JPH1052490A - Monitoring device for flowing blood on shunt forming site - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monitoring device for flowing blood on shunt forming site that is possible to accurately detect blood flow quantity without mis- detecting on noise around the patient and to quickly notify a patient of drop down in flowing blood quantity from a certain level by measuring flowing blood quantity through detecting vibration made by flowing blood on a shunt forming site. SOLUTION: This device is composed of a vibration detector 1 to detect vibration made by flowing blood on a shunt forming site, an amplifier 2 to amplify the signals from the vibration detector 1, a frequency selector 3 to select certain frequencies among from signals sent from the amplifier 2, a smoother 4 to convert an AC voltage from the frequency selector 3 into a proportional DC voltage, a primary memory 5 to store information of voltage proportional to flowing blood quantity at the normal period and a judgement finder 6 to output a warning to a patient when the present flowing blood quantity becomes lower than the primary figures stored in the initial value memory 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blood dialysis or filtration therapy using an artificial organ, which monitors a blood circulating state at a shunt forming site as a site for extracting blood from a living body. The present invention relates to a blood flow monitoring device at a shunt formation site for early detection of thrombus generation in a blood vessel.

[0002]

2. Description of the Related Art Conventionally, blood purification therapy using an artificial organ capable of artificially exerting renal and hepatic functions has been generally adopted, and a remarkable effect has been recognized. For example, hemodialysis or filtration therapy using artificial organs, which is applied to patients with renal failure, is a typical example.
When performing blood purification using an artificial organ, an operation called a shunt is performed on an arm, a thigh, or the like in order to secure a venous blood flow required for extracorporeal circulation. When blood is taken out of the body, a needle is inserted into the shunt part (arterialized vein part), and the blood is drawn with a blood pump at a blood flow rate of about 200 to 800 ml / min.

[0003] However, in the shunt forming portion, there is a problem that blood is easily coagulated and a thrombus often occurs. If a thrombus occurs, and if it is found early, it can be removed by administering a blood coagulation inhibitor or thrombolytic agent and dissolving the resulting thrombus. Over time, it becomes difficult to dissolve it, and the thrombus must be removed by surgery. In addition, if this operation is not performed within a few hours, the blood vessel cannot be used, which may cause a situation in which a shunt must be formed again.

[0004] For this reason, conventionally, a patient listens to a shunt sound daily with a stethoscope at the time of getting up and going to bed to check the blood circulation state. BACKGROUND ART Injection, infusion, and the like are used to receive an anticoagulant such as heparin, a thrombolytic agent such as urokinase and activator, and to undergo surgery depending on the situation.

[0005] The inventor of the present invention disclosed in Japanese Patent Application Laid-Open No. H5-111547 (Title of Invention:
A monitoring device for monitoring the state of blood flow at the shunt formation site) was invented. The apparatus includes a microphone for detecting a shunt sound, which is a flow sound of blood in the shunt forming section, and a detection value and a lower limit value set in advance in the microphone that change according to a decrease in the shunt sound due to deterioration of the blood flow state. , A control circuit that issues a signal when the detected value falls below a set value, and an alarm generating means that is activated based on the signal issued by the control circuit.

[0006] This device continuously monitors the blood flow state of the shunt portion by detecting the shunt sound, which is the flow sound of blood in the shunt forming portion, with a microphone, and a thrombus is formed in the shunt portion to form a blood clot. When the flow rate decreases, the detection value detected by the microphone becomes smaller than a preset lower limit value, and an alarm is automatically issued. However, since the shunt sound, which is the flow sound of blood in the shunt forming section, is detected by the microphone, in addition to the shunt sound, noise around the patient (eg, car noise, television sound, radio sound, human voice, etc.) Noise) was also detected at the same time, and accurate detection could not be performed.

Conventionally, during hemodialysis or filtration therapy using an artificial organ, a patient may become unconscious due to a decrease in blood pressure and need to be treated, and it has been necessary to detect a decrease in blood pressure at an early stage.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and detects a vibration caused by a blood flow in a shunt forming section and measures a blood flow to thereby reduce noise around a patient. It is an object of the present invention to provide a blood flow state monitoring device at a shunt formation site capable of accurately detecting a blood flow without erroneously detecting the blood flow and notifying a patient of a decrease in the blood flow by a certain amount or more as soon as possible. A second object of the present invention is to detect a decrease in blood pressure of a patient during hemodialysis or filtration therapy at an early stage. The purpose of the present invention is to detect a decrease in blood pressure at an early stage by using a blood flow monitoring device.

[0009]

[Means for Solving the Problem] The first one shown in FIG.
According to the invention, a vibration detecting means 1 for detecting a vibration caused by a blood flow in a shunt forming section, an amplifying means 2 for amplifying a signal detected by the vibration detecting means 1, and an amplifying means 2 Frequency selecting means 3 for selecting the frequency of the vibration component generated from the shunt forming portion from the signal, smoothing means 4 for converting the frequency selecting means 3 into a DC voltage proportional to the AC voltage, and a normal blood flow Initial value storage means 5 for storing a DC voltage (initial value: B) proportional to the current value, and the current blood flow rate: A is more constant than the initial value: B stored in the initial value storage means 5 This is a monitoring device for monitoring the state of blood flow at the shunt formation site, comprising a determination means 6 for outputting an alarm to the patient when the following occurs.

A second invention shown in FIG. 2 includes a judgment value setting means 7 which can externally set a judgment degree (judgment value) of a blood flow rate, the blood at a shunt formation site according to claim 1. It is a monitoring device in a flowing state. The third invention is
The first or second aspect of the present invention focuses on the correlation between blood flow and blood pressure, and uses the apparatus for monitoring the state of blood flow at a shunt formation site of the present invention in order to detect a decrease in blood pressure at an early stage. It is to be.

[0011]

According to the structure of the first aspect of the present invention, the vibration generated at the anastomotic portion of the shunt is converted into an electric signal by the vibration detecting means 1 with respect to the arm in which the inner shunt is formed as in the prior art. The converted signal is amplified by the amplification means 2, and only the frequency components corresponding to the vibration generated at the anastomotic portion of the shunt are selected from the amplified signals by the frequency selection means 3, and the level of the selected frequency component is changed. Smoothing means 4
The initial value which is the output voltage of the smoothing means 4 when the shunt is functioning normally while rectifying and smoothing at:
A is stored in the initial value storage means 5, and when the output voltage of the smoothing means 4 during monitoring is lower than the voltage stored in the initial value storage means 5: B, the determination means 6 An alarm is output to the patient, and the patient can detect a decrease in blood flow at an early stage.

According to the configuration of the second invention, the first invention is provided with the judgment value setting means 7 which can externally set a judgment value indicating the degree of decrease in blood flow, and the degree of decrease due to individual differences among patients. Can be set freely, and it is possible to accurately detect a decrease in blood flow suited to the patient. The third invention focuses on the fact that there is a correlation between blood flow and blood pressure in the first or second invention, and uses the blood flow monitoring device at the shunt formation site of the present invention to reduce blood pressure. Can be found early.

[0013]

EXAMPLES Examples of the present invention will be described below in order to clarify the present invention more specifically. First Embodiment A first embodiment of the present invention will be described with reference to the drawings.

In FIG. 3, reference numeral 10 designates an inner shunt which is attached with a bandage or an adhesive bandage (not shown) to be attached to an arm formed as in the prior art (not shown) to detect a vibration generated at an anastomotic portion of the shunt. This is a sensor made of a flexible piezoelectric element. The piezoelectric element used here is a thin film made of a polymer piezoelectric material such as polyvinylidene fluoride (PVDF) or a composite material of PVDF and PZT, and a flexible electrode film is attached to both surfaces. A charge amplifier (charge amplifier) 11 amplifies the output of the sensor 10 without being affected by the line capacitance of a cable for extracting a signal from the sensor.
It is. Reference numeral 20 denotes an amplifier (amplifier) capable of changing the gain in accordance with the magnitude of the output signal of each patient. Reference numeral 30 denotes a band-pass filter that selects only a vibration component generated by the flow of blood in the shunt forming section from signals detected by the sensor 10 and amplified by the charge amplifier 11 and the amplifier 20. The vibration component generated by the blood flow in the shunt forming section is 100 to 800H.
The frequency band of the band-pass filter is selected to be 150 to 500 Hz in consideration of noise, hum, and the like, which are found from the experimental data of the patient to be between z. 40 is
A rectifying / smoothing circuit for converting the AC signal selected by the bandpass filter 30 into a DC signal.

Reference numeral 60 denotes a CPU, a ROM, a RAM, a clock generation circuit (including a clock), an interval timer,
Clock timer, event counter, various internal buses (not shown), AD converter (ADC) 60a, input / output device (I / O) 60b, and LCD controller 60c
ΜPD7 with a one-chip microcomputer consisting of
8P064 (manufactured by NEC) or the like can be used. 61 corresponds to FIG.
Is a mode switch for selecting the mode shown in FIG.
Reference numeral 62 denotes a set switch for performing input from each mode to the child mode and selection of a numerical value or a setting mode. 63
Is an alarm device including a buzzer, an indicator light, and the like for notifying a patient of a decrease in blood flow. 64 is the degree of decrease in blood flow,
It is a digital switch including a thumbwheel switch, a DIP switch, and the like for inputting a numerical value such as a measurement interval. Reference numeral 65 denotes a liquid crystal display (LCD) that displays a mode, a blood flow amount, a measurement time, and the like. Reference numeral 70 denotes a determination value setting circuit that generates a DC voltage by a variable resistor in order to set the degree of decrease in blood flow.

The configuration of the present device comprises a charge amplifier 11 and an amplifier 20 for amplifying an output signal of the sensor 10;
A band-pass filter 3 for selecting only the vibration component of the shunt forming part from the detection signal amplified by the amplifier 20 or the like;
0, a rectifying / smoothing circuit 40 for converting the output signal of the band-pass filter 30 into a DC signal,
0, 1-chip microcomputer 60, mode switch 61, select switch 61, alarm device 63
, A digital switch 64, an LCD 65, and a power supply (not shown) composed of a nickel-metal hydride battery, a nickel-cadmium battery or the like for supplying a voltage to each circuit. Rectification
The outputs of the smoothing circuit 40 and the determination value setting circuit 70 are output from an ADC 60 built in the one-chip microcomputer 60.
a. The mode switch 61, the select switch 61, and the alarm device 63 are connected to an I / O 60b built in the one-chip microcomputer 60, respectively. The LCD 65 is connected to an LCD controller 60c built in the one-chip microcomputer 60.

The operation of the first embodiment of the present invention will be described below with reference to FIGS. When the apparatus is turned on, the apparatus is turned on in step 10 of FIG.
It is described as S10. The other steps are the same. ) And S2
Proceed to initialization of 0. At S20, CPU, RAM, I /
Initialize O60b and LCD controller 60c, etc.
The mode is set to the measurement mode (continuous measurement) of mode 0, and the initial value of the blood flow is set to 0, and the process proceeds to the measurement / determination serve routine of S30. In S30 (see FIG. 7), the blood flow during measurement is compared with an initial value (details will be described later),
Proceed to S40. In S40, if the measurement mode is continuous measurement, the process proceeds to the measurement / determination serve routine of S30, and if the measurement mode is other than continuous measurement, the process proceeds to S50. In S50, the one-chip microcomputer 60 itself executes a HALT instruction suitable for performing an intermittent operation such as a clock operation, the one-chip microcomputer 60 operates in the low power consumption mode, and the clock of the one-chip microcomputer 60 operates. The program is paused until the application timer executes the clock interrupt. Immediately after power-on, the program loops S30 and S40 unless a mode operation is performed.

When the mode switch 61 is operated, the mode switch interrupt shown in FIG. 5 is generated, and the flow proceeds to the mode setting subroutine of S60. When the mode setting is completed, the flow proceeds to S61. In S61, a return instruction (RET) is executed to return from the subroutine to the program executed before the interruption.

The mode setting routine will be described below with reference to FIG. 8 schematically showing the operation of the mode setting routine S60. During continuous measurement of mode 0 or HAL
If the mode switch 61 is operated during T, a mode switch interrupt is generated, and the mode advances to mode 1 where the previously set initial value: B is set to the LCD 65 via the LCD controller 60c.
To be displayed. In mode 1, when the mode switch 61 is operated, the operation proceeds to mode 2, and when the set switch 62 is operated, the operation proceeds to mode 11. In the mode 11, the smoothed blood flow: A described later is transmitted to the LCD 65 via the LCD controller 60c of the one-chip microcomputer 60.
Is displayed, and the gain of the amplifier 20 is changed so that the display on the LCD 65 is adjusted to a value of 60 to 80. Then, when the set switch 62 is operated, the blood flow rate: A is set to the initial value: B, and the one-chip microcomputer 60 is set. And the process proceeds to mode 2. In addition, ADC
The voltage input to the 60a is displayed by processing the original data to a numerical value of 0 to 99, with the full scale of the ADC 60a being 99.

In mode 2, when the mode switch 61 is operated, the operation proceeds to mode 3, and when the set switch 62 is operated, the operation proceeds to mode 21. When the mode switch 61 is operated in the mode 21, the process proceeds to the mode 22. In mode 21,
Judgment value previously stored in the program: 50%
50 is displayed on the LCD 65 via the CD controller 60c, and it is determined that the normal determination value is sufficient.
Is operated, the RA of the one-chip microcomputer 60 is
C = 0.5 is stored in the M determination value area, and the process proceeds to mode 3. In the mode 22, the output of the judgment value setting circuit 70 is set to AD
C60a periodically converts the digital value (every 1 msec) to a digital value, displays the digital value on the LCD 65 via the LCD controller 60c, and changes the judgment value setting circuit 70 while looking at the numerical value of the LCD 65 to obtain the optimum judgment value: C. When adjustment is completed and the set switch 62 is operated, C = (displayed value ÷ 10) is stored in the determination value area of the RAM of the one-chip microcomputer 60, and the mode proceeds to mode 3.

Judgment value: 50% selected as a fixed value of C
Can be applied to patients who have developed arterialized veins sufficiently after shunting surgery, patients whose doctors have determined that blood flow is normal, and the like. The input from the judgment value setting circuit 70 can be 0 to 99%, and when monitoring the patient from the middle, the machine is reset in the middle, the judgment value set first is erased, and the judgment value: C is set again. This is used when the blood flow is particularly larger than that of other normal patients, and in most cases, the judgment value is used at 30 to 70%.

In mode 3, when the mode switch 61 is operated, the operation proceeds to mode 0, and when the set switch 62 is operated, the operation proceeds to mode 31. In the mode 31, when the mode switch 61 is operated, the operation proceeds to the mode 32. When the continuous measurement is selected and the set switch 62 is operated, the operation proceeds to the mode 0.
In the mode 32, when the mode switch 61 is operated, the process proceeds to the mode 33. When the interval measurement for 15 minutes is selected and the set switch 62 is operated, the process proceeds to the mode 0. In the mode 33, when the mode switch 61 is operated, the mode advances to the mode 34, in which the set switch 6 for selecting the interval measurement for 30 minutes is set.
When 2 is operated, the mode proceeds to mode 0. In the mode 34, when the mode switch 61 is operated, the operation proceeds to the mode 31. When the set switch 62 is operated to select the 60-minute interval measurement, the operation proceeds to the mode 0.

In the measurement interval of mode 3, continuous measurement, 15
There are minute interval measurement, 30 minute interval measurement, and 60 minute interval measurement. In the continuous measurement, when the initial value of the blood flow of the patient: B and the judgment value: C are set, the patient whose blood flow is reduced to nearly 50% of the initial value: B, when the patient's tendency is first observed, and when dialysis is performed It is effective to use it for monitoring blood pressure of patients whose blood pressure falls during the period. In the 15-minute interval measurement, the patient's blood flow is initially set to B while the patient's blood flow is slightly lower than the initial B:
It is effective to use for monitoring the blood pressure during dialysis of dialysis patients when it is reduced to 60% or less. It is effective to use the 30-minute interval measurement to investigate the degree of change in blood flow of a patient during a day while the patient with normal blood flow is asleep. 60
It is effective to use the minute interval measurement in cases other than the above.

The one-chip microcomputer 60 has an HA
During the LT, if the timer interrupt for the 15-minute, 30-minute, or 60-minute interval set in mode 3 is generated inside the one-chip microcomputer 60, the process proceeds to the measurement / determination serve routine of S30. In the measurement / determination serve routine of S30 (see FIG. 7), the blood flow during measurement is compared with an initial value (details will be described later), and the process proceeds to S40.

Referring to FIG. 7, the measurement / judgment serve routine will be described in detail below. At the start of S31, the measurement / determination serve routine is started, and the flow proceeds to blood flow input of S32. In S32, the vibration generated by the blood flow in the anastomotic portion of the shunt is detected by the sensor 10, amplified, and an AC signal obtained by frequency selection is converted into a DC voltage by the rectification / smoothing circuit 40, and the voltage is converted to a DC voltage. The ADC 60a periodically (every 1 msec) converts the digital value into a digital value, and determines the judgment value data: A
n is stored in the blood flow data area of the RAM of the one-chip microcomputer 60. Further, the output voltage of the determination value setting circuit 70 is converted into a digital value periodically (every 1 msec) by the ADC 60a, and the determination value data: C
n is stored in the determination value data area of the RAM of the one-chip microcomputer 60, and the process proceeds to S33. In S33, the blood flow data: An and the determination value data: C
n, a plurality of (10-30) data are subjected to smoothing to remove noise by a moving average method, a weighted average method, etc., and blood flow data: A and determination value data: C are obtained, respectively, and S34 Proceed to.

In S34, if the blood flow data: A is larger than the product of the initial value of blood flow: B and the determination value: C, the blood flow is determined to be in the normal range, and the process proceeds to S37, where this subroutine is terminated. The blood flow data: A is the initial value of the blood flow: B
If the determination value is smaller than the product of C, it is determined that the blood flow has decreased, and the process proceeds to S35. In S35, when the blood flow rate has continuously decreased for a certain period of time or more (for example, between several seconds to several minutes) (when the blood flow has continuously passed through S35), the process proceeds to S36. If the blood flow does not continuously decrease for a certain period of time or longer, the blood flow is determined to be in the normal range, the process proceeds to S37, and the present subroutine is terminated. In S36, the alarm is output to the alarm device 63 via the I / O 60b of the one-chip microcomputer 60, and the alarm device notifies the patient of a decrease in blood flow by sound or light, and blinks the display on the LCD 65, and then proceeds to S3.
Then, the subroutine ends. In addition, the patient's arm is bent or a load is applied to the shunt site, and the blood flow is temporarily reduced and an alarm is output.The patient notices and extends the patient's arm or removes the load applied to the shunt site, and the blood flow is normal. If you return, the alarm will be released.

The effect of the present embodiment is that the blood flow in the shunt forming section is detected and the blood flow is measured to detect the blood flow accurately without erroneously detecting noise around the patient. Not only can the patient be alerted to a decrease in blood flow more than a certain amount early, but also by using time interval measurement, battery consumption can be suppressed and long-term measurement can be performed.

A second embodiment of the present invention will be described with reference to FIGS. The second embodiment is a modification of the first embodiment and describes the differences, and the same portions are denoted by the same reference numerals and description thereof will be omitted. Instead of the bandpass filter 30 and the rectifying / smoothing circuit 40 used in the first embodiment,
In the second embodiment, the filtering process of S38 and the averaging process of S39 in FIG. 10 are replaced by software processes.

In the present embodiment, the vibration caused by the blood flow flowing through the shunt anastomosis is detected by the sensor 10 and
After the output of 0 is amplified by the charge amplifier 11, it is amplified by the amplifier 20 capable of changing the gain according to the magnitude of the output signal of each patient, and the AC signal is sent to the ADC 60 a of the one-chip microcomputer 60. Is entered directly as In the AC signal, a half point (middle scale) of the full scale of the ADC 60a is the zero point of the AC signal. 9 is the same as that of the first embodiment shown in FIG.
Therefore, the description is omitted.

FIG. 10 is different from FIG. 7 of the first embodiment in that a filtering process in S38 and an averaging process in S39 are added. In S38, using the blood flow data: A obtained by the smoothing in S33, a band-pass filter using a recursive digital filter has a pass bandwidth of 150 to 500 Hz, and after performing a filtering process, proceeds to S39. In S39, a half point (middle scale) of the full scale of the ADC 60a is set as the zero point of the AC signal, and averaging processing is performed by adding absolute values to obtain blood flow data.
Proceed to 4. Note that the other configuration in FIG. 10 is the same as that in FIG. 7 of the first embodiment, and a description thereof will be omitted.

The effect of the second embodiment is that power consumption is further reduced because the bandpass filter 30 and the rectifying / smoothing circuit 40 of the first embodiment are eliminated.

Normally, the vibration of the shunt forming portion can be detected satisfactorily with one sensor 10, but if necessary, a plurality of sensors may be provided around the shunt portion and around the shunt portion (where vibration does not propagate). It is also possible to more accurately detect the vibration of the shunt forming portion by removing noise and hum on the body surface.

[0033]

According to the present invention, by detecting the vibration caused by the blood flow in the shunt forming section and measuring the blood flow, the blood flow can be accurately detected without erroneous detection of the noise around the patient, and the blood flow can be maintained at a certain level or more. Can be notified to the patient early.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim of the first invention.

FIG. 2 is a diagram corresponding to claims of the second invention.

FIG. 3 is a block diagram of a first embodiment of the present invention.

FIG. 4 is a general (basic) flowchart.

FIG. 5 is a diagram showing a mode switch interruption.

FIG. 6 is a diagram showing a timer interrupt.

FIG. 7 shows a subroutine of measurement and determination.

FIG. 8 is a diagram schematically showing a mode setting routine.

FIG. 9 is a block diagram of a first embodiment of the present invention.

FIG. 10 is a diagram showing a modified example of a measurement / determination subroutine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Vibration detection means 2 Amplification means 3
Frequency selection means 4 Smoothing means 5 Initial value storage means 6
Judgment means 7 Judgment value setting means

Claims (3)

[Claims] An amplifying means for amplifying a signal detected by said vibration detecting means; and amplifying means for amplifying a signal detected by said vibration detecting means. Frequency selecting means 3 for selecting the frequency of the vibration component generated from the shunt forming portion from the signals of the above, a smoothing means 4 for converting the frequency selecting means 3 into a DC voltage proportional to the AC voltage, Initial value storage means 5 for storing a DC voltage (initial value: B) proportional to the flow rate, and the current blood flow rate: A is larger than the initial value: B stored in the initial value storage means 5 A monitoring device for monitoring a blood flow state at a shunt formation site, comprising a determination unit 6 that outputs an alarm to a patient when the blood pressure falls below a certain level. 2. A monitoring device for monitoring a blood flow state in a shunt forming part according to claim 1, further comprising a judgment value setting means for externally setting a judgment value indicating a degree of decrease in blood flow. 3. The monitoring device for monitoring a blood flow state at a shunt formation site according to claim 1, wherein a monitoring of a decrease in blood pressure is performed based on a blood flow rate.