KR102360073B1 - Blood pressure measuring apparatus, wrist watch type terminal having the same, and method of measuring blood pressure - Google Patents

Abstract

Disclosed are a blood pressure measuring device, a wrist watch type terminal, and a blood pressure measuring method.
The disclosed blood pressure measuring device includes a light source for irradiating light to a living body, a light receiving device for receiving light from the living body, and a processing device for calculating blood pressure according to a detection signal from the light receiving device. The processing device obtains a subtraction value for subtracting a moving average value of a second section longer than the first section from the moving average value of the first section of the detection signal, extracts a characteristic point of the pulse wave according to the subtraction value, and at the characteristic point The obtained characteristic quantity is converted into blood pressure.

Description

Blood pressure measuring apparatus, wrist watch type terminal having the same, and method of measuring blood pressure

The embodiment relates to a blood pressure measuring device, a wrist watch type terminal, and a blood pressure measuring method.

Patent Document 1 discloses a blood pressure measuring device that irradiates near-infrared light and detects the amount of reflected light from a blood vessel as a photoelectric pulse wave. The blood pressure measuring apparatus of Patent Document 1 includes a photoelectric sensor and a body movement sensor, and unnecessary frequency components are removed from the photoelectric sensor and the body movement sensor. The blood pressure is calculated by using the ratio of the output values of the photoelectric sensor and the pressure sensor as a calibration value.

1. Japanese Patent Laid-Open No. 2002-369805 In such a photoelectric blood pressure measuring device, the pulse wave is observed in a state in which the effect of white noise or the like or the AC component generated by the circuit is added to the original AC component of the pulse wave. Therefore, components other than the pulse wave of the living body become noise. In particular, when a blood pressure measuring device such as a wrist watch type other than a calf type is used as the blood pressure measuring device, the installation state of the blood pressure measuring device is changed due to a movement or disturbance of a subject to be measured. Therefore, the noise becomes large, and it becomes difficult to improve the measurement precision. In addition, it is difficult to measure the systolic blood pressure (SBP2) because the pulse wave changes are small.

The embodiment provides an apparatus and a measuring method capable of precisely measuring blood pressure.

A blood pressure measuring apparatus according to an embodiment includes: a light source for irradiating light to a living body; a light receiver for receiving light from the living body; and a processing device for measuring blood pressure based on the detection signal from the light receiver, wherein the processing device subtracts a moving average value of a second section longer than the first section from a moving average value of the first section of the detection signal and a subtraction unit for obtaining a subtracted value, an extracting unit for extracting pulse wave feature points based on the subtraction value, and a conversion unit for converting a feature amount calculated based on the feature points into blood pressure.

The processing device specifies one cycle of the pulse wave based on the subtraction value, extracts the characteristic point for each pulse wave cycle to obtain a plurality of characteristic quantities, and calculates the blood pressure from the plurality of characteristic quantities.

The processing device excludes a period from which the feature point cannot be extracted due to noise from the blood pressure calculation.

A blood pressure measuring apparatus according to another embodiment includes a sensor unit including a light source for irradiating light to a living body and a light receiving device for receiving light from the living body; and a processing device for extracting first and second feature points of the pulse wave based on the detection signal from the sensor unit, and converting a feature amount based on the first and second feature points into blood pressure,

The light source outputs a first detection signal based on light in a first wavelength band and a second detection signal based on light in a second wavelength band shorter than the first wavelength band,

In the first section of the pulse wave, the processing device extracts the first characteristic point based on the systolic posterior blood pressure (SBP2) based on the first detection signal. In a second section different from the first section, the second feature point is extracted based on the second detection signal, and the feature amount obtained based on the first feature point and the second feature point is converted into blood pressure.

The second section includes the maximum and minimum values of the pulse wave.

The light of the first wavelength band may be red light or infrared light, and the light of the second wavelength band may be green light.

The light source may alternately emit the light of the first wavelength band in the first section and the light of the second wavelength band in the second section.

The blood pressure measuring device may be provided in a wrist watch type terminal.

A blood pressure measurement method according to an embodiment includes: a light source irradiating light to a living body; a light receiver for receiving light from the living body; A blood pressure measuring method by a blood pressure measuring device comprising a; a processing device for measuring blood pressure based on the detection signal from the light receiver

obtaining a subtraction value for subtracting a moving average value of a second section longer than the first section from the moving average value of the first section of the detection signal;

extracting feature points of the pulse wave based on the subtraction value; and

and converting the feature amount calculated based on the feature point into blood pressure.

The first period may be one cycle of power used, and the second period may be one to five cycles of pulse waves.

A blood pressure measurement method according to another embodiment includes: a light source irradiating light to a living body; a sensor unit having a light receiver for receiving light from the living body;

A blood pressure measuring device having a processing device that extracts first and second feature points of the pulse wave based on the detection signal from the sensor unit, and converts a feature amount based on the first and second feature points into blood pressure In the blood pressure measurement method,

outputting a first detection signal based on light in a first wavelength band and a second detection signal based on light in a second wavelength band shorter than the second wavelength band;

In a first period of one cycle of the pulse wave, the first characteristic point based on the systolic posterior blood pressure (SBP2) is extracted based on the first detection signal, and in a second period different from the first period in the first period, the extracting the second feature point based on a second detection signal; and

and converting the feature quantity obtained based on the first feature point and the second feature point into blood pressure.

The blood pressure measuring apparatus and blood pressure measuring method according to the embodiment can remove noise by using the subtracted value of the moving average values, so that it is possible to measure the blood pressure with high precision.

A blood pressure measuring apparatus and blood pressure measuring method according to another embodiment calculates a characteristic point of systolic posterior blood pressure using a first wavelength suitable for measuring systolic posterior blood pressure, and the maximum blood pressure uses a second wavelength longer than the first wavelength to generate noise It is possible to measure blood pressure with high precision by calculating the feature points with reduced .

1 is a block diagram showing the configuration of a blood pressure measuring apparatus according to an embodiment.
2 is a graph showing an example of a detection signal detected by the sensor unit of the blood pressure measuring device according to the embodiment.
3A and 3B are graphs showing an example of a pulse wave from which noise is removed by a digital filter of the blood pressure measuring device according to the embodiment and its characteristic points.
4A and 4B are graphs showing a regression line for converting a feature amount of a feature point extracted from a pulse wave measured by a blood pressure measuring device according to an embodiment into a blood pressure.
5 is a flowchart illustrating a blood pressure measuring method according to an exemplary embodiment step by step.
6 is a block diagram illustrating a configuration of a blood pressure measuring apparatus according to another exemplary embodiment.
7 is a diagram for explaining a first period and a second period of a blood pressure measuring apparatus according to another exemplary embodiment.

Hereinafter, each embodiment will be described with reference to the drawings. In the description, like elements are denoted by the same reference numerals. Duplicate descriptions of equivalent components or homogeneous components are omitted.

<First embodiment>

It will be described with reference to FIG. 1, which is a block diagram showing the configuration of a blood pressure measuring apparatus according to an embodiment. The blood pressure measuring device 1 includes a sensor unit 10 , an analog front end (AFE) 20 , a processing device 30 , and a display unit 40 . The blood pressure measuring device 1 is, for example, a measuring device installed in a wearable terminal, and is mounted on the wrist of a person to be measured with a belt, like a wrist watch-type terminal. That is, by wrapping the band around the arm, the blood pressure measuring device 1 is in a state capable of measuring the blood pressure.

The sensor unit 10 includes a light source 11 and a light receiver 12 . The light source 11 is, for example, a light emitting device such as an LED (Light Emitting Diode), and generates green light, red light or infrared light (IR). The light from the light source 11 is irradiated to the living body.

The light receiver 12 is, for example, a photodetector such as a photodiode, a CCD (Charge Coupled Device), or a CMOS sensor (Complementary Metal Oxide Semiconductor Image Sensor), and is disposed adjacent to the light source 11 . The light receiver 12 receives the light from the living body, and outputs a detection signal corresponding to the intensity to the AFE 20 . Accordingly, the sensor unit 10 is a photoelectric sensor that detects a volumetric pulse wave corresponding to a change in the volume of a blood vessel.

Specifically, when the light of the light source 11 is irradiated to the living body, the light is scattered from the epidermis, dermis, capillary, peripheral blood vessel, fat, artery, etc. of the living body. The light receiver 12 detects scattered light from each part of the living body. The pulse flowing through the blood vessel moves with a period of a certain time, and a characteristic motion is observed in the intensity of scattered light (pulse wave) obtained from the pulse. That is, the intensity of scattered light represents a pulse wave. By analyzing this pulse wave, biomarkers such as blood pressure, blood oxygen concentration, and AI value (Augmentation index) can be obtained.

In the embodiment, the light source 11 generates red light or infrared light that easily passes through the epidermis or dermis of a living body. Accordingly, the intensity of scattered light scattered from the living blood vessel can be increased. The light receiver 12 may be arranged to receive light that has passed through the living body. In this case, the light source 11 and the light receiver 12 are disposed to face each other with the living body interposed therebetween.

The AFE 20 includes an amplifier 21 , a noise removal filter 22 , and an Analog Digital Converter (ADC) 23 . The amplifier 21 amplifies the detection signal from the sensor unit 10 . The noise removal filter 22 is an analog filter, and removes the noise of the detection signal amplified by the amplifier 21 by analog processing. The noise removal filter 22 is an LC filter such as a low-pass filter or a high-pass filter. The ADC 23 converts the detection signal from which the noise is removed by the noise removal filter 22 into a digital signal. Next, the ADC 23 outputs the detection signal converted into a digital signal to the processing device 30 . The ADC 23 outputs a digital value sampled at a predetermined sampling period as a detection signal.

The processing device 30 is, for example, a microcomputer, and includes a CPU (Central Processing Unit) 31 , a memory 32 , a digital filter 33 , and a power management unit 34 . The memory 32 stores a predetermined program. The CPU 31 reads and executes the program stored in the memory 32 . In this way, according to the signal detected by the AFE 20, the blood pressure (SBP, DBP) and the like can be measured. In order to measure the blood pressure, the CPU 31 performs a process for extracting a feature point and a process for converting a feature amount into a blood pressure, as described later. Accordingly, the CPU 31 includes an extraction unit 51 for extracting a feature point and a conversion unit 52 for converting a feature amount into a blood pressure, as shown in FIG. 1 . In addition, the processing device 30 may calculate a health index other than blood pressure, for example, an AI value.

The power management unit 34 controls the power supplied to the sensor unit 10 . For example, the power management unit 34 supplies a predetermined driving current to the light source 11 to cause the light source 11 to emit light with a predetermined intensity. In addition, the power management unit 34 may control the timing of supplying current to the light source 11 so that the light source 11 intermittently emits light at a predetermined timing.

2 shows a detection signal output from the AFE 20 . As shown in FIG. 2 , a pulse wave according to blood vessel pulsation is repeatedly displayed as a detection signal. In addition, the detection signal includes white noise or circuit noise generated from an electronic circuit or the like. The digital filter 33 performs digital processing for removing noise components from the detection signal. Then, the CPU 31 measures the blood pressure according to the detection signal from which the noise is removed by the digital filter 33 .

The digital filter 33 obtains a moving average of the detection signal. The moving average value a(n) at a certain time t(n) is obtained by adding up all the data in the period before and after [t(n-m)-t(n+m)] centered on the certain time t(n). , is the value obtained by dividing the added value by 2m+1. First, the digital filter 33 calculates the moving average value of the first section corresponding to the frequency of the power source as the first moving average value. For example, a section corresponding to one cycle of the commercial power supply (50 Hz or 60 Hz) is set as the first section, and the digital filter 33 obtains an average of digital values included in the first section.

Next, the digital filter 33 calculates the moving average of the second section longer than the first section as the second moving average. For example, the second interval is set according to the pulse. A section longer than one pulse is set as the second section. Here, as a specific example, a section corresponding to one period of 0.47 Hz may be set as the second section. That is, the digital filter 33 obtains an average of digital values included in 1/0.47 Hz. Since the second section is longer than the first section, the number of data included in the second section is greater than the number of data in the first section. Accordingly, the second moving average value has less variation than the first moving average value.

Then, the digital filter 33 becomes a subtraction unit that calculates a subtraction value obtained by subtracting the second moving average value from the first moving average value. 3A shows an example of a waveform of a subtraction value calculated from a first moving average value and a second moving average value. 3A is a graph showing an example of a subtracted value and a feature point extracted by the subtracted value. 3A is an enlarged view of a portion of an ideal pulse wave. 3B shows a pulse wave acquired by red light, a pulse wave acquired by green light, and a difference therebetween, respectively. Here, the following arithmetic processing is performed using the red light acquisition result. It is also possible to use infrared light instead of red light.

The processing device 30 may specify one cycle of the pulse wave from the period in which the subtraction value becomes positive , as shown in FIGS. 3A and 3B . In the following description, a pulse wave of one cycle is referred to as a single pulse wave. The processing device 30 may set the timing at which the subtraction value becomes positive from negative as the starting point of the pulse wave.

Then, the extraction unit 51 of the processing device 30 extracts the feature points of the pulse wave according to the subtracted value. The processing apparatus 30 extracts, for example, a maximum value, a minimum value, a local maximum, a minimum value, an inflection point, etc. as a feature point for every pulse wave. The processing device 30 calculates the value and time of the feature point from the waveform of the subtracted value. For example, the processing device 30 calculates the characteristic point by obtaining the undecomposed velocity pulse wave of the pulse wave or obtaining the second undecomposed acceleration pulse wave. 3 shows an example of the feature points extracted by the processing device 30 .

In FIG. 3 , the first peak (maximum value) in one cycle is the systolic peak, and the second peak (maximum value) is the Reflective peak. After the second peak, the minimum value becomes a notch indicating the boundary between systolic and diastolic. S.Time is the time from the start point of one cycle to the systolic peak. The time from the start point of one cycle to the reflection peak is R. Time. The time from the start point of one cycle to the notch is referred to as the notch time. The processing device 30 extracts the minimum value of one cycle as a feature point. In this way, the processing device 30 calculates values and times at a plurality of feature points. In addition, in the embodiment, the maximum value, the minimum value, etc. may be corrected based on the subtraction value from the notch.

The processing device 30 calculates a feature amount from values and time of a plurality of feature points included in the pulse wave. The characteristic quantity is a number for calculating blood pressure (SBP, DBP), and is a number derived from the value and time of the characteristic point in the pulse wave. The feature quantity can be calculated according to a preset calculation formula. The feature quantity is a value that changes according to a change in blood pressure, and the blood pressure can be precisely measured by using a value that greatly changes with the change in blood pressure. In addition, in the feature point, the subtracted value may be referred to as the feature amount as it is. Here, in order to obtain SBP and DBP, two calculation expressions are prepared.

Then, the conversion unit 52 of the processing device 30 converts the feature amount into blood pressure. The conversion unit 52 converts the feature amount into a blood pressure value using a regression line. Here, two regression lines are stored in the memory 32 to calculate SBP (systolic blood pressure: BP_MAX) and DBP (diastolic blood pressure: BP_MIN) as shown in FIGS. 4A and 4B . Then, the processing device 30 calculates the feature amount for SBP and the feature amount for DBP based on the pulse wave. The processing device 30 calculates SBP from a predetermined feature amount using the regression line for SBP. In addition, the processing device 30 calculates DBP from other feature quantities using the regression line for DBP. In this way, the blood pressure is measured with the blood pressure measuring device. The extracted feature points and the calculation formula for obtaining the feature quantity from the feature points are optimized by a known method. That is, a feature point and a calculation formula capable of precisely measuring blood pressure are set.

A regression line is set using pre-acquired multiple measurement results. That is, for a plurality of subjects to be measured, a characteristic quantity is obtained with the blood pressure measuring device according to the embodiment, and blood pressure values are measured with a conventional Calf blood pressure monitor. In this way, a database corresponding to the characteristic quantity and the blood pressure value is constructed. Then, a regression analysis is performed on the data recorded in the database to obtain a regression line. The regression line may be set for each sex and age. For example, you may set by age for each gender, such as a 20-year-old male, a 20-year-old female, a 30-year-old male, and a 30-year-old female. That is, after acquiring data for each age and gender, the database may be built. In addition, the processing device 30 may convert the feature amount into blood pressure using a regression curve using a polynomial of a second order or higher as well as a regression straight line.

Also, the processing device 30 may calculate the blood pressure based on the plurality of pulse waves. For example, the processing device 30 extracts a characteristic point for each of n pulse waves (n is an integer of 2 or more), and calculates a characteristic quantity. As a result, since a feature amount is calculated for each pulse wave, n feature amounts are calculated. Then, the processing device 30 converts each of the n feature quantities into blood pressure (SBP or DBP) using the regression line. Thereby, n blood pressure values are calculated. Then, the average value of the n blood pressure values can be used as the blood pressure. In this way, when the feature amount is calculated based on the plurality of pulse waves, the measurement accuracy can be improved.

Alternatively, the blood pressure may be obtained by excluding a part of the n blood pressure values. For example, the blood pressure may be an average of (n-2) blood pressure values excluding the maximum and minimum values among the n blood pressure values. Accordingly, the measurement accuracy can be improved. Also, pulse waves having a characteristic quantity or characteristic point value significantly different from other pulse waves may be excluded from the calculation of the blood pressure.

A pulse wave (one cycle) from which a feature point cannot be extracted may be excluded from the calculation of blood pressure. For example, if the maximum and minimum values necessary for calculating the feature amount are buried in the noise due to the influence of noise or the like and cannot be calculated, the feature amount cannot be calculated for the period. Therefore, it is preferable not to convert the blood pressure for the pulse wave (period) from which the feature point cannot be extracted. In this way, the measurement accuracy of blood pressure can be improved.

In this way, the processing device 30 estimates the tendency of the rise and fall of the pulse wave based on the subtracted value, and estimates the maximum value, the minimum value, the maximum value, the minimum value, the inflection point, etc. as the feature points. In addition, the processing device 30 may calculate a feature amount from a plurality of feature points for each pulse wave. The processing device 30 may convert the feature amount into a blood pressure value using a straight line preset by the database.

The display unit 40 includes a display monitor such as a liquid crystal display. The display unit 40 displays the waveform of the blood pressure or pulse wave calculated by the processing device 30 .

In the blood pressure measuring apparatus of the embodiment, a subtraction value between the moving average value of the first section and the moving average value of the second section is used. In this way, the influence of scattering noise other than disturbance light, vibration, and pulse can be reduced. Accordingly, the measurement accuracy of blood pressure can be improved by appropriately extracting the feature points. In addition, a section corresponding to the frequency (50 Hz or 60 Hz) of commercial power may be used as the section of the first moving average value. In this way, power supply noise is reduced.

In addition, the digital filter 33 performs digital processing to reduce noise. Therefore, compared with an analog filter, it is possible to make a blood pressure measuring device simply. For example, when removing noise with an analog filter, it is necessary to avoid the influence of LC filter oscillation, so it is necessary to design a circuit for each model. In the embodiment, since noise is removed by digital signal processing by a computer program, it can be developed simply.

In addition, the processing device 30 specifies one cycle (single pulse wave) of the pulse wave using the subtracted value. That is, the start timing of one cycle is specified at the timing when the subtraction value becomes 0. Thereby, a characteristic quantity can be calculated|required more suitably. For example, since the time to the feature point can be precisely calculated, an appropriate feature quantity can be calculated. Based on the detection signal of one light receiver 12, a first moving average value and a second moving average value are obtained. In this way, it is also possible to appropriately estimate the noise level. Moreover, it also becomes possible to measure with higher precision. If the moving average is frequently calculated and the subtracted value is obtained, even when the noise fluctuates, measurement can be performed with high accuracy.

A method for measuring blood pressure according to an embodiment will be described with reference to FIG. 5 . 5 is a flowchart illustrating a blood pressure measurement method.

First, the measurement subject (living body) mounts the blood pressure measuring device 1 on, for example, the wrist, and receives light from the living body (wrist) with the light receiver 12 (S1). The light receiver 12 photoelectrically converts a signal indicating the intensity of the received light and outputs it to the AFE 20 .

Next, the AFE 20 processes the detection signal input from the sensor unit 10 (S2). As described above, the amplifier 21 of the AFE 20 amplifies the detection signal. Then, the noise removal filter 22 filters the detection signal and removes the noise. ADC 23 converts the detection signal to AD.

The digital filter 33 performs digital filter processing on the detection signal (S3). That is, a subtraction value between the first moving average value and the second moving average value is obtained, and noise is removed. Also, the period can be specified by the subtracted value.

The processing device 30 extracts a feature point based on the subtracted value (S4). For example, the processing device 30 extracts the feature point by differentiating the pulse wave indicated by the subtracted value or differentiating it twice. Here, the processing device 30 extracts a feature point for each pulse wave. Then, for each pulse wave, the processing device 30 calculates a feature amount based on the value and time of the feature point (S5). That is, the value and time of the feature point are converted into a feature quantity using a preset calculation formula. For a pulse wave from which a characteristic point cannot be extracted, a characteristic quantity is not calculated.

Then, the processing device 30 converts the feature amount into blood pressure using the regression line (S6). The processing device 30 calculates SBP and DBP. The display unit 40 displays the obtained blood pressure (S7). By performing such a process, the above-mentioned effect can be acquired.

Moreover, when it is desired to measure biometric information other than blood pressure, it is sufficient to set a calculation formula and a regression line for obtaining a characteristic quantity according to the measured biometric information. For example, when it is desired to measure the blood oxygen concentration, a calculation formula for calculating the characteristic quantity is set from the characteristic points to be obtained and the values of the characteristic points. For a plurality of measurement subjects, blood oxygen concentration is measured in advance and a database is built. Then, according to the database, a regression line is obtained. In this way, the blood oxygen concentration can be measured by the blood pressure measuring device 1 .

<Second embodiment>

A blood pressure measuring device according to the embodiment will be described with reference to FIG. 6 . 6 is a block diagram illustrating a configuration of a blood pressure measuring apparatus according to an embodiment. In the embodiment, a feature point corresponding to the systolic posterior blood pressure (SBP2) is extracted. SBP2 is systolic post-systolic blood pressure, and corresponds to the second peak of systolic (Reflective Peak) of FIG. 3 . SBP2 is a characteristic point that exists after the systolic blood pressure (SBP) of the pulse wave and before the notch, and is used as an important index of biometric information from which the hardness of blood vessels (AI value) and the like can be derived. However, it is difficult to extract SBP2 because the change in the pulse wave is small.

Hereinafter, a configuration for extracting the feature points of SBP2 will be described. In the embodiment, in order to extract the feature points of SBP2, two light sources 11a and 11b are installed in the sensor unit 10 . Since the basic configuration and processing of the blood pressure measuring device are the same as those of the first embodiment, a description thereof will be omitted.

In this embodiment, the sensor unit 10 includes a first light source 11a and a second light source 11b. The first light source 11a emits light in a first wavelength band (eg, a wavelength of 600 nm or more and 1100 nm or less). The second light source 11b emits light of a second wavelength band shorter than the first wavelength band (eg, a wavelength of 480 nm or more and 560 nm or less). The light of the first wavelength band is, for example, red light or infrared light, and the light of the second wavelength band is green light. The first wavelength band and the second wavelength band are not limited to being completely different, and may partially overlap.

The power management unit 34 causes the first light source 11a and the second light source 11b to emit light at different timings. For example, the power management unit 34 alternately emits light from the first light source 11a and the second light source 11b. Accordingly, the first light source 11a and the second light source 11b emit light intermittently, and the light emission period is the same and the phases are different.

The first light source 11a and the second light source 11b are disposed adjacent to each other. The first light source 11a and the second light source 11b irradiate light toward substantially the same part of the living body. The light receiver 12 detects the scattered light from the light-irradiated area. The light receiver 12 has sensitivity to light in the first wavelength band and the second wavelength band. That is, when the light source 11a emits infrared light, the light receiver 12 can detect from infrared light to green light. When the light source 11a emits red light, the light receiver 12 may detect light in a wavelength range from red light to green light.

When irradiating light to a living body, the depth of reach differs depending on the wavelength, so the biometric information to be obtained is different. For example, green light has a high rate of scattering at a depth up to the surface of the dermis. On the other hand, red light or infrared light has a high rate of scattering through the dermis to the depth of the arteries. That is, infrared light or red light has little absorption into a living body and is easily transmitted. When infrared light or red light is used, scattered light in the arteries increases. Since infrared light or red light has a deep reach, more information can be obtained. However, peripheral blood vessels and fat in the epidermis, dermis, etc. other than the arteries have little influence as noise. This noise makes it difficult to analyze the scattered light and prevents the acquisition of precise biometric information. On the other hand, since green light has a shallow reaching depth, noise caused by scattered light from a region or the like is small.

In this embodiment, green light and red light or infrared light having a longer wavelength than green light are used separately. Specifically, in the first period of the pulse wave, light (red light or infrared light) of the first wavelength band is used, and in the second period, light (green light) of the second wavelength band is used. The sensor unit 10 alternately emits light in the first wavelength band and light in the second wavelength band. Accordingly, it is possible to perform measurements at different wavelengths with a simple configuration.

The light emission timing of the 1st light source 11a and the 2nd light source 11b is demonstrated using FIG. Fig. 7 is a diagram showing light emission timing in a pulse wave. The pulse wave may be divided into two periods, a first period Tr and a second period Tg. The first period Tr is an emission period of red light or infrared light. In the first period Tr, the first light source 11a is turned on and the second light source 11b is turned off. The second period Tg is a green light emission period. In the second period Tg, the first light source 11a is turned off and the second light source 11b is turned on. The first period Tr and the second period Tg are repeated. The light of the first wavelength band and the light of the second wavelength band are detected by the same light receiver 12 . The ADC 23 converts the detection signal into a digital value at a predetermined sampling period.

The second period Tg includes the maximum and minimum values of the pulse wave. That is, the second period Tg is a period including the feature point (maximum value) based on the SBP and the feature point (minimum value) based on the DBP. In the second period Tg, the timing before the minimum value is the head, and the timing after the maximum value is the end. The first period Tr is a period from which the end timing of the second period Tg is taken as the start timing and continues only for a predetermined time therefrom. The end timing of the first period Tr is the beginning timing of the second period Tg. The first period Tr is a period including the feature point based on SBP2. In FIG. 7 , the second period Tg is longer than the first period Tr, but the second period Tg may be shorter than the first period Tr.

The maximum and minimum values of the pulse wave are easy to extract. Accordingly, even when green light having a weak intensity of scattered light from an artery is used, it is possible to easily extract feature points based on SBP and DBP. On the other hand, the feature points based on SBP2 can also be called local minima, maximal value, and inflection point, and it is difficult to extract. Accordingly, light in the first wavelength band is used to extract the feature points of SBP2. In the light of the first wavelength band, since the intensity of scattered light in the artery is high, the characteristic point of SBP2 is likely to appear as a local maximum. The processing device 30 extracts the feature point corresponding to SBP2 relatively easily.

In the present embodiment, light in the first wavelength band is detected in the first period Tr including the feature point of SBP2. The processing device 30 extracts the feature points of SBP2 according to the light of the first wavelength band. In other words, the feature point of SBP2 is extracted without using light in the second wavelength band. By using the light of the first wavelength band, the intensity of scattered light increases, so that the characteristic points of SBP2 can be easily extracted. For example, for SBP2 extraction, there is no need to differentiate the pulse wave in two stages or perform other data analysis.

Hereinafter, an example of a processing method for extracting feature points of SBP2 will be described. During the pulse wave cycle of FIG. 3 , data adjacent to each other are subtracted using data of the first period Tr. Then, the absolute value of the calculated value is taken, and a period in which the vicinity of 0 is calculated a lot is extracted. Counting from the beginning of the period, the second time of the period in which the vicinity of 0 is calculated a lot can be regarded as R.Time, and data near that time can be regarded as SBP2. In this way, the characteristic quantity of SBP2 is calculated|required.

In addition, the processing device 30 extracts the maximum and minimum values of the pulse wave based on the light in the second wavelength band. The feature point based on SBP and the feature point based on DBP are extracted without using light in the first wavelength band. Extraction of maximum and minimum values from the pulse wave is easy. Moreover, noise becomes small in green light. Accordingly, even when green light having a small intensity of scattered light from the artery is used, the processing device 30 may precisely extract the feature point.

As in the first embodiment, the processing device 30 calculates the blood pressure from the feature points. The processing device 30 obtains a feature amount from a plurality of feature points extracted as a pulse wave. Then, the processing device 30 converts the feature amount into blood pressure using the regression line. What is necessary is just to set the regression curve according to the database when the light of the 1st wavelength band and the light of the 2nd wavelength band are used. That is, when light in the first and second wavelength bands is alternately irradiated, a database in which the characteristic quantity and the pulse measurement value are matched is constructed, and a regression line is obtained using the database.

For n periods (n is an integer of 2 or more) of the pulse wave, the processing device 30 calculates a characteristic amount for each period. Thereby, n blood pressure values are obtained. Then, n blood pressure values are averaged using n as a parameter. In this way, blood pressure can be accurately measured.

Also, as in the first embodiment, a pulse wave from which a characteristic point cannot be extracted or a pulse wave having a very different magnitude of a characteristic quantity can be excluded from the calculation of the blood pressure. In this embodiment, the feature point of SBP2 is extracted by the detection signal based on the first wavelength band. Therefore, the feature points of SBP2 are precisely extracted. A pulse wave from which the feature point of SBP2 cannot be extracted or a pulse wave with very different feature points of SBP2 may be excluded. Therefore, it is possible to precisely measure in a short time.

In addition, the AI value can be obtained using the feature points of SBP2. For example, on the wrist, the AI value can be obtained from the formula below.

AI=SBP2/SBP (highest point of pulse wave)×100

Regarding the setting of the first period Tr and the second period Tg, a plurality of pulse waves may be measured in advance and then appropriately set. For example, a plurality of pulse waves of the measurement target may be measured, and the processing device 30 may obtain a period of the pulse waves. And, the timing at which the processing device 30 becomes a maximum value and a minimum value for every pulse wave can be calculated|required. Then, a period including the maximum value and the minimum value is set as the second period. Then, a period other than the second period is set as the first period.

In this embodiment, light of a different wavelength band within the pulse wave is used. That is, the pulse wave is divided into a first period and a second period to irradiate light of different wavelength bands. In this way, the feature point can be precisely extracted. In particular, it is possible to easily extract the feature points of SBP2. Accordingly, blood pressure can be precisely measured.

In addition, since the light sources 11a and 11b are alternately emitted light, the common light receiver 12 outputs a first detection signal based on the first wavelength band and a second detection signal based on the second wavelength band. That is, one light receiver 12 outputs a first detection signal based on the first wavelength band for the first period Tr, and outputs a second detection signal based on the second wavelength band for the second period Tg do. In this way, since the light receiver 12 and the AFE 20 are each constituted by one, the equipment configuration can be simplified.

In the above description, two light sources 11a and 11b having different emission colors are provided, however, two light receivers 12 may be provided. That is, a first light receiver for receiving light in the first wavelength band and a second light receiver for receiving light in the second wavelength band may be provided in the sensor unit 10 . In other words, a first light receiver having no sensitivity in the second wavelength band and a second light receiver having no sensitivity in the first wavelength band may be provided. Then, one light source 11 that emits light in the first and second wavelength bands is provided, and the two light receivers can receive light in each wavelength band. In this case, the light source may be a white light source. Alternatively, two light sources and two light receivers may be provided respectively. In this case, the first light source and the first light receiver corresponding to the first wavelength band, and the second light source and the second light receiver corresponding to the second wavelength band may be provided.

As for the second embodiment, processing may or may not be performed by the digital filter 33 shown in the first embodiment. That is, as shown in the first embodiment, the feature point may be extracted based on the subtraction value of the two moving averages, or the feature point may be extracted based on a detection signal that has not been subjected to digital filter processing.

It is also possible to assemble the blood pressure measuring device 1 according to the first and second embodiments to a wearable terminal such as a wrist watch type terminal. The embodiments may be referred to as a wrist watch-type terminal equipped with the blood pressure measuring device 1 . Since the sensor unit 10 is installed in a wristwatch-type terminal and has a wireless communication unit, other components (eg, the processing device 30, the display unit 40, etc.) may be provided in the smart phone. In this case, analog data or digital data acquired by the wristwatch-type terminal is transmitted to the smart phone by wireless communication. Incidentally, the smartphone receiving the data may perform part or all of the processing for measuring the blood pressure.

As mentioned above, although the invention was demonstrated with reference to an Example, this invention is not limited by the above. Various changes which can be understood by those skilled in the art can be made within the scope of the present invention in the configuration and detailed description of the present invention.

1: blood pressure measuring device 10: sensor unit
11: light source 12: receiver
20: AFE 21: Amplifier
22: noise removal filter 23: ADC
30: processing unit 31: CPU
32: memory 33: digital filter
34: power management unit 40: display unit
51: extraction unit 52: conversion unit

Claims (20)

a light source for irradiating light to a living body;
a light receiver for receiving light from the living body; and
a processing device for measuring blood pressure based on the detection signal from the light receiver;
The processing device comprises: a subtraction unit for obtaining a subtraction value for subtracting a moving average value of a second section longer than the first section from a moving average value of a first section of the detection signal;
an extraction unit for extracting pulse wave feature points based on the subtraction value;
and a conversion unit that converts the feature quantity calculated based on the feature point into blood pressure,
The processing device specifies one cycle of the pulse wave based on the subtraction value,
Extracting the feature point for each pulse wave period to obtain a plurality of the feature quantity,
calculating the blood pressure from the plurality of feature quantities,
The first section is one cycle of the power used,
The second section is a blood pressure measuring device of one cycle or more of a pulse wave. delete The method of claim 1,
The processing device excludes a period from which the feature point cannot be extracted due to noise from the blood pressure calculation. delete delete delete delete A wrist watch-type terminal having the blood pressure measuring device according to any one of claims 1 to 3. a light source for irradiating light to a living body; a light receiver for receiving light from the living body; A method for measuring blood pressure by a blood pressure measuring device including a processing device for measuring blood pressure based on the detection signal from the light receiver,
obtaining a subtraction value for subtracting a moving average value of a second section longer than the first section from the moving average value of the first section of the detection signal;
extracting feature points of the pulse wave based on the subtraction value; and
Converting the feature quantity obtained based on the feature point into blood pressure,
The first section is one cycle of the power used,
The second section is a blood pressure measuring method of one cycle or more of a pulse wave. 10. The method of claim 9,
The second section is a blood pressure measuring method of 1 to 5 cycles of the pulse wave. The method of claim 9, wherein the extracting of the feature points of the pulse wave comprises:
specifying one cycle of the pulse wave based on the subtraction value, extracting the characteristic point for each pulse wave cycle to obtain a plurality of characteristic quantities, and averaging the plurality of characteristic quantities. The method of claim 11, wherein the extracting of the feature points of the pulse wave comprises:
A blood pressure measuring method in which the one cycle of the pulse wave is a starting point of the pulse wave at a timing when the subtraction value becomes positive from negative. The method of claim 11, wherein the extracting of the feature points of the pulse wave comprises:
and extracting the maximum, minimum, maximum, minimum, and inflection points of the pulse wave. The method of claim 13, wherein the extracting of the feature points of the pulse wave comprises:
A blood pressure measurement method in which a period in which at least one of the characteristic points cannot be extracted due to noise is excluded from the blood pressure conversion. delete delete delete delete delete delete

Images