Method of identifying a filter

Abstract

A method of identifying a type of a filter, which has at least one retentate side and at least one permeate side separated from one another by at least one filter medium, includes generating a pressure in a fluid, in particular in a liquid, on the retentate side or on the permeate side via a pressure source. The method then includes switching off the pressure source, and measuring a pressure development in the fluid over time subsequent to the switching off of the pressure source.

Claims

1. A method of determining, for a dialyzer that includes a retentate side and a permeate side which are separated from one another by a semipermeable membrane, whether the dialyzer has a high ultrafiltration coefficient or a low flow resistance, or a low ultrafiltration coefficient or a high flow resistance, said method comprising the steps of: connecting a pressure source pump on the retentate side inlet of the dialyzer and a pressure sensor between the dialyzer and the pump; providing blocking valves on the retentate side outlet, and the permeate side inlet and outlet; connecting a control unit to the pump, the blocking valves, and the pressure sensor; filling the dialyzer completely with a dialysis solution; closing all of the blocking valves; with the pump, generating a specific predetermined pressure in the dialysis solution on the retentate side; switching off the pump; and measuring a pressure drop in the dialysis fluid over time subsequent to the switching off of the pump, the pressure drop being measured by the pressure sensor, with the control unit being configured to measure the pressure drop over time after the switching off of the pump, and to determine the dialyzer as having the high ultrafiltration coefficient or the low flow resistance if the pressure drops by a first predefined amount within a predefined time period after the switching off of the pump, and to determine the dialyzer as having the low ultrafiltration coefficient or the high flow resistance if the pressure drops by a second predefined amount in the predefined time period after the switching off of the pump, with the second predefined amount being greater than the first predefined amount, and with the retentate side being the dialysate side when the permeate side is the blood side, and the retentate side being the blood side when the permeate side is the dialysate side.

2. The method in accordance with claim 1, wherein the retentate side and/or the permeate side of the dialysis filter is/are connected to one or more fluid lines, with one or more of the blocking valves being provided in the one or more fluid lines.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There are shown:

(2) FIG. 1: a schematic view of a system in accordance with the present invention for identifying a filter; and

(3) 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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

(5) 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.

(6) 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.

(7) 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.

(8) 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.

(9) The system hoses A1 and A2 have a limited stiffness and thus represent a pressure-dependent volume.

(10) 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.

(11) The method of identifying the filter is designed as follows:

(12) 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.

(13) 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.

(14) 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.

(15) 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.

(16) 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.

(17) 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.

(18) 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.

(19) 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.

(20) 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.

(21) The invention being thus described, it will be apparent that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be recognized by one skilled in the art are intended to be included within the scope of the following claims.