JPS5910227B2 - Ultra-filtration measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-P excess measuring device for measuring the amount of excess water removed from the blood, so-called ultra-extreme excess, in hemodialysis therapy for patients with renal failure or debilitation. .

Hemodialysis therapy is performed using a device called a hemodialyzer.

In this method, the dialysate and blood are brought into contact through a semipermeable membrane, and waste products in the blood are transferred to the dialysate side due to the concentration gradient, and water is transferred to the dialysate side due to the pressure difference.

The amount of water removed at this time (ultimate excess) is equivalent to the amount of dialysate that flowed into the hemodialyzer from the amount of dialysate that flowed from the hemodialyzer between the start and end of the dialysis. However, it is often difficult to determine the exact value of ultrafluidic overflow at any given time during dialysis.

Usually, the patient's weight is measured and the weight loss is calculated to determine the ultracardiac overdose.

However, this time-consuming method cannot sufficiently take into account factors that cause weight fluctuations such as eating, excretion, sweating, etc. during hemodialysis, which lasts for several hours.

However, since this ultrasonic excess is an extremely important medical element in the treatment of uremic patients, it is desired to provide a method that can accurately measure it.

Therefore, first, a method as shown in FIG. 1 can be considered.

In this method, flowmeters 4 and 5 are provided in the middle of the inflow device 2 and outflow path 3 for the hemodialyzer 1, and the inflow and outflow amounts to the hemodialyzer 1 are measured by the flowmeters 4 and 5, and each flow rate is The purpose is to find out the amount of water removed (ultimate excess amount) from the difference in the amount of water removed.

That is, the subtractor 6 calculates the difference between the results obtained by the flowmeters 4 and 5, and the integrator 7 adds up the total amount of the difference, thereby measuring the total amount of water removed and displaying it on the indicator 8.

However, while the flow rate of dialysate supplied to the hemodialyzer 1 is usually 500 d/min, the amount of water removed is approximately 500 d/min.
ml/min, and therefore, the flowmeters 4, 5, subtractor 6, and integrator 7 must have an accuracy of 0.01% in order to determine the amount of water removed (i.e., flow rate difference) with an accuracy of 1%. must be used.

In other words, in order to use this method, it is necessary to use extremely expensive equipment, especially flowmeters, which are expensive and very impractical.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide an ultra-p excess measuring device that is inexpensive but highly reliable.

That is, the present invention provides a hemodialyzer, an inflow circuit for supplying dialysate to the hemodialyzer, an outflow circuit for discharging dialysate from the hemodialyzer, and an inflow amount of dialysate flowing into the inflow circuit. an identical flowmeter that alternately measures the outflow amount of dialysate flowing into the outflow circuit, a switching circuit that alternately inserts this flowmeter in the middle of the inflow circuit and the outflow circuit, and receives the output of the flowmeter, and an input state switch that inverts the state of the output signal corresponding to each measurement timing of the inflow and outflow, and calculates the output signal obtained through this input state switch to determine the ultra-F excess amount of the hemodialyzer. The present invention provides an ultrap p-overdose measuring device characterized by comprising means.

Next, one embodiment of the present invention will be described based on FIG.

In the figure, reference numeral 11 denotes a hollow fiber type hemodialyzer, in which a large number of hollow fibers, for example, around 10,000 hollow fibers made of cellulose acetate or the like with an inner diameter of about 200 to 300 μm are stored in a bundle inside a cylindrical main body 12. The inside of the hollow fiber forms a blood chamber, and the outside of the hollow fiber forms a dialysate chamber through which the dialysate passes.

Furthermore, a blood inflow chamber is formed at one end of the blood chamber,
This communicates with the inflow terminal 13.

Further, a blood outflow chamber is formed at the other end of the blood chamber, and this chamber communicates with the outflow terminal 14.

An inflow terminal 15 and an outflow terminal 16 for dialysate are connected to the dialysis chamber, respectively.

A temperature controller 17 is connected to the inflow terminal 15 on the dialysate chamber side.
A dialysate inflow circuit 18 with a dialysate is connected thereto.

A dialysate supply source (not shown) is connected to the inflow side end of the inflow circuit 18.

Further, an outflow circuit 19 for discharging dialysate from the hemodialyzer 11 is connected to the outflow terminal 16 on the dialysate chamber side.

A pump 20 is provided in the middle of this outflow circuit 19 to create a flow of dialysate.

Furthermore, a switching circuit 21 is incorporated between the inflow circuit 18 and the outflow circuit 19, and
The same flowmeter 22, which will be described later, can be inserted alternately between the inflow circuit 18 and the outflow circuit 19.

That is, as shown in FIG. 2, the switching circuit 21 includes a plurality of branch paths 23... and four three-way switching valves 24a.
, 24b, 24c, and 24d are connected, and the flow meter 22 is further provided in the flow path 25 between the three-way switching valves 24a and 24b.

And each of the above three-way switching valves 24a t 24b, 2
By simultaneously switching the directions of 4c and 24d between the state shown by the solid line and the state shown by the dotted line, the flowmeter 22 can be inserted alternately between the inflow circuit 18 and the outflow circuit 19.

In other words, each three-way switching valve 2 4 a t 2 4 b t
When the direction of 2 4 c t 2 4 d is set to the state shown by the solid line, the dialysate flows through the path shown by the solid line arrow.

In addition, each three-way switching valve 24a t 24b, 24c
, 24d are switched to the state shown by the dotted line, the dialysate flows halfway between the inflow circuit 18 and the outflow circuit 19 through the path shown by the dotted line arrow.

Therefore, in the flow path 25 provided with the flow meter 22, the flow always flows in the same direction.

Then, the same flow meter 22 measures the flow rate of the dialysate.

In other words, each three-way switching valve 24a t 24b t 24
By switching the direction of c t 24d, the flow rate of the dialysate flowing through the inflow circuit 18 and the outflow circuit 19 can be measured with the same flowmeter 22.

Further, the flow meter 22 converts the flow rate etc. into an electrical analog signal and outputs it, and its method is not particularly limited, but for example, an impeller type, a differential pressure type, an electromagnetic type, etc. Possible methods include the conventional method and the ultrasonic method.

On the other hand, the output signal of the flow meter 22 is
The integrated amount is integrated by the integrator 27 via the indicator 2.
It is displayed as B.

In other words, the integrator 27 and the indicator 28 are connected to the polarity switch 2.
6 constitutes a means for calculating the output signal obtained through the hemodialyzer 11 and detecting an excess amount of ultraviolet P in the hemodialyzer 11.

Further, the polarity switch 26 includes each three-way switching valve 24a.
, 24b t 24c and 24d, and the polarity is reversed when the flow meter 22 measures the flow rate in the inflow circuit 18 and when it measures the flow rate in the outflow circuit 19.

For example, when the flow rate of the inflow circuit 18 is being measured, the value is set to "negative", and when the flow rate of the outflow circuit 19 is being measured, the value is set to be "positive".

Therefore, the integrator 27 shows the difference between the respective flow rates, that is, the ultrapolar excess in one hemodialyzer 11, and this is detected by the indicator 2.
8.

Next, the operating state of the above embodiment will be explained.

First, each three-way switching valve 24a, 24b, 24c, 2
When the direction of 4d is indicated by a solid line, the inflow circuit 18
The dialysate flowing through the outflow circuit 19 is in the direction shown by the solid arrow, and the flowmeter 22 measures the flow rate of the inflow circuit 18, that is, the inflow amount.

Furthermore, when this inflow amount is being measured, it is input to the integrator 27 as a negative output signal.

In this way, the inflow amount for a certain period of time T is integrated on the negative side.

Immediately after this certain period of time T has elapsed, each three-way switching valve 24a
, 24b y 24c t 24d are simultaneously switched to take the direction shown by the dotted line, and from this point on, the flowmeter 22 measures the flow rate of the outflow circuit 19 for a certain period of time T.

Furthermore, each three-way switching valve 2 4 a , 2 4 b t
The polarity switch 26 is also switched in conjunction with the switching operation of the 2 4 C 724d, and the polarity of the output signal of the flowmeter 22 is reversed, so that it enters the integrator 27 as a positive signal and is integrated on the positive side.

In this way, if measurements are continued alternately while switching at regular intervals T, the integrator 27 will integrate the amount of water removed in the hemodialyzer 11, which is the difference between the inflow and outflow amounts, that is, the ultra-ultra-resolution amount. This can be instructed by the indicator 28.

According to the above configuration, the same flowmeter 22 is used to measure the inflow and outflow to the hemodialyzer 11 every fixed period T, and while the flowmeter 22 is measuring the inflow, Integration is performed by switching the polarity using a polarity switch 26 so that the output signal is on the positive side, and so that the output signal is on the negative side while measuring the outflow amount.

Therefore, the errors caused by the flowmeter 22 cancel each other out, and the errors do not accumulate.

For this reason, the flow measurement 22 has a normal level of accuracy (1%).
It is possible to use this method, and it is possible to perform highly accurate measurements.

The above will be compared with the case of the method shown in FIG. 1 and will be explained using mathematical formulas.

Generally, the output value E of a flowmeter is expressed as E-kQ+Eo, where Q is the true flow rate and k is the conversion coefficient.

Note that Eo is an offset and drift amount, and is generally called a zero adjustment error.

In the case of the method shown in Figure 1, there are two flowmeters, and if their output values are E1 and E2, then E1-kIQ1+E0
1 E2 = k2Q2 + EO 2 - (k1+Δk)Q2+(EOI+ΔEO), and the difference is E2 E1=kl(Q2 Qt)+Δk Q2+Δ
Eo, ΔkQ2 becomes an error due to gain error, and ΔEo becomes an error due to offset drift.

Can't be ignored.

On the other hand, in the method of this embodiment shown in FIG. 2, when the flow rate Q1 on the inflow circuit 18 side is measured for a certain period of time T, the integrated output ■1 is V, -f Edt--BT--kQ1T- EoT0 Also, when measuring the flow rate Q2 on the outflow circuit 19 side, the polarity is switched, so V2=-f Edt-+ET=+kQ2T+EoTo, and between 2T, V1+V2--kQ1T-EoT0kQ,,T+EoT
1 kT (Q2 Qt).

In other words, no cumulative error occurs as in the method shown in FIG.

Note that the error caused by the switching operation can be made negligible by setting the fixed time T to a corresponding length.

On the other hand, in the case of the method of the above embodiment, the flow meter 22 measures the inflow and outflow amounts alternately at fixed time intervals T, and is therefore effective in normal cases where there is little variation in the flow rate.

However, in special cases where the flow rate fluctuates frequently, it may cause errors.

The embodiment shown in FIG. 3 improves this point.

Another embodiment shown in FIG.
is added, and when the flow meter 22 in the above embodiment measures the flow rate on the inflow circuit 18 side, it measures the flow rate on the outflow circuit 19; They are designed to operate complementary to each other so as to measure the flow rate of the inflow circuit 18 when the inflow circuit 18 is running.

Note that the branch path 33 of the switching circuit 32 and the three-way switching valves 34a, 34b, 34c, and 34a are the third
Each of the three-way switching valves 34 is connected as shown in the figure.
a, 3 4 b, t 3 4 c, and 3 4 d perform the above operation by switching at fixed time intervals T between the state shown by the solid line and the state shown by the dotted line.

Furthermore, the two flowmeters 22 and 31 that operate complementarily,
They are connected to one integrator 37 via separate polarity switchers 35 and 36, respectively.

Then, the integrator 37 integrates the flow rate difference, and the indicator 38 displays the result.

In this case, when the flowmeter 22 measures the flow rate on the inflow circuit 18 side and the other flowmeter 31 measures the flow rate on the outflow circuit 19 side for the first fixed time T, the output of the integrator 37 is ■1=f (E2-E1)dt-E2T-E1T〇1K202T+Eo2T-k1Q1T-Eo1T.

During the next fixed time T, the flowmeter 22 measures the flow rate in the outflow circuit 19, and the other flowmeter 31 measures the flow rate in the inflow circuit 18 side, so the output is 'z-fT(Et-E2
)dt=k1Q2'r+%,'r k2QtT EO2
TO, and between 2T, V1+■2-k2Q2T+Eo2T-k1Q1T-Eo
1T ten k1Q2T+Eo1T-k2Q, T-Eo2T1(k,+k2)Q2T (kl+k2)QIT1(
It can be seen that k1+k2)(Q2-Q,), the conversion coefficient is approximately doubled, and no cumulative error occurs as in the above embodiment.

In each of the above embodiments, since the output is an analog signal, an analog integrator is directly used as the integrator.

However, even with pulse oscillation type flowmeters or analogue output type flowmeters, by passing through a voltage-to-frequency converter (v/F converter), digital integration such as a reversible counter can be used. is also possible.

In this case, the reversible counter is turned up via a state switch that inverts the input state instead of switching the polarity.
A similar implementation is possible by switching and inverting the state of input to the -DOWN terminal.

As explained above, the present invention alternately measures the inflow and outflow of dialysate into a hemodialyzer using the same flowmeter, and further measures the inflow and outflow when the flowmeter measures the inflow and outflow. During measurement, the state of the output signal of the flowmeter is inverted and inputted to the same calculation section for integration, thereby determining the difference between the inflow and outflow amounts, that is, the ultrafurnace overflow.

Therefore, unlike the case where the inflow and outflow amounts are measured separately using different flowmeters, the errors caused by the flowmeters cancel each other out, and the errors do not accumulate.

In other words, highly accurate measurement is possible even though the excess amount of the ultra-furnace with respect to the total flow rate is extremely small.

Moreover, since the error caused by the flowmeter can be ignored, there is no need to use a particularly highly accurate and expensive flowmeter, and a normal one is sufficient.

Therefore, this ultrafurnace excess measuring device can be made inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a generally considered ultra-sweep overload measuring device, FIG. 2 is a schematic configuration diagram showing one embodiment of the present invention, and FIG. 3 is another embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing an example. 11...Hemodialyzer, 18...Inflow circuit, 19...Outflow circuit, 21...Switching circuit, 22...Flowmeter , 24a , 24b
, 24c y 24ct...---3-way switching valve, 2
6...Polarity switch, 27...Integrator, 28...Indicator, 31...Flowmeter,
34a, 3tb, 34c, 34d. -...-3-way switching valve, 35, 36...Polarity switching device, 37.
...Integrator, 38...Indicator.

Claims (1)

[Claims] 1 A hemodialyzer, an inflow circuit that supplies dialysate to this hemodialyzer, an outflow circuit that discharges dialysate from the hemodialyzer, an inflow amount of dialysate that flows into this inflow circuit, and a dialysis flow that flows into the outflow circuit. An identical flowmeter that alternately measures the outflow amount of liquid, a switching circuit that alternately inserts this flowmeter in the middle of the inflow circuit and outflow circuit, and a switching circuit that receives the output of the flowmeter and measures the inflow and outflow amount. an input state switch that inverts the state of the output signal corresponding to each measurement period of the scene, and a means for calculating the output signal obtained through the input state switch to determine the extra-furnace overflow of the hemodialyzer. An ultra-p excess measurement device characterized by: