JPH0833706A - Clogging detecting method for body fluid external circulating device - Google Patents

Abstract

PURPOSE:To detect clogging on the discharge side of a roller pump with body fluids out of contact with the air by connecting an electromagnetic flowmeter to the discharge side of the roller pump, thereby detecting one of the amplitude, the peak value and change value of the pulsating body fluid quantity. CONSTITUTION:A first electromagnetic flowmeter 7a is connected to the discharge side of a first roller pump 1A for sucking a body fluid, for example, blood, and a first filter 3A for separating the blood into blood plasma and blood corpuscles is connected to the discharge side of the flowmeter. A second filter 3B for separating the blood plasma into a high molecular substance and a low molecular substance is connected to the discharge side of a second roller pump 1B for transferring the blood corpuscles filtered by the first filter 3A through a second electromagnetic flowmeter 7b. Further, a drip chamber 4 is disposed for mixing the low molecular substance separated by the second filter 3B with the blood corpuscles, and a supply container 10 is connected to the supply side of the chamber 4 through a fourth roller pump 1D. Thus, clogging of the respective filters 3A, 3B is detected by the respective electromagnetic flowmeters 7a, 7b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a method for detecting clogging of a body fluid extracorporeal circulation device which is a device for purifying blood.

[0002]

2. Description of the Related Art An apparatus for purifying blood, which is an extracorporeal circulation apparatus for circulating and purifying body fluid outside the body, is disclosed in, for example, Japanese Unexamined Patent Publication No. 57-57.
No. 22765. As shown in FIG. 12, this type of device includes first, second, and third roller pumps 1A, 1B, and 1C for forcibly circulating body fluid. Furthermore, this device is equipped with a first roller pump 1
Purification means 2 for purifying body fluid is connected to the discharge side of A. The purifying means 2 of this device includes a first filter 3A and a second filter 3B. The first filter 3A is
The blood is separated into plasma and blood cells, and the second filter 3B is used.
Separates blood cells into a high molecular weight substance and a low molecular weight substance that are pathogenic substances. Since this device may cause hemolysis when the first filter 3A is clogged, the speed of the second roller pump 1B connected to the plasma side of the first filter 3A is reduced and the device is connected to the first drip chamber 4A. The pressure detected by the pressure sensor 5A and the pressure sensor 5B connected to the plasma side of the first filter 3A is 50 to 60 mm.
It is necessary to adjust to Hg. Further, when the second filter 3B is clogged, the second roller pump 1
The detection pressure of the pressure sensor 5C of the second drip chamber 4B connected between B and the second filter 3B increases. In this state, the speed of the third roller pump 1C is increased, the second filter 3B is replaced, or the treatment is terminated.

Therefore, in the body fluid external circulation device shown in this figure, it is important to accurately detect clogging of the filter connected to the discharge side of the roller pump. To achieve this, conventionally, a drip chamber is connected to the discharge side of the roller pump. The drip chamber can detect whether body fluids are circulating normally. The drip chamber has a structure in which a predetermined amount of air is stored in the upper part and body fluid is discharged from the lower end. further,
A pressure sensor is connected to the upper part of the drip chamber to detect a clogging state on the discharge side of the drip chamber. The pressure sensor detects the pressure inside the drip chamber and detects clogging on the discharge side of the drip chamber. If the discharge side of the drip chamber becomes clogged,
This is because the pressure inside the drip chamber rises.

[0004]

The body fluid extracorporeal circulation device shown in FIG. 12 detects clogging of a filter by a pressure sensor connected to a drip chamber. However, since this method stores a predetermined amount of air in the drip chamber, it has a drawback that blood, which is a body fluid, comes into contact with air. The contact of blood with air causes blood clots to clot. To prevent this adverse effect, an anticoagulant is added to blood. However, recently, there is a tendency to reduce the amount of anticoagulant used or not to use it at all. This is because the use of anticoagulants may have a harmful effect on patients.
For example, the use of anticoagulants in patients with a hemorrhagic diathesis can induce fatal bleeding.

However, the method of detecting the degree of clogging on the discharge side by using the drip chamber cannot eliminate the disadvantage that blood comes into contact with air and coagulates unless an anticoagulant is used. In order to prevent this drawback, an improved method is described in Japanese Utility Model Publication No. 2-25408. In the method described in this publication, as shown in FIG. 13, the pressure on the discharge side of the roller pump 1 is detected by a double pipe type pressure detector 6. The double-tube type pressure detector 6 is a hard outer tube 6A.
Further, a flexible inner tube 6B is arranged in the outer tube 6A, and the outer tube 6A is connected to the pressure gauge. The pressure detector 6 having this structure includes an inner tube 6
When the pressure of the blood flowing into B increases, the inner tube 6B expands, increasing the pressure between the inner tube 6B and the outer tube 6A.
The pressure increase between the inner pipe 6B and the outer pipe 6A is detected by the pressure gauge 6C. This method allows blood to pass inside the inner tube 6B, so that it does not come into contact with air. For this reason,
There is a feature that the occurrence of thrombus can be effectively prevented without using an anticoagulant.

However, it is difficult for this method to accurately detect minute pressure changes in blood. Further, like the drip chamber 4, it is necessary to store a predetermined amount of blood in the inner tube 6B. This is because if the inner tube 6B is made thin, it is difficult to expand the inner tube 6B by a small pressure change of blood. For example, a method for detecting clogging of a blood purification device requires a decomposing ability capable of detecting a change of about 5 mmHg on the discharge side of a roller pump. It is very difficult to accurately detect such a minute pressure change by the method using the double-tube type pressure detector 6. In the double-tube type pressure detector 6, the detection sensitivity can be increased by thickening the inner tube 6B. However, if the inner tube 6B is thickened, the amount of blood discharged to the outside of the body increases, which has the adverse effect of increasing the burden on the patient.

Further, in the method using the double-tube type pressure detector 6, the elasticity of the inner tube 6B causes a measurement error. This is because the flexible inner tube 6B is easily deformed, but the hard inner tube 6B is difficult to be deformed. To make the elasticity of the inner tube 6B uniform,
Very high precision is required to keep the amount of deformation constant, which is very difficult, especially at weak pressures. Inner tube 6B
This is because the slight thickness error in (3) considerably deforms the elasticity of the inner tube 6B. The double pipe type pressure detector 6 is
With almost no exception, it is a disposable part commonly called "dispo". This is because it is difficult to sterilize after use.
Disposable parts are used only once, so it is important to mass-produce cheaply. It is extremely difficult to mass-produce inexpensively and increase the accuracy of the inner pipe. Therefore, the method using the double-tube type pressure detector can prevent blood coagulation, but has a drawback that it is difficult to detect minute pressure changes accurately and with a small measurement error.

Further, in the conventional body fluid extracorporeal circulation device shown in FIG. 12, a negative pressure detection sensor 11 is connected to the suction side of the first roller pump 1A. Negative pressure detection sensor 11
Are coupled to detect a reduced flow of blood drawn from the patient. The negative pressure detection sensor 11 detects a negative pressure by deforming a tube made of a soft material. Flexible tubing helps reduce blood flow from the patient
It is crushed by negative pressure. The collapse of the tube is detected by a micro switch (not shown) to detect the negative pressure. The negative pressure detection sensor having this structure has a drawback that it is difficult to accurately detect the negative pressure like the double-tube type pressure detector.

The present invention was developed with the object of resolving this drawback. An important object of the present invention is to prevent minute pressure changes on the discharge side of the roller pump without contacting body fluid with air. Can be accurately detected with a small measurement error,
Moreover, it is an object of the present invention to provide a method for detecting clogging of a body fluid extracorporeal circulation device, which can reduce the priming volume and the burden on the patient by reducing the drip chamber of the blood circuit. Another important object of the present invention is to provide a method for detecting clogging of a body fluid extracorporeal circulation device in which the negative pressure detection sensor can be omitted if necessary.

[0009]

The clogging detection method for an extracorporeal liquid circulation device according to the present invention has the following constitution in order to achieve the above object. In order to overcome the drawbacks of the method using the double-tube pressure sensor 6 shown in FIG. 13, the present inventor first connected an electromagnetic flow meter to the discharge side of the roller pump, and The flow rate of blood was detected with to detect the degree of clogging. The method of using an electromagnetic flow meter instead of the drip chamber and the double tube type pressure detector has no mechanical moving parts, so there is little concern about failure, and moreover, the blood flow rate can be detected with high sensitivity. It has excellent features.

However, the method using the electromagnetic flowmeter has a drawback that the clogging on the discharge side of the roller pump cannot be accurately detected. That is because the electromagnetic flowmeter cannot detect pressure. In the body fluid extracorporeal circulation device, even if the filter or the like on the discharge side of the roller pump is clogged, the flow rate of blood or the like is slightly reduced. This is because the roller pump 1 has a constant flow rate characteristic. The method of measuring the flow rate and detecting the clogging can detect the clogging of the device in which the flow rate decreases. However, in the roller pump, which is a constant flow pump, the flow rate hardly decreases even when the discharge side is clogged. This is because the roller pump crushes the flexible hose 9 with the two rollers 8 as shown in FIG. 1 to pump blood or the like.

Therefore, although the method of measuring the flow rate by the electromagnetic flow meter to detect the clogging has various excellent points, the clogging condition can be surely detected by accurately detecting the minute pressure change on the discharge side of the roller pump. There are fatal drawbacks that are difficult to detect. As a result of further trial and error, the present inventor succeeded in detecting a minute pressure change of body fluid extremely accurately by effectively utilizing the unique discharge characteristic of the roller pump which is a constant flow rate characteristic. did.

In the roller pump, the flexible hose 9 is crushed by the roller 8 and pressure-fed, so that the flow rate on the discharge side pulsates as shown in FIG. Further, when the change in the flow rate is measured in detail, when the discharge side of the roller pump is clogged, the pulsating amplitude becomes large as shown in FIG. When the discharge side of the roller pump is not clogged, the pulsation amplitude becomes small as shown in FIG. However, since the roller pump has a constant flow rate characteristic, the integrated value thereof hardly changes even if the flow rate pulsates. This is because the integrated value is the circulating body fluid amount. 3 and 4 in detail, it can be seen that even if the integrated value of the flow rate does not change, its peak value changes significantly depending on the degree of clogging. When the peak value changes,
The amplitude changes, and the flow rate change value also changes significantly.
Focusing on this point, the present inventor succeeded in accurately detecting the clogging condition on the discharge side of the roller pump by using the electromagnetic flowmeter.

Therefore, the clogging detection method for the extracorporeal fluid circulation device according to the present invention uses a roller pump to circulate the extracorporeal fluid outside the body and to install a filter for filtering the extracorporeal fluid in the circulation path. This is an improvement of the clogging detection method.

Further, in the method of the present invention, an electromagnetic flow meter is connected to the discharge side of the roller pump, and any one of the amplitude, peak value and change value of the pulsating body fluid flow rate is detected by the electromagnetic flow meter, and the roller is detected. It is characterized by detecting clogging on the pump discharge side.

The peak value, change value, and amplitude of the pulsating body fluid flow rate are, for example, the following values. Difference between maximum value and minimum value, that is, maximum amplitude value, or minimum value

Further, in the clogging detecting method for the external circulation apparatus for body fluid according to the second aspect of the present invention, the electromagnetic flow meter is used together with the negative pressure detecting sensor. Therefore, in the clogging detection method for the extracorporeal liquid circulation device of the present invention, the electromagnetic flowmeter can be used in combination with the negative pressure detection sensor, and the negative pressure detection sensor can be omitted.

[0017]

According to the method for detecting clogging of the apparatus for circulating extracorporeal fluid according to the present invention, the flow rate on the discharge side of the roller pump is measured by an electromagnetic flow meter to detect clogging on the discharge side of the roller pump, but the flow rate is simply detected. Not of. The flow rate on the discharge side of the roller pump changes from the state shown in FIG. 4 to the state shown in FIG. 3 depending on the degree of clogging. When the pressure of the filter 3 on the roller pump discharge side is low, as shown in FIG. 4, it pulsates with a small amplitude. The pulsation of the flow rate is synchronized with the rotation of the roller pump. For example, 0.8H
The flow rate of the roller pump rotated at the cycle of z is 0.8
Pulsates at Hz. As the use time elapses and the filter pressure increases, the amplitude of the pulsating flow rate increases, as shown in FIG.

The most preferable method of detecting clogging of the apparatus for circulating extracorporeal fluid according to the present invention is to detect the amplitude of the flow rate, that is, the difference between the maximum value and the minimum value, by using an electromagnetic flow meter to detect the clogging of the roller pump. Detects a blockage. The amplitude of the flow rate increases almost in proportion to the pressure on the discharge side of the roller pump. FIG. 5 shows the state. In this figure, the horizontal axis shows the pressure (average value) on the discharge side of the roller pump, and the vertical axis shows the output voltage difference of the electromagnetic flow meter corresponding to the amplitude of the flow rate. The output voltage difference of the electromagnetic flow meter corresponds to the amplitude of the flow rate because it is the voltage difference at the maximum flow rate and the voltage at the minimum current.

However, in this figure, bovine blood was used in place of body fluid, the rotation cycle of the roller pump was set to 0.8 Hz, and the average flow rate of the roller pump was set to 100 ml / min for measurement.

As is clear from this figure, the pressure on the discharge side of the roller pump is approximated by a linear function with respect to the amplitude of the pulsating flow rate. Therefore, the clogging detection method for the extracorporeal liquid circulation device of the present invention detects the flow rate with an electromagnetic flow meter, and further detects the amplitude of this flow rate,
It is possible to accurately detect a change in pressure on the discharge side of the roller pump. In this figure, the pressure change of 5 mmHg, which is the pressure change on the discharge side of the roller pump, corresponds to the output voltage difference of 0.5 V of the electromagnetic flow meter corresponding to the amplitude of the flow rate,
Can be accurately detected.

In the above method, the amplitude of the flow rate is detected by the electromagnetic flow meter to determine the degree of clogging on the discharge side of the roller pump, but this method can detect the clogging on the discharge side of the roller pump most accurately. However, instead of the amplitude of the flow rate, it is also possible to detect the maximum value or the minimum value of the flow rate, the maximum inclination gradient of the flow rate, the time width of the specific flow rate, and the like to detect the clogging on the discharge side of the roller pump.

Furthermore, in the clogging detection method for the body fluid external circulation device according to the second aspect of the present invention, since the electromagnetic flowmeter is used in combination with the negative pressure detection sensor, the negative body fluid circulation device shown in FIG. The pressure detection sensor can be omitted. The clogging detection method for the extracorporeal liquid circulation device of the present invention detects the flow rate with the electromagnetic flow meter and calculates the flow rate to detect clogging, so that the flow rate measurement of the negative pressure detection sensor can be detected with the electromagnetic flow meter. The pressure detection sensor can be omitted.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. However, the examples shown below exemplify the clogging detection method of the body fluid external circulation device for embodying the technical idea of the present invention, and the present invention describes the clogging detection method of the body fluid external circulation device as follows. No specific method.

First, an apparatus used for the clogging detection method for the external circulation apparatus of the present invention will be described. The body fluid extracorporeal circulation device shown in FIG. 6 is a device for purifying blood, and includes a first roller pump 1A for sucking blood that is body fluid, and a first electromagnetic flow meter connected to the discharge side of the first roller pump 1A. 7a and a first filter 3A connected to the discharge side of the first electromagnetic flow meter 7a to separate blood into plasma and blood cells,
A second roller pump 1B for transferring blood cells filtered by the first filter 3A and a discharge side of the second roller pump 1B are connected via a second electromagnetic flow meter 7b to convert plasma into a high molecular substance and a low molecular substance. A second filter 3B which is separated into
And a drip chamber 4 for mixing the low molecular weight substance separated by the second filter 3B with blood cells. further,
In order to supplement the components removed by the second filter 3B, a replenishment container 10 is connected between the drip chamber 4 and the discharge side of the first filter 3A via a fourth roller pump 1D.

The first electromagnetic flow meter 7a includes a first filter 3
The clogging of A is detected, and the second electromagnetic flow meter 7b detects the clogging of the second filter 3B.

First electromagnetic flow meter 7a and second electromagnetic flow meter 7b
The structure of is shown in FIG. The electromagnetic flowmeter 7 of this figure includes a hard pipe 7A made of plastic for passing blood, and an AC magnet 7B for applying an AC magnetic field to the facing surface of the hard pipe 7A.
An electrode 7C for detecting an AC voltage generated in a direction orthogonal to the magnetic field of the AC magnet 7B and the flow direction of blood, and an electrode 7C.
The differential amplifier 7D that amplifies the voltage generated at the output, the A / D converter 7E that converts the output of the differential amplifier 7D into a digital amount, and the arithmetic circuit 7F that calculates the output of the A / D converter 7E.

The electrode 7C is fixed by penetrating the hard pipe 7A in a watertight manner. The tip of the electrode 7C is a hard pipe 7A
Is exposed inside. The tip of the electrode 7C is in electrical contact with the blood flowing through the hard pipe 7A. Electrode 7C
Is fixed to the facing surface of the hard pipe 7A. Electrode 7C
The hard pipe 7A fixing the is a disposable part used only for one patient. Therefore, although not shown, the hard pipe 7A has a structure in which both ends are detachably connected to the hose and can be replaced.

The AC magnet 7B preferably applies an AC magnetic field of 100 to 150 gauss to the hard pipe 7A. The voltage generated in the electrode 7C increases in proportion to the magnetic field of the hard pipe 7A. When the magnetic field of the hard pipe 7A is increased, the voltage generated at the electrode 7C becomes higher. However, if the AC magnet 7B is strengthened, the cost of the AC magnet 7B increases. AC magnet 7B
The magnetic field is preferably set in the above range in consideration of cost and generated voltage. However, the magnetic field of the hard pipe 7A can be set in the range of 10 to 1000 Gauss, for example.

The AC magnet 7B comprises an iron core having magnetic poles located on the opposite surface of the hard pipe 7A, and an exciting coil wound around the iron core. The exciting coil is excited with an alternating current of about 30 Hz, for example. If the frequency of the alternating current supplied to the exciting coil is too low, it will be difficult to stably amplify the alternating current amplifier. When the frequency is too high, the exciting coil current becomes small and the voltage generated at the electrode 7C becomes low. The frequency of the alternating current supplied to the exciting coil is, for example, several tens Hz.
It is possible to set in the range from to several hundred Hz.

The hard pipe 7A is, for example, a pipe made of polycarbonate, and the electrode 7C is watertightly fixed to the opposing surface. The electrode 7C is a metal needle such as stainless steel. Electrode 7
C is a differential amplifier 7D with extremely high input impedance
Since it is connected to the input terminal of, it is not necessary to increase the contact area with blood. This is because the voltage can be detected with almost no current flowing through the electrode 7C.

The electrode 7C is connected to the input side of the differential amplifier 7D. The differential amplifier 7D amplifies the AC voltage generated at the opposing electrode 7C. Since the voltage generated at the electrode 7C is small, it can be amplified by the differential amplifier 7D and the post-processing can be performed accurately.
The amplification factor of the differential amplifier 7D is designed so that the output voltage becomes several V when detecting a predetermined flow rate, for example.

The output signal of the differential amplifier 7D is an analog quantity. The A / D converter 7E converts an analog amount into a digital amount at a constant cycle. This is because the arithmetic circuit 7F, which is a microcomputer, calculates the output signal of the differential amplifier 7D to calculate the pressure on the discharge side of the roller pump. The cycle in which the A / D converter 7E converts the output signal of the differential amplifier 7D into a digital amount is sufficiently shorter than the cycle of the output signal of the differential amplifier 7D. For example, 1 cycle of the output signal of the differential amplifier 7D is used. / 10 or less, preferably 1/30
It is set below. For example, when the output signal of the differential amplifier 7D pulsates at 0.8 Hz, the A / D converter 7D
E performs A / D conversion of the output signal of the differential amplifier 7D in a cycle of 100 milliseconds or less, preferably 30 milliseconds or less.
Actually, the A / D converter 7E performs A / D conversion on the output signal of the differential amplifier 7D in a cycle of 1 millisecond or less.

The arithmetic circuit 7F is a microcomputer. The microcomputer operates the digital signal input from the A / D converter 7E to calculate the pressure on the discharge side of the roller pump.

In the apparatus for circulating extracorporeal fluid shown in the figure, when blood flows through the hard pipe 7A, a voltage proportional to the flow rate is generated at the electrode 7C. The voltage generated on the electrode 7C is amplified by the differential amplifier 7D. Therefore, the output voltage of the differential amplifier 7D becomes a parameter indicating the flow rate of blood.

The external circulation apparatus for body fluid shown in this figure has an arithmetic circuit 7
The output voltage of the differential amplifier 7D is calculated by F to detect clogging on the discharge side of the roller pump. The arithmetic circuit 7F is shown in FIG.
The flow rate is calculated according to the flow chart of step 1 to detect clogging on the discharge side of the roller pump.

(1) It is determined whether the voltage output from the differential amplifier 7D has the maximum value (Vmax). The step (1) is looped until the output signal of the differential amplifier 7D reaches the maximum value (Vmax). (2) When it is determined that it is the maximum value (Vmax), the maximum value (Vmax) is stored in the memory. (3) It is determined whether the output voltage of the differential amplifier 7D is the minimum value (Vmin), and step (3) is looped until the output voltage reaches the minimum value (Vmin). (4) The minimum value (Vmin) is stored in the memory.

(5) Maximum value (Vmax) and minimum value (Vmin)
The differential voltage (V) is calculated. The difference voltage (V) is the difference between the output voltages of the differential amplifier 7D, that is, the amplitude of the output signal of the differential amplifier 7D. The amplitude of the output signal of the differential amplifier 7D corresponds to the amplitude of the pulsating blood flow rate. The blood flow amplitude is a function of the pressure on the discharge side of the roller pump.
Therefore, the differential voltage (V) is a function indicating the pressure on the discharge side of the roller pump. FIG. 5 is a graph showing the amplitude of the output pressure of the differential amplifier 7D with respect to the pressure on the discharge side of the roller pump, that is, the difference voltage (V).

(6) The difference voltage (V) is compared with the reference voltage (Vs) stored in advance in the arithmetic circuit 7F.
When the difference voltage (V) is lower than the reference voltage (Vs), the process loops to step (1). (7) When the differential voltage (V) is higher than the reference voltage (Vs), the filter is clogged. The reference voltage (Vs) for comparing the differential voltage (V) is set to a voltage when the filter is clogged and the pressure on the discharge side of the roller pump reaches a set value. For example, as shown in FIG.
When the pressure on the roller pump discharge side changes by 5 mHg when the difference voltage (V) and the pressure on the roller pump discharge side change, the difference voltage (V) becomes about 1.2 V and the pressure is 10 m.
As mHg increases, the difference voltage (V) becomes 1.8V. Therefore, if the reference voltage (Vs) is set to 1.2V,
When the pressure on the discharge side of the roller pump increases by 5 mmHg, the clogging of the filter is displayed. When the reference voltage (Vs) is set to 1.8 V, the filter clogging is displayed when the pressure on the discharge side of the roller pump increases by 10 mmHg.

As described above, the method of comparing the difference voltage (V) which is the amplitude of the output signal of the differential amplifier 7D, that is, the amplitude of the pulsating body fluid flow rate with the reference value, is the most accurate in the pressure on the discharge side of the roller pump. Has a feature that can detect However, the present invention can also detect the clogging of the filter by detecting the peak value of the body fluid flow rate in the step shown in FIG. 9.

The method of FIG. 9 detects clogging of the filter in the following steps. (1) The voltage output from the differential amplifier 7D is the maximum value (Vm
ax) is determined. The step (1) is looped until the output voltage of the differential amplifier 7D reaches the maximum value (Vmax). (2) When it is determined that it is the maximum value (Vmax), the maximum value (Vmax) is stored in the memory. (3) The average voltage (Vm) is calculated from the output signal of the differential amplifier 7D. The average voltage (Vm) is calculated by integrating the output signal of the differential amplifier 7D for one cycle or more and dividing the integrated value by time. (4) The difference voltage (V) between the maximum value (Vmax) and the average voltage (Vm) is calculated. The difference voltage (V) is a voltage indicating how high the maximum value (Vmax) of the output voltage of the differential amplifier 7D is with respect to the average voltage (Vm). When the output signal of the differential amplifier 7D is vertically symmetrical with respect to the average voltage (Vm), the difference voltage (V) becomes half the amplitude of the output signal of the differential amplifier 7D. Since the amplitude of the output signal of the differential amplifier 7D corresponds to the amplitude of the pulsating blood flow rate, the differential voltage (V), which is half the amplitude, also shows half the amplitude of the blood flow rate. It is a function showing the pressure on the side. Therefore, the average voltage (Vmax) of the maximum value (Vmax)
The differential voltage (V) with respect to m) is a function indicating the pressure on the discharge side of the roller pump.

(5) The differential voltage (V) is compared with the reference voltage (Vs) stored in advance in the arithmetic circuit 7F.
When the difference voltage (V) is lower than the reference voltage (Vs), the process loops to step (1). As shown in FIG. 8, the reference voltage (Vs) is set to a half voltage value as compared with the method of FIG. 8 for detecting the amplitude of the differential amplifier 7D.

(6) When the difference voltage (V) is higher than the reference voltage (Vs), the filter is clogged. The reference voltage (Vs) for comparing the differential voltage (V) is set to a voltage when the filter is clogged and the pressure on the discharge side of the roller pump reaches a set value. For example, when the pressure on the discharge side of the roller pump changes and the pressure becomes 50 mmHg, the differential voltage (V) becomes about 7.7 V and the pressure becomes 5 m.
When mHg changes, the difference voltage (V) changes by 0.5V.
Therefore, when the reference voltage (Vs) is set to 7.7 V, the filter clogging is displayed when the pressure on the discharge side of the roller pump rises to 50 mmHg. Reference voltage (V
When s) is set to 9.2 V, when the pressure on the discharge side of the roller pump rises to 60 mmHg, the clogging of the filter is displayed.

Further, the filter is clogged, the pressure on the discharge side of the roller pump becomes high, and the differential amplifier 7D
As the amplitude of the output pressure increases, the minimum value (Vmin) also decreases, so it is possible to detect clogging of the filter by comparing the minimum value (Vmin) with the average voltage (Vm). It is not always necessary to compare the maximum value (Vmax) and the minimum value (Vmin) with the average voltage (Vm). This is because the roller pump is a constant flow pump, so that the change in the flow rate is small.

Furthermore, the filter is clogged,
When the difference between the maximum value (Vmax) and the minimum value (Vmin), that is, the amplitude increases, the maximum inclination gradient of the pulsating differential amplifier 7D output signal also increases. Therefore, the differential amplifier 7D
It is also possible to detect the clogging of the filter by detecting the maximum slope of the output signal. Further, when the amplitude of the output signal of the differential amplifier 7D is increased, the time for which the voltage is close to the maximum value (Vmax) and the time for the voltage is close to the minimum value (Vmin) are shortened. This is because the slope is steep and the peak width is narrow. Therefore, the maximum value (Vmax) and the minimum value (Vmi
It is also possible to detect clogging of the filter by detecting the time width of n).

Further, as shown in FIG. 2, the maximum value (Vma
It is also possible to detect the clogging of the filter by detecting the time width of the voltage lower than the predetermined value from x). In this figure, the clogging of the filter is detected by detecting the time width of the voltage value lower by 0.2 V from the maximum value (Vmax). This is because when the filter is clogged and the pressure on the discharge side of the roller pump becomes high, the output voltage of the differential amplifier 7D has a narrow time width near the peak as shown in FIG. 3 according to the characteristic shown in FIG. . FIG. 10 is a graph showing the pressure on the discharge side of the roller pump with respect to the time width in which the output voltage of the differential amplifier 7D becomes 0.2 V lower than the maximum value (Vmax). As shown in this graph, when the filter is clogged and the pressure on the discharge side of the roller pump increases, the maximum value (Vma
The time width when the voltage becomes 0.2 V lower than x) becomes gradually shorter. Therefore, the clogging of the filter can be detected by detecting the time width in which the output voltage of the differential amplifier 7D reaches a predetermined value.

Furthermore, the amplitude of the differential amplifier 7D can be detected in real time without using a microcomputer. FIG. 11 shows a circuit for detecting the amplitude of the differential amplifier output signal, instead of the A / D converter and the arithmetic circuit which is a microcomputer. This circuit is
An integrating circuit 7G that shifts the transfer of the output signal of the differential amplifier 7D by 90 degrees, a multiplier 7H that separately squares the signals on the input side and the output side of the integrating circuit 7G, and the output signals of the two multipliers 7H are added. And an adding circuit 7I for This circuit performs the following operation to detect the amplitude of the output signal of the differential amplifier 7D.

The output signal of the differential amplifier 7D is set to Asinωt
Then, the output signal of the integrating circuit 7G becomes Acosωt. This is because the integrating circuit 7G shifts the transfer of the signal of Asin ωt by 90 degrees. Since the two multipliers 7H square the input signal, their output signals are A ² sin ² ωt and A ² sin ² ωt
² cos ² ωt. Since the squared signals are added by the adder circuit 7I, the output signal of the adder circuit 7I becomes A ² sin ² ωt + A ² cos ² ωt. This equation can be transformed into A ² (sin ² ωt + cos ² ωt). Since sin ² ωt + cos ² ωt = 1, the adder circuit 7
The output signal of I is A ² indicating the amplitude. Therefore, this circuit compares the output signal of the adder circuit 7I with the set value and can determine that the filter is clogged when the output signal is higher than the set value. However, since this detection circuit calculates the amplitude by using the output signal of the differential amplifier 7D as a sine wave, when the output signal of the differential amplifier 7D has a waveform approximate to a sine wave, the discharge side of the roller pump is Can detect clogging.

Further, since the method for detecting clogging of the extracorporeal fluid circulation device of the present invention detects the flow rate of body fluid with an electromagnetic flow meter, the negative pressure detection sensor required for the conventional extracorporeal fluid circulation device shown in FIG. 12 is used. Can be omitted. This is because the amount of body fluid inhaled from the patient into the body fluid external circulation device can be detected by detecting the body fluid flow rate with the electromagnetic flow meter.

[0049]

The clogging detection method for an external circulation apparatus of the present invention uses an electromagnetic flow meter to prevent a minute pressure change on the discharge side of a roller pump with a small measurement error without bringing the body fluid into contact with air. It has the features that it can be detected accurately and that the amount of body fluid discharged from the patient can be reduced to reduce the burden on the patient. This is because the electromagnetic flow meter detects changes in the pulsating flow rate and calculates the pressure on the discharge side of the roller pump.

Further, the clogging detection method for the extracorporeal liquid circulation device according to the present invention, like the conventional double-tube pressure detector,
The flexible inner tube is not elastically deformed to detect pressure. The change in flow rate is electrically detected by an electromagnetic flow meter, and the pressure on the discharge side of the roller pump is calculated from the pulsating state. Therefore, it is not necessary to use a part that causes a measurement error such as an inner tube, the pressure change on the discharge side of the roller pump can be accurately measured with a small measurement error, and the variation in the measurement error to be used parts can be reduced. Features are also realized.

Further, in the clogging detection method for the external circulation apparatus of the present invention, the flow rate is detected by the electromagnetic flow meter, and the clogging is detected by calculating the flow rate. It has the feature that it can be sucked out of the body and detect the blood flow rate. Therefore, the feature that the external circulation apparatus for body fluid can be simplified is also realized.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a roller pump.

FIG. 2 is a graph showing a change in flow rate on the discharge side of the roller pump.

FIG. 3 is a graph showing a flow rate change when a filter on a discharge side of a roller pump is clogged.

FIG. 4 is a graph showing changes in the flow rate when body fluid smoothly passes through the filter on the discharge side of the roller pump.

FIG. 5 is a graph showing the pressure on the discharge side of the roller pump with respect to the amplitude of the differential amplifier output voltage of the electromagnetic flow meter.

FIG. 6 is a circuit diagram showing a schematic connection state of mounting used in the clogging detection method of the body fluid external circulation device of the present invention.

FIG. 7 is a schematic sectional view of an electromagnetic flow meter.

FIG. 8 is a flow chart diagram in which the arithmetic circuit calculates the output voltage of the differential amplifier and detects clogging on the discharge side of the roller pump.

FIG. 9 is a flow chart diagram in which the arithmetic circuit calculates the output voltage of the differential amplifier and detects clogging on the discharge side of the roller pump.

FIG. 10 is a graph showing the pressure change on the discharge side of the roller pump with respect to the time width of the set value of the differential amplifier output voltage of the electromagnetic flow meter.

FIG. 11 is a circuit diagram for calculating the amplitude of the differential amplifier output signal by calculating the output voltage of the differential amplifier in real time.

FIG. 12 is a circuit diagram showing an example of a conventional body fluid external circulation device.

FIG. 13 is a circuit diagram showing an example of a conventional external circulation device for body fluids.

[Explanation of symbols]

1A ... Roller pump 1B ... Roller pump
1C ... Roller pump 1D ... Roller pump 2 ... Purification means 3A ... Filter 3B ... Filter 4 ... Drip chamber 4A ... Drip chamber 4B ... Drip chamber 5A ... Pressure sensor 5B ... Pressure sensor 5
C ... Pressure sensor 6 ... Pressure detector 6A ... Outer tube 6B
… Inner tube 6C… Pressure gauge 7… Electromagnetic flow meter 7a… Electromagnetic flow meter 7b
... Electromagnetic flowmeter 7A ... Hard pipe 7B ... AC magnet 7C ... Electrode 7D ... Differential amplifier 7
E ... A / D converter 7F ... Arithmetic circuit 7G ... Integrating circuit 7
H ... Multiplier 7I ... Addition circuit 8 ... Roller 9 ... Hose 10 ... Supply container 11 ... Negative pressure detection sensor

Claims (2)

[Claims] 1. A method of detecting clogging of a body fluid external circulation device, wherein a roller pump is used to circulate body fluid outside the body, and a filter for filtering body fluid is provided in a circulation path. Clogged external fluid circulation device characterized by detecting the clogging on the discharge side of the roller pump by connecting the meter and detecting any of the amplitude, peak value, and change value of the pulsating body fluid flow rate with an electromagnetic flow meter. Detection method. 2. The method for detecting clogging of a body fluid external circulation device according to claim 1, wherein an electromagnetic flow meter is also used as a negative pressure detection sensor.