System for preparing a concentrate solution

Abstract: System for preparation of a fluid intended for medical use, for example dialysis fluid or replacement fluid for heamofiltration or a concentrate for preparation for such fluids, including a source (1, 2) of pure water and at least one cartridge or another vessel (27-29) containing a powder which is to be dissolved in the said water for preparation of the desired fluid. The system according to the invention is characterized by means (3, 16, 17, 18, 19) for conducting the water to a mixing vessel (21) and said cartridge or cartridges (27-29) and means (22) for recirculation of the water or partially prepared fluid through said cartridge or one of said cartridges until an appropriate concentration from the complete or partial dissolving of the powder is obtained.

Description: The present invention relates to a system for preparing a concentration solution for use as a medical solution, for example, dialysis fluid or replacement fluid for hemofiltration or a concentrate for preparation of such fluids. Previous systems available for similar purposes normally start from one or more concentrates in liquid form. US-A-4 158 034 discloses how a concentrate in liquid form is mixed with water for preparation of a dialysis fluid. EP-A-0 022 922 and US-A-4 783 273 disclose how two liquid-based concentrates are mixed with water to obtain a fluid intended for medical use, for example dialysis fluid. More recently, systems have been introduced using one or more concentrates in powder form. US-A-4 784 495 discloses how one or more such powder-based concentrates can be used, possibly with the addition of a liquid-based concentrate. US-A-4 848 916 discloses an apparatus for bulk mixing of bicarbonate solutions by adding bicarbonate powder to water enclosed in a mixing vessel. In order to promote the dissolution of the powder, the water is recirculated in an external recirculation circuit until the powder is completely dissolved. If a concentrate in powder form is used, where the powder is hard to dissolve, it can be difficult to achieve an adequately fast dissolving in the system according to US-A-4 784 495. Furthermore, the system according to said patent can become relatively complicated if it is desired to add several different, individually pre-packed powder-based concentrates. DISCLOSURE OF THE INVENTION The above-mentioned problems are solved by the present invention which relates to a system for preparing a concentrate solution for use as a medical solution, for example, dialysis fluid or replacement fluid or hemofiltration or a concentrate fluid for preparation of such fluids, comprising a container, a supply means of pure water for supplying a predetermined amount of water to said container, recirculation means for recirculating said predetermined amount of water in a recirculation path including said container. According to the invention, the system comprises a plurality of vessels, each containing an in water dissolvable solid substance, said recirculation means recirculating said predetermined amount of water in said recirculation path including said container and a first of said vessels, for at least partially dissolving the substance of said first vessel until a predetermined concentration is obtained for providing a partially prepared solution, said recirculation means further comprising valve means for connecting said container to a further of said plurality of vessels for including each vessel one by one in the recirculation path replacing the previous vessel, for recirculating said partially prepared solution in said recirculation path for at least partially dissolving the substance of each of said vessels until a predetermined concentration is obtained for providing said concentrate solution. By means of this recirculation even a relatively difficult to dissolve powder-based concentrate can be dissolved. At the same time a liquid-based concentrate can be prepared in the container from one or more powder-based concentrates which, after preparation, can be conveyed to conventional dialysis machines which otherwise normally receive such liquid-based concentrates from one or more external containers. Preferably, the system according to the invention comprises determination means included within the recirculation path for determining the concentration level of the partially prepared solution of said recirculation path, whereby said recirculation means further comprising control means for terminating the flow through the one of said vessels, which is connected to the recirculation path, when a predetermined concentration level has been obtained as determined by said determination means. Thus, precisely the right amount of concentrate for the patient can be taken from each vessel. In other words an individual dosage can be obtained. Such determination means can be a conductivity meter or other suitable means for measuring the concentration, such as a pH-meter or an ion-selective meter. The same substitution can also be made for the conductivity meters mentioned in the rest of this description. Further details and features are included in the subclaims. Further advantageous objects and features appear from the following detailed description of a preferred embodiment with reference to the drawings. Figures 1-3 show in the form of a block diagram a preferred embodiment of the system according to the invention in its three different connectable positions. Fig. 4 shows a diagram of the measured conductivity in the above-described recirculation circuit with the supply of three different concentrates. Figures 1-3 are block diagrams of a preferred embodiment of the system according to the invention in its three different positions. Figure 1 shows how a recirculation circuit 20 and a separate powder cartridge 5 are filled with water. The water is taken from an inlet 1 via a heating vessel 2 through conduits 3 and 4 to the powder cartridge 5, which is located between two connection pieces 6 and 7. When the cartridge 5 is filled, the water is further passed as shown in figure 1 through a conduit 8 and a valve 9 to a detector 10, which detects the presence of water and/or concentrate therein. The detection can include a certain time delay so that the fluid will have time to fill the subsequent conduit 11, valve 12, conduit 13, valve 14 and conduit 15. At the same time, water is conveyed from a branch point 16 through a conduit 17, a valve 18 and a conduit 19 to a recirculation circuit, which in its entirety is denoted by 20. This circuit includes a mixing vessel 21, a recirculation pump 22, a concentration measuring device 23, for example a conductivity meter, and connected between two valve units 24 and 25 a number of cartridges or other vessels 27, 28 and 29 for one or more powder concentrates and possibly some liquid-based concentrate. When a sufficient quantity fluid is supplied to the mixing vessel 21, the valve 18 is closed, which can occur under the control of a level indicator schematically shown by dashed line 30. Then, the recirculation pump 22 is started with the valve units 24 and 25 so positioned that the water passes through one of the vessels or cartridges 27-29. In figure 1, vessel 29 is connected. When the desired conductivity is obtained, which is monitored by help of the meter 23, the next cartridge 28 is connected, and then finally cartridge 27. If the prepared fluid in the mixing vessel 21 should include another liquid-based or easily dissolvable concentrate, the dissolving can occur during the filling of the mixing vessel 21 with the vessel containing this concentrate being connected to the conduit 17. Such a vessel 31 is indicated in block-form in dashed lines. When the recirculation circuit 20 is filled, the valve 18 is closed as showed in figure 2. Similarly, valve 9 is actuated when vessel 5 is filled. This position is also shown in figure 2. Simultaneously, valve 12 is switched from the position shown in figure 1 to that in figure 2, so that water from the conduit 4 can pass to a further vessel or powder cartridge 32 located between two connection pieces 33 and 34. When this cartridge 32 has been filled, the water with dissolved concentrate therein is conveyed through the conduit 35, valve 12, conduit 13, valve 14 and conduit 15 to a main line or conduit 36 which includes a pump 37 and a detector 38, for example a conductivity measuring device. This detector controls the valve 14 so that it is switched to the position shown in figure 3. The fluid from vessel 32 is now conveyed instead from valve 14 via a conduit 39 with a dosage pump 40 to the main line 36 to a mixing point 41 upstream of a restrictor 42. This restrictor 42, together with the pump 37 and a gastrap not shown arranged further downstream, are used for de-gasing the prepared fluid. When valve 14 has been switched to the position shown in figure 3, the described system is ready for dialysis. An inlet valve 43 in the recirculation circuit 20 is thus actuated so the pump 22 can pump prepared fluid from the mixing vessel 21 to a mixing point 44, to which concentrate from vessel 5 is conveyed via valve 9 and conduit 45. The appropriate concentration of the dissolved substance is measured in this conduit upstream and downstream of the mixing point 44. This can be achieved, for example, by means of a differential conductivity meter, whose measuring points are denoted by 46 and 47, respectively. The prepared solution can then be conveyed further through the conduit 45 with the help of a pump 48, which preferably consists of an accurately metering dosage pump, and finally to the main line 36, in which the concentration is once more checked by means of a meter 49, for example another conductivity measuring device. This meter 49 then controls the pump 48, as shown by dashed line 50 in figure 3. Additional concentrate is then added to the prepared solution at the mixing point 41 by means of a pump 40 controlled by the measuring device 38 as indicated by the dashed line 51. By means of this measuring device 38, which preferably consists of a conductivity meter, the final concentration of the prepared solution obtained from the system according to the invention is regulated. Finally, figure 4 shows a diagram of how the conductivity in the recirculation circuit 20 varies. Here it is assumed that the meter 23 consists of a conductivity measuring device and that the vessels 27, 28 and 29 contain three different salts. Thus, between time t0 and t1 one of these vessels is connected until the conductivity value c1 is obtained. Thereafter, the next vessel is connected until the conductivity value c2 is reached. Then the last vessel is connected which remains connected until the conductivity obtains the desired value c3. At this point the valve 43 is switched over so that the ready-prepared solution can be conducted to the mixing point 44. At this mixing point concentrate from the vessel 5 is added. The mixture thus obtained is then led to a mixing point 52 in the main line 36 where it is mixed with water from the heating vessel 2. At the next mixing point 41, concentrate from the vessel 32 is then added. After a final check in the measuring device 38, the ready prepared solution can then be conducted to its place of consumption, as symbolized by an arrow 53.

Claims: System for preparing a concentrate solution for use as a medical solution, for example, dialysis fluid or replacement fluid for hemofiltration or a concentrate fluid for preparation of such fluids, comprising a container (21); water supply means (17) for supplying a predetermined amount of water to said container; recirculation means (22) for recirculating said predetermined amount of water in a recirculation path including said container (21); characterized by a plurality of vessels (27, 28, 29), each containing an in water dissolvable solid substance; said recirculation means (22) recirculating said predetermined amount of water in said recirculation path including said container (21) and a first of said vessels (29), for at least partially dissolving the substance of said first vessel until a predetermined concentration is obtained for providing a partially prepared solution; said recirculation means further comprising valve means (24, 25) for connecting said container (21) to a further of said plurality of vessels (27,28) for including each vessel one by one in the recirculation path replacing the previous vessel, for recirculating said partially prepared solution in said recirculation path for at least partially dissolving the substance of each of said vessels until a predetermined concentration is obtained for providing said concentrate solution. System according to claim 1, characterized by determination means (23) included within the recirculation path for determining the concentration level of the partially prepared solution of said recirculation path; said recirculation means further comprising control means (22, 43), for terminating the flow through the one of said vessels, which is connected to the recirculation path, when a predetermined concentration level has been obtained as determined by said determination means. System according to claim 2, characterized in that said determination means comprises a conductivity meter (23) for determining the conductivity and thus the concentration level of said partially prepared solution. System according to any one of the previous claims, characterized in that said recirculation means comprises pump means (22) for recirculating the partially prepared solution in the recirculation path. System according to any one of the previous claims, characterized by withdrawal means (43) for withdrawing prepared concentrate solution from said container. System according to any one of the previous claims, characterized in that said recirculation means comprises a pump means (22) for metering the concentrate solution to an outlet conduit for using said concentrate solution as a medical solution. System according to claim 6, characterized in that said recirculation means comprises an outlet valve (43) for connecting said container to said outlet conduit. System according to any one of the previous claims, characterized by a heating device (2) for heating said supplied water. System according to any one of the previous claims, characterized in that said supply means for water comprises a valve means (18) for terminating said supply of water when a predetermined amount of water has been supplied, as determined by for example a level indicator (30). System according to any one of the previous claims, characterized in that said plurality of vessels contains an excess of solid substances, so that said concentrate solution can be prepared with the content of said plurality of vessels. System according to any one of the previous claims, characterized in that there are three vessels (27, 28, 29) containing three different salts. System according to any one of the previous claims, characterized in that each of said plurality of vessels is a cartridge. System according to anyone of the previous claims, characterized by a further vessel (31) connected in parallel with said plurality of vessels and containing a liquid-based concentrate solution intended to be included in the concentrate solution. System according to claim 13, characterized in that said further vessel (31) is connected to said water supply means (17) for mixing said liquid-based concentrate solution with water and supplying said mixture to said container (21). System according to any one of the previous claims, characterized by a level indicator (30) for terminating the supply of water when a predetermined amount of water has been supplied. System according to any one of the previous claims, characterized in that said recirculation means comprises a recirculation conduit for forming said recirculation path, comprising said container (21), said valve means (24, 25) and one of said vessels (29). System according to any one of the previous claims, characterized by further comprising a secondary vessel (5), containing an in water dissolvable solid substance; secondary water supply means (4) for supplying water to said secondary vessel for dissolving said solid substance and forming a secondary concentrate solution; mixing means (44) for mixing said secondary concentrate solution with said concentrate solution withdrawn from said recirculation means for forming said medical solution. System according to claim 17, characterized by further comprising a tertiary vessel (32), containing an in water dissolvable solid substance; tertiary water supply means (4) for supplying water to said tertiary vessel for dissolving said solid substance and forming a tertiary concentrate solution; mixing means (41) for mixing said tertiary concentrate solution with said concentrate solution withdrawn from said recirculation means, possibly mixed with said secondary concentrate solution for forming said medical solution. System according to any one of the previous claims, characterized by a conduit (3, 17) for supplying water from said water supply means (2) straight to one of said vessels (31, 27, 28, 29) for flushing therefrom a predetermined quantity of said solid substance or liquid-based concentrate solution directly to the container (21).

Inventors: JOENSSON LENNART, KNUTSSON STEFAN, JOENSSON, LENNART, KNUTSSON, STEFAN, JÖNSSON, Lennart
Applicants: GAMBRO AB
Application year: 1991
Main classification: B01F5
IPC codes: A61J3, B01F5, A61M1, B01F15, B01F3, B01F1