Biological condition estimation device

Abstract

To provide a technology to extract an electrocardiographic feature amount accurately.SOLUTION: A biological state estimation device includes: an electrocardiographic waveform acquisition unit; an electrocardiographic feature amount extraction unit for searching for an electrocardiographic waveform and extracting an electrocardiographic feature amount; a pulse wave waveform acquisition unit; and a pulse wave feature amount extraction unit for searching for a pulse wave waveform and extracting a pulse wave feature amount, and estimates a biological state on the basis of at least the electrocardiographic feature amount. The biological state estimation device includes an electrocardiographic waveform quality determination unit for determining whether or not the electrocardiographic waveform has the quality that allows the electrocardiographic feature amount to be extracted only from the electrocardiographic waveform: a first search reference point setting unit for setting a first reference point for searching for an electrocardiographic waveform when the electrocardiographic waveform is determined to have the quality that allows the electrocardiographic feature amount to be extracted; and a second search reference point setting unit for setting a second reference point for searching for an electrocardiographic waveform on the basis of the pulse wave feature amount when the electrocardiographic waveform is determined not to have the quality that allows the electrocardiographic feature amount to be extracted. The electrocardiographic feature amount extraction unit searches for the electrocardiographic waveform on the basis of the first reference point or the second reference point, and extracts the electrocardiographic feature amount.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a biological state estimating device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there is known an apparatus that simultaneously measures an electrocardiogram waveform and a pulse waveform and estimates a biological condition from characteristic quantities related to the circulatory system, such as a heartbeat interval.

[0003] In such devices that simultaneously measure the electrocardiogram waveform and the pulse waveform, features are basically extracted from the electrocardiogram waveform, but when a large amount of noise is superimposed on the electrocardiogram waveform, the features obtained from the pulse waveform are complemented (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-261419 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in such conventional techniques, when a large amount of noise is superimposed on the electrocardiogram waveform, the electrocardiogram waveform is not searched for, making it difficult to extract features that are only present in the electrocardiogram waveform using the pulse waveform.

[0006] In view of the above-described conventional techniques, the present invention aims to provide a technique that can accurately extract features of an electrocardiogram waveform by searching for the electrocardiogram waveform based on features of a pulse waveform, even when noise that is likely to affect the electrocardiogram waveform is present. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides an electrocardiogram waveform acquisition unit for acquiring an electrocardiogram waveform; an electrocardiogram feature extraction unit that searches the electrocardiogram waveform and extracts a feature of the electrocardiogram waveform; a pulse waveform acquiring unit for acquiring a pulse waveform; a pulse wave feature quantity extraction unit that searches the pulse waveform acquired by the pulse waveform acquisition unit and extracts feature quantities of the pulse waveform; a biological condition estimating device for estimating a biological condition based on at least the electrocardiogram waveform feature quantity out of the electrocardiogram waveform feature quantity and the pulse waveform feature quantity, an electrocardiogram waveform quality determination unit that determines whether the electrocardiogram waveform has a quality that allows extraction of an electrocardiogram waveform feature quantity from the electrocardiogram waveform alone; a first search reference point setting unit that sets a first reference point for searching the electrocardiogram waveform when it is determined that the electrocardiogram waveform has a quality that allows extraction of a feature amount of the electrocardiogram waveform; a second search reference point setting unit that sets a second reference point for searching the electrocardiogram waveform based on the feature value of the pulse waveform when it is determined that the electrocardiogram waveform does not have a quality that allows extraction of the feature value of the electrocardiogram waveform; Equipped with The electrocardiogram feature amount extraction unit is characterized in that it searches the electrocardiogram waveform based on the first reference point or the second reference point to extract a feature amount of the electrocardiogram waveform.

[0008] According to this, even if it is determined that the electrocardiogram waveform has a quality that does not allow extraction of the feature value of the electrocardiogram waveform, the electrocardiogram waveform is searched for based on the second reference point set based on the feature value of the pulse waveform. Therefore, even when there is noise that easily affects the electrocardiogram waveform, the feature amount of the electrocardiogram waveform can be extracted with high accuracy, and the estimation accuracy of the biological condition is improved. Also, even when it is difficult to search for the electrocardiogram waveform from only the electrocardiogram waveform, searching for the electrocardiogram waveform based on the second reference point based on the feature amount of the pulse waveform enables accurate analysis of the electrocardiogram waveform. The biological condition estimation device may estimate the biological condition based on at least the features of the electrocardiogram waveform among the features of the electrocardiogram waveform and the features of the pulse waveform, and may estimate the biological condition from only the features of the electrocardiogram waveform, or may estimate the biological condition based on both the features of the electrocardiogram waveform and the features of the pulse waveform.

[0009] In the present invention, a pulse waveform quality determination unit that determines whether the pulse waveform has a quality that allows a feature of the pulse waveform to be extracted, When it is determined that the pulse waveform has a quality that enables extraction of a feature value of the pulse waveform, the pulse wave feature value extraction unit may extract the feature value of the pulse waveform.

[0010] In this way, it is determined whether the pulse waveform has the quality to extract features of the pulse waveform, and if it does, a second reference point is set based on the extracted features of the pulse waveform. This makes it possible to accurately extract features of the electrocardiogram waveform even when there is noise that is likely to affect the electrocardiogram waveform but not the pulse waveform.

[0011] In the present invention, The pulse wave feature amount extraction unit extracts a rising edge of the pulse waveform, The second search The reference point setting section may set the time of a rising edge of the pulse waveform as the second reference point.

[0012] Various features can be used as the feature of the pulse waveform, but in this way, the second reference point can be set using the rising edge of the pulse waveform as the feature of the pulse waveform.

[0013] In the present invention, The pulse wave feature amount extraction unit extracts a peak of the pulse waveform, The second search reference point setting section may set the time of a peak of the pulse waveform as the second reference point.

[0014] In this way, the second reference point can be set using the peak of the pulse waveform as a feature amount of the pulse waveform.

[0015] In the present invention, the pulse wave feature amount extraction unit extracts a peak in a first derivative waveform calculated from the pulse waveform; The second search reference point setting section may set, as the second reference point, a time of a peak in a first derivative waveform calculated from the pulse waveform.

[0016] In this way, the second reference point can be set using a peak in a first derivative waveform calculated from the pulse waveform as a feature amount of the pulse waveform.

[0017] In the present invention, the pulse wave feature amount extraction unit extracts a peak in a second derivative waveform calculated from the pulse waveform; The second search reference point setting unit is configured to set a peak in a second derivative waveform calculated from the pulse waveform. The time of the second reference point may be set as the second reference point.

[0018] In this way, the second reference point can be set using the peak in the second derivative waveform calculated from the pulse waveform as the pulse waveform feature amount. In this way, the pulse waveform feature amount can be, but is not limited to, the rising edge of the pulse waveform, the peak or bottom of the pulse waveform, the peak of the first derivative or the second derivative of the pulse waveform, or the like.

[0019] In the present invention, The electrocardiogram feature extraction unit is configured to extract the electrocardiogram feature set by the second search reference point setting unit. The above The electrocardiogram waveform for each beat specified based on the second reference point may be synchronized and an arithmetic average may be calculated, and a feature amount of the electrocardiogram waveform may be extracted from the synchronized arithmetic average waveform obtained.

[0020] Various methods can be used to extract the features of an electrocardiogram waveform, but in some cases, such as myoelectric noise, noise can be canceled and a clean synchronized average waveform can be obtained by synchronizing the electrocardiogram waveform for each beat and calculating the average. Therefore, by searching for the synchronized average waveform, electrocardiogram features can be extracted with high accuracy.

[0021] In the present invention, A display unit for displaying information is provided, The synchronous averaged waveform may be displayed on the display unit.

[0022] In this way, even if noise such as myoelectricity is superimposed, a clean electrocardiogram waveform with the noise cancelled can be displayed to the user.

[0023] In the present invention, A blood pressure value may be estimated as the biological condition.

[0024] In this way, it is possible to provide a biological condition estimation device that can estimate blood pressure values ​​with high accuracy.

[0025] In the present invention, A heart rate may be estimated as the biological condition.

[0026] In this way, it is possible to provide a biological state estimation device that can estimate the heart rate with high accuracy. Effect of the Invention

[0027] The present invention aims to provide a technology that can accurately extract features of an electrocardiogram waveform even in the presence of noise that is likely to affect the electrocardiogram waveform, by searching for the electrocardiogram waveform based on features of a pulse waveform. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a diagram showing the appearance of a biological state estimating device according to an embodiment. [Diagram 2] FIG. 2 is a diagram for explaining features of the biological state estimating device according to the embodiment. [Diagram 3] FIG. 3 is a diagram illustrating a hardware configuration of the biological state estimating apparatus according to the embodiment. As illustrated in FIG. [Figure 4] FIG. 4 is a diagram illustrating a software configuration of the biological state estimating apparatus according to the embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of searching for an electrocardiogram feature according to the embodiment. [Figure 6] FIG. 6 is a diagram illustrating another example of a search for an electrocardiogram feature according to the embodiment. [Figure 7] FIG. 7 is a diagram for explaining a search for an electrocardiogram feature according to the embodiment. [Figure 8] FIG. 8 is a diagram for explaining a search for an electrocardiogram feature according to the embodiment. [Figure 9] FIG. 9 is a diagram for explaining a search for an electrocardiogram feature according to the embodiment. [Figure 10] FIG. 10 is a flowchart illustrating a procedure for searching an electrocardiogram according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0030] <Example 1> An example of an embodiment of the present invention will be described below. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, and the like of the components described in this example are not intended to limit the scope of the present invention to those alone.

[0031] Fig. 1 shows an external view of a biological state estimation device 10 according to this embodiment. Fig. 1(A) shows the external view when a belt 200 is wrapped around a subject and worn, and Fig. 1(B) shows the external view from the inner circumferential surface 202 side when the belt 200 is unfolded.

[0032] The biological state estimation device 10 mainly includes a main body 100 and a belt 200. The main body 100 is provided on an outer peripheral surface 201 of the belt 200, and a control unit 101 (described later) and the like are housed therein. A display unit 110 and an operation unit 111 are provided on the outer surface. A hook-and-loop fastener 210 is provided on one end in the longitudinal direction of an inner peripheral surface 202 of the belt 200. The other hook-and-loop fastener that engages with the hook-and-loop fastener 210 when worn is provided on the outer peripheral surface 201 of the belt 200. A group of electrodes 220A to 220F for measuring electrocardiogram waveforms are arranged at equal intervals in the longitudinal direction on one edge 202A in the width direction of the inner peripheral surface 202 of the belt 200. An electrocardiogram sensor 220 composed of the group of electrodes 220A to 220F is arranged on the edge 202A that is on the shoulder side when worn on the upper arm. Electrodes 231A, 232A, 232B, and 231B constituting a sensor unit 230 of a pulse wave sensor are arranged on the other end 202B in the width direction of the inner circumferential surface 202 of the belt 200. Electrodes 231A and 231B are electrodes for passing electricity to the upper arm, and electrodes 232A and 232B are electrodes for detecting voltage. The sensor unit 230 is provided at a position on the elbow side when worn on the upper arm. When worn on the upper arm, the sensor unit 230 is arranged with electrodes 231A, 232A, 232B, and 231B in this order from the shoulder side to the elbow side along the brachial artery.

[0033] (Characteristics of the biological condition estimation device) In the biological condition estimation device 10 according to this embodiment, the electrocardiogram waveform (electrocardiogram) and pulse wave waveform (pulse wave signal) acquired through the electrocardiogram sensor 220 and the sensor unit 230 of the pulse wave sensor are searched for, a feature of the electrocardiogram waveform (electrocardiogram feature) and a feature of the pulse wave waveform (pulse wave feature) are extracted, and a biological condition such as a blood pressure value is estimated based on at least the electrocardiogram feature of the electrocardiogram feature and the pulse wave feature. When the electrocardiogram has a quality that allows the electrocardiogram feature to be extracted and the pulse wave signal has a quality that allows the pulse wave feature to be extracted, each can be searched for and the electrocardiogram feature and pulse wave feature can be extracted with high accuracy, so that a biological condition such as a blood pressure value based on these can also be estimated with high accuracy.

[0034] Depending on the state in which the biological state estimation device 10 is worn, the user's body movements, posture, etc., noise may be superimposed on the electrocardiogram, reducing the quality of the electrocardiogram. It is difficult to accurately extract electrocardiogram features from only an electrocardiogram of such low quality. In this case, depending on the cause of the noise occurring in the electrocardiogram, the electrocardiogram may be affected but the pulse wave signal may be unaffected or only slightly affected. Figure 2 is a graph showing such a relationship between the electrocardiogram and the pulse wave signal. Here, the top row shows the electrocardiogram, the second row from the top shows the pulse wave signal detected by the photoplethysmography sensor, and the third row from the top shows the pulse wave signal detected by the photoplethysmography sensor. The third row shows the pulse wave signal detected by the pressure-type pulse wave sensor, and the bottom row shows the output signal of the acceleration sensor (the output signals in the three-axis directions are shown by solid lines, dashed lines, and dotted lines). In FIG. 2, as shown in the output signal of the acceleration sensor, the waveform is shown in a state where the user wearing the biological state estimation device 10 moves before Tm, and there is no body movement after Tm, with time Tm shown as the vertical solid line as the boundary. Therefore, in the electrocardiogram in the top row, the waveform is superimposed with myoelectricity before time Tm, whereas the waveform is not superimposed with myoelectricity after Tm, and the electrocardiogram waveform is significantly different at the boundary of time Tm. In contrast, no significant change is observed in the pulse wave signals from any of the pulse wave sensors before and after time Tm. Moreover, while the electrocardiogram waveform is significantly disturbed due to the occurrence of a large body movement during the period Prd shown by the dashed line, no disturbance is observed in any of the pulse wave signals.

[0035] Due to such characteristics of the electrocardiogram and pulse wave signal, even if the electrocardiogram has a quality such that electrocardiographic features cannot be extracted from the electrocardiogram alone, if the pulse wave signal has a quality such that the pulse wave features can be extracted, it is possible to set a search reference point for extracting the electrocardiographic features using the pulse wave features, as described below. Therefore, the electrocardiographic features can be extracted with high accuracy, and the biological condition such as blood pressure can also be estimated with high accuracy.

[0036] (Hardware configuration) 3 shows a hardware configuration of the biological state estimation device 10 according to this embodiment. The biological state estimation device 10 mainly includes a main body 100 and a belt 200.

[0037] As described above, on the inner circumferential surface of belt 200, electrode groups 220A to 220F for measuring an electrocardiogram are arranged. A sensor unit 230 of a pulse wave sensor for measuring a pulse wave is disposed on the inner circumferential surface of the belt 200. The sensor unit 230 includes a pair of electrodes 231A and 231B for passing electricity through the user's body, and a pair of electrodes 232A and 232B for detecting a voltage. The belt 200 is also provided with an electricity supply and voltage detection circuit 233 that supplies electricity between the electrodes 231A and 231B of the sensor unit 230 and detects the voltage between the electrodes 232A and 232B. The electricity supply and voltage detection circuit 233 may be provided in the main body 100. The belt 200 also includes a pressure cuff 204 that is like a bag and can contain fluid.

[0038] The main body 100 is provided with a control unit 101, a memory unit 102, a battery 103, a switch circuit 104, a subtraction circuit 105, an analog front end (AFE) 106, a pressure sensor 107, an oscillator circuit 108, a pump 109, a display unit 110, an operation unit 111, a valve 112, a pump drive circuit 113, an acceleration sensor 114, an AFE 115, and a communication unit 116.

[0039] The control unit 101 includes a central processing unit (CPU) 1011, a random access memory (RAM) 1012, a read only memory (ROM) 1013, etc., and controls each of the components. The control unit 101 controls the control circuit 102 to realize various functions described later. The storage unit 102 is an auxiliary storage device such as a semiconductor memory or a hard disk drive (HDD), and stores programs executed by the control unit 101, setting data required to execute the programs, measurement results, etc. A part or all of the programs may be stored in the ROM 1013.

[0040] The battery 103 supplies power to the control unit 101 etc. The battery 103 can be configured by, for example, a rechargeable battery.

[0041] Each of the electrodes 220A to 220F included in the electrocardiogram sensor 220 is connected to an input terminal of a switch circuit 104. Two output terminals of the switch circuit 104 are respectively connected to two input terminals of a subtraction circuit 105. The switch circuit 104 receives a switch signal from the control unit 101, and connects two electrodes designated by the switch signal to the subtraction circuit 105. The subtraction circuit 105 subtracts a potential input from one input terminal from a potential input from the other input terminal. The subtraction circuit 105 outputs a potential difference signal representing a potential difference between the two connected electrodes to the AFE 106. The subtraction circuit 105 is, for example, an instrumentation amplifier. The AFE 106 includes, for example, a low pass filter (LPF), an amplifier, and an analog-to-digital (AD) converter. The potential difference signal is filtered by the LPF, amplified by the amplifier, and converted into a digital signal by the AD converter. The potential difference signal converted into a digital signal is output to the control unit 101. The control unit 101 acquires the potential difference signal acquired in time series from the AFE 106 as an electrocardiogram.

[0042] The current and voltage detection circuit 233 passes a high-frequency constant current between the electrodes 231A and 231B. For example, the frequency of the current is 50 kHz, and the current value is 1 mA. The current and voltage detection circuit 233 detects the voltage between the electrodes 232A and 232B while current is being passed between the electrodes 231A and 231B, and generates a detection signal. The detection signal indicates a change in electrical impedance due to a pulse wave propagating through the part of the artery where the electrodes 232A and 232B face each other. The current and voltage detection circuit 233 performs signal processing including rectification, amplification, filtering, and AD conversion on the detection signal, and outputs the detection signal to the control unit 101. The control unit 101 acquires the detection signal output in time series from the current and voltage detection circuit 233 as a pulse wave signal.

[0043] The acceleration sensor 114 detects acceleration in three axes, namely, X, Y, and Z directions, and outputs the detection signal to AFE1. The AFE 115 includes, for example, an amplifier and an AD converter. The detection signal of the acceleration sensor 114 is amplified by the amplifier and converted into a digital signal by the AD converter. The detection signal converted into a digital signal is output to the control unit 101. The control unit 101 controls the AFE 1 1 The detection signals obtained in time series from 5 are obtained as three-axis acceleration signals.

[0044] The pressure sensor 107 is connected to the pressing cuff 204 via a pipe, and the pump 109 and the valve 112 are connected to the pressing cuff 204 via a pipe. The pipe may be a common pipe. The pump 109 is, for example, a piezoelectric pump, and supplies air as a fluid to the pressing cuff 204 through the pipe in order to increase the pressure of the pressing cuff 204. The valve 112 is mounted on the pump 109, and is controlled to open and close according to the operating state of the pump 109. When the valve 112 is in an open state, the pressing cuff 204 communicates with the atmosphere, and the air in the pressing cuff 204 is discharged to the atmosphere. The valve 112 has a function of a check valve, and does not allow air to flow backward. The pump drive circuit 113 drives the pump 109 based on a control signal received from the control unit 101.

[0045] Pressure sensor 107 detects the pressure (also called cuff pressure) in pressure cuff 204 and generates an electrical signal representing the cuff pressure. The cuff pressure is, for example, a pressure based on atmospheric pressure. Pressure sensor 107 is, for example, a piezo-resistance pressure sensor. Oscillating circuit 108 oscillates based on the electrical signal from pressure sensor 107 and outputs a frequency signal having a frequency corresponding to the electrical signal to a control unit. 101 Here, the output of the pressure sensor 107 is used to control the pressure in the pressure cuff 204, and is also used to calculate blood pressure values ​​(including systolic blood pressure (maximum blood pressure) and diastolic blood pressure (minimum blood pressure)) by the oscillometric method.

[0046] Although an example in which the control unit 101 includes one CPU 1011 has been described, the configuration of the control unit 101 is not limited to this, and the control unit 101 may include a plurality of processors. The biological state estimation device 10 may also include a communication unit 116 for communicating with an external device such as a user's mobile terminal (e.g., a smartphone). The communication method may be an appropriate wired and / or wireless method. Depending on the communication method, the communication unit 116 The device includes a wired communication module and / or a wireless communication module. As a wireless communication method, for example, Bluetooth (registered trademark), BLE (Bluetooth Low Energy), etc. can be adopted.

[0047] The operation unit 111 is an input device through which a user inputs instructions to the biological state estimating device 10. For example, it is composed of a button. The display unit 110 is a display device for displaying measurement results and messages to the user, and can be configured, for example, by a liquid crystal display (LCD) or an OLED (Organic Light Emitting Diode) display.

[0048] (Software configuration) FIG. 4 shows a biological state estimating apparatus according to the present embodiment. 10 4 shows the software configuration of the electrocardiogram measurement control unit 101A, the pulse wave measurement control unit 101B, the acceleration measurement control unit 101C, the electrocardiogram quality determination unit 101D, the pulse wave quality determination unit 101E, the pulse wave feature value extraction unit 101F, the pulse wave-based search reference point setting unit 101G, the electrocardiogram-based search reference point setting unit 101H, the electrocardiogram feature value extraction unit 101I, the pulse wave transit time calculation unit 101J, the blood pressure value calculation unit 101K, the display control unit 101L, the blood pressure measurement control unit 101M, the instruction input unit 101N, the calibration unit 101P, and the error processing unit 101Q shown in FIG. 4 are realized by the control unit 101 executing the program stored in the storage unit 192. The electrocardiogram storage unit 102A, the pulse wave storage unit 102B, the acceleration storage unit 102C, the blood pressure value storage unit 102E, and the blood pressure value storage unit 102F are realized by the storage unit 102.

[0049] The electrocardiogram measurement control unit 101A controls the switch circuit 104 to acquire an electrocardiogram. Specifically, the electrocardiogram measurement control unit 101A generates a switch signal for selecting two of the six electrodes 220A to 220F, and outputs the switch signal to the switch circuit 104. The electrocardiogram measurement control unit 101A acquires a potential difference signal obtained using the two selected electrodes, and stores time-series data of the acquired potential difference signal as an electrocardiogram in the electrocardiogram storage unit 102A.

[0050] When the user wears the biological state estimation device 10 on the upper arm, the electrocardiogram measurement control unit 101A determines an optimal electrode pair for acquiring an electrocardiogram. For example, the electrocardiogram measurement control unit 101A acquires an electrocardiogram for each of all electrode pairs, and determines the electrode pair that provides an electrocardiogram with the largest amplitude of the R wave as the optimal electrode pair. After that, the electrocardiogram measurement control unit 101A measures the electrocardiogram using the optimal electrode pair.

[0051] Pulse wave measurement control unit 101B controls energization and voltage detection circuit 233 to acquire a pulse wave signal. Specifically, pulse wave measurement control unit 101B instructs energization and voltage detection circuit 233 to pass a current between electrodes 231A and 231B, and acquires a detection signal indicating the voltage between electrodes 232A and 232B detected in a state in which a current is passed between electrodes 231A and 231B. Pulse wave measurement control unit 101B stores time-series data of the detection signal as a pulse wave signal in pulse wave storage unit 102B.

[0052] Acceleration measurement control section 101C acquires the three-axis acceleration output by acceleration sensor 114 at a predetermined cycle, and stores the acceleration as an acceleration signal in acceleration storage section 102C.

[0053] The electrocardiogram quality determination unit 101D determines whether the electrocardiogram stored in the electrocardiogram storage unit 102A has a quality that allows electrocardiogram features to be extracted from the electrocardiogram alone. The following methods can be used to determine the quality of the electrocardiogram. For example, the quality of the electrocardiogram can be determined by determining whether the contact state of the electrodes is good or bad according to a criterion such as whether the electrocardiogram waveform is constant. In addition, the quality of the electrocardiogram can be determined by acquiring a three-axis acceleration signal from the acceleration storage unit 102C and determining whether the acceleration signal is equal to or lower than a predetermined threshold. In addition, the quality of the electrocardiogram can be determined by the presence or absence of an electromyogram. When an electrocardiogram is mixed with an electrocardiogram, irregular fine vibrations are observed, so the presence or absence of an electromyogram can be determined by detecting the presence or absence of such irregular fine vibrations. The quality of the electrocardiogram may be determined by any of the above-mentioned methods, or by using any two or three or all of the above-mentioned methods. In addition, the determination of the quality of the electrocardiogram is not limited to these, and other known methods may be adopted. It can be used.

[0054] Pulse wave quality determination unit 101E determines whether the pulse wave signal stored in pulse wave storage unit 102B has a quality that allows extraction of pulse wave features. The following methods can be used to determine the quality of the pulse wave signal. For example, the quality of the pulse wave signal can be determined by determining whether the contact state of the electrodes is good or bad according to a criterion such as whether the pulse wave signal is constant. In addition, the quality of the pulse wave signal can be determined by acquiring a three-axis acceleration signal from acceleration storage unit 102C and determining whether the acceleration signal is equal to or less than a predetermined threshold. In addition, the quality of the pulse wave signal can be determined by determining whether the amplitude value of one beat of the pulse wave signal stored in pulse wave storage unit 102B is equal to or less than a predetermined threshold. The quality of the pulse wave signal can be determined by using any of the above-mentioned methods, or any two or three or all of the above-mentioned methods. In addition, the method of determining the quality of the pulse wave signal is not limited to these, and other known methods can be adopted.

[0055] The electrocardiogram-based search reference point setting unit 101H sets a reference point for searching the electrocardiogram when the electrocardiogram feature amount extracting unit 101I extracts features from the electrocardiogram waveform. For example, a peak point corresponding to an R wave can be set as the reference point. The reference point is not limited to this, and a peak point corresponding to a Q wave, a peak point for an S wave, or the like may be set as the reference point according to the purpose.

[0056] As described above, the electrocardiogram feature extraction unit 101I searches for the reference points set by the electrocardiogram-based search reference point setting unit 101H in the electrocardiogram and extracts the electrocardiogram feature. As the electrocardiogram feature, various feature values ​​such as P waves, QRS waves, T waves, PQRST waves, J waves, PQ interval, QT interval, and QRS time are targeted in addition to the R wave. FIG. 5 shows an example of an electrocardiogram having good quality and capable of extracting electrocardiogram features only from the electrocardiogram. The upper part of FIG. 5 shows an example of an electrocardiogram read from the electrocardiogram storage unit 102A, and the lower part of FIG. 5 shows an example of a pulse wave read from the pulse wave storage unit 102B. When the quality of the electrocardiogram is good and the peak points corresponding to the R waves are set as the reference points, the electrocardiogram waveform is searched, the peak points Wr1, Wr2, and Wr3 corresponding to the R waves are detected, and their times are specified. In this way, the beat times are extracted as the intervals between the peaks corresponding to the R waves as electrocardiogram features. Based on the beat times thus obtained, the heart rate as the biological condition can be estimated. In addition, the electrocardiogram can be searched as indicated by the arrows, using the peak points Wr1, Wr2, and Wr3 corresponding to the R waves as references, and various electrocardiogram features as described above can be extracted. In sections where a good electrocardiogram is obtained, electrocardiogram features can be extracted from the electrocardiogram alone, but in some cases, pulse wave features (e.g., the rising edge of the pulse wave) may be searched for based on this electrocardiogram feature (here, the time of the peak of the R wave of the electrocardiogram, which is the beat time).

[0057] When the electrocardiogram quality determination unit 101D determines that the electrocardiogram does not have the quality that allows the electrocardiogram feature to be extracted from the electrocardiogram alone, the pulse wave feature extraction unit 101F extracts the pulse wave feature from the pulse wave stored in the pulse wave storage unit 102B, and the pulse wave-based search reference point setting unit 101G subsequently sets reference points for searching the electrocardiogram. The feature related to the ejection of the pulse wave can be, but is not limited to, the rise, bottom, and peak of the pulse wave, or the peak of the first derivative and the peak of the second derivative of the pulse wave. FIG. 6 shows examples of an electrocardiogram and a pulse wave signal when it is determined that the quality of the electrocardiogram is not good and the electrocardiogram does not have the quality to extract an electrocardiogram feature, but the pulse wave signal has the quality to extract a pulse wave feature. The upper part of FIG. 6 shows an example of an electrocardiogram read from the electrocardiogram storage unit 102A, and the lower part of FIG. 6 shows an example of a pulse wave signal read from the pulse wave storage unit 102B. The pulse wave feature extraction unit 101F extracts rising points Wp1, Wp2, and Wp3, which are pulse wave feature values, from the pulse wave signal stored in the pulse wave storage unit 102B, and specifies their times. The data of the pulse wave feature values ​​extracted in this way is provided to the pulse wave-based search reference point setting unit 101G. The pulse wave feature quantity extraction unit 101F extracts pulse wave feature quantities for estimating a blood pressure value, which will be described later. Put out.

[0058] Pulse wave-based search reference point setting unit 101G sets reference points for searching an electrocardiogram based on the pulse wave feature extracted in this manner. When the rising point of the pulse wave signal is extracted, pulse wave-based search reference point setting unit 101G sets the electrocardiogram time point corresponding to the time of the rising point of the pulse wave signal as a reference point, and provides this to electrocardiogram feature extractor 101I. Electrocardiogram feature extractor 101I searches for electrocardiogram feature values ​​using as references the search reference points set based on the pulse wave feature values ​​received from pulse wave feature extractor 101F. As described above, when rising points Wp1, Wp2, and Wp3 of the pulse wave signal and their times are extracted as pulse wave feature values, electrocardiogram feature extractor 101I uses the rising point of the pulse wave signal as a reference and searches the electrocardiogram within a predetermined time from the time of this rising point as indicated by the arrows, ,exampleFor example, the peak point corresponding to the R wave is detected. Then, the interval between peaks corresponding to R waves is extracted as an electrocardiogram feature. It is possible.

[0059] Fig. 7 shows another example of an electrocardiogram and a pulse wave signal when it is determined that the electrocardiogram does not have a quality that allows electrocardiogram features to be extracted from the electrocardiogram alone, but the pulse wave signal has a quality that allows pulse wave features to be extracted. Here, the upper part of Fig. 7 shows the pulse wave signal read from the pulse wave storage unit 102B, and the lower part shows the electrocardiogram read from the electrocardiogram storage unit 102A. In this example, the electrocardiogram and pulse wave were measured while the user wearing the biological state estimation device 10 was sitting on a chair with his arms raised in front of him. When measuring an electrocardiogram with one arm, the electrocardiogram waveform itself detected by the electrocardiogram sensor 220 is small (less than 1 / 10 of lead I) and the influence of myoelectricity is significant.

[0060] In the example shown in FIG. 7, pulse wave feature amount extractor 101F extracts peak points Wp11, Wp12, Wp13, Wp14, and so on, of the pulse wave. Based on the data of the peak point Wp11 of the pulse wave signal extracted in this manner, pulse wave-based search reference point setting unit 101G provides the times of peak points Wp11 of the pulse wave signal, etc., to electrocardiogram feature extraction unit 101I as reference points for searching an electrocardiogram. The electrocardiogram feature extraction unit 101I searches the electrocardiogram, for example, based on the time of the peak point Wp11 of the pulse wave signal, and extracts peak points Wr11, Wr12, Wr13, Wr14, etc. corresponding to the R wave. Even if the peak point corresponding to the R wave is extracted in the electrocardiogram, as shown in FIG. 7, the electrocardiogram is obtained as a dirty waveform with superimposed myoelectricity, and it is difficult to extract the electrocardiogram feature from the electrocardiogram alone based on the peak point corresponding to the R wave. For this reason, when the synchronous averaging of the waveform for each beat as shown in FIG. 8(A) is taken based on the peak point corresponding to the R wave extracted as described above, a clean waveform (synchronous averaging waveform) as shown in FIG. 8(B) is obtained. FIG. 9(A) shows the waveform for each beat in gray, and the synchronous averaging waveform obtained by taking the synchronous averaging based on the peak point corresponding to the R wave is shown in black. FIG. 9(B) shows the waveform of the electrocardiogram measured by I lead for comparison. Just as P waves can be clearly extracted from the electrocardiogram waveform shown in Figure 9(B), P waves can also be clearly extracted from the electrocardiogram waveform obtained by synchronous averaging shown in Figure 9(A), so other electrocardiogram features can be extracted in a similar manner.

[0061] Pulse wave propagation time calculation unit 101J calculates the pulse wave propagation time based on the time difference between the feature points of the electrocardiogram and the feature points of the pulse wave signal acquired from electrocardiogram feature amount extraction unit 101I and pulse wave feature amount extraction unit 101F. For example, pulse wave propagation time calculation unit 101J detects the time of the peak point corresponding to the R wave from the electrocardiogram, detects the time of the rising point from the pulse wave signal, and calculates the difference obtained by subtracting the time of the peak point from the time of the rising point as the pulse wave propagation time.

[0062] The blood pressure value calculation unit 101K calculates the blood pressure value based on the pulse wave transit time calculated by the pulse wave transit time calculation unit 101J and a calculation formula for calculating the blood pressure value from the pulse wave transit time. Since a known calculation formula can be appropriately adopted as the calculation formula for calculating the blood pressure value from the pulse wave transit time, a description thereof will be omitted. The blood pressure value calculated by the blood pressure value calculation unit 101K is the blood pressure value It is stored in storage unit 102E.

[0063] The instruction input unit 101N accepts an instruction input by a user using the operation unit 111. For example, when the user performs an operation to instruct execution of blood pressure measurement, the instruction input unit 101N gives an instruction to start blood pressure measurement to the blood pressure measurement control unit 101M.

[0064] The blood pressure measurement control unit 101M controls the pump drive circuit 113 to perform blood pressure measurement. When the blood pressure measurement control unit 101M receives an instruction to start blood pressure measurement from the instruction input unit 101N, it drives the pump 109 via the pump drive circuit 113. This starts the supply of air to the pressure cuff 204. The pressure cuff 204 is inflated, and the upper arm of the user is compressed. The blood pressure measurement control unit 101M monitors the cuff pressure using the pressure sensor 107. During the pressurization process of supplying air to the pressure cuff 204, the blood pressure measurement control unit 101M calculates the blood pressure value by the oscillometric method based on the pressure signal output from the pressure sensor 107. The blood pressure value includes, but is not limited to, a systolic blood pressure (SBP) and a diastolic blood pressure (DBP). The blood pressure measurement control unit 101M associates the calculated blood pressure value with time information and stores it in the blood pressure value storage unit 102F. The blood pressure measurement control unit 101M can calculate the heart rate at the same time as the blood pressure value. When the calculation of the blood pressure value is completed, the blood pressure measurement control unit 101M stops the pump 109 via the pump drive circuit 113. This stops the valve 204 from the pressure cuff 204. 112 Air is discharged through the blood pressure measurement control section. 101M Alternatively, the blood pressure value may be calculated by the oscillometric method during the depressurization process in which air is discharged from the pressure cuff 204 that has been pressurized to a predetermined cuff pressure.

[0065] The display control unit 101L controls the display unit 110 to display messages to the user and measurement results such as blood pressure values ​​and heart rates on the display unit. 110 Display it on.

[0066] The calibration unit 101P calibrates the blood pressure calculation formula based on the pulse wave transit time obtained by the pulse wave transit time calculation unit 101J and the blood pressure value obtained by the blood pressure measurement control unit 101M. The correspondence relationship between the pulse wave transit time and the blood pressure value varies depending on the individual user and also on the position where the biological state estimation device 10 is worn. For this reason, the blood pressure calculation formula is calibrated. As a method for calibrating the blood pressure calculation formula, a known method can be adopted, and therefore a description thereof will be omitted.

[0067] When the ECG quality determining unit 101D determines that the ECG does not have the quality that allows the ECG feature to be extracted from the ECG alone, and the pulse wave quality determining unit 101E determines that the pulse wave signal does not have the quality that allows the pulse wave feature to be extracted, the error processing unit 101Q determines that an error has occurred and terminates the biological state estimation process for blood pressure values, etc. Then, the error processing unit 101Q causes the display control unit 101L to display on the display unit 110 a message indicating that an error has occurred.

[0068] Furthermore, the quality of the electrocardiogram and pulse wave signals can be determined not only from the electrocardiogram and pulse wave signals, but also from the acceleration detected by acceleration sensor 114.

[0069] As described above, when an electrocardiogram has a quality that allows an electrocardiogram feature to be extracted only from the electrocardiogram, the biological state estimation device 10 according to this embodiment sets a search reference point for searching the electrocardiogram to extract the electrocardiogram feature based on the electrocardiogram, but when an electrocardiogram has a quality that does not allow an electrocardiogram feature to be extracted only from the electrocardiogram, the biological state estimation device 10 according to this embodiment sets a search reference point for searching the electrocardiogram by extracting a pulse wave feature detected by the sensor unit 230 of the pulse wave sensor. Since the electrocardiogram is thus searched based on the pulse wave feature, even when there is noise that is likely to affect the electrocardiogram but not the pulse wave signal, new feature can be extracted with high accuracy, and further, a biological state such as a blood pressure value can be estimated with high accuracy.

[0070] Here, a sensor unit 230 including electrodes 231A, 231B, 232A, and 232B; The control unit 101 functioning as the current application and voltage detection circuit 233 and the pulse wave measurement control unit 101B corresponds to the pulse waveform acquisition unit of the present invention. The electrode groups 230A-230F, the switch circuit 104, the subtraction circuit 105, the AFE 106, and the control unit 101 functioning as the electrocardiogram measurement control unit 101A correspond to the electrocardiogram waveform acquisition unit of the present invention. The control unit 101 functioning as the electrocardiogram quality determination unit 101D corresponds to the electrocardiogram waveform quality determination unit of the present invention. The control unit 101 functioning as the pulse wave-based search reference point setting unit 101G corresponds to the second search reference point setting unit of the present invention, and the reference point of the electrocardiogram search set by the pulse wave-based search reference point setting unit 101G corresponds to the second reference point of the present invention. The control unit 101 functioning as the electrocardiogram-based search reference point setting unit 101H corresponds to the first search reference point setting unit of the present invention, and the reference point of the electrocardiogram search set by the electrocardiogram-based search reference point setting unit 101H corresponds to the first reference point of the present invention.

[0071] (Electrocardiogram feature extraction method) FIG. 10 is a flowchart illustrating the operation of extracting electrocardiographic features in the biological state estimating device 10 according to this embodiment.

[0072] The following operation will be described assuming that the control unit 101 measures an electrocardiogram, a pulse waveform, and acceleration and stores them in the storage unit 102.

[0073] First, in step S1, it is determined whether the quality of the electrocardiogram is good, that is, whether the quality is such that electrocardiogram features can be extracted based on the electrocardiogram alone.

[0074] If it is determined in step S1 that the quality of the electrocardiogram is good, the process proceeds to step S2. In step S2, the peak point of the R wave is searched for in the electrocardiogram, and this is set as the search reference point, and the process proceeds to step S3.

[0075] If it is determined in step S1 that the quality of the electrocardiogram is not good, the process proceeds to step S4. In step S4, it is determined whether the quality of the pulse wave signal is good, that is, whether the quality is such that pulse wave features can be extracted based on the pulse wave signal.

[0076] If it is determined in step S4 that the quality of the pulse wave signal is good, the process proceeds to step S5. In step S5, a feature of the pulse wave is extracted and set as a search reference point. For example, the rising edge of the pulse wave is extracted and the time of the rising edge of the pulse wave is set as the search reference point, and the process proceeds to step S3.

[0077] Then, in step S3, electrocardiographic features are extracted using the search reference points set in step S2 or step S5.

[0078] If it is determined in step S4 that the quality of the pulse wave signal is not good, an error is determined, and the process is terminated. If an error is determined, the error process may be, for example, displaying a message indicating that an error has occurred. 110 Depending on the cause of the error, the belt 200 Alternatively, a message such as "put the device back on" or "take a correct posture for measurement" may be displayed on the display unit 110. [Explanation of symbols]

[0079] 10. Biological condition estimation device 101 Control section 104 Switch circuit 105 Subtraction circuit 106··AFE 220··Electrocardiogram sensor 230· ·S Nsa Department 233 Power supply and voltage detection circuit

Claims

1. an electrocardiogram waveform acquisition unit for acquiring an electrocardiogram waveform; an electrocardiogram feature extraction unit that searches the electrocardiogram waveform and extracts a feature of the electrocardiogram waveform; a pulse waveform acquiring unit for acquiring a pulse waveform; a pulse wave feature quantity extraction unit that searches the pulse waveform and extracts feature quantities of the pulse waveform; a biological condition estimating device for estimating a biological condition based on at least the electrocardiogram waveform feature quantity out of the electrocardiogram waveform feature quantity and the pulse waveform feature quantity, an electrocardiogram waveform quality determination unit that determines whether the electrocardiogram waveform has a quality that allows extraction of an electrocardiogram waveform feature quantity from the electrocardiogram waveform alone; a first search reference point setting unit that sets a first reference point for searching the electrocardiogram waveform when it is determined that the electrocardiogram waveform has a quality that allows extraction of a feature amount of the electrocardiogram waveform; a second search reference point setting unit that sets a second reference point for searching the electrocardiogram waveform based on the feature value of the pulse waveform when it is determined that the electrocardiogram waveform does not have a quality that allows extraction of a feature value of the electrocardiogram waveform; Equipped with The biological state estimation device, wherein the electrocardiogram feature extraction unit searches the electrocardiogram waveform based on the first reference point or the second reference point and extracts features of the electrocardiogram waveform for each beat.

2. a pulse waveform quality determination unit that determines whether the pulse waveform has a quality that allows a feature of the pulse waveform to be extracted, 2. The biological state estimation device according to claim 1, wherein the pulse wave feature quantity extraction unit extracts the feature quantities of the pulse waveform when it is determined that the pulse waveform has a quality that enables extraction of feature quantities of the pulse waveform.

3. The pulse wave feature amount extraction unit extracts a rising edge of the pulse waveform, 3. The biological state estimating device according to claim 1, wherein the second search reference point setting section sets a time of a rising edge of the pulse waveform as the second reference point.

4. The pulse wave feature amount extraction unit extracts a peak of the pulse waveform, 3. The biological state estimating device according to claim 1, wherein the second search reference point setting section sets a time of a peak of the pulse waveform as the second reference point.

5. the pulse wave feature amount extraction unit extracts a peak in a first derivative waveform calculated from the pulse waveform; 3. The biological state estimating device according to claim 1, wherein the second search reference point setting section sets, as the second reference point, a time of a peak in a first derivative waveform calculated from the pulse waveform.

6. the pulse wave feature amount extraction unit extracts a peak in a second derivative waveform calculated from the pulse waveform; 3. The biological state estimating device according to claim 1, wherein the second search reference point setting section sets, as the second reference point, a time of a peak in a second derivative waveform calculated from the pulse waveform.

7. 7. The biological condition estimating device according to claim 1, wherein a blood pressure value is estimated as the biological condition.

8. 8. The biological condition estimating device according to claim 1, wherein a heart rate is estimated as the biological condition.

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