METHOD OF PURGING GAS BUBBLES IN AN EXTRACORPOREAL BLOOD CIRCUIT

Abstract

The invention relates to a method of purging gas bubbles from at least one target zone of an extracorporeal blood circuit, preferably of an extracorporeal blood circuit of a dialysis machine, with a flushing liquid, wherein 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 wherein the flow rate of the flushing liquid in the extracorporeal blood circuit lies above a range of possible flow rates at least at times during the flushing process, which range is used during the treatment for the blood. The invention furthermore relates to an extracorporeal blood treatment unit having an extracorporeal blood circuit, a pump and a control unit, with the control unit being configured to carry out a flushing process in accordance with the invention. The invention furthermore relates to an extracorporeal blood treatment unit having an extracorporeal blood circuit, a pump and a control unit, with the control unit being configured such that the conveying speed for blood is slowly increased after a standstill of the pump or after an operation of the pump at throttled speed.

Claims

1. A method of purging gas bubbles from at least one target zone of an extracorporeal blood circuit, preferably of an extracorporeal blood circuit of a dialysis machine, with a flushing liquid, characterized in that the flow rate and/or the pressure of the flushing liquid in the extracorporeal blood circuit is 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.

2. A method in accordance with claim 1, characterized in that the flushing liquid is conveyed through the target zone using a pump; and in that the variation of the flow rate and/or of the pressure takes/take place by a change in the conveying rate of the pump.

3. A method in accordance with claim 1, characterized in that the change in the conveying rate takes place by a swathing on and switching off of the pump or by a throttling and increasing of the pump speed.

4. A method in accordance with claim 1, characterized in that the pump is a blood pump arranged in the extracorporeal blood circuit or a flushing pump arranged outside the extracorporeal blood circuit.

5. A method in accordance with claim 1, characterized in that the extracorporeal blood circuit has at least one clamp or a valve; and in that the variation of the flow rate and/or of the pressure takes/take place by a control of the clamp.

6. A method in accordance with claim 1, characterized in that the flow rate and/or the pressure of the flushing liquid is/are increased and reduced in bursts.

7. A method in accordance with claim 1, characterized in that the bursts show a continuous or abrupt build-up and a continuous or abrupt drop in the flow rate and/or in the pressure of the flushing liquid.

8. A method in accordance with claim 1, characterized in that the amplitude of the bursts is selected such that the flow rate and/or the pressure of the flushing liquid varies between valleys and peaks by at least a factor of 1.3, a factor of 1.5 or a factor of 2.

9. A method in accordance with claim 1, characterized in that the flow rate of the flushing liquid in the extracorporeal blood circuit during the flushing process is larger than 550 ml/min or larger than 700 ml/min at least at times.

10. An extracorporeal blood treatment unit, preferably a dialysis machine, having an extracorporeal blood circuit, a pump and a control unit, characterized in that the control unit is configured to carry out a flushing method in accordance with one of the preceding claims.

11. An extracorporeal blood treatment unit, preferably a dialysis machine, having an extracorporeal blood circuit, a pump and a control unit, characterized in that the control unit is configured such that the conveying speed for blood is slowly increased during the extracorporeal blood treatment after a standstill of the pump or after an operation of the pump at a throttled speed.

12. An extracorporeal blood treatment unit in accordance with claim 11, characterized in that the control unit is configured such that the conveying speed for blood is slowly increased at the start of the treatment.

13. An extracorporeal blood treatment unit in accordance with claim 11, characterized in that the control unit is configured such that the conveying speed for blood is slowly increased after a treatment interruption.

14. An extracorporeal blood treatment unit in accordance with claim 11, characterized in that the conveying speed is increased on a ramp having an increase of no more than 300 ml/min.sup.2 or 200 ml/min.sup.2 or 150 ml/min.sup.2.

15. An extracorporeal blood treatment unit in accordance with claim 11, characterized in that the control unit is configured to carry out a flushing method in accordance with one of the claims 1 to 9.

Description

[0030] Further details and advantages result from the FIGURE described in the following and from the embodiments.

[0031] The only FIGURE shows a schematic representation of fluid circuits of a dialysis machine in accordance with the invention.

[0032] The dialysis machine has a dialyzer 1 which has a blood chamber 2 and a dialysis fluid 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 fluid chamber 3 is a component of a dialysis fluid circuit 6. 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.

[0033] The extracorporeal blood circuit 5 furthermore has a separate inflow 14 and a separate outflow 15 for flushing liquid. It is alternatively naturally possible and covered by the invention that the flushing liquid enters into the extracorporeal blood circuit via the arterial port 7 and/or leaves it again via the venous port 11. A short-circuit of the arterial and venous ports is conceivable for the purpose of a closed-loop operation. It can nevertheless be advantageous for the flushing liquid charged with microbubbles to flow out of the circuit via the venous port or via a separate outflow. A reversal of the flow of the blood flow direction against the direction of blood flow is conceivable.

[0034] 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.

[0035] The shown extracorporeal blood circuit can be flushed using a process in accordance with the invention. Flushing liquid is thus supplied at the separate inflow 14 and is conveyed through the circuit by means of the blood pump 9. The blood pump is not operated at a constant conveying rate over a certain time period, for example 3 minutes, during the flushing procedure, but the pump speed is rather increased by a factor of 2 and lowered again in brief periodic intervals of around 2 seconds. This results in a periodic change in the flow rate and in the pressure of the flushing liquid in the extracorporeal blood circuit, which in turn promotes the detachment of microbubbles.

[0036] The flushing can, for example, be carried out during the priming or during a treatment break. It is, for example, conceivable to carry out the process during the duration of a pressure holding test.

[0037] If the process is carried out during the priming, a detachment of already present microbubbles can be brought about by adapting the pump rate in the initial flushing of the extracorporeal circuit. The extracorporeal circuit can be filled to a maximum with degased flushing solution. Pressure bursts can be generated by a repeated stopping and restarting of the blood pump. Microbubbles can be detached from the hose wall and transported away by the flushing solution by this and by a pump rate increased in the further procedure. The flushing solution can be discarded.

[0038] If the extracorporeal blood treatment is continued after the standstill of the blood pump after ending the method in accordance with the invention, provision is made within the framework of the described embodiment that the conveying speed of the blood pump is slowly increased at the start of the treatment. A detachment of microbubbles from the extracorporeal line system at the start of treatment can thus be reduced. Provision is specifically made that the conveying speed is increased on a linear ramp with an increase of 200 ml/min.sup.2 so that the desired value of 400 ml/min.sup.2 is only reached after 2 minutes. Other algorithms for the increase and other desired values are naturally also covered by the invention.

[0039] Finally, it can be stated that the partly stationary microbubbles are detached within the framework of the method in accordance with the invention, for example by means of a repeated stop and go of the blood pump and/or by means of a high pump speed and are removed from the extracorporeal circuit by means of present sinks and by means of sinks optionally to be provided in the venous branch of the extracorporeal circuit (e.g. using the UF pump via the dialyzer membrane or via the substitution port or via a further drain in the venous branch). The circuit can be filled to a maximum during the intimal filling of the extracorporeal blood circuit with degased substitution liquid and the air collections and microbubble reservoirs can be attacked and reduced by means of flow and pressure bursts (e.g. by a brief maximum blood pump rate, blocking and releasing the venous clamp, etc.). After a stop of the blood pump before or during the treatment, the blood pump can always be slowly ramped up, e.g. in a ramp with no more than 200 ml/min.sup.2, which means that a possible desired rate of 400 ml/min ml/min.sup.2 would only be 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 of the substitution pump can remain at a minimum during the bypass (e.g. pump stop) and both rates can be slowly ramped up to their desired value again after the bypass.