JP5328614B2 - Pulse wave analyzer and pulse wave analysis program - Google Patents

Description

  The present invention relates to a pulse wave analysis device and a pulse wave analysis program that can detect a reflected wave contained in a pulse wave of a living body with high accuracy.

  Conventionally, it is known that a pulse wave has various important information for grasping the state of a living body's circulatory system. For example, AI (Augmentation Index) is used for quantitative evaluation of the degree of arteriosclerosis in the whole body, estimation of central arterial pressure, etc. by calculating the ratio of the ejection wave component and the reflected wave component contained in the pulse wave. It is used.

  In order to obtain the AI, it is necessary to specify each of the ejection wave component and the reflected wave component included in the pulse wave, and a technique for that purpose is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2004-31468) and the like. Has been. In Patent Document 1, the ejection wave component and the reflected wave component are obtained by waveform analysis based on the differentiation of the pulse wave.

  In addition, regarding the pulse wave velocity obtained by measuring the pulse wave at two measurement sites, the ejection wave and the reflected wave are separated, and the time difference between the ejection wave and the reflected wave is used to determine the velocity at one measurement site. Japanese Patent Laid-Open No. 2003-010139 discloses a technique for identifying the pulse wave velocity from the pulse wave.

On the other hand, the pulse wave rises with the heartbeat, then gradually falls, and rises again with the next heartbeat. The waveform of this pulse wave is determined by the motion of the heart and the elastic characteristics of the artery. As described above, since the pulse wave is important biological information for grasping the state of the circulatory system of the living body, various efforts for modeling the waveform of the pulse wave have been made. For example, non-patent documents 1 and the like disclose that it can be modeled by the following equation (1).
P (t) = Ps · exp (−λ · t) (1)
Ps: systolic blood pressure
λ: Reciprocal of time constant

  By the way, in the above-mentioned patent document 1 and patent document 2, the technique which isolate | separates a ejection wave and a reflected wave is disclosed, and especially patent document 1 classify | categorizes the waveform of a pulse wave, and is suitable for each of the classified waveform. A technique capable of appropriately separating ejected waves and reflected waves by performing simple waveform analysis is disclosed.

  However, even if the temporal positional relationship in the pulse wave of one beat can be correctly specified for each of the ejection wave and the reflected wave, the amplitude of the reflected wave alone cannot be correctly specified. Because, as described in Non-Patent Document 1, the pulse wave rises with the beat of the heart, but then falls with a certain time constant, so even in the time when the reflected wave exists, There is a residual amplitude of the ejection wave. In other words, even if the temporal position of the reflected wave in the pulse wave is identified, the amplitude at that time is the result of combining the remaining component of the ejected wave and the reflected wave, so the amplitude of the reflected wave alone Cannot be identified correctly.

  Therefore, when comparing the magnitude of the ejected wave and the reflected wave using the AI or the like, the time of the reflected wave in the pulse wave is compared in order to more accurately compare the magnitude of the ejected wave and the reflected wave. It is required to specify the residual component of ejected waves at various positions.

JP 2004-313468 A JP 2003-010139 A

Hahn, Jin-Oh “A system identification approach to non-invasive central cardiovascular monitoring”, Ph.D. Thesis, Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.

  Accordingly, an object of the present invention is to provide a pulse wave analysis device and a pulse wave analysis program that can more accurately detect a reflected wave component and an ejected wave component of a pulse wave.

In order to solve the above problems, a pulse wave analysis device according to the present invention includes a pulse wave detection unit that detects a pulse wave in a certain part of a living body,
A reference for detecting a reference time for specifying the ejection wave component included in the pulse wave at the partial position detected by the pulse wave detection unit and a reference time for specifying the reflected wave component included in the pulse wave A time detector;
The amplitude of the pulse wave corresponding to the reference time of the ejection wave component detected by the reference time detection unit is detected and the pulse wave corresponding to the reference time of the reflected wave component detected by the reference time detection unit is detected. A pulse wave amplitude detector for detecting amplitude;
Based on the reference time of the ejection wave component detected by the reference time detection unit and the amplitude of the pulse wave corresponding to the reference time of the ejection wave component, the waveform of the ejection wave component included in the pulse wave is obtained. The modeled wave is obtained by modeling, and the pulse wave is based on the reference time of the reflected wave component detected by the reference time detection unit and the amplitude of the pulse wave corresponding to the reference time of the reflected wave component. A waveform modeling unit that models the waveform of the reflected wave component contained in to obtain a modeled reflected wave;
A model wave amplitude deriving unit that obtains the amplitude of the ejected wave component and the amplitude of the reflected wave component at a desired phase of the pulse wave from the modeled ejected wave and the modeled reflected wave modeled by the waveform modeling unit; It is characterized by providing.

  According to the pulse wave analysis apparatus of the present invention, the reference time detecting unit detects the reference time for specifying the ejection wave component and the reflection component of the pulse wave, and the pulse wave amplitude detection unit detects the ejection wave. The amplitude of the pulse wave corresponding to the reference time for specifying the component and the reflected wave component is detected. Then, based on the reference time for specifying the ejection wave component and the reflected wave component and the amplitude of the pulse wave corresponding to the reference time of the ejection wave component and the reflected wave component, the waveform modeling unit The ejection wave and the reflected wave included in the pulse wave are modeled, and the model wave amplitude deriving unit calculates the ejection wave component in the desired phase of the pulse wave from the modeled ejection wave and the modeled reflection wave. The amplitude and the amplitude of the reflected wave component are obtained. Therefore, the reflected wave component and ejected wave component of the pulse wave can be detected more accurately, and the biological index based on the accurate reflected wave component and ejected wave component of the pulse wave can be obtained more accurately.

In the pulse wave analysis program of one embodiment, the reference time for specifying the ejection wave component included in the pulse wave in a certain part of the living body and the reflected wave component included in the pulse wave are specified. A reference time deriving function for obtaining a reference time;
The amplitude of the pulse wave corresponding to the reference time of the reflected wave component obtained by the reference time deriving function and the amplitude of the pulse wave corresponding to the reference time of the ejection wave component obtained by the reference time deriving function A pulse wave amplitude derivation function for
Based on the reference time of the ejection wave component obtained by the reference time deriving function and the amplitude of the pulse wave corresponding to the reference time of the ejection wave component, the waveform of the ejection wave component included in the pulse wave is calculated. The modeled ejection wave is modeled to obtain the pulse wave based on the reference time of the reflected wave component obtained by the reference time deriving function and the amplitude of the pulse wave corresponding to the reference time of the reflected wave component. Modeling the waveform of the reflected wave component contained in the waveform modeling function to obtain the modeled reflected wave,
A model wave amplitude derivation function that obtains the amplitude of the ejected wave component and the reflected wave component at the desired phase of the pulse wave from the modeled ejected wave and modeled reflected wave modeled by the waveform modeling function Let the computer run.

  According to the pulse wave analysis program of this embodiment, the computer executes the reference time derivation function to obtain the reference time of the ejection wave component of the pulse wave and the reference time of the reflection component, and the pulse wave amplitude derivation function. Thus, the amplitude of the pulse wave corresponding to the reference time of the ejection wave component and the reflection component is obtained. Based on the reference time of the ejected wave component and reflected wave component and the amplitude of the pulse wave corresponding to the reference time, the ejected wave and reflected wave included in the pulse wave are modeled by the waveform modeling function. The amplitude of the ejected wave component and the amplitude of the reflected wave component in the desired phase of the pulse wave are obtained from the modeled modeled ejected wave and modeled reflected wave. Therefore, the reflected wave component and ejected wave component of the pulse wave can be obtained more accurately, and the biological index based on the accurate reflected wave component and ejected wave component of the pulse wave can be obtained more accurately.

  According to the pulse wave analysis device of the present invention, based on the reference time for identifying the ejection wave component and the reflection component of the pulse wave and the amplitude of the pulse wave corresponding to the reference time for identifying the ejection wave component and the reflection component. Then, the waveform of the ejection wave and the waveform of the reflected wave included in the pulse wave are modeled, and the ejection wave component in the desired phase of the pulse wave is modeled from the modeled ejection wave and the modeled reflected wave. The amplitude and the amplitude of the reflected wave component are obtained. Therefore, according to the pulse wave analysis apparatus of the present invention, the reflected wave component and the ejected wave component of the pulse wave can be detected more accurately, and the biological index based on the accurate reflected wave component and the ejected wave component of the pulse wave can be further improved. It can be obtained accurately.

It is a block diagram which shows embodiment of the pulse-wave analyzer of this invention. FIG. 4 is a waveform diagram showing a pulse wave waveform detected by the pulse wave detection unit of the embodiment in a column (A) and an acceleration waveform of the pulse wave in a column (B). It is a wave form diagram which shows the 3rd derivative waveform of the pulse wave detected by the above-mentioned pulse wave detection part in the (A) column, and shows the 4th derivative waveform of the above-mentioned pulse wave in the (B) column. It is a waveform diagram showing the pulse wave amplitude and pulse wave amplitudes W1 and W2 at the reference points Q1 and Q2 of the pulse wave. It is a wave form diagram which shows the waveform of the said pulse wave, and the ejection wave component S1 and the reflected wave component S2 of the said pulse wave. 4 is a waveform diagram showing how each of the ejection wave component S1 and the reflected wave component S2 contributes to the pulse wave S. FIG.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1 is a block diagram showing a pulse wave analyzer 10 according to an embodiment of the present invention. The pulse wave analysis device 10 includes a pulse wave detection unit 1 that detects a pulse wave in a certain part of a human body. As this pulse wave detection unit 1, for example, there is a unit that measures the degree to which infrared light output from a light emitting element is reflected or absorbed according to the blood volume in a blood vessel (photoelectric volume pulse wave method). In addition, a device that detects a pulse wave by a pressure pulse wave method that extracts a change in pressure of blood in the blood vessel pushing the blood vessel as an electrical signal may be used. In addition, the body part for measuring the pulse wave by the pulse wave detector 1 is not particularly limited, but is preferably a non-invasive / non-constrained part. -Wrist and earlobe are preferred.

  Further, the pulse wave analyzing apparatus 10 includes a reference time for specifying each of the ejection wave component and the reflected wave component included in the pulse wave detected by the pulse wave detection unit 1 and the above-mentioned corresponding to the reference time. The ejection wave / reflected wave information extracting unit 6 for detecting the amplitude of the pulse wave, and the pulse wave model based on the reference time and the information representing the amplitude from the ejected wave / reflected wave information extracting unit 6 To determine the amplitude of the ejected wave component and the reflected wave component at the desired phase of the pulse wave from the modeled ejected wave and the modeled reflected wave. A wave / reflected wave component contribution detection unit 5 is provided.

  The ejection wave / reflected wave information extraction unit 6 calculates a reference time for specifying the ejection wave component included in the pulse wave detected by the pulse wave detection unit 1 and the reflected wave component included in the pulse wave. It has a reference time detector 2 that detects a reference time for identification.

  An example of a process in which the reference time detection unit 2 calculates the reference time will be described below. First, an example of a pulse wave waveform detected by the pulse wave detector 1 is shown in the (A) column of FIG. 2A. The vertical axis in the column (A) of FIG. 2A represents the measured voltage value (V) corresponding to the amplitude (mmHg) of the pulse wave. In the pulse wave analysis device 10 of this embodiment, as an example, the voltage value (V) measured by the pulse wave detector 1 with the blood pressure (mmHg) measured by a general cuff sphygmomanometer is the amplitude of the pulse wave. Correction (calibration) of how to correspond to (mmHg) is performed. This correction (calibration) may be performed at the start of the first use, and the calibration result may be used in subsequent measurements.

  For example, when the pulse wave is Type C of blood pressure waveform classification by Murgo et al., The reference time detection unit 2 is the time of the systolic maximum point Q1 in the pulse wave waveform shown in the column (A) of FIG. 2A. T1 is detected as the reference time T1 of the ejection wave component. The (B) column of FIG. 2A shows the acceleration wave of the pulse wave, and the (A) column of FIG. 2B shows the triple differential wave of the pulse wave. For example, when the pulse wave is Type C of blood pressure waveform classification by Murgo et al., The reference time detection unit 2 performs the third zero cross of the fourth-order differential wave of the pulse wave shown in the (B) column of FIG. 2B. The point Q2 is detected as the reference time T2 of the reflected wave component. The third zero-cross point Q2 means a point at which the fourth differential waveform shown in FIG. 2B (B) zero-crosses downward for the third time after the pulse wave shown in FIG. 2A (A) has reached the minimum value. To do.

  In the above description, the case where the detected pulse wave is Type C of the blood pressure waveform classification has been described. However, when the detected pulse wave has a waveform shape other than Type C of the blood pressure waveform classification, If there is a method that can suitably specify the reference time of the ejection wave component of the pulse wave and the reference time of the reflected wave component, it may be adopted. For example, if the pulse wave does not show a large blood pressure fluctuation, it basically does not show a very large waveform change, so by superimposing a plurality of measured pulse waves (addition averaging), the pulse wave detection accuracy can be improved. It becomes possible to plan.

  In addition, since the pulse wave shows various waveform shapes depending on the noise level, age, sex, presence / absence of disease, physical condition, etc., the reference time of the ejection wave component of the pulse wave and the reflected wave component are more preferably If there is a method that can specify the reference time, it may be adopted. For example, it is possible to improve the accuracy of specifying the reference time of the ejection wave component of the pulse wave and the reference time of the reflected wave component by leaving the detected pulse wave as a history together with the state of the measurement subject at that time. .

  The ejection wave / reflected wave information extraction unit 6 includes a pulse wave amplitude detection unit 3. The pulse wave amplitude detector 3 drives the amplitude W1 of the pulse wave S corresponding to the reference time T1 of the ejected wave component detected by the reference time detector 2, as illustrated in the waveform diagram of FIG. While detecting as the pulse wave amplitude of the outgoing wave component, the amplitude W2 of the pulse wave S corresponding to the reference time T2 of the reflected wave component detected by the reference time detector 2 is detected as the pulse wave amplitude of the reflected wave component. The above-described content is a method adopted in AI (Augmentation Index) which has been used as a diagnostic index for the circulatory system in recent years.

  Then, the ejection wave / reflected wave information extraction unit 6 uses the ejection wave to obtain information indicating the reference time T1 of the ejection wave component detected by the reference time detection unit 2 and the reference time T2 of the reflected wave component. The amplitude W1 of the pulse wave S corresponding to the reference time T1 of the ejection wave component detected by the pulse wave amplitude detection unit 3 and the reference time of the reflected wave component are input to the reflected wave component contribution degree detection unit 5 Information representing the amplitude W2 of the pulse wave S corresponding to T2 is input to the ejection wave / reflected wave component contribution detection unit 5.

  By the way, as illustrated in the waveform diagram of FIG. 4, the pulse wave amplitude W2 measured in the vicinity of the reference time T2 of the reflected wave component S2 includes not only the reflected wave component W3 but also the ejection wave component. There are many cases. For this reason, in the ejection wave / reflected wave component contribution degree detection unit 5 to be described next, assuming that the pulse wave S is a composite wave of the ejection wave and the reflected wave, the ejection wave and the reflected wave to the pulse wave S Each contribution is detected.

  That is, the ejection wave / reflected wave component contribution detection unit 5 includes a waveform modeling unit 7 and a single amplitude information detection unit 8. The waveform modeling unit 7 includes the ejection wave included in the pulse wave S based on the reference time T1 of the ejection wave component and the amplitude W1 of the pulse wave S corresponding to the reference time T1 of the ejection wave component. The waveform of the wave component S1 is modeled to obtain a modeled ejection wave. In addition, the waveform modeling unit 7 includes a reference time T2 of the reflected wave component S2 detected by the reference time detection unit 2 and a reflected wave component S2 of the pulse wave S corresponding to the reference time T2 of the reflected wave component S2. Based on the amplitude W3, the waveform of the reflected wave component S2 included in the pulse wave S is modeled to obtain a modeled reflected wave.

For example, the waveform modeling unit 7 performs the modeled ejection wave based on the reference time T1 of the ejection wave component and the amplitude W1 of the pulse wave S corresponding to the reference time T1 of the ejection wave component. The amplitude WS1 (t) at time t after the reference time T2 of S1 is modeled as the following equation (2).
WS1 (t) = W1 · exp (−λ (t−T1)) (2)

  In the above equation (2), λ is the reciprocal of the falling time constant of the pulse wave. In this equation (2), the reciprocal λ of the time constant is an unknown number.

On the other hand, the waveform modeling unit 7 is based on, for example, the reference time T2 of the reflected wave component and the amplitude W3 of the reflected wave component of the pulse wave S corresponding to the reference time T2 of the reflected wave component. The amplitude WS2 (t) at the time t after the reference time T2 of the modeled reflected wave S2 is modeled as the following equation (3).
WS2 (t) = W3 · exp (−λ (t−T2)) (3)

  In the above equation (3), the amplitude W3 of the reflected wave component at the reference time T2 and the inverse λ of the time constant are unknown parameters. The above formulas (2) and (3) correspond to those obtained by applying the formula (1) described in Non-Patent Document 1 to the ejection wave and the reflected wave.

From the above equations (2) and (3), the amplitude W (t) of the pulse wave S after the reference time T2 is expressed by the following equation (4).
W (t) = W1 · exp (−λ (t−T1))
+ W3 · exp (−λ (t−T2)) (4)

  Next, the single amplitude information detection unit 8 uses the above equation (4) obtained by the waveform modeling unit 7 to use the single amplitude of each of the ejection wave component S1 and the reflected wave component S2 of the pulse wave S. Detect information. This will be described below.

The right side of the above equation (4) indicates that it can accurately represent how much the amplitude of each of the ejection wave component and the reflected wave component contributes to the whole pulse wave (the waveform in FIG. 5). (See figure). By substituting the reference time T2 of the reflected wave component into the above equation (4), the following equation (5) is obtained, and by substituting the time T when the minimum value W0 of the pulse wave S is substituted into the above equation (4). The following equation (6) is obtained (see the waveform diagram of FIG. 5).
W (T2) = W1 · exp (−λ (T2−T1)) + W3 = W2 (5)
W (T) = W1 · exp (−λ (T−T1)) + W3 · exp (−λ (T−T2))
= W0 (6)

In the above equations (5) and (6), there are two unknown parameters, the reciprocal λ of the time constant and the amplitude W3 of the reflected wave component at the reference time T2, so the above two equations (5) and (6) Can solve simultaneous equations. That is, the following equation (7) is obtained from the above equation (5).
W3 = W2−W1 · exp (−λ (T2−T1)) (7)

Substituting W3 by this equation (7) into the above equation (6), the following equation (8) is obtained.
W1 · exp (−λ (T−T1)) + W2 · exp (−λ (T−T2)
−W1 · exp (−λ (T2−T1)) · exp (−λ (T−T2)) = W0
W2 · exp (−λ (T−T2)) = W0
−λ (T−T2) = ln (W0 / W2)
λ = {ln (W0 / W2)} / (T2-T) (8)

  From this equation (8), the reciprocal λ of the time constant is obtained from the known parameters. Therefore, by substituting λ obtained by this equation (8) into the above equation (7), the amplitude W3 of the reflected wave component at the reference time T2 can be obtained from the known parameters.

  From the reciprocal λ of the time constant obtained in this way, the amplitude W3 of the reflected wave component at the reference time T2, and the above equation (4), the amplitude W (t) at any time after the reference time T2 of the pulse wave S is obtained. can get. That is, according to the above equation (4), it is possible to detect individual amplitude information of the ejection wave component S1 and the reflected wave component S2 of the pulse wave S.

  In the above embodiment, the above equation (1) is adopted as a pulse waveform modeling by the method described in Non-Patent Document 1, but it is not limited to this equation. If there is a more preferable formula, it may be adopted. In the present invention, the individual contributions of the ejection wave component and the reflected wave component can be obtained using various model equations.

  In recent years, in addition to conventional indicators such as the maximum value (maximum blood pressure) and the minimum value (minimum blood pressure) or the difference (pulse pressure) in pulse waves, AI (Augmentation Index), ejection waves and reflected waves A new biometric index used is attracting attention. These biological indices can be obtained more accurately based on the individual contributions of the ejection wave and the reflected wave obtained by the present invention. Therefore, according to the pulse wave analysis apparatus of the present invention, it is useful for grasping the state of the living body. Naturally, the pulse wave analysis device of the present invention can be used not only for AI but also for other biological indices using ejection waves and reflected waves.

  As described above, the reference time detection unit 2 obtains the reference time T1 and T2, and the pulse wave amplitude detection unit 3 detects the amplitude of the pulse wave S corresponding to the reference times T1 and T2. The pulse wave amplitude deriving function for obtaining W1 and W2, and the waveform modeling unit 7 modeling the waveform of the ejection wave component of the pulse wave S to obtain the modeled ejection wave and the reflected wave component of the pulse wave S A waveform modeling function for modeling the waveform of the waveform and obtaining a modeled reflected wave, and the single amplitude information detecting unit 8 from the modeled ejected wave and the reflected wave, the single amplitude of each of the ejected wave and the reflected wave. A model wave amplitude deriving function for detecting information may be executed by a computer using a pulse wave analysis program.

DESCRIPTION OF SYMBOLS 1 Pulse wave detection part 2 Reference time detection part 3 Pulse wave amplitude detection part 5 Ejection wave / reflected wave component contribution degree detection part 6 Ejection wave / reflected wave information extraction part 7 Waveform modeling part 8 Single amplitude information detection part 10 Pulse wave analyzer Q1 Pulse wave maximum point Q2 Pulse wave third zero cross point S Pulse wave S1 Ejection wave component S2 Reflected wave component T1 Ejection wave component reference time T2 Reflected wave component reference time W1 Reference time T1 Amplitude of ejected wave component W2 Amplitude of pulse wave at reference time T2 W3 Amplitude of reflected wave component at reference time T2

Claims (2)

A pulse wave detector for detecting a pulse wave in a certain part of the living body;
A reference for detecting a reference time for specifying the ejection wave component included in the pulse wave at the partial position detected by the pulse wave detection unit and a reference time for specifying the reflected wave component included in the pulse wave A time detector;
The amplitude of the pulse wave corresponding to the reference time of the ejection wave component detected by the reference time detection unit is detected and the pulse wave corresponding to the reference time of the reflected wave component detected by the reference time detection unit is detected. A pulse wave amplitude detector for detecting amplitude;
Based on the reference time of the ejection wave component detected by the reference time detection unit and the amplitude of the pulse wave corresponding to the reference time of the ejection wave component, the waveform of the ejection wave component included in the pulse wave is obtained. The modeled wave is obtained by modeling, and the pulse wave is based on the reference time of the reflected wave component detected by the reference time detection unit and the amplitude of the pulse wave corresponding to the reference time of the reflected wave component. A waveform modeling unit that models the waveform of the reflected wave component contained in to obtain a modeled reflected wave;
A model wave amplitude deriving unit that obtains the amplitude of the ejected wave component and the amplitude of the reflected wave component at a desired phase of the pulse wave from the modeled ejected wave and the modeled reflected wave modeled by the waveform modeling unit; A pulse wave analysis device comprising: A reference time deriving function for obtaining a reference time for specifying the ejection wave component included in the pulse wave in a certain part of the living body and a reference time for specifying the reflected wave component included in the pulse wave;
The amplitude of the pulse wave corresponding to the reference time of the reflected wave component obtained by the reference time deriving function and the amplitude of the pulse wave corresponding to the reference time of the ejection wave component obtained by the reference time deriving function A pulse wave amplitude derivation function for
Based on the reference time of the ejection wave component obtained by the reference time deriving function and the amplitude of the pulse wave corresponding to the reference time of the ejection wave component, the waveform of the ejection wave component included in the pulse wave is calculated. The modeled ejection wave is modeled to obtain the pulse wave based on the reference time of the reflected wave component obtained by the reference time deriving function and the amplitude of the pulse wave corresponding to the reference time of the reflected wave component. Modeling the waveform of the reflected wave component contained in the waveform modeling function to obtain the modeled reflected wave,
A model wave amplitude derivation function that obtains the amplitude of the ejected wave component and the reflected wave component at the desired phase of the pulse wave from the modeled ejected wave and modeled reflected wave modeled by the waveform modeling function A pulse wave analysis program that is executed by a computer.

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