Blood pressure estimation device, blood pressure estimation method, and blood pressure estimation program

Abstract

The absolute value of blood pressure can be directly estimated from a pulse wave signal with fewer processing steps, and the accuracy of blood pressure estimation can be improved. A blood pressure estimation device (1) comprises: a first pulse wave information detection unit (313) that detects first pulse wave information at a first position of a living body; a second pulse wave information detection unit (313) that detects second pulse wave information at a second position of the living body that is spaced apart from the first position in a vertical direction; and a blood pressure estimation unit (314) that estimates the blood pressure of the living body based on comparison value information of the first pulse wave information obtained by the first pulse wave information detection unit and the second pulse wave information obtained by the second pulse wave information detection unit.

Description

Technical Field

[0001] The present invention relates to a blood pressure estimation device, a blood pressure estimation method and a blood pressure estimation program. Background Art

[0002] Conventionally, blood pressure is measured by wearing a contact sensor on the body. However, such conventional methods are troublesome to wear the sensor, require conscious blood pressure measurement, and are difficult to make people accustomed to blood pressure measurement. Furthermore, the blood pressure of non-specific persons other than the sensor wearer cannot be measured.

[0003] In contrast, in recent years, a method for obtaining a pulse wave signal remotely / contactlessly based on a video signal obtained by photographing a body with a camera has been proposed (Patent Document 1 and Non-Patent Document 1). Specifically, this method extracts a video pulse wave signal by performing signal processing on the brightness values ​​of a body video signal involving multiple frames, and calculates a numerical value related to blood pressure. In particular, according to the method of Patent Document 1, the phase difference between the video pulse wave signal of a part of the body close to the heart (proximal part) and the video pulse wave signal of a part of the body far from the heart (distal part) is calculated as a value related to blood pressure. In addition, according to the method of Non-Patent Document 1, the difference between the boundary time from the diastole to the systole of the video pulse wave at any part of the body and the time at which the extreme value of the fundamental wave of the video pulse wave is given is calculated as a value related to blood pressure.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 6072893

[0007] Non-patent literature

[0008] Non-patent document 1: Norihiro Sugita, Makoto Yoshizawa, Makoto Abe, Akira Tanaka, Noriyasu Homma, Tomoyuki Yambe: Contactless technique for measuring blood-pressure variability from one region in video plethysmography, Journal of Medical and Biological Engineering.pp.1-10,(2018)https: / / doi.org / 10.1007 / s40846-018-0388-8. Summary of the invention

[0009] Problems to be solved by the invention

[0010] In the techniques of the above-mentioned documents, even if the values ​​related to blood pressure can be obtained, in order to estimate the absolute value of blood pressure based on the related values ​​of blood pressure, it is necessary to obtain the parameters (regression coefficient, deviation) of the regression equation that gives the two. The "absolute value" mentioned here does not refer to the mathematical meaning of the numerical value corresponding to the distance from the origin, but refers to the value of the original unit of the measurement quantity as the antonym of "relative value". However, these parameters are different for each subject, and in order to obtain these parameters, it is necessary to estimate based on the true blood pressure value obtained using the conventional contact sensor under the condition that each subject produces blood pressure fluctuations by some method, and the processing steps are numerous and complicated.

[0011] In addition, in the method using the pulse wave propagation velocity of the pulse wave, information on the time axis is required to obtain the time difference and phase difference, but in order to obtain the time information, a high-performance CPU and complex program processing for analyzing the pulse wave are required, making it difficult to obtain accurate values.

[0012] The blood pressure estimation device, blood pressure estimation method and blood pressure estimation program of the present invention are completed in view of the above-mentioned problems, and provide a new blood pressure estimation device, blood pressure estimation method and blood pressure estimation program that can directly estimate the absolute value of blood pressure based on the pulse wave signal even without information in the time axis direction such as the phase difference of the pulse wave.

[0013] Means for solving problems

[0014] The blood pressure estimation device disclosed herein includes: a first pulse wave information detection unit, which detects first pulse wave information at a first position of a biological body; a second pulse wave information detection unit, which detects second pulse wave information at a second position of the biological body that is separated from the first position in a vertical direction; and a blood pressure estimation unit, which estimates the blood pressure of the biological body based on comparison value information (preferably pulse wave amplitude information) between the first pulse wave information obtained by the first pulse wave information detection unit and the second pulse wave information obtained by the second pulse wave information detection unit.

[0015] In addition, a blood pressure estimation method related to the above and a blood pressure estimation program capable of executing the above blood pressure estimation method are disclosed.

[0016] Effects of the Invention

[0017] According to the disclosed blood pressure estimation device, blood pressure estimation method and blood pressure estimation program, the blood pressure of a biological body is estimated based on comparison value information (preferably pulse wave amplitude information) between a first pulse wave information detected at a first position of the biological body and a second pulse wave information detected at a second position of the biological body separated from the first position in a vertical direction. This eliminates the need to calculate a time-dependent phase difference, etc., and enables the absolute value of the blood pressure to be directly estimated based on the pulse wave signal with fewer processing steps, thereby improving the accuracy of blood pressure estimation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 : is a block diagram illustrating a hardware configuration of a blood pressure estimation device according to an embodiment.

[0019] Figure 2 : is a block diagram illustrating a functional configuration of a blood pressure estimation device as an embodiment.

[0020] Figure 3 is a flow chart showing the blood pressure estimation steps.

[0021] Figure 4 It is a figure explaining an embodiment.

[0022] Figure 5 It is a figure explaining an embodiment.

[0023] Figure 6 1 and 12 are diagrams showing pulse wave signals obtained in the present embodiment, wherein (a) shows a high pulse wave signal and (b) shows a low pulse wave signal.

[0024] Figure 7 It is a figure explaining other embodiment. DETAILED DESCRIPTION

[0025] With reference to the accompanying drawings, a blood pressure estimation device, a blood pressure estimation method, and a blood pressure estimation program as embodiments are described. The embodiments shown below are merely illustrative, and there is no intention to exclude various modifications and technical applications not explicitly shown in the following embodiments. The various structures of the embodiments can be implemented with various modifications within the scope of their main purpose. In addition, they can be selected or discarded as needed, or they can be appropriately combined.

[0026] [1. Hardware structure]

[0027] First, refer to Figure 1 , an example of the hardware structure of the blood pressure estimation device according to the embodiment is described. Figure 1As shown, the blood pressure estimation device 1 of the embodiment includes a video acquisition device 2, an information processing device 3, and an output device 4. The video acquisition device 2 and the output device 4 are connected to the information processing device 3 in a manner that allows them to communicate with each other by wire or wirelessly. The blood pressure estimation device 1 may also include an input device such as a mouse, a keyboard, or an operation button (not shown).

[0028] <Video Acquisition Device>

[0029] The video acquisition device 2 is a device for capturing a predetermined part of a body of a living being (hereinafter, also referred to as a subject) in a non-contact state and acquiring continuous video information (video signal) in a time series. In the embodiment, a visible light camera equipped with a photographic lens and a visible light imaging element for receiving visible light is exemplified, but the invention is not limited thereto, and an infrared light camera or the like may also be used. The video acquisition device 2 outputs the acquired video signal to the information processing device 3.

[0030] The video acquisition device 2 may further include a lighting device 2A. The lighting device 2A is selected according to the type of the imaging element.

[0031] There is no particular limitation on the designated part of the subject's body that the video acquisition device 2 photographs. Generally, parts that are easy to photograph are preferred depending on how much of the skin surface is exposed, such as hands and faces. Among them, the palms, foreheads, and cheeks are preferably used from the perspective of the width of the shooting area. In particular, from the perspective of easily acquiring a video pulse wave with a high S / N ratio of the signal, parts where the arterioles are controlled by the sympathetic nerves when the blood pressure rises and the peripheral vascular resistance increases are preferred. Such parts include peripheral parts such as hands, legs, and other limbs, among which the hands are preferred, and the palms are more preferred.

[0032] The number of video acquisition devices 2 is not particularly limited. A desired predetermined portion may be extracted from a video from one video acquisition device 2, or a plurality of video acquisition devices 2 may capture the desired predetermined portion. When a plurality of video acquisition devices 2 are used, the lighting device 2A may be attached to each video acquisition device 2, or the lighting device 2A may be shared by each video acquisition device 2.

[0033] <Information Processing Device>

[0034] The information processing device 3 is composed of a computer such as a PC (Personal Computer) or a server. The information processing device 3 processes the video signal received from the video acquisition device 2 and outputs it to the output device 4. The information processing device 3 includes a CPU (Central Processing Unit) 3A, a memory 3B, a storage unit 3C, and an interface unit 3D. These are connected via a bus so as to be able to communicate with each other.

[0035] <cpu>

[0036] The CPU 3A is an example of a calculation processing device (processor) that performs various controls and calculations. The CPU 3A can realize the functions of the blood pressure estimation device 1 by developing in the memory 3B and executing a blood pressure estimation program stored in the storage unit 3C described later.

[0037] The blood pressure estimation program mentioned here is a program that causes the computer (CPU3A) to perform the following processing: detecting first pulse wave information at a first position of a biological body (subject), detecting second pulse wave information at a second position of the biological body that is separated from the first position in the vertical direction, and estimating the blood pressure of the biological body based on comparison value information between the first pulse wave information and the second pulse wave information.

[0038] In addition, embodiments of the first position and the second position of the living body, the first pulse wave information and the second pulse wave information, and the comparison value information will be described later.

[0039] <Memory>

[0040] The memory 3B and the storage unit 3C are storage devices that store various data and programs.

[0041] The memory 3B or the storage unit 3C described above can store a blood pressure estimation program or the like that realizes all or part of the various functions of the information processing device 3 .

[0042] The interface (IF) unit 3D is a communication interface for controlling the connection and communication between the information processing device 3, the video acquisition device 2, and the output device 4 based on a wired or wireless network. In addition, the blood pressure estimation program can also be downloaded from the network (not shown) to the CPU 3A via the IF and stored in the storage unit 3C.

[0043] The IF unit 3D may also include a reading unit (not shown) for reading data or programs recorded on the recording medium 3F. The reading unit may include a connection terminal or device that can be connected or inserted into the computer-readable recording medium 3F.

[0044] In addition, the blood pressure estimation program may be stored in the recording medium 3F.

[0045] <Output device>

[0046] The output device 4 is a device for providing information mainly through vision, and displays the video acquired by the video acquisition device 2, the result processed by the information processing device 3, and the like.

[0047] A mobile terminal such as a smartphone may be used as the output device 4. In this case, the output from the information processing device 3 is transmitted to the mobile terminal via the IF unit 3D via the communication network, and the output result is displayed on the display of the mobile terminal.

[0048] [2. Principle]

[0049] In a living body, blood pressure in various parts of the body changes synchronously with the pulsation of the heart. Due to this change, pulse pressure (the difference between the maximum blood pressure and the minimum blood pressure) is generated in each pulsation. Strictly speaking, this pulse pressure varies depending on the hardness of blood vessels in various parts, but it can be assumed that the pulse pressure is roughly the same in various parts of the body regardless of whether it is high or low.

[0050] On the other hand, in a living body, due to the pulsation of the heart, the pulse waves in various parts of the body also fluctuate synchronously with the pulsation. Due to this fluctuation, the difference between the maximum value and the minimum value of each fluctuation (the difference between the peak value of the maximum value and the valley value of the minimum value, hereinafter referred to as "pulse wave amplitude") is generated. This pulse wave amplitude varies depending on the vertical position of the body. In addition, as described later, it is also known that the relationship between blood pressure and the cross-sectional area of ​​the blood vessel associated with the pulse wave amplitude can be approximated by an exponential function having a deviation coefficient associated with the characteristics of the blood vessel.

[0051] Based on the above insights, the inventors of the present application conducted in-depth research and found that the coefficients related to the curvature of the pulse wave amplitude change related to blood pressure are determined by the vertical position of each part of the body. Although the deviation coefficient, which is the only unknown number in the derivation, varies from person to person, the approximate value is known in the literature, and if this value is used, the approximate blood pressure can be estimated, which is a groundbreaking value that does not require the true value of the blood pressure of the subject. In addition, even when obtaining a more accurate deviation coefficient corresponding to each subject, as long as there is a true value of the blood pressure, it can be obtained, and the blood pressure can be obtained even if the blood pressure fluctuation is not given to the subject.

[0052] Based on the above, by utilizing the relationship between height information of at least two arbitrary measurement positions having a height difference in the vertical direction and the pulse wave amplitude J of the pulse wave signal measured at the positions, the absolute value of blood pressure can be directly estimated from the pulse wave.

[0053] The principle and the present embodiment constructed based on the principle are described in detail below.

[0054] <Relationship between blood pressure P and blood vessel cross-sectional area A>

[0055] According to previous research (Benjamin Gavish: Arterial stiffness: Going a step beyond, American Journal of Hypertension (2016)), it is known that the pressure P [mmHg] of the blood vessels and the cross-sectional area A [cm 2 ]for

[0056] [Formula 1]

[0057] P=α+γe βA

[0058] Here, α is a deviation coefficient related to the characteristics of the blood vessels, β is a value indicating the strength of the distortion mode of the pulse wave (related to the increase in the volume pulse wave), and γ is a weight coefficient that relates α to β. α, β, and γ are constants, but they vary according to the characteristics of the blood vessels. Regarding the characteristics of the blood vessels, especially arteriosclerosis depends on age, and therefore has age dependence as shown in Table 1. It is believed that even if the main reason is other than age, the characteristics of the blood vessels will change. Even if the age is the same, there are large individual differences. Even for the same individual, it will change according to various conditions such as changes within a day, exercise, and psychological stress. In the following, formula (1) is referred to as the basic function. That is, the basic function includes a deviation coefficient α that depends on the age of the organism, and can be called a function that represents the relationship between the blood pressure P and the cross-sectional area A of the blood vessel of the organism.

[0059] [Table 1]

[0060] Table 1 Average values ​​of parameters α, β, and γ of basic functions

[0061] Young people (age 28-31) Seniors (age 71-78) α[mmHg] 53 43 <![CDATA[β[cm -2 ]]]> 1.43 3.42 γ[mmHg] 1.07 1.05

[0062] <Relationship between the signal value I of the video pulse wave and the cross-sectional area A of the blood vessel>

[0063] The pulse wave obtained from the video signal (Video Plethysmogram: VPG) uses the property of hemoglobin contained in the blood to absorb green light well, etc., to obtain the pulsation information in the blood vessels from the video signal obtained by photographing the skin. The amount of hemoglobin in the arterial blood vessels increases and decreases periodically with the beating of the heart, and is proportional to the volume of the arterial blood vessels. Since the amount of hemoglobin is the main cause of the generation of the video pulse wave, it is believed that the video pulse wave is also proportional to the volume of the arterial blood vessels (blood vessel cross-sectional area A). This property is the same in infrared light. Therefore, the relationship between the signal value I of the video pulse wave and the blood vessel cross-sectional area A is as follows,

[0064] [Formula 2]

[0065] I=KβA (2)

[0066] In this way, it can be expressed using the proportionality constant Kβ (K is a constant including various factors that affect the pulse wave signal (such as the lighting environment during measurement)). By transforming equation (2) and substituting it into equation (1), it can be transformed into

[0067] [Formula 3]

[0068]

[0069] <Relationship between blood pressure P and pulse wave amplitude J>

[0070] If we take the natural logarithm of formula (3), we get

[0071] [Formula 4]

[0072]

[0073] If the relationship of formula (4) is shown in the figure, then Figure 4 As shown by the thin solid line.

[0074] If we differentiate equation (4) by P, we get

[0075] [Formula 5]

[0076]

[0077] The differential of the video pulse wave signal value based on blood pressure can also be approximated by the ratio of the difference in the pulse wave signal value between the systolic period and the diastolic period (pulse wave amplitude) to the difference in the blood pressure between the systolic period and the diastolic period (pulse pressure). That is, if the systolic blood pressure (maximum blood pressure) of each beat is set to P S , set the diastolic blood pressure (minimum blood pressure) as P D , the pressure gradient between systole and diastole (pulse pressure) is set to D = P S ~P D , and further, the pulse wave signal values ​​of the systolic and diastolic periods corresponding to the blood pressure are set to I S ,I D , the difference between the systolic period and the diastolic period of the pulse wave signal (the difference between the maximum and minimum values ​​in the pulsation, that is, the pulse wave amplitude) is set to J = I S -I D , it can be approximated as

[0078] [Formula 6]

[0079]

[0080] Based on the assumption that equation (5) and equation (6) are equal, we get

[0081] [Formula 7]

[0082]

[0083] It can be assumed that the equation (7) is independent of the height of the measurement site and holds true between the blood pressure P and the pulse wave amplitude J at any site.

[0084] <Systolic blood pressure P S Relationship with pulse wave amplitude J>

[0085] On the other hand, if the pulse pressure D = P S -P D Transform and substitute into equation (3), then we get equation (8) and equation (9).

[0086] [Formula 8]

[0087]

[0088] [Formula 9]

[0089]

[0090] If the difference between the systolic period (maximum value) and the diastolic period (minimum value) of the pulse wave signal, i.e., the pulse wave amplitude J=I S -I D , divide equation (9) by equation (8), and we get

[0091] [Formula 10]

[0092]

[0093] If it is deformed, it is

[0094] [Formula 11]

[0095]

[0096] Here, the change in the cross-sectional area of ​​the blood vessel is small, so when it is assumed that the cross-sectional area of ​​the blood vessel can be approximated by equation (12),

[0097] [Formula 12]

[0098]

[0099] According to formula (12), we can get

[0100] [Formula 13]

[0101]

[0102] Equation (13) also does not depend on the position. The systolic blood pressure P at any position is S holds true between the pulse wave amplitude J measured at this position.

[0103] According to the above equations (7) and (13), it can be confirmed that there is a certain relationship between the blood pressure P and the pulse wave amplitude J. However, J can be detected from the video signal, but K and D are unknown.

[0104] Therefore, consider the case where there is a height difference in the measurement position. For simplicity, the equation is expanded for the systolic period. If equation (13) is divided into high and low positions, and the subscripts H and L are added to distinguish them, then equations (14) and (15) are established.

[0105] [Formula 14]

[0106]

[0107] [Formula 15]

[0108]

[0109] At this time, if we assume that the pulse pressure remains unchanged at both high and low altitudes, that is, D H =D L , then since equation (14) and equation (15) are equal, we can get equation (16),

[0110] [Formula 16]

[0111] (P SH -α)J H =(P SL -α)J L (16)

[0112] D and K are eliminated. The difference in local systolic blood pressure between the lower and upper hands is set as formula (17),

[0113] [Formula 17]

[0114] ΔP=P SL -P SH (17)

[0115] If equation (16) is transformed, it becomes equation (18).

[0116] [Formula 18]

[0117] (P SL -ΔP-α)J H =(P SL -α)J L (18)

[0118] Furthermore, in formula (19),

[0119] [Formula 19]

[0120]

[0121] If equation (18) is transformed, we get equation (20).

[0122] [Formula 20]

[0123]

[0124] The ratio information of the low part to the high part of the amplitude of the pulse wave signal (the difference between the maximum value and the minimum value in the pulse) in formula (20) is R=J L / J H Therefore, if the difference ΔP and α between the local systolic blood pressure at the high and low points are known in addition to R, the absolute value P of the systolic blood pressure at the low point can be calculated according to formula (20): SL [mmHg].

[0125] ΔP is the pressure gradient between the high and low points. Therefore, if the vertical distance is known, since the density of blood is roughly equal to that of water, it is assumed that the water column pressure close to this part (0.735 mmHg per 1 cm) is obtained. Therefore, assuming q = 0.735 [mmHg / cm] and the vertical distance is h [cm], the equation (21) is:

[0126] [Formula 21]

[0127] ΔP=qh (21)

[0128] Therefore, equation (20) can be standardized as equation (22).

[0129] [Formula 22]

[0130]

[0131] Hereinafter, equation (22) is referred to as a blood pressure function. That is, it can be said that the blood pressure function is derived from the above-mentioned basic function, and is a function that uses the comparison value information (amplitude ratio information) as a variable and further includes a deviation coefficient α.

[0132] Furthermore, the lower diastolic blood pressure P can also be derived similarly using the above equations (14) to (22). DL , high systolic blood pressure P SH , high diastolic blood pressure P DH In addition, the vertical distance h can be estimated based on the video alone, using the length of the hand or face captured in the video as a reference.

[0133] In addition, although q is calculated based on the density of water, the accuracy is improved if q is calculated based on the density of blood. A method for further improving the accuracy will be described later.

[0134] Figure 5 This is a diagram illustrating the relationship of equation (22). If we focus on the slope of the straight line that linearly approximates the curve, the slope is gentler at high points than at low points. This is because the elasticity of the blood vessels changes with respect to the intravascular pressure.

[0135] Thus, it is considered that by using the amplitudes of the pulse wave signals at high and low points, the ratio information R=J of the low point to the high point based on the amplitude (difference between the maximum value and the minimum value in the pulse) of the video pulse wave signal which can be directly measured is obtained. L / J H , the difference between the high and low local systolic blood pressure ΔP = qh, the value of the deviation coefficient α, the absolute value of the low systolic blood pressure, i.e., P, can be calculated with fewer steps SL [mmHg] In other words, by directly substituting the value detected from the video signal into equation (22), the absolute value blood pressure P having the original unit [mmHg] of the measured amount can be easily estimated without applying a regression equation.

[0136] The blood pressure estimation device 1 of the embodiment is based on the above principle and calculates the ratio information R=J of the pulse wave amplitude at the low point to the high point based on the signal value of the video pulse wave (video pulse wave signal) representing the time change of the brightness value of the video signal. L / J H The following describes the processing of the blood pressure estimation device 1 by listing the components to sequentially describe the processing of detecting the measurement position from the video signal, the processing of detecting the pulse wave information from the video signal, and the processing of estimating the blood pressure based on the detected pulse wave information.

[0137] [3. Functional structure]

[0138] Reference Figure 2 , an example of the functional configuration of the blood pressure estimation device 1 according to the embodiment will be described. Figure 2 In the example, the Figure 1 A portion of the devices, cables, etc. in the information processing device 3 shown. Figure 2 As shown in the example, the functions of the blood pressure estimation device 1 are mainly realized by the information processing device 3. Furthermore, the information processing device 3 is functionally configured to include a processing unit 31 and a storage unit 32.

[0139] [3-1. Processing unit]

[0140] The processing unit 31 detects the vertical distances between the upper and lower measurement positions of the subject (the upper measurement position of the subject corresponds to the first position or the second position of the biological body, and the lower measurement position of the subject corresponds to the second position or the first position of the biological body) from the video information (video signal) of the specified part of the subject, detects the video pulse wave signal (pulse wave information) at each position, and estimates the blood pressure based on the comparison value information of the pulse wave amplitude of each detected video pulse wave signal (the video pulse wave signal at the upper measurement position corresponds to the first pulse wave information at the first position of the biological body or the second pulse wave information at the second position, and the video pulse wave signal at the lower measurement position corresponds to the first pulse wave information at the second position of the biological body or the second pulse wave information at the first position).

[0141] [3-2. Functions of the processing unit]

[0142] The processing unit 31 is a functional part where the CPU 3A performs calculations, and each function is constituted as a separate program. Figure 2 As shown, the processing unit 31 includes a video signal acquisition unit 311 , a measurement region detection unit 312 , a pulse wave information detection unit 313 , and a blood pressure estimation unit 314 .

[0143] <Video Signal Acquisition Section>

[0144] The video signal acquisition unit 311 acquires a video signal representing a video of a predetermined part of the body of the subject through the video acquisition device 2. The video signal acquisition unit 311 outputs the acquired video signal of the subject to the measurement area detection unit 312 and the pulse wave information detection unit 313. In addition, the video signal acquisition unit 311 may acquire the video signal by reading the video signal information stored in the video information storage unit 321 of the storage unit 32 described later. In addition, the video signal acquisition unit 311 may acquire the video signal stored in an external communication terminal or an external storage device by receiving data including the video signal through a network or an electric line.

[0145] <Measurement Area Detection Section>

[0146] The measurement area detection unit 312 detects an area of ​​a predetermined part of the subject included in the video of the video signal obtained by the video acquisition device 2. In the embodiment, the face area, the palm area, the foot, the sole area, and the heart area (reference position) are detected as needed. As a method for detecting each measurement part, for example, a method based on pattern matching or a method using a discriminator can be used, and the discriminator is obtained by learning using multiple sample images of the face and hands of the person. In addition, the face of the subject can be pre-registered in the ROM, and face recognition can be performed after the subject is detected, thereby identifying a specific face. In addition, with respect to the heart area, a position located within a certain range from the face area can also be identified as the heart area.

[0147] Furthermore, the measurement area detection unit 312 also detects the skin area of ​​a specific part. In the case of automatically extracting the skin area based on the color information in the video, the skin area of ​​the subject can be extracted by extracting the area representing the skin color from the video. Specifically, the measurement area detection unit 312 extracts all coordinates (pixel coordinates) representing the color (brightness value) corresponding to the skin color in the two-dimensional coordinates of the video, and extracts the area in which the pixels of the continuous coordinates in the extracted coordinates are aggregated as the skin area. In this way, the measurement area detection unit 312 can extract the skin area corresponding to the specific part of the subject's body by extracting the area in which the pixels of the continuous coordinates are aggregated.

[0148] The measurement area detection unit 312 may also perform tracking processing on the area of ​​the predetermined part as the tracking area. As an example of implementation, when only one hand is used at two positions, high and low, at intervals, tracking processing is performed when the hand is moved from the low position (first position) to the high position (second position). The tracking processing is, for example, searching the current frame image for an area where the feature quantity of the image in the tracking area in the previous frame image has the highest similarity with the feature quantity of the image in the tracking candidate area in the current frame image (this area becomes the tracking area in the original frame image).

[0149] The measurement area detection unit 312 executes the above-described detection process on each frame constituting the video, and sequentially sends the coordinates of the area in each frame to the pulse wave information detection unit 313 .

[0150] The predetermined part may be any part as long as it has a height difference in the vertical direction, for example, a hand and face placed near the heart, the forehead and jaw of the face, the right hand and the left hand with a height difference, the right foot and the left foot, etc.

[0151] Alternatively, one of the predetermined parts may be moved to a higher or lower position during measurement. For example, the predetermined part may be measured by placing both hands at the same height at first, fixing one hand at that position, and then moving the other hand in the vertical direction to measure.

[0152] In addition, when, for example, the face is selected as the predetermined part, the predetermined part of the face can be measured while the user is sitting first, and then the user can stand up and move the face in the vertical direction to measure the predetermined part.

[0153] In this embodiment, the palm area uses both hands, the left hand is set at a low position (L: first position), and the right hand is set at a high position (H: second position). If the two palm areas are set as predetermined positions, the possibility that the endogenous elements of the blood vessels from the heart to the predetermined positions are roughly the same is high, so the endogenous influence of the blood vessels is small, and higher measurement accuracy can be expected, which is preferred.

[0154] <Pulse Wave Information Detection Section>

[0155] The pulse wave information detection unit (first pulse wave information detection unit, second pulse wave information detection unit) 313 detects a video pulse wave signal indicating a temporal change in the brightness value of each measurement position based on the video signal of the skin area of ​​the specific part of the subject detected by the measurement area detection unit 312. In the embodiment, the video pulse wave signal (first pulse wave information) is detected from the video signal obtained at a low position, and the video pulse wave signal (second pulse wave information) is detected from the video signal obtained at a high position. The pulse wave information detection unit 313 outputs the detected pulse wave information signal (pulse wave information) to the blood pressure estimation unit 314.

[0156] For example, in the case of detecting the brightness value of green light, which is usually used in the video pulse wave, the pulse wave information detection unit 313 applies a green filter to the skin area of ​​each frame of the video, or detects the brightness value of green light using the brightness value of "G (green)". Then, the pulse wave information detection unit 313 calculates the average value of the brightness value of green light for each frame, and detects the video pulse wave as a time-varying curve. The pulse wave information detection unit 313 may also smooth the image before detecting the brightness value of green light based on the video signal, and remove artificial pulse noise generated in the camera itself as the video acquisition device 2. In addition, when using infrared light, the brightness value of the infrared light obtained may be used directly.

[0157] exist Figure 6 (a) Figure 6 (b) shows the video pulse wave signal detected in this embodiment. Figure 6 (a) shows the video pulse wave signal I of the palm area at a high position H , Figure 6 (b) shows the video pulse wave signal I of the lower palm area L .Depend on Figure 6 (a) Figure 6 (b) shows that the video pulse wave signal I at high and low H ,I L Significant differences were observed in the pulse wave amplitude J at high H Greater than the pulse wave amplitude J at the lower part L characteristics.

[0158] <Blood Pressure Estimation Unit>

[0159] The blood pressure estimation unit 314 estimates the absolute value of the blood pressure P based on equation (22). In the embodiment, it is necessary to obtain the vertical difference h, the ratio R of the pulse wave amplitude at the lower part to the pulse wave amplitude at the higher part, and the deviation coefficient α. The vertical difference h can be predetermined. V When it is obtained from a video, for example, the size h of the face region is calculated by the blood pressure estimation unit 314 based on the coordinates of the measurement region input from the measurement region detection unit 312. F Based on this size, the vertical difference between the center of gravity at the high point and the center of gravity at the low point (distance h V ). For the ratio of the pulse wave amplitude at the lower part to the higher part, the pulse wave amplitude J is calculated based on the pulse wave information (first pulse wave information and second pulse wave information) of the palm area at the higher part and the lower part input from the pulse wave information detection unit 313. L , J H , calculate the comparison value information of the low amplitude relative to the high amplitude of the video pulse wave signal, that is, the ratio (amplitude ratio information) R.

[0160] R can also be calculated by cutting out the high and low video pulse wave signals for each beat, respectively finding the difference between the maximum value and the minimum value in the beat, and finding the ratio thereof. However, since the video pulse wave has much noise, the power spectrum of the high and low video pulse wave signals can be temporarily found in time series, respectively, and the square root of the largest frequency component is found within the frequency range related to the pulse wave, and the ratio thereof is found to perform calculation.

[0161] The coefficient of variation α is obtained by measuring a subject using the literature values ​​shown in Table 1 or a cuff-type blood pressure monitor or the like, and is acquired from the storage unit 32 described later.

[0162] The blood pressure estimation unit 314 substitutes the above-calculated and acquired vertical difference h, the ratio R of the pulse wave amplitude at the lower part to the higher part, and the deviation coefficient α into equation (22) to estimate the absolute value of the blood pressure.

[0163] [3-3. Storage unit]

[0164] The storage unit 32 uses the memory 3B to store various data through a file system or a database system. The storage unit 32 stores programs in advance, and by causing the CPU 3A to execute the programs, the CPU 3A performs the functions of the functional elements of the processing unit 31. In addition, these programs are collectively referred to as the program of the present invention (the above-mentioned blood pressure estimation program). In addition, as the storage unit 32, it is also possible to use Figure 1 The storage unit 3C is shown.

[0165] [3-4. Functions of the storage unit]

[0166] like Figure 2 As shown, the storage unit 32 includes a video information storage unit 321 , a measurement result storage unit 322 , an estimation result storage unit 323 , and a reference information storage unit 324 .

[0167] <Video Information Storage Unit>

[0168] The video information storage unit 321 stores video signals. Specifically, the video information storage unit 321 stores video signals of the subject person acquired by the video acquisition device 2. For example, the video information storage unit 321 stores video signals representing a video including a predetermined part of the subject person. The video information storage unit 321 stores the video signals in association with the time information of the subject person.

[0169] <Measurement Result Storage Section>

[0170] The measurement result storage unit 322 stores the size h of the face region calculated by the blood pressure estimation unit 314. F , the vertical distance h between the center of gravity of the upper and lower palm areas V , the pulse wave amplitude J of the pulse wave information signal L , J H , and the comparison value information of the low point relative to the high point of the pulse wave amplitude, that is, the ratio (amplitude ratio information) R. At this time, the measurement result storage unit 322 stores the measurement information that associates the estimated date and time with the measurement result for each subject. V In the case of F .

[0171] <Estimation Result Storage Section>

[0172] The estimated result storage unit 323 stores the estimated blood pressure value estimated by the blood pressure estimation unit 314. At this time, the estimated result storage unit 323 stores measurement information in which the estimated date and time are associated with the measurement result for each subject.

[0173] <Reference Information Storage Unit>

[0174] The reference information storage unit 324 stores reference information referred to by the blood pressure estimation unit 314 in the estimation process as the deviation coefficient α and the water column pressure q. The reference information may be a document value or may be updated by the subject periodically measuring with a cuff-type blood pressure monitor or the like.

[0175] [4. Flowchart]

[0176] Figure 3 2 is a flowchart illustrating the content of the above-mentioned processing performed in the blood pressure estimation device 1 .

[0177] First, a subject person is photographed by the video acquisition device 2 to acquire a video signal, and the acquired video signal is input to the video signal acquisition unit 311 of the information processing device 3 (step S1).

[0178] Next, the measurement area detection unit 312 of the information processing device 3 receives the video signal obtained in step S1 from the video signal acquisition unit 311, and detects the face area, lower palm area, soles of feet, etc. (first position) of the subject (step S2). Next, the pulse wave information detection unit 313 receives the video signal obtained in step S1 and the first position information detected in step S2, and detects the video pulse wave signal (first pulse wave information) at the first position based on them (step S3).

[0179] Similarly, the measurement area detection unit 312 of the information processing device 3 detects the upper palm area, sole of the foot, etc. (second position) of the subject based on the video signal obtained in step S1 (step S4). Next, the pulse wave information detection unit 313 of the information processing device 3 receives the video signal obtained in step S1 and the second position information detected by the measurement area detection unit 312 in step S4, and detects the video pulse wave signal (second pulse wave information) at the second position based on them (step S5).

[0180] Next, the blood pressure estimation unit 314 of the information processing device 3 calculates the distance h between the two positions based on the first position information and the second position information detected in steps S2 and S4. V (Step S6) In addition, if the vertical distance h is known in advance, V In the case of V The information storage unit 32 reads the distance h V Next, the blood pressure estimation unit 314 calculates the comparison value information (amplitude ratio information) of the pulse wave amplitude based on the first pulse wave information and the second pulse wave information detected in steps S3 and S5 (step S7).

[0181] Furthermore, the blood pressure estimation unit 314 of the information processing device 3 obtains the necessary parameters q and α from the reference information storage unit 324 (step S8), and estimates the blood pressure based on equation (22) (step S9). The blood pressure estimation unit 314 outputs the estimation result to the estimation result storage unit 323 and the output device 4 (step S10).

[0182] In addition, the processing of steps S2 to S5 may be performed in order from high to low, the order of each step may be reversed, or the processing may be performed simultaneously.

[0183] [5. Results of this embodiment]

[0184] In the blood pressure estimation device 1 of this embodiment, the left hand is set to a low position (L: first position), and the right hand is set to a high position (H: second position), and the video acquisition device 2 is used to shoot, and the processing unit 31 estimates the absolute value of the blood pressure P based on formula (22).

[0185] While the blood pressure P was obtained based on the video pulse wave by photographing, the blood pressure was measured using a continuous sphygmomanometer (Finometer Midi; Finapres Medical Systems) as a true value for comparing the accuracy of the blood pressure, and comparison was performed.

[0186] The measurement was performed for 60 seconds. During the measurement, the foot was kicked with Aeromoke (registered trademark) to give blood pressure changes. The video pulse wave signal obtained at the left hand low and the right hand high is as follows: Figure 6 (a) Figure 6 as shown in (b).

[0187] The height difference between the right hand and the left hand is h = 50 cm, and the deviation coefficient α uses the literature values ​​α = 40 mmHg and q = 0.735 [mmHg / cm] (blood density = water density) in Table 1. The results of calculating the blood pressure P based on formula (22) are shown in Table 2 as the correlation coefficient and root mean square error RMSE (root mean squared error) with the blood pressure of the continuous sphygmomanometer (hereinafter referred to as the true blood pressure).

[0188] [Table 2]

[0189] Table 2 Correlation and error of blood pressure (results of estimating the lower systolic blood pressure)

[0190] Correlation coefficient RMSE [mmHg] Target person 1 0.57 31.7 Target person 2 0.61 54.6 Target person 3 0.53 51.2 Target person 4 0.89 7.15 Target person 5 0.61 68.8

[0191] It was observed that the estimated blood pressure values ​​were highly correlated with the measured values, but there were subjects with larger RMSE and subjects with smaller RMSE.

[0192] In this embodiment, the coefficient of variation α uses the literature value, but it is considered that the coefficient of variation α varies depending on individual differences and the conditions of the subjects. If each subject appropriately changes the coefficient of variation α to different values, the RMSE is improved compared to Table 2, and the optimal value is less than 10 mmHg in most subjects.

[0193] The above demonstrates that the blood pressure estimation device 1 of the present embodiment can estimate the blood pressure, and shows the possibility that the blood pressure can be estimated with high accuracy if the value of the variation coefficient α is accurately determined.

[0194] [6. Function and Effect]

[0195] As described above, the blood pressure estimation device 1 of the embodiment can easily estimate the blood pressure based on the measurement positions of the high and low parts of the specific part of the subject detected by the measurement area detection unit 312 and the ratio information of the pulse wave amplitude of the pulse wave information of the high and low parts detected by the pulse wave information detection unit 313, which are calculated or detected based on the video signal acquired by the video acquisition device 2. In addition, if time-related information such as phase difference is not required, the blood pressure estimation device 1 of the embodiment does not apply the regression equation to the value that can be detected only from the video signal, and can estimate the blood pressure directly, so that the blood pressure can be estimated with fewer steps.

[0196] In addition, in the above-mentioned blood pressure estimation, video pulse waves are used in the pulse wave measurement, but formula (22) is not limited to signals from the video. As long as the pulse wave signals at the high and low points of the biological body can be obtained, the blood pressure P can be estimated. Therefore, it is also possible to measure a specified position with a height difference by using a device for detecting pulse waves such as a photoelectric pulse wave meter, thereby estimating the blood pressure.

[0197] [7. Modifications]

[0198] [7-1. Modification of Blood Pressure Estimation]

[0199] In the above-described embodiment, the case where the blood pressure is estimated based on the pulse wave amplitude ratio information of the video pulse wave signal is exemplified, but the blood pressure may be estimated based on the pulse wave amplitude difference information of the video pulse wave signal.

[0200] If equation (7) is considered for the low position (L) and the high position (H), the systolic blood pressure P in the low position is SL as follows.

[0201] [Formula 23]

[0202]

[0203] In addition, the systolic blood pressure P at high altitude SH as follows.

[0204] [Equation 24]

[0205]

[0206] Furthermore, if equation (24) is subtracted from equation (23), the equation (25) is obtained.

[0207] [Formula 25]

[0208] P SL -P SH =ΔP≈KD(J L -1 -J H -1 ) (25)

[0209] Therefore, we get formula (26).

[0210] [Equation 26]

[0211]

[0212] Substituting equation (26) into equation (23), we get equation (27):

[0213] [Formula 27]

[0214]

[0215] According to formula (19),

[0216]

[0217] Therefore, equation (27) becomes equation (28),

[0218] [Equation 28]

[0219]

[0220] This equation (28) yields the same result as equation (20).

[0221] If we assume that ΔP=qh holds and substitute it into equation (26), we get equation (29).

[0222] [Equation 29]

[0223]

[0224] The right side of equation (29) can be measured, so KD is known. If this value is expressed as G=KD, then according to equation (7), equation (30) is obtained.

[0225] [Formula 30]

[0226]

[0227] G in formula (30) is the difference information of the pulse wave amplitude J of the video pulse wave signal, which can be directly measured. Hereinafter, formula (30) is also referred to as a blood pressure function. That is, it can be said that the blood pressure function is derived from the above-mentioned basic function, and is a function that uses the comparison value information (difference information) as a variable and also includes a deviation coefficient α.

[0228] In addition, the processing of the above modification example is equivalent to Figure 3 In the method using the difference information, the processing of steps S2 to S5 may be performed in order from high to low, the order of each step may be reversed, or the steps may be performed simultaneously.

[0229] [7-2. Modification using parameter mapping]

[0230] In the embodiment and the modified example, the blood pressure is estimated by calculation based on equation (22) and equation (30), but the blood pressure may be estimated using information pre-stored in the storage unit 32. That is, in this case, when the height difference h of the detection position is fixed to a predetermined position, for example, the hand is fixed, qh in equation (22) becomes a constant, so that Figure 7 As shown, in the reference information storage unit 324, the value P' of qh / (1 to R) calculated by combining the constant qh and a plurality of patterns of R is stored in advance as a map M1, and the deviation coefficient α corresponding to the subject is stored in advance as a map M2. On the other hand, when R is detected from the pulse wave signal, P' and α corresponding to the detected R can be read out to estimate the blood pressure based on the simple calculation formula P = P' + α.

[0231] Similarly, in the storage unit 32, a combination of J and G=KD may be stored as a mapping M1′, and a deviation coefficient α corresponding to the subject may be stored as a mapping M2. In contrast, when J is detected from the pulse wave signal, P″ corresponding to the detected J may be read out, and the blood pressure may be estimated based on a simple calculation formula P=P″+α. In addition, a plurality of mappings may be prepared for each different α.

[0232] [7-3. Variation Coefficient Modification Example]

[0233] In the above embodiment, the variation coefficient α used the literature value in the range of 43 to 53 mmHg shown in Table 1, but as mentioned above, it is considered to vary depending on the individual and the situation. Therefore, the method of correcting α is described below.

[0234] First, with the hand at the same height as the heart (reference position), the true value of blood pressure P is measured using a sphygmomanometer. 0 . Measure J based on the video at this time 0 If α is taken as an unknown number, P 0 and J 0 Substituting into equation (30), we get equation (31).

[0235] [Equation 31]

[0236]

[0237] If α determined as in equation (31) is set to α * , then any blood pressure can be estimated as shown in formula (32).

[0238] [Formula 32]

[0239]

[0240] Based on formula (32), the following four values ​​need to be measured:

[0241] i) J at the lower position measured from the video L

[0242] ii) J at the higher point measured from the video, which is hcm higher than the lower point H

[0243] iii) J at the position of the heart measured from the video 0

[0244] iv) The true value P of the blood pressure corresponding to iii) measured by the sphygmomanometer 0 .

[0245] When using equation (22), it is necessary to calculate the pulse wave amplitude J of the hand at two locations where there is a height difference of hcm. L and J H On the other hand, in the method based on formula (32), if J L and J H Substituting into equation (29) to determine G = KD, J 0 and P 0 Substitute into equation (31) to determine α * , then the blood pressure P can be estimated more easily based on the pulse wave amplitude J using formula (32).

[0246] In addition, in J L In the case of the heart, J 0 =J L In this case, you can also use J L To replace J 0 .

[0247] In addition, α * Since the value α may change depending on the state of the subject, it is preferable to periodically calculate and update the value stored in the reference information storage unit 324. The processing unit 31 further includes a variation coefficient determination unit 315 for determining the variation coefficient α. * processing.

[0248] In the above-mentioned modification, the position of the heart measured from the video is detected by the measurement region detection unit 312. Then, for each subject, the value measured as a premise of using the formula (32) and the J at the position of the heart measured from the video are calculated. 0 and J measured by a sphygmomanometer 0 The corresponding true value of blood pressure P 0 The measurement result storage unit 322 stores the coefficient of variation α calculated based on equation (32) for each subject. * Stored in the reference information storage unit 324.

[0249] [7-4. Modification example using each person's correct q]

[0250] In the above method, for q, the density of blood is assumed to be approximately equal to the density of water and the density of water is used. However, if the density of blood is used, the accuracy is further improved. However, the density of blood varies from person to person, and if the density of blood of each person can be easily calculated, the accuracy can be improved.

[0251] A method for simply obtaining the density of blood is described below.

[0252] First, the subject's predetermined part is placed at a low position, and the blood pressure P at the predetermined part is measured. L Next, in this state, the specified part is raised to a height of a vertical distance h, and the blood pressure P at the specified part is measured. H .

[0253] At this time, referring to equations (17) and (21), the blood pressure P at the lower part is L With high blood pressure P H The difference is expressed by formula (33).

[0254] [Formula 33]

[0255] ΔP=qh=P L -P H (33)

[0256] By using the obtained local blood pressure ΔP in equation (22), it can be used as a value unique to the subject, and the blood pressure can be estimated with high accuracy.

[0257] The blood pressure measurement used at this time can use a well-known blood pressure meter such as a cuff-type blood pressure meter and a continuous blood pressure meter. In addition, when using a continuous blood pressure meter, the continuous blood pressure values ​​at low and high points obtained within a specified time can be averaged to find the difference between the low average blood pressure and the high average blood pressure.

[0258] Furthermore, as mentioned above using the parameter map, by setting the relationship between the local blood pressure ΔP and the plurality of vertical distances h in advance as a map, the blood pressure can be estimated simply and accurately.

[0259] [7-5. Modification of parameter calculation]

[0260] In addition, a method of using a large amount of data to find the unknown parameters of equation (30) has been proposed. Assuming that equation (30) always holds, by giving a certain blood pressure change, K (≥2) different blood pressures P measured by a sphygmomanometer are obtained. K and pulse wave amplitude J k (k = 1, 2, ... K). At this time, the estimated values ​​of the unknown parameters G (with cap) and α (with cap) in equation (32) can be obtained by the least square method. That is, in equation (34),

[0261] [Equation 34]

[0262]

[0263] At this time, G (with hat) and α (with hat) are used as the solution to the normal equation that minimizes the norm of the residual of the model equation (35), which becomes equation (37).

[0264] [Formula 35]

[0265] y=Ax+ε (35)

[0266] [Equation 36]

[0267] ε T ε=(y-Ax) T (y-Ax) (36)

[0268] [Equation 37]

[0269]

[0270] The minimum number of data required at this time is the following 4:

[0271] i) Two different pulse wave amplitudes J measured from the video 1 , J 2

[0272] ii) Two different blood pressures P measured by a sphygmomanometer 1 , P 2

[0273] However, it is necessary to apply some kind of blood pressure change so that the two blood pressures differ.

[0274] If we further generalize formula (30), then for different blood pressures P k and pulse wave amplitude J k (k=1,2,···K), if it is assumed that equation (38) holds,

[0275] [Equation 38]

[0276]

[0277] Then consider expanding formula (36) to a model with n (≤K) times (an extremely common multiple regression model)

[0278] [Equation 39]

[0279] y=Ax+ε (39)

[0280] Here, it is formula (40).

[0281] [Formula 40]

[0282]

[0283] The estimated parameters are as shown in formula (41).

[0284] [Formula 41]

[0285] x=(A T A) -1 A T y (41)

[0286] The minimum number of data required at this time is 2n as follows:

[0287] i) n different pulse wave amplitudes J measured from the video k (k=1, 2, ... n)

[0288] ii) n different blood pressures P measured by a sphygmomanometer k (k=1, 2, ... n)

[0289] In the above-mentioned multiple modified examples, the same effects as those of the embodiment are achieved except that the calculated values ​​are different.

[0290] [7-6. Modification Example Using Correction Coefficients of Each Part]

[0291] In the method of the present invention, if different predetermined parts of the living body are measured at the same height, equal values ​​of pulse wave amplitude J are calculated. However, for example, when the right and left hands are placed at the same height and their respective pulse wave amplitudes J are measured, some deviations are known.

[0292] This is believed to be because the characteristics of the blood vessels in the right and left hands are not necessarily exactly the same. Of course, if the blood vessel characteristics are significantly different in the hands, face, etc., the pulse wave amplitudes J will not be equal even if measured at the same height. If the pulse wave amplitude J is different in each part, it will naturally affect the estimation of blood pressure. Therefore, it is necessary to perform correction for each part.

[0293] The following describes a method of correcting each part by taking the case where both hands are used and the right hand is set at a high position and the left hand is set at a low position as an example.

[0294] Assume that the pulse wave amplitudes ΔJ of the right and left hands measured at the same height are left , ΔJ right different.

[0295] At this time, if the left and right pulse wave amplitude ratios (pulse wave amplitude ratios for each part) R are introduced LR , then it becomes equation (42).

[0296] [Formula 42]

[0297] R LR =ΔJ left / ΔJ right (42)

[0298] If R LR As a constant, the pulse wave amplitude ΔJ in the right hand can be corrected right The pulse wave amplitude of the left hand ΔJ left The deviation (difference) originally existed between them. Formula (42) can be transformed into Formula (43).

[0299] [Formula 43]

[0300] ΔJ left =R LR ΔJ right (43)

[0301] Therefore, according to formula (22), the ratio information of the low place to the high place R = J L / J H , and equation (42), the blood pressure estimation equation that eliminates the influence of the left and right differences in pulse wave amplitude (the difference in each part) is obtained as equation (44).

[0302] [Formula 44]

[0303]

[0304] Therefore, R LR It can also be said that it is a coefficient (correction coefficient) for correcting the pulse wave information between different parts.

[0305] In this way, the left and right pulse wave amplitude ratio (the pulse wave amplitude ratio for each part) R can be easily measured. LR .

[0306] In the case of the right hand and the left hand, R is obtained by fixing both hands at the same height and measuring the pulse wave amplitude of each hand using a video pulse wave or a photoelectric pulse wave. LR In order to further improve R LR The accuracy can be obtained by performing this measurement multiple times and finding R LR to achieve the average value.

[0307] By using the pulse wave amplitude ratio R of each part, which is easily obtained LR By correcting the pulse wave amplitude of each part, blood pressure can be estimated with higher accuracy. In addition, by associating multiple parts using the pulse wave amplitude ratio of each part, the pulse wave amplitude of other parts can be corrected by measuring only one part, which can reduce the burden of measurement.

[0308] [8. Others]

[0309] In the embodiment, as the imaging element, color images or monochrome images are mainly exemplified, but not limited to these. As described above, since the signal value I of the video pulse wave is proportional to the blood vessel cross-sectional area A, it is sufficient as long as information reflecting this relationship can be obtained. Therefore, the imaging element may use an infrared image or an ultrasonic image.

[0310] In the embodiment, the size h of the face area is calculated. F , and based on this size, calculate the difference in the vertical direction between the center of gravity of the high and low palm areas (distance h V ), but the size of a part other than the face area can also be calculated. In addition, the difference (distance h) between the high and low positions in the vertical direction can be calculated based on the tip of the longest finger of the hand instead of the palm area. V The benchmark can also be a benchmark other than a living organism.

[0311] In the embodiment, it is disclosed that the blood pressure is estimated without using the information related to time such as phase information (pulse wave propagation velocity), but in order to improve the accuracy, it does not prevent the use of the above information. The blood pressure information obtained in the embodiment can also be corrected by using the blood pressure estimated from the pulse wave propagation velocity, parameters related to the pulse wave propagation velocity, etc. In addition, conversely, the blood pressure estimated from the pulse wave propagation velocity can also be corrected by using the parameters and blood pressure values ​​of the embodiment.

[0312] Description of symbols

[0313] 1 Blood pressure estimation device

[0314] 2 Video acquisition device

[0315] 2A Lighting

[0316] 3 Information processing device

[0317] 3A CPU

[0318] 3B memory

[0319] 3C Storage Department

[0320] 3D Interface (IF)

[0321] 3F Recording medium

[0322] 4 Output Devices

[0323] 31 Processing Department

[0324] 311 Video signal acquisition unit

[0325] 312 Measurement area detection unit

[0326] 313 Pulse wave information detection unit

[0327] 314 Blood Pressure Estimation Department

[0328] 315 Deviation coefficient determination unit

[0329] 32 Storage

[0330] 321 Video Information Storage Department

[0331] 322 Measurement result detection unit

[0332] 323 Estimation result storage unit

[0333] 324 Reference information storage unit< / cpu>

Claims

1. A blood pressure estimation device, characterized in that: The blood pressure estimation device comprises: a first pulse wave information detecting unit configured to detect first pulse wave information at a first position of the living body; a second pulse wave information detection unit configured to detect second pulse wave information at a second position of the living body that is spaced apart from the first position in a vertical direction; as well as A blood pressure estimation unit estimates the blood pressure of the biological body based on pulse wave amplitude information at the first position and the second position obtained based on the first pulse wave information obtained by the first pulse wave information detection unit and the second pulse wave information obtained by the second pulse wave information detection unit, and the distance in the vertical direction, wherein the pulse wave amplitude information is a difference between a maximum value and a minimum value within a pulsation.

2. The blood pressure estimation device according to claim 1, characterized in that: The first pulse wave information and the second pulse wave information are acquired as video signals, respectively, and the pulse wave amplitude information is calculated based on the video signals.

3. The blood pressure estimation device according to claim 1 or 2, characterized in that: The blood pressure estimation unit estimates the blood pressure of the biological body by inputting the pulse wave amplitude information into a blood pressure function. The blood pressure function is derived based on a basic function. The basic function includes a deviation coefficient that depends on the characteristics of the blood vessels of the biological body and represents the relationship between the blood pressure of the biological body and the cross-sectional area of ​​the blood vessels. The blood pressure function uses the pulse wave amplitude information as a variable and also includes the deviation coefficient.

4. The blood pressure estimation device according to claim 1 or 2, characterized in that: The pulse wave amplitude information is pulse wave amplitude ratio information of the first pulse wave information and the second pulse wave information, The blood pressure estimation unit estimates the blood pressure of the living body based on the distance between the first position and the second position in addition to the pulse wave amplitude ratio information.

5. The blood pressure estimation device according to claim 1 or 2, characterized in that: The blood pressure estimation unit estimates the blood pressure of the biological body according to the following formula (1): P=qh / (1-R)+α … Formula (1) Here, q represents density, h represents the distance in the vertical direction, R represents the ratio of the pulse wave amplitude information at the first position to the pulse wave amplitude information at the second position, and α represents a deviation coefficient.

6. The blood pressure estimation device according to claim 1 or 2, characterized in that: The pulse wave amplitude information is difference information between the pulse wave amplitudes of the first pulse wave information and the second pulse wave information. The blood pressure estimation unit estimates the blood pressure of the living body based on the difference information.

7. The blood pressure estimation device according to claim 3, characterized in that: The blood pressure estimation device includes a variation coefficient determination unit that determines the variation coefficient based on the first pulse wave information and the second pulse wave information and the blood pressure information and the pulse wave information of the living body at a reference position of the living body.

8. The blood pressure estimation device according to claim 1 or 2, characterized in that: The first pulse wave information is acquired from a predetermined part of the living body, and the predetermined part is moved to acquire the second pulse wave information from the predetermined part.

9. The blood pressure estimation device according to claim 1 or 2, characterized in that: The first pulse wave information is acquired from one of the two hands of the living body, and the second pulse wave information is acquired from the other of the two hands.

10. The blood pressure estimation device according to claim 1 or 2, characterized in that: The first pulse wave information is obtained from one of the hands of the living body, and the other of the hands is moved to obtain the second pulse wave information from the other of the hands.

11. The blood pressure estimation device according to claim 1 or 2, characterized in that: A correction coefficient is obtained based on pulse wave information of different predetermined parts of the living body acquired at the same position in the vertical direction, and at least one of the first pulse wave information and the second pulse wave information is corrected based on the correction coefficient.

12. A blood pressure estimation method, characterized in that: The blood pressure estimation method comprises the following steps: a first pulse wave information detecting step of detecting first pulse wave information at a first position of the biological body; a second pulse wave information detection step of detecting second pulse wave information at a second position of the living body that is spaced apart from the first position in a vertical direction; as well as A step of estimating the blood pressure of the biological body based on pulse wave amplitude information at the first position and the second position obtained according to the first pulse wave information obtained in the first pulse wave information detection step and the second pulse wave information obtained in the second pulse wave information detection step, and the distance in the vertical direction, wherein the pulse wave amplitude information is the difference between the maximum value and the minimum value within the pulsation.

13. A blood pressure estimation program, characterized in that: The blood pressure estimation program causes the computer to execute the following processing: detecting first pulse wave information at a first location of the biological body; detecting second pulse wave information at a second position of the living body that is spaced apart from the first position in a vertical direction; as well as The blood pressure of the living body is estimated based on pulse wave amplitude information at the first position and the second position obtained from the first pulse wave information and the second pulse wave information, and the distance in the vertical direction, the pulse wave amplitude information being the difference between the maximum value and the minimum value in a pulsation.

Images