WO2024095965A1 - Pulse wave analysis device, pulse wave analysis method, and program - Google Patents

Abstract

This pulse wave analysis device (10) comprises an acquisition unit (11) for acquiring a pulse wave waveform, a generation unit (12) for generating an acceleration pulse wave waveform, a detection unit (13) for detecting a feature point included in the acceleration pulse wave waveform, and an output unit (14) for outputting the feature point. The detection unit (13): determines, for one of the maxima present in the acceleration pulse wave waveform, whether an ascending inflection point exists between said maxima and the next minima present after the maxima, and if said ascending inflection point exists, detects the ascending inflection point as a feature point; or determines, for one of the minima present in the acceleration pulse wave waveform, whether a descending inflection point exists between said minima and the next maxima present after the minima, and if said descending inflection point exists, detects the descending inflection point as a feature point.

Description

Pulse wave analysis device, pulse wave analysis method and program

This disclosure relates to a pulse wave analysis device, a pulse wave analysis method, and a program for analyzing pulse waves.

Patent Document 1 discloses a technology for understanding the state of the circulatory system (for example, monitoring autonomic nerve activity) by analyzing fluctuations in the peak value and time interval of characteristic points (for example, a-wave to e-wave) determined by peaks in an accelerated pulse waveform, which is a second derivative waveform of the pulse waveform.

JP 2004-000316 A

However, due to aging and individual differences, the maximum or minimum values that serve as characteristic points (e.g., from a-wave to e-wave) in the accelerated pulse wave waveform may disappear. This disappearance phenomenon is often particularly noticeable in the c-wave and d-wave. The technology in Patent Document 1 does not take this disappearance phenomenon into account, so there is a problem in that it is not possible to detect the disappeared characteristic points, making it difficult to properly analyze the pulse wave.

The present disclosure provides a pulse wave analysis device that can properly analyze a pulse wave even when extreme values that are characteristic points in an accelerated pulse wave waveform have disappeared.

The pulse wave analysis device according to the present disclosure is a pulse wave analysis device that analyzes pulse waves, and includes an acquisition unit that acquires a pulse wave waveform, a generation unit that generates an acceleration pulse wave waveform that is a second derivative waveform of the pulse wave waveform, a detection unit that detects feature points contained in the acceleration pulse wave waveform, and an output unit that outputs the detected feature points, and the detection unit determines whether or not an upward inflection point exists between any maximum value present in the acceleration pulse wave waveform and the minimum value next to the maximum value, and if no upward inflection point exists between the maximum value and the minimum value, If so, the minimum value is detected as a feature point, and if an upward inflection point exists between the maximum value and the minimum value, the upward inflection point is detected as a feature point. Alternatively, for any minimum value present in the accelerated pulse wave waveform, it is determined whether or not a downward inflection point exists between the minimum value and the maximum value next to the minimum value, and if no downward inflection point exists between the minimum value and the maximum value, the maximum value is detected as a feature point, and if a downward inflection point exists between the minimum value and the maximum value, the downward inflection point is detected as a feature point.

The pulse wave analysis method according to the present disclosure is a pulse wave analysis method executed by a pulse wave analysis device that analyzes pulse waves, and includes an acquisition step of acquiring a pulse wave waveform, a generation step of generating an acceleration pulse wave waveform which is a second derivative waveform of the pulse wave waveform, a detection step of detecting characteristic points contained in the acceleration pulse wave waveform, and an output step of outputting the detected characteristic points, and in the detection step, for any maximum value present in the acceleration pulse wave waveform, it is determined whether or not there is an upward inflection point between the maximum value and the minimum value present next to the maximum value, and If the upward inflection point does not exist in the acceleration pulse waveform, the minimum value is detected as a characteristic point, and if the upward inflection point exists between the maximum value and the minimum value, the upward inflection point is detected as a characteristic point. Alternatively, for any minimum value present in the acceleration pulse waveform, it is determined whether or not a downward inflection point exists between the minimum value and the maximum value next to the minimum value, and if the downward inflection point does not exist between the minimum value and the maximum value, the maximum value is detected as a characteristic point, and if the downward inflection point exists between the minimum value and the maximum value, the downward inflection point is detected as a characteristic point.

The program disclosed herein is a program for causing a computer to execute the above-mentioned pulse wave analysis method.

The pulse wave analysis device according to one aspect of the present disclosure can properly analyze the pulse wave even when the extreme values that are characteristic points in the acceleration pulse waveform disappear.

FIG. 13 is a diagram for explaining the disappearance of extreme values in an acceleration pulse waveform. 1 is a block diagram showing an example of a pulse wave analysis device according to an embodiment; 4 is a flowchart showing an example of the operation of the pulse wave analysis device according to the embodiment. FIG. 13 is a diagram showing an example of an acceleration pulse wave waveform in which no extreme values are lost. FIG. 13 is a diagram showing an example of an accelerated pulse wave waveform in which the b-wave and c-wave have disappeared. FIG. 13 is a diagram showing an example of an accelerated pulse wave waveform in which the c-wave and d-wave have disappeared. FIG. 13 is a diagram showing feature points that are not correctly detected when noise occurs. FIG. 13 is a diagram showing feature points that are correctly detected when noise occurs. 13 is a flowchart showing an example of a pulse wave analysis method according to another embodiment.

(How one aspect of the present disclosure was achieved)
First, the process by which one embodiment of the present disclosure was achieved will be described with reference to FIG.

FIG. 1 is a diagram for explaining the disappearance of extreme values in an acceleration pulse wave waveform. FIG. 1(a) shows an acceleration pulse wave waveform in which the extreme values have not disappeared, FIG. 1(b) shows an acceleration pulse wave waveform in which the difference between adjacent maximum and minimum values (e.g., c-wave and d-wave) has become small, and FIG. 1(c) shows an acceleration pulse wave waveform in which adjacent maximum and minimum values (e.g., c-wave and d-wave) have disappeared.

As shown in FIG. 1(a), a typical acceleration pulse wave has multiple extreme values (specifically, multiple maximum values and multiple minimum values). The first maximum value in the acceleration pulse wave is called the a-wave, the minimum value following the a-wave is called the b-wave, the maximum value following the b-wave is called the c-wave, the minimum value following the c-wave is called the d-wave, and the maximum value following the d-wave is called the e-wave. The minimum value following the e-wave is called the f-wave. Note that the minimum value following a maximum value such as the a-wave, c-wave, or e-wave in an acceleration pulse wave waveform refers to the first minimum value among one or more minimum values that exist in time behind the maximum value (in other words, the minimum value that exists in the earliest position in time among one or more minimum values that exist in time behind the maximum value). For example, in the acceleration pulse wave waveform shown in FIG. 1(a), the minimum value following the a-wave is the b-wave. In addition, the maximum value that exists next to a minimum value such as a b wave or a d wave in an acceleration pulse waveform refers to the first maximum value among one or more maximum values that exist in time after the relevant minimum value (in other words, the maximum value that exists in the earliest position in time among one or more maximum values that exist in time after the relevant minimum value). For example, in the acceleration pulse waveform shown in FIG. 1(a), the maximum value that exists next to the b wave is the c wave.

Due to aging and individual differences, the maximum or minimum values that are characteristic points in the accelerated pulse wave waveform may vary, and the difference between adjacent maximum and minimum values (e.g., c-wave and d-wave) may become smaller as shown in FIG. 1B, or adjacent maximum and minimum values (e.g., c-wave and d-wave) may disappear as shown in FIG. 1C. In the accelerated pulse wave waveform shown in FIG. 1B, the difference between the c-wave and d-wave is smaller, but the c-wave and d-wave have not disappeared, so the c-wave and d-wave can be detected as characteristic points. In the accelerated pulse wave waveform shown in FIG. 1C, the c-wave and d-wave have disappeared, so the c-wave and d-wave cannot be detected as characteristic points. For this reason, in the case shown in FIG. 1C, it is difficult to properly analyze the pulse wave.

The following describes a pulse wave analysis device that can properly analyze a pulse wave even when the extreme values that are characteristic points in the acceleration pulse wave waveform have disappeared.

The following describes the embodiment in detail with reference to the drawings.

The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, the arrangement and connection of the components, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

(Embodiment)
A pulse wave analysis device according to an embodiment will be described below.

FIG. 2 is a block diagram showing an example of a pulse wave analysis device 10 according to an embodiment.

The pulse wave analysis device 10 is a device that analyzes pulse waves (e.g., a human's pulse waves). Pulse waves contain a variety of important information for understanding the state of a living body's circulatory system. Because the pattern of the accelerated pulse wave waveform changes with age, the pulse wave analysis device 10 can estimate the subject's vascular age, for example, by analyzing the wave height or area of characteristic points (e.g., a-wave to f-wave) in the accelerated pulse wave waveform.

The pulse wave analysis device 10 comprises an acquisition unit 11, a generation unit 12, a detection unit 13, and an output unit 14. The pulse wave analysis device 10 is a computer including a processor and a memory. The memory is a ROM (Read Only Memory) and a RAM (Random Access Memory), etc., and can store programs executed by the processor. The acquisition unit 11, the generation unit 12, the detection unit 13, and the output unit 14 are realized by a processor that executes programs stored in the memory, etc.

The acquisition unit 11 acquires the subject's pulse waveform. The acquisition unit 11 acquires the pulse waveform from, for example, a pulse wave measuring device. The pulse wave measuring device has a light emitting unit and a light receiving unit, and acquires a pulse wave signal (pulse wave waveform) based on the light reflected by the light receiving unit when light is irradiated from the light emitting unit and reflected by the subject's body. For example, the pulse wave measuring device acquires a voltage value converted from the amount of reflected light received as the pulse wave signal. Note that transmitted light that has passed through the human body may be used instead of reflected light that has reflected from the human body.

The generating unit 12 generates an acceleration pulse waveform, which is a second derivative waveform of the pulse waveform. Also, for example, the generating unit 12 may generate a velocity pulse waveform, which is a first derivative waveform of the pulse waveform. For example, the generating unit 12 generates a velocity pulse waveform by first differentiating the pulse waveform, and generates an acceleration pulse waveform by first differentiating the velocity pulse waveform.

The detection unit 13 detects characteristic points included in the acceleration pulse waveform. Specifically, the detection unit 13 determines whether or not an upward inflection point exists between any maximum value present in the acceleration pulse waveform and the minimum value next to the maximum value, and if the upward inflection point does not exist between the maximum value and the minimum value, detects the minimum value as a characteristic point, and if the upward inflection point exists between the maximum value and the minimum value, detects the upward inflection point as a characteristic point. Alternatively, the detection unit 13 determines whether or not a downward inflection point exists between any minimum value present in the acceleration pulse waveform and the maximum value next to the minimum value, and if the downward inflection point does not exist between the minimum value and the maximum value, detects the maximum value as a characteristic point, and if the downward inflection point exists between the minimum value and the maximum value, detects the downward inflection point as a characteristic point. An upward inflection point is a point on a continuous plane curve where the curve changes from convex downward to convex upward. A downward inflection point is a point on a continuous plane curve where the curve changes from convex upward to convex downward. The operation of the detection unit 13 will be described in detail later.

The output unit 14 outputs the detected feature points. For example, the output unit 14 outputs the detected feature points to a component for analyzing pulse waves that is provided in the pulse wave analysis device 10. Note that the output unit 14 may output the detected feature points to a device external to the pulse wave analysis device 10.

Next, the operation of the pulse wave analysis device 10 (specifically, the operation of the detection unit 13) will be described in detail with reference to Figures 3 to 8.

FIG. 3 is a flowchart showing an example of the operation of the pulse wave analysis device 10 according to the embodiment.

Figure 4 shows an example of an acceleration pulse waveform in which there is no loss of extreme values. Figure 4 shows the pulse waveform, a velocity pulse waveform which is the first derivative waveform of the pulse waveform, and an acceleration pulse waveform which is the second derivative waveform of the pulse waveform, in a case in which there is no loss of extreme values in the acceleration pulse waveform.

Figure 5 shows an example of an acceleration pulse waveform in which the b-waves and c-waves have disappeared. Figure 5 shows the pulse waveform, a velocity pulse waveform which is the first derivative of the pulse waveform, and an acceleration pulse waveform which is the second derivative of the pulse waveform when the b-waves and c-waves have disappeared in the acceleration pulse waveform.

Figure 6 shows an example of an acceleration pulse waveform in which the c-wave and d-wave have disappeared. Figure 6 shows the pulse waveform, a velocity pulse waveform which is the first derivative of the pulse waveform, and an acceleration pulse waveform which is the second derivative of the pulse waveform when the c-wave and d-wave have disappeared in the acceleration pulse waveform.

Fig. 7 shows feature points that are not correctly detected when noise occurs. Fig. 7 shows the pulse waveform, the velocity pulse waveform, which is the first derivative of the pulse waveform, and the acceleration pulse waveform, which is the second derivative of the pulse waveform, when noise is superimposed on the d-wave and subsequent waves in the acceleration pulse waveform.

Fig. 8 shows characteristic points that are correctly detected when noise occurs. Fig. 8 shows the pulse waveform, the velocity pulse waveform, which is the first derivative of the pulse waveform, and the acceleration pulse waveform, which is the second derivative of the pulse waveform, when noise is superimposed on the d-wave and subsequent waves in the acceleration pulse waveform.

In addition, in Figures 4 to 8, upward inflection points are indicated by upward triangles (△) and downward inflection points are indicated by downward triangles (▽).

First, the detection unit 13 sets the first maximum value in the acceleration pulse waveform to the a-wave and detects this maximum value as a feature point (step S101). The first maximum value in the acceleration pulse waveform is the maximum value that exists at the earliest position in time among the maximum values present in the acceleration pulse waveform. Since the wave height of the a-wave is generally large, this embodiment is based on the premise that the a-wave does not disappear.

Next, the detection unit 13 determines whether or not there is an upward inflection point between the a-wave and the minimum value following the a-wave in the accelerated pulse waveform (step S102). In the accelerated pulse waveforms shown in Figures 4 and 6 to 8, the minimum value following the a-wave is the point indicated as the b-wave, and it can be seen that there is no upward inflection point between the a-wave and this point. In the accelerated pulse waveform shown in Figure 5, the minimum value following the a-wave is the point indicated as the d-wave, and it can be seen that there is an upward inflection point between the a-wave and this point.

If there is no upward inflection point between the a-wave and the next minimum value after the a-wave (No in step S102), the detection unit 13 sets the minimum value to the b-wave and detects the minimum value as a feature point (step S103). For example, as shown in Figures 4 and 6 to 8, the minimum value corresponding to the b-wave has not disappeared in the accelerated pulse waveform, so this minimum value can be detected as the feature point set to the b-wave.

If an upward inflection point exists between the a-wave and the minimum value next to the a-wave (Yes in step S102), the detection unit 13 sets the upward inflection point to the b-wave and c-wave, and detects the upward inflection point as a characteristic point (step S104). For example, as shown in FIG. 5, the minimum and maximum values corresponding to the b-wave and c-wave disappear from the acceleration pulse waveform, becoming an upward inflection point. Therefore, if an upward inflection point exists between the a-wave and the minimum value next to the a-wave, the upward inflection point can be detected as a characteristic point that is regarded as the disappeared b-wave and c-wave. In this way, the b-wave and c-wave can be detected even in an acceleration pulse waveform in which the b-wave and c-wave have disappeared.

If the detection unit 13 sets the b-wave to the minimum value next to the a-wave in step S103, it determines whether or not there is a downward inflection point between the b-wave and the maximum value next to the b-wave in the accelerated pulse waveform (step S105). In the accelerated pulse waveforms shown in Figures 4, 6 to 8, the b-wave is set to the minimum value next to the a-wave. In the accelerated pulse waveforms shown in Figures 4, 7 and 8, the b-wave is the maximum value next to the b-wave, which is indicated as the c-wave, and it can be seen that there is no downward inflection point between the b-wave and this point. In the accelerated pulse waveform shown in Figure 6, the b-wave is the maximum value next to the e-wave, and it can be seen that there is a downward inflection point between the b-wave and this point.

If there is no downward inflection point between the b wave and the maximum value next to the b wave (No in step S105), the detection unit 13 sets the maximum value to the c wave and detects the maximum value as a feature point (step S106). For example, as shown in Figures 4, 7, and 8, the maximum value corresponding to the c wave has not disappeared in the accelerated pulse waveform, so this maximum value can be detected as the feature point set to the c wave.

If a downward inflection point exists between the b wave and the maximum value next to the b wave (Yes in step S105), the detection unit 13 sets the downward inflection point to the c wave and d wave, and detects the downward inflection point as a feature point (step S107). For example, as shown in FIG. 6, the maximum and minimum values corresponding to the c wave and d wave have disappeared in the accelerated pulse wave waveform, resulting in a downward inflection point. Therefore, if a downward inflection point exists between the b wave and the maximum value next to the b wave, the downward inflection point can be detected as a feature point that is regarded as the disappeared c wave and d wave. In this way, the c wave and d wave can be detected even in an accelerated pulse wave waveform in which the c wave and d wave have disappeared.

If the upward inflection point following the a-wave is set to the b-wave and c-wave in step S104, or if the maximum value following the b-wave is set to the c-wave in step S106, the detection unit 13 determines whether or not an upward inflection point exists between the c-wave and the minimum value following the c-wave in the accelerated pulse waveform (step S108). In the accelerated pulse waveforms shown in Figures 4, 7, and 8, the maximum value following the b-wave is set to the c-wave. Also, in the accelerated pulse waveform shown in Figure 5, the upward inflection point following the a-wave is set to the b-wave and c-wave. In the accelerated pulse waveforms shown in Figures 4, 5, 7, and 8, the minimum value following the c-wave is the point indicated as the d-wave, and it can be seen that there is no upward inflection point between the c-wave and this point. Although not shown, in an accelerated pulse waveform in which an upward inflection point exists between the c wave and the minimum value following the c wave, an upward inflection point similar to the upward inflection point existing between the a wave and the minimum value following the a wave shown in FIG. 5 exists between the c wave and the minimum value following the c wave.

If there is no upward inflection point between the c-wave and the minimum value next to the c-wave (No in step S108), the detection unit 13 sets the minimum value to the d-wave and detects the minimum value as a feature point (step S109). For example, as shown in Figures 4, 5, 7, and 8, the minimum value corresponding to the d-wave has not disappeared in the accelerated pulse waveform, so this minimum value can be set to the d-wave and detected as a feature point.

If an upward inflection point exists between the c wave and the minimum value following the c wave (Yes in step S108), the detection unit 13 sets the upward inflection point to the d wave and e wave and detects the upward inflection point as a characteristic point (step S110). Although the accelerated pulse waveform in this case is not shown, in this case, the minimum and maximum values corresponding to the d wave and e wave disappear from the accelerated pulse waveform and become an upward inflection point. Therefore, if an upward inflection point exists between the c wave and the minimum value following the c wave, the upward inflection point can be detected as a characteristic point that is regarded as the disappeared d wave and e wave.

If the detection unit 13 sets the downward inflection point after the b wave to the c wave and d wave in step S107, or sets the minimum value after the c wave to the d wave in step S109, it determines whether or not a downward inflection point exists between the d wave and the maximum value after the d wave in the accelerated pulse waveform (step S111). In the accelerated pulse waveforms shown in Figures 4, 5, 7, and 8, the minimum value after the c wave is set to the d wave. Also, in the accelerated pulse waveform shown in Figure 6, the downward inflection point after the b wave is set to the c wave and d wave. In the accelerated pulse waveforms shown in Figures 4 to 7, the maximum value after the d wave is the point indicated as the e wave, and it can be seen that there is no downward inflection point between the d wave and this point. Although not shown, in an acceleration pulse wave waveform in which a downward inflection point exists between the d wave and the maximum value following the d wave, a downward inflection point exists between the d wave and the maximum value following the d wave, similar to the downward inflection point existing between the b wave and the maximum value following the b wave shown in Figure 6. Note that the acceleration pulse wave waveform shown in Figure 8 is the same waveform as the acceleration pulse wave waveform shown in Figure 7, but in Figure 8, the maximum value at the same location as the maximum value shown as the e wave in Figure 7 is not shown as an e wave. This will be described later.

If there is no descending inflection point between the d wave and the maximum value next to the d wave (No in step S111), the detection unit 13 sets the maximum value to the e wave and detects the maximum value as a feature point (step S112). For example, as shown in Figures 4 to 7, the maximum value corresponding to the e wave has not disappeared in the accelerated pulse waveform, so this maximum value can be set to the e wave and detected as a feature point.

If a downward inflection point exists between the d wave and the maximum value next to the d wave (Yes in step S111), the detection unit 13 sets the downward inflection point to the e wave and the f wave and detects the downward inflection point as a feature point (step S113). Although the accelerated pulse waveform in this case is not shown, in this case, the maximum and minimum values corresponding to the e wave and the f wave disappear in the accelerated pulse waveform, becoming a downward inflection point. Therefore, if a downward inflection point exists between the d wave and the maximum value next to the d wave, the downward inflection point can be detected as a feature point that is regarded as the disappeared e wave and f wave. Note that the f wave does not necessarily have to be set.

However, in Figure 7, noise is superimposed on the d-wave onwards in the accelerated pulse waveform, and the noise causes a maximum value to occur immediately after the d-wave. As a result, if noise is superimposed on the d-wave on the accelerated pulse waveform, this maximum value will be erroneously detected as an e-wave.

In step S111, the detection unit 13 may determine whether or not a descending inflection point exists between a point on the acceleration pulse waveform at the later of the time of the d wave on the acceleration pulse waveform and the time of the next minimum value (the "trough of the first derivative pulse wave" shown in FIG. 8) of the maximum value on the velocity pulse waveform (the "peak of the first derivative pulse wave" shown in FIG. 8) and the next maximum value. Since the e wave occurs after the time of the next minimum value after the maximum value on the velocity pulse waveform, by detecting the e wave on the acceleration pulse waveform at least after that time on the velocity pulse waveform, the e wave can be correctly detected as a feature point even if noise is superimposed after the d wave on the acceleration pulse waveform as shown in FIG. 8.

When the upward inflection point next to the c wave is set to the d wave and the e wave in step S110, or when the maximum value next to the d wave is set to the e wave in step S112, the detection unit 13 judges whether or not an upward inflection point exists between the e wave and the minimum value next to the e wave in the accelerated pulse waveform (step S114). In the accelerated pulse waveforms shown in Figures 4 to 8, the maximum value next to the d wave is set to the e wave. In the accelerated pulse waveforms shown in Figures 4 to 8, the minimum value next to the e wave is the point indicated as the f wave, and it can be seen that there is no upward inflection point between the e wave and this point. Note that, although not shown, in an accelerated pulse waveform in which an upward inflection point exists between the e wave and the minimum value next to the e wave, an upward inflection point exists between the e wave and the minimum value next to the a wave, such as the upward inflection point existing between the a wave and the minimum value next to the a wave shown in Figure 5, between the e wave and the minimum value next to the e wave. Note that the acceleration pulse waveform shown in FIG. 8 is the same waveform as the acceleration pulse waveform shown in FIG. 7, but in FIG. 8, the minimum value at the same location as the minimum value shown as an f wave in FIG. 7 is not shown as an f wave. This will be discussed later.

If there is no upward inflection point between the e-wave and the minimum value next to the e-wave (No in step S114), the detection unit 13 sets the minimum value to the f-wave and detects the minimum value as a feature point (step S115). For example, as shown in Figures 4 to 8, the minimum value corresponding to the f-wave has not disappeared in the accelerated pulse waveform, so this minimum value can be detected as the feature point set to the f-wave.

If an upward inflection point exists between the e-wave and the minimum value following the e-wave (Yes in step S114), the detection unit 13 sets the upward inflection point to the f-wave and detects the upward inflection point as a characteristic point (step S116). Although the accelerated pulse waveform in this case is not shown, in this case, the minimum value corresponding to the f-wave disappears in the accelerated pulse waveform and becomes an upward inflection point. Therefore, if an upward inflection point exists between the e-wave and the minimum value following the e-wave, the upward inflection point can be detected as a characteristic point that is regarded as the disappeared f-wave.

However, in Figure 7, noise is superimposed after the d wave on the accelerated pulse waveform, and the noise causes a maximum value to occur immediately after the d wave, and a minimum value to occur immediately after the maximum value. As a result, if noise is superimposed after the d wave on the accelerated pulse waveform, this minimum value will be erroneously detected as an f wave.

In step S114, the detection unit 13 may determine whether or not an upward inflection point exists between a point on the acceleration pulse waveform at the later of the time of the e wave on the acceleration pulse waveform and the time of the next minimum value after the maximum value on the velocity pulse waveform, and the next minimum value after that point. Since the f wave occurs after the time of the next minimum value after the maximum value on the velocity pulse waveform, by detecting the f wave on the acceleration pulse waveform at least after that time on the velocity pulse waveform, the f wave can be correctly detected as a characteristic point even if noise is superimposed after the d wave on the acceleration pulse waveform, as shown in FIG. 8.

3, the detection unit 13 determines whether or not an upward inflection point exists between each maximum value in the acceleration pulse waveform and the minimum value next to the maximum value, and determines whether or not a downward inflection point exists between each minimum value in the acceleration pulse waveform and the maximum value next to the minimum value, but this is not limiting. For example, the detection unit 13 may determine whether or not an upward inflection point exists between any maximum value in the acceleration pulse waveform and the minimum value next to the maximum value. Alternatively, the detection unit 13 may determine whether or not a downward inflection point exists between any minimum value in the acceleration pulse waveform and the maximum value next to the minimum value. In other words, the detection unit 13 may determine whether or not an upward inflection point exists only for any maximum value in the acceleration pulse waveform, or may determine whether or not a downward inflection point exists only for any minimum value in the acceleration pulse waveform.

As described above, the present disclosure detects the disappeared extreme value as a feature point by utilizing the fact that in an acceleration pulse wave waveform in which an extreme value has disappeared, the disappeared extreme value becomes an upward inflection point or a downward inflection point. Specifically, when a minimum value and a maximum value that should exist after a certain maximum value have disappeared, the disappeared minimum value and maximum value become one upward inflection point. Therefore, when an upward inflection point exists between a certain maximum value and the next minimum value in the acceleration pulse wave waveform, the upward inflection point can be regarded as the disappeared minimum value and maximum value and detected as a feature point. Similarly, when a maximum value and a minimum value that should exist after a certain minimum value have disappeared, the disappeared maximum value and minimum value become one downward inflection point. Therefore, when a downward inflection point exists between a certain minimum value and the next maximum value in the acceleration pulse wave waveform, the downward inflection point can be regarded as the disappeared maximum value and minimum value and detected as a feature point. Therefore, even if the extreme values that are characteristic points in the acceleration pulse waveform disappear, the pulse wave can be analyzed appropriately.

(Other embodiments)
Although the pulse wave analysis device 10 according to one or more aspects of the present disclosure has been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as it does not deviate from the spirit of the present disclosure, various modifications conceived by a person skilled in the art to each embodiment and forms constructed by combining components of different embodiments may also be included within the scope of one or more aspects of the present disclosure.

For example, in the above embodiment, an example was described in which the detection unit 13 detects feature points set in the f-wave, but the detection unit 13 does not have to detect feature points set in the f-wave.

For example, in the above embodiment, the generating unit 12 generates a velocity pulse waveform, which is a first derivative waveform of the pulse waveform, but the generating unit 12 does not have to generate a velocity pulse waveform. In this case, the detecting unit 13 does not have to determine whether or not a descending inflection point exists between a point on the acceleration pulse waveform at the later of the time of the d wave in the acceleration pulse waveform and the time of the minimum value next to the maximum value in the velocity pulse waveform, and the maximum value next to that point. Also, in this case, the detecting unit 13 does not have to determine whether or not an ascending inflection point exists between a point on the acceleration pulse waveform at the later of the time of the e wave in the acceleration pulse waveform and the time of the minimum value next to the maximum value in the velocity pulse waveform, and the minimum value next to that point.

For example, the present disclosure can be realized not only as a pulse wave analysis device 10, but also as a pulse wave analysis method including steps (processing) performed by the components that make up the pulse wave analysis device 10.

FIG. 9 is a flowchart showing an example of a pulse wave analysis method according to another embodiment.

The pulse wave analysis method is a method executed by a pulse wave analysis device that analyzes a pulse wave, and includes, as shown in FIG. 9, an acquisition step (step S11) for acquiring a pulse wave waveform, a generation step (step S12) for generating an acceleration pulse wave waveform, which is a second derivative waveform of the pulse wave waveform, a detection step (steps S13 to S18) for detecting characteristic points contained in the acceleration pulse wave waveform, and an output step (step S19) for outputting the detected characteristic points. In the detection step, for any maximum value present in the acceleration pulse wave waveform, it is determined whether or not an upward inflection point exists between the maximum value and the minimum value next to the maximum value (step S13), and if no upward inflection point exists between the maximum value and the minimum value (step S1 3), the minimum value is detected as a feature point (step S14); if an upward inflection point exists between the maximum value and the minimum value (step S13, Yes), the upward inflection point is detected as a feature point (step S15); or, for any minimum value present in the accelerated pulse waveform, it is determined whether or not a downward inflection point exists between the minimum value and the maximum value next to the minimum value (step S16); if no downward inflection point exists between the minimum value and the maximum value (step S16, No), the maximum value is detected as a feature point (step S17); if a downward inflection point exists between the minimum value and the maximum value (step S16, Yes), the downward inflection point is detected as a feature point (step S18).

Note that FIG. 9 shows an example in which steps S13 to S15 are performed before steps S16 to S18 are performed, but steps S16 to S18 may be performed before steps S13 to S15, or steps S13 to S15 and steps S16 to S18 may be performed in parallel. Also, it is not necessary for either steps S13 to S15 or steps S16 to S18 to be performed.

For example, the present disclosure can be realized as a program for causing a computer (processor) to execute the steps included in the pulse wave analysis method. Furthermore, the present disclosure can be realized as a non-transitory computer-readable recording medium, such as a CD-ROM, on which the program is recorded.

For example, when the present disclosure is realized as a program (software), each step is performed by running the program using hardware resources such as a computer's CPU, memory, and input/output circuits. In other words, each step is performed by the CPU obtaining data from memory or input/output circuits, etc., performing calculations, and outputting the results of the calculations to memory or input/output circuits, etc.

In the above embodiment, each component included in the pulse wave analysis device 10 may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

Some or all of the functions of the pulse wave analysis device 10 according to the above embodiment are typically realized as an LSI, which is an integrated circuit. These may be individually integrated into a single chip, or may be integrated into a single chip that includes some or all of the functions. Furthermore, the integrated circuit is not limited to an LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connections and settings of the circuit cells inside the LSI may also be used.

(Additional Note)
The above description of the embodiments discloses the following techniques.

(Technology 1) A pulse wave analysis device for analyzing pulse waves, comprising an acquisition unit for acquiring a pulse wave waveform, a generation unit for generating an acceleration pulse wave waveform, which is a second derivative waveform of the pulse wave waveform, a detection unit for detecting feature points contained in the acceleration pulse wave waveform, and an output unit for outputting the detected feature points, wherein the detection unit determines, for any maximum value present in the acceleration pulse wave waveform, whether or not an upward inflection point exists between the maximum value and the minimum value present next to the maximum value, and when no upward inflection point exists between the maximum value and the minimum value, outputs the minimum value. A pulse wave analysis device that detects the maximum value as a characteristic point, and if an upward inflection point exists between the maximum value and the maximum value, detects the upward inflection point as a characteristic point, or, for any minimum value present in the accelerated pulse wave waveform, determines whether or not a downward inflection point exists between the minimum value and the maximum value next to the minimum value, and detects the maximum value as a characteristic point if the downward inflection point does not exist between the minimum value and the maximum value, and detects the downward inflection point as a characteristic point if the downward inflection point exists between the minimum value and the maximum value.

For example, when the extreme values have not disappeared in the acceleration pulse wave waveform, a first maximum, a first minimum value next to the first maximum, a second maximum value next to the first minimum, and a second minimum value next to the second maximum are present in the acceleration pulse wave waveform. In contrast, in an acceleration pulse wave waveform in which the first minimum value and the second maximum value have disappeared, the minimum value that occurs next to the first maximum is the second minimum value, and the first minimum value and the second maximum value are not detected as feature points, and the pulse wave cannot be analyzed appropriately. Also, for example, when the extreme values have not disappeared in the acceleration pulse wave waveform, a first minimum value, a first maximum value next to the first minimum value, a second minimum value next to the first maximum value, and a second maximum value next to the second minimum are present in the acceleration pulse wave waveform. In contrast, in an accelerated pulse wave waveform in which the first maximum and second minimum have disappeared, the maximum value that occurs next to the first minimum becomes the second maximum, and the first maximum and second minimum are not detected as feature points, which may result in the pulse wave not being analyzed properly.

Therefore, the present disclosure detects the disappeared extreme value as a feature point by utilizing the fact that in an acceleration pulse wave waveform in which an extreme value has disappeared, the disappeared extreme value becomes an upward inflection point or a downward inflection point. Specifically, when a minimum value and a maximum value that should exist after a certain maximum value have disappeared, the disappeared minimum value and maximum value become one upward inflection point. Therefore, when an upward inflection point exists between a certain maximum value and the next minimum value in an acceleration pulse wave waveform, the upward inflection point can be regarded as the disappeared minimum value and maximum value and detected as a feature point. Similarly, when a maximum value and a minimum value that should exist after a certain minimum value have disappeared, the disappeared maximum value and minimum value become one downward inflection point. Therefore, when a downward inflection point exists between a certain minimum value and the next maximum value in an acceleration pulse wave waveform, the downward inflection point can be regarded as the disappeared maximum value and minimum value and detected as a feature point. Therefore, even if the extreme values that are characteristic points in the acceleration pulse waveform disappear, the pulse wave can be analyzed appropriately.

(Technology 2) The detection unit sets the first maximum value in the accelerated pulse waveform to the a-wave and detects the maximum value as a feature point, determines whether or not an upward inflection point exists between the a-wave and the next minimum value in the accelerated pulse waveform, and if the upward inflection point does not exist between the a-wave and the minimum value, sets the minimum value to the b-wave and detects the minimum value as a feature point, and if the upward inflection point exists between the a-wave and the minimum value, sets the upward inflection point to the b-wave and c-wave and detects the upward inflection point as a feature point. and when the minimum value next to the a-wave is set to the b-wave, it is determined whether or not a downward inflection point exists between the b-wave and the maximum value next to the b-wave in the accelerated pulse wave waveform, and when the downward inflection point does not exist between the b-wave and the maximum value, the maximum value is set to the c-wave and detected as a characteristic point, and when the downward inflection point exists between the b-wave and the maximum value, the downward inflection point is set to the c-wave and d-wave and detected as a characteristic point, and an upward inflection point next to the a-wave is set to the b-wave and c-wave. or when the maximum value next to the b wave is set to the c wave, it is determined whether or not an upward inflection point exists between the c wave and the minimum value next to the c wave in the accelerated pulse waveform, and if the upward inflection point does not exist between the c wave and the minimum value, the minimum value is set to the d wave and detected as a characteristic point, and if the upward inflection point exists between the c wave and the minimum value, the upward inflection point is set to the d wave and the e wave and detected as a characteristic point, and a downward inflection point next to the b wave is set to the c wave. When the pulse wave analysis device is set to the d wave and the d wave, or when the minimum value next to the c wave is set to the d wave, it is determined whether or not a downward inflection point exists between the d wave and the maximum value next to the d wave in the accelerated pulse wave waveform, and if the downward inflection point does not exist between the d wave and the maximum value, the maximum value is set to the e wave and detected as a characteristic point, and if the downward inflection point exists between the d wave and the maximum value, the downward inflection point is set to the e wave and detected as a characteristic point.

If an upward inflection point exists between the a wave and the next minimum of the a wave, this upward inflection point can be detected as a feature point that is considered to be the b wave and c wave that have disappeared. If an upward inflection point does not exist between the a wave and the next minimum of the a wave, the minimum value corresponding to the b wave has not disappeared, and this minimum value can be detected as a feature point that has been set for the b wave.

If the minimum value following the a wave is set as the b wave, and there is a downward inflection point between the b wave and its next maximum, then this downward inflection point can be detected as a characteristic point that is regarded as the c wave and d wave that have disappeared. If there is no downward inflection point between the b wave and its next maximum, then the maximum value corresponding to the c wave has not disappeared, and this maximum value can be detected as a characteristic point that has been set for the c wave.

If the upward inflection point following the a wave is set to the b and c waves, or if the maximum value following the b wave is set to the c wave, and an upward inflection point exists between the c wave and the next minimum value of the c wave, then that upward inflection point can be detected as a characteristic point that is considered to be the disappeared d wave and e wave. If there is no upward inflection point between the c wave and the next minimum value of the c wave, then the minimum value corresponding to the d wave has not disappeared, and so this minimum value can be detected as a characteristic point that has been set to the d wave.

If the downward inflection point following the b wave is set as the c wave and d wave, or if the minimum value following the c wave is set as the d wave, and a downward inflection point exists between the d wave and the next maximum value of the d wave, then that downward inflection point can be detected as a characteristic point that is considered to be the e wave that has disappeared. If there is no downward inflection point between the d wave and the next maximum value of the d wave, then the maximum value corresponding to the e wave has not disappeared, and so this maximum value can be detected as a characteristic point that has been set for the e wave.

In this way, even if the extreme values disappear, the a-waves through e-waves can be detected, allowing the pulse wave to be analyzed appropriately.

(Technology 3) The pulse wave analysis device according to Technology 2 further includes a generator that generates a velocity pulse waveform, which is a first derivative of the pulse waveform, and a detector that determines whether or not a downward inflection point exists between a point on the acceleration pulse waveform that is the later of the time of a d-wave on the acceleration pulse waveform and the time of the next minimum value after the maximum value on the velocity pulse waveform, and the next maximum value after that point. If no downward inflection point exists between that point and the maximum value, the maximum value is set to an e-wave and detected as a characteristic point, and if a downward inflection point exists between that point and the maximum value, the descending inflection point is set to an e-wave and detected as a characteristic point.

If noise is superimposed after the d wave on the acceleration pulse waveform, the e wave may be erroneously detected as a feature point in the section where the noise is superimposed. Therefore, the e wave is detected in the acceleration pulse waveform at least after the point of the next minimum value after the maximum value on the velocity pulse waveform. This is because the e wave occurs after the point of the next minimum value after the maximum value on the velocity pulse waveform. As a result, even if noise is superimposed after the d wave on the acceleration pulse waveform, the e wave can be correctly detected as a feature point. At this time, if the e wave has disappeared, the downward inflection point can be detected as a feature point that is considered to be the e wave.

(Technology 4) The pulse wave analysis device according to Technology 2, in which the detection unit determines whether or not an upward inflection point exists between the e wave and the minimum value following the e wave in the accelerated pulse wave waveform when the upward inflection point following the c wave is set to the d wave and e wave, or when the maximum value following the d wave is set to the e wave, and if the upward inflection point does not exist between the e wave and the minimum value, the minimum value is set to the f wave and detected as a characteristic point, and if the upward inflection point exists between the e wave and the minimum value, the upward inflection point is set to the f wave and detected as a characteristic point.

If an upward inflection point exists between the e wave and the next minimum of the e wave, this upward inflection point can be detected as a feature point that is considered to be the disappeared f wave. If an upward inflection point does not exist between the e wave and the next minimum of the e wave, the minimum value corresponding to the f wave has not disappeared, and this minimum value can be detected as a feature point set for the f wave.

(Technology 5) The pulse wave analysis device according to Technology 4, further comprising: the generating unit generating a velocity pulse waveform which is a first derivative waveform of the pulse waveform; the detecting unit determining whether or not an upward inflection point exists between a point on the acceleration pulse waveform which is the later of the time of an e-wave on the acceleration pulse waveform and the time of the next minimum value after the maximum value on the velocity pulse waveform, and the next minimum value after said point; if no upward inflection point exists between said point and said minimum value, said minimum value is set to an f-wave and detected as a characteristic point; and if an upward inflection point exists between said point and said minimum value, said upward inflection point is set to an f-wave and detected as a characteristic point.

If noise is superimposed after the d wave on the acceleration pulse waveform, the f wave may be erroneously detected as a feature point in the section where the noise is superimposed. Therefore, the f wave is detected in the acceleration pulse waveform at least after the point of the next minimum value after the maximum value on the velocity pulse waveform. This is because the f wave occurs after the point of the next minimum value after the maximum value on the velocity pulse waveform. As a result, even if noise is superimposed after the d wave on the acceleration pulse waveform, the f wave can be correctly detected as a feature point. At this time, if the f wave has disappeared, the upward inflection point can be detected as a feature point that is considered to be an f wave.

(Technology 6) A pulse wave analysis method executed by a pulse wave analysis device that analyzes pulse waves, comprising: an acquisition step of acquiring a pulse wave waveform; a generation step of generating an accelerated pulse wave waveform, which is a second derivative waveform of the pulse wave waveform; a detection step of detecting characteristic points contained in the accelerated pulse wave waveform; and an output step of outputting the detected characteristic points, in which, for any maximum value present in the accelerated pulse wave waveform, a determination is made as to whether or not an upward inflection point exists between the maximum value and the minimum value present next to the maximum value, and a determination is made as to whether or not the upward inflection point exists between the maximum value and the minimum value. a pulse wave analysis method that detects the minimum value as a characteristic point if there is no minimum value, detects the rising inflection point as a characteristic point if there is an upward inflection point between the maximum value and the minimum value, or determines whether or not there is a downward inflection point between any minimum value present in the accelerated pulse wave waveform and the maximum value next to the minimum value, detects the maximum value as a characteristic point if there is no downward inflection point between the minimum value and the maximum value, and detects the downward inflection point as a characteristic point if there is a downward inflection point between the minimum value and the maximum value.

This provides a pulse wave analysis method that can properly analyze a pulse wave even when the extreme values that are characteristic points in the acceleration pulse waveform have disappeared.

(Technology 7) A program for causing a computer to execute the pulse wave analysis method described in Technology 6.

This makes it possible to provide a program that can properly analyze the pulse wave even when the extreme values that are characteristic points in the acceleration pulse wave waveform have disappeared.

This disclosure can be applied to devices that analyze pulse waves using characteristic points of an acceleration pulse waveform.

REFERENCE SIGNS LIST 10 Pulse wave analysis device 11 Acquisition unit 12 Generation unit 13 Detection unit 14 Output unit

Claims (7)

1. A pulse wave analysis device for analyzing a pulse wave,
   An acquisition unit for acquiring a pulse waveform;
   a generator for generating an acceleration pulse waveform which is a second derivative waveform of the pulse waveform;
   a detection unit for detecting feature points included in the acceleration pulse waveform;
   an output unit that outputs the detected feature points;
   The detection unit is
   For any maximum value present in the accelerated pulse waveform, it is determined whether or not there is an upward inflection point between the maximum value and the minimum value next to the maximum value, and if there is no upward inflection point between the maximum value and the minimum value, the minimum value is detected as a characteristic point, and if there is an upward inflection point between the maximum value and the minimum value, the upward inflection point is detected as a characteristic point, or
   For any minimum value present in the accelerated pulse waveform, it is determined whether or not a downward inflection point exists between the minimum value and the maximum value next to the minimum value, and if the downward inflection point does not exist between the minimum value and the maximum value, the maximum value is detected as a feature point, and if the downward inflection point exists between the minimum value and the maximum value, the downward inflection point is detected as a feature point.
   Pulse wave analysis device.
2. The detection unit is
   A first maximum value in the accelerated pulse waveform is set as an a-wave, and the first maximum value is detected as a feature point;
   determining whether or not an upward inflection point exists between an a-wave and a minimum value next to the a-wave in the accelerated pulse waveform, and if the upward inflection point does not exist between the a-wave and the minimum value, setting the minimum value to the b-wave and detecting the minimum value as a characteristic point, and if the upward inflection point exists between the a-wave and the minimum value, setting the upward inflection point to the b-wave and c-wave and detecting the upward inflection point as a characteristic point;
   when the minimum value next to the a-wave is set to the b-wave, it is determined whether or not a downward inflection point exists between the b-wave and the maximum value next to the b-wave in the accelerated pulse waveform, and when the downward inflection point does not exist between the b-wave and the maximum value, the maximum value is set to the c-wave and detected as a characteristic point, and when the downward inflection point exists between the b-wave and the maximum value, the downward inflection point is set to the c-wave and d-wave and detected as a characteristic point;
   When the upward inflection point following the a-wave is set to the b-wave and c-wave, or when the maximum value following the b-wave is set to the c-wave, it is determined whether or not an upward inflection point exists between the c-wave and the minimum value following the c-wave in the accelerated pulse waveform, and if the upward inflection point does not exist between the c-wave and the minimum value, the minimum value is set to the d-wave and detected as a characteristic point, and if the upward inflection point exists between the c-wave and the minimum value, the upward inflection point is set to the d-wave and e-wave and detected as a characteristic point,
   When the downward inflection point next to the b wave is set to the c wave and d wave, or when the minimum value next to the c wave is set to the d wave, it is determined whether or not a downward inflection point exists between the d wave and the maximum value next to the d wave in the accelerated pulse waveform, and when the downward inflection point does not exist between the d wave and the maximum value, the maximum value is set to the e wave and detected as a characteristic point, and when the downward inflection point exists between the d wave and the maximum value, the downward inflection point is set to the e wave and detected as a characteristic point.
   2. The pulse wave analysis device according to claim 1.
3. moreover,
   The generator generates a velocity pulse waveform which is a first derivative waveform of the pulse waveform,
   the detection unit determines whether or not a downward inflection point exists between a point on the acceleration pulse waveform at the later of a time point of a d-wave on the acceleration pulse waveform or a time point of a minimum value next to a maximum value on the velocity pulse waveform, and a maximum value next to the point; if the downward inflection point does not exist between the point and the maximum value, the detection unit sets the maximum value to an e-wave and detects the maximum value as a characteristic point; and if the downward inflection point exists between the point and the maximum value, the detection unit sets the downward inflection point to an e-wave and detects the downward inflection point as a characteristic point.
   3. The pulse wave analysis device according to claim 2.
4. When the detection unit sets the ascending inflection point subsequent to the c wave to the d wave and e wave, or when the maximum value subsequent to the d wave is set to the e wave, it determines whether or not an ascending inflection point exists between the e wave and the minimum value subsequent to the e wave in the accelerated pulse waveform, and when the ascending inflection point does not exist between the e wave and the minimum value, it sets the minimum value to the f wave and detects the minimum value as a characteristic point, and when the ascending inflection point exists between the e wave and the minimum value, it sets the ascending inflection point to the f wave and detects the ascending inflection point as a characteristic point.
   3. The pulse wave analysis device according to claim 2.
5. moreover,
   The generator generates a velocity pulse waveform which is a first derivative waveform of the pulse waveform,
   the detection unit determines whether or not an upward inflection point exists between a point on the acceleration pulse waveform that is the later of the time of an e-wave on the acceleration pulse waveform and the time of the next minimum value after a maximum value on the velocity pulse waveform, and if the upward inflection point does not exist between the point and the minimum value, sets the minimum value to an f-wave and detects the minimum value as a characteristic point, and if the upward inflection point exists between the point and the minimum value, sets the upward inflection point to an f-wave and detects the upward inflection point as a characteristic point.
   5. The pulse wave analysis device according to claim 4.
6. A pulse wave analysis method executed by a pulse wave analysis device that analyzes a pulse wave, comprising:
   An acquisition step of acquiring a pulse waveform;
   generating an acceleration pulse waveform which is a second derivative waveform of the pulse waveform;
   a detection step of detecting a feature point included in the acceleration pulse waveform;
   and an output step of outputting the detected feature points.
   In the detection step,
   For any maximum value present in the accelerated pulse waveform, it is determined whether or not there is an upward inflection point between the maximum value and the minimum value next to the maximum value, and if there is no upward inflection point between the maximum value and the minimum value, the minimum value is detected as a characteristic point, and if there is an upward inflection point between the maximum value and the minimum value, the upward inflection point is detected as a characteristic point, or
   For any minimum value present in the accelerated pulse waveform, it is determined whether or not a downward inflection point exists between the minimum value and the maximum value next to the minimum value, and if the downward inflection point does not exist between the minimum value and the maximum value, the maximum value is detected as a feature point, and if the downward inflection point exists between the minimum value and the maximum value, the downward inflection point is detected as a feature point.
   Pulse wave analysis method.
7. A program for causing a computer to execute the pulse wave analysis method described in claim 6.

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