the first embodiment. That is, the first calculation unit 38 estimates parameters of a physical model representing the blood vessels of the subject, transmits the estimated parameters to the second calculation unit 40 via the communication unit 35, and sends the estimated parameters to the second calculation unit 40 via the communication unit 35. However, the vascular function may be derived using the acquired parameters. The derived blood vessel function may be inputted from the second calculation unit 40 to the operation control unit 30 via the communication unit 35 under the control of the first calculation unit 38 and displayed on the display unit 37.

On the other hand, the second calculation unit 40 may be configured to perform both the parameter estimation operation and the blood vessel function derivation operation. In this case, the first calculation section 38 acquires the control operations of the pressurizing section control section 31 and the sensor control section 32 and the measurement results of the sensors via the sensor control section 32, and performs the second calculation via the communication section 35. A transfer operation for transferring data to the unit 40 is performed, but an operation for estimating parameters and an operation for deriving blood vessel function are not performed. The parameters and blood vessel function obtained by the second calculation unit 40 are input from the second calculation unit 40 to the operation control unit 30 via the communication unit 35 under the control of the first calculation unit 38 and are displayed on the display unit 37. may be done.

In any of the above examples, since the function of the calculation section in the operation control section 30 can be simplified, the vascular function measurement system A3 can be further simplified and downsized. In addition, since the second calculation unit 40 that performs parameter estimation etc. is built on a server etc. connected to a network, even if it becomes necessary to update the algorithm etc. used for estimation, the second calculation unit 40 It is only necessary to update the following files, which reduces the effort involved in updating.

Note that the technical scope of the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention.

For example, in the embodiment described above, sensors are provided at multiple locations in the longitudinal direction of the cuff portion 10, and a third sensor 23 near the heart is also used. However, in order to estimate the parameters of the physical model representing the blood vessel of the subject, it is sufficient that at least the first sensor 21 disposed downstream of the pressurizing section 11 is provided. For example, in the first embodiment described above, a configuration in which the second sensor 22 and the third sensor 23 are not provided in the vascular function measurement system A1 is also acceptable. Even with a configuration in which only the first sensor 21 is provided, parameters can be estimated with sufficient accuracy.

In addition, the components in the embodiments described above can be replaced with well-known components as appropriate without departing from the spirit of the present invention, and the embodiments and modifications described above may be combined as appropriate.

The present disclosure can be applied to a system and method for measuring vascular function of a subject.

10... Cuff part 11... Pressurizing part 21... First sensor 22... Second sensor 23... Third sensor 33... Calculating part 38... First calculating part 40... Second calculating part A1, A2, A3... Vascular function measurement system

Claims

a cuff portion having a pressurizing portion that is wrapped around the arm or leg of the subject;
a first sensor provided in the cuff part and located closer to the distal end of the arm or leg than the pressurizing part;
a calculation unit that estimates parameters of a physical model representing a blood vessel of the subject based on an output signal of the first sensor when changing the pressurizing force of the pressurizing unit;
A vascular function measurement system.
The vascular function measurement system according to claim 1, further comprising a second sensor that is provided in the cuff part and is located closer to the proximal end of the arm or leg than the pressurizing part.
The vascular function measuring system according to claim 1, comprising a third sensor attached near the heart of the subject.
The vascular function measurement system according to claim 2, comprising a third sensor attached near the heart of the subject.
The vascular function measurement according to any one of claims 1 to 4, wherein the calculation unit estimates the parameter based on a time change in a time axis waveform and a frequency spectrum represented by the output signal of the first sensor. system.
The calculation unit performs simulation by applying the physical model to a distributed constant circuit model when estimating the parameter;
The distributed constant circuit model includes an inductance L, a resistance R, a capacitance C, a conductance G, a pressurizing force R CUFF generated by the pressurizing section, and an impedance Zo,
The inductance L is a resistance component to a change in the blood flow corresponding to an inertial force in the blood flow,
The resistance R is a resistance component to blood flow corresponding to friction between the blood vessel wall and the blood,
The capacitance C is a component that locally accumulates blood, corresponding to an increase in the inner diameter due to elastic deformation of the blood vessel,
The conductance G is a component that eliminates local accumulation of blood, which corresponds to the reciprocal of the restoring force of elastic deformation of the blood vessel,
The pressurizing force R CUFF represents a state in which the pressurizing part tightens the arm or leg when R CUFF = 0, and a state in which the pressurizing part is open when R CUFF = ∞,
The impedance Zo represents a state in which there is no reflection at the periphery of the blood vessel and the distributed constant circuit model is terminated with a matched impedance.
The vascular function measurement system according to claim 5.
The calculation unit starts a simulation of the distributed constant circuit model using the trial parameters, compares the simulation result with a time axis waveform and a frequency spectrum indicated by the output signal of the first sensor, and compares the result of the simulation with a time axis waveform and a frequency spectrum indicated by the output signal of the first sensor, so that both of them are determined to be a predetermined value. 7. The vascular function measuring system according to claim 6, wherein the simulation and the comparison are repeatedly performed while changing the trial parameter to other values until the parameters match with an accuracy of .
Obtaining an output signal of a first sensor located closer to the distal end of the arm or leg than the pressurizing part when changing the pressurizing force of the pressurizing part wrapped around the arm or leg of the subject;
estimating parameters of a physical model representing the blood vessel of the subject based on the acquired output signal of the first sensor;
Vascular function measurement method.