JP4257260B2 - Pulse measurement device using shunt sound - Google Patents

Description

The present invention relates to a pulse measuring device using a shunt sound during extracorporeal blood treatment including blood purification therapy such as hemodialysis, blood filtration, blood filtration dialysis, and blood purification.

  Conventionally, patients undergoing extracorporeal blood treatment, for example, dialysis treatment, create a shunt (also referred to as blood access) in which a vein and an artery near the wrist are anastomosed, and extracorporeal circulating blood of about 200 [ml / min] required for dialysis. Getting the flow rate.

  By creating a shunt, arterial blood flow is drawn to the venous side. This becomes a factor that causes a rapid change in the flow path diameter and flow path shape of the blood vessel, and generates a blood flow sound and vibration sound due to blood vessel vibration at the anastomosis. Conventionally, the blood flow volume and the vibration sound are acquired as a shunt sound by using a stethoscope or a heart sound sensor.

  The shunt is often constricted due to blood coagulation, etc., and dialysis patients or medical staff routinely auscultate shunt sounds, assess the loudness and frequency of the shunt, and grasp the shunt status to ensure good blood removal. It is managed so that it can be obtained. The technique of collecting shunt sounds and grasping the shunt state is realized in Japanese Patent No. 3083378 (Patent Document 1) and Japanese Patent Laid-Open No. 10-52490 (Patent Document 2).

  The device described in Patent Document 1 automatically and continuously performs blood flow in a shunt portion, which is a means for extracting blood from a living body for extracorporeal circulation that guides blood to an artificial organ in hemodialysis or filtration therapy. In this way, it is possible to reduce the trouble that the patient has to confirm the blood flow state many times every day by auscultation and to detect the deterioration of the blood flow state at an early stage.

  For this reason, in order to continuously detect the shunt sound corresponding to the blood flow, the microphone is fixed with the adhesive bandage in the vicinity of the arterial and venous coupling means, while the shunt sound changes due to the deterioration of the circulation state. A detection circuit for inputting a detection value in a microphone to be compared with a lower limit value of a preset shunt volume, a control circuit for emitting a signal when the detection value falls below the lower limit value, and a signal generated by the control circuit An alarm device configured to include an alarm generating means that is operated based on the above is attached to the wrist with a belt.

  In addition, the device described in Patent Document 2 detects blood flow caused by blood flow in the shunt portion and obtains blood flow, thereby accurately detecting blood flow without misdiagnosis of noise around the patient, and blood It is an object of the present invention to provide a blood flow condition monitoring device in a shunt that can immediately notify a patient when the amount falls below a reference value.

  Therefore, a vibration detecting means for detecting the vibration of the shunt, an amplifying means for amplifying the signal detected by the vibration detecting means, and a frequency for selecting the frequency of the vibration component from the signal of the amplifying means Selection means, smoothing means for converting to a DC voltage proportional to the AC voltage of the frequency selection means, initial value storage means for storing a voltage proportional to the blood flow during normal operation, and the initial value storage And determining means for outputting an alarm to the patient when the current blood flow rate is lower than the initial value stored in the means.

  In these techniques, vibration detection means is installed on an arm that is a shunt portion of a patient to acquire vibration. In this case, in order to manage blood pressure and pulse, the patient must keep wearing the device on the arm, which causes inconvenience.

  Therefore, there is a dialysis device or a device that provides tube deformation measurement means in a disposable extracorporeal circuit, and can manage blood pressure and pulse without causing discomfort of continuous wearing to the patient, thereby reducing the burden on the medical staff. It is disclosed in Japanese Patent Application Laid-Open No. 2002-186590 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2002-186665 (Patent Document 4).

  The device described in Patent Document 3 describes a system that continuously measures the pulse of a patient in a dialysis circuit.

  That is, the computer for monitoring processing calculates the wave number per unit acquisition time from the deformation signal obtained by measuring the deformation amount of the tube in the middle of the tube that sends blood to the dialyzer, and obtains the patient's pulse from the calculated wave number. I am doing so.

  Moreover, the apparatus described in Patent Document 4 describes a system that continuously monitors the systolic blood pressure of a dialysis patient while preventing blood contamination.

  That is, the permissible fluctuation range of the systolic blood pressure predetermined for the patient is set in the monitoring processing computer. The monitoring processing computer calculates the maximum blood pressure from the deformation signal obtained by acquiring the deformation amount of the tube in the middle of the tube that sends blood to the dialyzer, and monitors whether the maximum blood pressure value is within the allowable fluctuation range, A warning signal is output on condition that the maximum blood pressure value during dialysis is outside the allowable fluctuation range.

In these documents, a movable lot for obtaining blood pressure is provided in a blood circuit, and an abnormality is detected by calculating the wave number based on the measured blood pressure waveform.
Japanese Patent No. 3083378 JP-A-10-52490 JP 2002-186590 A JP 2002-186665 A

  However, in the apparatus for monitoring the blood flow state described in Patent Document 1 or 2, an abnormality is detected after acquiring shunt sounds and detecting noises such as environmental sounds at frequencies other than the shunt sounds using a frequency filter. is doing. For this reason, the sound existing in the same frequency band as the shunt sound cannot be removed as noise, which may cause malfunction of the apparatus.

  Furthermore, as described above, it is necessary to keep the device on the arm for shunt sound management, which is inconvenient.

  On the other hand, in the system for acquiring the pulse by acquiring the deformation amount of the tube described in Patent Document 3 or 4, the abnormality is detected by mainly acquiring the blood pressure in the blood circuit. In this case, when pressure such as body movement or bending is applied to the tube, it is also detected, which may cause erroneous detection. In order to avoid this as much as possible, pulse / blood pressure acquisition means is installed only in the arterial blood circuit.

In view of the above problems, an object of the present invention is to provide a shunt sound acquisition means for acquiring a shunt sound in a blood circuit, and to obtain a sound pressure sum by performing a Fourier transform on the converted electric signal to derive a sound pressure sum. An object of the present invention is to provide a pulse measuring device using a shunt sound for acquiring a pulse .

The present invention relates to a pulse measuring device using a shunt sound, and the above object of the present invention is to provide a shunt sound acquisition means attached to an extracorporeal circulation blood circuit for acquiring a shunt sound, and the extracorporeal circulation resulting from the shunt sound. A shunt sound receiving means for receiving the vibration of the blood circuit as an electric signal, a frequency analyzing means for performing a Fourier transform on the electric signal, a frequency filter for passing the Fourier transformed frequency component, and a frequency band passing through the frequency filter. The shunt sound is achieved by providing a sound pressure sum calculating means for calculating the sum of sound pressures and a pulse detecting means for detecting a pulse as one pulse when the sound pressure sum of the frequency band exceeds a set value. Storage means for measuring and storing a basic pulse rate from the shunt sound acquired at a predetermined time from the start of acquisition, and a pulse measured thereafter Comparing the difference detecting means for obtaining a difference, said difference with a predetermined value, by further providing an abnormality means for informing the pulse abnormality when the difference becomes the predetermined value or more, it is more effectively achieved .

  According to the shunt sound acquisition method, the pulse measurement method using the shunt sound and the apparatus according to the present invention, the pulse can be continuously acquired non-invasively during the treatment for the patient, so that it is free from the trouble of wearing the apparatus. There are advantages.

  Furthermore, it is possible to detect a pulse by acquiring a shunt sound only in the venous blood circuit.

  Since the device does not require any special device other than the sensor and the acquisition device, these can be added to the conventional device at low cost. Moreover, it is not necessary to make any changes to the blood circuit itself.

  In addition, even when a noise frequency that cannot detect a normal pulse with one type of acquisition method is entered, the method and apparatus are more flexible than in the past because the state of the shunt is grasped by another type of acquisition method. Can be provided.

  The present invention includes a shunt sound acquisition means for acquiring a shunt sound in a blood circuit, and uses a shunt sound to acquire a more accurate pulse by deriving a sound pressure sum from the detected value of the converted electric signal. A pulse measuring method and apparatus are provided. For this reason, a shunt sound is acquired and converted into an electrical signal in the blood circuit of the extracorporeal blood treatment apparatus, and the noise frequency of this electrical signal is removed, and the sum of sound pressures is derived and compared at regular intervals, and the set value A pulse is detected with a sum of sound pressures exceeding 1 as one pulse.

  Hereinafter, in this embodiment, extracorporeal blood treatment is illustrated as an example of hemodialysis, and the present invention will be described.

  FIG. 1 is an example of a shunt created during hemodialysis and an inserted cannula.

  During hemodialysis, in order to obtain an extracorporeal blood volume of 200 [ml / min], dialysis patients usually create a shunt that secures a blood flow of about 500 to 700 [ml / min] by anastomosing the vein and artery of the wrist. is doing. In the shunt, it is known that a shunt sound (vibration) is generated by a turbulent flow generated by merging two flows, and auscultation and palpation are performed as part of daily shunt management.

  The arterial cannula 1 and the venous cannula 7 are inserted into blood vessels as shown in FIG. 1, and blood sampling is performed.

  FIG. 2 is a configuration diagram of a hemodialysis apparatus according to the present invention.

  The hemodialysis apparatus includes an arterial cannula 1 that obtains extracorporeal blood flow, an arterial blood tube 2 that secures arterial blood flow, and a blood pump that operates to obtain extracorporeal blood to the hemodialysis apparatus during hemodialysis. 3, a dialyzer (dialyzer) 4 for hemodialysis, a venous drip chamber 5, a venous blood tube 6 through which blood purified by the dialyzer 4 flows, a venous cannula 7 for returning extracorporeal circulation to the body, a patient A shunt sound acquisition means 8 for acquiring the shunt sound of the patient, a shunt sound analysis device 9 for analyzing the shunt sound acquired from the patient, and an alarm device 10 for outputting an alarm when an abnormality is detected from the analyzed shunt sound. ing.

  The blood is guided from the arterial cannula 1 to the dialyzer 4 through the arterial blood tube 2. A blood pump 3 is installed in the arterial blood tube 2 to circulate blood taken out from the arterial cannula 1 to an extracorporeal circuit. The dialyzer 4 purifies the blood by removing unnecessary substances and moisture by the principle of diffusion and ultrafiltration, and the purified blood is returned to the patient's body through the venous blood tube 6 from the venous cannula 7. The venous blood tube 6 is provided with a venous drip chamber 5 for removing bubbles.

  The arterial blood circuit described in the present embodiment refers to the blood circulation path from the arterial cannula 1 to the blood introduction part of the dialyzer 4, and the venous blood circuit refers to the blood outlet part of the dialyzer 4 to the venous cannula. Refers to blood circulation up to 7.

  The shunt sound acquisition means 8 is provided in the arterial blood tube 2 and / or the venous blood tube 6 as shown in this figure in order to avoid the inconvenience of wearing it on the body. Normally, it is desirable to install both the arterial blood tube 2 and the venous blood tube 6.

  In order to perform more accurate shunt sound acquisition, the arterial shunt sound acquisition means 8a is provided between the arterial cannula 1 and the blood pump 3, and the venous shunt sound acquisition means 8b is provided from the venous drip chamber 5 to the venous cannula 7. It is desirable to install between.

  Further, the shunt sound acquisition means 8 converts at least one of sound, vibration of the blood circuit, and blood pressure into an electric signal, for example. As the most preferred example, it is desirable to acquire all three types and convert them into electrical signals.

  In addition, the shunt sound acquisition means 8 provided in the vein side blood tube 6 acquires the shunt sound transmitted from the vein side cannula 7 punctured by the shunt. As described above, the shunt sound is a blood flow sound in the anastomosis part and a blood vessel vibration sound due to the blood flow. When undergoing hemodialysis, the arterial cannula 1 and the venous cannula 7 puncture the same shunt blood vessel, so that the same sound can be heard through each cannula. Since the venous cannula 7 is separated from the anastomosis portion, the magnitude of the shunt sound that can be acquired is attenuated (see FIG. 1), but the same shunt sound as the arterial shunt sound acquisition means 8a and the venous shunt sound acquisition means 8b is acquired. It will be.

  FIG. 3 is a configuration diagram of the shunt sound analyzer.

  The acquired shunt sound is input to the shunt sound analyzer 9 as an electrical signal.

  The shunt sound analyzing device 9 includes a shunt sound receiving unit 91 that receives the input of the electric signal, a frequency analyzing unit 92 that performs frequency analysis every predetermined time and converts the electric signal into a frequency-sound pressure system, and a shunt sound A frequency filter 93 that extracts only a frequency band in which a frequency component is present, a sound pressure sum calculation means 94 that acquires an integral value of a specific frequency range in an electric signal converted into a frequency-sound pressure system, and time-series processing. Connected to a pulse detecting means 95 for detecting an integrated value equal to or greater than a predetermined set value from the electrical signal as a pulse of one pulse, and an alarm device for determining whether or not the detected pulse rate is a normal value and issuing an alarm. The pulse abnormality detecting means 96, the basic pulse rate setting means 97 for manually setting the basic pulse rate, and the display device 99 for displaying the pulse rate and the like on the shunt sound analyzer 9 are configured. To have.

  In addition, when a shunt sound is acquired by two or more types of acquisition methods, it is desirable to perform analysis for each acquired electrical signal. That is, analysis and pulse detection using the means of 92 to 96 are performed independently for each acquired signal. This will be described later.

  As the pulse rate set by the basic pulse rate setting means 97, for example, a normal human pulse rate of 60 times / minute is set.

  The operation of this apparatus in such a configuration will be described with reference to the flowchart shown in FIG.

  When hemodialysis is performed, the shunt sound acquisition means 8 converts the acquired shunt sound into an electrical signal and transmits it to the analyzer 9 (step S101). Examples of the acquisition of the shunt sound include a microphone, a blood pressure acquisition device that acquires blood pressure of the blood circuit, and a vibration acquisition device that acquires vibration of the blood circuit. An example of the obtained waveform is shown in FIG.

  Further, since there are individual differences in shunt sound and pulse for each patient, it is desirable to acquire the shunt sound with a certain time as the sampling time and compare the pulse that can be derived from this as the basic pulse rate of this patient. This will be described when the operation of the pulse abnormality detecting means 96 is described.

  The acquired electrical signal of the shunt sound (hereinafter simply referred to as an electrical signal) is sent to the analyzer 9, and the shunt sound receiving means 91 receives it (step S102). The acquired electrical signal is transmitted to the frequency analysis means 92 for pulse detection.

  As described above, if three types of microphone, blood pressure acquisition device, and vibration acquisition device are simultaneously used for acquisition as the shunt sound acquisition means 8 (including any other acquisition device), each device It is desirable to prepare a frequency analysis means for performing frequency analysis for each electrical signal acquired by the above. Here, for the sake of simplicity, only the shunt sound acquired by the microphone will be described, but the same applies to the processing of other types of electrical signals.

  The frequency analysis unit 92 performs frequency analysis for a predetermined time range on the input electric signal. There may be overlap in the time interval for performing frequency analysis. This frequency analysis is continuously performed, and the result is shown by the frequency-sound pressure system in FIG. 6 (step S103). In FIG. 5, this predetermined time range is represented by T1, T2, T3..., And the result of frequency analysis is represented by T1, T2, T3 in FIG. The time of T1, T2, T3... May be arbitrary, but if it is too large, the next pulse will be included, so the length of one pulse can be divided into several to analyze the frequency. Is preferred.

  As long as this frequency analysis is an analysis that can be converted into a frequency-sound pressure sum system such as Fourier transform and maximum entropy (MEM) method, any analysis method may be used.

  The shunt sound usually has a frequency band of 100 Hz to 500 Hz. For this reason, other frequency bands can be processed as noise frequencies. In order to remove the noise frequency, a noise filter is used to remove the noise frequency (step S104). In addition, since 100Hz-500Hz is a normal value and there are individual differences, in order to respond | correspond more flexibly, it is preferable to have a play as 50Hz-1000Hz. Or it can also set using the shunt sound acquired at the time of the basic pulse rate extraction mentioned above.

  Next, the sound pressure sum calculation means 94 calculates the sound pressure sum existing in the frequency band after passing through the frequency filter (step S105). This sound pressure sum is calculated by integrating a decibel curve obtained by frequency analysis of each predetermined time range. The obtained sound pressure sums are juxtaposed as a time series.

  In addition, since the heart functions as a pump, blood flow becomes maximum at the same time as the pulse is depressed, and the sound that can be heard as a shunt sound also has the maximum sound pressure. Using this characteristic, a set value is set in advance, and the pulse detecting means 95 detects a portion having a sound pressure sum exceeding the set value as one pulse, that is, one pulse (step S106). There are individual differences in the set value, and it is desirable to set using the shunt sound obtained by extracting the basic pulse rate described above. FIG. 7 shows the result of leaving the sound pressure sum exceeding the set value.

  As a more preferred embodiment, it is well known that the sound pressure of the shunt sound decreases after a single pulse. By using this characteristic, the frequency analysis period is continuously observed, and the set value is set. If a peak exceeding the peak is detected as one pulse, a more accurate pulse can be obtained.

  Information about the pulse is reported by being displayed on the display means 98 of the shunt sound analyzer. As for the detected pulse, the pulse rate of the same time as the time when the basic pulse rate was taken in the pulse abnormality detecting means 96 described later is counted, but the display means 98 displays this pulse rate, the pulse rate before that, Other information about the pulse can be displayed at any time.

  The measured pulse is compared with the basic pulse rate by the pulse abnormality detection means 96, and it is detected whether or not there is an abnormality in the pulse (step S107).

  As described above, when a plurality of electrical signals are obtained by a plurality of acquisition means, pulse measurement is performed independently for each signal. However, here, it is assumed that three types of electrical signals are obtained by three types of acquisition means. To do.

  The pulse of each of the three signals is detected according to the above-described flowchart. The obtained pulse information is a time-sound pressure sum two-dimensional graph as shown in FIG. 3, and information from which peaks are extracted is transmitted from the pulse detection means 95 to the pulse abnormality detection means 96.

  In the pulse abnormality detection means 96, the above three types of signals are input and compared with the shunt sound obtained by extracting the basic pulse rate and the pulse rate analyzed by the shunt sound. As a result, an abnormality is detected.

  The shunt sound from which the basic pulse rate was extracted was acquired as a sample for a certain time after the start of blood sampling, and the above analysis was performed to acquire the pulse rate, the interval between pulses, the size of the sound pressure sum, etc. Is. By storing this as a normal shunt sound in the pulse abnormality detecting means 96 together with the pulse rate, the pulse abnormality detecting means 96 effectively detects the pulse abnormality.

  Depending on the noise situation, there are situations where one or two of the three types of signals detect an abnormality and the other one does not detect an abnormality. In this case, whether or not to derive a signal as a pulse abnormality can be changed by setting. In the most careful case, when even one abnormality is detected, a signal is transmitted to the alarm device 10 (step S108), and the alarm device 10 is activated to report it.

  On the other hand, the basic pulse rate can be manually set using the basic pulse rate setting means 97 without first detecting the basic pulse rate, and this pulse rate is compared with the detected pulse rate for determination. It is also possible to do.

  Thereafter, when the pulse acquisition is continued, the acquisition / analysis of the shunt sound is continued, and when it is not continued, the process ends (step S109).

It is an example of the shunt created at the time of hemodialysis which concerns on this invention, and the inserted cannula. It is a block diagram which shows an example of the hemodialysis apparatus which concerns on this invention. It is a block diagram which shows the internal means structural example of the shunt sound analyzer which concerns on this invention. It is a flowchart which shows the operation | movement which concerns on this invention. It is a wave form diagram which shows an example of the electric signal of the shunt sound which concerns on this invention. It is a figure which shows an example of the frequency-sound pressure system which concerns on this invention. It is the figure which took out the sound pressure sum exceeding the setting value based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Arterial side cannula 2 Arterial side blood tube 3 Blood pump 4 Dializer 5 Vein side drip chamber 6 Vein side blood tube 7 Venous side cannula 8 Shunt sound acquisition means 9 Shunt sound analysis device 10 Alarm device 91 Shunt sound reception means 92 Frequency analysis Means 93 Frequency filter 94 Sound pressure sum calculation means 95 Pulse detection filter 96 Pulse abnormality detection means 97 Basic pulse rate setting means 98 Display means

Claims (2)

A shunt sound acquisition means attached to an extracorporeal circulation blood circuit for acquiring a shunt sound, a shunt sound reception means for receiving vibration of the extracorporeal circulation blood circuit caused by the shunt sound as an electric signal, and the electric signal Frequency analysis means for performing Fourier transform, a frequency filter for passing the Fourier-transformed frequency component, sound pressure sum calculating means for calculating the sound pressure sum of the frequency band that has passed through the frequency filter, and sound pressure of the frequency band A pulse measuring device using a shunt sound, comprising: a pulse detecting means for detecting a pulse as one pulse when the sum exceeds a set value. Storage means for measuring and storing a basic pulse rate from the shunt sound acquired at a predetermined time from the start of acquisition of the shunt sound, difference detection means for obtaining a difference between the measured pulse and a difference between the storage means and the predetermined difference The pulse measuring device using a shunt sound according to claim 1 , further comprising: an abnormality means for notifying a pulse abnormality when the difference is equal to or greater than the predetermined value.

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