JP7290768B2 - detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a detection device, and more particularly to the technical field of a detection device that detects blood flow using shunt sound.

For this type of device, for example, at least one of sound, blood circuit vibration, and blood pressure is converted into an electric signal, and after the electric signal is converted into a frequency-sound pressure system by frequency analysis, a shunt sound is generated. There has been proposed a device for measuring a pulse by extracting only a frequency band in which frequency components are present (see Patent Document 1).

Japanese Patent No. 4257260

For example, during dialysis treatment, blood may be drawn from a patient after a shunt is formed by anastomosing a vein and an artery near the wrist. A blood vessel in the vicinity of a shunt (hereinafter referred to as a "shunt formation site" as appropriate) is often constricted due to, for example, blood coagulation. For this reason, doctors and nurses, for example, auscultate the shunt sound (that is, the noise generated when blood flows from an artery to a vein), or measure the blood flow at the shunt formation site by echo examination. In many cases, the state of the formation site is grasped and evaluated. However, when auscultating the shunt sound, the evaluation of the state of the shunt portion varies from person to person, making objective evaluation difficult. Also, in the case of echo examination, it is necessary to acquire a certain amount of skill.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a detection device capable of detecting a blood flow rate from a shunt sound.

The detection device of the embodiment provides shunt sound information indicating the shunt sound of a shunt-formed site of a living body, which is a measurement target, in which a shunt is formed by anastomosing a vein in the vicinity of the wrist or the cubital region with the brachial artery. from auscultation means, and reference information indicating the correlation between the intensity of the shunt sound at the shunt formation site and the blood flow rate of the brachial artery upstream from the shunt formation site, the reference information blood in the brachial artery of the living body based on the intensity of the shunt sound based on the shunt sound information acquired by the first acquisition means and the reference information; estimating means for estimating the flow rate.

The operation and other advantages of the present invention will become apparent from the detailed description that follows.

1 is a block diagram showing the configuration of a detection device according to an example; FIG. It is a figure which shows an example of the analysis processing result of a shunt sound signal. It is a figure which shows the detection concept of a shunt sound and blood flow. FIG. 4 is a diagram showing an example of the relationship between the intensity of shunt sound and blood flow.

An embodiment of the detection device of the present invention will be described.

The detection device of the embodiment provides shunt sound information indicating the shunt sound of a shunt-formed site of a living body, which is a measurement target, in which a shunt is formed by anastomosing a vein in the vicinity of the wrist or the cubital region with the brachial artery. from auscultation means, and reference information indicating the correlation between the intensity of the shunt sound at the shunt formation site and the blood flow rate of the brachial artery upstream from the shunt formation site, the reference information and a blood flow rate at the shunt formation site based on the intensity of the shunt sound based on the shunt sound information acquired by the first acquisition means and the reference information estimating means for estimating the

According to research by the inventor of the present application, it has been found that there is a relatively strong correlation between the intensity of the shunt sound and the blood flow rate at the shunt formation site. Therefore, according to the detection device, the blood flow rate at the shunt formation site can be detected from the shunt sound. In particular, according to the detection device, the blood flow rate at the shunt formation site can be objectively detected without depending on the operator of the detection device.

In one aspect of the detection device of the embodiment, the second acquisition means is provided for acquiring reference information indicating the relationship between the intensity of the shunt sound and the blood flow rate, and the calculation means includes the intensity of the shunt sound and the reference information based on the shunt sound information. , the blood flow rate at the shunt formation site is calculated. According to this aspect, the blood flow rate at the shunt formation site can be detected relatively easily.

In another aspect of the detection device of the embodiment, the calculation means has an analysis means for obtaining data indicating the time change for each frequency of the sound by performing a predetermined analysis process on the shunt sound information. According to this aspect, the intensity of the shunt sound can be obtained relatively easily.

In this aspect, the calculation means may specify the intensity of the shunt sound based on the data corresponding to the predetermined frequency band among the data. With this configuration, it is possible to suppress the influence of environmental noise, for example.

In this aspect, the calculation means may specify the intensity of the shunt sound based on the data corresponding to the predetermined period among the data. This predetermined period may be a period corresponding to systole. With this configuration, for example, the influence of arrhythmia can be suppressed.

In another aspect of the detection device of the embodiment, the first acquiring means acquires shunt sound information indicating a shunt sound having a predetermined frequency or less among the shunt sounds of the shunt formation site. According to this aspect, it is possible to suppress the influence of environmental noise, for example.

An embodiment of the detection device of the present invention will be described. First, the configuration of the detection device according to the embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of a detection device according to an embodiment.

In FIG. 1 , the detection device 1 includes a shunt sound input section 11 , an audio signal analysis processing section 12 , an intensity parameter calculation section 13 , a blood flow estimation section 14 and a blood flow estimated value display section 15 .

Next, each component of the detection device 1 will be described. The shunt sound input unit 11 receives an analog signal representing the sound of the shunt formation site to be measured (that is, the sound including the shunt sound) detected by the electronic stethoscope 20 . The shunt sound input unit 11 performs analog-to-digital conversion on the input analog signal at a predetermined sampling frequency Fs to calculate a shunt sound waveform. The shunt sound input section 11 may be formed integrally with the electronic stethoscope 20 .

The speech signal analysis processing unit 12, the intensity parameter calculation unit 13, and the blood flow estimation unit 14 constitute a calculation unit. The audio signal analysis processing unit 12 performs an N-point short-time Fourier transform on the value x(n) of the time n of the shunt sound waveform calculated by the shunt sound input unit 11 in units of frames of length N ( (see formula below). Here, the audio signal analysis processing unit 12 uses the N-length window function w(k) to cut out the N-length frame.

"k=0...N-1" means the frequency position (height) in units of N equal divisions of the sampling frequency Fs.

The audio signal analysis processing unit 12 applies logarithmic transformation to the short-time Fourier-transformed shunt sound waveform to calculate a time-frequency analysis waveform PLog[n, k]. The time-frequency analysis waveform PLog[n, k] is represented by the following equation.

The intensity parameter calculator 13 extracts data corresponding to a predetermined frequency band and a predetermined period from the time-frequency analysis waveform PLog[n, k], and obtains the intensity of the shunt sound. Here, the predetermined frequency band and predetermined period will be described with reference to FIG. FIG. 2 is a diagram showing an example of the analysis processing result of the shunt sound signal (that is, the time-frequency analysis waveform PLog[n, k]).

In order to perform dialysis safely and efficiently, sufficient blood flow is required at the site of shunt formation. Sounds detected by the electronic stethoscope 20 include, in addition to shunt sounds caused by shunt formation sites, environmental noises and noises such as high-pitched sounds caused by stenosis.

Noise often appears in a frequency band of, for example, 400 to 800 Hz (see the portion surrounded by the dotted line circle in FIG. 2(a)). On the other hand, the shunt sound is detected as sound in a relatively low frequency band such as 100-500 Hz. Therefore, in this embodiment, in order to reduce the influence of noise, for example, a frequency band of 100 to 300 Hz is set as the predetermined frequency band (see "target band" in FIG. 2(a)).

In addition, in this embodiment, in order to emphasize the shunt sound caused by the shunt formation site synchronized with the heartbeat and to reduce the influence of time fluctuations in diastole due to arrhythmia, the systole is set as the predetermined period. is set (see FIG. 2(b)). Here, in the systole, one heartbeat interval is detected from the time change in volume based on the time-frequency analysis waveform PLog[n, k], and the volume in the first half of the detected one heartbeat interval and/or one heartbeat interval is set as 100%, for example, as a volume period of 80% to 100%.

Specifically, the intensity parameter calculator 13 obtains the intensity of the shunt sound using the following formula. In the following formula, “r1”, “r2”, “t1” and “t2” are respectively “lower limit frequency of target band”, “upper limit frequency of target band”, “start time of systole” and “systole means the end time of

The blood flow estimator 14 estimates the blood flow at the shunt formation site based on the intensity of the shunt sound obtained by the intensity parameter calculator 13 and reference information defining the relationship between the intensity of the shunt sound and the blood flow. . Here, the reference information will be explained with reference to FIGS. 3 and 4. FIG. FIG. 3 is a diagram showing the detection concept of shunt sound and blood flow. FIG. 4 is a diagram showing an example of the relationship between the intensity of the shunt sound and the blood flow.

When the subject is a human, as shown in FIG. 3, a shunt is often formed by anastomosing the vein near the wrist with the brachial artery. In this case, in the echo examination, the blood flow in the brachial artery is measured as the blood flow in the shunt formation site. The relationship between blood flow measured by echography and stenosis is relatively clear.

As an example, when a shunt is formed by anastomosing a vein in the vicinity of the wrist with the brachial artery, as shown in FIG. to measure. When the intensity of the shunt sound and the blood flow at the same time are associated with each other and plotted on a plane having the axis of the intensity of the shunt sound and the blood flow, the result shown in FIG. 4 is obtained, for example. For example, the approximate straight line “y=ax+b” based on this result is an example of “reference information” according to the present embodiment. The reference information is stored in advance in the strength parameter calculator 13, for example.

The blood flow estimated value display section 15 displays the blood flow estimated by the blood flow estimation section 14 . As shown in FIG. 4, there is a relatively strong correlation between the intensity of the shunt sound and the blood flow. Therefore, it can be said that the blood flow estimated by the blood flow estimation unit 14 is relatively accurate.

The "shunt sound input unit 11", the "audio signal analysis processing unit 12", and the "strength parameter calculation unit 13" according to the embodiment are equivalent to the "first obtaining means", "analysis means", and "second obtaining means" according to the present invention. It is an example of "means".

The detection device 1 is applicable not only to humans but also to dogs and cats, for example. When the detection device 1 is applied to dogs and cats, for example, reference information that defines the relationship between the intensity of the shunt sound and the blood flow for dogs and cats may be stored in the intensity parameter calculator 13 in advance. .

<First modification>
In the above-described embodiment, when obtaining the intensity of the shunt sound, data corresponding to a predetermined frequency band (for example, 100 to 300 Hz) of the time-frequency analysis waveform PLog[n, k] and corresponding to the systole are used. I am using However, the intensity of the shunt sound may be obtained using data corresponding to a predetermined frequency band (for example, 100 to 300 Hz) of the time-frequency analysis waveform PLog[n, k].

Specifically, the intensity parameter calculator 13 may obtain the intensity of the shunt sound by the following formula. In the following formula, "T" means "end time of one heartbeat interval".

<Second modification>
In the above-described embodiment, the intensity parameter calculator 13 extracts data corresponding to a predetermined frequency band from the time-frequency analysis waveform PLog[n, k]. In this modified example, the shunt sound input section 11 is provided with, for example, a bandpass filter or a lowpass filter. Then, the shunt sound input unit 11 performs analog-to-digital conversion on sounds corresponding to a predetermined frequency band among the sounds detected by the electronic stethoscope 20 to calculate a shunt sound waveform.

<Third modification>
In the above-described embodiment, analog-to-digital conversion is performed in the shunt sound input unit 11, but analog-to-digital conversion is performed in, for example, the electronic stethoscope 20 or another device other than the electronic stethoscope 20 and the detection device 1. The resulting sound (ie, shunt sound waveform) may be input to the shunt sound input section 11 .

The present invention is not limited to the above-described embodiments, and can be modified as appropriate within a range that does not contradict the gist or idea of the invention that can be read from the scope of claims and the entire specification. It is also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Detection apparatus 11... Shunt sound input part 12... Sound signal analysis process part 13... Intensity parameter calculation part 14... Blood flow estimation part 15... Blood flow estimated value display part 20... Electronic stethoscope

Claims (6)

Acquiring, from an auscultatory means, shunt sound information indicating the shunt sound of a shunt-formed site of a living body, where a shunt is formed by anastomosing a vein near the wrist or the cubital region of a living body to be measured with a brachial artery. 1 obtaining means;
obtaining reference information indicating the correlation between the intensity of the shunt sound at the shunt formation site and the blood flow rate of the brachial artery upstream from the shunt formation site from storage means storing the reference information in advance; 2 acquisition means;
estimating means for estimating the blood flow rate of the shunt formation site based on the intensity of the shunt sound based on the shunt sound information acquired by the first acquisition means and the reference information;
A detection device comprising: 2. The detecting device according to claim 1, wherein said estimating means has analyzing means for obtaining data indicating temporal change for each sound frequency by performing a predetermined analysis process on said shunt sound information. 3. The detecting device according to claim 2, wherein said estimating means specifies the intensity of the shunt sound based on data corresponding to a predetermined frequency band among said data. 4. The detecting device according to claim 2, wherein said estimating means specifies the intensity of the shunt sound based on data corresponding to a predetermined period among said data. 5. The detection device according to claim 4, wherein the predetermined period is a period corresponding to systole. 2. The detecting device according to claim 1, wherein said first acquiring means acquires shunt sound information indicating a shunt sound having a predetermined frequency or less among said shunt sounds of said shunt forming portion.

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