JPH01210826A - Ultrafiltration quantity measuring instrument using ultrasonic difference flow meter and ultrafiltration quantity controller - Google Patents

Abstract

PURPOSE:To measure a difference flow rate of a fluid with high accuracy, and also, to apply an ultrasonic difference flow meter to a blood dialyzing system so that the ultrafiltration quantity can be measured and controlled correctly by providing a simple measuring circuit and an arithmetic circuit, etc. CONSTITUTION:Ultrasonic transmitter-receivers 18a, 18b, 20a and 20b are placed so as to be opposed to each other at the same clearance against duct lines 10, 12 through which a fluid to be measured flows, respectively, and these transmitter-receivers are placed in series so that the fluids to be measured in each duct line become opposite directions to each other. Subsequently, by constituting a measuring circuit by bringing these transmitter-receivers to phase locked loop connection, a flow meter which can derive simply a difference flow rate of each fluid is obtained. Accordingly, by using this flow meter for measuring a flow rate of a dialytic liquid system to a dialyzer 42 of a blood dialyzing system, a measurement of the ultrafiltration quantity can be attained simply and with high accuracy. Also, by the ultrafiltration quantity to be detected, a control of the ultrafiltration quantity can be attained simply and with high accuracy by controlling a dialytic liquid outflow quantity especially of a dialytic liquid rate.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a hemodialysis system, and in particular to a method for easily and highly accurately measuring the amount of dialysate delivered to a dialyzer during hemodialysis using ultrafiltration. The present invention relates to a device that measures and controls the amount of ultrafiltration using an ultrasonic differential flow rate needle.

[Conventional technology]

Generally, in a hemodialysis system, waste products are removed and abnormalities in electrolytes and acid-base balance in the blood are removed by movement of solutes due to the concentration difference between blood and dialysate through the semipermeable membrane of the dialyzer. correction and ultrafiltration removes excess fluid from the patient. In correcting such excess fluid, a particularly rapid decrease in body fluid causes a drop in blood pressure and an imbalance syndrome in the patient, resulting in a very dangerous situation. To solve this problem, conventional hemodialysis systems either use two metering pumps or metering containers to control the amount of dialysate in and out of the dialyzer at a constant level, or measure the ultrafiltration rate of the dialyzer to limit the amount of dialysate. Methods of controlling external filtration pressure are known.

However, in a hemodialysis system, approximately 1,501 dialysis fluids are required for one treatment for one patient. in this case,
The permissible error in the amount of water removed from the patient is approximately 150 m1.
Therefore, it is necessary to ensure an error of about 0.1% for the dialysate. In order to maintain this level of accuracy, it is necessary to regularly and rigorously maintain and inspect the membranes and flow path switching valves in high-precision metering pumps and metering containers, and to prevent foreign objects from entering the flow path. However, there are disadvantages such as the possibility that the precipitates and the like may get caught in the valve part and impair quantitative performance.

A method has also been proposed in which the inflow and outflow of dialysate into a dialyzer is directly measured with a flowmeter, and the amount of ultrafiltration is measured from the difference in flow rate.

However, it is difficult to put this into practical use because a flowmeter with the measurement accuracy described above cannot be obtained.

Recently, a pair of ultrasonic transducers are arranged facing each other with a predetermined distance M apart from each other in a pipe through which a fluid to be measured flows, and the ultrasonic propagation path connecting these ultrasonic transducers is formed into a phase-locked loop ( (hereinafter referred to as PLL), and detects the oscillation frequency of the PLL in a state in which the ultrasonic waves propagate in the forward and reverse directions with respect to the fluid flow using the PLI-. An ultrasonic flowmeter has been developed that can perform simple and highly accurate flow measurement, and has a configuration that determines the flow velocity of the fluid to be measured.

This type of ultrasonic flow meter can be applied to measure the differential flow rate between two fluid systems, for example, by coaxially connecting a tube with no flow in the sending direction and a tube with no flow in the return direction. arranging and joining these tubes via an ultrasound-transparent wall, and providing a first ultrasonic transducer and a second ultrasonic transducer at each outer end of the two tubes, respectively; By providing an inflow short tube near each outer end of the two tubes, and by providing an outflow short tube near the other end where the two tubes join, ultrasonic pulses can be generated from both ends of the joined tubes. By sending out an oscillation frequency expressed as the reciprocal of the delay time depending on the flow of each fluid, the difference in the flow velocity of both fluids can be determined from the difference in these frequencies, regardless of the sound speed in the fluid, and from this, the appropriate A differential flow rate needle capable of measuring a differential flow rate has been proposed (Japanese Unexamined Patent Publication No. 57-94616).

[Problem to be solved by the invention]

However, when measuring the differential flow rate between two fluids to be measured using the flow rate measurement method of the conventional ultrasonic flowmeter described above, for example, a conventional differential flow rate needle requires a special flow path pipe for measurement. This not only makes the piping configuration complicated, but also
There is a drawback that it is difficult to measure the differential flow rate of fluid in existing piping. Therefore, if a conventional ultrasonic flowmeter is installed for each pipe and the differential flow rate is calculated from the flow rate measurement value of each flowmeter, a large number of common measurement circuits and calculation circuits are required, which increases cost. There is. To solve this problem, for example, a circuit is configured to share common measurement pipes and arithmetic circuits of each flow meter, and the time difference or phase difference is compared for each ultrasonic measurement signal of the directly opposing flow rate, and the PLL is used to order the fluid. A method of determining the frequency difference in the direction and the opposite direction has also been proposed, but in this case, when the differential flow rate of the fluid is approximately equal, the oscillation frequency of the PLL is unstable, resulting in a large measurement error.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to not only eliminate the need for a special piping configuration, but also to measure the differential flow rate of a fluid with high accuracy using a simple measuring circuit and arithmetic circuit. An ultrafiltration rate measuring device that constitutes an ultrasonic parallel flowmeter that can determine If, and can appropriately measure and control the ultrafiltration rate by applying this ultrasonic parallel flowmeter to a hemodialysis system. and to provide an ultrafiltration rate control device.

[Means to solve the problem]

The ultrafiltration rate measuring device using the ultrasonic differential flow rate 8c according to the present invention includes a pair of ultrasonic transducers placed in the dialysate inflow conduit and dialysate outflow conduit with the same distance between each other. and interconnecting transducers arranged in series with each of the pipes and provided at one end of each of the pipes so that the dialysate flows in opposite directions by a repeater via a switching device, A transducer provided at the other end of the pipe is connected via a switch in a phase-locked loop equipped with a 9II oscillator on the voltage side, and the frequencies of the oscillation output signals of the phase-locked loop are detected and the frequencies of the oscillation output signals of the respective pipes are detected. The device is characterized by being provided with an arithmetic circuit that calculates the differential flow rate of the dialysate flowing through the dialysate.

In the ultrafiltration measurement device described above, the phase-locked loop that constitutes the ultrasonic parallel flow meter reversibly propagates the ultrasonic signal output from the excitation amplifier to each pipe line via the switch. At the same time, the received ultrasound signal is supplied to a time difference voltage converter via an output amplifier together with an output obtained by dividing the oscillation frequency of the ultrasound signal, and the time difference voltage converter converts the signal from the output amplifier into a signal from the output amplifier. Voltage controlled oscillation F so that the time difference between the divided oscillation signal and the frequency-divided oscillation signal is zero.
It can be configured to control the oscillation frequency of the A unit.

Further, in the present invention, in the ultrafiltration rate measuring device configured as described above, the ultrafiltration rate detection value obtained by the arithmetic circuit that calculates the ultrafiltration rate is compared with the ultrafiltration rate setting value. By providing a control system that adjusts the flow rate of the dialysate flowing out from the dialyzer, an ultrafiltration rate control device can be constructed.

[Effect]

Ultrasonic flow meter using the ultrasonic parallel flowmeter according to the present invention! According to the i-measurement device, ultrasonic transducers are arranged facing each other at a distance of -4 from each pipe through which the fluid to be measured flows,
By arranging these transducers in series so that the fluids to be measured in each pipeline are in opposite directions, and connecting them in a phase-locked loop (PLL) to form a measurement circuit, each of the above-mentioned It is possible to obtain an ultrasonic parallel flow meter that can easily determine the differential flow rate of fluid. Therefore, by applying this ultrasonic parallel flowmeter to measuring the flow m of the dialysate system to the dialyzer of a hemodialysis system, the ultrafiltration rate can be easily and highly accurately measured. Also,
To easily and accurately control the ultrafiltration rate by controlling the dialysate system, especially the dialysate outflow rate, using the ultrafiltration rate detected by the ultrafiltration rate measuring device configured as described above. Can be done.

〔Example〕

Next, embodiments of an ultrafiltration rate measuring device and an ultrafiltration rate controlling device using an ultrasonic differential flowmeter according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block circuit diagram showing the system configuration of an ultrasonic differential flowmeter applied to the ultrafiltration rate measuring device of the present invention. This shows the connection arrangement. In FIG. 1, reference numerals 10 and 12 indicate conduits through which dialysate as a fluid to be measured flows, each having the same inner diameter and length. Each end of these pipes 10.12 has a liquid inlet 1.
4a.

14b and liquid outflow ports 16a, 16b, and an ultrasonic transducer 18a is provided on the internal upstream side and downstream side, respectively.
, 18b and 20a.

20b is arranged. In this case, each tube II i O.

12, opposing ultrasonic transducers 18a and 20a
and the separation distance between 18b and 20b (are set to the same length. Also, the ultrasonic transducers 18a and 18b provided on the upstream side of each pipe line 10.12 are connected to the excitation amplifier via the switch 22. 24 and an output amplifier 26.However, the excitation amplifier 24 is provided with a voltage controlled oscillator 28 that supplies an oscillation signal for outputting an ultrasonic signal having a desired frequency.This voltage controlled oscillator 2
8 divides the frequency of the oscillation output signal with a frequency divider 30, and inputs this frequency-divided output signal and the output signal of the output amplifier 26 to a time difference voltage converter 32 to generate a voltage proportional to the time difference. By inputting this voltage output to the voltage controlled oscillator 28, the frequency of the oscillation output signal is changed in a direction in which the time difference becomes a predetermined value, for example, zero. Further, an ultrasonic transducer 20a provided on the downstream side of each pipe line 10.12.
.

20b is connected via a relay switch 34 to a repeater 36 that relays the ultrasonic signal. Note that the reference numeral 38 is
This is a frequency measuring device that measures the frequency of the oscillation output signal of the voltage controlled oscillator 28, and based on the frequency measured by this frequency measuring device 28, the differential flow rate of the dialysate system, that is, the ultrafiltration rate is calculated by the calculating unit 40. do. Also, reference numeral 4
2 indicates a dialyzer.

Next, a method of measuring the differential flow rate using the circuit having the above configuration will be explained.

Now, the flow rate of the dialysate flowing through one pipe line 10 (the dialysate flowing into the dialyzer 42) is set to V+, and the flow rate of the dialysate flowing through the other pipe line 12 (the dialysate flowing out from the dialyzer 42) is v.
Set it to 2.

At this time, the propagation velocity of the ultrasonic waves in the conduits 10 and 12 (when the direction is forward with respect to the dialysate flowing in the conduit 10, it is in the opposite direction with respect to the dialysate flowing in the conduit 12; On the other hand, when it is in the forward direction, it is in the opposite direction with respect to the dialysate flowing through the pipe line 10), and when the speed of sound is C, it is expressed by the following equations.

Therefore, the time required for the ultrasonic waves to travel a certain distance MJ in each of the pipes 10 and 12 is expressed by the following formula (note that the time for passing through the repeater 36 is ignored).

As a result, the time difference ΔTF, Δ′■゛, of the signals supplied to the time difference voltage converter 32 becomes the following equation.

However, N: frequency division number of the frequency divider 30 f: frequency of the ultrasonic signal Therefore, when the frequency of the oscillation output signal of the voltage controlled oscillator 28 is changed in the direction where the time differences ΔTP and ΔTR become zero, and stabilized. The frequency of is obtained by the following equation.

c-VI Cv2 f2 Rewriting the above equation, i! (2c10v+ -V2) NC2+C
V, -CV2-VIV2) f+... (9) R(2C+V2-Vl) Nc2+cv2
CV + VI V2 ) f2... (10) Here, since C2 >> CV + CV2 VI V2 and C2 >> CV 2CV + V + V 2,... (II) Therefore, the frequencies f+ and ft are By measuring with the frequency measuring device 38 and storing it in the computing unit 40, and then calculating the equation (16) with the computing unit, the pipe line 10.12
The difference in the flow rate of the dialysate flowing through the dialysate, v2-v, can be calculated, and based on this, the differential flow rate, that is, the amount of ultrafiltration can be measured.

FIG. 2 shows an embodiment of an ultrafiltration rate control device to which the ultrafiltration rate measuring device described above is applied. That is, in FIG. 2, reference numeral 50 indicates an ultrasonic parallel flowmeter, the internal configuration of which is as shown in FIG. In this embodiment, the dialysate system is provided with a flow rate regulating valve 52 on the inflow side of the dialyzer 42 and a voltage pump 54 on the outflow side of the dialyzer 42. Therefore, in this embodiment, when the ultrasonic parallel flow meter 50 detects the ultrafiltration rate, this detection signal is supplied to the ultrafiltration rate regulator 56 to display the ultrafiltration rate and limit the ultrafiltration rate. It is supplied to the external filtration amount regulator 58. However, the ultrafiltration amount regulator 58 compares the detected value with the set value preset by the ultrafiltration i setting device 60, outputs a predetermined control signal based on the deviation, and controls this control. supplying the signal to the one-pressure pump drive circuit 62;
Controls the pressure relief pump 54. Thereby, the pressure (negative) on the dialysate side of the dialyzer 42 can be controlled to achieve appropriate control of the amount of ultrafiltration.

〔Effect of the invention〕

As is clear from the embodiments described above, according to the present invention,
Transducers and receivers are arranged facing each other at the same distance from the pipes through which the fluid to be measured flows, and these transducers are arranged in series so that the fluids to be measured in each pipe are in opposite directions. The transducer at one end of each pipe is interconnected by a repeater via a switch, and the transducer at the other end of each pipe is connected to the PL via a switch.
By using an L connection and appropriately switching each switch, the propagation direction of the ultrasonic signal is changed and the frequency at which the PLL is stabilized is determined, and the differential flow rate of the fluid to be measured can be easily calculated from the difference between these frequencies. It can be calculated.

Therefore, by applying the ultrasonic parallel flowmeter configured in this manner to the dialysate system for the dialyzer of a hemodialysis system, the amount of ultrafiltration can be easily and appropriately measured. Furthermore, according to the ultrasonic parallel flowmeter, the pipe line for measuring the flow rate not only does not have a specific configuration;
Since they can be placed separately, they can be immediately applied to existing hemodialysis systems.6 Furthermore, the ultrafiltration rate control device configured using the ultrafiltration rate measuring device described above can be used to By always maintaining the dialysate supply to the device at a constant amount (for example, 500 ml/II!n) and controlling the flow rate of the dialysate using a general variable displacement pump, etc., the limit can be reduced. It is possible to control the amount of external filtration (for example, 500 to 517 ml/min) with high precision and at low cost.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. It goes without saying that adjustments can be made and various design changes can be made without departing from the spirit of the invention.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing the configuration of main parts of a hemodialysis system and the configuration of an ultrasonic parallel flow meter showing an embodiment of the ultrafiltration rate measuring device according to the present invention, and FIG. FIG. 1 is a system diagram of main parts of a hemodialysis system showing an example of an external filtration rate control device. 10.12...Pipe lines 14a, 14b...Liquid inlet 16a, 16b...Liquid outlet 18a, 18b, 20a, 20b=Transducer 22...
・Switcher 24... Excitation amplifier 26... Output amplifier 28... Voltage control # oscillator 30... Frequency divider 32... Time difference voltage converter 34... Relay switch 36...・Repeater 38...Frequency measuring device 40...Calculator 42...Dylyzer 50...Ultrasonic parallel flowmeter 52...Flow rate adjustment valve 54...Removal pump 56...Limit Extrafiltration rate indicator 58...Ultrafiltration rate setting device 60...Ultrafiltration rate setting device 62...1 pressure pump drive circuit 64...Drive motor FIG, 1 Blood; Use FIG, 2 Dialysis 1 sentence

Claims (3)

[Claims] (1) A pair of ultrasonic transducers are placed in the dialysate inflow pipe and dialysate outflow pipe with the same distance between each other, and the dialysate flow is reversed in series with each of the pipes. The transducers provided at one end of each of the pipes are interconnected by a repeater via a switch, and the transducers provided at the other end of each pipe are connected via a switch. connected by a phase-locked loop equipped with a voltage-controlled oscillator, and provided with an arithmetic circuit that detects the frequency of each oscillation output signal of the phase-locked loop and calculates a differential flow rate of dialysate flowing through each of the conduits. Ultrafiltration measurement device. (2) The phase-locked loop reversibly propagates the ultrasonic signal output from the excitation amplifier to each conduit via a switch, and also transmits the received ultrasonic signal via the output amplifier. and supplies the oscillation frequency of the ultrasonic signal to the time difference voltage converter together with the divided output, so that the time difference between the signal from the output amplifier and the frequency divided oscillation signal becomes zero by the time difference voltage converter. The ultrafiltration rate measuring device according to claim 1, wherein the ultrafiltration rate measuring device is configured to control the oscillation frequency of the voltage controlled oscillator. (3) A pair of ultrasonic transducers are placed in the dialysate inflow pipe and dialysate outflow pipe with the same distance between each other, and the dialysate flow is reversed in series with each of the pipes. The transducers provided at one end of each of the pipes are interconnected by a repeater via a switch, and the transducers provided at the other end of each pipe are connected via a switch. an arithmetic circuit that is connected by a phase-locked loop equipped with a voltage-controlled oscillator, detects the frequency of the oscillation output signal of the phase-locked loop, and calculates the ultrafiltration amount from the differential flow rate of the dialysate flowing through each of the pipes; an ultrafiltration system comprising: a control system that compares the ultrafiltration rate detection value obtained by the arithmetic circuit with an ultrafiltration rate set value and adjusts the flow rate of the dialysate flowing out from the dialyzer; Volume control device.