Patent Description:
Extracorporeal blood treatment, such as hemodialysis, is performed by an apparatus that is configured to supply one or more fluids for use in the treatment. Equipment that is exposed to blood during treatment is typically replaced after each treatment. Such disposable equipment may include a dialyzer and a line set with tubing for defining an extracorporeal blood circuit for conducting blood from a patient, through the dialyzer and back to the patient. During a treatment session, the extracorporeal circuit is connected to the patient at a withdrawal end and a return end, respectively, and a blood pump of the apparatus is operated to pump the patient's blood through the blood circuit while one or more pressure sensors of the apparatus are connected in fluid communication with the line set to monitor the pressure in the blood circuit.

Conventionally, at the end of a blood treatment session, the blood pump is stopped and a so-called rinseback procedure is initiated. Attending staff disconnects the withdrawal end from the patient and connects it to a bag containing a physiological saline solution, whereupon the blood pump is operated so that the saline solution pushes most of the blood present in the blood circuit back into the patient. Then, when the blood pump is stopped, attending staff may disconnect the return end from the patient and place the disposable equipment in a special container for contaminated waste. To reduce weight, the staff may first carry the dialyzer, the line set and the bag to a nearby sink or container for draining of remaining fluid. Alternatively, the attending staff may start a draining procedure on the apparatus, whereby the apparatus operates the blood pump to pump remaining fluid through the return connector into the nearby sink or container.

This conventional procedure involves a considerable risk of blood and blood-containing saline solution being spilled on the apparatus and its surroundings.

The prior art comprises <CIT> which proposes to procedure for draining the blood circuit via the dialyzer by use of a specialized line set. In contrast to conventional line sets, the specialized line set includes a dedicated branch tube which is terminated by a connector that is specifically configured for interconnection with a connector on the return end of the line set. After rinseback and while the withdrawal end is connected to a flexible bag of saline solution, the caretaker connects the connector on the branch tube to the connector on the return end so as to form a closed loop. The apparatus then operates the blood pump to circulate the remaining fluid in the closed loop and controls one or more of its dialysis fluid pumps to create a pressure gradient over the membrane of the dialyzer, so as to drive the remaining liquid through the membrane into the apparatus for safe disposal. To benefit from the technique proposed in <CIT>, dialysis clinics are required to acquire and keep in stock the specialized line set. This is undesirable from a logistic point of view and increases operating cost and internal handling and storage at the dialysis clinics. Further, it is currently believed that it may be difficult to ensure a sufficient drainage of the blood circuit by use of the proposed line set and the associated draining procedure.

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

A further objective is to provide a technique that enables draining of the blood circuit after completed blood treatment by use of a conventional line set.

Another objective is to facilitate or improve automated draining of the blood circuit.

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 control system, a blood treatment apparatus, a method and a computer readable medium in accordance with first and second inventive concepts as defined by the independent claims, embodiments thereof being defined by dependent claims.

A first aspect is a control system for a blood treatment apparatus. The blood treatment apparatus comprises a fluid supply unit and is configured for installation of a dialyzer and a line set to define a first flow circuit for conducting a fluid provided by the fluid supply unit through the dialyzer and back to the fluid supply unit, and to define a second flow circuit which is separated from the first flow circuit by a semi-permeable membrane of the dialyzer and comprises return and withdrawal lines for connection to a vascular system of a subject during a blood treatment session. The control system is configured to, subsequent to a termination of the blood treatment session: instruct an operator to connect the second flow circuit to a first port of a container that holds a human-compatible fluid; operate the blood treatment apparatus to push remaining blood in the second flow circuit into the vascular system of the subject through the return line while admitting the human-compatible fluid from the container into the second flow circuit; instruct the operator to disconnect the return line from the vascular system of the subject and re-arrange the second flow circuit to define a closed loop; and operate, in a draining phase, the blood treatment apparatus to draw residual liquid from the closed loop into the first flow circuit through the semi-permeable membrane of the dialyzer.

In accordance with the first inventive concept, the control system is further configured to instruct the operator to re-arrange the second flow circuit by connecting the second flow circuit to a second port of the container so that the container is included in the closed loop.

Generally, the first inventive concept enables the second flow circuit and the container to be substantially drained of residual fluid in the draining phase by a combination of automated control and operator instructions. According to the first inventive concept, the second flow circuit is connected in fluid communication with two separate ports of the container in the draining phase. Such use of a container that has more than one port enables the closed loop to be formed by a simple and conventional line set. For example, the ports on the container may be configured for connection, directly or indirectly, to any two suitable existing connectors of such a conventional line set, e.g. terminal connectors on the ends of the withdrawal and return lines. Further, by arranging the container within the closed loop, the residual fluid is circulated through the container in the draining phase, which serves to counteract the formation of obstructions to the flow within the container or at the ports. Thereby, the first inventive concept also improves the ability of the blood treatment apparatus to perform an automated draining of the second flow circuit.

In some embodiments of the control system of the first inventive concept, in the closed loop, the withdrawal line is connected in fluid communication with the first port of the container and the return line is connected in fluid communication with the second port of the container.

In some embodiments of the control system of the first inventive concept, in the closed loop, terminating connectors on the withdrawal and return lines are connected, directly or indirectly, to the first and second ports, respectively, of the container.

In some embodiments of the control system of the first inventive concept, the control system is further configured to, in the draining phase, operate the blood treatment apparatus to circulate the residual liquid in the closed loop, and thus through the container.

In accordance with the second inventive concept, the control system further is configured to instruct the operator to re-arrange the second flow circuit by connecting the return and withdrawal lines in fluid communication with the first port of the container through a three-way manifold coupling unit.

Generally, the second inventive concept enables the closed loop to be formed by a simple and conventional line set since the three-way manifold coupling unit, when connected to the first port of the container, provides two ports for connection, directly or indirectly, to any two existing connectors of a conventional line set, e.g. terminal connectors on the ends of the withdrawal and return lines.

In some embodiments of the control system of the second inventive concept, in the closed loop, a first port of the three-way manifold coupling unit is connected in fluid communication with the first port of the container, a second port of the three-way manifold coupling unit is connected in fluid communication with the withdrawal line, and a third port of the three-way manifold coupling unit is connected in fluid communication with the return line.

In some embodiments of the control system of the second inventive concept, the control system is further configured to, in the draining phase, operate the blood treatment apparatus to circulate the residual liquid in the closed loop.

In the following, further embodiments of the control system are defined and are applicable to both of the first and second inventive concepts. These embodiments provide at least some of the technical effects and advantages described in the foregoing, as well as additional technical effects and advantages as readily understood by the skilled person in view of the following detailed description.

In some embodiments, the control system is further configured to, in the draining phase, operate a clamp of the blood treatment apparatus to selectively open a branch line, which is included in the line set and is arranged in fluid communication with the second flow circuit, so as to ventilate the closed loop.

In some embodiments, the control system is configured to, during the draining phase, operate the clamp to keep the branch line open and only intermittently close the branch line.

In some embodiments, the control system is configured to, in the draining phase, operate the clamp to repeatedly close the branch line, e.g. for <NUM>-<NUM> seconds, and preferably for <NUM>-<NUM> seconds.

In some embodiments, the control system is configured to, when terminating the draining phase, operate the clamp to close the branch line, operate the blood treatment apparatus to generate a sub-atmospheric pressure in the thus-closed branch line, and operate the clamp to open the branch line to release the sub-atmospheric pressure.

In some embodiments, one of the return and withdrawal lines is arranged in the clamp during the blood treatment session, and the control system is further configured to, before the draining phase, instruct the operator to remove said one of the return and withdrawal lines from the clamp and install the branch line in the clamp.

In some embodiments, the branch line is branched from the withdrawal line.

In some embodiments, the control system is further configured to, before the draining phase, instruct the operator to disconnect the branch line from a sensor port of the blood treatment apparatus.

In some embodiment, the return line is arranged in the clamp and the withdrawal line is arranged in a further clamp of the blood treatment apparatus during the blood treatment session, the branch line is branched from the withdrawal line downstream of the further clamp, and the control system is further configured to, before the draining phase, instruct the operator to remove the return line from the clamp, install the branch line in the clamp, and instruct the operator to disconnect the branch line from a sensor port of the blood treatment apparatus, wherein the control system is further configured to, before instructing the operator to disconnect the branch line, close the further clamp and operate the blood treatment apparatus to generate a sub-atmospheric pressure in the withdrawal line downstream of the further clamp and in the branch line.

In some embodiments, the fluid supply unit defines a drain flow path which extends from an inlet port for connection to the first flow circuit to a drain pump, wherein the drain flow path comprises a set of sensors and an inlet valve intermediate the inlet port and the set of sensors, wherein the fluid supply unit further defines a supply flow path, which comprises an outlet valve and extends from a supply pump to an outlet port for connection to the first flow circuit, and wherein the control system is further configured to, in the draining phase: close the outlet and inlet valves; open a valve located in a connecting line, which extends between a first location in the drain flow path intermediate the inlet port and the inlet valve and a second location in the drain flow path intermediate the drain pump and the set of sensors; and operate the drain pump to draw the residual liquid from the closed loop into the first flow circuit through the semi-permeable membrane of the dialyzer and from the first flow circuit into the drain flow path via the inlet port.

In some embodiments, the connecting line extends from a degassing device in the drain flow path, and wherein the control system is further configured to, during the blood treatment session, open the valve in the connecting line to expel gases from the degassing device through the connecting line.

In some embodiments, the control system is further configured to, in the draining phase: open a bypass valve in a bypass line, which extends between a third location in the drain flow path intermediate the inlet valve and the second location, and a fourth location in the supply flow path intermediate the supply pump and the outlet valve, so as to establish fluid communication between the inlet port and a pressure sensor in the supply flow path; and control the drain pump based on a pressure signal from the pressure sensor.

A second aspect is a blood treatment machine comprising a fluid supply unit configured to supply a fluid to a first flow circuit, a pump operable to engage with a second flow circuit, and the control system in accordance with the first or second inventive concept or any embodiment thereof.

A third aspect is a method of operating a blood treatment apparatus that comprises a fluid supply unit and is configured for installation of a dialyzer and a line set to define a first flow circuit for conducting a fluid provided by the fluid supply unit through the dialyzer and back to the fluid supply unit, and to define a second flow circuit which is separated from the first flow circuit by a semi-permeable membrane of the dialyzer and comprises return and withdrawal lines for connection to a vascular system of a subject during a blood treatment session. The method comprises, subsequent to a rinseback procedure and while the withdrawal line is connected to a first port of a container and when the return line has been disconnected from the vascular system of the subject: causing a re-arrangement of the second flow circuit to define a closed loop; and operating, in a draining phase, the blood treatment apparatus to draw residual liquid from the closed loop into the first flow circuit through the semi-permeable membrane of the dialyzer.

In the method of the first inventive concept, the re-arrangement comprises connecting the second flow circuit to a second port of the container so that the container is included in the closed loop.

In some embodiments of the method of the first inventive concept, the re-arrangement comprises connecting the withdrawal line in fluid communication with the first port of the container and connecting the return line in fluid communication with the second port of the container.

In some embodiments of the method of the first inventive concept, the re-arrangement comprises connecting terminating connectors on the withdrawal and return lines, directly or indirectly, to the first and second ports, respectively, of the container.

In some embodiments, the method of the first inventive concept further comprises: operating, in the draining phase, the blood treatment apparatus to circulate the residual liquid in the closed loop, and thus through the container.

In the method of the second inventive concept, the re-arrangement comprises connecting the return and withdrawal lines in fluid communication with the first port of the container through a three-way manifold coupling unit.

In some embodiments of the method of the second inventive concept, the re-arrangement results in a first port of the three-way manifold coupling unit being connected in fluid communication with the first port of the container, a second port of the three-way manifold coupling unit being connected in fluid communication with the withdrawal line, and a third port of the three-way manifold coupling unit being connected in fluid communication with the return line.

In some embodiments, the method of the second inventive concept further comprises, in the draining phase, operating the blood treatment apparatus to circulate the residual liquid in the closed loop.

In the following, further embodiments of the method are defined and are applicable to both of the first and second inventive concepts.

In some embodiments, the method further comprises, in the draining phase, operating a clamp to selectively open a branch line, which is included in the line set and is arranged in fluid communication with the second flow circuit, so as to ventilate the closed loop.

In some embodiments, the method comprises, during the draining phase, operating the clamp to keep the branch line open and only intermittently closing the branch line.

In some embodiments, the method further comprises, in the draining phase, operating the clamp to repeatedly close the branch line, e.g. for <NUM>-<NUM> seconds, and preferably for <NUM>-<NUM> seconds.

In some embodiments, the method further comprises, when terminating the draining phase: operating the clamp to close the branch line; operating the blood treatment apparatus to generate a sub-atmospheric pressure in the thus-closed branch line; operating the clamp to open the branch line to release the sub-atmospheric pressure.

In some embodiments of the method, one of the return and withdrawal lines is arranged in the clamp during the blood treatment session, and the method further comprises, before the draining phase, removing said one of the return and withdrawal lines from the clamp and installing the branch line in the clamp.

In some embodiment of the method, the branch line is branched from the withdrawal line.

In some embodiments, the method further comprises, before the draining phase, disconnecting the branch line from a sensor port of the blood treatment apparatus.

In some embodiments, the return line is arranged in the clamp and the withdrawal line is arranged in a further clamp of the blood treatment apparatus during the blood treatment session, and the branch line is branched from the withdrawal line downstream of the further clamp, wherein the method further comprises, before the draining phase, removing the return line from the clamp, installing the branch line in the clamp, and disconnecting the branch line from a sensor port of the blood treatment apparatus, and wherein the method further comprises, before said disconnecting the branch line, closing the further clamp and operating the blood treatment apparatus to generate a sub-atmospheric pressure in the withdrawal line downstream of the further clamp and in the branch line.

In some embodiments of the method, the fluid supply unit is configured to define a drain flow path, which extends from an inlet port for connection to the first flow circuit to a drain pump and which comprises a set of sensors and an inlet valve intermediate the inlet port and the set of sensors, and a supply flow path, which comprises an outlet valve and extends from a supply pump to an outlet port for connection to the first flow circuit, and the method further comprises, in the draining phase: closing the outlet and inlet valves; opening a valve located in a connecting line, which extends between a first location in the drain flow path intermediate the inlet port and inlet valve and a second location in the drain flow path intermediate the drain pump and the set of sensors; and operating the drain pump to draw the residual liquid from the closed loop into the first flow circuit through the semi-permeable membrane of the dialyzer and from the first flow circuit into the drain flow path via the inlet port.

In some embodiments of the method, the connecting line extends from a degassing device in the drain flow path, and the method further comprises, during the blood treatment session, opening the valve in the connecting line to expel gases from the degassing device through the connecting line.

In some embodiments, the method further comprises, in the draining phase: opening a bypass valve in a bypass line, which extends between a third location in the drain flow path intermediate the inlet valve and the second location and a fourth location in the supply flow path intermediate the supply pump and the outlet valve, so as to establish fluid communication between the inlet port and a pressure sensor in the supply flow path; and controlling the drain pump based on a pressure signal from the pressure sensor.

A fourth aspect is a computer-readable medium comprising computer instructions which, when executed by a processor, cause the processor to perform the method in accordance with the first or second inventive concept or any embodiment thereof.

Still other objectives, features, embodiments, aspects and advantages of the present invention may appear from the following detailed description, from the attached claims as well as from the drawings.

Embodiments of the invention will now be described in more detail with reference to the accompanying drawings.

Embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, the invention being defined by the appended claims. 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 of the invention, which is defined by the appended claims.

In the following, embodiments of the invention will be exemplified with reference to an apparatus configured for treatment of renal failure, denoted "dialysis machine" below.

<FIG> shows an example of such a dialysis machine <NUM>, which is operable to perform a dialysis treatment when combined with a set of disposable products or "disposables" to be described below with reference to <FIG>. The dialysis machine <NUM> in <FIG> is also known as "monitor" and defines a machine chassis that exposes holders for mounting the disposable(s) in operative engagement with components such as connectors, pumps, sensors, clamps, etc. The disposables are exposed to circulating blood and are typically for single-use, i.e. they are discarded after each treatment session.

In the illustrated example, a control system or controller <NUM> in the machine <NUM> is configured to synchronize and control the operation of the components of the machine <NUM>, e.g. by electric control signals. The operation of the control system <NUM> may be at least partly controlled by software instructions that are supplied on a computer-readable medium for execution by a processor 2A in conjunction with a memory 2B in the control system <NUM>. A display unit <NUM> is operable to provide information and instructions for an operator, such as a nurse, a physician or a patient. The machine <NUM> may also enable the operator to enter data into the machine, e.g. via mechanical buttons (not shown) or virtual buttons on a touch panel, e.g. in the display unit <NUM>. A fluid supply unit <NUM> is configured to supply one or more suitable fluids during operation of the machine <NUM>. Such fluids may include one of more of a treatment fluid (dialysis fluid) for use during blood treatment, a disinfectant for use in disinfection of the machine between treatments, a saline solution, and purified water. The fluids may be supplied from replaceable containers attached to the machine <NUM> or may be generated on demand by the machine <NUM> or another apparatus in fluid communication with the machine <NUM>. In the illustrated example, the machine comprises machine ports <NUM>, <NUM>, <NUM>', <NUM>' in fluid connection to the supply unit <NUM>. The machine ports <NUM>, <NUM> are input and output ports, respectively, for a human-compatible fluid such as a treatment fluid, saline solution or water, whereas the machine ports <NUM>', <NUM>' are input and output ports, respectively, for a disinfectant. The machine <NUM> further comprises a holder <NUM> for a dialyzer (<NUM> in <FIG>), a machine-controlled peristaltic pump ("blood pump") <NUM> for engagement with a withdrawal line (<NUM>" in <FIG>), and a holder <NUM> for a drip chamber (<NUM> in <FIG>), and two machine-controlled clamps <NUM>, <NUM>. Further, a holder <NUM> is provided for a container (<NUM> in <FIG>). The machine <NUM> also comprises sensor ports <NUM>, <NUM> in fluid communication with pressure sensors (not shown) within the machine <NUM>. The skilled person realizes that the machine <NUM> may comprise further components that are not shown in FIG. 1A, e.g. a blood detector, an injection system for anticoagulant, etc..

<FIG> illustrates a dialysis machine <NUM>, e.g. as shown in <FIG>, which is connected to a set of disposables and operated for hemodialysis treatment of a subject S, in this example a human patient. The set of disposables includes a dialyzer <NUM>, which is a blood filtration unit configured for fluid connection to a line set (below) and for fluid connection to the machine ports <NUM>, <NUM>. A semi-permeable membrane <NUM> ("dialyzer membrane") is arranged inside the housing of the dialyzer <NUM> to separate a first chamber ("dialysis fluid side compartment") <NUM> from a second chamber ("blood side compartment") <NUM>. The first and second chambers <NUM>, <NUM> are configured to be perfused by blood and dialysis fluid, respectively, during blood treatment. The set of disposables further includes fluid-conducting devices in the form of first and second line arrangements 24A, 24B, which are collectively known as a "line set" in the art. The first line arrangement 24A comprises a drip chamber <NUM> and flexible tubing that defines a flow path extending from a first end with a dialyzer connector to a second end having a terminal connector <NUM>. In the following, the tubing <NUM>' that extends to the terminal connector <NUM> is denoted "return line". The second line arrangement 24B comprises flexible tubing that defines a flow path from a first end with a terminal connector <NUM> to a second end with a dialyzer connector. In the following, the tubing <NUM>" that extends to the terminal connector <NUM> is denoted "withdrawal line". The line arrangements 24A, 24B and the dialyzer <NUM> may be provided as separate components that are interconnected before use, or they may be delivered as a preassembled unit. Although not shown in <FIG>, each of the line arrangements 24A, 24B may include further components, such as one or more manual clamps, one or more branch lines for dedicated use such as connection to a pressure sensor (cf. sensor ports <NUM>, <NUM> in <FIG>), infusion of anticoagulant, replacement fluid, etc..

As understood from <FIG>, the disposables have been mounted to the machine <NUM> by attaching the dialyzer <NUM> to holder <NUM> (<FIG>) and the drip chamber <NUM> to holder <NUM> (<FIG>), by arranging the withdrawal line <NUM>" for engagement with pump <NUM> and clamp <NUM> ("withdrawal clamp"), and by arranging the return line <NUM>' for engagement with clamp <NUM> ("return clamp"). The set of disposables is connected for fluid communication with the dialysis machine <NUM> so as to define a first flow circuit C1 ("dialysis fluid circuit") for dialysis fluid supplied by the dialysis machine <NUM> and a second flow circuit C2 ("extracorporeal blood circuit") which is connected to the vascular system of the subject S. Specifically, the dialyzer <NUM> is connected by a supply line <NUM>' and a drain line <NUM>" to establish fluid communication between the first chamber <NUM> and the ports <NUM>, <NUM>, thereby forming the first flow circuit C1. Further, the dialyzer <NUM> is connected for establishing fluid communication between the second chamber <NUM> and the line arrangements 24A, 24B, thereby forming the second flow circuit C2. During blood treatment, the terminal connectors <NUM>, <NUM> are connected to a blood vessel access of the subject S. As is well-known in the art, the blood vessel access (also known as "vascular access") may be a fistula, graft or catheter, and the terminal connectors <NUM>, <NUM> may be connected to the blood vessel access by any conventional device, including needles or catheters.

<FIG> also illustrates fluid lines <NUM>, <NUM> that extend inside the machine <NUM> from the fluid supply unit <NUM> (<FIG>) to the ports <NUM>, <NUM>, via machine-operated outlet and inlet valves <NUM>, <NUM> for selectively opening and closing the ports <NUM>, <NUM>. In the following, filled and non-filled valve symbols indicate that a valve is open and closed, respectively.

In <FIG>, the machine <NUM> is operated by the control system <NUM> (<FIG>) to open the valves <NUM>, <NUM> and establish a flow of dialysis fluid through the first chamber <NUM> of the dialyzer <NUM>, as indicated by arrows. The machine <NUM> is also operated by the control system <NUM> to open clamps <NUM>, <NUM> and run pump <NUM> so that blood is drawn from the vascular system of the subject S along line arrangement 24B, pushed through the second chamber <NUM> of the dialyzer <NUM> and back to the vascular subject S along line arrangement 24A, as indicated by arrows, while the blood is being subjected to dialysis treatment in the dialyzer <NUM>. Dialysis treatment as such is well-known to the person skilled in the art and will not be described in detail herein.

When dialysis treatment is completed, it is common practice to return all or most of the blood remaining in the second flow circuit C2 to the vascular system of the subject S. This process is known as "rinseback" or "reinfusion" and involves pushing at least a portion of the remaining blood into the subject S while introducing a rinseback fluid into the second flow circuit C2. After rinseback, the second flow circuit C2 contains a residual fluid in the form of a mixture of rinseback fluid and blood. Embodiments of the invention aim at facilitating disposal of the residual fluid.

In the following, an embodiment of a first inventive concept will be described with reference to the flow chart in <FIG> in combination with system diagrams in <FIG>, which illustrate a dialysis machine <NUM> when arranged and operated for rinseback and drainage of residual fluid, respectively. The flow chart in <FIG> represents a post-treatment procedure <NUM> that includes rinseback, a draining phase and removal of disposables. Each of the steps <NUM>-<NUM> of the method <NUM> may be controlled by the control system <NUM> of the dialysis machine <NUM>. To the extent that a step involves a manual operation, the control system <NUM> may generate and present corresponding instructions for the operator, e.g. on the display <NUM>, and may also require the operator to confirm when the manual operation has been completed, e.g. by pressing or touching a button on the machine <NUM>. However, it also conceivable that one or more of the steps are independently performed by the operator based on written instructions, e.g. from an operations manual or work guide, without involvement of the control system <NUM>.

The procedure <NUM> is initiated after termination of the dialysis treatment in <FIG>. The dialysis treatment may be terminated by the machine <NUM> stopping the blood pump <NUM>, closing the clamps <NUM>, <NUM>, and closing the valves <NUM>, <NUM>. In a rinseback step <NUM>, the operator connects a container <NUM>, which contains a human-compatible fluid ("rinseback fluid"), to the second flow circuit C2 and the machine <NUM> is operated to perform the above-mentioned rinseback. The rinseback fluid may be any fluid, which by its composition is compatible with the human body if administered to its circulatory system in relevant amounts, including but not limited to a saline solution, a treatment fluid, and water.

As shown in <FIG>, the rinseback fluid is held within an internal space <NUM> of the container <NUM>, which comprises an outlet port <NUM> and an inlet port <NUM> in fluid communication with the internal space <NUM>. The container <NUM> may be made of rigid or flexible material, preferably a transparent or translucent material that allows for ocular inspection of the contents in the container <NUM>. In the illustrated example, the container <NUM> further defines a suspension hole <NUM>.

In the example of <FIG>, step <NUM> involves instructing the operator to disconnect the terminal connector <NUM> from the vascular access of the subject S and connect the terminal connector <NUM> to the outlet port <NUM> of the container <NUM>. The dialysis machine <NUM> then opens clamps <NUM>, <NUM> and operates pump <NUM> to push the remaining in the second flow circuit C2 into the subject S while drawing rinseback fluid from the container <NUM> into the withdrawal line <NUM>", as indicated by arrows in <FIG>, until all or a majority of the remaining blood in the second flow circuit C2 has been returned to the subject S. The machine <NUM> then stops pump <NUM> and closes clamps <NUM>, <NUM>. The rinseback may be terminated manually by the operator or automatically by the machine <NUM> based on input from a dedicated sensor (not shown).

In a re-arrangement step <NUM>, which is performed after termination of the rinseback step <NUM>, the operator is instructed to re-arrange the second flow circuit C2 to form a closed loop that includes the container <NUM>. In the example of <FIG>, the closed loop is formed by connecting the terminal connector <NUM> on the return line <NUM>' to the inlet port <NUM> of the container <NUM>.

After step <NUM>, the machine <NUM> enters a draining phase that includes a circulation step <NUM> and a filtration step <NUM>.

In the circulation step <NUM>, the machine <NUM> is operated to open clamps <NUM>, <NUM> and start pump <NUM> to circulate the residual fluid in (along) the closed loop, as indicated by arrows in <FIG>. The residual fluid is composed of remaining rinseback fluid in the container <NUM> and a mixture of rinseback fluid and blood residues in the line arrangements 24A, 24B and in the second chamber <NUM> of the dialyzer <NUM>.

In the filtration step <NUM>, the machine <NUM> is operated to draw residual fluid from the second flow circuit C2 into the first flow circuit C1 through the membrane <NUM>, and from the first flow circuit C1 into the drain line <NUM> of the machine <NUM>, as indicated by arrows in <FIG>. This process, denoted "filtration" herein, may be achieved by controlling the machine <NUM> to generate a lower pressure in the first chamber <NUM> compared to the second chamber <NUM>. In the illustrated example, inlet valve <NUM> is opened, outlet valve <NUM> is closed and the fluid supply unit <NUM> is operated to generate suction on drain line <NUM>, to thereby reduce the pressure in the first chamber <NUM> and draw residual fluid across the membrane <NUM>. In an alternative, both valves <NUM>, <NUM> are opened and the fluid supply unit <NUM> is operated to supply a fluid, e.g. a dialysis fluid, to the supply line <NUM> and to establish a higher flow rate in the drain line <NUM> than in the supply line <NUM>. The filtration of step <NUM> may be at least partly concurrent with the circulation of step <NUM>. It is conceivable that the machine <NUM> is operated to alternate between filtration and circulation. Steps <NUM> and <NUM> are terminated when the second flow circuit C2 is deemed to be sufficiently drained of residual fluid. Steps <NUM> and <NUM> may be terminated by the operator, e.g. by pressing a button on the machine, or automatically by the machine <NUM>, e.g. based on dead-reckoning of the volume pumped into the patient by the pump <NUM> and/or based on input from a sensor, such as a pressure sensor in fluid communication with the closed loop (cf. P1, P2 in <FIG>) and/or a pressure sensor in the fluid supply unit (cf. P3 in <FIG>).

Finally, in step <NUM>, clamps <NUM>, <NUM> are opened and the operator is instructed to strip the machine <NUM> of the set of disposables by disconnecting the dialyzer <NUM>, the line arrangements 24A, 24B and the container <NUM>, preferably as a unit. The operator may then discard the set of disposables. Subsequently, the machine <NUM> may perform a conventional disinfection procedure, e.g. after instructing the operator to connect tubing <NUM>', <NUM>" to ports <NUM>', <NUM>' (<FIG>).

The procedure <NUM> enables the closed loop, including the container <NUM>, to be substantially drained of residual fluid during the draining phase. This reduces the weight of the set of disposables to be discarded and also reduces the risk that residual fluid is spilled on and around the machine <NUM>. As understood from <FIG>, by enabling the second fluid circuit C2 to be connected to two separate ports <NUM>, <NUM> on the container <NUM>, the procedure <NUM> may be implemented by use of a simple and conventional line set and by use of a conventional dialysis machine <NUM>. Further, it is currently believed that the circulation of residual fluid through the container <NUM> serves to facilitate draining of the closed loop. For example, the inflow of residual fluid through the inlet port <NUM> may serve to reduce the risk of the outlet port <NUM> becoming obstructed before the container <NUM> is completely drained. Such obstruction may occur, e.g., if the container is compliant (flexible) and gradually collapses as the amount of residual fluid in the container <NUM> diminishes.

By experimentation, the inventors have found that the draining of the closed loop may be facilitated if the closed loop is vented to the atmosphere during the filtration and/or between periods of filtration (step <NUM>). Such venting will counteract formation of negative (sub-atmospheric) pressure in the closed loop by the filtration, and thereby ensure a sufficient pressure difference between the chambers <NUM>, <NUM> as well as counteract flow resistance caused by negative pressure, e.g. a collapsing of the container <NUM> (if flexible). For automated draining, the venting is preferably machine-controlled.

An embodiment that enables such machine-controlled venting by use of a simple and conventional line set will now be described with reference to a flow chart in <FIG> in combination with system diagrams in <FIG>, which illustrate a dialysis machine <NUM> when arranged and operated for blood treatment and drainage of residual fluid, respectively. In the illustrated example, the line arrangement 24A includes a branch line <NUM> in fluid communication with the drip chamber <NUM> and extending to a connector for connection to sensor port <NUM>, which is in fluid communication with a first pressure sensor P1 in the machine <NUM>. The line arrangement 24B includes a branch line <NUM> in fluid communication with the withdrawal line <NUM>" and extending to a connector for connection to sensor port <NUM>, which is in fluid communication with a second pressure sensor P2 in the machine <NUM>. As is well-known to the skilled person and shown in <FIG>, the branch lines <NUM>, <NUM> are connected to the ports <NUM>, <NUM> during blood treatment, thereby enabling the machine <NUM> to monitor pressure (aka "arterial pressure") on the withdrawal side of the second flow circuit C2 upstream of the pump <NUM>, and pressure (aka "venous pressure") on the return side of the second flow circuit C2.

The procedure <NUM> is performed when the blood treatment in <FIG> has been terminated and includes an initial rinseback step <NUM>, which may be identical to step <NUM>, and a re-arrangement step <NUM>, which may be identical to step <NUM> and results in connectors <NUM>, <NUM> being connected to ports <NUM>, <NUM> of container <NUM>, as seen in <FIG>. After step <NUM>, the operator is instructed to remove the withdrawal line <NUM>" from the clamp <NUM>, which is opened (step <NUM>), disconnect branch line <NUM> from sensor port <NUM> so that the terminal end of branch line <NUM> is open to the environment (step <NUM>), and install branch line <NUM> in clamp <NUM> so that clamp <NUM> is operable to selectively open and close branch line <NUM> (step <NUM>). The procedure <NUM> then proceeds to the draining phase, by performing a circulation step <NUM> and a filtration step <NUM> in correspondence with steps <NUM> and <NUM> as described above, as well as a ventilation step <NUM>, in which clamp <NUM> is opened to vent the closed loop, for reasons explained above.

The ventilation in step <NUM> may differ depending on implementation. In one embodiment, steps <NUM> and <NUM> are performed with open clamps <NUM>, <NUM> to ensure proper filtration and circulation, as illustrated in <FIG>, in which a dashed arrow designates air that enters the opened branch line <NUM>. However, the inventors have found that the draining of the closed loop may be facilitated, particularly at end of the draining phase when small amounts of residual fluid remain in the container <NUM>, if clamp <NUM> is intermittently closed during circulation and/or filtration. In one example, the clamp <NUM> is closed during a fraction of the duration of the draining phase, e.g. less than <NUM>%, <NUM>%, <NUM>% or <NUM>%. Thus, the branch line is kept open during the draining phase except for one or more short time periods in which the branch line is closed. In fact, the inventors have found that draining may be improved by toggling the clamp <NUM>, particularly towards the end of the draining phase. In such toggling, the clamp <NUM> is repeatedly (<NUM> or more times) switched to close and then re-open the branch line <NUM>. In one embodiment, the clamp <NUM> is intermittently closed for <NUM>-<NUM> seconds, and preferably <NUM>-<NUM> seconds, during the toggling. In step <NUM>, when the second flow circuit C2 is deemed, by operator input or based on sensor data, to be sufficiently drained of residual fluid the clamps <NUM>, <NUM> are closed. After a predefined wait time ΔT (step <NUM>), the pump <NUM> is stopped and filtration is terminated (step <NUM>). Optionally, the filtration may be stopped already at step <NUM> or step <NUM>. By operating the pump <NUM> during the wait time ΔT, a negative pressure is established in branch line <NUM>. This will reduce risk of residual fluid leaking out of the branch line <NUM> when the clamps <NUM>, <NUM> are subsequently opened for disconnection of the disposables (cf. step <NUM>). In an alternative, only clamp <NUM> is closed in step <NUM>, and clamp <NUM> is subsequently closed in step <NUM>. This may further reduce the risk of liquid leaking from the branch line <NUM> when disconnected after completed draining phase.

The procedure <NUM> may be implemented by use of a simple and conventional line set and by use of a conventional dialysis machine <NUM> and enables facilitated draining of the second flow circuit C2 by machine-controlled venting of the closed loop.

It is to be realized that corresponding effects may be achieved if steps <NUM>, <NUM> are modified to instruct the operator to replace the return line <NUM>' by the branch line <NUM> in clamp <NUM>, resulting in the configuration shown in <FIG>. All other steps of the procedure <NUM> may be implemented as described with reference to <FIG>. However, to facilitate draining in step <NUM>, clamp <NUM> is operated for ventilation/toggling. Further, only clamp <NUM> may be closed in step <NUM>, whereas clamp <NUM> may be subsequently closed in step <NUM>. The installation of the branch line <NUM> in clamp <NUM> enables a dedicated leakage prevention procedure to be performed between steps <NUM> and <NUM>. In this procedure, the control system <NUM> closes clamp <NUM> and then operates pump <NUM> to generate negative pressure in the withdrawal line <NUM>" downstream of the clamp <NUM> and in the branch line <NUM>. The control system <NUM> may stop the blood pump <NUM> after a predefined time or when a predefined pressure is attained in the branch line <NUM>, e.g. indicated by the pressure sensor P2. The negative pressure reduces the risk of blood leakage when the branch line <NUM> is disconnected from the sensor port <NUM> in step <NUM>.

The installation of the branch line <NUM> in clamp <NUM> as shown in <FIG>, or in clamp <NUM> as shown in <FIG>, has the advantage of enabling the blood pump <NUM> to generate a negative pressure in the branch line <NUM> by steps <NUM>-<NUM>.

In further alternatives, not shown, steps <NUM>-<NUM> are modified to instruct the operator to disconnect branch line <NUM> from sensor port <NUM> and install branch line <NUM> in either of clamps <NUM>, <NUM>.

The implementation of the procedure <NUM> may depend on the particular combination of dialysis machine and line set, e.g. which branch line <NUM>, <NUM> is long enough to be arranged in which clamp <NUM>, <NUM>.

In all embodiments herein, the above-mentioned negative pressure may be generated by operation of the blood pump <NUM> and/or by performing filtration through the dialyzer membrane.

There may be situations when it is not possible or desirable to use a two-port container <NUM> as described hereinabove. Instead, a single-port container may be preferred. For example, a dialysis clinic may want to keep an existing supply chain of single-port containers, may want to avoid stock-keeping of different container types, etc. When using a single-port container, it is equally important to avoid the need for a specialized line set to perform machine-controlled draining of the blood circuit after completed blood treatment.

This objective may be achieved in accordance with a second inventive concept by use of a three-way manifold coupling unit, which defines three ports and an internal manifold that fluidly connects the ports. Such a coupling unit may also be denoted "T coupling" or "Y coupling" in the art. One port of the coupling unit is connected to the port of the single-port container to provide two ports for connection to the return and withdrawal lines of a line set. By such an arrangement, a closed loop may be formed by use of a conventional line set, where the container is fluidly connected to the closed loop by the coupling unit, but is located outside of the closed loop. Experiments show that the closed loop and the container may be substantially drained of residual fluid by performing the above-described filtration to draw the residual fluid into the dialysis machine through the dialyzer membrane.

In the following, an embodiment of the second inventive concept will be described with reference to the flow chart in <FIG> in combination with the system diagram in <FIG>, which includes a container <NUM> with a single port <NUM>' and otherwise corresponds to <FIG>. The flow chart in <FIG> corresponds to <FIG> and represents a post-treatment procedure <NUM>' that includes rinseback, a draining phase and removal of disposables. Unless otherwise stated, the description of <FIG> is equally applicable to <FIG>. The procedure <NUM>' differs from the procedure <NUM> by the re-arrangement step <NUM>', in which the operator is instructed to connect a first port of a <NUM>-way manifold coupling unit <NUM> to the container port <NUM>' and to connect the terminal connectors <NUM>, <NUM> to second and third ports of the coupling unit <NUM>. It is realized from <FIG> that the provision of the coupling unit <NUM> enables the use of a conventional line set and that steps <NUM>, <NUM>-<NUM> may be performed as described for <FIG>. As indicated by an arrow in <FIG>, fluid is drawn from the container <NUM> into the closed loop by the filtration (step <NUM>). In a variant, the coupling unit <NUM> is connected to the container port <NUM>' already in step <NUM>, i.e. in preparation for the rinseback procedure. For example, step <NUM> may involve connecting the first port of the coupling unit <NUM> to the container port <NUM>' and connecting the connector <NUM> on the withdrawal line <NUM>" to the second port of the coupling unit <NUM>, while ensuring that the third port of the coupling unit <NUM> is closed. The dialysis machine then performs rinseback. Then, in step <NUM>, the operator may be instructed to form the closed loop by connecting the connector <NUM> on the return line <NUM>' to the third port of the coupling <NUM>.

The description of the procedure <NUM> in <FIG> is also applicable to the second inventive concept, given that step <NUM> is modified in correspondence with step <NUM>'. As noted, the coupling unit <NUM> may optionally be connected to the container port <NUM>' already in step <NUM>. All embodiments described with reference to <FIG> are equally applicable to the second inventive concept.

Experiments conducted by the inventors indicate that the venting step <NUM>, and in particular the toggling of the branch line during the venting step <NUM>, results in a significant reduction in the time required for draining the second flow circuit C2 in accordance with the second inventive concept. The toggling will provide a motive force that actively pulls fluid from the container into the closed loop and thereby reduces the time required for draining the container <NUM>.

As a non-limiting example, the first and second inventive concepts may be implemented to substantially drain the second fluid circuit C2 and the container <NUM> of residual fluid in <NUM>-<NUM> minutes, assuming that the total volume of residual fluid to be drained is less than approx. <NUM>-<NUM> and that the dialyzer <NUM> has a high-flux or high-permeability membrane (having an ultrafiltration capacity of more than <NUM>/h/mmHg). As used herein, "substantially drain" may indicate that the total remaining amount of residual fluid after the draining phase is no more than <NUM>, and preferably no more than <NUM>.

By insightful reasoning, the inventors have found that it might be advantageous to avoid exposing sensitive components in the fluid supply unit <NUM> to the residual fluid, which may include blood residues. For example, exposing sensors to the residual fluid might lead to fouling that causes the machine <NUM> to malfunction. Thus, in one embodiment, a drain flow path within the fluid supply unit <NUM> is modified during filtration compared to blood treatment to avoid such exposure. Furthermore, the flow paths within the fluid supply unit <NUM> may be modified such that the output signal of a pressure sensor in the fluid supply unit <NUM> represents pressure in the first chamber <NUM> of the dialyzer <NUM>, allowing the control system <NUM> to at least partly control the filtration based on the output signal.

These principles will now be exemplified with reference to a conventional fluid supply unit <NUM> which is depicted in <FIG>. The fluid supply unit <NUM> defines a supply flow path <NUM> that extends from a dialysis fluid supply <NUM> to the outlet port <NUM> and includes a supply valve <NUM>, a supply pump <NUM>, a degassing device <NUM>, a conductivity sensor <NUM>, a pressure sensor P3, a flow sensor <NUM>, and an outlet valve <NUM>. The fluid supply system <NUM> also defines a drain flow path <NUM> that extends from the inlet port <NUM> to a drain <NUM> and includes a degassing device <NUM>, an inlet valve <NUM>, a flow sensor <NUM>, a conductivity sensor <NUM>, a blood detector <NUM>, and a drain pump <NUM>. A gas evacuation line <NUM> connects the degassing chamber <NUM> to the drain flow path <NUM> upstream of the drain pump <NUM> and includes an evacuation valve <NUM>. In the illustrated example, fluid communication may be established between the first and second flow paths <NUM>, <NUM>, via either of a first and a second bypass line <NUM>, <NUM> with a respective bypass valve <NUM>, <NUM>. The first bypass line <NUM> extends between an upstream end of flow sensor <NUM> and a downstream end of flow sensor <NUM>, and the second bypass line <NUM> extends between a downstream end of flow sensor <NUM> and an upstream end of flow sensor <NUM>. Although not shown in <FIG>, further sensors may be included in the inlet and outlet flow paths <NUM>, <NUM>, e.g. sensors included in a protective system of the machine <NUM>.

The fluid supply unit <NUM> may be operated during blood treatment, by the control system <NUM> (<FIG>), to generate a flow of fresh dialysis fluid through the outlet port <NUM> and a flow of spent dialysis fluid through the inlet port <NUM>, as indicated by solid arrows in <FIG>. In the illustrated example, valves <NUM>, <NUM> are open, supply <NUM> pump is active, bypass valves <NUM>, <NUM> are closed, valve <NUM> is open and drain pump <NUM> is active. Further, evacuation valve <NUM> is opened, at least intermittently, to allow gases to be drawn from degassing device <NUM> along gas evacuation line <NUM> by drain pump <NUM>, as indicated by a dashed arrow.

<FIG> illustrates a method <NUM> of operating the fluid supply unit <NUM> for achieving the above-mentioned filtration during the draining phase. The control system <NUM> may execute the method <NUM> by generating suitable control signals for the valves and the pumps in the fluid supply unit <NUM>. The resulting configuration of the fluid supply unit <NUM> is shown in <FIG>. In step <NUM>, supply pump <NUM> is stopped and outlet valve <NUM> is closed. In the example of <FIG>, supply valve <NUM> may also be closed. In step <NUM>, inlet valve <NUM> is closed. In step <NUM>, evacuation valve <NUM> is opened to establish a flow path between drain port <NUM> and drain pump <NUM>. In step <NUM>, bypass valve <NUM> is opened to establish fluid communication between drain flow path <NUM> and the pressure sensor P3 in the supply flow path <NUM>. In step <NUM>, drain pump <NUM> is started to thereby draw residual fluid from dialyzer <NUM> into inlet port <NUM>, via degassing device <NUM>, evacuation line <NUM>, and drain pump <NUM> into drain <NUM>, as indicated by solid arrows in <FIG>. Thus, this unconventional use of the gas evacuation line <NUM> makes it possible to avoid exposing the sensors <NUM>-<NUM> in the drain flow path <NUM> to residual fluid. Further, by opening the bypass valve <NUM>, the pressure sensor P3 will be responsive to pressure changes in the second chamber <NUM> of the dialyzer <NUM>. Thus, in step <NUM>, the drain pump <NUM> and thus the filtration may be controlled based on the output signal of the pressure sensor P3.

The method <NUM> may be implemented in any fluid supply unit <NUM> that defines a supply flow path (cf. <NUM>) and a drain flow path (cf. <NUM>) comprising a set of sensors (cf. <NUM>-<NUM>), wherein step <NUM> generally involves opening a valve (cf. <NUM>) located in a connecting line (cf. <NUM>), which extends between a first location in the drain flow path intermediate an inlet port (cf. <NUM>) and an inlet valve (cf. <NUM>) and a second location in the drain flow path intermediate a drain pump (cf. <NUM>) and the set of sensors. Further, step <NUM> may generally involve opening a bypass valve (cf. <NUM>, <NUM>) in a bypass line (cf. <NUM>, <NUM>), which extends between a third location in the drain flow path intermediate the inlet valve (cf. <NUM>) and the second location, and a fourth location in the supply flow path intermediate a supply pump (cf. <NUM>) and an outlet valve (cf. <NUM>), so as to establish fluid communication between the inlet port (cf. <NUM>) and a pressure sensor (cf. P3) in the supply flow path.

While the invention 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 invention is not to be limited to the disclosed embodiments, but on the contrary, is defined by the appended claims.

For example, the foregoing description is equally applicable to any machine or apparatus which is configured to perform extracorporeal blood treatment by use of a dialyzer or an equivalent filtration unit, including but not limited to hemodialysis, hemofiltration, hemodiafiltration, plasmapheresis, extracorporeal blood oxygenation, extracorporeal liver support/dialysis, ultrafiltration, etc..

Further, it is conceivable to arrange another existing branch line of the line set in one of the machine-controlled clamps. For example, conventional line sets may include a branch line for infusion of anticoagulant and/or a branch line for infusion of substitution fluid.

In a further variant, the branch line may be installed in any other machine-controlled clamp than the withdrawal and return clamps that may be present on the dialysis machine. For example, dialysis machines may comprise a venting clamp for engagement with a branch line ("venting line") connected to the drip chamber <NUM>. It is also conceivable to omit steps <NUM>-<NUM> and perform step <NUM> by controlling the venting clamp in engagement with the venting line.

In a further variant, steps <NUM> and <NUM> are omitted, which means that the branch line is disconnected to be open to the atmosphere during steps <NUM>-<NUM>.

Further, the above-mentioned toggling during step <NUM> may be achieved by instructing the operator to intermittently and manually pinch the branch line, e.g. by use of a manual clamp.

Claim 1:
A control system for a blood treatment apparatus (<NUM>) that comprises a fluid supply unit (<NUM>) and is configured for installation of a dialyzer (<NUM>) and a line set (24A, 24B) to define a first flow circuit (C1) for conducting a fluid provided by the fluid supply unit (<NUM>) through the dialyzer (<NUM>) and back to the fluid supply unit (<NUM>), and to define a second flow circuit (C2) which is separated from the first flow circuit (C1) by a semi-permeable membrane (<NUM>) of the dialyzer (<NUM>) and comprises return and withdrawal lines (<NUM>', <NUM>") for connection to a vascular system of a subject (S) during a blood treatment session, said control system being configured to, subsequent to a termination of the blood treatment session:
instruct an operator to connect the second flow circuit (C2) to a first port (<NUM>) of a container (<NUM>) that holds a human-compatible fluid;
operate the blood treatment apparatus (<NUM>) to push remaining blood in the second flow circuit (C2) into the vascular system of the subject (S) through the return line (<NUM>') while admitting the human-compatible fluid from the container (<NUM>) into the second flow circuit (C2);
instruct the operator to disconnect the return line (<NUM>') from the vascular system of the subject (S) and re-arrange the second flow circuit (C2) to define a closed loop; and
operate, in a draining phase, the blood treatment apparatus (<NUM>) to draw residual liquid from the closed loop into the first flow circuit (C1) through the semi-permeable membrane (<NUM>) of the dialyzer (<NUM>);
wherein the operator is instructed to re-arrange the second flow circuit (C2) by connecting the second flow circuit (C2) to a second port (<NUM>) of the container (<NUM>) so that the container (<NUM>) is included in the closed loop.