METHOD OF PURGING GAS BUBBLES IN AN EXTRACORPOREAL BLOOD CIRCUIT

Abstract

The invention relates to a method of purging gas bubbles from a target zone of an extracorporeal blood circuit of a dialysis machine, wherein the target zone is flowed through by flushing liquid which enters into the target zone through an inflow and exits it again through an outflow, wherein the inflow differs from the arterial port and the outflow differs from the venous port of the extracorporeal blood circuit. The invention furthermore relates to a dialysis machine having an extracorporeal blood circuit and a control unit, with the extracorporeal blood circuit having an inflow and an outflow for flushing liquid, with the inflow differing from the arterial port and the outflow differing from the venous port of the extracorporeal blood circuit, and with the control unit being configured to carry out a method in accordance with the invention. The invention furthermore relates to a disposable for the dialysis treatment, wherein the disposable comprises an arterial line, elements of a blood pump, a dialyzer and a venous line, wherein the disposable has an interface for the inflow of flushing liquid in the arterial line and an interface for the outflow of flushing liquid in the venous line, and wherein the interface for the inflow differs from the arterial port and the interface for the outflow differs from the venous port of the hose set.

Claims

1. A method of purging gas bubbles from a target zone of an extracorporeal blood circuit, preferably of an extracorporeal blood circuit of a dialysis machine, wherein the target zone is flowed through by a flushing liquid which enters into the target zone through an inflow and exits it again through an outflow, characterized in that the inflow differs from the arterial port and the outflow differs from the venous port of the extracorporeal blood circuit.

2. A method in accordance with claim 1, characterized in that the outflow is arranged in the venous line; and/or in that the outflow is arranged downstream of all existing interfaces of the extracorporeal blood circuit.

3. A method in accordance with claim 1, characterized in that the inflow is arranged upstream or downstream of the blood pump in the arterial line.

4. A method in accordance with claim 1, characterized in that the extracorporeal blood circuit comprises an arterial clamp and/or a venous clamp, with the arterial clamp preferably being arranged between the arterial port and the inflow and with the venous clamp preferably being arranged between the outflow and the venous port.

5. A method in accordance with claim 1, characterized in that the inflow and/or the outflow can be closed using a clamp or is/are connected to the extracorporeal blood circuit using a three-way valve.

6. A method in accordance with claim 1, characterized in that the flow rate and/or the pressure of the flushing liquid in the extracorporeal blood circuit is/are inconstant at least at times during the flushing process; and/or in that the flow rate of the flushing liquid in the extracorporeal blood circuit lies outside a range of possible flow rates at least at times during the flushing process, which range is used during the treatment for the blood.

7. A method in accordance with claim 1, characterized in that the method is carried out during a treatment interruption, in particular during a pressure holding test.

8. A method in accordance with claim 1, characterized in that the method comprises the following steps: (a) Closing an arterial clamp and opening the inflow; (b) Conveying a first volume of flushing liquid into the target zone, with the first volume substantially corresponding to the volume of the target zone; (c) Closing a venous clamp and opening the outflow; (d) Flushing through of the target zone with the flushing liquid; (e) Opening the arterial clamp and closing the inflow; (f) Draining of a second volume of flushing liquid from the target zone, with the second volume substantially corresponding to the volume of the target zone; and (g) Closing the outflow and opening the venous clamp.

9. A method in accordance with claim 1, characterized in that the method comprises the following steps: (a′) Stopping the blood pump and opening the inflow; (b′) Conveying a first volume of flushing liquid into the target zone, with the first volume substantially corresponding to the volume of the target zone; (c′) Closing a venous clamp and opening the outflow; (d′) Flushing through of the target zone with the flushing liquid; (e′) Closing the inflow and starting the blood pump; (f′) Draining of a second volume of flushing liquid from the target zone, with the second volume substantially corresponding to the volume of the target zone; and (g′) Closing the outflow and opening the venous clamp.

10. An extracorporeal blood treatment unit, preferably a dialysis machine, having an extracorporeal blood circuit and a control unit, characterized in that the extracorporeal blood circuit has an inflow and an outflow for flushing liquid, with the inflow differing from the arterial port and the outflow differing from the venous port of the extracorporeal blood circuit, and with the control unit being configured to carry out a method in accordance with one of the preceding claims.

11. An extracorporeal blood treatment unit in accordance with claim 10, characterized in that the extracorporeal blood treatment unit comprises a line system for flushing liquid which is connected to the extracorporeal blood circuit so that flushing liquid can enter into the target zone through an inflow and can leave it again through an outflow, with the line system preferably comprising a flushing pump which is arranged upstream of the inflow in the line system.

12. An extracorporeal blood treatment unit in accordance with claim 10, characterized in that the control unit is configured so that it interrupts the treatment before the carrying out of the process and/or so that it triggers the process during an interruption of the treatment and/or so that it automatically continues the treatment after the carrying out of the process.

13. An extracorporeal blood treatment unit in accordance with claim 10, characterized in that the control unit is configured so that it takes account of the quantity of flushing liquid supplied by the process and/or of the blood drained off by the process in the determination of treatment-specific parameters, in particular in the determination of the ultrafiltration volume.

14. An extracorporeal blood treatment unit in accordance with claim 10, characterized in that the control unit is configured so that the conveying speed for blood is slowly increased after the end of the process.

15. A disposable for the extracorporeal blood treatment, in particular for the dialysis treatment, wherein the disposable comprises an arterial line, elements of a blood pump, a blood treatment unit, in particular a dialyzer, and a venous line, characterized in that the disposable in the arterial line has an interface for the inflow of flushing liquid and in the venous line has an interface for the outflow of flushing liquid, with the interface for the inflow differing from the arterial port and the interface for the outflow differing from the venous port of the hose set.

16. A disposable in accordance with claim 15, characterized in that the interface for the outflow of flushing liquid is arranged downstream of all other interfaces of the disposable.

17. A disposable in accordance with claim 15, characterized in that the interface for the inflow of flushing liquid is arranged upstream or downstream of the pump segment.

18. A disposable in accordance with claim 15, characterized in that the extracorporeal blood circuit comprises an arterial clamp and/or a venous clamp, with the elements of the arterial clamp preferably being arranged between the arterial port and the interface for the inflow of flushing liquid and with the venous clamp preferably being arranged between the interface for the outflow of flushing liquid and the venous port.

19. A disposable in accordance with claim 15, characterized in that the interface for the inflow and/or outflow of flushing liquid can be closed using a clamp or is connected to the arterial line or to the venous line using a three-way valve.

Description

[0046] Further details and advantages result from the Figures and embodiments described in the following. There are shown in the Figures:

[0047] FIG. 1: a schematic representation of fluid circuits of a dialysis machine from the prior art;

[0048] FIG. 2: a schematic representation of fluid circuits in accordance with a dialysis machine in accordance with a first embodiment of the invention; and

[0049] FIG. 3: a schematic representation of fluid circuits in accordance with a dialysis machine in accordance with a second embodiment of the invention.

[0050] FIG. 1 shows fluid circuits of a dialysis machine from the prior art. The dialysis machine has a dialyzer 1 which has a blood chamber 2 and a dialysis liquid chamber 3 which are separated from one another by a membrane 4. The blood chamber 2 is a component of an extracorporeal blood circuit 5. The dialysis liquid chamber 3 is a component of a dialysis liquid circuit 6.

[0051] The blood circuit 5 has an arterial port 7 which is connected to the blood chamber 2 via an arterial line 8. A blood pump 9 is seated in the arterial line 8. The venous end of the blood chamber 2 is connected to the venous port 11 by means of the venous line 10. A drip chamber 12 is located in the venous line.

[0052] The arterial and venous ports are not connected to the patient during the filling and flushing (priming) of the blood circuit. The arterial port is connected to a flushing liquid reservoir 13 and the venous port represents an outflow for flushing liquid. After the filling of the blood circuit with flushing liquid, a flushing phase takes place, with flushing liquid exiting the venous port.

[0053] A flushing of the blood circuit can thus not take place while a patient is connected to the circuit since the arterial port and the venous port are not available for the flushing.

[0054] FIG. 2 shows fluid circuits of a dialysis machine in accordance with a first embodiment of the invention. Components already known from FIG. 1 are provided with corresponding reference numerals.

[0055] Unlike the prior art, the extracorporeal blood circuit 5 furthermore here has a separate inflow 14 and a separate outflow 15 for flushing liquid. It is thus made possible that the flushing liquid cannot leave a target zone for a flushing disposed between the inflow and the outflow via the venous port 11, but rather via the separate outflow 15. Flushing liquid can furthermore enter into the circuit via a separate inflow.

[0056] The outflow 15 is arranged in the venous line 10 downstream of all existing interfaces of the extracorporeal blood circuit. A postdilution port 16 is shown as an interface by way of example in the Figure. An air bubble detector 17 is located between the outflow and the venous port. The inflow is arranged upstream of the blood pump in the arterial line and represents a separate access. As a further interface, the blood circuit comprises a predilution port 18 with an integrated heparin feed line 19. The extracorporeal blood circuit furthermore comprises an arterial clamp 20 and a venous clamp 21. The arterial clamp is arranged between the arterial port 7 and the inflow 14. The venous clamp is arranged between the outflow 15 and the venous port 11. Both the inflow 14 and the outflow 15 are connected to the extracorporeal blood circuit 15 by means of a three-way valve.

[0057] A higher flexibility with respect to the onset time of the method for purging gas bubbles can be achieved by the arrangement of the additional outflow and inflow as well as by the further components of the dialyzer in accordance with the invention. For example, a purging of gas bubbles is possible during a treatment break, for example during a pressure holding test. A flushing can, for example, have the following steps before or during the treatment: [0058] (a) Closing the arterial clamp and opening the inflow; [0059] (b) Conveying a first volume of flushing liquid into the target zone disposed between the inflow and outflow, with the first volume substantially corresponding to the volume of the target zone; [0060] (c) Closing the venous clamp and opening the outflow; [0061] (d) Flushing through of the target zone with the flushing liquid; [0062] (e) Opening the arterial clamp and closing the inflow; [0063] (f) Draining of a second volume of flushing liquid from the target zone, with the second volume substantially corresponding to the volume of the target zone; and [0064] (g) Closing the outflow and opening the venous clamp.

[0065] The conveying of the flushing liquid in steps (b), (d) and (f) takes place using the blood pump. The conveying of the flushing liquid into the system takes place using a separate flushing pump which is not shown in the Figures and which is arranged in the supply system for the flushing liquid at the machine side.

[0066] Provided that, as in the shown embodiment, the access of the substituate flow is disposed before the blood pump, the flushing out of the microbubbles can be carried out in that the substituate pump and the blood pump run at the same conveying rate. Since the substituate is then completely conveyed on at the same conveying rate by the blood pump, blood can no longer be drawn into the hose system so that an arterial clamp can also be dispensed with. Alternatively, an arterial clamp allows the temporary clamping closed of the blood stream and allows large freedom with respect to a variation of the conveying rates of the blood pump and the substituate pump for generating pressure pulses and volume flow pulses which can be suitable to detach and take along bubbles and microbubbles.

[0067] FIG. 3 shows fluid circuits of a dialysis machine in accordance with a further embodiment of the invention. Components already known from FIGS. 1 and 2 are provided with corresponding reference numerals.

[0068] This embodiment differs from the embodiment shown in FIG. 1 in that the inflow 14 is arranged downstream of the blood pump in the arterial line and corresponds to the predilution port 18 with an integrated heparin feed line 19. An arterial clamp has been dispensed with. For example, a flushing can have the following steps before or during the treatment using this embodiment of the invention: [0069] (a′) Stopping the blood pump and opening the inflow; [0070] (b′) Conveying a first volume of flushing liquid into the target zone disposed between the inflow and outflow, with the first volume substantially corresponding to the volume of the target zone; [0071] (c′) Closing the venous clamp and opening the outflow; [0072] (d′) Flushing through of the target zone with the flushing liquid; [0073] (e′) Closing the inflow and starting the blood pump; [0074] (f′) Draining of a second volume of flushing liquid from the target zone, with the second volume substantially corresponding to the volume of the target zone; and [0075] (g′) Closing the outflow and opening the venous clamp.

[0076] The conveying of the flushing liquid in steps (b′) and (d′) takes place using a separate flushing pump which is not shown in the Figures and which is arranged in the supply system for the flushing liquid at the machine side. The conveying of the flushing liquid in step (f′) preferably takes place using the blood pump 9.

[0077] Provided that a purging of the target zone takes place using a dialysis machine in accordance with the invention during the carrying out of a pressure holding test in the dialysis liquid circuit, there are two possibilities of process management in both embodiments shown, namely a temporal decoupling and a spatial decoupling.

[0078] Temporal decoupling means that the flushing is already initiated before the direct start of the pressure holding test and substitution liquid is flushed into the target zone as the flushing liquid. Spatial decoupling means that a further vessel is used, for example a bag for the buffering of substituate.

[0079] During the temporal decoupling, the blood flow in the extracorporeal blood circuit is stopped and is replaced with an addition of the flushing solution into the arterial line. The flushing solution is filled in with a still running blood pump for so long until the boundary layer of substituate/blood close to the body can be detected approximately at the level of the venous chamber, for example by an optical detector or color sensor. The dialysis liquid circuit is then stopped for the pressure holding test. The venous clamp is then closed and the outflow opened. The target zone is flushed using a method in accordance with the invention during the pressure holding test. After the pressure holding test, the extracorporeal circuit is coupled again; an outlet valve close to a vein is opened until the boundary layer blood/substituate now provided with the opposite sign is detected. The outflowing substituate charged with microbubbles is discarded. The outlet valve is now closed and the blood purification is continued. In the spatial decoupling, a further vessel is used for buffering substituate solution and the blood-side system is then fed from this during the pressure holding test. The process management otherwise takes place as with the temporal decoupling.

[0080] In both of the embodiments shown, an adaptation of the pump rate to an ideal speed can take place during the flushing using a dialysis machine in accordance with the invention.

[0081] Such an adaptation can take place against the background that it has been observed that a high entry of microbubbles into the patient in particular takes place in the first minutes of the treatment. At the start, the mean microbubble flow can be an order of magnitude higher than during the remaining treatment. In addition, there is a number of air collections in the extracorporeal circuit which can serve as a source and reservoir for later microbubble injections (blood pump hose, heparin injection syringes and other injection syringes, supply lines (e.g. heparin hose and other drain lines)). The blood pump rate or flushing pump rate can thus, for example, be operated during the flushing such that the microbubbles can be removed more easily. The partly stationary microbubbles should e.g. be detached by means of a repeated stop and go of the pump and a high pump speed. Flow bursts and pressure bursts attack air collections and microbubble reservoirs and reduce them. These bursts can be achieved e.g. by brief maximum pump rates, blocking and releasing a venous clamp and the like. The detached microbubbles are removed from the extracorporeal circuit by means of the outflow in the venous line.

[0082] Furthermore, such an adaptation can take place against the background that it has been observed that the fast start-up of the blood pump can have the consequence of an intense increase of the number of microbubbles and that in particular a pressure holding test, in which the dialysis liquid is no longer refreshed and the blood in the dialyzer capillaries is no longer rinsed around with fresh, degased dialysis liquid, can have the consequence of an intense increase of the number of microbubbles. The blood pump can therefore optionally ramp up slowly after the flushing, e.g. in a ramp at no more than 200 ml/min.sup.2, which means that a desired rate of, for example, 400 ml/min is only reached after 2 minutes after a blood pump stop. In the case of a pressure holding test, the blood pump rate can be lowered in good time before the test, the conveying rate of the blood pump and substitution pump can remain at a minimum during the flushing and the pressure holding test and both rates can subsequently ramp up again slowly to their desired value.

[0083] It can be stated in summary that the invention makes it possible to flush a target zone of the extracorporeal blood circuit at any desired time, for example during a pressure holding test, and thus to avoid the formation of microbubbles. The flushing liquid can be discarded via the separate outflow.