JP2014097242A - Pulse wave analyzer and method, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an extreme value of an acceleration pulse wave more appropriately.SOLUTION: A pulse wave analyzer (100) includes: first detection means (110) for detecting at least two or more of inflection points (t(0) to t(4)) of an acceleration pulse wave corresponding to a second-order differential value of a pulse wave of a living body; second detection means (120) for detecting a time (t(B) to t(E)) in which an absolute value of a first-order differential value of the acceleration pulse wave becomes minimum for each interval between the at least two or more of the inflection points; and third detection means (130) for detecting a value of the acceleration pulse wave corresponding to the time detected by the second detection means as a feature value of the acceleration pulse wave used for monitoring the body condition of the living body.

Description

  The present invention relates to a pulse wave analyzing apparatus and method for analyzing, for example, a pulse wave of a living body, and a technical field of a computer program.

  As this type of pulse wave analysis device, there is a technique for monitoring the state of a living body by analyzing a second-order differential value (hereinafter referred to as “acceleration pulse wave” as appropriate) of the pulse wave of the living body (for example, Patent Documents). 1). Specifically, Patent Document 1 describes a waveform corresponding to five consecutive extreme values of an acceleration pulse wave (specifically, a positive wave corresponding to the time when the aortic valve opens and blood begins to be pushed out from the left ventricle. A wave, a b wave which is a negative wave following the a wave, a c wave which is a positive wave or a negative wave following the b wave, and an e wave which appears after passing through a notch generated when the aortic valve is closed. ) To monitor the state of a living body (for example, to monitor the autonomic function).

Japanese Patent Laid-Open No. 2004-316

  Such an acceleration pulse wave waveform (that is, a wave to e wave) is generally detected by detecting five consecutive extreme values appearing in the acceleration pulse wave. However, depending on the waveform of the acceleration pulse wave, it is not always possible to suitably detect all five extreme values of the acceleration pulse wave. Specifically, the time when the first-order differential value of the acceleration pulse wave becomes zero is generally the time when the extreme value of the acceleration pulse wave appears. In other words, the acceleration pulse wave value at the time when the first-order differential value of the acceleration pulse wave becomes zero is generally detected as the extreme value of the acceleration pulse wave. However, depending on the waveform of the acceleration pulse wave, the first-order differential value of the acceleration pulse wave may not become zero at the time when the extreme value of the acceleration pulse wave should be detected. Such a phenomenon is particularly prominent in the c wave and d wave of the acceleration pulse wave. If an acceleration pulse wave in which such an extreme value is not suitably detected (that is, an acceleration pulse wave in which at least one of the a wave to the e wave is not suitably detected) is used, the state of the living body cannot be suitably monitored. There is a fear.

  The present invention has been made in view of the above problems, for example, and it is an object to provide a pulse wave analysis apparatus and method, and a computer program capable of more suitably detecting an extreme value of an acceleration pulse wave. To do.

  A pulse wave analysis device for solving the above-mentioned problem is a pulse wave analysis device for analyzing a pulse wave of a living body, and at least an inflection point of an acceleration pulse wave corresponding to a second-order differential value of the pulse wave of the living body. The absolute value of the first-order differential value of the acceleration pulse wave is minimized for each section between the first detection means for detecting two or more and at least two or more inflection points detected by the first detection means. Second detection means for detecting time, and a value of the acceleration pulse wave corresponding to the time detected by the second detection means is detected as a feature value of the acceleration pulse wave used for monitoring the state of the living body And third detecting means.

  A pulse wave analysis method for solving the above problem is a pulse wave analysis method for analyzing a pulse wave of a living body, and at least an inflection point of an acceleration pulse wave corresponding to a second-order differential value of the pulse wave of the living body is provided. The absolute value of the first-order differential value of the acceleration pulse wave is minimized for each section between the first detection step for detecting two or more and the at least two or more inflection points detected by the first detection means. A second detection step for detecting time and a value of the acceleration pulse wave corresponding to the time detected by the second detection means are detected as a characteristic value of the acceleration pulse wave used for monitoring the state of the living body. And a third detection step.

  A computer program for solving the above-described problems causes a computer to function as the above-described pulse wave analyzer.

It is a block diagram which shows the structure of the blood vessel age diagnostic apparatus. It is a flowchart which shows the flow of operation | movement of the blood vessel age diagnostic apparatus. It is a graph which shows an example of each waveform of the first-order differential value of a volume pulse wave, an acceleration pulse wave, the acceleration pulse wave, and the second-order differential value of an acceleration pulse wave. It is a graph which shows an example of each waveform of the first-order differential value of a volume pulse wave, an acceleration pulse wave, the acceleration pulse wave, and the second-order differential value of an acceleration pulse wave.

(Embodiment of pulse wave analyzer)
The pulse wave analysis device according to the present embodiment is a pulse wave analysis device that analyzes a pulse wave of a living body, and has at least two inflection points of acceleration pulse waves corresponding to a second-order differential value of the pulse wave of the living body. A time at which the absolute value of the first-order differential value of the acceleration pulse wave is minimized is detected for each section between the first detection means to be detected and at least two or more inflection points detected by the first detection means. And a second detecting means for detecting a value of the acceleration pulse wave corresponding to the time detected by the second detecting means as a feature value of the acceleration pulse wave used for monitoring the state of the living body. Detecting means.

  The pulse wave analysis device of this embodiment can analyze a pulse wave of a living body. The analysis result by the pulse wave analyzer is used, for example, to monitor the state of the living body. Specifically, the analysis result by the pulse wave analysis device may be used, for example, to estimate the blood vessel age of the living body. Or the analysis result by a pulse wave analyzer may be used, for example, in order to evaluate the autonomic nerve function of a living body. Or, for example, it may be used for estimating blood pressure in a living body or diagnosing heart disease, various organ diseases, and the like.

  In order to analyze the pulse wave, the pulse wave analysis apparatus includes a first detection unit, a second detection unit, and a third detection unit.

  The first detecting means detects an inflection point of the acceleration pulse wave corresponding to the second-order differential value of the pulse wave (so-called volume pulse wave). In particular, the first detection means detects at least two (ie, a plurality) inflection points of the acceleration pulse wave.

  The “acceleration pulse wave inflection point” is a point where the curve direction of the curve changes when the acceleration pulse wave is expressed by a curve (that is, a point where the curve tangent intersects the curve itself) Means. Such an inflection point typically coincides with a point at which the second derivative of the acceleration pulse wave becomes zero (that is, a point at which the sign of the second derivative of the acceleration pulse wave changes). In other words, such an inflection point typically coincides with a point where the first-order differential value of the acceleration pulse wave becomes an extreme value.

  The second detection means is a time at which the absolute value of the first-order differential value of the acceleration pulse wave is minimum for each acceleration pulse wave section (in other words, period) divided by the inflection point detected by the first detection means. Is detected. For example, the first detecting means includes a first inflection point, a second inflection point following the first inflection point,..., And N-1 (where N is an integer of 2 or more). Assume that the Nth inflection point following the inflection point is detected. At this time, the second detection means detects the first time at which the absolute value of the first-order differential value of the acceleration pulse wave is minimum in the section between the first inflection point and the second inflection point. To do. Similarly, the second detection means detects the second time when the absolute value of the first-order differential value of the acceleration pulse wave is minimum in the section between the second inflection point and the third inflection point. To do. Similarly, after that, the second detection means detects an acceleration pulse in a section between the k-1 inflection point (where k is an integer satisfying 1 ≦ k ≦ N) and the kth inflection point. The (k-1) -th time at which the absolute value of the first-order differential value of the wave is minimum is detected.

  The third detection means uses the acceleration pulse wave value corresponding to the time detected by the second detection means as a feature value of the acceleration pulse wave (e.g., from the above-described a wave to e). It is detected as a feature value corresponding to a wave).

  Here, as described above, the characteristic value of the acceleration pulse wave used for monitoring the state of the living body is, for example, a positive wave corresponding to the time when the aortic valve opens and blood begins to be pushed out from the left ventricle. a characteristic value corresponding to the a wave, a characteristic value corresponding to the b wave that is a negative wave following the a wave, a characteristic value corresponding to the d wave from the c wave that is a positive wave or a negative wave following the b wave, the aorta An example is a characteristic value corresponding to an e-wave that appears after a notch generated when the valve is closed. As described above, such a characteristic value typically matches the extreme value of the acceleration pulse wave. The “extreme value of acceleration pulse wave” means a local maximum value or minimum value of the acceleration pulse wave. Such an extreme value generally means the value of the acceleration pulse wave at the time when the first-order differential value of the acceleration pulse wave becomes zero. However, as will be described in detail later using a graph, depending on the waveform of the acceleration pulse wave (in other words, the waveform of the acceleration pulse wave (volume pulse wave)), At the time when the extreme value is to be detected, the first-order differential value of the acceleration pulse wave may not become zero. As a cause of this, an individual difference between living organisms can be cited as an example. As a result, when a method of directly detecting the extreme value of the acceleration pulse wave is employed, a situation may occur in which only a part of the characteristic value of the acceleration pulse wave that should be detected is detected. However, in order to suitably monitor the state of the living body, only the value of the acceleration pulse wave at the time when the first-order differential value of the acceleration pulse wave becomes zero (that is, the extreme value of the acceleration pulse wave in the original sense) can be used. First, the value of the acceleration pulse wave at the time when the first-order differential value of the acceleration pulse wave should be zero but not zero (that is, it is not the extreme value of the acceleration pulse wave in the original sense, It is preferable to treat “values that should be treated as extreme values” as “feature values of acceleration pulse waves”.

  Therefore, the pulse wave analysis device of the present embodiment detects the feature value of the acceleration pulse wave by using the relationship between the extreme value and the inflection point described below. Specifically, the extreme value typically exists between the inflection points. In other words, an inflection point exists between the extreme values. Therefore, if the relationship between such an inflection point and an extreme value is taken into consideration, there is no extreme value of acceleration pulse wave in a general sense in a section between two consecutive inflection points. Even if the first-order differential value of the acceleration pulse wave does not become zero, it can be handled as a feature point of the acceleration pulse wave. Therefore, the pulse wave analysis device of the present embodiment takes into account the relationship between such an inflection point and an extreme value, and the feature point of the acceleration pulse wave for each section between the two inflection points. Is detected.

  Here, the time at which the extreme value of the acceleration pulse wave appears coincides with the time at which the first-order differential value of the acceleration pulse wave in the section between the two inflection points becomes zero. Therefore, in this embodiment, the time at which the absolute value of the first-order differential value of the acceleration pulse wave in the section between the two inflection points is minimum is defined as the time at which the feature value of the acceleration pulse wave appears. . That is, the pulse wave analysis device according to the present embodiment calculates the acceleration pulse wave value at the time when the absolute value of the first-order differential value of the acceleration pulse wave in the section between the two inflection points is minimum. It is detected as a feature value. As a result, the pulse wave analysis device of the present embodiment can preferably detect the characteristic value of the acceleration pulse wave (for example, a value corresponding to the above-described a wave to e wave). In particular, the pulse wave analysis device of the present embodiment detects the time when the first-order differential value of the acceleration pulse wave becomes zero (that is, directly detects the extreme value of the acceleration pulse wave). Even when the feature value cannot be detected suitably, the feature value of the acceleration pulse wave can be detected suitably.

<2>
In the pulse wave analysis apparatus according to the present embodiment, the first detection unit detects at least two or more inflection points that appear continuously starting from the maximum extreme value of the acceleration pulse wave for each predetermined period. .

  According to this aspect, the maximum extremum corresponding to the a wave that is a positive wave corresponding to the time when the aortic valve opens and blood begins to be pushed out from the left ventricle (that is, one of the characteristic values) is used as a starting point. A feature value corresponding to the e wave (further, a feature value corresponding to the f wave appearing after the e wave, a feature value corresponding to the wave after the f wave, etc.) is suitably detected from the b wave appearing after the wave. .

<3>
In another aspect of the pulse wave analysis apparatus of the present embodiment, the second detection means has a minimum absolute value of the first-order differential value of the acceleration pulse wave for each section between two adjacent inflection points. The time that becomes is detected.

  According to this aspect, the characteristic value of the acceleration pulse wave used for monitoring the physical condition of the living body (for example, the above-described a wave to e wave and substantially extreme value) is suitably detected.

  Here, “adjacent to each other” means a state of adjacent to each other in time series. Therefore, the first detecting means has a first inflection point, a second inflection point following the first inflection point,..., And N-1 (where N is an integer of 2 or more). When the Nth inflection point following the inflection point is detected, the k-1 inflection point (where k is an integer satisfying 1 ≦ k ≦ N), the kth inflection point, Are two inflection points adjacent to each other.

<4>
In another aspect of the pulse wave analysis device of the present embodiment, the first detection means detects a point where the second-order differential value of the acceleration pulse wave becomes zero as an inflection point.

  According to this aspect, the first detection means can suitably detect the inflection point.

(Embodiment of pulse wave analysis method)
<5>
The pulse wave analysis method of this embodiment is a pulse wave analysis method for analyzing a pulse wave of a living body, and includes at least two or more inflection points of an acceleration pulse wave corresponding to a second-order differential value of the pulse wave of the living body. A time at which the absolute value of the first-order differential value of the acceleration pulse wave is minimized is detected for each section between the first detection step to be detected and at least two or more inflection points detected by the first detection means. And a second detecting step for detecting a value of the acceleration pulse wave corresponding to the time detected by the second detection means as a characteristic value of the acceleration pulse wave used for monitoring the physical condition of the living body. A detection step.

  According to the pulse wave analysis method of the present embodiment, various effects enjoyed by the above-described pulse wave analysis device of the present embodiment can be suitably enjoyed.

  Incidentally, in response to various aspects adopted by the pulse wave analysis device of the present embodiment, the pulse wave analysis method of the present embodiment may adopt various aspects.

(Embodiment of computer program)
The computer program according to the present embodiment causes the computer to function as the pulse wave analysis device according to the present embodiment described above (including various aspects thereof).

  According to the computer program of this embodiment, the various effects which the pulse wave analyzer of this embodiment mentioned above enjoys can be enjoyed suitably.

  Incidentally, in response to various aspects adopted by the pulse wave analysis device of the present embodiment, the computer program of the present embodiment may adopt various aspects.

  Such an operation and other advantages of the present embodiment will be clarified from examples described below.

  As described above, the pulse wave analysis apparatus according to the present embodiment includes the first detection unit, the second detection unit, and the third detection unit. The pulse wave analysis method of the present embodiment includes a first detection step, a second detection step, and a third detection step. The computer program of this embodiment causes a computer to function as the pulse wave analysis device of this embodiment. Therefore, the extreme value of the acceleration pulse wave can be detected more suitably.

  Hereinafter, embodiments of a pulse wave analyzing apparatus and method and a computer program will be described with reference to the drawings. In the following description, an example in which the pulse wave analysis apparatus is applied to the blood vessel age diagnosis apparatus 100 will be described.

(1) Configuration of Vascular Age Diagnosis Device First, the configuration of the vascular age diagnosis device 100 will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the blood vessel age diagnostic apparatus 100.

  As shown in FIG. 1, the blood vessel age diagnostic apparatus 100 includes an inflection point detector 110 that is a specific example of “first detection means” and a feature value detector that is a specific example of “second detection means”. 120 and a blood vessel age diagnostic device 130 which is a specific example of “third detection means”.

  The inflection point detector 110 detects the inflection point of the acceleration pulse wave corresponding to the second-order differential value of the volume pulse wave of the living body. In order to detect the inflection point of the acceleration pulse wave, the inflection point detector 110 includes a differentiator 111 and a zero cross time detector 112.

  The differentiator 111 calculates a second-order differential value of the acceleration pulse wave and outputs the calculated second-order differential value of the acceleration pulse wave to the zero cross time detector 112. The differentiator 111 further calculates a first-order differential value of the acceleration pulse wave and outputs the calculated first-order differential value of the acceleration pulse wave to the feature value detector 120.

  The zero cross time detector 112 detects the time when the second-order differential value of the acceleration pulse wave becomes zero. Note that the time when the second-order differential value of the acceleration pulse wave becomes zero (time t (0) to time t (4) described later) corresponds to the time when the inflection point of the acceleration pulse wave appears. That is, the value of the acceleration pulse wave at the time when the second-order differential value of the acceleration pulse wave becomes zero (time t (0) to time t (4) described later) corresponds to the inflection point of the acceleration pulse wave. The zero cross time detector 112 outputs the detected time to the feature value detector 120.

  The feature value detector 120 detects feature values of acceleration pulse waves (specifically, feature values used for diagnosing blood vessel age). In order to detect the feature value of the acceleration pulse wave, the feature value detector 120 includes a waveform divider 121 and a minimum absolute value time detector 122.

  The waveform divider 121 divides the first-order differential value of the acceleration pulse wave into a plurality of sections (in other words, periods or waveforms) divided by the time detected by the zero cross time detector 112.

  The minimum absolute value time detector 122 is the time at which the absolute value of the first-order differential value of the acceleration pulse wave is minimum for each of the plurality of sections obtained by the division operation of the waveform divider 121 (time t (described later)). The time t (E)) is detected from B). The time when the absolute value of the first-order differential value of the acceleration pulse wave is minimum corresponds to the time when the feature value of the acceleration pulse wave appears. That is, the value of the acceleration pulse wave at the time when the absolute value of the first-order differential value of the acceleration pulse wave is minimum corresponds to the feature value of the acceleration pulse wave. The minimum absolute value time detector 122 outputs the detected time to the blood vessel age diagnostic device 130.

  As the characteristic value of the acceleration pulse wave, for example, a value corresponding to a wave which is a positive wave corresponding to the time when the aortic valve opens and blood begins to be pushed out from the left ventricle (hereinafter referred to as “point A” as appropriate). ) Is an example. In addition, as a characteristic value of the acceleration pulse wave, a value corresponding to a b wave that is a negative wave following the a wave (hereinafter, referred to as “point B” as appropriate) is given as an example. Further, the characteristic value of the acceleration pulse wave is a value corresponding to the c wave, which is a positive wave or a negative wave following the b wave (hereinafter referred to as “C point” and “D point”, respectively). As an example. Further, as an example of the characteristic value of the acceleration pulse wave, a value corresponding to an e wave that appears after a notch generated when the aortic valve is closed (hereinafter, referred to as “point E” as appropriate) is given as an example.

  However, feature points other than the points A to E illustrated here may be used. However, in this embodiment, from the viewpoint of simplifying the description, the description will be made using an example in which the points A to E (that is, five feature values) are used as the feature values of the acceleration pulse wave.

The blood vessel age diagnostic device 130 diagnoses the blood vessel age of the living body. In order to diagnose the vascular age of the living body, the vascular age diagnostic device 130 includes an amplitude value detector 131 and a vascular age estimator 132;
The amplitude value detector 131 detects the amplitude value of the acceleration pulse wave at the time detected by the minimum absolute value time detector 122. The amplitude value of the acceleration pulse wave at the time detected by the minimum absolute time detector 122 corresponds to the feature value of the acceleration pulse wave.

  The blood vessel age estimating unit 132 estimates the blood vessel age of the living body based on the amplitude value of the acceleration pulse wave detected by the amplitude value detector 131 (that is, the characteristic value of the acceleration pulse wave). As a blood vessel age estimation method, a known method may be used.

  The blood vessel age estimation unit 132 may estimate the blood vessel age using all the characteristic values of the acceleration pulse wave detected by the amplitude value detector 131 (that is, all of the points A to E). Alternatively, the blood vessel age estimation unit 132 estimates the blood vessel age using a part of the characteristic values of the acceleration pulse wave detected by the amplitude value detector 131 (for example, the points A, C, and E). Also good. When the blood vessel age estimation unit 132 estimates the blood vessel age using a part of the characteristic values of the acceleration pulse wave (for example, the points A, C, and E), the amplitude value detector 131 has the minimum absolute value. It is sufficient to detect the amplitude value of the acceleration pulse wave at a part of the time detected by the value time detector 122.

  FIG. 1 shows an example in which an acceleration pulse wave is input to the blood vessel age diagnostic apparatus 100. However, the volume pulse wave may be input to the blood vessel age diagnostic apparatus 100. In this case, it is preferable that the differentiator 111 (or another differentiator different from the differentiator 111) included in the blood vessel age diagnostic apparatus 100 calculates the acceleration pulse wave by differentiating the volume pulse wave.

(2) Flow of Operation of Vascular Age Diagnosis Device Next, the flow of operation of the vascular age diagnosis device 100 will be described with reference to FIGS. FIG. 2 is a flowchart showing the operation flow of the blood vessel age diagnostic apparatus 100. FIG. 3 is a graph showing an example of waveforms of the first-order differential value of the volume pulse wave, the acceleration pulse wave, the acceleration pulse wave, and the second-order differential value of the acceleration pulse wave. FIG. 4 is a graph showing other examples of waveforms of the volume pulse wave, acceleration pulse wave, first-order differential value of acceleration pulse wave, and second-order differential value of acceleration pulse wave.

  As shown in FIG. 2, the amplitude value detector 131 uses the maximum value of the acceleration pulse wave (in other words, the maximum extreme value and the maximum amplitude value) as the first characteristic value (point A) of the acceleration pulse wave. (Step S10). For example, in the acceleration pulse wave shown in the second graph of FIG. 3 and FIG. 4, the maximum value of the acceleration pulse wave is observed at time t (A). Therefore, the amplitude value detector 131 detects the value of the acceleration pulse wave at time t (A) as the first characteristic value (point A) of the acceleration pulse wave.

  The acceleration pulse wave shown in the second stage graphs of FIGS. 3 and 4 is a signal obtained by second-order differentiation of the volume pulse wave shown in the first stage graphs of FIGS. 3 and 4. It is a waveform. The volume pulse wave shown in the first-stage graphs of FIGS. 3 and 4 corresponds to a volume pulse wave for one cycle. In step S10, the amplitude detector 131 preferably detects the maximum value of the acceleration pulse wave obtained by second-order differentiation of the volume pulse wave for one cycle. This is because the amplitude of the a wave that is a positive wave corresponding to the time when the aortic valve opens and blood begins to be pushed out from the left ventricle is larger than the amplitude of each of the b wave to the e wave. This is because it can be detected as the first characteristic value (point A) of the wave. For this reason, the operation shown in FIG. 2 is preferably performed repeatedly in accordance with the period of the volume pulse wave.

  After that, the inflection point detector 110 is time t (0), time t (1), time t (2) at which the inflection point of the acceleration pulse wave appears after the time corresponding to the point A detected in step S10. ), Time t (3) and time t (4) are detected (step S11). Specifically, the differentiator 111 first outputs the second-order differential value of the acceleration pulse wave to the zero cross time detector 112. The zero cross time detector 112 detects the time t (4) from the time t (0) when the second-order differential value of the acceleration pulse wave becomes zero.

  For example, a graph indicating the second-order differential value of the acceleration pulse wave shown in the second graph of each of FIGS. 3 and 4 is described in the fourth graph of each of FIGS. 3 and 4. As shown in FIGS. 3 and 4, the time when the second-order differential value of the acceleration pulse wave becomes zero (that is, the time when it crosses the zero level) is detected. As described above, the value of the acceleration pulse wave from the time t (0) to the time t (4) when the second-order differential value of the acceleration pulse wave becomes zero is the second stage in FIG. 3 and FIG. This corresponds to the inflection point of the acceleration pulse wave indicated by the white square symbol in the graph.

  At this time, it is preferable that the inflection point detector 110 detects five times (that is, time t (0) to time t (4)) adjacent to each other (in other words, appearing continuously in time). . This is because the blood vessel age diagnostic apparatus 100 according to the present embodiment uses the characteristic that one feature value exists between two inflection points adjacent to each other, and the acceleration pulse wave excluding the point A is used. This is because four feature values (specifically, points B to E) are detected. Therefore, in order to detect four characteristic values (specifically, points B to E) of the acceleration pulse wave, at least five times when the second-order differential value of the acceleration pulse wave becomes zero are detected. It is preferable.

  Thereafter, the feature value detector 120 minimizes the absolute value of the first-order differential value of the acceleration pulse wave in a section from time t (0) to time t (1) (in other words, a period). Time t (B) is detected (step S12). Specifically, the waveform divider 121 is a signal component corresponding to a section from time t (0) to time t (1) in the first-order differential value of the acceleration pulse wave output from the differentiator 111. To extract. Thereafter, the minimum absolute value time detector 122 receives the time t (when the absolute value of the signal component corresponding to the section from the time t (0) extracted by the waveform divider 121 to the time t (1) is minimum. B) is detected.

  For example, a graph showing the first-order differential value of the acceleration pulse wave shown in the second graph in each of FIGS. 3 and 4 is described in the third graph in each of FIGS. 3 and 4. As shown in FIGS. 3 and 4, in the section from time t (0) to time t (1), the first-order differential value of the acceleration pulse wave becomes zero at time t (B) ( That is, the absolute value of the first derivative of the acceleration pulse wave is minimized). Accordingly, in step S12, this time t (B) is detected.

  Thereafter, the amplitude detector 131 detects the acceleration pulse wave value (that is, the amplitude value) at time t (B) as the second characteristic value (point B) of the acceleration pulse wave (step S13).

  Following the operation from step S12 to step S13, the feature value detector 120 is connected to the interval from time t (1) to time t (2) (in other words, period ), The time t (C) at which the absolute value of the first-order differential value of the acceleration pulse wave is minimum is detected (step S14). The detection mode at time t (C) is the same as the detection mode at time t (B).

  For example, in the example shown in FIG. 3, the absolute value of the first-order differential value of the acceleration pulse wave is minimized at time t (C) in the section from time t (1) to time t (2). (However, the first-order differential value of the acceleration pulse wave is not zero). Therefore, in step S14, this time t (C) is detected.

  On the other hand, in the example shown in FIG. 4, in the section from time t (1) to time t (2), the first-order differential value of the acceleration pulse wave becomes zero at time t (C) ( That is, the absolute value of the acceleration pulse wave is minimized). Therefore, in step S14, this time t (C) is detected.

  After that, the amplitude detector 131 detects the acceleration pulse wave value (that is, the amplitude value) at time t (C) as the third characteristic value (point C) of the acceleration pulse wave (step S15).

  Following the operation from step S12 to step S15, the feature value detector 120 follows the interval from time t (2) to time t (3) (in other words, period ), The time t (D) at which the absolute value of the first-order differential value of the acceleration pulse wave is minimum is detected (step S16). The detection mode at time t (D) is the same as the detection mode at time t (B).

  For example, in the example shown in FIG. 3, the absolute value of the first-order differential value of the acceleration pulse wave is minimized at time t (D) in the section from time t (2) to time t (3). (However, the first-order differential value of the acceleration pulse wave is not zero). Accordingly, in step S16, this time t (D) is detected.

  On the other hand, in the example shown in FIG. 4, the first-order differential value of the acceleration pulse wave becomes zero at time t (D) in the section from time t (2) to time t (3) ( That is, the absolute value of the acceleration pulse wave is minimized). Accordingly, in step S16, this time t (D) is detected.

  Thereafter, the amplitude detector 131 detects the acceleration pulse wave value (that is, the amplitude value) at time t (D) as the fourth characteristic value (point D) of the acceleration pulse wave (step S17).

  Following the operation from step S12 to step S17, the feature value detector 120 is connected to the interval from time t (3) to time t (4) (in other words, period ), The time t (E) at which the absolute value of the first-order differential value of the acceleration pulse wave is minimum is detected (step S18). The detection mode at time t (E) is the same as the detection mode at time t (B).

  For example, as shown in FIGS. 3 and 4, in the section from time t (3) to time t (4), the first-order differential value of the acceleration pulse wave becomes zero at time t (E). (That is, the absolute value of the first derivative of the acceleration pulse wave is minimized). Accordingly, in step S18, this time t (E) is detected.

  Thereafter, the amplitude detector 131 detects the acceleration pulse wave value (that is, the amplitude value) at time t (E) as the fifth characteristic value (point E) of the acceleration pulse wave (step S19).

  Thereafter, the blood vessel age estimation unit 132 includes the first feature value (point A), the second feature value (point B), the third feature value (point C), and the fourth feature value (point D) detected by the amplitude detector 131. ) And the fifth characteristic value (point E) are used to estimate the blood vessel age of the living body (step S20).

  Here, as described above, the five characteristic values (points A to E) of the acceleration pulse wave typically coincide with the extreme values of the acceleration pulse wave. The “extreme value of acceleration pulse wave” generally means the value of the acceleration pulse wave at the time when the first-order differential value of the acceleration pulse wave becomes zero. In this sense, in the example shown in FIG. 4, the extreme value of the acceleration pulse wave matches the feature value of the acceleration pulse wave. However, in the example shown in FIG. 3, the first-order differential value of the acceleration pulse wave at the time when the extreme value of the acceleration pulse wave should be originally detected (for example, time t (C) and t (D) in FIG. 3). Does not become zero. As a cause of this, an individual difference between living organisms can be cited as an example. As a result, when the technique of directly detecting the extreme value of the acceleration pulse wave is employed, a situation may occur in which only some of the feature values of the five characteristic values of the acceleration pulse wave that should be detected are detected. However, in order to appropriately estimate the blood vessel age, not only the value of the acceleration pulse wave at the time when the first-order differential value of the acceleration pulse wave becomes zero (that is, the extreme value of the acceleration pulse wave in the original sense). The value of the acceleration pulse wave at the time when the first-order differential value of the acceleration pulse wave should be zero in spite of the fact that it does not become zero (that is, it is not the extreme value of the acceleration pulse wave in the original sense, It is preferable to treat “values that are desired to be handled as values” as “feature values of acceleration pulse waves”.

  For this reason, in this embodiment, instead of detecting the time when the first-order differential value of the acceleration pulse wave becomes zero (that is, detecting the extreme value of the acceleration pulse wave directly), By detecting the time at which the absolute value of the first-order differential value of the acceleration pulse wave is minimum for each section between the inflection points, the feature point of the acceleration pulse wave that exists between two adjacent inflection points Is detected.

  This is because extrema typically exist between inflection points. In other words, an inflection point exists between the extreme values. Therefore, if such a relationship between the inflection point and the extreme value is taken into consideration, an extremum of the acceleration pulse wave in a general sense exists in the section between two consecutive inflection points. Even if it is not (that is, the first-order differential value of the acceleration pulse wave does not become zero), it can be treated as a feature point of the acceleration pulse wave. In the present embodiment, by using such a relationship between the inflection point and the extreme value, the feature point of the acceleration pulse wave is detected for each section between the two inflection points.

  In addition, at the time when the extreme value of the acceleration pulse wave appears, the first-order differential value of the acceleration pulse wave in the section between the two inflection points is zero (that is, the absolute value of the first-order differential value is minimum). Coincides with the time. Therefore, in this embodiment, the time at which the absolute value of the first-order differential value of the acceleration pulse wave in the section between the two inflection points is minimum is defined as the time at which the feature value of the acceleration pulse wave appears. . As a result, in the present embodiment, five characteristic values of the acceleration pulse wave are suitably detected.

  According to the operation of this embodiment, as shown in FIG. 3, the time when the extreme value of the acceleration pulse wave should be originally detected (for example, time t (C) and t (D) in FIG. 3). 5, even if the first-order differential value of the acceleration pulse wave does not become zero, the five characteristic values of the acceleration pulse wave (particularly, points C and D where the first-order differential value of the acceleration pulse wave does not become zero). It is detected suitably. That is, according to the operation of the present embodiment, even if some of the feature points of the acceleration pulse wave are not the extreme value of the acceleration pulse wave, the five feature values of the acceleration pulse wave (particularly, the acceleration pulse wave) A point C or point D where the first-order differential value of the wave does not become zero is suitably detected. In other words, in the present embodiment, the feature value of the acceleration pulse wave is suitable for the method of detecting the time when the first-order differential value of the acceleration pulse wave becomes zero (that is, directly detecting the extreme value of the acceleration pulse wave). Even if it cannot be detected in a short time, the feature value of the acceleration pulse wave is preferably detected.

  In the example shown in FIG. 4, all five characteristic values of the acceleration pulse wave coincide with the extreme values of the acceleration pulse wave. In this case, the feature point of the acceleration pulse wave that exists between two adjacent inflection points may be detected by detecting the time when the first-order differential value of the acceleration pulse wave becomes zero.

  Further, the present invention can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and a pulse wave analysis apparatus and method, and a computer program that involve such a change are also included. It is also included in the technical idea of the present invention.

DESCRIPTION OF SYMBOLS 100 Blood vessel age diagnostic apparatus 110 Inflection point detector 111 Differentiator 112 Zero crossing time detector 120 Feature value detector 121 Waveform divider 122 Minimum absolute value time detector 130 Blood vessel age diagnostic device 131 Amplitude value detector 132 Blood vessel age estimator

Claims (6)

A device for analyzing a pulse wave of a living body,
First detection means for detecting at least two inflection points of acceleration pulse wave corresponding to a second-order differential value of the pulse wave of the living body;
Second detection means for detecting a time at which the absolute value of the first-order differential value of the acceleration pulse wave is minimum for each section between at least two or more inflection points detected by the first detection means;
And third detecting means for detecting a value of the acceleration pulse wave corresponding to the time detected by the second detecting means as a characteristic value of the acceleration pulse wave used for monitoring the state of the living body. Characteristic pulse wave analyzer.   The said 1st detection means detects at least 2 or more inflection points which appear continuously from the maximum extreme value of the said acceleration pulse wave as a starting point for every predetermined period. Pulse wave analyzer.   The second detection means detects a time at which an absolute value of a first-order differential value of the acceleration pulse wave is minimum for each section between two inflection points adjacent to each other. Or the pulse wave analysis device according to 2;   4. The pulse wave analysis apparatus according to claim 1, wherein the first detection unit detects a point at which a second-order differential value of the acceleration pulse wave becomes zero as an inflection point. 5. . A pulse wave analysis method for analyzing a pulse wave of a living body,
A first detection step of detecting at least two inflection points of an acceleration pulse wave corresponding to a second-order differential value of the pulse wave of the living body;
A second detection step of detecting a time at which an absolute value of the first-order differential value of the acceleration pulse wave is minimized for each section between at least two inflection points detected by the first detection means;
A third detection step of detecting a value of the acceleration pulse wave corresponding to the time detected by the second detection means as a feature value of the acceleration pulse wave used for monitoring the physical condition of the living body. A characteristic pulse wave analysis method.   A computer program for causing a computer to function as the pulse wave analysis device according to any one of claims 1 to 4.

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