JP2008279185A - Blood pressure measuring apparatus, program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blood pressure measuring apparatus capable of obtaining high measurement accuracy by a simple method. <P>SOLUTION: In a step 100, whether or not to utilize body feature information is judged. In a step 120, impedance is measured. In a step 130, an electrocardiogram and pulse waves are simultaneously measured. In a step 140, electrocardiographic signals and pulse wave signals obtained by measurement are analyzed and a feature amount is calculated. In a step 150, the propriety of the electrocardiographic signals and the pulse wave signals is confirmed. In a step 160, the impedance is measured again. In a step 170, a difference between the measured value of the impedance in the first time and the measured value of the impedance in the second time is confirmed. In a step 180, an operational expression (3) is utilized, the pulse wave propagation time (PTT), speed pulse waves (a1) and the impedance (Z) obtained in the processing of the respective steps are used and a blood pressure is calculated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a blood pressure measurement device mounted on a vehicle, for example, and capable of measuring blood pressure such as a driver without using a cuff or the like.

  Conventionally, when measuring blood pressure, both the auscultation method and the oscillometric method require tightening with a cuff, the device becomes larger, the subject is suffering, and continuous blood pressure measurement is required. There were problems such as being unable to do so.

On the other hand, in recent years, a measurement method for calculating blood pressure using a pulse wave velocity and a pulse wave feature amount has been studied (see Patent Documents 1 to 9). For example, a volume pulse wave can be measured using light, so that the apparatus can be miniaturized, the pain of the subject can be eliminated, and continuous blood pressure measurement can be performed.
JP-A-10-295656 Japanese Patent Laid-Open No. 10-295657 Japanese Patent Laid-Open No. 11-318837 JP-T-2001-504362 Special table 2003-555 gazette Special table 2003-527149 gazette Japanese Patent Laid-Open No. 2001-8907 JP 2006-263354 A JP 2006-6897 A

  However, in the case of the techniques described in any of the cited references, personal adaptation is basically required in order to increase measurement accuracy. In other words, in order to improve accuracy, it is necessary to input personal feature amounts (personal feature information) such as body weight to the measuring device by himself, which is troublesome.

  In addition, when inputting personal characteristic information such as weight, if old (new) data is not known, old data or estimated data may be input, and correct data is not input. In this case, there is a problem that the measurement accuracy is lowered.

  In view of the above points, an object of the present invention is to provide a blood pressure measurement device that can obtain high measurement accuracy by a simple method.

  (1) The invention of claim 1 (blood pressure measuring device) uses the biological information obtained from at least one of an electrocardiogram signal and a pulse wave signal detected from a living body and the impedance detected from the living body to measure blood pressure. It is characterized by calculating.

In the present invention, since the blood pressure is obtained using an electrocardiogram signal or a pulse wave signal without using a cuff or the like, there is an advantage that the burden on the measurer is small.
In particular, according to the present invention, when calculating blood pressure, not only data obtained from an electrocardiogram signal or pulse wave signal but also impedance corresponding to personal characteristic information is used. High measurement accuracy can be obtained without input.

  That is, as is clear from the experimental examples described later, since there is a correlation between the body weight and the impedance, the blood pressure can be accurately calculated without using the body weight or the like by using the impedance. Thereby, problems (for example, time-consuming and incorrect data input) when inputting personal characteristic information manually can be avoided.

  Note that not only the impedance itself but also a value corresponding to the impedance calculated from the impedance (impedance-corresponding value) is within the scope of the present invention. For example, since there is a correlation between impedance and body fat, the use of body fat instead of impedance is also within the scope of the present invention.

  (2) In the invention of claim 2, the biological information includes pulse wave propagation time (PTT), pulse wave velocity (PWV), electrocardiogram QT time, pulse wave AI, velocity pulse wave, and acceleration pulse wave. Of these, at least one type is characterized.

The present invention exemplifies biological information.
Among these, the pulse wave propagation time (PTT) is a time difference between the R wave of the electrocardiogram and the pulse wave measured with a finger, and can be obtained from the electrocardiogram signal and the pulse wave signal. The pulse wave velocity (PWV) is the length of the blood vessel / PTT and can be obtained from the electrocardiogram signal and the pulse wave signal. The QT time of the electrocardiogram can be obtained from the electrocardiogram signal as shown in FIG. As shown in FIG. 4, the pulse wave AI (Augmentation Index) is a ratio (P2 / P1) of the magnitude of the reflected wave (P2) and the traveling wave (P1) in the pulse wave, and can be obtained from the pulse wave. it can. The velocity pulse wave is the first derivative of the pulse wave signal, and the acceleration pulse wave is the second derivative of the pulse wave signal, both of which can be obtained from the pulse wave signal.

(3) The invention of claim 3 is characterized in that the impedance is detected before and / or after the detection of the biological information.
Thereby, the validity of the impedance value can be evaluated.

(4) The invention of claim 4 is characterized in that the impedance is detected using a plurality of frequencies.
The present invention exemplifies an impedance detection method, and by measuring the impedance by changing the frequency, it is possible to eliminate the influence of individual differences and perform measurement with higher accuracy.

(5) The invention according to claim 5 is characterized in that at the time of calculating the blood pressure, at least one kind of body characteristic information among height, weight, age, and sex is further used.
As described above, blood pressure can be measured with high accuracy by using an electrocardiogram signal, a pulse wave signal, and impedance, but the measurement accuracy can be further improved by further inputting body characteristic information.

(6) The invention of claim 6 is characterized in that switching between using and not using the body feature information is possible.
This makes it possible to perform optimum measurement according to the situation, such as when priority is given to simplicity or priority is given to accuracy.

(7) In the invention of claim 7, an interface for inputting at least one of the four types of body characteristic information is provided.
For example, body feature information can be input to the blood pressure measurement device through an interface such as a touch panel or a remote controller.

(8) The invention of claim 8 is characterized in that the electrocardiogram signal and impedance are measured using the same electrode.
Thereby, the apparatus can be simplified.

  (9) The invention of claim 9 is characterized in that the two modes of voltage measurement for obtaining the electrocardiogram signal and impedance measurement for obtaining the impedance are automatically switched.

Thereby, an electrocardiogram signal and impedance can be acquired automatically.
(10) The invention of claim 10 is characterized in that body fat is calculated and reported using the impedance.

Since body fat is usually calculated using impedance, the calculated body fat can be displayed on, for example, a display, or notified by voice or the like using a speaker.
(11) The invention of claim 11 is characterized in that the blood pressure measurement device is mounted on a vehicle.

Therefore, blood pressure can be measured when a driver or the like gets on.
(12) The invention of claim 12 is characterized in that the electrode used for detecting the biological information is attached to a steering of a vehicle.

  Since the electrode used for detecting the electrocardiogram signal and impedance is attached to the steering wheel, the electrocardiogram signal and impedance can be automatically measured only by the driver touching the steering wheel. If a pulse wave sensor is attached to the steering, a pulse wave signal can also be acquired.

(13) The invention of claim 13 is a program characterized by having means for realizing the function of the blood pressure measurement device according to claim 1 or 2.
Therefore, by executing this program with a microcomputer or the like, it is possible to calculate blood pressure using a predetermined arithmetic expression using biological information and impedance.

(14) The invention of claim 14 is a computer-readable recording medium on which the program of claim 13 is recorded.
Therefore, the blood pressure can be calculated as described above using the program recorded on the recording medium.

Next, the best mode (embodiment) of the present invention will be described.
[First Embodiment]
In the present embodiment, a blood pressure measurement device that is mounted on an automobile and measures the blood pressure of a driver will be described.

a) First, the system configuration of the blood pressure measurement device according to the present embodiment will be described.
As shown in FIG. 1, in this embodiment, a blood pressure measurement device 1 mounted on an automobile, a notification device 3 that notifies information to a driver and the like, a manual input unit 5 that manually inputs data, A pulse wave sensor 9 attached to the steering 7 and a pair of electrodes 11 and 13 attached to the steering 9 are provided.

  The blood pressure measurement device 1 is an electronic control device centered on a well-known microcomputer. Based on signals from the pulse wave sensor 9 and the electrodes 11 and 13, body fat calculation, blood pressure calculation, and notification device 3. Control.

The notification device 3 includes a display 15 such as a liquid crystal that displays blood pressure and body fat, and a speaker 17 that outputs the contents of the display 15 by voice or the like.
The manual input unit 5 is an input device such as a keyboard, a numeric keypad, or a remote controller that can manually input individual body characteristic information such as weight, height, age, and sex. Note that data may be input using the display screen of the display 15 as a touch panel.

  The pulse wave sensor 9 is an optical sensor provided with a well-known light emitting element (LED) or light receiving element (PD). For example, the pulse wave sensor 9 irradiates light on a fingertip of a driver and uses the reflected wave to pulse wave. Can be detected. Therefore, a pulse wave signal used for blood pressure calculation described later can be obtained from the pulse wave sensor 9.

  The pair of electrodes 11 and 13 are arranged on the left and right of the steering wheel 9 so as to come into contact with the left and right hands of the driver, respectively. The electrodes 11 and 13 are used as electrodes of an electrocardiograph that applies a voltage in order to obtain an electrocardiogram signal, and are also used as electrodes of a body fat meter through which a current flows to obtain body fat. Here, both the electrodes 11 and 13 and the blood pressure measurement device 1 function as an electrocardiograph and a body fat meter.

  Therefore, an electrocardiographic signal used for blood pressure calculation described later can be obtained by using these electrodes 11 and 13. Moreover, although an electric current is sent between a pair of electrodes 11 and 13 and impedance is obtained by it, body fat can be calculated | required from the impedance, weight, etc. FIG.

b) Next, functions of the blood pressure measurement device and the like of this embodiment will be described in more detail with reference to block diagrams.
As shown in FIG. 2, the blood pressure measurement device 1 of the present embodiment includes an impedance measurement unit 21, an electrocardiogram / impedance measurement switching unit 23, an electrocardiogram signal acquisition unit 25, a pulse wave signal acquisition unit 27, A body fat calculation unit 29, an electrocardiogram signal analysis unit 31, an electrocardiogram and pulse wave signal analysis unit 33, a pulse wave signal analysis unit 35, and a blood pressure calculation unit 37 are provided.

  Among these, the impedance measuring unit 21 measures impedance by flowing a minute current (for example, alternating current of a plurality of high and low frequencies) between the electrodes 11 and 13. The electrocardiogram signal acquisition unit 25 measures the electrical excitement associated with the heart activity as a potential difference (electrocardiogram signal) between the electrodes 11 and 13.

The electrocardiogram / impedance measurement switching unit 23 automatically switches the functions of the impedance measurement unit 21 and the electrocardiogram signal acquisition unit 25.
The pulse wave signal acquisition unit 27 drives the pulse wave sensor 9 to acquire a pulse wave signal.

The body fat calculation unit 29 calculates body fat by a known calculation method based on the impedance and the input body weight.
The electrocardiogram signal analysis unit 31 analyzes the electrocardiogram signal and calculates a known QT signal shown in FIG. The QT time is the time from the start time of a pulse accompanying the movement of the ventricle to the first peak after the pulse, as shown in FIG.

The electrocardiogram and pulse wave signal analysis unit 33 obtains a pulse wave propagation time (PTT), which is a delay time of the pulse wave signal with respect to the electrocardiogram signal, using the electrocardiogram signal and the pulse wave signal.
The pulse wave signal analysis unit 35 analyzes the pulse wave signal and, as shown in FIG. 4, the velocity pulse wave (the first peak wave height a1 of the first-order differential signal of the pulse wave signal) or the acceleration pulse wave ( The wave height d of the fourth peak of the second-order differential signal of the pulse wave signal) and AI are obtained. Here, AI is the ratio (P2 / P1) of the magnitude of the reflected wave and the traveling wave in the pulse wave.

The blood pressure calculation unit 37 calculates the blood pressure based on a predetermined calculation formula using QT time, PTT, velocity pulse wave a1, etc., acceleration pulse wave d, etc., AI, etc.
c) Next, an arithmetic expression used for calculating blood pressure will be described.

Here, for example, the blood pressure (estimated blood pressure: EBP) can be obtained using any one of the following equations (3) to (6). For reference, calculation formulas (1) and (2) not using conventional impedance are also described.

EBP = α · PTT / UT + β (1)
EBP = α · PTT + β · a1 + γ (2)

EBP = α · PTT + β · a1 + γ · Z + δ (3)
EBP = α · PTT / UT + β · d + γ · Z + δ (4)
EBP = α · PTT / UT + β · AI + γ · Z + δ (5)
EBP = α · PTT / UT + β · QT time + γ · Z + δ (6)

In the above equations, α, β, γ, and δ are coefficients. UT is the time from the rise of the pulse wave to the first peak (time to P0 in FIG. 4), and Z is the impedance. In addition, body fat FR can be used instead of Z. Hereinafter, each formula will be described.

In the formula (3), the impedance (Z) is used in addition to the pulse wave propagation time (PTT) and the velocity pulse wave (a1) to calculate the estimated blood pressure.
Among these, as will be described later, impedance is correlated with body fat, and body fat is correlated with body weight, so by using impedance to calculate estimated blood pressure, the estimated blood pressure considering weight is obtained. Can do. Therefore, the estimated blood pressure can be calculated automatically and accurately without inputting the weight manually separately as in the prior art.

  In the equation (4), the estimated blood pressure is calculated using impedance in addition to PTT / UT (blood pressure estimation equation based on the tube rule described in JP-A-2006-263354) and acceleration pulse wave.

  Accordingly, the estimated blood pressure considering the body weight can be obtained in the same manner as in the above formula (3), so that the estimated blood pressure can be automatically and accurately calculated without manually inputting the body weight.

In the formula (5), impedance is used in addition to PTT / UT and AI for calculation of the estimated blood pressure.
Accordingly, the estimated blood pressure considering the body weight can be obtained in the same manner as in the above formula (3), so that the estimated blood pressure can be automatically and accurately calculated without manually inputting the body weight. Here, since AI is used, since information on the central system and the peripheral system can be taken in, there is an advantage that blood pressure estimation accuracy is improved.

In the formula (6), impedance is used in addition to PTT / UT and QT time for calculating the estimated blood pressure.
Accordingly, the estimated blood pressure considering the body weight can be obtained in the same manner as in the above formula (3), so that the estimated blood pressure can be automatically and accurately calculated without manually inputting the body weight. Here, since the QT time is used, there is an advantage that blood pressure estimation accuracy is improved by capturing and considering the activity state of the heart.

d) Next, a control process performed by the blood pressure detection device will be described.
As shown in the flowchart of FIG. 5, in step (S) 100, it is determined whether to use body feature information. For example, it may be displayed on the display 15 whether or not the body feature information is used, and the driver's input may be prompted. If an affirmative determination is made here, the process proceeds to step 110, while if a negative determination is made, the process proceeds to step 120.

In step 110, since the input of body feature information is selected, when a weight or the like is input by a driver or the like, for example, using a touch panel, the data is acquired.
In step 120, impedance is measured.

In step 130, the electrocardiogram and the pulse wave are simultaneously measured. When only the pulse wave is used, only the pulse wave is measured.
In the subsequent step 140, the electrocardiogram signal and the pulse wave signal obtained by the measurement are analyzed, and the feature amount is calculated. For example, when the blood pressure is calculated using the equation (3), the pulse wave propagation time (PTT), the velocity pulse wave (a1), and the impedance (Z) are necessary. The pulse wave propagation time (PTT) is calculated using the pulse wave signal, and the velocity pulse wave (a1) is calculated by differentiating the pulse wave signal once.

  In subsequent step 150, validity of the electrocardiogram signal and the pulse wave signal is confirmed. That is, it is determined whether or not an electrocardiogram signal or a pulse wave signal is an appropriate value as a measurement value. If it is determined that the value is appropriate, the process proceeds to step 160. If it is determined that the value is not appropriate, the process returns to step 130 in order to measure the electrocardiogram and the pulse wave again.

In step 160, the impedance is measured again.
In the subsequent step 170, the difference between the measured value of the first impedance and the measured value of the second impedance is confirmed. That is, if the difference between the two measurement values is too large, a cause such as a measurement error may be considered, so it is determined whether or not the difference between the two measurement values is within a predetermined normal range. If an affirmative determination is made here, the process proceeds to step 180, whereas if a negative determination is made, the process returns to step 160 to measure impedance again.

  In step 180, the blood pressure is calculated using the pulse wave propagation time (PTT), velocity pulse wave (a1), and impedance (Z) obtained by the processing of each step described above using, for example, the above equation (3). calculate.

In the following step 190, body fat is calculated using impedance, weight, etc. (for example, further taking gender and height into consideration) as is well known.
In the subsequent step 200, the calculated blood pressure and body fat are displayed on the display 15 or notified through the speaker 17, and the process is temporarily terminated.

d) Next, an experimental example in which the effect of the present embodiment has been confirmed will be described.
FIG. 6A shows data obtained by actually measuring blood pressure using a cuff as in the past (horizontal axis), and estimated blood pressure data (vertical axis) calculated using the blood pressure measurement device 1 of the present embodiment. The correlation is taken. Here, the formula (3) using the pulse wave propagation time (PTT), the velocity pulse wave (a1), and the impedance (Z) is adopted as a formula for calculating the estimated blood pressure.

As is clear from the figure, the correlation coefficient (r) of both data is as high as 0.72, and it can be seen that the blood pressure measurement device 1 of this embodiment can measure blood pressure with high accuracy.
FIG. 6B shows the vertical axis and the horizontal axis in the same manner as FIG. 6A. Here, the formula (7) below is adopted as a formula for calculating the estimated blood pressure, and is input manually. The weight W (Weight) is also taken into account. In this equation (7), α, β, γ, δ, and ε are coefficients.

EBP = α · PTT + β · a1 + γ · Z + δ · W + ε (7)

As is clear from the figure, since the weight is further taken into account here, the correlation coefficient (r) of both data is 0.74, which is even higher, and the blood pressure measurement device 1 of the present embodiment makes the blood pressure more accurate. It can be seen that can be measured.

FIG. 6C shows the vertical axis and the horizontal axis as in FIG. Here, the following formula (8) is adopted as a formula for calculating the estimated blood pressure.
EBP = α · PTT / UT + β · a1 + γ · d1 + δ · Z + ε · d
+ Ζ · Weight + θ · Height + ι (8)

Note that UT, a1, d, d1, and AI (see FIG. 4 for d and d1) are used as pulse waves, and body weight (Weight) and height (Height) are used as body feature amounts. In this equation (8), α, β, γ, δ, ε, ζ, θ, and ι are coefficients.

  As is clear from the figure, here, since the pulse wave, impedance, and body feature amount are used, the correlation coefficient (r) of both data is as very high as 0.84, which is determined by the blood pressure measurement device 1 of the present embodiment. It can be seen that blood pressure can be measured with extremely high accuracy.

  FIG. 6D shows a comparative example. Since the conventional equation (1) (without using impedance) is adopted as a calculation formula, the correlation coefficient (r) of both data is 0. It can be seen that the blood pressure cannot be measured accurately with a small 61.

  FIG. 7 shows the correlation between body weight and impedance, and it can be seen that there is a correlation between body weight and impedance. In addition, the horizontal axis of FIG. 7 is the weight by the self-report of the person, and the vertical axis | shaft has shown the impedance.

  e) As described above, in the present embodiment, for example, the biological information of the pulse wave propagation time (PTT) and the velocity pulse wave (a1) obtained from the electrocardiogram signal and the pulse wave signal by using the equation (3), for example. Since the blood pressure is calculated not only using the impedance but also using the impedance (Z), the blood pressure can be measured with high accuracy by a simple method.

In addition, this invention is not limited to the said embodiment at all, and it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from this invention.
(1) For example, besides the above-described equations (3) to (8), pulse wave propagation time (PTT), pulse wave propagation velocity (PWV), electrocardiogram QT time, pulse wave AI, velocity pulse wave, and Blood pressure can be calculated (estimated) using at least one type of biological information in the acceleration pulse wave. For example, as in each expression, an expression is created by sequentially adding values obtained by multiplying biological information by a predetermined coefficient, and blood pressure can be calculated using the expression. Note that it is preferable to use a lot of biological information having different information related to blood pressure because the estimation accuracy is improved.

(2) Moreover, the function of the blood pressure measurement device described above can be realized by processing executed by a computer program, and this program can be recorded on a recording medium.
That is, the function for realizing the above-described program in the computer system can be provided as a program that is activated on the computer system side, for example. In the case of such a program, for example, the program is recorded on a computer-readable recording medium such as a flexible disk, a magneto-optical disk, a CD-ROM, a DVD, and a hard disk, and is used by being loaded into a computer system and started as necessary. be able to. In addition, the program may be recorded as a computer-readable recording medium such as a ROM or a backup RAM, and the ROM or the backup RAM may be incorporated into a computer system.

It is explanatory drawing which shows schematic structure of the blood-pressure measuring apparatus arrange | positioned in the vehicle interior of embodiment. It is a block diagram which shows the function of a blood pressure measuring device. It is a graph which shows an electrocardiogram signal. It is a graph which shows a pulse wave signal and its calculated value. It is a flowchart which shows the control processing of a blood-pressure measuring device. It is a graph which shows the correlation with the actual value using a cuff, and the calculated value by a blood-pressure measurement apparatus. It is a graph which shows the relationship between a body weight and an impedance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Blood pressure measuring device 3 ... Notification apparatus 7 ... Steering 5 ... Manual input part 9 ... Pulse wave sensor 11, 13 ... Electrode

Claims (14)

  A blood pressure measurement device that calculates blood pressure using biological information obtained from at least one of an electrocardiogram signal and a pulse wave signal detected from a living body and impedance detected from the living body.   The biological information is at least one of pulse wave propagation time (PTT), pulse wave propagation velocity (PWV), electrocardiogram QT time, pulse wave AI, velocity pulse wave, and acceleration pulse wave. The blood pressure measurement device according to claim 1.   The blood pressure measurement device according to claim 1 or 2, wherein the impedance is detected before, after, or both of the detection of the biological information.   The blood pressure measurement apparatus according to any one of claims 1 to 3, wherein the impedance is detected using a plurality of frequencies.   5. The blood pressure measurement apparatus according to claim 1, wherein at the time of calculating the blood pressure, at least one kind of body characteristic information is used among height, weight, age, and sex.   6. The blood pressure measurement device according to claim 5, wherein switching between using and not using the body characteristic information is possible.   The blood pressure measurement device according to claim 5 or 6, further comprising an interface for inputting at least one of the four types of body characteristic information.   The blood pressure measurement device according to claim 1, wherein the electrocardiogram signal and impedance are measured using the same electrode.   9. The blood pressure measurement device according to claim 8, wherein two modes of voltage measurement for obtaining the electrocardiogram signal and impedance measurement for obtaining the impedance are automatically switched.   10. The blood pressure measurement device according to claim 1, wherein body impedance is calculated and reported using the impedance.   The blood pressure measurement device according to any one of claims 1 to 10, wherein the blood pressure measurement device is mounted on a vehicle.   The blood pressure measurement device according to claim 11, wherein the electrode used for detecting the biological information is attached to a steering of a vehicle.   A program comprising means for realizing the function of the blood pressure measurement device according to claim 1 or 2.   A computer-readable recording medium on which the program according to claim 13 is recorded.

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