DE2858205C2 - Device for hemodialysis and for withdrawing ultrafiltrate - Google Patents

Description

ren negative pressure to an air separation device upstream of the dialyzer is not possible, since this the Would affect ultrafiltration.

The invention is therefore based on the object of a To create a device of the type mentioned, in which the separation of the excess in the dialysis fluid contained gases can be done as precisely and simply as possible in such a way that an exact balancing the device can be performed.

This task is achieved in that the device for degassing fresh dialysis fluid in the supply line to the balancing unit is switched on and has a pump upstream with which fresh dialysis fluid is used can be supplied with a negative pressure, and the device for degassing used Dialysis fluid with the pump via a lockable Line is connected.

With the device according to the invention, the primary degassing takes place first of all upstream of the "balancing unit". so that fresh dialysis fluid that has already been degassed is pumped into the first balance chamber. Thus takes place thus not the balancing of the components of the dialysis fluid, but rather the balancing the dialysis fluid itself, which has already been degassed, which is a considerable advantage over DE-OS 25 44 258

In addition, the secondary degassing of the dialysis fluid takes place downstream of the dialyzer in the closed Circuit no longer with the ultrafiltrate pump, which according to DE-OS alternates on degassing or withdrawal of ultrafiltrate is switched. According to the invention, an air separation vessel is now used provided downstream of the dialyzer, the sole purpose of which is to separate the air from the used dialysis fluid serves. In this way, an exact balancing can be carried out using the dialysis fluid that has been freed from excess air can be ensured with the device according to the invention.

Furthermore, the air separation tanks are for the primary and the secondary degassing coupled together such that a single pump for degassing for the fresh and used dialysis fluid is sufficient.

The primary degassing is initially upstream of the air separation vessel for the fresh dialysis fluid obtained in that a degassing section is provided through a flow resistance on the one hand and a pump on the other hand is formed. The negative pressure created in this way sets the in the fresh Air contained in dialysis fluid is released, which is separated when it enters the primary air separation vessel will. The negative pressure generated in the degassing section is below the ultrafiltration pressure in the closed one Cycle. As is known, the latter pressure is also in the air separation vessel for the secondary Air separation on.

According to the invention, the secondary air separation vessel with the pump is now upstream of the primary Air separation vessel is arranged, connected, this connecting line being blocked by a valve. This valve can be opened by the signal from a level switch *, which is advantageously in the secondary Air separator is arranged. As a result of the lower negative pressure created by the pump on the primary air separator is generated, the excess air is sucked out of the secondary air separator until the level sensor causes this valve to close.

Thus a pump effects the primary and secondary separation of air, i. H. the degassing of fresher and used dialysis fluid

The subclaims have advantageous developments of the subject matter
The invention is explained below with reference to the drawing:

It shows

F i g. 1 a simplified schematic diagram of the dialysis solution circuit with a balancing device,
F i g. 2 a simplified principle diagram of the dialysis solution circuit with a combination of the functions of balancing and proportional dosing and joint monitoring of both functions,

F i g. 3 shows a more detailed representation of the scheme according to FIG. 2,

3A shows a circuit arrangement for controlling the balancing and metering device,

4 shows a further embodiment of the arrangement according to FIG. 1 to compensate for temperature-related errors in the mass balance,

F i g. 5 a block diagram for the computational compensation of the influence of temperature differences,

F i g. 6 an example of a balancing chamber in a schematic sectional view,

F i g. 7 shows another expanded embodiment of the arrangement according to FIG. 1 for venting the catalyst circuit,

8 shows a more detailed representation of the fluid circuit of a hemodialysis machine,
9 shows an embodiment of the metering device in section.

To explain the basic mode of operation of a balancing device, the relevant part of the liquid circuit is shown in a greatly simplified and schematic manner in FIG. 1. The most important part of this arrangement is the balancing device 1. It comprises two interconnected chambers la and b, the first of which is assigned to the inlet line 2 for the fresh dialysis solution and the second to the outlet line 3 for the used dialysis solution. The balancing device ensures that the amount of fresh dialysis solution flowing through the line 2a to the dialyzer 4 exactly matches the used dialysis solution flowing out of the dialyzer through the line 3a. Due to this property of the balancing device, under these conditions, a volume shift between the blood and the dialysis solution side of the semipermeable membrane 5 in the dialyzer 4, the other side of which is connected to the patient via lines 6, cannot take place under these conditions.

The so-called ultrafiltration rate is therefore zero.

The part of the fluid circuit enclosed between the balancing device 1 and the dialyzer 4 behaves like a closed, volume-constant system. In order to discharge liquid from this system, a withdrawal device 7 is provided, which is connected to a drain 8.
The amount of liquid derived from the system with the aid of the extraction device has to be replaced by an equal amount of liquid due to the properties of the balancing device mentioned. The amount of liquid diverted by means of the extraction device corresponds to the amount of liquid passing through the membrane of the dialyzer, the ultrafiltrate. match. the

The extraction device can now be designed in such a way that control of the ultrafiltration can be achieved.

Very high demands are placed on the accuracy of the balancing device. During hemodialysis treatment typically about 200 liters of dialysis solution are passed through the dialyzer. The amount of ultrafiltrate is typically about 2 to 3 liters and should, apart from a deviation of the order of 0.1 can be precisely determined up to 0.2 liters. The accounting error caused in the balancing device may therefore, if possible, do not exceed the order of magnitude of 1 per thousand. Significant danger can arise then result for the patient when due to a technical error, z. B. by failure of a component larger accounting field occurs and goes unnoticed remains, therefore the balancing device must be required to automatically recognize a functional error and an alarm is triggered in the event of an error.

This necessary security against malfunctions of the balancing system is achieved in that the balancing unit is not only designed to account for incoming and outgoing dialysis solution, but is simultaneously connected together with a metering device to form a control circuit.

The principle of a corresponding extended arrangement is shown in FIG. 2 shown. Here are the same parts with the same reference numerals as in FIG. 1 referred to.

Additional elements to implement a proportional dosing function and for their monitoring are a metering device 9 and an analysis device 10. The metering device is connected to a line 11 fed here and in turn feeds into the supply line 2 via a connection 12.

The analyzing device is directly in the supply line 2 between the balancing device 1 and the dialyzer 4 switched on.

A prerequisite for the intended function of the arrangement shown is. that the balancing device 1 has a periodic mode of operation in which it has a precisely defined volume of dialysis solution per working period forwards. For this defined volume of dialysis solution a fixed volume of concentrate is necessary, which through the metering device 9 is also supplied periodically, the balancing device 1 and the metering device preferably work synchronously.

The water supplied via the line 2 and the concentrate supplied by the metering device 9 form if the proportions are correctly adjusted, a dialysis solution of the desired type after mixing them Composition. This is done by the analysis device that is in the line to the dialyzer is inserted, monitored. Since the parts used in the balancing device to measure the volumes at the same time determine the volume of liquid passed on per working period of the analysis device 10, both the process of proportional dosing and, indirectly, the process of accounting are monitored.

Details on this should be based on the in F i g. 3 will be explained as an example. The balancing device consists of the balancing chambers 22 and 23 and the associated valves 14 to 21. Together with the Dosing device 9, the balancing device also forms a proportional dosing system, the concentrate and water mixes in a predetermined proportion. The analysis device 10 measures one or several parameters characteristic of the composition of the mixture and thereby enables a Control of the functions mentioned.

The two chambers 22 and 23 are an essential part of the balancing device these consist of volume-rigid hollow bodies with two rooms each, which are separated by a movable, tightly closing one Element 24 and 25 are separated from each other, so that when one room is enlarged other space will inevitably decrease in size by the same amount. In the schematic representation of 3, the chambers 22 and 23 are, for example, as Balls and the movable elements 24 and 25 shown as membranes. Important for the real Design of the chambers and the movable ones in them

! 5 elements with regard to the dosing function is also, that the displacement of the movable elements from one extreme position to the other to a reproducible one Volume shift leads. In the case of the in FIG. 3 indicated embodiment, this is for example thereby achieved that the membranes 24 and 25 in their extreme positions completely against the right or put on the left wall of the respective chamber, so that when moving from one extreme position to the other one Volume shift takes place from the amount of the total chamber volume.

The valves 14 to 21 assigned to the balancing chambers form two groups which are actuated alternately. When the valves in group A (15, 17, 18, 20) are open, the valves in group ß (14,16,19,

21) closed, and vice versa. As a result, the two chambers work alternately, periodically exchanging their functions. While one of the two chambers is inserted into the circuit (2a. 3a) of the dialyzer, the other chamber is loaded with new dialysis solution and at the same time the used dialysis solution is displaced into the drain line 3.

When the valves of group A (shown dark) and the valves of group β (shown light) are closed, the chamber 22 is charged with fresh dialysis solution, while the chamber 23 is used to feed the dialyzer. The loading process of the chamber 22 results from the fact that fresh solution flows under pressure through the opened valve 18 into the space 22a, so that the membrane 24 evades and the used dialysis solution located on the other side of the membrane in space 226 through the opened valve 15 into the drain line 3 is displaced. When the membrane is completely in contact with the right wall of the chamber, this charging process is complete.

Meanwhile, the dialysis room is fed from the chamber 23 by adding the fresh Dialysis solution passed through the opened valve 17 via line 2a to the dialyzer and used as dialysis solution from the dialyzer via line 3a and that

opened valve 20 into space 236 of the same chamber is returned. Due to the volume rigidity of the balancing chamber, the amount of liquid returned must exactly match the amount of fluid supplied to the dialyzer. The dialysis solution

flows in a quasi-closed cycle, because the beginning and the end are connected to one another via the movable element in the balancing chamber.

However, there is no mixing of fresh and used dialysis solution. As soon as the

If the membrane in the chamber 23 has been fully applied to the right chamber wall, the process is ended. In order to continue to maintain the flow through the dialyzer, only the valves are switched.

so that the two chambers of the balancing device exchange their functions.

If the valves of group A are now closed and the valves of group B are open, fresh dialysis solution can continue to flow into the dialyzer through the opened valve 14 from space 22a of chamber 22, while the same amount of used dialysis solution from the dialyzer via the open valve 19 is returned to the space 22b on the other side of the membrane. At the beginning of this process, the space 22a is at the maximum and the space 22 £> at the minimum level, since in the previous work cycle, the space 22a, as described, was completely filled with fresh dialysis solution. While the dialyzer is being fed from the chamber 22, the chamber 23, the space 23b of which is completely filled with used dialysis solution from the previous work cycle, is charged with fresh dialysis solution. The fresh dialysis solution flows through the opened valve 21 into the space 23a, and the used dialysis solution located in the space 23b is displaced through the opened valve 16 into the drain line 3.

The switching of the valve groups must take place when the supply of the balancing chamber is out who is currently feeding the dialyzer is exhausted. The charging of the other balance chamber should already be completed by this time, which is indicated by a correspondingly high loading speed can be easily achieved. The signal for switching the valves can be different Way to be won. Since the dialysis solution flow in the dialyzer circuit stops as soon as the membrane is in the the balancing chamber feeding the dialyzer has reached its extreme position, z. B. a flow meter with a device for triggering a signal when the flow falls below a minimum, used for this purpose will. Another possibility is to change the pressure caused by reaching the end position to trigger the switchover function. Known methods are also possible, which provide a direct detection of reaching the end position, z. B. micro switch.

In the described mode of operation, the balancing device takes a specific one in each work cycle Amount of dialysis solution that is generated by the between the two extreme positions of the movable element in the volume shift occurring in the balancing chamber is defined. To each of these from the balancing device absorbed volume unit must now the corresponding amount of concentrate to the supplied Base liquid (e.g. distilled water) added by mixing the concentrate and liquid in the intended ratio to convert the dialysis solution into of the desired composition and concentration. The concentrate is added by the metering device 9. This can for example be designed as a metering pump, which with a or several pump strokes deliver the amount of concentrate belonging to one filling of the balancing chamber. the The activity of the metering device is controlled synchronously with the switching of the valves 14 to 21, i. H. with everyone Loading process one of the balance chambers 22 or 23, the required amount of concentrate is retrieved and the at the same time the inflowing water is mixed in. In Fig. 3, the admixing line 12 is directly connected to the supply line 2 connected to the balancing device. However, this is by no means necessary. It may be more beneficial that Admixture of the concentrate in an upstream part of the water treatment system or directly to be carried out at the water inlet of the device, among other things. to ensure that the concentrate is mixed as homogeneously as possible and reach water.

The analysis device 10 monitors the composition of the dialysis solution in a manner known per se, which flows to the dialyzer. It is common to use electrical conductivity wedge knives for this, however other analysis devices, e.g. B. ion-selective electrodes into consideration. However, it is essential that in the arrangement according to the invention with the aid of the analysis device not only the function of the proportional dosing of concentrate and water is monitored, but indirectly also the balancing function. If, in fact, a defect occurs in one of the components of the balancing device, e.g. B. a failure one of the valves 14 to 21, a leak in the membranes 24, 25 or a leak in the balancing chamber to the outside, see above the dosing function is also impaired, which leads to a corresponding deviation in the composition the dialysis solution leads. Through the usual limit value monitoring of the analysis device an alarm signal is triggered in such cases and the device can also automatically stop working can be set to prevent further effects of the error.

The in F i g. The arrangement shown in FIG. 3 has another important property, namely that it offers the possibility of temporarily canceling the balancing function, but maintaining the function of proportional dosing of concentrate and water. This is e.g. B. important when starting a new dialyzer to first prime the dialyzer with dialysis solution. Due to the properties of the balancing system, this would normally not be possible, since the balancing system removes the same amount of the liquid that is supplied and thus keeps the liquid volume in the dialyzer circuit constant.
The operating mode with the balancing function canceled is achieved by controlling the valves differently. Starting from a state in which one balance chamber (e.g. 22a) is completely filled with fresh dialysis solution and the other balance chamber (e.g. 23 £>) is completely filled with used dialysis solution, valves 19 and 20 as well as an in the drain line lying valve 26 is closed. The valves 15 and 16 are opened, and the valves 16 and 17 as well as 21 and 14 now form two groups which are alternately opened and closed. Controlling the said

so valve groups can either in the manner described above on the basis of a detection of the extreme positions the membrane take place or, for the sake of simplicity, by a time cycle that is selected to be sufficiently slow, so that the membranes are certainly already in the end positions at the time of switching.

If, under the conditions mentioned, the valves 21 and 14 are opened while the valves 18 and 17 are closed, the fresh dialysis solution flows through the valve 21 into the space 23a of the balance chamber 23 and is displaced from the space 23b on the other side of the membrane via the opened space Valves 15 and 16 the corresponding amount of liquid in the space 22b of the balancing chamber 22. Accordingly, the same amount of fresh dialysis solution is displaced from the space 22a and fed through the open valve 14 to the dialyzer. The process ends when the membranes have reached their extreme positions.

The valves 21 and 14 are then closed and the valves 18 and 17 are opened. The fresh dialysis solution now flows through the valve 18 into the space 22a of the balancing chamber 22 and displaces over the membrane the solution located in room 22i> via the opened valves 15 and 16 into room 23oder balancing chamber 23, so that the fresh dialysis solution previously filled into the space 23a in the same amount over the Valve 17 is passed to the dialyzer. After the membranes have reached their extreme positions, takes place a «renewed switching of the valve groups 18, 17 and 211,14, so that the two chambers 22,23 again swap their functions.

As a result of the method of operation described, the dialysis solution becomes the same as in the normal, balancing operating mode in certain portions fed to the dialyzer through the between the two extreme positions of the movable element in the balancing chambers occurring volume shift are defined. in the The metering device feeds the concentrate in the same cycle. The function of proportional dosing of The water and concentrate therefore remain while the balancing is canceled.

A circuit arrangement for controlling the valves 14 to 21 and 26 and the metering device 9 accordingly the functions described is shown in FIG. 3A shown. It's just a simple one Embodiment that is replaced in various ways by other circuit arrangements can be. If the actuation of the valves and the dosing device is not as assumed here, takes place by solenoids, but z. B. hydraulic or pneumatic, are equivalent working control devices can be used without further ado in accordance with the general state of the art.

The switchover from the normal balancing operating mode to the non-balancing operating mode is carried out by a relay 70 with 7 changeover contacts, to the outputs of which the solenoid coils of the valves 10 to 18 are connected. In the illustrated rest position of the contacts, the solenoid 14s to 21 a and 26a of the valves 14 summarized to 21 and 26 to two groups, which are alternately supplied 71 or 72 by means of a flip-flop 73 with power via a respective one of the power amplifier.

The control signals from the end position detector of the balancing device are fed via a line 74. You get through a changeover switch 75a and a timing element 76, which determines a pulse or a pulse train Duration generated to the power amplifier 77 to activate the magnetic coil 9a of the metering device 9. This triggers a dosing process with every switchover process.

In order to switch the system to the non-balancing operating mode, the mechanically coupled changeover switches 75a and 75b are brought into the position shown in dashed lines. The solenoid coils of the valves 19, 20 and 26 are thereby de-energized, so that these valves remain closed at all times. The coils of valves 15 and 16 are continuously energized to keep these valves open.

The valve groups 18, 17 and 21, 14 are alternately switched over by the flip-flop 80 via the power amplifiers 78, 79. The flip-flop 80 is controlled by a pulse generator 81 which has been switched to the active state by actuating the switch 75b. At the same time, these control pulses reach the solenoid 9a of the metering device 9 via the changeover switch 75a, the timing element 76 and the power amplifier 77, so that it continues to work synchronously with the changeover processes of the balancing unit.

In a further embodiment, the possibility is provided for the balancing on the mass of the incoming and outgoing referring to draining liquid. This is achieved in that the temperatures of the

Direction compared liquid flows are brought into agreement and thereby the influence of the temperature dependence of the density of the liquid is eliminated. An arrangement with which this is achieved is shown schematically in FIG. The dialysis solution circuit is provided with two flow heaters Wl and Hl and with three temperature sensors that measure the temperature 70, 72 and 73. The temperature sensor 72 and the Diirchlauferwärmer Hl together with an electronic controller 27 of a known type form a temperature control system 28 within a control device, which are used to adjust the temperature of the dialysis solution supplied to the dialyzer 4 to an adjustable setpoint that corresponds approximately to the human body temperature (approx . 38 ⁰ C).

bring to. It can be assumed that the temperature of the used dialysis solution coming from the dialyzer is lower than the temperature of the solution supplied to the dialyzer due to heat losses to the surroundings, so that a lower temperature is measured at the connection of the return line 3a to the balancing device with the temperature sensor 73. In order to create the same conditions for both parts la and \ b of the balancing device, the temperature measured by the temperature sensor 73 is now used as the setpoint for a temperature control system which includes the temperature sensor 71, the flow heater Hl and an electronic controller. This control system causes the temperatures 7Ί and 73 to be the same.

In another embodiment, the temperature dependency the density and the resulting influence on the balance are mathematically taken into account. at Exact volumetric balancing results in the mass-related due to the temperature deviation Accounting errors

Δπι in g / h from the formula
-Qn- (Ti-TX) β

Here Qn is the dialysis solution flow (in g / min), 73 - Ti is the temperature difference in K between the inputs of the balancing device and β is the cubic expansion coefficient of the dialysis solution (approx.

3.7-10- "K- ¹ ).

The technical implementation of the calculation process is possible in various ways. With the one indicated in Fig.5 A block diagram illustrating a preferred embodiment assumes that the

Total amount of ultra nitrate on display device 30, e.g. B. a digit display device shown shall be. The display device is controlled by a counter 31 whose input pulses each a certain unit amount (e.g. 1 g) ultra-

represent filtrate. The counter receives 32 input pulses from the removal device via an OR gate (7 in Fig. 1) as well as from the correction circuit to compensate the temperature input

rivers fed. If the extraction device has a is a volumetric pump that delivers a unit volume per working stroke, the control pulses of the Pump can be given directly to input 33 of the Oder gate. In other cases / .. B. a Interconnection with a voltage-frequency converter may be necessary.

To correct the influence of the temperature difference 7Ί - 73, the difference between the two electrical signals representing the temperatures 7Ί and 73 is first formed with the aid of a subtraction circuit 34. The difference 7Ί - 73 is multiplied by the multiplier 35 with an electrical signal corresponding to the flow rate Qd. If the machine always works with the same dialysis solution flow and an operational adjustment is not provided for this, the multiplier can be omitted and the flow rate as well as the other constants can be taken into account as a constant factor.

The signal is then fed to a voltage-frequency converter 36, which is one of the temperature differences and the pulse frequency corresponding to the other influencing variables (shown in unit quantities per unit of time) generated. These pulses arrive at the input 37 of the OR gate 32. If with both input signals of the OR gate, the pulse duration is very small compared to that between the pulses Pauses, the error that could arise from the random coincidence of two pulses can be neglected will.

The in F i g. The arrangement shown in FIG. 5 is only an example of a possible implementation. If the device z. B. for other purposes contains a microcomputer, it is very obvious to this for the present Purpose to use. Starting from the basic arrangement shown in FIG. 2, there are different Configurations of the dialysis solution circuit possible with regard to the generation of the Flow rate in the dialyzer as well as with regard to the removal of air from the dialyzer circuit.

If the balancing chambers are designed in the manner shown in FIG. 4 type shown schematically with a passive displaceable separating element in the chamber, in this case the membranes 24 and 25, is an additional one Conveyor in series with the dialyzer required, to create the flow. Any type of pump is suitable for this. But there is also the possibility the balance chambers according to the in F i g. 6 to shape the principle shown.

The balancing chamber 40 is divided into two chambers 40a by means of a movable or displaceable membrane 41 and 406 split. In one of the two chambers is a working memory in the form of a helical spring 42 is arranged, which is fixed to one with the membrane 41 and sealingly connected support element 43 is supported. In the in F i g. 6 are both of the position shown Rooms of the balance chamber 40 in equilibrium. The spring 42 is dimensioned such that it supports the support element 43 able to push up to the outer wall of the space 40a and still has a residual force

In this way, the spring creates the driving force for the transport of the liquid out of the space 40a out. The flow rate depends on the flow resistance of the connected liquid circuit and can be set to the desired value with a throttle. The room 40a has connection pieces 44a and 44b for filling and emptying. while room 406 has a connecting piece 45a and 456 is provided.

The described function of the accounting system assumes in any case that this is done in the accounting chambers The medium located can be regarded as practically imkompressibcl. It must therefore be prevented that air bubbles get into the balance chambers. On the input side, when the fresh dialysis solution is supplied, this is guaranteed without further ado, since it is necessary to degas the dialysis solution before she gets to the dialyzer. For this purpose devices with thermal or negative pressure degassing and subsequent deposition of the gas bubbles known.

On the return side from the dialyzer to the balancing device An additional air separator is generally necessary to remove air, which is particularly caused by leaks can enter the system at the dialyzer connections or by other uncontrolled routes, to remove.

7 shows a corresponding arrangement which, in addition to the functional elements already described for FIGS. 1 and 2, includes a pump 46, an air separation vessel 47 and an air separation valve 48. The air separation valve 48 is controlled by the level sensor 49. If the liquid level in the air separation vessel 47 drops so far that the level sensor responds due to the accumulated air, the air separation valve 48 in the line 3b , which opens into the drain line 3, is opened. In order to generate a positive pressure in the air separation vessel 47 by utilizing the driving force of the pump 46, the return to the balancing device is also blocked in a suitable manner when the level sensor 49 is addressed, e.g. B. by closing the valves 19 and 20 (FIG. 3), as shown in FIG. 7 is indicated schematically. The accumulated air is diverted through the air separation valve 48. The level sensor 49 can, for. B. be a reed contact, which is operated by a float provided with a magnet. The switching characteristics of the reed contact can be used to advantage

the air separation when a certain liquid level is exceeded in the air separation chamber again to end.

An example of a hemodialysis machine that combines some of the properties described above and some additional properties is shown below with reference to FIGS. 8 described, the same parts as in FIGS. 1 to 4 and 7 are provided with the same reference numerals.
The liquid circuit shown schematically in FIG. 8 contains, as an essential component, those already shown in FIG. 3 shown balancing device with the two balancing chambers 22 and 23 and the associated valves 14 to 21.
The balancing device is supplied with fresh dialysis solution under a certain pressure (approx. 0.3-1.5 bar) from the supply unit 100, which is used, among other things, for degassing and heating the dialysis solution. The water entering through the water line 50 is expanded to a lower pressure (0.1-1 bar) by a pressure reducing valve 52. The concentrate is mixed in behind the pressure reducing valve via the metering device 9 and the line 51

a concentrate container 53 is taken.

The dosing shown purely schematically in Fig.

B5 device has a housing AB, in which the membrane body C (z. B. rubber) is located. The end of the plug D is vulcanized into the membrane body and is fitted with a defined, possibly adjustable stroke.

direction of the double arrow G driven.

The check valves FF are on the other side of the diaphragm housing.

As in connection with F i g. 3 is the Actuation of the metering device 9 with the control of the balancing device in each case one work cycle or a defined number of work cycles of the metering device is triggered. The mixture is through the negative pressure generated by the pump 54 in connection with the flow resistance 55 (approx. 0.9 bar) degassed. This flow resistance can be designed either as a simple throttle or as a control valve controlled by the negative pressure.

The released air is separated by the air separator 56 and z. B. led into the drain line 57. The air separator can, as indicated, work with a float-controlled air outlet or with a level sensor that actuates a solenoid valve

From the lower connection of the air separator 56, the degassed dialysis solution reaches the balancing device via the flow heater 58. The flow heater contains an electric heater and at least one temperature sensor 59 and is used to the Warm the dialysis solution to about body temperature (38 ° C). For this purpose, temperature sensor 59 and heater 58 are in a known manner via a temperature controller

60 coupled

The balancing device is, as in connection with FIG. 3 explains, in the successive work cycles with certain portions of fresh dialysis solution, which by dps volume of the balance chambers 22 and 23 are defined, loaded. In the pauses between the charging cycles, the dialysis solution is returned to the degassing system through the overflow valve 61. the During this time, dialysis solution flows in a closed circuit, which is made up of elements 54,56,58,

61 and 55 is formed. On the suction side of the pump 54, the aforementioned high negative pressure is constantly available, which in the example described here is also used to remove the air from the dialyzer circuit to remove lying air separator 47.

A special feature of the supply unit 100 is the arrangement of the elements 54, 55, 56, 58, 61 in one closed recirculation circuit and the feeding of the dialysis solution into the connecting line between the flow resistance 55 and the overflow valve 61. The recirculation makes the degassing highly effective and the control behavior of the Flow heater reached. Another advantage is that with this arrangement the dialysis solution with a sm Pressure is available which is arbitrarily higher than the water inlet pressure at 50, and that at the same time negative pressure is available to draw air from other parts of the system. While the order of elements 55,54,56,61 is important, the Continuous heater 58 can also be inserted elsewhere in the circuit, e.g. B., just before the Flow resistance 55 or between the flow resistance and the pump 54 or between the Pump and air separator 56.

The fresh coming from the balancing device Dialysis solution passes through the analysis device 10 and 10 bypass valve 62 into the line 63, which leads to the dialyzer. The analysis device 10 is an electrical conductivity meter in the present case Combination with a temperature sensor, which on the one hand compensates for the temperature dependency serves to measure the conductivity and, on the other hand, to measure and monitor the temperature of the dialysis solution, as explained above for FIG. If the Conductivity or the temperature is outside the permissible normal range, the bypass valve 62 is automatically switched over, so that the dialysis solution no longer led to the dialyzer, but according to the dashed arrow on the outflow side of the Diaiysators is diverted. When the function is normal, the flow from the dialyzer is com Mende Dialysis rlösung via line 64 through the Blood leak detector 65 and the pressure measuring device 66 in the air separator 47. The blood leak detector and the Pressure measuring devices are known devices for monitoring the tightness of the dialyzer membrane or to measure the return pressure. The used dialysis solution is transferred from the lower part of the air separator to the balancing device via a pump 67 The delivery rate of this pump, which z. B. via a speed adjustment of the drive motor can be changed, determines the per unit of time

Amount of dialysis solution flowing through the dialyzer.

In the example shown of a hemodialysis system

The electrical signal for the reversal is advised

the valves of the bilauaiervorrichtung and for the syn-

chronological control of the metering device 9 obtained from the supply circuit of the drive motor of the pump 67. If the Membrane in the balancing chamber that is used to supply the dialyser is completely connected to the chamber wall, the power requirement increases and with it the current drawn by the pump motor increases significantly. By one inserted into the motor circuit 82 Resistance connected to the input of a threshold switch can in this way change the Switching signal can be obtained, which is sent to input 74 in FIG. 3A is placed.

The air separation chamber 47 has in the upper part a level sensor 49, for. B. with a preheated thermistor or according to another common function principle. When the liquid level in the air separation chamber is below the response level of the sensor 49 drops, the valve 48 is opened by the switching signal of the sensor 49 so that the air via the line 68 through the degassing pump 54 into the supply part 100 is sucked off. A negative pressure of z. B. -0.9 bar is used to remove the air because, depending on the set ultrafiltration rate, there is normally also a negative pressure of up to about -0.6 bar in the dialyzer.

The valve 48 is closed again when the liquid level in the air separation chamber 47 has risen sufficiently again.

To connect a Diaiysators not pre-filled with the liquid, as above with reference to the F i g. 3 and 3A, a special filling program is provided in which the balancing function is canceled, the proportional dosing function of the balancing unit in conjunction with the dosing device 9 however remains.

The filling program is switched on automatically when - due to the large amount of air coming out of the dialyzer - the air separation process exceeds a certain period of time via the valve 48, e.g. B. by closing switches 75a and 766 in 3A via a timing element which is connected to the sensor 49.

In this case, the valve 48 is closed and on Valve 69 opened to direct the air through this valve

16

to drain 57 to direct. The valve control is in the in connection with F i g. 3 and 3A changed so that fresh dialysis solution is unbalanced reaches the dialyzer and displaces the air present there into the air separation vessel 47, from where it passes over the opened valve 69 reaches the drain line 57. If by subsequent dialysis solution the fluid level has risen again in the air separation vessel. is indicated by the corresponding signal from the level sensor 49 ended the filling program and the system switched back to the normal balancing operating mode.

The removal of a precisely predeterminable amount of fluid from the dialyzer circuit and thus the measurement and / or control of the ultrafiltration takes place with the aid of the extraction device 7, which is shown in the present embodiment is designed as a volumetric diaphragm pump, each individual Pump stroke corresponds to a unit amount (1 ml) of ultrafiltrate. The extraction takes place via a line 83 from the lower part of the air separation vessel 47 to ensure that only bubble-free liquid is removed will. The exit of the ultrafiltration pump or extraction device 7 is normally about the switching valve 84 is connected to the drain line 57. With the help of the switching valve 84, however, there is also the possibility of the removed liquid in accordance with the dashed arrow via the sample line 85 to be taken separately and z. B. for control purposes in a measuring vessel.

Another special feature is that by connecting the input to the bypass line 83 and an expedient use of the switching valves 62 and 84 also samples of the fresh dialysis solution the sample line 85 can be removed to e.g. B. the composition of the dialysis solution with a external analyzer to control. A changeover switch (not shown) becomes this Purpose brought the valves 62 and 84 into the positions corresponding to the dashed arrows and the ultrafiltrate pump switched to maximum stroke frequency. The dialysis solution is then available on the sample line 85 to disposal.

A remarkable difference compared to the previously known proportional dosing devices in Incidentally, hemodialysis equipment consists in that, in the arrangement according to the invention, the concentrate and the Dialysis solution are dosed, while in the previously known devices the original components, namely water and concentrate. The arrangement according to the invention thereby offers a significant advantage in terms of chemical disinfection of the device. In between treatments chemical disinfection of the dialysis solution circuit, it is usual and appropriate to to supply a disinfectant concentrate instead of the concentrate for the preparation of the dialysis solution, which after dilution with water results in the disinfectant solution. With the proportional dosing devices that have been used up to now this means that all between the water pipe connection of the device and the metering device for the water lying parts as well this dosing device itself cannot be included in the chemical disinfection, since the addition of the concentrate downstream of the Dosiervor- tvi direction for the water takes place. In contrast, in the system used in the invention, the concentrate metering device z. B. be connected directly to the Wasscreingang of the device, so that the the entire liquid-carrying part of the device is included in the disinfection.

In addition 6 sheets of drawings

Claims (7)

& '■■ :! ! '' V I'1 claims: 1. Device for hemodialysis and for withdrawing ultrafiltrate with at least one balancing unit which consists of at least two chambers separated by a sliding element, each have a supply line and a discharge line for fresh and used dialysis fluid, with a dialyzer, which is connected to the one supply line and one discharge line, shut-off devices and conveying devices arranged in the supply lines and in the discharge lines are, with a device for degassing fresh dialysis fluid upstream of the dialyzer and a second device for degassing used dialysis fluid downstream of the Dialyzer, but upstream of the second balance chamber, with pumps in the supply lines or are arranged in the discharge lines, with a device for removing ultrafiltrate the closed circuit, the one through the balancing unit, the one supply line, the dialyzer and a discharge line is formed, as well as with a supply device for provision of Irish dialysis fluid from concentrate solution and water, characterized in that that the device (56) for degassing fresh dialysis fluid in the supply line to Balancing unit (1; 22, 23) is switched on and has a pump (54) upstream with which fresh Dialysis fluid can be supplied with a negative pressure, and the device (47) for degassing used Dialysis fluid is connected to the pump (54) via a lockable line (68). 2. Apparatus according to claim 1, characterized in that the air separation chamber (47) has a Level sensor (49) with which a switching signal can be generated when the liquid level drops is, diäs opens the valve (48) switched on in the line (68). 3. Apparatus according to claim 1 or 2, characterized in that the pump (54) is a negative pressure can be generated which is below the negative pressure generated by the ultrafiltration device (7). 4. Device according to one of claims 1-3, characterized in that upstream of the pump (54) a flow resistance (55) is switched on in the supply line for the fresh dialysis fluid. 5. Device according to one of claims 1-4, characterized in that the device for Degassing of fresh dialysis fluid has an air separator (56), the air outlet of which can be shut off and is connected to a drain line (57). 6. Apparatus according to claim 5, characterized in that that the air outlet of the air separator (56) with a float, level sensor or solenoid valve is controlled. 7. Apparatus according to claim 5 or 6, characterized in that the air separator (56) has a lateral connection for the supply and a lower connection for the discharge of the fresh dialysis fluid having. The invention relates to a device for hemodialysis and for the removal of ultrafiltrate with at least one balancing unit, which consists of at least two by one Slidable element consists of separate chambers, each with a feed line and a discharge line for Have fresh and used dialysis fluid, with a dialyzer connected to the one supply line and the one discharge line is connected, shut-off devices and conveying devices in the supply lines and are arranged in the discharge lines, with a device for degassing fresh dialysis fluid upstream of the dialyzer and a second device for degassing used dialysis fluid downstream of the dialyzer, but upstream of the second balance chamber, with pumps in the supply lines or are arranged in the discharge lines, with a device for removing ultrafiltrate the closed circuit through the balancing unit, the one feed line, the dialyzer and the a discharge line is formed, as well as with a supply device for the provision of fresh Dialysis fluid from concentrate solution and water. A device of the type mentioned is known from DE-OS 25 44 258. This device has a balancing unit, consisting of two balancing chambers for the preparation of the fresh dialysis fluid and a balance chamber for discharging the used dialysis fluid. These chambers form in connection with the lines going out therefrom, which are connected to the dialyzer, one closed circuit from which the air produced during dialysis has to be removed in order to achieve an exact Guarantee accounting. Downstream of the two chambers for the volumetric supply of water and concentrate solution is a Mixing container provided in which these two components are mixed. Thus, the freshness obtained is Dialysis fluid not yet degassed. This degassing takes place in a manner known per se in front of the dialyzer, d. H. between the mixing container and the dialyzer in a closed circuit. Like this degassing however, is not explained. A further air separation device is provided downstream of the dialyzer, in which the leaks through Place on the dialyzer or by the dialyzer itself released gas should be removed to the accounting not to bother. In addition, this air separation device is equipped with a pump for the extraction of ultrafiltrate connected, which pumps out liquid from the closed circuit, which in a corresponding manner through fluid from the blood must be replaced in a closed circuit. This pump also serves to remove excess air from the air separator. Such a balancing device initially has the disadvantage that the balancing is not carried out exactly because the supplied, balanced liquids have not yet been degassed and this degassing only takes place downstream of the balance chambers he follows. Furthermore, this is downstream of the bo balancing chambers and degassing of the fresh dialysis fluid taking place upstream of the dialyzer problematic, since the ultrafiltration pump already creates a negative pressure in the entire circuit, with which / was the degassing the fresh dialysis fluid can be carried out, but the separation of the released Gases is not done before the dialyzer, which is desirable. Because the ultrafiltration pressure is maintained in the system is also the creation of a small