Patent Description:
One type of kidney failure therapy is peritoneal dialysis (PD), which infuses a dialysis solution, also called dialysis fluid, into a patient's peritoneal chamber via a catheter. The dialysis fluid is in contact with the peritoneal membrane in the patient's peritoneal chamber. Waste, toxins and excess water pass from the patient's bloodstream, through the capillaries in the peritoneal membrane, and into the dialysis fluid due to diffusion and osmosis, i.e., an osmotic gradient occurs across the membrane. An osmotic agent in the PD dialysis fluid provides the osmotic gradient. Used or spent dialysis fluid is drained from the patient, removing waste, toxins and excess water from the patient. This cycle is repeated, e.g., multiple times.

Extracorporeal blood treatment involves removing blood from a patient, treating the blood externally to the patient, and returning the treated blood to the patient. Extracorporeal blood treatment is typically used to extract undesirable matter or molecules from the patient's blood and add desirable matter or molecules to the blood. Extracorporeal blood treatment is used with patients unable to effectively remove matter from their blood, such as when a patient has suffered temporary or permanent kidney failure. These patients and other patients may undergo extracorporeal blood treatment to add or remove matter to their blood, to maintain an acid/base balance or to remove excess body fluids, or to perform extracorporeal gas exchange processes, for example.

Systems of this kind, like a peritoneal dialysis apparatus or an extracorporeal blood treatment apparatus, are configured to manage fluids, like medical fluids and/or blood, and comprise valves to control the fluid or fluids flow.

Systems comprising a rigid cartridge and a soft elastic membrane are known. The rigid cartridge comprises volcano-like funnels facing the soft elastic membrane. The volcano-like funnels put into communication a chamber or passage with another chamber or passage of the cartridge. The volcano-like funnels are closed by respective pistons configured to keep pressed the soft elastic membrane against the volcano-like funnels. The volcano-like funnels are opened by moving away the pistons from the volcano-like funnels and also from the soft elastic membrane.

A main drawback of this kind of valves is that, when the piston is moved away from the soft elastic membrane to open the valve, in case of a negative pressure in the funnel, the soft elastic membrane may remain stuck on an edge of the funnel and the valve closed. The negative pressure generates a self-closing effect even if the piston is in a backward position.

Document <CIT> discloses a device for transferring a fluid in an injection apparatus or in a dialysis apparatus. The device has a main channel, a secondary channel leading at an opening into the main channel, and a flexible closing element for closing the secondary channel. The opening of the secondary channel can be closed in a fluid-tight manner by the flexible closing element, by pressing the closing element with an external force, exerted by a valve actuator, onto or into the opening. In order to prevent that, in the case of a negative pressure in the main channel, the flexible closing element closes the secondary channel even without application of an external force, at least one projection is associated with the or each secondary channel and arranged in the main channel in the area of the opening of the respective secondary channel, and protrudes over the opening or over a lowest level of the opening.

A main disadvantage of <CIT> is that the correct opening of the valve in case of negative pressure depends also on the pliability of the membrane. Part of the membrane may remain stuck on the edge of the secondary channel if the membrane is very soft, yieldable and pliable.

Document <CIT> discloses a disposable cassette, for example for an extracorporeal treatment of blood, having a sealing membrane and a valve actuator therefor. The disposable cassette comprises a fluid guide body and the sealing membrane lying thereon. A passage of the fluid guide body extends in a main passage in the form of a volcano-like funnel. The sealing membrane is pressed against an orifice of the volcano-like funnel or raised away from the volcano-like funnel by an actuating part of the valve actuator connected to a plunger surface and to the sealing membrane.

A main disadvantage of <CIT> is that the actuating part must be connected to the sealing membrane to push and also pull said membrane and therefore said actuating part must be part of the cassette. This implies high costs for making the disposable cassette or for providing releasable couplings between the sealing membrane and the plunger.

Document <CIT> discloses a centrifugal fluid processing system and a fluid processing cassette with a cassette body and a soft membrane delimiting liquid passages: a first port of a valve station is in fluid communication with one liquid passage and an occlusion element (plunger) moves the soft membrane between a retracted position allowing liquid passage and a forward position wherein the membrane occludes the liquid passage. Part of the membrane may remain stuck on the edge of the liquid passage if the membrane is very soft, yieldable and pliable.

Document <CIT> discloses a spring element to unseat a valve membrane of an assembly; the spring assembly is provided at the manifold of the medical device.

It is therefore an object of the present invention to improve accuracy and reliability of the volcano-like valves.

It is an object of the present invention to provide volcano-like valves which may be opened and keep open in reliable manner also in case of negative pressure.

It is a further object of the present invention to provide volcano-like valves provided with the above cited features without increasing the manufacturing costs of the manifold which said valves belong to.

It is a further object of the present invention to provide a manifold assembly comprising said volcano-like valves which is cost effective and reliable, wherein said manifold assembly may be also disposable.

At least one of the above objects is substantially reached by a medical apparatus according to one or more of the appended claims.

A medical apparatus according to aspects of the present disclosure and capable of achieving one or more of the above objects is here below disclosed.

Referring now to the <FIG>, an embodiment of a peritoneal dialysis apparatus <NUM> (APD) comprises a cycler <NUM> and a manifold assembly <NUM> (<FIG> and <FIG>) that organizes tubing and performs many functions discussed herein.

The cycler <NUM> comprises a box <NUM> housing all the mechanical and electronical parts of the cycler <NUM>. The cycler <NUM> comprises an electronic control unit <NUM> (<FIG>), a roller peristaltic pump <NUM> (<FIG>), a plurality of occlusion elements <NUM>, a first or high level sensor <NUM> and a second or low level sensor <NUM>, a pressure transducer <NUM> and an air pump <NUM> (schematically illustrated in <FIG>). The cycler <NUM> may also comprise a heater, not shown.

The peristaltic pump shown in <FIG> and <FIG> comprises two pressing rollers 6a angularly spaced of <NUM>°.

A motor, not shown, of the peristaltic pump <NUM> is housed in the box <NUM> and a rotor <NUM> of the peristaltic pump <NUM> is positioned on a front panel <NUM> of the box <NUM> (<FIG>).

A site <NUM> of the front panel <NUM> next to the rotor <NUM> is configured to retain in removable manner the manifold assembly <NUM> on said front panel <NUM>. The site <NUM> may comprise retaining elements configured to be coupled to the manifold assembly <NUM> and/or the manifold assembly <NUM> comprises hooking elements configured to hook, in removable manner, said disposable assembly <NUM> to the front panel <NUM> of the cycler <NUM>.

The occlusion elements <NUM> (<FIG>) protrude from the front panel at the site <NUM>. Each occlusion element <NUM> comprises a plunger <NUM> (<FIG>) moved by a respective actuator, not shown, housed in the box <NUM>. The actuator is configured to move the plunger <NUM> between a retracted position (<FIG>) and a forward position (<FIG>), as will be discussed herein.

The cycler <NUM> comprises a lid <NUM> (<FIG> and <FIG>) movable between a closed position, in which the lid <NUM> covers the front panel <NUM>, and an open position, in which the lid <NUM> is spaced from the front panel <NUM> to allow a user to access to said front panel <NUM>. The lid <NUM> of the embodiment of the attached Figures is hinged to the box <NUM> and may be rotated between the open and the closed position. For sake of simplicity, elements detailed below and belonging to the lid <NUM> have not been depicted in <FIG>.

When the manifold assembly <NUM> is properly mounted on the site <NUM> of the cycler <NUM> and the lid <NUM> is in the closed position, said manifold assembly <NUM> is closed between the front panel <NUM> and the lid <NUM>.

The first level sensor <NUM> and the second level sensor <NUM> are installed on the lid <NUM> and protrude from a side of the lid <NUM> configured to face the front panel <NUM> and/or the manifold assembly <NUM> when the lid <NUM> is in the closed position (<FIG>). The illustrated level sensors <NUM>, <NUM> are capacitive sensors. In other embodiments, not shown in the attached Figures, the level sensors <NUM>, <NUM> may be ultrasonic sensors or other type of sensors and/or may be installed on the front panel of the box <NUM>.

An air conduit <NUM> is mounted on the lid <NUM> and comprises a coupling end <NUM>. The coupling end <NUM> is configured to face the manifold assembly <NUM> when the lid <NUM> is in the closed position (<FIG> and <FIG>), as will be discussed herein. The air conduit <NUM> is in air communication with the pressure transducer <NUM> and the air pump <NUM>. The pressure transducer <NUM> and the air pump <NUM> may be installed in the lid <NUM> or in the box <NUM>.

The control unit <NUM>, schematically shown in <FIG>, is operationally connected to the motor of the peristaltic pump <NUM>, to the actuators of the occlusion elements <NUM>, to the pressure transducer <NUM> and the air pump <NUM>, to the first level sensor <NUM> and second level sensor <NUM>, to the heater and to any other device or sensor of the cycler <NUM> and is configured/programmed to control operation of the peritoneal dialysis apparatus <NUM>.

The control unit may be also connected to a display, a keyboard or a touch screen <NUM> configured to show working parameters of the apparatus <NUM> and/or to allow a user to set up the apparatus <NUM> (<FIG>).

The lid <NUM> and/or the front panel <NUM> of the box <NUM> may also comprise further elements, not shown, configured to manage and route tubing of the manifold assembly <NUM>.

The manifold assembly <NUM> for the peritoneal dialysis apparatus <NUM> comprises a disposable casing <NUM> comprising a rigid molded plastic rigid shell <NUM>, e.g. made of PETG (polyethylene terephthalate glycol-modified) polymer (<FIG>, <FIG> and <FIG>), and a plastic sheet <NUM>, e.g. a polyvinyl chloride soft sheet (<FIG>). The rigid molded plastic rigid shell <NUM> delimits a front and sides of the casing <NUM> and the plastic sheet <NUM> is a back of the casing <NUM> (<FIG>).

The plastic rigid shell <NUM> has a substantially flattened shape and comprises septa and recesses on the inner side of the casing <NUM>. Said septa delimit internally a first compartment <NUM> and a second compartment <NUM> for fresh and spent dialysis fluid (<FIG>). Said recesses delimit internally respective three expansion chambers 24a, 24b, 24c and externally, on the front of the casing <NUM>, respective three protrusions 25a, 25b, 25c (<FIG> and <FIG>).

In a front view or back view, the plastic rigid shell <NUM> and the casing <NUM> have a substantially rectangular outline with two long sides and two short sides. When the casing <NUM> is properly mounted on the cycler <NUM>, the two long sides are vertical.

The first compartment <NUM> is delimited by an outer septum <NUM> positioned on a peripheral border of the plastic rigid shell <NUM> and by a first inner septum <NUM>. Referring to the back view of <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, the first inner septum <NUM> has a first extremity connected to the outer septum <NUM> on the top short side of the plastic rigid shell <NUM> and a second extremity connected to the outer septum <NUM> on the right long side of the of the plastic rigid shell <NUM>.

The first inner septum <NUM> has a substantially U-shape and develops substantially parallel to the left long side, to the bottom short side and to the right long side of the plastic rigid shell <NUM>. The first compartment <NUM> is a U-shaped first elongated passage.

The second compartment <NUM> is delimited by the first inner septum <NUM> and by a portion of the outer septum <NUM> not delimiting the first compartment <NUM>, such that the second compartment <NUM> is partly surrounded by the U-shaped first compartment <NUM>.

A second inner septum <NUM> is positioned inside the second compartment <NUM> to create a route in the second compartment <NUM>. The second inner septum <NUM> has a first extremity connected to the first inner septum <NUM> at a location close to the first extremity of said first inner septum <NUM> and a second free extremity positioned close to a lower right corner of the plastic rigid shell <NUM>.

Referring to the back view of <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, the second inner septum <NUM> has a substantially inverted U-shape and develops substantially parallel to the top short side and to the right long side of the plastic rigid shell <NUM>. Therefore, the second compartment <NUM> comprises an inverted U-shaped second elongated passage.

A long stretch of the inverted U-shaped second elongated passage is parallel to a right long stretch of the U-shaped first elongated passage. The second compartment <NUM> comprises a main central part divided, in part, from the second elongated passage by the second inner septum <NUM>. The second elongated passage has a second extremity communicating with the main central part.

The three expansion chambers 24a, 24b, 24c are fashioned in the main central part of the second compartment <NUM> and each expansion chamber 24a, 24b, 24c has a depth greater than a depth of a remaining part of the second compartment <NUM>.

Two through apertures 29a, 29b (<FIG> and <FIG>) pass through the plastic rigid shell <NUM> and the main central portion of the second compartment <NUM>. These two through apertures are surrounded and delimited by respective further septa <NUM> connected to the first inner septum <NUM> Therefore, also these further septa <NUM> delimit the second compartment <NUM>.

A first aperture 29a and a second aperture 29b are positioned between two of said three of expansion chambers 24a, 24b, 24c. A first expansion chamber 24a of the three expansion chambers 24a, 24b, 24c is close to the bottom short side of the casing <NUM> and to a short stretch of the U-shaped first elongated passage; a second expansion chamber 24b of the three expansion chambers 24a, 24b, 24c is placed between the first aperture 29a and the second aperture 29b; a third expansion chamber 24c of the three expansion chambers 24a, 24b, 24c is placed above the second aperture 29b.

An inner volume delimited in the second compartment <NUM> is greater than an inner volume delimited in the first compartment <NUM>. For instance, the inner volume of the second compartment <NUM> is about <NUM><NUM> and the inner volume of the first compartment <NUM> is about <NUM><NUM>.

A hole <NUM> (<FIG>) is fashioned in the front of the plastic rigid shell <NUM> located between the third expansion chamber 24c and the second inner septum <NUM>. A rigid plastic frame <NUM> supporting a breathable membrane <NUM> (<FIG>) is joined, by welding or gluing, to an edge of the hole <NUM>. The breathable membrane <NUM> may be of PTFE (polytetrafluoroethylene).

When the assembly <NUM> is properly mounted on the cycler <NUM>, an upper part of the second compartment <NUM> provided with the breathable membrane <NUM> delimits an air buffer volume, as will be discussed herein.

The plastic sheet <NUM> (<FIG>) is welded or glued to the plastic rigid shell <NUM> The plastic sheet <NUM> is joined to the outer septum <NUM>, the first inner septum <NUM>, the second inner septum <NUM> and to the further septa <NUM>, to seal the first compartment <NUM> and the second compartment <NUM>.

The plastic rigid shell <NUM> comprises a first pump port <NUM> comprising a hollow cylinder protruding from a right side (in <FIG> and <FIG>) of the casing <NUM>. The first pump port <NUM> is in fluid communication with the first compartment <NUM>. The first pump port <NUM> opens inside the first compartment <NUM> at an extremity of the right long stretch of the U-shaped first elongated passage.

The plastic rigid shell <NUM> comprises a second pump port <NUM> comprising a hollow cylinder protruding from the right side (in <FIG> and <FIG>) of the casing <NUM>. The second pump port <NUM> is in fluid communication with the second compartment <NUM>. The second pump port <NUM> opens inside the second compartment <NUM> at a first extremity of the second elongated passage.

The first pump port <NUM> and the second pump port <NUM> are close to each other but separated by the first inner septum <NUM>. The hollow cylinders defining the first pump port <NUM> and the second pump port <NUM> diverge from each other away from the casing <NUM>.

The plastic rigid shell <NUM> comprises a drain port <NUM> comprising a hollow cylinder <NUM> protruding from the left side (in <FIG> and <FIG>) of the casing <NUM>.

The hollow cylinder <NUM> of the drain port <NUM> passes through the outer septum <NUM> such that said drain port <NUM> is in fluid communication with the first compartment <NUM>.

The drain port <NUM> comprises a short hollow barrel <NUM> connected to the hollow cylinder <NUM>. A central axis of the hollow cylinder <NUM> is perpendicular to a main axis of the hollow barrel <NUM> and the cavities delimited inside the hollow cylinder <NUM> and the hollow barrel <NUM> are in fluid communication with each other. The hollow barrel <NUM> protrudes from a bottom surface of the first compartment <NUM> and opens inside the first compartment <NUM> (<FIG>).

The hollow barrel <NUM> is shorter than the adjacent outer septum <NUM> (as shown in <FIG>), than the first inner septum <NUM>, than the second inner septum <NUM>, than the further septa <NUM>, such that the plastic sheet <NUM> is spaced from an edge of the hollow barrel <NUM>, when said plastic sheet <NUM> is not deformed, as shown in <FIG>.

As will be discussed herein, the edge of the hollow barrel <NUM> and a part of the plastic sheet <NUM> facing said edge form a drain valve <NUM> of the drain port <NUM>.

The plastic rigid shell <NUM> further comprises a first dialysis port <NUM> and a second dialysis port <NUM>. Each of these ports <NUM>, <NUM> protrudes from the left side (in <FIG> and <FIG>) of the casing <NUM> and has the same structure as the drain port <NUM> detailed above (hollow cylinder <NUM> and hollow barrel <NUM>).

The first dialysis port <NUM> and a second dialysis port <NUM> have a receptive first dialysis valve <NUM> and a respective second dialysis valve <NUM>.

The plastic rigid shell <NUM> further comprises a heater port <NUM> which also protrudes from the left side (in <FIG> and <FIG>) of the casing <NUM> and is structurally similar to the drain port <NUM> detailed above (hollow cylinder <NUM> and hollow barrel <NUM>). The heater port <NUM> has a heater valve <NUM>. The heater port <NUM> is placed close to an upper left corner of the plastic rigid shell <NUM>.

Differently from the drain port <NUM>, from the first dialysis port <NUM> and from the second dialysis port <NUM>, the hollow barrel <NUM> of the heater port <NUM> is also in fluid communication with an opening <NUM> fashioned through the front of the casing <NUM> (<FIG>).

The plastic rigid shell <NUM> comprises a further hollow barrel <NUM> placed in the second compartment <NUM> and close to the hollow barrel <NUM> of the heater port <NUM>. The first inner septum <NUM> is located between the further hollow barrel <NUM> and the hollow barrel <NUM>.

The further hollow barrel <NUM> is in fluid communication with a further opening <NUM> fashioned through the front of the casing <NUM> (<FIG>) and the opening <NUM> and the further opening <NUM> are connected by a by-pass channel <NUM> delimited by a cover <NUM> welded or glued to the front of the plastic rigid shell <NUM>. The by-pass channel <NUM> is in fluid communication with the first compartment <NUM>, with the second compartment <NUM> and with the heater line tube <NUM>.

An edge of the further hollow barrel <NUM> and a part of the plastic sheet <NUM> facing said edge form a by-pass valve <NUM>. The further hollow barrel <NUM> is part of a by-pass port <NUM> provided with the by-pass valve <NUM>.

The second inner septum <NUM> separates an area of the second compartment <NUM> with the hole <NUM> and the breathable membrane <NUM> from the by-pass valve <NUM> (<FIG> and <FIG>).

The plastic rigid shell <NUM> further comprises a patient port <NUM>. The patient port <NUM> protrudes from the left side (in <FIG> and <FIG>) of the casing <NUM> and has the same structure as the drain port <NUM> detailed above (hollow cylinder <NUM> and hollow barrel <NUM>).

The hollow cylinder <NUM> of the patient port <NUM> passes through the outer septum <NUM> and the first inner septum <NUM> such that said patient port <NUM> is in fluid communication with the second compartment <NUM> (<FIG>). The patient port <NUM> has a patient valve <NUM>.

All the valves (drain valve <NUM>, first dialysis valve <NUM>, second dialysis valve <NUM>, heater valve <NUM>, by-pass valve <NUM>, patient valve <NUM>) are structurally and functionally identical and, when the manifold assembly <NUM> is properly mounted on the cycler <NUM>, they are each placed in front of a respective occlusion element <NUM> of the cycler <NUM>. Each occlusion element <NUM> of the cycler <NUM> is configured to open or close the respective valve (<FIG>). In other embodiments, not shown in the attached Figures, the occlusion element <NUM> may be installed on the lid <NUM> and the structure of the manifold assembly <NUM> is such to cooperate with said occlusion element <NUM> on the lid <NUM>.

The hollow cylinders <NUM> of the heater port <NUM>, the first dialysis port <NUM>, the second dialysis port <NUM>, the drain port <NUM> and the patient port <NUM> are parallel with respect to each other. In the embodiment of the attached Figures, when the manifold assembly <NUM> is properly mounted on the cycler <NUM>, the heater port <NUM> is above the first dialysis port <NUM> which in turn is above the second dialysis port <NUM> which in turn is above the drain port <NUM> which in turn is above the patient port <NUM>.

The first compartment <NUM> shaped like a U-shaped first elongated passage extends between the heater port <NUM> and the first end of the first pump port <NUM>. The second elongated passage has a first extremity connected to the second pump port <NUM>.

The manifold assembly <NUM> comprises a yielding pump tube <NUM> having a first end <NUM> connected to the first pump port <NUM> and to first compartment <NUM> and a second end <NUM> connected to the second pump port <NUM> and to the second compartment <NUM> (<FIG>). The yielding pump tube <NUM> extends outside the casing <NUM> and is shaped as a loop or as an eyelet having an omega "Ω" shape to be placed in part around the rotor <NUM> of the peristaltic pump <NUM> of the cycler <NUM>.

The manifold assembly <NUM> further comprises (<FIG>): a patient line tube <NUM> having a first end connected to the patient port <NUM> and a second end connectable to a patient's peritoneal cavity; a first dialysis fluid line tube <NUM> having a first end connected to the first dialysis port <NUM> and a second end connected to a first supply bag <NUM>; a second dialysis fluid line tube <NUM> having a first end connected to the second dialysis port <NUM> and a second end connected to a second supply bag <NUM>; a heater line tube <NUM> having a first end connected to the heater port <NUM> and a second end connected to a heater bag <NUM>; a drain fluid line tube <NUM> having a first end connected to the drain port <NUM> and a second end connected to a drain <NUM>.

The patient line tube <NUM> may extend to a patient line connector, which may for example connect to a patient's transfer set leading to an indwelling catheter that extends to the patient's peritoneal cavity.

The first compartment <NUM>, the yielding pump tube <NUM> and the second compartment <NUM> delimit together a fluid path extending between one of the first dialysis fluid line tube <NUM>, second dialysis fluid line tube <NUM>, heater line tube <NUM>, drain fluid line tube <NUM> and the patient line tube <NUM>, to allow fluid flow from one of the fluid line tubes to the patient line tube <NUM> or from the patient line tube <NUM> to one of the fluid line tubes when the peristaltic pump <NUM> of the cycler <NUM> is actuated.

The casing <NUM> of the manifold assembly <NUM> is mounted on the front panel <NUM> of the cycler <NUM>, the yielding pump tube <NUM> is coupled to the rotor <NUM> and the first dialysis fluid line tube <NUM>, second dialysis fluid line tube <NUM>, heater line tube <NUM>, drain fluid line tube <NUM> are properly arranged and connected to the respective first supply bag <NUM>, second supply bag <NUM>, heater bag <NUM> and drain <NUM>. The patient line tube <NUM> is properly arranged and connected to the patient P. The heater bag <NUM> is coupled to the heater of the cycler <NUM>.

The shape of the casing <NUM>, with the three protrusions 25a, 25b, 25c and the two through apertures 29a, 29b, facilitate the user to grab the casing <NUM> and to mount the casing <NUM> on the cycler <NUM>.

The user closes the lid <NUM> so that the first level sensor <NUM> and the second level sensor <NUM> are positioned in front of an external flat surface of the casing <NUM>. The position of the first level sensor <NUM> and the second level sensor <NUM> when the lid <NUM> is closed is shown in <FIG> and <FIG>. In <FIG> the positions of the first level sensor <NUM> and second level sensor <NUM> are schematically represented through dashed line circles.

The first level sensor <NUM> and the second level sensor <NUM> are placed one above the other. The first level sensor <NUM> is positioned between the third expansion chamber 24c and the second expansion chamber 24b. The second level sensor <NUM> is positioned between the second expansion chamber 24b and the first expansion chamber 24a.

When the lid <NUM> is closed, the coupling end <NUM> of the air conduit <NUM> is coupled to the rigid plastic frame <NUM> supporting the breathable membrane <NUM> (<FIG> and <FIG>) such that the coupling end <NUM> faces the breathable membrane <NUM>. This way, the pressure transducer <NUM> and the air pump <NUM> of the cycler <NUM> are put into communication with the breathable membrane <NUM> and with the upper part of the second compartment <NUM>, i.e. with the air buffer volume.

According to a method for controlling the peritoneal dialysis apparatus <NUM>, the control unit <NUM> commands the actuators of the occlusion elements <NUM> to open or close the drain valve <NUM>, first dialysis valve <NUM>, second dialysis valve <NUM>, heater valve <NUM>, by-pass valve <NUM> and patient valve <NUM> according to the steps to be performed.

When the valve <NUM> of the patient port <NUM> is open, the patient line tube <NUM> is in fluid communication with the second compartment <NUM>, when the valve <NUM> of the patient port <NUM> is closed, fluid communication between the patient line tube <NUM> and the second compartment <NUM> is prevented.

When the first dialysis valve <NUM> of the first dialysis fluid port <NUM> is open, the first dialysis fluid line tube <NUM> is in fluid communication with the first compartment <NUM>, when the first dialysis valve <NUM> of the first dialysis fluid port <NUM> is closed, fluid communication between the first dialysis fluid line tube <NUM> and the first compartment <NUM> is prevented.

When the second dialysis valve <NUM> of the second dialysis fluid port <NUM> is open, the second dialysis fluid line tube <NUM> is in fluid communication with the first compartment <NUM>, when the second dialysis valve <NUM> of the second dialysis fluid port <NUM> is closed, fluid communication between the second dialysis fluid line tube <NUM> and the first compartment <NUM> is prevented.

When the heater valve <NUM> of the heater port <NUM> is open, the heater line tube <NUM> is in fluid communication with the first compartment <NUM>, when the heater valve <NUM> of the heater port <NUM> is closed, fluid communication between the heater line tube <NUM> and the first compartment <NUM> is prevented.

When the drain valve <NUM> of the drain port <NUM> is open, the drain fluid line tube <NUM> is in fluid communication with the first compartment <NUM>, when the drain valve <NUM> of the drain port <NUM> is closed, fluid communication between the fluid drain line tube <NUM> and the first compartment <NUM> is prevented.

When the by-pass valve <NUM> of the by-pass port <NUM> is open, the heater line tube <NUM> is in fluid communication with the second compartment <NUM>; when the by-pass valve <NUM> of the by-pass port <NUM> is closed, fluid communication between the heater line tube <NUM> and the second compartment <NUM> is prevented.

As shown in <FIG> and <FIG>, when the actuator keeps the plunger <NUM> of the occlusion element <NUM> in the retracted position of <FIG>, the plastic sheet <NUM> is spaced from the edge of the hollow barrel <NUM> and fluid may flow between the hollow barrel <NUM> and the first compartment <NUM> (valve open).

When the actuator moves the plunger <NUM> of the occlusion element <NUM> in the forward position of <FIG> and keeps the plunger <NUM> in said forward position, the plunger <NUM> is accommodated in part in the hollow barrel <NUM>.

The plunger <NUM> pushes, deforms and keeps a portion of plastic sheet <NUM> against the edge of the hollow barrel <NUM>. The hollow barrel <NUM> is a seat for the plunger <NUM> and for the portion of plastic sheet <NUM> trapped between. A fluid flow between the hollow barrel <NUM> and the first compartment <NUM> is prevented (valve closed). All valves work in this way.

Before patient treatment, the manifold assembly <NUM> is primed. A possible priming sequence is represented in the following table (Table <NUM>).

Another priming procedure may be performed using communication vessels as disclosed in the following Table <NUM>.

After priming, patient treatment may be started.

According to an embodiment of the method for controlling the peritoneal dialysis apparatus <NUM> (<FIG> and <FIG>), the control unit <NUM> commands the peritoneal dialysis apparatus <NUM> to move the dialysis fluid from the first supply bag <NUM> to the patient P.

The control unit <NUM> closes and keeps closed the heater valve <NUM>, the by-pass valve <NUM>, the second dialysis valve <NUM> and the drain valve <NUM>, opens and keeps open the first dialysis valve <NUM> and the patient valve <NUM>. The control unit <NUM> commands the motor to rotate the peristaltic pump <NUM> in a first rotation direction (CounterClockWise in <FIG>) to pump the dialysis fluid from the first compartment <NUM> to the second compartment <NUM>.

An auxiliary in-line heater, not shown, may be placed on the first dialysis fluid line tube <NUM> to heat the dialysis fluid while flowing through said dialysis fluid line tube <NUM> and towards the patient P.

According to another embodiment of the method for controlling the peritoneal dialysis apparatus <NUM> (<FIG>, <FIG>, <FIG>, <FIG>, <FIG>), the control unit <NUM> commands the peritoneal dialysis apparatus <NUM> to move the dialysis fluid from the first supply bag <NUM> towards the heater bag <NUM>. In this embodiment, the auxiliary in-line heater is not used.

The control unit <NUM> opens and keeps open the by-pass valve <NUM> and the first dialysis valve <NUM> while closes and keeps closed the heater valve <NUM>, the second dialysis valve <NUM>, the drain valve <NUM> and the patient valve <NUM>. The control unit <NUM> commands the motor to rotate the peristaltic pump <NUM> in a first rotation direction (CounterClockWise in <FIG>) to pump the dialysis fluid from the first compartment <NUM> to the second compartment <NUM> and then to the heater bag <NUM> through the by-pass channel <NUM>.

Once the dialysis fluid has been heated in the heater bag <NUM> coupled to the heater of the cycler <NUM>, the control unit <NUM> commands the peritoneal dialysis apparatus <NUM> to move the heated dialysis fluid from the heater bag <NUM> towards the patient P.

The control unit <NUM> opens and keeps open the heater valve <NUM> and the patient valve <NUM> and closes and keeps closed the by-pass valve <NUM>, the first dialysis valve <NUM>, the second dialysis valve <NUM> and the drain valve <NUM>. The control unit <NUM> commands the motor to rotate the peristaltic pump <NUM> in a first rotation direction (CounterClockWise in <FIG>) to pump the dialysis fluid from the first compartment <NUM> to the second compartment <NUM>.

At the end of the patient treatment, the spent dialysis fluid is removed from the patient P. The control unit <NUM> commands the peritoneal dialysis apparatus <NUM> to move the spent dialysis fluid from the patient P towards the drain <NUM>.

The control unit <NUM> opens and keeps the drain valve <NUM> and the patient valve <NUM> and closes and keeps closed the heater valve <NUM>, the by-pass valve <NUM>, the first dialysis valve <NUM>, the second dialysis valve <NUM>. The control unit <NUM> commands the motor to rotate the peristaltic pump <NUM> in a second rotation direction (ClockWise in <FIG>) to pump the dialysis fluid from the second compartment <NUM> to the first compartment <NUM>.

This treatment sequence is represented in the following table (Table <NUM>).

<FIG> and <FIG> show another embodiment of the manifold assembly <NUM> of the peritoneal dialysis apparatus <NUM> (APD). The cycler <NUM> of this embodiment is not shown and may have the same structure/architecture disclosed for the first embodiment.

The manifold assembly <NUM> (<FIG> and <FIG>) that organizes tubing and performs many functions discussed herein is different from the manifold assembly <NUM> of embodiment <NUM> in the following features.

As can be seen comparing <FIG> and <FIG> (the same reference numerals are used for the same elements), the first dialysis port <NUM> and the second dialysis port <NUM> open inside the second compartment <NUM> instead of the first compartment <NUM>. The first dialysis valve <NUM> and the second dialysis valve <NUM> are positioned in the second compartment <NUM> and close to the second expansion chamber 24b.

The first dialysis fluid line tube <NUM> has the first end connected to the first supply bag <NUM> and the second end connected to the second compartment <NUM>. The second dialysis fluid line tube <NUM> has the first end connected to the second supply bag <NUM> and the second end connected to the second compartment <NUM>.

In addition, the drain port <NUM> and the drain fluid line tube <NUM> are arranged close to a top of the casing <NUM> and, when the manifold assembly <NUM> is properly mounted on the cycler <NUM>, are located above the heater port <NUM> and the heater line tube <NUM>.

The second inner septum <NUM> has a first extremity connected to the right long side of the plastic rigid shell <NUM>, close to the second pump port <NUM> and, differently from the embodiment of <FIG>, the area of the second compartment <NUM> with the hole <NUM> and the breathable membrane <NUM> is not separated from the by-pass valve <NUM> by said second inner septum <NUM>.

Furthermore, the hole <NUM> and the breathable membrane <NUM> are next to the top short side of the plastic rigid shell <NUM>.

An area <NUM> of the plastic sheet <NUM> is configured to be coupled to displacement sensor <NUM> (shown only schematically) of the cycler <NUM> when the manifold assembly <NUM> is properly mounted on the cycler <NUM>.

<FIG> shows that said area <NUM> faces a zone of the first compartment <NUM> located at a right bottom elbow the substantially U-shaped first elongated passage. The displacement sensor <NUM> is mounted on the front panel <NUM> of the cycler <NUM>.

The flow route from the heater bag <NUM> to the patient P and the flow route from the patient P to drain are the same shown in <FIG> and <FIG> and disclosed in the previous paragraphs.

Because of the different position of the first dialysis valve <NUM> and second dialysis valve <NUM>, the flow route from the first supply bag <NUM> to the heater bag <NUM> is other than the one shown in <FIG>.

Indeed, in this second embodiment (<FIG> and <FIG>), the control unit <NUM> opens and keeps open the heater valve <NUM> and the first dialysis valve <NUM> while closes and keeps closed the by-pass valve <NUM>, the second dialysis valve <NUM>, the drain valve <NUM> and the patient valve <NUM>. The control unit <NUM> commands the motor to rotate the peristaltic pump <NUM> in the second rotation direction (ClockWise in <FIG>) to pump the dialysis fluid from the second compartment <NUM> to the first compartment <NUM>.

The treatment sequence for the manifold assembly <NUM> of the second embodiment is shown in the following table (Table <NUM>).

Before patient treatment, the manifold assembly <NUM> of the second embodiment is primed. A possible priming sequence is represented in the following table (Table <NUM>).

<FIG> shows another embodiment of the manifold assembly <NUM> of the peritoneal dialysis apparatus <NUM> (APD). The cycler <NUM> of this embodiment is different from the first embodiment, because the valves are not part of the casing <NUM> and the occlusion elements of the cycler <NUM> are pinch valves.

In this third embodiment, like in the second embodiment, as can be seen comparing <FIG>, <FIG> and <FIG> (the same reference numerals are used for the same elements), the first dialysis port <NUM> and the second dialysis port <NUM> open inside the second compartment <NUM> instead of the first compartment <NUM>.

All the ports do not comprise valves or part of valves. The drain port <NUM> and the drain fluid line tube <NUM> are arranged close to a top of the casing <NUM>, like in the second embodiment.

The second inner septum <NUM> separates the area of the second compartment <NUM> with the hole <NUM> and the breathable membrane from an area of the second compartment <NUM> with an auxiliary drain port <NUM> connected to an auxiliary drain fluid line tube <NUM>.

The drain valve <NUM>, first dialysis valve <NUM>, second dialysis valve <NUM>, heater valve <NUM>, patient valve <NUM> are clamps part of the cycler <NUM> and operating on tube sections of the drain fluid line tube <NUM>, first dialysis fluid line tube <NUM>, second dialysis fluid line tube <NUM>, heater line tube <NUM>, patient line tube <NUM>. The clamp and the tube section form together a pinch valve.

In addition, an auxiliary drain valve <NUM> works on the auxiliary drain fluid line tube <NUM> and the drain fluid line tube <NUM> merges with the auxiliary drain fluid line tube <NUM> in a common drain line before reaching the drain <NUM> (<FIG>).

The flow route from the heater bag <NUM> to the patient P and the flow route from the patient P to drain are the same shown in <FIG> and <FIG> and disclosed in the previous paragraphs (first embodiment).

The flow route from the first supply bag <NUM> to the heater bag <NUM> is the same of the second embodiment (see Table <NUM>).

A possible priming sequence is represented in the following table (Table <NUM>).

In some embodiments, the valves are part of the casing and are shaped like in <FIG>. For instance, all the valves (drain valve <NUM>, first dialysis valve <NUM>, second dialysis valve <NUM>, heater valve <NUM>, by-pass valve <NUM>, patient valve <NUM>) of embodiment two of <FIG> and <FIG> are of the type shown in <FIG>.

This kind of valves is configured to work with the occlusion element <NUM> illustrated in <FIG>, <FIG> and <FIG>.

The occlusion element <NUM> comprises the plunger <NUM>, like the one of <FIG> and <FIG>, and further comprises a mechanical tensioning plunger <NUM>. Both the plunger <NUM> and the tensioning plunger <NUM> are mechanically coupled to an actuator <NUM>, shown in <FIG> and <FIG>.

In the embodiment of <FIG>, the actuator <NUM> is a linear actuator connected to a shaft <NUM>. A distal end of the shaft <NUM> carries the plunger <NUM> and a damping and/or resilient element <NUM> (like a spring) is placed between the distal end and said plunger <NUM>. The plunger <NUM> is shaped like a cup housing the spring.

The damping and/or resilient element <NUM> allows to reduce the force exerted on the membrane <NUM> to avoid damaging said membrane <NUM>.

Like in <FIG> and <FIG>, the actuator <NUM> is configured to move the plunger <NUM> along an axial direction and between the retracted position, in which the plunger <NUM> is spaced from the soft membrane <NUM> and the port is open, and a forward position, in which the plunger <NUM> is at least in part accommodated in the seat and the soft membrane <NUM> is deformed and trapped between said plunger <NUM> and said seat to close the port.

The membrane tensioner <NUM> is configured to raise the soft membrane <NUM> away from the seat when the plunger <NUM> goes back to the retracted position and to counteract a possible negative pressure tending to keep the valve closed.

The membrane tensioner <NUM> comprises a tensioning plunger <NUM> which is also mechanically connected to the actuator <NUM>. The tensioning plunger <NUM> is shaped substantially like a cylinder, is coaxial to the plunger <NUM> and surrounds at least in part the plunger <NUM>.

The tensioning plunger <NUM> comprises two arched walls 76a coaxial to a central axis. The walls 76a are spaced one from the other to delimit two windows 76b between them (<FIG>).

The tensioning plunger <NUM> is fitted on the shaft <NUM> and is axially movable along said shaft <NUM>. Borders of the arched walls 76a of the tensioning plunger <NUM> face the soft membrane <NUM> and the plunger <NUM> may protrude from the tensioning plunger <NUM>.

The actuator <NUM> is also configured to move the tensioning plunger <NUM> between a retracted position, in which the tensioning plunger <NUM> is spaced from the soft membrane <NUM>, and a forward position, in which the tensioning plunger <NUM> engages the soft membrane <NUM> at locations other than an edge of the seat, to move away the soft membrane <NUM> from the edge and to stretch said soft membrane <NUM> above the seat.

In other embodiments, not shown, the tensioning plunger <NUM> may be moved by an auxiliary actuator, not shown.

The actuator <NUM> is housed in the box <NUM> of the cycler <NUM>; the plunger <NUM>, the tensioning plunger <NUM> and the shaft <NUM> are guided through openings fashioned in the box <NUM> of the cycler <NUM>.

The tensioning plunger <NUM> is in the retracted position when the plunger <NUM> is in the forward position (<FIG>). In this configuration, the plunger <NUM> protrudes from the tensioning plunger <NUM>.

The tensioning plunger <NUM> is in the forward position when the plunger <NUM> is in the retracted position (<FIG>). In this configuration, the plunger <NUM> is entirely housed within the tensioning plunger <NUM> and does not protrude beyond the borders of the tensioning plunger <NUM>.

The occlusion element <NUM> comprises a reverse mechanism connecting the tensioning plunger <NUM> and the plunger <NUM>. The reverse mechanism is configured to move the plunger <NUM> in an opposite direction with respect to a moving direction of the tensioning plunger <NUM> when the plunger <NUM> is moved by the actuator <NUM>.

In the embodiment of <FIG>, the tensioning plunger <NUM> comprises a projection <NUM> extending parallel to the shaft <NUM> and a rocker lever <NUM>. A first end of the rocker lever <NUM> is hinged to the shaft <NUM> of the plunger <NUM>, a second end of the rocker lever <NUM> is hinged to the projection <NUM> of the tensioning plunger <NUM> and a middle portion of the rocker lever <NUM> is hinged to a stationary part of the cycler <NUM>, for instance to a part of the box <NUM>.

When the linear actuator moves the plunger <NUM> towards the forward position, the rocker lever <NUM> tilts and moves the tensioning plunger <NUM> towards the retracted position. When the linear actuator moves the plunger <NUM> towards the retracted position, the rocker lever <NUM> tilts and moves the tensioning plunger <NUM> towards the forward position.

The variant embodiment of <FIG> comprises an additional damping and/or resilient element 75a (a spring) coupled to the tensioning plunger <NUM>. In this embodiment, the cylinder defining the tensioning plunger <NUM> is in two parts. A first part is rigidly connected to the projection <NUM>. A second part carries the borders of the arched walls 76a of the tensioning plunger <NUM> facing the membrane <NUM>. The additional damping and/or resilient element 75a is interposed between the first and the second part.

The additional damping and/or resilient element 75a allows to reduce the force exerted on the membrane <NUM> by the tensioning plunger <NUM>, to avoid damaging said membrane <NUM>. A further function of the additional damping and/or resilient element 75a is to compensate for possible plastic deformation of the membrane <NUM> that may lose elasticity and may plastically deform over time. Even if the membrane <NUM> is plastically stretched, the additional damping and/or resilient element 75a is always able to push the borders of the arched walls 76a of the tensioning plunger <NUM> against the membrane <NUM> (forward position), to move away said soft membrane <NUM> from the edge and to stretch said soft membrane <NUM> above the seat.

In the embodiment of <FIG>, the actuator <NUM> is a stepper motor comprising a rotatable shaft <NUM> connected to the shaft <NUM> of the plunger <NUM>. The rotatable shaft <NUM> has an outer thread and is coupled, through a left hand threaded coupling <NUM>, to an inner thread of the shaft <NUM>.

The shaft <NUM> has an outer thread and is coupled, through a right hand threaded coupling <NUM>, to an inner thread of the tensioning plunger <NUM>.

The tensioning plunger <NUM> and the shaft <NUM> are axially guided by a stationary element <NUM>, for instance to a part of the box <NUM>.

The rotation of the rotatable shaft <NUM> caused by the stepper motor makes the shaft <NUM> moving only axially in a first direction (the shaft <NUM> does not revolve), e.g. towards the forward position of the plunger <NUM>.

Because of the left hand threaded coupling <NUM>, the axial movement of the shaft <NUM> drives the rotation of the tensioning plunger <NUM> and, due to a different pitch of the left hand threaded coupling <NUM> and right hand threaded coupling <NUM>, also the axial movement of said tensioning plunger <NUM> in a second direction, opposite the first direction, e.g. towards a retracted position of the tensioning plunger <NUM>.

When the stepper motor moves the plunger <NUM> towards the forward position, the left hand threaded coupling <NUM> and right hand threaded coupling <NUM> work to move the tensioning plunger <NUM> towards the retracted position. When the stepper motor moves the plunger <NUM> towards the retracted position, the left hand threaded coupling <NUM> and right hand threaded coupling <NUM> work to move the tensioning plunger <NUM> towards the forward position.

In order to properly work with the plunger <NUM> and with the membrane tensioner <NUM>, the valve has a circular edge <NUM> delimiting the seat and also an auxiliary edge <NUM> extending in part around the circular edge <NUM> and spaced with respect to said edge <NUM>.

Instead of the hollow barrel <NUM> of <FIG> and <FIG>, the valve comprises a shaped member <NUM> which protrudes from the bottom surface of the respective compartment <NUM>, <NUM> and comprises the edge <NUM> and the auxiliary edge <NUM>.

The shaped member <NUM> is substantially cylindrical and delimits a central cylindrical cavity <NUM>. The edge <NUM> delimits an upper part of said cavity <NUM> and the auxiliary edge <NUM> comprises two arch shaped parts coaxial to the cavity and to the edge <NUM>.

As shown in <FIG>, the auxiliary edge <NUM> is raised with respect to the edge <NUM> such that, when the manifold assembly <NUM> is properly mounted on the site <NUM> of the cycler <NUM>, the auxiliary edge <NUM> is closer to the occlusion element than the edge <NUM>.

<FIG> show working steps of the assembly comprising the valve and the occlusion element <NUM>.

In <FIG>, the valve is closed. The plunger <NUM> is in the forward position and in part accommodated in the seat, the soft membrane <NUM> is trapped between said plunger <NUM> and the edge <NUM>.

In <FIG>, the valve is still closed even if the plunger <NUM> is partly raised, because of negative pressure which keeps the soft membrane <NUM> against the edge <NUM>.

In <FIG>, the valve is open, because the tensioning plunger <NUM> in the forward position partly surrounds the shaped member <NUM> and the auxiliary edge <NUM> and pulls the soft membrane <NUM> against the auxiliary edge <NUM>. This way, the soft membrane <NUM> is detached from the edge <NUM>.

In this position, the shaped member <NUM> is at least in part positioned inside the tensioning plunger <NUM>. Each arched wall 76a of the tensioning plunger <NUM> is placed close to one of the two arch shaped part of the auxiliary edge <NUM> and radially outside said arch shaped part of the auxiliary edge <NUM>, as shown in <FIG>.

The windows 76b face radial openings delimited between the arched walls 76a and allow fluid communication between the cylindrical cavity <NUM> and the first or second compartment <NUM>, <NUM>, therefore the valve is open (<FIG>).

The structure of valve and occlusion element <NUM> just disclosed may be also part of other kind of medical apparatuses (e.g. dialysis apparatuses for extracorporeal treatment of blood), not necessarily of the peritoneal dialysis apparatus disclosed above.

The medical apparatus may comprise a dialysis machine and a manifold assembly and the manifold assembly is mounted or mountable on the dialysis machine.

The manifold assembly comprises a casing comprising a rigid shell and at least one soft membrane, the rigid shell and soft membrane delimit at least a first fluid passage. The rigid shell comprises at least one port in fluid communication with the first fluid passage and with a second fluid passage. The at least one port has a seat and the soft membrane facing the seat.

The dialysis machine comprises at least one occlusion element <NUM> which, when the manifold assembly is properly mounted on the dialysis device, faces the seat with the soft membrane <NUM> there between. The seat is configured for accommodating, at least partially, a respective occlusion element <NUM> of the dialysis machine.

The dialysis apparatus may be an apparatus for extracorporeal treatment of blood comprising: a blood treatment device; an extracorporeal blood circuit coupled to the blood treatment device; a blood pump, wherein a pump section of the extracorporeal blood circuit being configured to be coupled to the blood pump; a treatment fluid circuit operatively connected to the extracorporeal blood circuit and/or to the blood treatment device. The treatment fluid circuit comprises a dialysis line connected to a fluid chamber of the treatment unit and a fluid evacuation line connected to the fluid chamber. The treatment fluid circuit comprises an infusion circuit comprising one or more infusion lines of a replacement fluid. The manifold assembly may be part of the extracorporeal blood circuit or of the treatment fluid circuit.

The manifold assembly <NUM> described above may be used to calibrate the peristaltic pump <NUM>, i.e. to estimate the stroke liquid volume of the yielding pump tube <NUM> connected to the peristaltic pump <NUM> in order to reach volumetric accuracy measure requirements.

The following description is referred to the manifold assembly <NUM> of the second embodiment of <FIG> and <FIG>. This embodiment is illustrated also in <FIG> and <FIG>. The upper part of the second compartment <NUM> and the air buffer volume are in fluid communication, through the hole <NUM>, the breathable membrane <NUM> and an air filter <NUM>, with an auxiliary chamber <NUM> part of the cycler <NUM>. The pressure transducer <NUM> is connected to the auxiliary chamber <NUM> and an air valve <NUM> allows to open or close communication of the auxiliary chamber <NUM> with ambient air.

The peristaltic pump <NUM> comprises an encoder or is coupled to an encoder, not shown in the attached Figures. The encoder is operatively connected to the control unit <NUM> and is configured to detect the position and movement of the pressing rollers 6a of the peristaltic pump <NUM>.

The control unit <NUM> is operatively connected the motor of the peristaltic pump <NUM>, to the first level sensor <NUM>, to the second level sensor <NUM>, to the air valve <NUM>, to the actuators of the occlusion elements <NUM> and to the pressure transducer <NUM> and is configured and/or programmed to calibrate the peristaltic pump <NUM> according to the method here detailed.

As shown in <FIG>, the first level sensor <NUM> or high level sensor and the second level sensor <NUM> or low level sensor, delimit a high level "C" and a low level "A" in the second compartment <NUM>.

A first volume "V1" is delimited in the second compartment <NUM> below the low level "A". The first volume "V1" is about <NUM>. A second volume "V2" is delimited in the second compartment <NUM> between the low level "A" and the high level "C". The second volume "V2" is between two and four times a nominal stroke liquid volume of the peristaltic pump <NUM>. The nominal stroke liquid volume of the peristaltic pump <NUM> may be <NUM> and the second volume "V2" is about <NUM>. A third volume "V3" is delimited in the second compartment <NUM> above the high level "C". The third volume "V3" is about <NUM>. The auxiliary chamber <NUM> delimits inside a fourth volume "V4" of a about <NUM>. A sum of the second, third and fourth volume is about <NUM>.

The yielding pump tube <NUM> shaped as a loop comprises a rounded part 55a and two straight parts 55b. The rounded part 55a and two straight parts 55b form a single tube. The straight parts 55b are respectively connected to the first pump port <NUM> and the second pump port <NUM>. The rounded part 55a is configured to be pressed and deformed/squeezed by the pressing rollers 6a of the peristaltic pump <NUM>.

Looking at <FIG>, if the peristaltic pump <NUM> rotates counterclockwise, each of the two pressing rollers 6a starts squeezing the rounded part 55a at a bottom portion, between the rounded part 55a and the lower of the two straight parts 55b, and releases the rounded part 55a at a top portion, between the rounded part 55a and the upper of the two straight parts 55b.

In order to calibrate the peristaltic pump <NUM>, i.e. to estimate the stroke liquid volume of the yielding pump tube <NUM>, the following procedure is performed (reference is made to <FIG>).

The drain valve <NUM>, first dialysis valve <NUM>, second dialysis valve <NUM>, by-pass valve <NUM>, patient valve <NUM> are closed. The heater valve <NUM> is open and the heater bag <NUM> is filled with water. The air valve <NUM> is open.

The control unit <NUM> controls the peristaltic pump <NUM> to start rotating counterclockwise, to pump water from the heater bag <NUM> into the first compartment <NUM> and then into the second compartment <NUM>. When the low level sensor <NUM> detects water (AII in <FIG>), the peristaltic pump <NUM> is stopped.

The peristaltic pump <NUM> is then rotated clockwise to lower the water level until water is no more detected by the low level sensor <NUM> and then stopped again (AI in <FIG>).

The peristaltic pump <NUM> is again rotated counterclockwise. When the low level sensor <NUM> detects again water (low liquid level A in <FIG> and <FIG>), the control unit <NUM> controls the peristaltic pump <NUM> to keep rotating counterclockwise and pumping water in the second compartment <NUM>. Meanwhile, the control unit <NUM> starts counting encoder pulses starting from the detection of water by the low level sensor <NUM>.

When a predetermined number of pulses "Delta_Encoder_Pulses" (e.g. <NUM> pulses), corresponding to a predetermined angle of rotation "Delta" (e.g. <NUM>°) of the peristaltic pump <NUM>, is reached and the water level is at a first level B (<FIG> and <FIG>), the air valve <NUM> is closed and the peristaltic pump <NUM> to keeps on rotating counterclockwise to pump more water in the second compartment <NUM> and to compress air in the volume above the water level.

The position of one of the two pressing rollers 6a at the end of the predetermined angle "Delta" of rotation is a predetermined position. Such predetermined position may be at a portion of the yielding pump tube <NUM> between the rounded part 55a and one of the two straight parts 55b. The water level when the pressing roller 6a is in the predetermined position is the first level B. An extra volume "Extra_Volume" of water is pumped to raise the level from the low liquid level A to the first level B (<FIG> and <FIG>).

Starting from said predetermined position of the peristaltic pump <NUM> and from the first level B, the control unit <NUM> rotates the peristaltic pump <NUM> of a counterclockwise predetermined rotation "Rotor_rev" defined by "n" half-revolutions of the peristaltic pump <NUM>, where "n" is an integer (e.g. n = <NUM>). The rotational speed of the peristaltic pump <NUM> may be <NUM> rpm.

This way, at the end of the "n" half-revolutions, the same pressing roller 6a is positioned again in the predetermined position and the water level is raised to a second level D.

Since the pressing roller 6a passes in the predetermined position several times during the "n" half-revolutions, the water level is sensed through the high level sensor <NUM> and the rotation of the peristaltic pump <NUM> is stopped when the pressing element 6a is in the predetermined position for a first time after sensing the high level C (<FIG> and <FIG>).

Air pressure in the second compartment <NUM> is measured by the pressure transducer <NUM>. An initial pressure PInit before air compression (first level B) and a final pressure PFinal after air compression (second level D) are taken. The initial pressure PInit is about <NUM> mmHg (differential pressure with respect to atmospheric pressure) and the final pressure is about <NUM> mmHg.

After stopping the rotation of the peristaltic pump <NUM> and before taking the final pressure PFinal, it is provided for waiting for a stabilizing time and keeping on measuring pressure (DI in <FIG>), to check for possible leakages.

A variation of liquid volume "Vol_Moved" in the second compartment <NUM>, due to the rotation of the peristaltic pump <NUM> of the predetermined rotation "Rotor_rev", is then calculated as a function of an initial air volume "Compensated_Volume" above the first level B and of the initial pressure PInit and the final pressure PFinal.

The initial air volume "Compensated_Volume" is a difference between a volume of air above the low liquid level "A" (i.e. V2 + V3 + V4) and the extra volume of water "Extra_Volume", wherein the extra volume of water "Extra_Volume" is the volume of water between the first level B and the low liquid level A, i.e. the volume of water moved by the rotation "Delta" of the peristaltic pump <NUM>.

The stroke liquid volume "Stroke_Vol_Press" of the peristaltic pump <NUM> is calculated as a ratio between the variation of liquid volume "Vol_Moved" and the "n" half-revolutions of the peristaltic pump <NUM>. The calculation of the stroke liquid volume "Stroke_Vol_Press" as disclosed may be executed consecutively two to five times and an average stroke liquid volume is determined.

The method of calibration may also be implemented in other medical apparatuses comprising a medical machine provided with a peristaltic pump and comprising a manifold assembly, for instance in an apparatus for extracorporeal treatment of blood of the kind above disclosed.

The procedure detailed above may be summarized through the following formulas.

Stroke_Vol_Press may be calculated from equation f. , wherein:.

Claim 1:
Medical apparatus comprising a medical machine and a manifold assembly (<NUM>), wherein the manifold assembly (<NUM>) is mounted or mountable on the medical machine;
the manifold assembly (<NUM>) comprising:
a casing (<NUM>) comprising a rigid shell (<NUM>) and at least one soft membrane (<NUM>), the rigid shell (<NUM>) and soft membrane (<NUM>) delimiting at least a first fluid passage for a fluid; the rigid shell (<NUM>) comprising at least one port in fluid communication with said first fluid passage and with a second fluid passage for the fluid; the at least one port having a seat; said at least one soft membrane (<NUM>) facing the seat of said at least one port; the seat is configured for accommodating, at least partially, a respective occlusion element (<NUM>) of the medical machine;
the medical machine comprising:
at least one occlusion element (<NUM>); said occlusion element (<NUM>), when the manifold assembly (<NUM>) is properly mounted on the medical machine, faces the seat with the soft membrane (<NUM>) there between; the occlusion element (<NUM>) comprising a plunger (<NUM>) and an actuator (<NUM>); wherein the actuator (<NUM>) is configured to move the plunger (<NUM>) between a retracted position, in which the plunger (<NUM>) is spaced from the soft membrane (<NUM>) and the port is open, and a forward position, in which the plunger (<NUM>) is at least in part accommodated in the seat and the soft membrane (<NUM>) is trapped between said plunger (<NUM>) and said seat to close the port;
characterized in that
the occlusion element (<NUM>) comprises a membrane tensioner of mechanical type; wherein the membrane tensioner is configured to raise the soft membrane (<NUM>) away from the seat when the plunger (<NUM>) goes back to the retracted position and to counteract a possible negative pressure tending to keep the port closed.