Supervision in system for generating medical fluid

Abstract

A system for generating a medical fluid comprises a main pump (P0) in a main path (11) connected to a source of base fluid, and first and second pumps (P1, P2) for dosing a respective concentrate into the main path at first and second dosing points (DPa, DPb). The system is operated to generate the medical fluid by operating the main pump at a production speed; operating the first pump at a predetermined speed relation to the production speed; adjusting, by feedback control, a current speed of the second pump (P2) to achieve a target conductivity in a first signal (SS1) from a first conductivity sensor (15a) located downstream of the dosing points; monitoring a second signal (SS2) from a second conductivity sensor (15b) located intermediate the dosing points, in relation to an allowable range; and adjusting the allowable range as a function of the current speed of the second pump.

Description

[0001] SUPERVISION IN SYSTEM FOR GENERATING MEDICAL FLUID

[0002] Technical Field

[0003] The present disclosure relates generally to preparation of medical fluid, for example for use in renal replacement therapy, by mixing a base fluid with one or more concentrates, and in particular to supervision of such preparation.

[0004] Background Art

[0005] Renal replacement therapy (RRT) is a therapy that replaces the normal bloodfiltering function of the kidneys. It is used when the kidneys are not working well, which is known as kidney failure and includes acute kidney injury (AKI) and chronic kidney disease (CKD). RRT involves removal of water from the blood of the patient suffering from kidney failure, as well as exchange of solutes with the blood. One example of RRT is peritoneal dialysis (PD), in which a medical fluid is infused into the peritoneal cavity of the patient to interface with the blood of the patient through the peritoneal membrane. Another example of RRT is extracorporeal (EC) blood therapy, in which blood is circulated outside of the patient and interfaced with one or more medical fluids. Modalities of extracorporeal blood therapy include hemodialysis (HD), hemofiltration (HF) and hemodiafiltration (HDF).

[0006] Medical fluids used in HD and PD are commonly known as dialysis fluids. In HF, the medical fluid is known as replacement fluid, since it is infused into the blood of the patient to replace fluid removed during therapy. In HDF, both dialysis fluid and replacement fluid are used.

[0007] RRT is typically automated and performed under control of a dialysis machine. In PD, the machine is known as a cycler, which is connected in fluid communication with the peritoneal cavity and is operated to control the flow of fresh dialysis fluid into the peritoneal cavity and the flow of spent dialysis fluid from the peritoneal cavity. In EC blood therapy, there are two main categories of machines: "chronic machines" for treatment of patient suffering from CKD, and "acute machines" for treatment of patients suffering from AKI.

[0008] Over time, RRT consumes large quantities of medical fluid. It is generally desirable to provide a technique of generating medical fluid for RTT on-demand with accurate composition.

[0009] It is known to prepare medical fluid for EC blood therapy by dosing plural liquid concentrates into a flow of a purified water at separate mixing points along a main line. Examples of techniques for controlling the dosing of the liquid concentrates based onsignal(s) from one or more conductivity sensors in the main line are disclosed in US 10076735. It is also proposed in US 10076735 to provide a protective sensor between two mixing points in the main line and monitor a conductivity signal from the protective sensor in relation to given limits, for the purpose of error detection.

[0010] It is generally desirable to reduce the complexity of systems for generating medical fluid. At the same time, it is vital that the medical fluid is generated with an accurate composition.

[0011] Summary

[0012] It is an objective to at least partly overcome one or more limitations of the prior art.

[0013] One objective is to provide a simple and robust technique of generating medical fluid by mixing a base fluid with two or more concentrates.

[0014] Another objective is to enable supervision of such a technique for error detection. One or more of these objectives, as well as further objectives that may appear from the description below, are at least partly achieved by a system, a computer-implemented method and a computer-readable medium according to the independent claims, embodiments thereof being defined by the dependent claims.

[0015] The present disclosure provides a technique of operating a system for generating a medical fluid. The technique based on the insight that it may be advantageous to configure such a system to control the flow rate of the medical fluid by a main pump in a main fluid path having an inlet for a base fluid, and to supply concentrates to the main fluid path upstream of the main pump, so that the medical fluid is formed in the main fluid path as the concentrates mix with the base fluid. To simplify the structure and operation of the system, the speed of a first supply pump for dosing a first concentrate at a first dosing point is set to have a fixed relation to the speed of the main pump. A second supply pump for dosing a second concentrate at a second dosing point downstream of the first dosing point is operated, by feedback control, to generate a target conductivity at a first conductivity sensor downstream of the dosing points. Such a system has low complexity and is capable of compensating for variations in the conductivity of the second concentrate that may occur during fluid production. The Applicant has realized that it may be advisable, from a safety standpoint, to supervise the conductivity of the mixture in the main fluid path between the first and second dosing points. Such supervision is performed by monitoring an output signal of a second conductivity sensor, which is arranged between the dosing points, in relation to an allowable range. To minimize the risk for false alarms, the allowable range is adjusted as a function of the current speed of the main pump. If this is not done, achange in the conductivity of the second concentrate may cause the output signal to fall outside the allowable range, even if the system produces the medical fluid according to specifications.

[0016] Any reference to "conductivity" and conductivity sensor" herein is not strictly limited to the property of electrical conductivity. Rather, these terms include any composition-related parameter (CRP) that is equivalent to electrical conductivity in view of the purpose of detecting changes in fluid composition.

[0017] Still other objectives, aspects, embodiments, features and advantages may appear from the following detailed description, from the attached claims as well as from the drawings.

[0018] Brief Description of the Drawings

[0019] FIG. 1 is a schematic diagram of an example system that involves generation of treatment fluid for RRT.

[0020] FIG. 2 is a block diagram of an example fluid generation system.

[0021] FIG. 3 shows the system of FIG. 2 during generation of medical fluid.

[0022] FIG. 4 is a side view of an example sub-system for generating a concentrate fluid from a powder concentrate.

[0023] FIG. 5 is a flow chart of an example method of operating a fluid generation system in a production phase.

[0024] FIGS 6A-6C are graphs of measured conductivity and an associated range for supervision of a fluid generation system during start-up and production phases, with FIG. 6A showing a static range, FIG. 6B showing an dynamically adjusted range, and FIG. 6C showing an enlarged portion of FIG. 6B.

[0025] FIG. 7 is a flow chart of an example method of operating a fluid generation system in a start-up phase.

[0026] FIGS 8A-8B show the system of FIG. 2 during the start-up phase.

[0027] FIG. 9 is a block diagram of an example fluid generation system according to a variant.

[0028] FIGS 10A-10B are flow charts of example methods of operating a fluid generation system in a production phase and a start-up phase, respectively.

[0029] Detailed Description of Example Embodiments

[0030] Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments are shown. Indeed, the subject of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, theseembodiments are provided so that this disclosure may satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0031] Also, it will be understood that, where possible, any of the advantages, features, functions, devices, and / or operational aspects of any of the embodiments described and / or contemplated herein may be included in any of the other embodiments described and / or contemplated herein, and / or vice versa. In addition, where possible, any terms expressed in the singular form herein are meant to also include the plural form and / or vice versa, unless explicitly stated otherwise. As used herein, "at least one" shall mean "one or more" and these phrases are intended to be interchangeable. Accordingly, the terms "a" and / or "an" shall mean "at least one" or "one or more," even though the phrase "one or more" or "at least one" is also used herein. As used herein, except where the context requires otherwise owing to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, that is, to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments.

[0032] As used herein, the terms "multiple", "plural" and "plurality" are intended to imply provision of two or more elements. The term "and / or" includes any and all combinations of one or more of the associated listed elements.

[0033] It will furthermore be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing the scope of the present disclosure.

[0034] Well-known functions or structures may not be described in detail for brevity and / or clarity. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0035] As used herein, "dialysis therapy" or "dialysis" refers to any therapy that replaces or supplements the renal function of a patient by use of a treatment fluid. Dialysis therapy includes, without limitation, extracorporeal (EC) blood therapy and peritoneal dialysis (PD) therapy. Dialysis therapy is also denoted renal replacement therapy, RRT, herein.

[0036] As used herein, "product water" refers to water that has a purity suitable for medical use. In some embodiments, the product water meets criteria of so-called "water for dialysis" "water for injection", or "ultrapure water". For example, criteria for "waterfor dialysis" or "dialysis water" may be defined in accordance with ANSI / AAMI / ISO 23500-3:2019.

[0037] As used herein, "medical fluid" refers to any fluid that contains one or more substances which are supplied to a patient for a curative, relieving or other medical purpose.

[0038] As used herein, "treatment fluid" refers to a medical fluid that is consumed as a result of dialysis therapy. Treatment fluid includes, without limitation, dialysis fluid for infusion into the peritoneal cavity during PD therapy, dialysis fluid for supply to a dialyzer during EC blood therapy, and replacement fluid and substitution fluid for infusion into blood during EC blood therapy.

[0039] As used herein, a "concentrate" is a substance that contains one or more compounds ("constituents") at a concentration that is higher than at the final use of the substance. A concentrate may be in the form a liquid or a powder. A concentrate is capable of being diluted, if a liquid, or dissolved, if a powder, in a solvent.

[0040] FIG. 1 shows an example system 1 which will be used to describe some embodiments. The system 1 comprises a fluid generation system (FGS) 10, which is operable to mix concentrates with a base fluid to produce a medical fluid. In the following, the medical fluid is a treatment fluid (TF) for use in renal replacement therapy (RRT). Any number of concentrates may be used. In FIG. 1, the FGS includes two concentrates Cl, C2. The FGS is arranged to receive the base fluid from a source 20 on a supply line 21. The base fluid is or contains product water, PW, that has a purity suitable for medical use. In the examples described herein, it is assumed that the base fluid is product water. The source 20 may or may not be configured to produce the base fluid on demand. In some embodiments, the source 20 is a device that is co-located with the FGS. The source 20 may be integrated with the FGS or be a separate machine. In an alternative, the source 20 is a centralized device which is configured to supply the base fluid to a plurality of receivers, for example within a dialysis clinic. In the illustrated example, TF is output by the FGS on a connecting line CE for use by an RRT system 30, which may or may not be part of the system 1, as indicated by dashed lines. The RRT system 30 is configured to perform a conventional RRT treatment by use of TF. RRT systems are well-known to the skilled person and will not be described in further detail.

[0041] The system 1 further includes a control arrangement or controller 100, which is configured to provide one or more control signals CSi for the FGS 10. By the control signal(s) CSi, the controller 100 causes the FGS to generate the treatment fluid TF with a desired ("target") composition and at a desired ("target") flow rate. The controller 100 is further configured to receive one or more output signals SSj of the FGS, for examplefrom one or more sensors. An example of an FGS will be described below with reference to FIG. 2.

[0042] In the illustrated example, the controller 100 comprises processor circuitry 101 and computer memory 102. A control program may be stored in the memory 102 and executed by the processor circuitry 101 to perform any of the methods, procedures, or functions as described herein. The control program may be supplied to the controller 100 on a computer-readable medium, which may be a tangible (non-transitory) product (e.g., magnetic medium, optical disk, read-only memory, flash memory, etc.) or a propagating signal. In the illustrated example, the controller 100 comprises a signal interface 103a for receiving the output signal(s) SSj from the FGS and providing the control signal(s) CSi. The controller 100 may also comprise an input / output (I / O) interface 103b for connection to a user interface (UI) device 110. The term "UI device" is intended to include any and all devices that are capable of performing guided humanmachine interaction comprising presentation of information and receipt of input. For example, the UI device 110 may comprise a combination of a display device and data entry hardware. The data entry hardware may include one or more of a keyboard, keypad, computer mouse, control buttons, touch panel, microphone and voice control functionality, camera and gesture control functionality, etc. Each of the interfaces 103a, 103b may be configured for wired or wireless data transmission in accordance with any standardized or proprietary protocol. It may be noted that the interfaces 103a, 103b may be implemented by a single interface device.

[0043] FIG. 2 is a schematic diagram of an example FGS 10. In the illustrated example, the FGS comprises a main fluid line or path ("main line") 11 that extends from an inlet 11' for base fluid to an outlet 11" for treatment fluid (TF). The inlet 11' and the outlet 11" may comprise terminal connectors for connection to corresponding terminal connectors on other fluid lines. With reference to FIG. 1, the inlet 11' may be connected to a terminal connector (not shown) on the supply line 21.

[0044] A main pump P0 is arranged in the main line 11 to define the flow rate of treatment fluid that is pumped to and through the outlet 11" when the FGS is operated to produce treatment fluid.

[0045] First and second supply arrangements Al, A2 are arranged in sequence upstream of the main pump P0 to supply a respective concentrate Cl, C2 into the main line 11. The first supply arrangement Al comprises a first concentrate inlet 14a', and a first concentrate supply line 14a that extends from the concentrate inlet 14a' to a first dosing point DPa in the main line 11. A first reservoir Rl, which holds a first concentrate Cl, is releasably connected to the first concentrate inlet 14a'. A first concentrate pump Pl ("first pump") is arranged in the first supply line 14a to pump the concentrate Cl fromthe reservoir R1 to the dosing point DPa. The second supply arrangement Al comprises a second concentrate inlet 14b', and a second concentrate supply line 14b that extends from the concentrate inlet 14b' to a second dosing point DPb in the main line 11. A second reservoir R2, which holds a second concentrate C2, is releasably connected to the second concentrate inlet 14b'. A second concentrate pump P2 ("second pump”) is arranged in the second supply line 14b to pump the concentrate C2 from the reservoir R2 to the second dosing point DPb, which is located downstream of the first dosing point DPa along the main line 11.

[0046] In some embodiments, when the treatment fluid is produced for use in EC blood therapy, Cl may be an acid concentrate and C2 may be a bicarbonate concentrate, as is well known in the art.

[0047] In the illustrated example, each of the first and second arrangements Al, A2 includes a throughflow mixing device 16a, 16b, which is arranged downstream of the respective dosing point DPa, DPb and is configured impart mixing to the passing fluid. Thereby, during production, an effectively homogeneous mixture of base fluid and concentrate Cl is attained downstream of the mixing device 16a, and an effectively homogeneous mixture of base fluid and concentrates Cl, C2 is attained downstream of the mixing device 16b. The respective mixing device 16a, 16b may include a mixing chamber, and / or an in-line mixer, an injector mixer, or any other conventional device for mixing liquids as they flow through the device. At least one of the mixing devices 16a, 16b may be configured as a bubble trap for removing gas bubbles from the passing fluid.

[0048] A first sensor 15a is arranged in the main line 11 downstream of the second dosing point DPb, and a second sensor 15b is arranged in the main line 11 intermediate the first and second supply arrangements Al, A2, or equivalently, intermediate the first and second dosing points DPa, DPb. In the illustrated example, the sensor 15a is arranged upstream of the main pump P0 but can equally well be positioned downstream the main pump P0 but upstream the three-way valve 13 (below). The sensors 15a, 15b are denoted "conductivity sensors" in the following and are presumed to provide a respective output signal SSI, SS2 indicative of the conductivity of the passing fluid. However, as used herein, a "conductivity sensor" is any sensor capable of measuring a relevant composition-related parameter (CRP) of the passing fluid. Depending on implementation, such a relevant CRP may designate a conductivity, a resistivity, a concentration of one or more substances, or a pH value of the passing fluid.

[0049] Downstream of the main pump P0, a 3-way valve 13 is arranged in the main line 11 to define a junction to a drain line 12, which extends to a drain 40. The drain 40 may be a fixed installation such as a sink, bathtub, toilet, floor drain, etc. Alternatively, thedrain 40 may be a reservoir or container for collecting fluid. The 3-way valve 13 is operable to direct the fluid flow either along the main line 11 to the outlet 11 " or from the main line 11 into the drain line 12. It is to be understood that any 3-way valve disclosed herein may be replaced by two or more on / off valves.

[0050] It is to be understood that FIG. 2 is a simplified diagram and that the FGS may include additional components, such as further sensors, one or more heat exchangers, one or more filters for reducing bacteria and endotoxins, etc. For example, the FGS may include an additional conductivity sensor ("protective sensor"), which is associated with a conductivity sensor that is used for operational control ("control sensor"), such that the output signals of the control sensor and the protective sensor provide the same information. The output signal of the respective protective sensor is monitored by a separate supervision system for detection of malfunctions. The use of protective sensors is standard practice in the field of RRT and will not be described in further detail.

[0051] FIG. 3 shows the system of FIG. 2 in a production phase, in which treatment fluid is produced and output. In FIG. 3, as well as other corresponding drawings herein, open valves and operating fluid pumps are indicated by filled symbols, fluid lines through which fluid is flowing are indicated by thicker lines, and flow directions are indicated by thick solid arrows. The valve 13 is open along the main line 11 and closed towards the drain line 12. The main pump P0 is operated at a production speed to generate a flow rate QPQ. In the production phase, QPQ is equal to the production flow rate Qpp of treatment fluid. The first pump Pl is operated at a first speed to generate a production flow rate Q of the first concentrate Cl. The second pump P2 is operated at a second speed to generate a production flow rate Q 2 °f the second concentrate C2. By locating the main pump P0 downstream of the dosing points DPa, DPb, the production speed of the main pump P0 defines the production rate of treatment fluid. The flow rate Qpp of base fluid into the FGS is given by the difference between the flow rate QPQ and the sum of the flow rates

[0052]

[0053] Qc2:QBF=QPO ~ .Qci + QC2^- Thus, in the production phase, the speed of the main pump P0 is set to achieve a desired (target) flow rate of treatment fluid, and the speeds of the pumps Pl, P2 are controlled to achieve a desired (target) composition of the treatment fluid.

[0054] In the present disclosure, it is presumed that the first pump Pl is controlled, in the production phase, to achieve a predefined relation, RC1, between the flow rates Q and QPQ : QPQ = Qa ■ RC1. It is realized that RC1 corresponds to a desired ("target") mixing ratio between base fluid and concentrate Cl in the treatment fluid to be produced. In some embodiments, achieving RC1 corresponds to operating the first pump Pl to maintain a predetermined relation between the speeds of the first pump Pl and the main pump P0 ("speed ratio", SR). In other words, the speed of the first pumpPl is slaved to the speed of the main pump P0. The second pump P2, on the other hand, is controlled to achieve a target value in the output signal SSI of the first sensor 15a, where the target value is representative of the target composition of the treatment fluid. One reason for performing this feedback control is for the FGS to produce the treatment fluid with the target composition even if the composition of the second concentrate C2 should vary in the production phase.

[0055] Each of the first and second concentrates may comprise any number and types of constituent(s) of the resulting treatment fluid. It is realized that the concentrates Cl, C2 are in liquid form as they are pumped into the main line 11 at the respective dosing point DPa, DPb. It is not uncommon for a concentrate for RRT to be supplied as a powder or, equivalently, a granulate. Such a powder concentrate is then dissolved in a solvent, by the FGS, to produce a liquid concentrate for use in producing the treatment fluid. Advantages of using powder concentrates include minimized risk of microbial contamination and growth, ease of handling, and increased shelf life. For example, it is common practice to supply bicarbonate and sodium chloride as a powder concentrates for use in producing treatment fluid.

[0056] FIG. 4 is a side view of an example powder-to-liquid arrangement (PEA) 17, which is configured to convert a powder concentrate into a liquid concentrate. As installed in the FGS, the PEA 17 is arranged to receive a solvent, typically product water, on an input line 14b" and to output liquid concentrate on the supply line 14b. The PEA 17 includes a mounting structure or holder 18, which is configured for removable installation of the container R2, which holds a powder concentrate C2. The container R2 has an inlet 18a at its top and an outlet 18b at its bottom. When the container R2 is installed in the holder 18, the inlet 18a is fluidly connected to the inlet line 14b" and the outlet 18b is fluidly connected to the supply line 14b. The solvent that enters the container 18 via the inlet 18a is allowed to percolate through the bed of powder concentrate C2, resulting in a saturated solution of liquid concentrate at the outlet 18b. Through the operation of the second pump P2 (FIG. 3), liquid concentrate is drawn from the container R2.

[0057] The composition of the liquid concentrate that leaves of the FEA 17 may vary over time, for example as a result of uneven distribution of powder concentrate within the container R2. The distribution may become more uneven as the power concentrate is consumed. It is also possible that channels are formed within the bed of powder concentrate as the solvent penetrates the bed. Further, depending on the solubility temperature dependence of the concentrate constituent(s), the composition of the liquid concentrate may also vary as function of the temperature of the incoming solvent and / or the ambient temperature.Thus, if the FGS is operated on a liquid concentrate that is formed from a powder concentrate, it is possible or even likely that the composition of the liquid concentrate varies over time. Such a concentrate may then be installed as the second concentrate C2 in the FGS, so that any variation in composition is counteracted by the feedback control based on the output signal SSI.

[0058] The composition of the liquid concentrate from a container that holds the concentrate in liquid from may also vary over time, for example if the concentrate is in the form of a suspension. Due to sedimentation, a gradient may be formed in the container, resulting in varying composition out of the container. Such a concentrate may also be installed as the second concentrate in the FGS.

[0059] The operation of the FGS as described with reference to FIG. 3 presumes that the main pump P0 and the first pump Pl provide a consistent (stable) flow rate over time. This may be achieved by using volumetric pumps for the pumps P0, Pl. Alternatively or additionally, the operation of the respective pump P0, Pl may be actively controlled to achieve a target flow rate given by a flow meter. For example, a flow meter may be arranged in the main line 11 downstream of the second arrangement A2 and used for controlling the main pump P0.

[0060] As used herein, a "volumetric pump" is a pump that is configured to generate a well-defined flow rate of a fluid by repeatedly discharging a respective stroke volume of the fluid. Specifically, a volumetric pump is configured to drive a fluid by trapping a fixed and well-defined volume of the fluid in a pump chamber and by forcing (displacing) that trapped volume through a pump outlet by a movable pumping element in direct contact with the fluid. Volumetric pumps that may be used in the FGS include reciprocating pumps such as piston pumps, as well as rotary vane pumps and diaphragm pumps.

[0061] As described, the signal SSI from the first sensor 15a is used for controlling the speed of the second pump P2 in the production phase. The signal SS2 from the second sensor 15b is used for supervision of the operation of the first arrangement Al. Such supervision is warranted since proper operation of the FGS relies on the first arrangement Al supplying the first concentrate Cl with a consistent composition and at a consistent flow rate. Thus, in the production phase, the controller 100 monitors the signal SS2 in relation to an allowable range and takes action if the signal SS2 falls outside this range, for example by stopping the FGS or bypassing the flow towards the drain 40 and / or generating an alarm.

[0062] FIG. 6A is a graph of example signals SSI, SS2 generated by the sensors 15a, 15b in a start-up phase and a production phase for the FGS in FIG. 2. The start-up phase extends between times tl and t3 and will be described further below with reference toFIGS 7-8. In the production phase, which starts at time t3, the signal SSI is stable as a result of the feedback control of the second pump P2. Static lower and upper limits SL1', SL1" are set to define the allowable range. As seen, the signal SS2 starts to increase at time t4. At this time, the conductivity of the liquid concentrate C2 that is pumped into the main line 11 starts to decrease, causing the speed of the second pump P2 to be increased by the feedback control. The resulting increase of Q 2 will automatically decrease the flow rate Qpp of the base fluid into the FGS, recalling that:

[0063]

[0064] Thus, the signal SS2 starts to increase at time point t4. At time t4', the controller 100 generates an alarm via the UI device 110 (FIG. 1), since the signal SS2 exceeds the upper limit SL1". In the illustrated example, the decreasing concentration of the liquid concentrate C2 is the result of channeling in the container R2. At time t5, an operator of the FGS taps on the container R2 to collapse the channels, causing the conductivity of the liquid concentrate C2 to return to normal and, consequently, the signal SS2 to fall back within the allowable range. The controller 100 then terminates the alarm.

[0065] The alarm generated at time t4' in FIG. 6A does not represent an operational failure of the first arrangement Al, or an operational failure of the FGS to produce treatment fluid at desired composition and flow rate. Thus, the alarm is regarded as a false alarm. It is desirable to minimize the number of false alarms, since every false alarm interferes with the work of the staff that operates the FGS, for example staff in a dialysis clinic or an intensive care unit. Even worse, a false alarm may cause the controller 100 to terminate the production of treatment fluid, so that the RRT needs to be stopped as well. One solution to this problem may be to increase the allowable range. However, this reduces patient safety by decreasing the ability to timely detect a malfunction of the first supply arrangement Al.

[0066] FIG. 5 is a flow chart of an example method Ml of operating an FGS to mitigate the problem of false alarms. The method Ml may be performed by the controller 100. The method Ml is performed in the production phase. Dashed boxes designate optional steps.

[0067] In step S10, the main pump P0 is operated at a production speed, which may be fixed or variable in the production phase. In step Sil, the first pump Pl is operated at a first speed given by the predetermined speed relation ("speed ratio") SR, which defines the speed of the first pump Pl relative to the speed of the main pump P0. In step S13, the second concentrate pump P2 is operated by feedback control based on the signal SSI, to achieve the target conductivity in the signal SSI.In the production phase, steps S10, Sil and S13 are performed concurrently and continuously throughout the production phase. As will be described below with reference to FIG. 7, the FGS may transition to the production phase from a start-up phase in which the pumps P0, P2 are sequentially started. Alternatively, the start-up phase may be omitted and the production phase may be "kick started" by directly initiating steps S10, Sil and S13.

[0068] In step S15, the signal SS2 is monitored in relation to an allowable range. Further, in step S15, dedicated action to ensure or maintain patient safety is taken if and when the signal SS2 falls outside the allowable range. The dedicated action may also be denoted predefined action. Many different predefined actions are conceivable in step S15, depending on the patient safety required. One action is to perform a diversion operation to direct the generated fluid to drain. In the example of FIG. 3, the valve 13 may be operated to open fluid communication between the main line 11 and the drain line 12 while preventing fluid communication along the main line 11 to the outlet 11". Another action is to generate a warning (for example, an alarm signal) or an instruction for a user via the UI device 110. A further action is to stop the pumps P0, Pl, P2. These actions may be combined.

[0069] Step S16 is performed to the minimize the risk that step S15 results in unnecessary actions, for example generation of false alarms, while enabling step S15 to timely detect a malfunction of the first supply arrangement Al. In step SI 6, which is performed continuously throughout the production phase, the allowable range is adjusted as a function of the current speed of the second pump P2. Step S16 is based on the insight that the deviating behavior of the signal SS2 in FIG. 6A, between times t4 and t5, is caused by a change in the speed of the second pump P2 as a result of the feedback control based on the signal SSI. This means that the behavior of the signal SS2 is predictable given the speed of the pump P2 and, consequently, that the allowable range may be adjusted based thereon. Thus, step S16 may involve determining an expected value of the signal SS2, given the speed of the pump P2, and setting the allowable range in relation to the expected value. In some embodiments, the allowable range is aligned with expected value. In this context, "aligned with" implies that the expected value is at a predefined relative location within the allowable range. In a nonlimiting example, the predefined relative location is a midpoint of the allowable range, so that the allowable range is centered on the expected value.

[0070] FIG. 6B is a graph of example signals SSI, SS2 generated by the sensors 15a, 15b in a production phase for the FGS in FIG. 2 when operated in accordance with the method Ml. Like in FIG. 6A, the production phase extends from time t3. As seen, the upper and lower limits SL", SL' follow the signal SS2 so as to define an allowable rangeof fixed extent that is aligned with the signal SS2. Thus, no alarm is generated. At time t5, like in FIG. 6A, an operator taps on the container R2 to collapse the channels in the powder concentrate within the container R2, and the signal SS2 decreases. The allowable range follows the signal SS2 back to the new level.

[0071] Thus, as depicted in FIG. 5, step S16 may include a step SI 6b of determining an expected value of the signal SS2 as a function of a reference conductivity value for the signal SS2 and the current flow rate of the concentrate C2, and a step SI 6c of adjusting the allowable range to the expected conductivity in the signal SS2. The current flow rate of the concentrate C2 may be determined in a step SI 6a. In some embodiments of step SI 6a, the current flow rate of the concentrate C2 is determined by use of a predetermined function that relates speed to flow rate for the second pump P2. The predetermined function may be given by nominal data for the pump P2 or by a preceding calibration procedure for the pump P2. In other embodiments of step SI 6a, the current flow rate of the concentrate C2 is given by a dedicated flow meter (not shown) in the supply line 14b.

[0072] The reference conductivity value, which may be retrieved from memory in step S12, is the value that will be present in the signal SS2 when the pump P2 is operated to achieve the target conductivity in the signal SSI while the first pump Pl and the main pump P0 are operated in accordance with the speed ratio, SR. The reference conductivity may be measured by the sensor 15b early in the production phase or in a preceding production phase, or be estimated by calculations based on the nominal compositions of the base fluid and the concentrates. In FIG. 6B, the reference conductivity value is designated K2 pp and is attained in the signal SS2 at the beginning of the production phase.

[0073] In some embodiments, the expected conductivity value K2 )j is calculated in step SI 6b according to the following equation:

[0074] K2ADJ =K2REF ‘ C1+ (QC2 ~ QC2REF^ / QPO) (2)

[0075] with Qpo being the flow rate generated by the main pump P0 at the production speed, QC2REF being the flow rate generated by the second pump P2 when operated at a reference speed, Qp2 being the flow rate generated by the second pump P2 at the current speed, and K2ppp being the reference conductivity value. The reference speed is thus the speed of the second pump P2 when the reference conductivity value K2 ppp is attained in the signal SS2.

[0076] As shown in FIG. 5, the method Ml may include a step S14 of determining the reference speed for use in step SI 6a. In step S14, the reference speed may be set to avalue that is representative of the speed of the second pump P2 during an initial time period of the production phase, suitably when the speed is substantially stable. For example, the reference speed may be calculated as an average or median of the speed of the second pump P2 during the initial time period. The speed of the pump P2 may be given by a speed sensor (not shown) associated with the pump P2 or determined from the control signal CS2 for the pump P2. Step S14 may also involve determining the conductivity reference value K2 pp. For example, K2 pp may be calculated as an average or median of signal values in the signal SS2 during the initial time period. It is realized that step S12 may be omitted if K2 ppp is determined in step S14.

[0077] FIG. 7 is a flow chart of method M2 performed by the FGS before entering the production phase. The method M2 results in a "start-up phase" or "setup phase" of the FGS. The method M2 may be performed by the controller 100. FIGS 8A-8B show the FGS of FIG. 2 at two stages in the start-up phase. Throughout the start-up phase, the valve 13 is set to direct the fluid flow along the main line 11 into the drain line 12.

[0078] In step S20, the main pump P0 is operated at a main setup speed. The main setup speed may, but need not, be identical to the production speed. In step S21, the first pump Pl is operated at a first setup speed. Thereby, the FGS generates a mixture of the base fluid and the concentrate Cl. FIG. 8 A shows the FGS during step S21. Step S21 may comprise steps S21a-S21c. In step S21a, the speed of the first pump Pl is adjusted until a setup conductivity is attained in the signal SS2 or the signal SSI. In step S21b, the speed ratio SR is determined based on the current speeds of the pumps P0, Pl that yield the setup conductivity in step S21a. If the setup conductivity represents the above-mentioned target mixing ratio between base fluid and concentrate Cl, the speed ratio SR is directly given by the relation between the current speeds of the pumps P0, Pl. Otherwise, as understood by the skilled person, the speed ratio SR is determined by rescaling the relation between the current speeds to meet the target mixing ratio. In step S21c, the first setup speed is set in relation to the main setup speed so as to meet the speed ratio SR. In step S21c, if necessary, the main setup speed may be changed to be equal to the production speed, with the first setup speed being set accordingly.

[0079] The method M2 further includes a step S23, which is performed when the pumps P0, Pl are operated at the main setup speed and the first setup speed, respectively. In step S23, the second pump P2 is started and feedback control is initiated to adjust the speed of the pump P2 to achieve the target conductivity of the treatment fluid in the signal SSI. FIG. 8B shows the FGS during step S23.

[0080] In the context of the present application, the production phase is considered to start whenever step S23 is completed and treatment fluid is generated with a desired composition and flow rate. The FGS may then, at any suitable time, be operated todirect the treatment fluid towards the outlet 11", by opening fluid communication along the main line 11 while preventing fluid communication between the main line 11 and the drain line 12.

[0081] Reverting to FIG. 6B, the start-up phase extends from time tl to time t3, at which the target conductivity is attained in the signal SSI. The main pump P0 is started at time tl (step S20). Shortly thereafter, the first pump Pl is started and controlled to achieve the first setup speed (step S21), causing the signal SS2 to rise. A corresponding signal increase is seen in the signal SSI, with a time delay At as a result of the distance between the sensors 15a, 15b along the main line 11. Then, at time t2, the second pump P2 is started and controlled so that the signal SSI is at the target conductivity (step S23). As a result of step S23, the signal SS2 rises to a new plateau, which defines the reference conductivity value K2REP.

[0082] It may be desirable to also monitor the operation of the first supply arrangement Al during step S23. This is achieved by step S22 in FIG. 7, which involves monitoring the signal SS2 in relation to an allowable setup range, which may or may not be identical to the allowable range used in the production phase (cf. steps S15-S16). As shown, step S22 may include a step S22a of adjusting the allowable setup range as a function of the current speed of the second pump P2. By analogy with step S16 (FIG.

[0083] 5), step S22 may be performed by determining an expected value of the signal SS2 as a function of a reference setup conductivity value for the signal SS2 and the current speed of the pump P2, and by adjusting the allowable setup range to the expected value in the signal SS2.

[0084] FIG. 6C is an enlarged view of the start-up phase in FIG. 6B and shows an allowable setup range that is defined by lower and upper limits SLO', SLO". The reference setup conductivity value is designated K2 ' pp and is given by the signal level in the signal SS2 before step S23 is initiated, while the pumps P0, Pl are operated in accordance with steps S20-S21.

[0085] In some embodiments, the expected conductivity value K2' DJ is calculated in step S22a according to the following equation:

[0086] K2'ADJ =K2'REF ‘ C1+ (QC2 ~ Q'C2REF QPO) (3)

[0087] with Qpo being the flow rate generated by the main pump P0, Q'c2REF being the flow rate generated by the second pump P2 when operated at a reference setup speed, QC2 being the flow rate generated by the second pump P2 at the current speed, and K2'ppp being the reference setup conductivity value. The reference setup speed is the speed of the second pump P2 when K2' ppp is attained in the signal SS2. The referencesetup speed may be determined together with K2 ' pp, by analogy with step S14 (FIG.

[0088] 5), for subsequent determination of Q'c2REF based on the reference setup speed.

[0089] In step S22, dedicated action is taken if and when the second signal SS2 falls outside the allowable setup range. The dedicated action may be one or more of the conceivable actions listed above for step S15.

[0090] The monitoring technique as described in the foregoing is equally applicable to an FGS that is configured to generate treatment fluid by mixing more than two concentrates with a base fluid. FIG. 9 is a schematic diagram of an example FGS 10 that is configured to mix three concentrates Cl, C2, C3 with a base fluid. Compared to FIG.

[0091] 2, the FGS comprises a third supply arrangement A3, which is configured to supply a third concentrate C3 into the main line 11 at a third dosing point DPc, which is located intermediate the first and second dosing points DPa, DPb. The third supply arrangement A3 comprises a third concentrate inlet 14c', and a third concentrate supply line 14c that extends from the concentrate inlet 14c' to the third dosing point DPc. A third reservoir R3, which holds the third concentrate C3, is releasably connected to the third concentrate inlet 14c'. A third concentrate pump P3 ("third pump") is arranged in the third supply line 14c to pump the concentrate C3 from the reservoir R3 to the dosing point DPc. In the illustrated example, the third arrangement A3 includes a throughflow mixing device 16c, which may be similar to the mixing device 16a in the first arrangement 16a. A third conductivity sensor 15c is located in the main line 11 downstream of the third dosing point DPc and intermediate the dosing points DPa, DPb. The third sensor 15c is configured to provide an output signal SS3 indicative of the conductivity of the passing fluid.

[0092] In some embodiments, when the treatment fluid is produced for use in EC blood therapy, Cl may be an acid concentrate, C2 may be a bicarbonate concentrate, and C3 may be a potassium concentrate, as is well known in the art.

[0093] The operation of the FGS in FIG. 9 presumes that the pumps P0, Pl and P3 provide a consistent (stable) flow rate over time. By analogy with the pumps P0, Pl in FIG. 2, the third pump P3 may be a volumetric pump and / or its operation may be actively controlled to achieve a target flow rate given by a flow meter (not shown).

[0094] In the following, it is presumed that the first and third pumps Pl, P3 are controlled, in the production phase, to generate a flow rate with a respective predefined relation to the flow rate generated by the main pump P0. In the production phase, the first pump Pl is operated to maintain a first speed ratio (SRI) between the speeds of the pumps Pl, P0, and the third pump P3 is operated to maintain a second speed ratio (SR2) between the speeds of the pumps P3, P0. The composition of the second concentrate C2 as supplied into the main line 11 may vary over time. Thus, like in the FGS of FIG. 2,the second pump P2 is controlled to achieve a target value in the output signal SSI of the first sensor 15a.

[0095] FIG. 10A is a flow chart of an example method M3 of operating the FGS in FIG.

[0096] 9 in the production phase. In step S10, like in FIG. 5, the main pump P0 is operated at a production speed. In step Sil', the first pump Pl is operated at a first speed given by the first speed ratio, SRI, and the third pump P3 is operated at a second speed given by the second speed ratio, SR2. Step S 12' may be performed to retrieve a first reference conductivity and a second reference conductivity, for use in step SI 6' (below). In step S13, like in FIG. 5, the second pump P2 is operated by feedback control based on the signal SSI, to achieve a target conductivity in the signal SSI. Like in FIG. 5, step S14 may be performed to determine the reference speed of the pump P2, and optionally determine the conductivity reference value K2 pp in the signal SS2. In step S 15', by analogy with step S15 in FIG. 5, the signals SS2, SS3 are monitored in relation to a first allowable range and a second allowable range, respectively. Like in step S15, dedicated action is taken when one of the signals SS2, SS3 falls outside its allowable range. It is conceivable that the difference between the signals SS3 and SS2 is small, for example when the conductivity and / or the relative dosing amount of the concentrate C3 is small. Under these circumstances, it is currently believed to be beneficial to monitor the signal SS3 via the difference between the signals SS3 and SS2. Thus, step S 15' may include a step S 15a' of generating a difference signal representing the difference between the signals SS3 and SS2, whereby step S 15' is performed to monitor the difference signal in relation to a suitable second allowable range. It is currently believed that monitoring the difference signal yields a higher precision in detecting a malfunction of the third arrangement A3.

[0097] In step SI 6', the first and second allowable ranges are adjusted as a function of the current speed of the second pump P2, by analogy with step S16 in FIG. 5. Step S 16' may include the same steps S16a-S16b as in FIG. 5 of determining the current flow rate of the concentrate C2 (step 16a), and determining an expected value of the signal SS2 as a function of a reference conductivity value for the signal SS2 and the current flow rate of the concentrate C2 (step S 16b). Step S16b may further include a step S16b' of determining an expected value K3^p j of the signal SS3 as a function of a reference conductivity value for the signal SS3 and the current flow rate of the concentrate C3. Step SI 6b' is performed by analogy with step S16b.

[0098] In some embodiments, the expected conductivity value K3^pj is calculated in step SI 6b' according to the following equation:

[0099] K3ADJ =K3REF ■ (! + (QC3 - QC3REF^ / QPO) (4)with Qpo being the flow rate generated by the main pump PO at the production speed, QC3REF being the flow rate generated by the third pump P3 when operated at a reference speed, QQ^ being the flow rate generated by the third pump P3 at the current speed, and K3 pp being the reference conductivity value. The reference speed is thus the speed of the third pump P3 when the reference conductivity value K3 pp is attained in the signal SS3.

[0100] In step S16c', by analogy with step S16c in FIG. 5, the first allowable range is adjusted to the expected value in the signal SS2, and the second allowable range is adjusted to the expected value in the signal SS3.

[0101] The skilled person readily understands how to modify steps SI 6b'- 16c', including Eq. 4 above, if the difference signal is instead monitored by step S15a'.

[0102] FIG. 10B is a flow chart of an example method M4 of operating the FGS in FIG.

[0103] 9 in the start-up phase. The method M4 comprises steps S20, S21 and S23, as well as an optional monitoring step S22, which are all identical to the corresponding steps in FIG.

[0104] 7. The description of these steps will not be repeated. The method M4 comprises additional steps S2 T and S22'. Step S21' is performed when the pumps PO, Pl are operated at the main setup speed and the first setup speed, respectively, with the first setup speed being given by the first speed ratio SRI (corresponding to SR in FIG. 7). In step 21', the third pump P3 is operated at a second setup speed. Thereby, the FGS generates a mixture of the base fluid and the concentrates Cl, C3. In the illustrated example, step S21' comprises steps S21a'-S21c'. In step S21a', the speed of the third pump P3 is adjusted until a second setup conductivity is attained in the signal SS3 or the signal SSI, by analogy with step S21a. In step S21b', the second speed ratio SR2 is determined based on the current speeds of the pumps PO, P3 that yield the setup conductivity in step S21a', by analogy with step S21b. In step S21c', the second setup speed is set in relation to the main setup speed so as to meet the second speed ratio SR2, by analogy with step S21c. In step S21c', if necessary, the main setup speed may be changed to be equal to the production speed, with the second setup speed being set accordingly.

[0105] A monitoring step S22' may be initiated when the pumps PO, Pl, P3 are operated at their respective setup speed. Step S22' may be performed by analogy with step S22 to monitor the signal SS3 for detection of a malfunction of the third arrangement A3 while the second arrangement A2 is operated in step S23. In some embodiments, an expected conductivity value K3' DJ is calculated in step S22' according to the following equation:K3'ADJ =K3'REF ■ (! + (Qc3 - Q’C3REF) / QPO) (5)

[0106] with Qpo being the flow rate generated by the main pump PO, Q'c3REF being the flow rate generated by the third pump P3 when operated at a reference setup speed, QQ^ being the flow rate generated by the third pump P3 at the current speed, and K3' ppp being the reference setup conductivity value. The reference setup speed is the speed of the third pump P3 when K3' ppp is attained in the signal SS3. The reference setup speed may be determined together with K3'ppp, by analogy with step S14 (FIG. 5), for subsequent determination of Q'c3REF based on the reference setup speed.

[0107] In step S22', dedicated action is taken if and when the third signal SS3 falls outside the allowable range. The dedicated action may be one or more of the conceivable actions listed above for step S15.

[0108] The technique described herein is not only appliable to generation of treatment fluid for use in RRT but may be applied to generate any type of medical fluid that is generated by mixing a base fluid with at least two fluids or concentrates. Examples include medical fluids for infusion into the circulatory system of a human or animal individual. Such medical fluids include IV (intravenous) solutions. Non-limiting examples of IV solutions include sodium chloride solution 0.9 w / v%, glucose 5% w / v solution, Ringer's solution, Hartman's solution, antibiotics, anticancer drugs, etc. The presented technique is likewise applicable to medical fluids for intramuscular or subcutaneous administration.

[0109] While the subject of the present disclosure has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the subject of the present disclosure is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and the scope of the appended claims.

[0110] Further, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, parallel processing may be advantageous.

[0111] In the following, clauses are recited to summarize some aspects and embodiments as disclosed in the foregoing.

[0112] Cl. A system for generating a medical fluid, said system comprising: a main fluid path extending from a first inlet for a base fluid to an outlet for the medical fluid; a main pump in the main fluid path; a first supply pump for dosing a first fluid at a first dosingpoint upstream of the main pump in the main fluid path; a second supply pump for dosing a second fluid at a second dosing point downstream of the first dosing point and upstream of the main pump in the main fluid path; a first conductivity sensor located in the main fluid path downstream of the first and second dosing points; a second conductivity sensor located in the main fluid path intermediate the first and second dosing points; and a control arrangement for operating the system in a production phase to generate the medical fluid; wherein the control arrangement, in the production phase, is configured to: operate the main pump at a production speed; operate the first supply pump at a first speed, which is set in accordance with a predetermined speed relation to the production speed; and adjust, by feedback control, a current speed of the second supply pump to achieve a target conductivity in a first signal from the first conductivity sensor, wherein the control arrangement, in the production phase, is further configured to: monitor a second signal from the second conductivity sensor in relation to an allowable range, and take dedicated action when the second signal falls outside the allowable range, and wherein the control arrangement is configured to adjust the allowable range as a function of the current speed of the second supply pump.

[0113] C2. The system of Cl, further comprising a sub-system, which is configured to generate the second fluid by dissolving a powder concentrate in a solvent.

[0114] C3. The system of Cl or C2, wherein a concentration of the second fluid varies with temperature.

[0115] C4. The system of any preceding clause, wherein the control arrangement is configured to determine an expected value of the second signal as a function of a reference conductivity value for the second signal and a current speed of the second supply pump, and set the allowable range in relation to the expected value.

[0116] C5. The system of C4, wherein the control arrangement is configured to align the allowable range with the expected value.

[0117] C6. The system of C4 or C5, wherein the reference conductivity value is present in the second signal when the second supply pump is operated to achieve the target conductivity in the first signal while the first supply pump and the main pump are operated in accordance with the speed relation.

[0118] C7. The system of any one of C4-C6, wherein the expected value is estimated based on a flow rate generated by the main pump at the production speed, a flow rate generated by the second supply pump when operated at a reference speed that results in the reference conductivity value in the second signal, a flow rate generated by the second supply pump at the current speed, and the reference conductivity value.

[0119] C8. The system of C7, wherein the expected value is estimated by K2^p J = REF ’ (1 + QC2 ~ QC2REF^ / QPO ’ wherein QpQ is the flow rate generated bythe main pump at the production speed, Qc REF fl°wrate generated by the second supply pump when operated at the reference speed, Q 2 is the flow rate generated by the second supply pump at the current speed, and K2 pp is the reference conductivity value.

[0120] C9. The system of C7 or C8, wherein the control arrangement, in the production phase, is configured to set the reference speed to a value that is representative of the speed of the second supply pump during an initial time period of the production phase.

[0121] CIO. The system of any one of C4-C9, wherein the control arrangement, in a startup phase before the production phase, is configured to: operate the main pump at a main setup speed; operate the first supply pump at a first setup speed, which is set in accordance with the speed relation to the main setup speed; and operate the second supply pump, by said feedback control, to achieve the target conductivity in the first signal.

[0122] Cll. The system of CIO, wherein the control arrangement, while operating the second supply pump to achieve the target conductivity in the first signal, is further configured to: monitor the second signal in relation to an allowable setup range while adjusting the allowable setup range as a function of a current speed of the second supply pump, and take further dedicated action when the second signal falls outside the allowable setup range.

[0123] C12. The system of CIO or Cl 1, wherein the control arrangement, in the start-up phase, is configured to, before operating the first supply pump at the first setup speed: operate the first supply pump, by further feedback control, to achieve a setup conductivity in the first or second signal; determine the speed relation based on the main setup speed and a resulting speed of the first supply pump; and determine the first setup speed of the first supply pump based on the thus-determined speed relation.

[0124] C13. The system of any one of C10-C12, wherein the control arrangement, in the production phase, is configured to set the reference conductivity value to a conductivity value that is present in the second signal when the target conductivity is achieved in the first signal in the start-up phase.

[0125] C14. The system of any preceding clause, wherein the dedicated action, and optionally the further dedicated action, comprises at least one of: perform a diversion operation, in which a valve arrangement in the main fluid path downstream of the main pump is operated to open the main fluid path to a drain path and close the main fluid path towards the outlet; generate a warning or instruction for a user of the system via a feedback device; or stop the main pump, the first supply pump and the second supply pump.C15. The system of any preceding clause, further comprising a third supply pump for dosing a third fluid at a third dosing point intermediate the first and second dosing points in the main fluid path, and a third conductivity sensor located in the main fluid path downstream of the third dosing point and intermediate the first and second dosing points.

[0126] Cl 6. The system of Cl 5, wherein the control arrangement, in the production phase, is further configured to: operate the third supply pump at a second speed, which is set in accordance with a predetermined second speed relation to the production speed; and monitor a third signal from the third conductivity sensor in relation to a further allowable range and take dedicated action when the third signal falls outside the further allowable range, wherein the control arrangement is configured to adjust the further allowable range as a function of the current speed of the second supply pump.

[0127] C17. The system of C16 in combination with CIO, wherein the control arrangement is further configured to, in the start-up phase before operating the second supply pump to achieve the target conductivity in the first signal: operate the second supply pump at a second setup speed, which is set in accordance with the second speed relation to the main setup speed.

[0128] Cl 8. The system of C17 or C17, wherein the control arrangement is configured to monitor the third signal by monitoring a difference signal between the third signal and the second signal, and wherein the further allowable range is defined for the difference signal.

[0129] Cl 9. The system of any preceding clause, wherein the first supply pump is a volumetric pump.

[0130] C20. The system of any preceding clause, wherein the main pump is configured to generate a stable flow rate.

[0131] C21. A computer-implemented method of operating a system for generating a medical fluid, said system comprising: a main fluid path extending from a first inlet for a base fluid to an outlet for the medical fluid; a main pump in the main fluid path; a first supply pump for dosing a first fluid at a first dosing point upstream of the main pump in the main fluid path; a second supply pump for dosing a second fluid at a second dosing point downstream of the first dosing point and upstream of the main pump in the main fluid path; a first conductivity sensor located in the main fluid path downstream of the first and second dosing points; and a second conductivity sensor located in the main fluid path intermediate the first and second dosing points; said method comprising, while the system is in a production phase to generate the medical fluid: operating the main pump at a production speed; operating the first supply pump at a first speed, which is set in accordance with a predetermined speed relation to the production speed;adjusting, by feedback control, a current speed of the second supply pump to achieve a target conductivity in a first signal from the first conductivity sensor; monitoring a second signal from the second conductivity sensor in relation to an allowable range, wherein dedicated action is taken when the second signal falls outside the allowable range; and adjusting the allowable range as a function of the current speed of the second supply pump.

[0132] C22. A computer-readable medium comprising program instructions, which when executed by a processor circuitry causes the processor circuitry to perform the method according to C21.

Claims

24CLAIMS1. A system for generating a medical fluid, said system comprising:a main fluid path (11) extending from a first inlet (11') for a base fluid to an outlet (11") for the medical fluid,a main pump (P0) in the main fluid path (11),a first supply pump (Pl) for dosing a first fluid at a first dosing point (DPa) upstream of the main pump (P0) in the main fluid path (11),a second supply pump (P2) for dosing a second fluid at a second dosing point (DPb) downstream of the first dosing point (DPa) and upstream of the main pump (P0) in the main fluid path (11),a first conductivity sensor (15a) located in the main fluid path (11) downstream of the first and second dosing points (DPa, DPb),a second conductivity sensor (15b) located in the main fluid path (11) intermediate the first and second dosing points (DPa, DPb), anda control arrangement (100) for operating the system in a production phase to generate the medical fluid,wherein the control arrangement (100), in the production phase, is configured to: operate (S10) the main pump (P0) at a production speed; operate (Sil) the first supply pump (Pl) at a first speed, which is set in accordance with a predetermined speed relation to the production speed; and adjust (S13), by feedback control, a current speed of the second supply pump (P2) to achieve a target conductivity in a first signal (SSI) from the first conductivity sensor (15a),wherein the control arrangement (100), in the production phase, is further configured to: monitor (S15) a second signal (SS2) from the second conductivity sensor (15b) in relation to an allowable range, and take dedicated action when the second signal (SS2) falls outside the allowable range, andwherein the control arrangement (100) is configured to adjust (SI 6) the allowable range as a function of the current speed of the second supply pump (P2).

2. The system of claim 1, further comprising a sub-system (17), which is configured to generate the second fluid by dissolving a powder concentrate (C2) in a solvent.

3. The system of claim 1 or 2, wherein a concentration of the second fluid varies with temperature.

4. The system of any preceding claim, wherein the control arrangement (100) is configured to determine (S16a-S16b) an expected value of the second signal (SS2) as a function of a reference conductivity value for the second signal (SS2) and a current speed of the second supply pump (P2), and set (S16c) the allowable range in relation to the expected value.

5. The system of claim 4, wherein the control arrangement (100) is configured to align the allowable range with the expected value.

6. The system of claim 4 or 5, wherein the reference conductivity value is present in the second signal (SS2) when the second supply pump (P2) is operated to achieve the target conductivity in the first signal (SSI) while the first supply pump (Pl) and the main pump (P0) are operated in accordance with the speed relation.

7. The system of any one of claims 4-6, wherein the expected value is estimated based on a flow rate generated by the main pump (P0) at the production speed, a flow rate generated by the second supply pump (P2) when operated at a reference speed that results in the reference conductivity value in the second signal (SS2), a flow rate generated by the second supply pump (P2) at the current speed, and the reference conductivity value.

8. The system of claim 7, wherein the expected value is estimated by K2^p J = REF ’ (1 + QC2 ~ QC2REF^ / QPO ’ wherein QpQ is the flow rate generated by the main pump (P0) at the production speed, Qc2REF 'sA°w rate generated by the second supply pump (P2) when operated at the reference speed, Qp2 isthe flow rate generated by the second supply pump (P2) at the current speed, and K2 pp is the reference conductivity value.

9. The system of claim 7 or 8, wherein the control arrangement (100), in the production phase, is configured to set (S14) the reference speed to a value that is representative of the speed of the second supply pump (P2) during an initial time period of the production phase.

10. The system of any one of claims 4-9, wherein the control arrangement (100), in a start-up phase before the production phase, is configured to:operate (S20) the main pump (P0) at a main setup speed;operate (S21) the first supply pump (Pl) at a first setup speed, which is set in accordance with the speed relation to the main setup speed; andoperate (S23) the second supply pump (P2), by said feedback control, to achieve the target conductivity in the first signal (SSI).

11. The system of claim 10, wherein the control arrangement (100), while operating the second supply pump (P2) to achieve the target conductivity in the first signal (SSI), is further configured to: monitor (S22) the second signal (SS2) in relation to an allowable setup range while adjusting (S22a) the allowable setup range as a function of a current speed of the second supply pump (P2), and take further dedicated action when the second signal (SS2) falls outside the allowable setup range.

12. The system of claim 10 or 11, wherein the control arrangement (100), in the start-up phase, is configured to, before operating the first supply pump (Pl) at the first setup speed: operate (S21a) the first supply pump (Pl), by further feedback control, to achieve a setup conductivity in the first or second signal (SSI, SS2); determine (S21b) the speed relation based on the main setup speed and a resulting speed of the first supply pump (Pl); and determine (S21c) the first setup speed of the first supply pump (Pl) based on the thus-determined speed relation.

13. The system of any one of claims 10-12, wherein the control arrangement (100), in the production phase, is configured to set (S12) the reference conductivity value to a conductivity value that is present in the second signal (SS2) when the target conductivity is achieved in the first signal (SSI) in the start-up phase.

14. The system of any preceding claim, wherein the dedicated action, and optionally the further dedicated action, comprises at least one of: perform a diversion operation, in which a valve arrangement (13) in the main fluid path (11) downstream of the main pump (P0) is operated to open the main fluid path (11) to a drain path (12) and close the main fluid path (11) towards the outlet (11"); generate a warning or instruction for a user of the system via a feedback device (110); or stop the main pump (P0), the first supply pump (Pl) and the second supply pump (P2).

15. The system of any preceding claim, further comprising a third supply pump (P3) for dosing a third fluid at a third dosing point (DPc) intermediate the first and second dosing points (DPa, DPb) in the main fluid path (11), and a third conductivity27sensor (15c) located in the main fluid path (11) downstream of the third dosing point (DPc) and intermediate the first and second dosing points (DPa, DPb).

16. The system of claim 15, wherein the control arrangement (100), in the production phase, is further configured to:operate (Sil') the third supply pump (P3) at a second speed, which is set in accordance with a predetermined second speed relation to the production speed; and monitor (S 15') a third signal (SS3) from the third conductivity sensor (15c) in relation to a further allowable range and take dedicated action when the third signal (SS3) falls outside the further allowable range,wherein the control arrangement (100) is configured to adjust (SI 6') the further allowable range as a function of the current speed of the second supply pump (P2).

17. The system of claim 16 in combination with claim 10, wherein the control arrangement (100) is further configured to, in the start-up phase before operating (S23) the second supply pump (P2) to achieve the target conductivity in the first signal (SSI): operate (S2T) the second supply pump (P3) at a second setup speed, which is set in accordance with the second speed relation to the main setup speed.

18. The system of claim 16 or 17, wherein the control arrangement (100) is configured to monitor (S 15'; S22') the third signal (SS3) by monitoring (S 15a') a difference signal between the third signal (SS3) and the second signal (SS2), and wherein the further allowable range is defined for the difference signal.

19. The system of any preceding claim, wherein the first supply pump (Pl) is a volumetric pump.

20. The system of any preceding claim, wherein the main pump (P0) is configured to generate a stable flow rate.

21. A computer-implemented method of operating a system for generating a medical fluid, said system comprising: a main fluid path extending from a first inlet for a base fluid to an outlet for the medical fluid; a main pump in the main fluid path; a first supply pump for dosing a first fluid at a first dosing point upstream of the main pump in the main fluid path; a second supply pump for dosing a second fluid at a second dosing point downstream of the first dosing point and upstream of the main pump in the main fluid path; a first conductivity sensor located in the main fluid path downstream of thefirst and second dosing points; and a second conductivity sensor located in the main fluid path intermediate the first and second dosing points; said method comprising, while the system is in a production phase to generate the medical fluid:operating (S10) the main pump (PO) at a production speed;operating (Sil) the first supply pump (Pl) at a first speed, which is set in accordance with a predetermined speed relation to the production speed;adjusting (S13), by feedback control, a current speed of the second supply pump (P2) to achieve a target conductivity in a first signal (SSI) from the first conductivity sensor (15a);monitoring (S15) a second signal (SS2) from the second conductivity sensor (15b) in relation to an allowable range, wherein dedicated action is taken when the second signal (SS2) falls outside the allowable range; andadjusting (SI 6) the allowable range as a function of the current speed of the second supply pump (P2).

22. A computer-readable medium comprising program instructions, which when executed by a processor circuitry (101) causes the processor circuitry (101) to perform the method according to claim 21.

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