JPS60209118A - Device for measuring ultrafiltration rate - Google Patents

Abstract

PURPOSE:To enable exact measurement of an ultrafiltration rate by passing liquid at two stages of different flow rates to two flowmeters which measure the inflow and outflow rates of a dialyzer and calibrating the other flowmeter by using the outputs from the respective flowmeters and the preliminarily measured characteristic value of the one flowmeter. CONSTITUTION:The flow rate of the dialyzing liquid to be admitted to a dialyzer 12 is measured by a flowmeter 16 and the flow rate of the waste dialyzing liquid discharged from the dialyzer is measured by a flowmeter 17. The difference between both flow rates is determined as an ultrafiltration rate. On the other hand, the device is changed over to a measurement mode for the ultrafiltration rate and a calibration mode for calibrating either of the flowmeters 16, 17 by a control part 21. The liquid of the prescribed flow rate is first passed to the flowmeters 16, 17 then the liquid of the flow rate different from the previous flow rate is passed thereto in the calibration mode. The other flowmeter is calibrated on the basis of the characteristic of the one flowmeter in an arithmetic part 27 by using the output signals of the flowmeters 16, 17 obtd. at the respective flow rates and the preliminarily measured characteristic value of either one flowmeter.

Description

[Detailed Description of the Invention] This invention relates to the flow rate of dialysis fluid flowing out from a dialyzer and the dialysis
The present invention relates to an ultrafiltration measurement device that measures the difference between the flow rate of dialysate flowing into a device and the flow rate of dialysate as an ultrafiltration rate.

<Prior Art> As shown in FIG. 1, in a dialysis apparatus, dialysate is supplied to a dialyzer 12 through a fluid supply line 11, and dialysis fluid from the dialyzer 12 is discharged through a drainage line 13. Dialyzer 1
2 is supplied with the patient's blood through a blood line 14,
Blood from which waste products have been removed by dialysis in the dialyzer 12 is returned to the patient through a blood line 15.

, in the conventional ultrafiltration rate measuring device, the liquid supply curve 1
1 and the drain line 13 are respectively provided with flow meters 16 and 17, the flow rate F1 of the dialysate flowing into the dialyzer 12 is measured by the flow meter 16, the measured value 1 is obtained, and the dialysate is discharged from the dialyzer 12. The flow rate FO of the dialysis effluent was measured with the flow meter 17, and the measured value was obtained, and the amount of ultrafiltration was determined as ■. -■I was looking at 1.

However, this conventional ultrafiltration rate measuring device has the following problems. That is, in general, a flow meter has a measurement error.If the flow rate is F, and the flow rate sensor output signal of the flow meter is E, then the following formula holds: E-[70 to 0. K here
is the flow rate-sensor output signal conversion coefficient, Eo is the zero error,
This is the sensor output signal when the pick flow rate F is zero. Also, if the flowmeter output value is ■, then between ■ and E, V
, =)tE1ε holds true. Here, the value is the sensor output signal-flowmeter output value conversion coefficient, and ε is the zero error, that is, the flowmeter output value output when the sensor output signal is zero.

1. Most of the time, this flowmeter output value ■ is used as the final output, and in the conventional ultrafiltration rate measurement/measuring device shown in FIG. 1, the output value Vl of the flowmeter 16 is:

V,=,μIEI1ε1=l'r (kt)'n, ten days. In 161 again. The output value ■2 of the flowmeter 17 is ゛.

V2 = y”2 Ez f 22 = J/u-2 (kq
fosEoz)tε2, respectively. Therefore, the ultrafiltration rate is Vx-V+=72ElsLi1z' (fi
r E r Navi 1) “l” (k2FO+Eo2)+E2
Fuu+Ck, +Fi+Eo+n-ε1=(2 to JL2
Fo-Ak + 閤1%2EO2; C@oH) (ε2-
ε, ) ---(17.Both flowmeters 16 and 17 have no errors. 6 Lunar Id, Vx-Fl, V
2 = FO, l, Takatch〃IK1= 1', EO1
= (1-, = O,) 2 = l in b2, KO1 = g,
= O, and V2-Vl=Fo-pl, which is equal to the true value. However, reality always contains errors.

When the error is zero, the sensor output signal-flowmeter output value conversion coefficient and the flow rate-sensor output signal conversion coefficient are respectively)to,
Let ko be ,,Lr:l: )ta+i3.
Pb) IZ-: Nori+Tunμ2*1(1=l(o
1'Kl 1 Ks''Ko+Δ can be written as 2. Using this, equation (1) becomes equation (2).

v, -V, =○α' ”, l”X ko, t IJ k
z) 7”o − (μo+li, μm) Cka+lLk+
9Fate.

=ノαoko(Fo-ftnname'o(Aka9o-1
1V + King -i) Junin 0ζ'/"2FI:) -Zip,
tFt) 10(i, 2F in μ2Δ.

-A)b+AR+Fi')fCo ----------(
2) Here, the true value of the ultrafiltration rate is only the first term, and the other terms are errors. 1 attack 2 mo 01 vomit. 2 * g l
It depends on the value of '+ε2, which varies depending on the flowmeter. for example.

The flow rate flowing into the dialysis type stop (hereinafter referred to as the inlet side flow rate) is 5.
00 g/min, error of flow meter 16 is +1%.

Flow rate flowing out from the dialyzer 12 (hereinafter referred to as outlet side flow rate)
is 505 me/min, and the error of flowmeter 17 is 11%.
(The error of normal flowmeters is often ±1% or more), the output value of the flowmeter 16 is 505/min.
This is an absolutely incredible value. Normally, there is no practical problem in measuring the ultrafiltration rate as long as the error is within ±10% of the true value, but the inlet flow rate) 1 o o me7 mi
In order for the measurement error of the field F ultrafiltration amount to be within ±lO% at the outlet side flow rate of 505 m (7/min), (50
5-500)X±0.1/2=0.25 ml/mi
, n or more is required. This means that when measuring a flow rate of about 500 mg/min, the error is less than ±0.251500, that is, less than ±0.05%, which is a high degree of accuracy.

Such a highly accurate flow meter is unrealistic.

In the conventional technology in which two flowmeters 16 and 17 are used and the difference in their output values is simply measured as the amount of ultrafiltration, the above-mentioned ΔlpΔkZ, 171'I + , i!
1%2+ Eol 1 EO2ε1. An error due to ε2 occurs, making it impossible to accurately measure the amount of ultrafiltration.

<Summary of the Invention> The object of the present invention is to provide an apparatus for calculating the amount of ultrafiltration from the difference between the flow rate of outflow dialysis fluid and the flow rate of inflow dialysate, without using a particularly high-precision flowmeter.

The purpose is to make it possible to accurately measure the amount of ultrafiltration.

According to this invention, separate flowmeters are used to measure the flow rate of the inflowing dialysate and the flow rate of the drained fluid.

The mode switching means can be used to switch between a measurement mode in which dialysis is performed using a voice filter and the ultrafiltration rate is measured, and a calibration mode in which the characteristics of one flowmeter are used as a reference to calibrate the other flowmeter. It is configured as follows. When switched to the calibration mode, a predetermined flow rate of liquid is passed through the flowmeter that measures inflow dialysate and the flowmeter that measures outflow dialysate.
Then, the liquid is allowed to flow at a flow rate different from the aforementioned flow rate, and the characteristics of one of the flowmeters are determined using the output signal of each flowmeter in each case and the characteristic value of one of the flowmeters. The other flowmeter is calibrated as a reference.

Embodiment> FIG. 2 shows an embodiment of the ultrafiltration rate measuring device according to the present invention, and parts corresponding to those in FIG. 1 are given the same reference numerals. In this invention, there is a mode in which the amount of ultrafiltration is measured under the control of the control unit 21, and a mode in which the ultrafiltration amount is measured by the control of the control unit 21, and
It is possible to switch to a calibration mode in which either one of 7 is calibrated. In its calibration mode, flow meters 16 and 1
7, the fluid is divided into two parts at an extremely high flow rate, each time being made to flow at the same flow rate. Therefore, in this embodiment, the flow meter 16 and the dialyzer 1
An operation valve 22 is connected to the liquid supply line 11 between the dialyzer 1 and the dialyzer 1.
An operating valve 23 is provided in the drain line 13 between the liquid supply line 11 and the flow meter 17, and a side passage 18 is provided between the liquid supply line 11 and the drain line 13, which includes a side passage 18 in parallel with the operating valve 24. Operation valves 25 and 6 are provided, respectively.

In measurement mode, the dialysate in the gfl supply line 11 is.

Flow rate sensor 16a of flow meter 16-operation valve 22-dialyzer 1
2 - Operation valve 23 - Flow through the flow rate sensor 17a of the flow meter 17.

The liquid is discharged through the drain line 13. On the other hand, in the calibration mode, the operating valves 22, 23 and 25 are first closed, and the dialysate flows through the flow rate sensor 16a - the operating valve 24 - the flow rate sensor 17a. When the calibration at this stage is completed, the operation valve 24 is then closed, the operation valve 25 is opened, and the dialysate flows through the flow rate sensor 16a - operation valve 25 - valve 26 - flow rate sensor 17a.

Let El be the output signal of the flow rate sensor 16a, and let F be the flow rate.
According to the above, El=KIF+hill o1 (3).

It was. The output signal of the flow rate sensor 16a is normally very small! 11 signal, it is necessary to convert this output signal E1 to a flowmeter output value Vl corresponding to the flow rate, and this conversion is (3
) Set F in the equation to Vl, and perform the calculation using the equation solved for Vl. This conversion is performed by the signal processing circuit 161) of the flowmeter 16, but since an inherent error occurs in the conversion in the signal processing circuit 161), generally Vx = , /JJ, Ex
+ε,...(4) is the relationship.

On the other hand, the flow rate sensor 17a also has a unique flow rate-sensor output signal conversion formula, which is E2 = KgF+
It can be expressed as Eo:z...(5).

Similarly to the flowmeter 16, the formula for converting the output signal E2 of the flow rate sensor 17a into the flowmeter output value ■ in the signal processing circuit 17b is: V2 =)lzE2+ε2...(6)
It is expressed as

A case will be described below in which the flowmeter 17 is calibrated in the calibration mode based on the characteristics of the flowmeter 16.

The characteristic value %, e, of the flowmeter 16 as a reference is known from the regression line in the regression analysis of the sensor output signal El and output value Vl performed in advance. The flow rate is Fo.

Fo, the output signals of the flow rate sensors 16a and 17a in the case of the flow rate Fo are respectively bl and EC2, and the output signals in the case of the flow rate FO are respectively KQI' and EC2', and the flow rate F
The output values of flowmeters 16 and 17 in case of O are respectively ■1
and “-1 flow rate BpO2, the output value is VO
1' and Vl, and the output value conversion coefficient for 〃 of the flowmeter 17 is %c2, then in the calibration mode, the same flow rate Fo,
Since Fa' is flowing, in each case VO2 = V
QI, VQ2'= VQI', Tsuma D, (4)
and (6), respectively, t kc2. Ec Tsuji E2 %
EC,1+'i: , +,A'CZEcj+ε
It must be z = P + 'EQ 1' + ε1. Therefore, these two formulas.

becomes. Therefore, the calculation unit 27 directly inputs EQ, l', Eog, FAl', and ECi under the control of the control unit 21, and converts these values and 'ξ) known output value conversion coefficient for the flowmeter 16. 〃Using 1 and 61, flow meter 1
The output value conversion coefficient E2 of 7 is calculated from equations (7) and (8).

Then, the signal processing circuits 161) and 17 in the measurement mode
The conversion formula from the sensor output signals Ex and E2 at b to the flowmeter output values v1 and V2 is Vl 7P1 Bi, +6.・
- For (4), calibrate as V2 =)tc2E2sε2.

For example, fi, = 95, E, = 5.15 and F
a = 50 o'ml/min, F.

= 40 ome/fnin time EO1 = 5.37
, Eal=4.32, Eoa-502Eal
l'=4. Oji! To illustrate the case of (3)
From f('7) and equation (8).

, PC2=91j
The conversion formula from the sensor output signal to the flowmeter output value in :, 1) is calibrated as follows: Vl = 95XE1-5,15K, 2 = 99.75XE2 + 4.255.

As described above, in the calibration mode, the characteristics of the flowmeter 16 (y"'
y&l, EO1'+61) as reference flow meter 17
The characteristic of ≠2°ε2) is calibrated. After this, the measurement mode is entered, and the measurement error in the measurement mode will be described below.

The flow rate of dialysate flowing through the flow rate sensor 16a in the measurement mode is FL, and the flow rate of dialysis fluid flowing through the flow rate sensor 17a is LT.
``o'', the output signals of the flow rate sensors 16a and 17a at that time are El and Eo, respectively, and the flowmeter output values are ``1'' and ``0'', respectively, then from equations (3) and (5).

E1=== KIFx −1−EOI, Eo=
In KgFo-1-Eog.

The conversion formula to the flowmeter output value in the signal processing circuits 16b and 17'b is obtained from equations (4) and (9), respectively: ■1=l
t-ξ+ε,...(10λVo=)lczEo+εZ
---(11). Therefore, the measured value of ultrafiltration rate Uo
b is as shown in the following equation.

By the way, as mentioned in the previous calibration mode, tLczEcs
:+6zchi1Ecl+E+, so (3) and (5
) From the formula, z(Kg Fo + E”)+ and x=, u
r (KIFG+EO1) +6. L, therefore Pc
zEoz-)t, fDax' =, 7t 1 f! a
Fc+ε+ )aC2Ks F'-ez, and when this is substituted into (12).

Fo'+Eog and 膓-KIFQ +EO1, EO1
'-KIFO'+ EOl to so EC2-ECZ' To each 2=-~-Ryoichi--(+4) fishing-to, =unidan last-Ctt7ノFc-Fc Fc-1- So (7 ) I Substitute (14) and (15) into (13).

becomes.

Now, if the true value of ultrafiltration rate is Ure, then Ure
is the dialysis fluid flow rate Fo minus the dialysate flow rate F1/
1-,'1 Subtracting the equation (17), we get 8 = ()ob L#a, and the error rate △ is △= lrε, that is, the measurement error of the ultrafiltration rate is ',, /''7 + K1 It depends only on the characteristic value of the flowmeter 16, and does not depend on the characteristic value of the flowmeter 17 at all.In other words, the calibration results in a state equivalent to using two flowmeters with exactly the same characteristics. becomes.

Now, let's explain the case of the previous example.

JllH=95, Fo -50ome/min
, Fo'=400me/mjJl.

Because EC1=5.37, ]JoiKaya=4.32.

5.37-4.32 △= 95 X -I m-0,0025500-40
0, the measurement error of ultrafiltration amount is -0.25%.

In addition, in the measurement mode, set ■1 as the dialysate flow rate.

■0 as the dialysis effluent flow rate (10) and (uX
Further, the calculation section 27 calculates Vo -Vx, and the result is displayed on the display section 28 as the ultrafiltration amount.

When the ultrafiltration rate measuring device according to the present invention is built into or placed alongside a dialysis machine and enters the preparation mode as a dialysis machine, the above-mentioned calibration mode is automatically performed, and then the dialysis mode is entered. Only the measurement mode may be performed in the dialysis mode, or the calibration mode may be automatically performed periodically in the dialysis mode. Alternatively, if necessary, the calibration mode may be manually set to perform the above-described calibration, and then the measurement mode may be manually switched.

FIG. 3 shows an embodiment of the invention using a microcomputer, and parts corresponding to those in FIG. 2 are given the same reference numerals. A central processing unit (hereinafter referred to as CPU) 30 of the microcomputer 29 performs various processes by decoding and executing programs stored in a read-only memory (hereinafter referred to as ROM) 31, and stores information necessary for the processing. The data to be processed and the data being processed are stored in a readable/writable memory (hereinafter referred to as RAM) 32 as necessary. CPU
30 provides a valve control signal to the valve control circuit 34 via the input/output section 33.

The output of the valve control circuit 34 causes the operating valves 22, 23, 24.
25 can be switched and controlled, and the flowmeter output values Vl and V2 of the flowmeter 16.17 and the output signals of the flow rate sensors 16a and 17a in the calibration mode can be taken in through the input/output section 33. is calculated and the result is supplied to the display circuit 28a of the 1 display section 28, and this is displayed on the display z8b.
to be displayed. Regarding the flowmeter 16, a regression analysis is performed in advance between the sensor output signal at the sample point and the flowmeter output value, and from the regression line, the coefficient 15. The values of ε1 are determined and these f values are stored in the ROM 31.

In this embodiment, when started, a program fixed in the ROM 31 enters the calibration mode.

As shown in the flowchart of FIG. 4, in step S1, the operating valve 22
．． 23 and 25 are both closed, while the operating valve 24 is opened and the dialysate passes through the flow rate sensor 16a.

It flows through the operation valve 24 and the flow rate sensor 17a without passing through the dialyzer 12. In this state, in step S2, the output signal Eel of the flow rate sensors 16a and 17a and the value of convex 2 for the same flow rate FO are imported into the RAM 32, and then in step S3, the program in the ROM 31 is loaded.
033, the valve control circuit 34, and the operation valve 22.
2324 is closed and the operating valve 25 is opened. Operation valve 2
A valve 26 is provided in the flow path 5, which allows an arbitrary flow rate FO different from that in the above case to flow. In this state, in step S4, the flow rate sensor 1 for the flow rate Fo'
6a and 17a output signals EQI' and gJ are stored in RAM.
Add 9 to 32. Next, in step S5, the values of the known output value conversion coefficients p1 and ε1 for the flowmeter 16 are stored in the ROM.
Read from 31. Then, in step S6, (wa) and (
8) Calculate c pump ε2 based on the formula, and step S7
Then, the values of μC2 and ε2 are stored in the RAM 32 as output value conversion coefficients of the flowmeter 17 in the measurement mode.

After processing this calibration mode, the CPU 30
According to the program in 31, open the operating valves 22 and 23,
Close the operation valves 24 and 25 to enter the measurement mode.

In the measurement mode, sensor output signals E1 and EO of flowmeters 16 and 17 are output to signal processing circuits 16b and 17, respectively.
In 1), as in the previous example, using equations (10) and (U) using the output value conversion coefficient obtained in the calibration mode,
They are converted into flowmeter output values V1 and ■, respectively.

The data is input to the CPU 3o through the input/output section 33.

Then, (1) - (1) is further calculated, and the result is displayed on the display 281) as the limit excess amount via the display circuit 28a.

The case where the flowmeter 17 is calibrated based on the characteristics of the flowmeter 16 has been described above, but it is also possible to calibrate the flowmeter 16 based on the characteristics of the flowmeter 17 in exactly the same manner by replacing both of them.

Note that the flowmeters 16 and 17 are not necessarily of the same type, and may be constructed of different types, such as 16 being an electromagnetic flowmeter and 17 being an ultrasonic flowmeter.

In addition, two different types of the same flow rate (Fo, Fo'
) The means for flowing the dialysate to the flowmeters 16 and 17 is not limited to the embodiment. For example, the control section 21 and the valve control circuit 34
The setting location of the flow rate switching means controlled by
Not only in the side channel 18 in the embodiment, but also in the liquid supply line 11
- Side channel 18 - Other locations in the flow path of the drain line stop may be used. Alternatively, the bypass 18 and valves 22-26 in embodiments
Omit the dialyzer 12-drain line 13 to the fluid supply line 1.
A flow rate switching means controlled in the same manner as described above may be provided in the flow path, and in the calibration mode, two different types of dialysate having the same flow rate may be made to flow through the dialyzer 12 to the flowmeters 16 and 17. .

In this case, in the calibration mode, no movement of water occurs between the blood flow path and the dialysate flow path of the dialyzer 12.

The pressure in both channels is controlled to be equal.

Further, the liquid flowing in the calibration mode is not limited to dialysate.

<Effects> As described above, according to the present invention, two flowmeters are conventionally used to measure the ultrafiltration rate, which is the difference between the outlet flow rate and the inlet flow rate of the dialyzer. Measurement errors caused by differences in characteristics between the two flowmeters, which were unavoidable in some cases, can be eliminated. Therefore, high-precision measurement is possible without using a particularly high-precision flow meter. Further, the flow path of the flow rate sensor exposed to the dialysis fluid can be cleaned with clean dialysis fluid. Moreover, it is sufficient to know the characteristic values of the flowmeter for only one meter, and the effort required for adjustment can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional extreme excess amount measuring device. FIG. 2 is a block diagram showing an example of the ultrafiltration rate measuring device according to the present invention, FIG. 3 is a block diagram showing an example of the ultrafiltration rate measuring device of the present invention using a microcomputer, and FIG. 4 is a flowchart showing an example of the operation of the apparatus shown in FIG. 3 in a calibration mode. 11: Liquid supply line, 12: Dialyzer. 13 two drain lines, 16. l'7: Flowmeter, 18
: Side path 21: Control section. 22 to 25: operation valve, 26 two valves, 27: calculation section. 292 Microcomputer, 34: Valve control circuit Patent applicant Sanyo Electric Manufacturing Co., Ltd. Figure 1 Figure 2/d Figure 4

Claims (1)

[Claims] The flow rate of the dialysate flowing into the dialyzer is measured with one flowmeter, and the flow rate of the dialysis fluid flowing out from the dialyzer is measured with another flowmeter, thereby limiting the difference between the two flow rates. In the ultrafiltration rate measuring device, mode switching means between an ultrafiltration rate measurement mode and a calibration mode for calibrating either one of the two flowmeters. In the above calibration mode, a predetermined flow rate of liquid is flowed through the two flowmeters, and then a liquid with a flow rate different from the above flow rate is flowed, and the output signal from each flowmeter obtained at each flow rate and the pre-measured An ultrafiltration rate measuring device comprising: a calibration means for calibrating the other flowmeter based on the characteristics of the one flowmeter using the characteristic values of the one flowmeter.