METHOD OF IDENTIFYING A FILTER

Abstract

The present invention relates to a method of identifying a filter, wherein the filter has at least one retentate side and at least one permeate side which are separated from one another by at least one filter medium, wherein the method comprises generating a pressure in a fluid, in particular in a liquid, on the retentate side or on the permeate side by means of a pressure source, in particular by means of a pump; switching off the pressure source; and the measurement of the pressure development in the fluid over time subsequent to the switching off of the pressure source.

Claims

1. A method of identifying a filter, wherein the filter has at least one retentate side and at least one permeate side which are separated from one another by at least one filter medium, wherein the method comprises generating a pressure in a fluid, in particular in a liquid, on the retentate side or on the permeate side by means of at least one pressure source, in particular by means of at least one pump; switching off the pressure source; and the measurement of the pressure development in the fluid over time subsequent to the switching off of the pressure source.

2. A method in accordance with claim 1, characterized in that the filter is a dialyzer; and/or in that the filter medium is a semi-permeable membrane.

3. A method in accordance with claim 1, characterized in that the pressure development is only measured by means of a single pressure sensor, with provision preferably being made that the pressure is measured on that side (permeate side or retentate side) of the filter on which the pressure is generated by the pressure source.

4. A method in accordance with claim 1, characterized in that the pressure source increases the pressure in the fluid for so long until a specific pressure has been reached; and in that the pressure source is subsequently switched off.

5. A method in accordance with claim 1, characterized in that the retentate side and/or the permeate side of the filter is/are connected to one or more fluid lines, with one or more blocking valves being provided in these fluid lines; and in that these blocking valves are closed during the measurement of the pressure development over time in the fluid.

6. A method in accordance with claim 1, characterized in that the filter is completely filled with fluid before the application of the pressure.

7. A system of identifying a filter, wherein the filter has at least one retentate side and at least one permeate side, the sides being separated from one another by at least one filter medium, wherein at least one pressure source, in particular at least one pump, is provided which is configured and arranged such that a pressure can be generated in a fluid, in particular in a liquid, on the retentate side or on the permeate side of the filter and comprising at least one pressure sensor which is arranged such that the pressure development over time in the fluid can be determined by means of the pressure sensor, with the system furthermore having at least one control unit which is connected to the pressure source and to the pressure sensor such that the measurement of the pressure development over time takes place after the switching off of the pressure source.

8. A system in accordance with claim 7, characterized in that the filter is a dialyzer; and/or in that the filter medium is a semi-permeable membrane.

9. A system in accordance with claim 7, characterized in that only a single pressure sensor is present, with provision preferably being made that this pressure sensor is arranged on that side (permeate side or retentate side) of the filter on which the pressure can be generated by the pressure source.

10. A system in accordance with claim 7, characterized in that no sensor is present for detecting mechanically or optically detectable filter features.

11. A system in accordance with claim 7, characterized in that the control unit is configured such that it controls the pressure source so that the pressure in the fluid is increased until a specific pressure has been reached and subsequently switches off the pressure source.

12. A system in accordance with claim 7, characterized in that the retentate side and/or the permeate side of the filter is/are connected to one or more fluid lines, with one or more blocking valves being provided in these fluid lines, and with the control unit being configured such that these blocking valves are closed during the measurement of the pressure development over time in the fluid.

13. A system in accordance with claim 12, characterized in that the retentate side and the permeate side are each connected to an inflow line and to an outflow line; in that the pressure source is arranged in one of these lines; and in that the named blocking valves are located in the further lines.

14. A blood treatment device, in particular a dialysis machine, having at least one system in accordance with claim 7.

Description

[0033] Further details and advantages of the invention will be explained in more detail with reference to an embodiment shown in the drawing.

[0034] There are shown:

[0035] FIG. 1: a schematic view of a system in accordance with the present invention for identifying a filter; and

[0036] FIG. 2: time curves of the pressure on the pressure build-up and after the switching off of the pressure source for different types of filter.

[0037] In FIG. 1, a line or a patient connection is marked by the reference numeral A1 which is connected to the patient in the operation of a blood treatment device and, for example, conducts blood from the patient to the dialyzer D in an extracorporeal circuit.

[0038] The pump B and the dialyzer D, which is separated by a semi-permeable membrane D1 into a retentate side R and into a permeate side P, are located in this extracorporeal circuit.

[0039] The reference numeral A2 designates a second line of the extracorporeal blood circuit or a patient connection through which the retentate is conveyed back to the patient in the operation of the apparatus. As can be seen from FIG. 1, a hose clamp F, by means of which the line A2 can be blocked, is located in the line A2.

[0040] As can further be seen from FIG. 1, the permeate side P of the filter D is likewise connected to a feed line A4 and to a drain line A3. The lines A4 and A3 likewise have hose clamps G and E by means of which these lines can be blocked. Reference numeral H designates the hydraulics of the system which can, for example, be the supply of a blood treatment device with dialysis solution, pumps for conveying the dialysis solution, etc. In treatment operation, the dialysis solution is transported through the line A4 to the filter D and the dialysis solution is led off from the filter D through the line A3.

[0041] The system hoses A1 and A2 have a limited stiffness and thus represent a pressure-dependent volume.

[0042] As can furthermore be seen from FIG. 1, a pressure sensor C is located between the pump B and the filter D for measuring the pressure p.

[0043] The method of identifying the filter is designed as follows:

[0044] The pump B conveys until a specific previously selected pressure is adopted at the pressure sensor C which is arranged between the pump P and the filter D. It can in this respect, for example, be a relative pressure of 1 bar.

[0045] If this pressure is reached, this is recognized by a control unit and the pump B is switched off. A pressure is adopted by a flow over the membrane D1 in the filter D in the system hoses A3, A4 up to the time of the switching off of the pump B. This pressure is dependent on the flow resistance of the membrane D1. The smaller the flow resistance of the membrane, the more liquid flows over the membrane into the lines A3 and A4 during the operation of the pump B.

[0046] After the switching off of the pump B, a pressure equalization takes place over the membrane D1 whose speed depends on the type of filter or on the property of the filter medium. In this respect, liquid is displaced into the system hoses A3 and A4.

[0047] With a membrane having a small flow resistance or a high ultrafiltration coefficient, a relatively high excess pressure is already adopted in the hoses A3 and A4 during the operation of the pump B since a comparatively large liquid quantity already passes over the membrane D1. This has the consequence that the pressure p at the pressure sensor C only drops by a relatively small amount within a previously defined time period, for example <5 seconds, after the switching off of the pump.

[0048] This can be recognized with reference to the line A in FIG. 2. The pressure is increased by the pump up to the time T1. The pump is then switched off and the clamps E, F and G are closed. As can be seen from the pressure curve A, the pressure only drops by a relatively small amount, typically by less than 30 mm Hg, after the switching off of the pump, that is after the time T1, since only a relatively small liquid quantity is displaced over the membrane up to the complete pressure equalization.

[0049] With a membrane having a high flow resistance or a small ultrafiltration coefficient, a different pressure curve results as can be recognized with reference to the line B in FIG. 2.

[0050] With a membrane having such a high flow resistance, a relatively small excess pressure is adopted in the system hoses A3 and A4 during the conveying of the pump B since only a comparatively small amount of liquid passes over the membrane D1.

[0051] After the switching off of the pump at the time T1, the pressure p at the pressure sensor C consequently drops by a relatively high amount in the named time period, typically of 5<seconds. The pressure drop is typically above 100 mm Hg, as can be recognized from line B. This is due to the fact that a relatively large liquid amount is still displaced over the membrane up to the complete pressure equalization, which results in a corresponding pressure drop in the compartment of the filter from which the liquid is displaced.

[0052] In the embodiment, the pump B and the pressure sensor C are on the blood side. Arranging the pump and the sensor on the dialyzate side is, however, likewise covered by the invention in principle.