Method and apparatus for ultrafiltration during hemodialysis.

p0001The invention relates to a method for hemodiafiltration wherein the dialysis liquid is passed through a device connected to the dialyzer provided with shut-off valves and balancing chambers having balancing device and the ultrafiltrate is removed in a precisely predetermined amount. The invention relates to a device for performing the method.

p0002From DE-PS 28 38 414 a device is known, comprising a balancing device, which consists of two separate chambers by a displaceable member having a respective feed line for fresh and one discharge pipe connected to an outlet for used dialysis fluid. In the feed and discharge valves are arranged, which are driven and switched by a control unit. For conveying the used dialysis fluid in the dialysis fluid between dialyzer and balance means a pump is located. Furthermore, this known device provides in the supply line to the dialyzer a dialyzer and in the removal of the dialyzer before an air separator.

p0003This device is operated such that fresh dialysis fluid is supplied from a dialysis the two balancing chambers alternately by appropriate switching of the stop valves in the supply lines. Simultaneously Fresh dialysis fluid is supplied from a pre-filled space of the other balancing chamber of the dialyzer, where the also flowing through the dialyzer blood the desired toxins are removed by diffusion. The power consumed by this diffusion dialysis fluid is then pumped into the second chamber of the same balance chamber, from which the used dialysis fluid is then directed into the outlet.

p0004The air trapped between the balance sheet means and the dialyzer portion of the liquid circuit behaves like a closed, constant volume system. In order to remove from this system liquid, a removal device is provided, which is connected to a drain.

p0005The means of the removal device from the system derived quantity of liquid must be due to the aforementioned characteristics of the balancing device is replaced by an equal amount of liquid that passes from the blood side to the dialysate side of the dialyzer. Thus the deduced by means of the removal device quantity of liquid consistent with the passing through the membrane of the dialyser liquid amount, the ultrafiltrate, match. The removal device having a substantially ultrafiltrate pump is configured such that a control of the ultrafiltration is possible.

p0006On the accuracy of the balancing device and the removal device high demands are made. In a hemodialysis typically about 200 l dialysis solution are passed through the dialyzer. The ultrafiltrate is typically about 2 - 3 l and should be up to a deviation in the order of 0.1 to 0.2 l estimated. The accounting error caused in the balancing device may therefore the order of 1 per thousand possible not exceed. To revoke a precisely predictable amount ultrafiltrate the dialysis fluid with the required precision, the removal device is equipped with a volumetric diaphragm pump, each individual pump stroke a unit amount corresponding ultrafiltrate. The removal takes place via a line from the lower part of which is arranged in Dialysatorkreislauf air separator to ensure that only bubble-free liquid is discharged. The output of the ultrafiltration pump or the removal device is connected via a switching valve with the drain line.

p0007Although this known device functions accurately and reliably, but there is a need to simplify This equipment technically, ie in particular to reduce the number of active components and calibration procedures and safety checks that must be carried out from time to time to save. These calibration processes and controls relating to the removal device for the ultrafiltrate.

p0008The object of the invention is a method by which a predictable ultrafiltration can be carried out more easily without additional ultrafiltrate pump. It is also an object of the invention to provide an apparatus for performing this method.

p0009This object is solved by the characterizing part of claim 1 and the characterizing part of claim 8.

p0010Whereas previously the ultrafiltrate was removed via a separate removal device in the dialysis fluid between the dialyzer and balancing device, the ultrafiltrate is first performed before discharge from the Dialysatorkreislauf on the balancing device according to the invention. In this way, the entire removal device for the ultrafiltrate can be saved. then the ultrafiltrate, like the spent dialysis fluid supplied to the outlet of the balancing device. In addition to saving the ultrafiltrate this method offers the advantage that the filling volume of the balancing chambers can be used to determine the amount of ultrafiltrate. Since the filling volume of a balancing chamber usually comprises 30 ml, can by repeated periodically filling the balance chamber with ultrafiltrate desired ultrafiltrate, the 2 - is 3 liters, determined in an exact way and are removed from the dialysis fluid path.

p0011In a first embodiment, the shut-off valves in the inlet and outlet lines of the balancing chambers are initially connected so that a balance chamber is completely filled completely with fresh dialysis fluid and the other balancing chamber with spent dialysis fluid to perform the ultrafiltration. Then the dialysis fluid path between the balancing device and the dialyzer is interrupted. This is expediently carried out by means of the so-called dialyser. After this dialyzer has been closed, spent dialysis fluid is pumped from the dialyzer by means of dialysis fluid pump continues to give a relatively short time due to the interrupted inflow of fresh dialysis fluid in the dialyzer adjusts a vacuum. This is the blood fluid, the so-called. Ultrafiltrate withdrawn, which is now pumped from the dialysis fluid pump in the area of ​​the balancing chamber, the second chamber is filled with fresh dialysis. Since the displaced fresh dialysis can not be supplied to the dialyzer by the interruption of the dialysis solution, is deflected by a suitable circuit of the inlet and discharge valves of the balancing chambers the fresh dialysis fluid into the empty space of the other balancing chamber, at the same time present in this chamber used dialysis whereby the outlet is conveyed. After the first balance chamber has been completely filled with ultrafiltrate, the first passage of the ultrafiltration is stopped and the inlet and discharge valves of the balancing chambers are switched back on Hämodialysebetrieb. By interrupting the hemodialysis can be inserted in this manner in each case a Ultrafiltratzyklus.

p0012This method, which causes the non-uniform removal of the ultrafiltrate can be improved to the effect according to a further embodiment that the ultrafiltrate is removed continuously. For this purpose, the dialysis fluid prior to performing hemodialysis and ultrafiltration is fed such an amount of air that corresponds to the filling volume of the balancing installation or a multiple. The desired amount of air is introduced into the normally arranged between the dialyzer and the balancing device in the dialysis air separator. Here, the dialysis fluid path is also interrupted until the desired amount of air is in the air separator.

p0013The air supply can be carried out in two ways. According to a preferred embodiment, an air pump is connected to the air separator, which by closing the dialyser pumps the desired amount of air into the air separator after interruption of the Dialysierflüssigkeitswegs between the balancing device and the dialyzer. Here, the dialysis fluid pump also remains in operation. By suitable adjustment of the feed rates of the two pumps, a pressure increase is avoided in the dialysate. In air separator two spaced sensors or an analog level meters are arranged such that the two sensors and the minimum and maximum position of the level sensor include about the filling volume of a balancing chamber. During this process, so no liquid is extracted from the blood, but the closed system controlled partially filled with air. This process requires only a few seconds. Then the valves are switched back to the dialysis mode and the air pump now starts to work to remove the previously pumped into the dialysis fluid air out of the air separator, whereby an ultrafiltration of liquid is caused from the blood in the reverse direction. In the event that the air separator during hemodialysis should accumulate additional air, the air pump remains in operation until the upper sensor detects fluid.

p0014According to another embodiment is also possible, instead of pumping with the aid of an air pump by means of the dialysis solution pump, which is disposed between the air separator and the balancing device, the air in the dialysis fluid path. For this purpose, the dialysis fluid path is interrupted between the outlet of the dialyzer and the air separator via a further valve to optionally prevent suction consumed dialysis. When the dialysis solution pump continues to be operated in this case, is also sucked through the air trap air in the air separator. To accelerate the suction the pump power of the dialysis fluid pump can be briefly increased. For this purpose, the dialyzing fluid from the control unit is switched accordingly. The determination of the amount of air is then also on the two arranged in the air trap sensors or via the analog level meter. Thereafter, the dialysis fluid path is opened again and the valves connected to dialysis operation. Also in this case, then the previously drawn quantity of air is again withdrawn from the dialysis fluid during dialysis by means of the air pump connected to the air separator. Thereby, the liquid level rises in the air separator again, and after both sensors detect liquid ultrafiltration has been completed, one of the air volume corresponding ultrafiltrate was recovered. Thereafter, the dialysis fluid path is refilled with air and the process starts anew. In this way it is possible to continuously withdraw ultrafiltrate during dialysis.

p0015The withdrawal of the desired amount of ultrafiltrate can be distributed by appropriate control of the air pump to any number of filling cycles of the balancing chambers. By appropriate selection of the chamber volume of the air separator that may include a multiple of the filling volume of a balancing chamber, so that in an extreme case, if the volume of the air separator corresponds to two to three liters, it must be filled with air only once.

p0016In the continuous withdrawal of ultrafiltrate during dialysis is the amount of liquid which leaves the dialyser to the fraction of the ultrafiltrate is increased over the amount that is supplied in the fresh dialysis fluid to the dialyzer. Because of this additional interest will be accumulated by the withdrawal of the air in the air separator, changes over the known dialysis procedures on the Functioning of the balance chambers nothing. When sucking the air in the air separator the used dialysis fluid is pumped into the empty space of the balancing chamber, which is filled with fresh dialysis fluid, at the same time this Fresh dialysis fluid is forced into the other balancing chamber, where again the used dialysis fluid into the outlet is displaced. This is achieved by appropriate control of the inlet and discharge valves.

p0017The inventive device has no extraction device and thus no ultrafiltrate. The output of the dialyzer is in this case directly connected to the air separator, which is in turn connected via the dialysis fluid pump with the balancing device. According to the invention, the controller for controlling the inlet and discharge valves of the balancing device and the dialyser and possibly the additional shut-off valve between the dialyzer and air separator is designed so that the ultrafiltrate can be guided via a respective chamber of the balancing device to the outlet in the amount predetermined. Here, the shut-off valves are controlled such that the discharged ultrafiltrate each corresponding to a filling volume of a balancing chamber or multiples.

p0018According to a first embodiment, the controller is configured such that it includes between two hemodialysis cycles the dialyzer and the shut-off valves of the balancing device controls such that the ultrafiltrate can be conveyed in one of the two spaces one of the two balancing chambers by means of the dialysis solution pump, while in the other space of these is redirected balance chamber found fresh dialysis in the other balancing chamber. This means that the valves alternately between the ultrafiltration and hemodialysis mode switch back and forth. Under the hemodialysis is understood that the valves are closed in the feed, for example, the two respective right spaces of the balancing chambers and valves of the discharge lines of the two respective left spaces of the balancing chambers, while the valves are closed in the feed and discharge of the remaining rooms.

p0019During the transition to the ultrafiltration all valves of the two balancing chambers are switched, while in the other balancing chamber only the valves of the left space are switched and the right space are maintained.

p0020According to a further embodiment the control unit is additionally designed to control the air pump and / or the dialysing fluid pump. The switch position of the valves in hemodialysis mode corresponds to the embodiment described in the above. After a Hämodialysezyklus wherein also simultaneously the ultrafiltrate is removed, the valves in the ultrafiltration mode described above are connected, the now however serves to pump air into the dialysis fluid. For this purpose, the control unit controls not only the shut-off valves but also the air pump and the dialysis solution pump, and optionally also the further shut-off valve in the dialysis fluid path between the dialyzer and the air separator.

p0021To perform a continuous ultrafiltration, the air separator is formed loaded and vented. In a particular embodiment, the air separator is equipped with a bidirectionally operating air pump in pumping the appropriate amount of air into the air separator before ultrafiltration and this amount of air pumped out again from the air separator during ultrafiltration. So the corresponding volume of air can be determined exactly, two sensors are arranged at a distance, that they isolate the filling volume of a balancing chamber or a multiple thereof, the air separator. It is also possible to incorporate an analog operating level meter instead of the two sensors, the distance between maximum and minimum position also corresponds to a capacity or a multiple of the filling volume of a balancing chamber.

p0022In the dialysis fluid is disposed according to another embodiment except the dialyzer between the outlet of the dialyzer and the inlet of the air separator a further valve.

p0023Exemplary embodiments of the invention are explained in detail with reference to the drawing.

p0024Show it :<ul><li>FIG. 1 a, b, simplified schematic diagrams of Dialysierflüssigkeitswegs with a balancing device according to a first embodiment;</li><li>2 shows also a simplified schematic diagram of the Dialysierflüssigkeitswegs according to another embodiment;</li><li>3 shows also a simplified schematic diagram of the Dialysierflüssigkeitswegs according to another embodiment.</li></ul>

p0025In Fig. 1a the dialysis fluid path is shown schematically. The most important component of this arrangement is the balancing device 1. It comprises two interconnected chambers 22 and 23, each chamber 22 and 23, divided into two rooms 22a, 22b and 23a and 23b by a movable member in the form of a membrane 24 or 25 is. This balance chambers of a dialysis 10, which is provided with a pump, and a metering device 9 with fresh dialysis fluid through the line 2 supplied. In the example shown here, the space 22a and the space 23a is connected to this supply line 2, being arranged to shut off in each case a shut-off valve 18 and a check valve 21 in this supply line 2nd These spaces 22a, 23a of the two balancing chambers 22 and 23 are connected at their outlet side via further cut-off valves 14 and 17 with the Dialysatorzuleitungszweig 6, leading to the dialyzer. 4 To this branch feed line 6, a dialyzer 30 is turned on. The output of the dialyzer 4 is about Dialysatorableitungszweig 13, an air separator 50 and a Dialysierflüssigkeitsdruckmeßeinrichtung 45 and a device connected to the air separator 50 dialysis fluid pump 40 in turn connected to the balancing device. 1 The Dialysierflüssigkeitsableitungszweig 27 between the dialysis fluid pump 14 and the balancing device 1 is divided into two line paths that lead to the spaces 22b and 23b of the balancing chambers 22 and 23rd In both of these conduction paths are shut-off valves 19 and 20 arranged in front of the balancing chambers. The spaces 22b and 23b are connected via stop valves 15 and 16 with the flow line 3 which leads to the outlet fifth

p0026The valves 14-21 and 30 are controlled by a control device 55th For this purpose, the control device outputs a to h on which with the valves 14 - 21 are connected via the electric lines a 'to h'.

p0027In Fig. 1a, the valves 14, 16, 17 and 19 dark (ie, open) and the valves 15, 18, 20, 21 and the dialyzer 30 bright (ie closed) are shown. This shift situation (so-called. Ultrafiltration mode) corresponds to the first embodiment of the method, in which the space 22a is completely filled with fresh dialysis fluid and the space 23b completely with spent dialysis fluid. Now, when the dialysis solution pump 40 is in the closed dialyzer 30 in operation, is formed in the dialyzer 4, a negative pressure, whereby the ultrafiltrate Blutkreisweg is withdrawn (not shown). This ultrafiltrate is fed via line 27 and the open valve 19 of the balance chamber 22 and there fed to the space 22b, while simultaneously fresh dialysis fluid from the space 22a via the open valve 14 and the open valve 17 is supplied to the space 23a of the balance chamber 23rd Here, in the chamber 23b spent dialysis fluid is supplied via the valve 16 the flow fifth After the space is filled completely 22b of the balance chamber 22 with the ultrafiltrate, the valves 14 to 21 and 30 controlled by the controller 55 such that the valves 14, 16, 19 and 21 are closed and the valves 15, 17, 18, 20 and 30 are opened (so-called. hemodialysis mode). This switching position is shown in Fig. 1b. In this valve position, then the hemodialysis is carried out, as is known from DE-PS 28 38 414th In the subsequent dialysis cycle then the space 23b with spent and the space 22a is filled with fresh dialysis.

p0028In the event that in the dialysis fluid in the air separator separates 50 air drops of liquid level, so that a switch located on the air separator 50 air / liquid sensor detects 51 air. In this case the pump is put in operation 41, which then pumps off the excess air until it is deactivated on a signal from the sensor 51 down.

p0029In FIG. 2, another embodiment is illustrated. In this case, the air separator 50 is equipped with two sensors, that is the upper sensor 51 and bottom sensor 52, which are connected via the electric lines i 'and j' to the inputs i and j to the control device 55th Instead of an analog operating level sensor or instead of two sensors 51, 52, a single sensor 51 can be used in combination with a volumetrically operating pump. Since about the dialysis fluid 45 pressure in the system is known, the pump 41 can be controlled by the control unit 55 so that, taking account of the general gas equation a predictable amount of dialysis fluid is displaced from the air separator 50th For this purpose, the dialysis fluid 45 is connected via the electric line 1 'to the input 1 of the control unit 55th

p0030The valves 14, 16, 17, 19 and 15, 18, 20, 21 are shown as dark or bright, which is also intended to indicate that these valves have been switched open or closed by the controller 55. The switch position of the valves 14-21 in this case corresponds to that of FIG. 1A.

p0031Before the start of the ultrafiltration, according to the embodiment shown here, first on the operating as a bi-directional pump 41 which is also connected to the control unit 55 delivering air into the air separator 50, the pumping rate is controlled so that the pressure at the dialysis fluid 45 does not increase , The pump 41 promotes so much air is detected by air at the lower sensor 52nd The sensors 51 and 52 are positioned so that the volume lying between them corresponds approximately to the balance chamber volume.

p0032The dialysis fluid is thereby displaced pumped by the pump 40, the pumping rate is matched to the air pump 41, via the valve 19 into the space 22b of the balance chamber 22nd At a predetermined speed, either the pump 40 or the pump 41, the other pump can be controlled so that the measured via the dialysis fluid 45 Dialysierflüssigkeitsdruck remains constant.

p0033At the same time located in the space 22a of the balance chamber 22 fresh dialysis fluid via the valve 14 and the open valve 17 also is pumped into the space 23a of the second balance chamber 23rd

p0034After the desired amount of air has been pumped into the air separator 50, the dialyser 30 are opened and the valves 14 to 21 from the control unit 55 in the dialysis mode - is shown as mentioned above and in Figure 1b, -. And the air pump 41 is switched into the venting operation , The present in the air separator 50 air, the air pump 41 pumps over a desired period out of the air separator, until the upper sensor 51 again detects liquid and deactivates the air pump 41st In this way a continuous ultrafiltration during hemodialysis is possible.

p0035In FIG. 3, another embodiment is illustrated. In this example, an additional valve 32 is in the Dialysatorableitungsweg 13, which connects the output 7 of the dialyser to the air separator 50, shown connected via the line k 'k to the input of the control unit 55th is Before the ultrafiltration to prevent aspiration of used dialysis fluid, this valve 32 is closed by the control unit 55, while the dialysis fluid pump continues to run 40th Simultaneously, the air pump 41 is turned off and the vent valve 42 of the air separator 50 which is also connected to the control unit 55 is opened. Accordingly, valve 42 is shown in dark. This valve 42 remains open until the lower sensor detects 52 air. The switch position of the valves 14 to 21 is the same as that which is shown in FIG. 2. In order to suck the air as quickly as possible, the pumping rate of pump 40 can be increased by control of the control unit 55 momentarily.

p0036When the desired amount of air is in the air separator 50, the valve 42 is closed and valves 30 and 32 opened. At the same time the valves are switched 14 to 21 in the dialysis mode (s. Fig. 1b). At the same time in this embodiment, the one-way pump 41 is taken from the control unit 55 in operation, the amount of air contained in the air separator 50 pumps off again for a predetermined period of time. This continues until the upper sensor 51 again detects liquid. During this period will be withdrawn by the resulting vacuum ultrafiltrate the bloodstream. This arrangement is particularly precisely controlled when instead of the sensors 51 and 52, an analogous working level sensor is used. The switching of the valves during hemodialysis and ultrafiltration then corresponds to the switching position already described with reference to Figure 1a.