Extracorporeal blood treatment apparatus

Abstract

An apparatus (1) for extracorporeal blood treatment comprising a filtration unit (2) having a primary chamber (3) and a secondary chamber (4) separated by a semipermeable membrane (5), a blood circuit (17) comprising at least a blood withdrawal line (6) and a blood return line (7), a fluid circuit (32) comprising a fluid supply (50) for providing a sterile fluid, and at least one gas inlet (49) for allowing gas to enter the blood circuit (17). The apparatus further comprises a control unit configured to perform a blood restitution procedure to a patient to end the extracorporeal blood treatment before disconnection from the patient, said blood restitution procedure comprising the steps of infusing a predetermined amount of sterile fluid from the supply (50) into the blood circuit (17), and causing a predetermined amount of gas to enter the blood circuit (17) from the gas inlet (49).

Description

TECHNICAL FIELD

[0001] The present invention relates to a device and a method for extracorporeal blood treatment, the device being configured and the method being intended to perform an automatic blood restitution procedure before the patient is disconnected from the device. More in detail, the blood restitution procedure is performed by allowing both sterile fluids and gases to enter the blood circuit. The blood restitution procedure also allows to substantially empty the blood circuit from the liquid. BACKGROUND

[0002] The kidneys perform many functions, including removal of water, excretion of catabolites (or metabolic waste, for example urea and creatinine), regulation of the concentration of electrolytes in the blood (for example sodium, potassium, magnesium, calcium, bicarbonate, phosphate, chloride), and regulation of the acid-base balance in the body (in particular by removal of weak acids and by production of ammonium salts).

[0003] In a person who has lost his kidney function, the body accumulates water and metabolic waste and exhibits excess electrolytes, since these excretion and regulation mechanisms no longer work. To overcome renal insufficiency, it is conventionally resorted to a blood treatment involving an extracorporeal circulation within a blood circuit through an exchanger (dialyzer) having a semi-permeable membrane, in which the patient's blood circulates on one side of the membrane and a dialysis liquid, which comprises the main electrolytes of the blood, at a concentration close to that of the electrolytes in the blood of a healthy subject, circulates on the other side. The patient is connected to the extracorporeal blood circuit through a withdrawal (or arterial) line and a return (or venous) line, which have respective needles at the end portions. A pressure difference is generated between the two compartments of the dialyzer, delimited by the semi-permeable membrane, so that a portion of the plasma fluid passes through the membrane by ultrafiltration into the compartment containing the dialysis liquid. The blood treatment in the dialyzer with respect to metabolic waste and electrolytes is produced by two mechanisms of transport of molecules through the membrane. Once the treatment has terminated, the extracorporeal blood should be returned to the patient and the patient must be disconnected from the withdrawal and return blood lines of the extracorporeal blood circuit by removing the respective needles, with subsequent disposal of the blood lines. In any case, since the blood circuit is still filled with blood (if no restitution or only a partial restitution has been performed) and / or residual liquid, the lines can be at risk of contamination, resulting in high disposal costs. Moreover, disconnecting the blood lines still filled with blood, blood residues or contaminated fluid poses a serious health risk to the operator. In fact, although the end clamp can be closed to prevent dripping, the very end of the blood line, i.e. the needle, still comprises liquid which can be a potential source of contamination.

[0004] Document US5685835A relates to a device and a method for disinfecting a contaminated blood tubing set (BTS) when it is attached to a dialysis machine after a dialysis procedure. The tubing set comprises a conventional dialyzer, a blood pump, a venous line and an arterial line configured to be attached to a patient. A saline tubing is also connected to the arterial reservoir so that in case of low blood pressure during the treatment or in order to flush the dialyzer with a saline solution during the initial priming, saline can be administered directly from the saline bag to the patient. The saline bag can also be used at the end of the dialysis treatment to return the blood remaining in the BTS to the patient. Then gravity will act to draw saline from the bag into the arterial reservoir and force the blood remaining in the arterial reservoir and arterial line back into the patient. The arterial clamp is then closed so that the arterial connector can be removed from the patient. Next, the blood pump starts to draw saline from the arterial reservoir and bag through the dialyzer and the venous reservoir, forcing the remaining blood back through the venous line into the patient. Once the saline has essentially replaced all the blood in the BTS, the venous clamp is closed so that the venous connector can also be separated from the patient. Once the patient is disconnected from the arterial and venous connectors, the dialysis machine is commanded to clean and disinfect the BTS before it is detached from the machine. The cleaning procedure can comprise connecting the arterial line to a dialysate hydraulic device which is commanded to generate a supply of cleaning or disinfectant agent to be pumped through the blood pump to the BTS. In addition, the dialysate hydraulic device can also supply air to the BTS after flushing the BTS with disinfectant solution and after the BTS is removed from the patient so that the blood pump can pump air through the BTS to essentially remove the solution. In any case, air is introduced into the BTS with the patient disconnected, which means that the blood lines are still filled with saline or disinfectant solution (in particular the needle) during the patient disconnection, resulting in a risk of contaminating the operator.

[0005] Document WO0151106A1 relates to a method for emptying a blood circuit of a device for extracorporeal blood treatment at the end of a treatment session, in the case where the blood contained in the circuit has almost been returned to the patient. The device comprises a blood treatment apparatus having a first compartment and a second compartment separated from each other by a semi-permeable membrane, an arterial tube having a first end connected to the inlet of the first compartment and a second end connectable to the patient. The device further comprises a venous tube having a first end connected to the outlet of the first compartment and a second end connectable to the patient. The cleaning method comprises stopping the blood pump for the time necessary to disconnect the arterial tube from the patient and connect it to a flexible bag containing a sterile saline solution, then running the blood pump again and pushing the blood contained in the circuit through the sterile solution towards the venous needle and returning the blood to the patient. When the saline solution reaches the end of the venous tube, the blood pump is stopped. To empty the blood circuit filled with saline solution and residual blood, the venous tube is also disconnected from the patient and the second end of the arterial tube is connected to the second end of the venous tube, so that the blood circuit is closed by itself. The blood pump is run again so that the saline solution circulates in the closed circuit at a moderate flow rate, while the two pumps arranged on the dialysis circuit are run at different rates, in particular where the speed of the downstream pump is faster than the speed of the upstream pump. Thus, the liquid contained in the closed circuit is transferred through the membrane from the first compartment of the dialyzer to the second compartment of the dialyzer by filtration, then discarded through the drain tube. The document also mentions another method for cleaning the circuit, comprising pumping air in the arterial tube so as to push the blood contained in the dialyzer and in the blood circuit towards the venous needle and transfer the residual blood to the patient.

[0006] In any case, the document does not disclose any additional details regarding the air infusion procedure to make it safe, reliable and easy to implement. On the contrary, the document merely mentions the drawbacks of air infusion without proposing, disclosing or even suggesting any way to make the procedure feasible.

[0007] Scope of the invention

[0008] Therefore, the scope of the present invention is to solve, at least in part, one or more of the drawbacks and / or limitations affecting the previous solutions.

[0009] It is an object of embodiments of the present invention to provide an extracorporeal blood treatment device capable of performing a proper and safe blood return procedure, allowing the patient to be disconnected substantially dry after treatment.

[0010] It is another object of embodiments of the present invention to provide an extracorporeal blood treatment device capable of substantially emptying the blood circuit of blood, blood residues or any contaminated fluid after the treatment session, to make the subsequent disposal of the blood circuit easier, safer and cheaper.

[0011] In more detail, it is another object of embodiments of the present application to provide an extracorporeal blood treatment apparatus that can allow a safe patient disconnection, avoiding the nurse in charge of the procedure to perform alternating sterile and non-sterile steps and at the same time reducing the contamination risk for the operator in charge of the disconnection.

[0012] It is another object of embodiments of the present application to provide an extracorporeal blood treatment apparatus that can substantially clean and empty the blood line in an automatic manner, without the need to previously disconnect the patient.

[0013] It is another object of embodiments of the present application to provide an extracorporeal blood treatment apparatus that can return to the patient, after the treatment session, a significant amount of residual blood present in the blood circuit of the apparatus, while limiting the amount of dialysis fluid infused into the blood flow of the patient. SUMMARY

[0014] A first aspect relates to an apparatus (1) for extracorporeal blood treatment, comprising:

[0015] - a filtration unit (2) having a primary chamber (3) and a secondary chamber (4) separated by a semi-permeable membrane (5);

[0016] - a blood circuit (17) comprising at least:

[0017] • a blood withdrawal line (6) extending between a first end connected to an inlet of the primary chamber and a second end adapted to be connected to a patient (P); and

[0018] • a blood return line (7) extending between a first end connected to an outlet of the primary chamber (3) and a second end adapted to be connected to said patient (P);

[0019] - a fluid circuit (32) comprising at least:

[0020] • a dialysis fluid effluent line (13) connected to an outlet of the secondary chamber (4);

[0021] • a fluid supply source (50) for providing a sterile fluid, e.g. a dialysis fluid or a substitution fluid;

[0022] - optionally, at least one gas inlet (49) for allowing a gas to enter into the blood circuit (17).

[0023] In a second aspect according to the preceding aspect, the apparatus (1) further comprises a control unit (12) configured to perform a blood return procedure to the patient (P) to end the extracorporeal blood treatment, before the disconnection from the patient.

[0024] In an additional independent aspect, there is provided a method for blood return, the method being performed by the device (1) for extracorporeal blood treatment according to any one of the preceding aspects, the method comprising the step of performing a blood return procedure to end the extracorporeal blood treatment to the patient (P) before being disconnected from the patient.

[0025] In another aspect according to the two preceding aspects, the blood return procedure comprises the steps of:

[0026] - bringing a predetermined amount of gas into the secondary chamber (4) of the filtration unit (2);

[0027] - infusing a predetermined amount of sterile fluid from a supply source (50) into the blood circuit (17), the step comprising back-filtering the sterile fluid, in particular dialysis fluid, through the semi-permeable membrane (5) into the blood circuit (17),

[0028] During the back-filtering step, the secondary chamber (4) of the filtration unit is filled with both gas and sterile fluid, in particular the predetermined amount of fluid determining full or partial blood return.

[0029] In aspect 2 according to any one of the preceding aspects, the blood return procedure comprises the steps of:

[0030] infusing a predetermined amount of sterile fluid from a supply source (50) into the blood circuit (17);

[0031] bringing a predetermined amount of gas from the gas inlet (49) into the blood circuit (17).

[0032] A third aspect relates to a method for blood return, the method being performed by a device (1) for extracorporeal blood treatment, in particular the method being performed by the device (1) according to any one of the preceding aspects, wherein the device comprises:

[0033] - a filtration unit (2) having a primary chamber (3) and a secondary chamber (4) separated by a semi-permeable membrane (5);

[0034] - a blood circuit (17) comprising at least:

[0035] • a blood withdrawal line (6) extending between a first end connected to an inlet of the primary chamber and a second end for connection to a patient (P); and

[0036] • a blood return line (7) extending between a first end connected to an outlet of the primary chamber (3) and a second end for connection to the patient (P);

[0037] - a fluid circuit (32) comprising at least:

[0038] • a dialysis fluid effluent line (13) connected to an outlet of the secondary chamber (4);

[0039] • a fluid supply source (50) for providing a sterile fluid, e.g. a dialysis fluid or a substitution fluid;

[0040] - at least one gas inlet (49) for allowing a gas to enter the blood circuit (17);

[0041] wherein the method comprises a blood return procedure for ending the extracorporeal blood treatment before disconnection from the patient, said blood return procedure being performed by the control unit (12) and comprising the steps of:

[0042] infusing a predetermined amount of sterile fluid from the supply source (50) into the blood circuit (17);

[0043] allowing a predetermined amount of gas to enter the blood circuit (17) from the gas inlet (49).

[0044] During the execution of the blood return procedure, the second end of the blood withdrawal line (6) is connected to the patient (P) and the second end of the blood return line (7) is connected to the patient (P).

[0045] During the execution of the blood return procedure, the treatment of the extracorporeal blood is terminated.

[0046] In a fourth aspect according to any of the preceding aspects, the device (1) further comprises a blood pump (21) operable on the blood circuit (17).

[0047] In a fifth aspect according to any of the preceding aspects 2, 3 or 4, said infusing step of sterile fluid defines at least one fluid-blood interface (FBI) in the blood circuit (17) and the step of allowing a predetermined amount of gas to enter the blood circuit (17) defines at least one gas-fluid interface (GFI) in the blood circuit (17).

[0048] In a sixth aspect according to any of the preceding aspects, at least part of the sterile fluid is interposed between the at least one fluid-blood interface (FBI) and the at least one gas-fluid interface (GFI).

[0049] In a seventh aspect according to any of the preceding aspects, the control unit (12) is further configured to simultaneously move towards the patient (P) the following items to return part of the blood to the patient (P) before disconnection from the patient:

[0050] o at least part of the extracorporeal blood contained in the blood circuit (17),

[0051] o the at least part sterile fluid between the fluid blood interface (FBI) and the gas fluid interface (GFI), and

[0052] o at least part gas.

[0053] In an eighth aspect according to any of the preceding aspects, the predetermined amount of sterile fluid is volumetrically lower than the predetermined amount of gas.

[0054] In a ninth aspect according to any of the preceding aspects, the step of infusing a predetermined amount of sterile fluid from the dialysis fluid supply (50) into the blood circuit (17) comprises infusing sterile fluid sufficient to reach at least the position of the gas inlet (49), in particular the first gas inlet (49a).

[0055] In a tenth aspect according to any of the preceding aspects, the step of infusing a predetermined amount of sterile fluid from the dialysis fluid supply (50) into the blood circuit (17) comprises infusing sterile fluid sufficient to reach and exceed the position of the gas inlet (49), in particular the first gas inlet (49a).

[0056] In an eleventh aspect according to any of the preceding aspects, the fluid circuit (32) further comprises a dialysis fluid supply line (8) connected to the inlet of the secondary chamber (4), the fluid supply (50) being a dialysis fluid supply and providing at least dialysis fluid to the dialysis fluid supply line (8).

[0057] In a twelfth aspect according to any of the preceding aspects, the step of infusing a predetermined amount of sterile fluid from the dialysis fluid supply (50) into the blood circuit (17) comprises back-filtering dialysis fluid into the blood circuit (17) through the semi-permeable membrane (5), in particular dialysis fluid sufficient to reach at least the position of the gas inlet (49).

[0058] In a thirteenth aspect according to any of the preceding aspects, the amount of dialysis fluid is sufficient to reach and exceed the position of the gas inlet (49), in particular the first gas inlet (49a).

[0059] In a fourteenth aspect according to any of the preceding aspects, the fluid circuit (32) further comprises an infusion line (39) fluidly connected to the blood circuit (17), in particular to the blood withdrawal line (6) and / or the blood return line (7).

[0060] In a fifteenth aspect according to the preceding aspect, the infusion line (39) is configured to infuse sterile fluid into the blood circuit (17), in particular the sterile fluid being a substitution fluid or saline.

[0061] In a sixteenth aspect according to either of the two preceding aspects, the infusion line (39) is fluidically connected to the blood circuit (17) at an infusion point interposed between a first end and a second end of the blood withdrawal line (6) or of the blood return line (7).

[0062] In a seventeenth aspect according to any one of the preceding aspects, the fluid supply source (50) is a dialysis fluid supply source connected to the infusion line (39) to provide at least the infusion line (39) with dialysis fluid, or

[0063] the fluid supply source (50) is a substitution fluid supply source, in particular a container or a bag, to provide at least the infusion line (39) with substitution fluid, or

[0064] the fluid supply source (50) is a sterile fluid supply source, in particular a container or a bag (e.g. containing saline), to provide at least the infusion line (39) with sterile fluid.

[0065] In an eighteenth aspect according to any one of the preceding aspects, said step of infusing a predetermined amount of sterile fluid from the dialysis fluid supply source (50) into the blood circuit (17) comprises directly infusing the sterile fluid into the blood circuit (17) through the infusion line (39), in particular, infusing sterile fluid sufficient to reach at least the position of the gas inlet (49), in particular of the first gas inlet (49a).

[0066] In a nineteenth aspect according to any one of the preceding aspects, the amount of dialysis fluid or of substitution fluid is sufficient to reach and exceed the position of the gas inlet (49), in particular of the first gas inlet (49a).

[0067] In a twentieth aspect according to any one of the preceding aspects, the step of causing a predetermined amount of gas to enter the blood circuit (17) comprises commanding activation of the blood pump (21) to draw gas from at least one gas inlet (49).

[0068] In a twenty-first aspect according to any one of the preceding aspects, the control unit (12) is configured to perform the step of infusing a predetermined amount of sterile fluid from the supply source (50) into the blood circuit (17) to return to the patient (P) a portion of extracorporeal blood contained in the blood circuit (17).

[0069] In a twenty-second aspect according to any one of the preceding aspects, said at least one fluid blood interface (FBI) comprises a first fluid blood interface (FBI’) and a second fluid blood interface (FBI”) in the blood circuit (17).

[0070] In a twenty-third aspect according to the previous aspect, a first fluid-blood interface (FBI’) is interposed between the sterile fluid and the second end of the blood return line (7), and a second fluid-blood interface (FBI”) is interposed between the sterile fluid and the second end of the blood withdrawal line (6).

[0071] In a twenty-fourth aspect according to any one of the previous aspects, the at least one gas-fluid interface (GFI) comprises a first gas-fluid interface (GFI’) and a second gas-fluid interface (GFI”) in the blood circuit (20).

[0072] In a twenty-fifth aspect according to the previous aspect, at least part of the sterile fluid is interposed between the first fluid-blood interface (FBI’) and the first gas-fluid interface (GFI’), and / or at least part of the sterile fluid is interposed between the second fluid-blood interface (FBI”) and the second gas-fluid interface (GFI”), at least after the gas has entered the blood circuit (17).

[0073] In a twenty-sixth aspect according to any one of the previous aspects, the step of causing the gas to enter determines a division of the sterile fluid to be infused into the blood circuit (17) into a first sterile fluid portion and a second sterile fluid portion.

[0074] In a twenty-seventh aspect according to the previous aspect, the first sterile fluid portion is interposed between the first fluid-blood interface (FBI’) and the first gas-fluid interface (GFI’), and the second sterile fluid portion is interposed between the second fluid-blood interface (FBI”) and the second gas-fluid interface (GFI”).

[0075] In a twenty-eighth aspect according to any one of the two previous aspects, the blood return procedure comprises moving the first sterile fluid portion towards the second end of the blood return line (7), and simultaneously or sequentially moving the second sterile fluid portion towards the second end of the blood withdrawal line (6).

[0076] In a twenty-ninth aspect according to any one of the previous aspects, the blood return procedure comprises moving the first fluid-blood interface (FBI’) and the first gas-fluid interface (GFI’) towards the second end of the blood return line (7), and moving the second fluid-blood interface (FBI”) and the second gas-fluid interface (GFI”) towards the second end of the blood withdrawal line (7).

[0077] In a thirtieth aspect according to any one of the previous aspects, the volume of the first sterile fluid portion and / or of the second sterile fluid portion is comprised between 50 ml and 200 ml.

[0078] In a thirty-first aspect according to any one of the preceding aspects, the at least one gas inlet (49) comprises a first gas inlet (49a) arranged on the blood return line (7) and a second gas inlet (49b) arranged on the blood withdrawal line (6).

[0079] In a thirty-second aspect according to the preceding aspect, the blood pump (21) is arranged on the blood withdrawal line (6).

[0080] In a thirty-third aspect according to any one of the preceding aspects, the second gas inlet (49b) is interposed between the blood pump (21) and the second end of the blood withdrawal line (6).

[0081] In a thirty-fourth aspect according to any one of the preceding aspects, the device (1) comprises an air separator (19a) arranged on the blood return line (7) and, optionally, an auxiliary air separator (19b) arranged on the blood withdrawal line (6).

[0082] In a thirty-fifth aspect according to the preceding aspect, the at least one gas inlet (49) is arranged at said air separator (19a).

[0083] In a thirty-sixth aspect according to any one of the two preceding aspects, the first gas inlet (49a) is arranged on the air separator (19a) and, optionally, the second gas inlet (49b) is arranged on the auxiliary air separator (19b).

[0084] In a thirty-seventh aspect according to any one of the preceding aspects, the infusion line (39) is connected to at least one of the air separator (19a) and the auxiliary air separator (19b).

[0085] In a thirty-eighth aspect according to any one of the preceding aspects, the device (1) comprises at least one shut-off element (59), in particular at least one valve or clamp, connected to said at least one gas inlet (49).

[0086] In a thirty-ninth aspect according to any one of the preceding aspects, the device comprises a first shut-off element (59a) connected to the first gas inlet (49a) and a second shut-off element (59b) connected to the second gas inlet (49b), the control unit (12) being configured to command the at least one shut-off element (59) between an open position, in which gas flow is allowed, and a closed position, in which gas flow is prevented, or the method comprises the step of commanding the at least one shut-off element (59) between an open position, in which gas flow is allowed, and a closed position, in which gas flow is prevented.

[0087] In a forty-first aspect according to any of the preceding aspects, the safety clamp (20a, 20b) is arranged closer to the vascular access (18) of the patient (P) than the respective one of the first and second gas inlets (49).

[0088] In a forty-first aspect according to any of the preceding aspects, the safety clamp (20a, 20b) is arranged closer to the vascular access (18) of the patient (P) than the respective one of the first and second gas inlets (49).

[0089] In a forty-second aspect according to any of the two preceding aspects, the control unit (12) is configured to command the blood return safety clamp (20a) and the blood withdrawal safety clamp (20b) between an open position, which allows the flow, and a closed position, which prevents the flow.

[0090] In a forty-third aspect according to any of the preceding aspects, the control unit (12) is configured to perform a restitution procedure according to a first configuration, or the method comprises performing a restitution procedure according to a first configuration, said restitution procedure comprising sequentially performing the following steps:

[0091] - commanding the infusion of a predetermined amount of sterile fluid into the blood circuit (17) through the infusion line (39) or through the semi-permeable membrane (5) counter-filtering the dialysis fluid, said step determining the position of the sterile fluid beyond the gas inlets (49), in particular the first gas inlet (49a), said step defining a first fluid-blood interface and a second fluid-blood interface (FBI', FBI");

[0092] - commanding a first shut-off element (59a) of the first gas inlet (49a) on the blood return line (7) to be in an open position, a second shut-off element (59b) of the second gas inlet (49b) on the blood withdrawal line (6) to be in a closed position, the blood return safety clamp (20a) to be in a closed position, the blood withdrawal safety clamp (20b) to be in an open position;

[0093] - commanding the activation of the blood pump (21) in a direction towards the second end of the blood withdrawal line (6) to draw a predetermined amount of gas from the first gas inlet (49a) into the blood circuit (17), this step defining a first gas-fluid interface GFI' and a second gas-fluid interface GFI" and determining the movement of the second gas-fluid interface (GFI") and of the second fluid-blood interface (FBI") towards the second end of the blood withdrawal line (6), thereby performing a partial blood restitution to the patient (P) through the blood withdrawal line (6).

[0094] In a forty-fourth aspect according to the preceding aspect, said restitution procedure according to the first configuration further comprises sequentially performing the following steps:

[0095] - commanding the blood withdrawal safety clamp (20b) to be in the closed position, the blood return safety clamp (20a) to be in the open position, the first shut-off element (59a) of the first gas inlet (49a) on the blood return line (7) to be in the closed position, the second shut-off element (59b) of the second gas inlet (49b) on the blood withdrawal line (6) to be in the open position;

[0096] - commanding the activation of the blood pump (21) in a direction towards the second end of the blood return line (7), this step determining the movement of at least one gas fluid interface (GFI), in particular of the first gas fluid interface (GFI') and of the first fluid blood interface (FBI') towards the second end of the blood return line (7), so as to cause a quantity of blood to be returned to the patient (P) through the blood return line (7);

[0097] Optionally, before the step of infusing a sterile fluid into the blood circuit (17), at least one between the blood return safety clamp (20a) and the blood withdrawal safety clamp (20b) is commanded to be in the open position, in particular:

[0098] the blood return safety clamp (20a) is in the open position; and

[0099] the blood withdrawal safety clamp (20b) is in the closed position or the blood pump (21) is stopped.

[0100] In a forty-fifth aspect according to any of the preceding aspects, according to a second configuration, the returning procedure implies the sequential execution of the following steps:

[0101] - commanding the infusion of a predetermined quantity of sterile fluid into the blood circuit (17) through the infusion line (39) or through the semi-permeable membrane (5) counter-filtering the dialysis fluid, said step determining the position of the sterile fluid beyond the gas inlet (49) arranged on the blood return line (7), said step defining a first fluid blood interface and a second fluid blood interface (FBI', FBI");

[0102] - optionally, determining the partial blood return through the blood return line (7) due to the infusion of the sterile fluid, the blood return safety clamp (20a) being in the open position;

[0103] - commanding the shut-off element (59) of the gas inlet (49) to be in the open position, the blood return safety clamp (20a) to be in the closed position, the blood withdrawal safety clamp (20b) to be in the open position;

[0104] - commanding the activation of the blood pump (21) in a direction towards the second end of the blood withdrawal line (6) to draw a predetermined amount of gas from the gas inlet (49) into the blood circuit (17), the step determining the movement of at least one gas-fluid interface (GFI), in particular of the second gas-fluid interface (GFI") and of the second fluid-blood interface (FBI") towards the second end of the blood withdrawal line (6), thereby performing blood restitution to the patient (P) through the blood withdrawal line (6).

[0105] In a forty-sixth aspect according to any one of the preceding aspects, according to a fourth configuration, the restitution procedure implies the sequential execution of the following steps:

[0106] - commanding the infusion of a predetermined amount of sterile fluid into the blood circuit (17) through the infusion line (39) or through the semi-permeable membrane (5) counter-filtering the dialysis fluid, the step determining the position of the sterile fluid beyond the gas inlet (49) arranged on the blood withdrawal line (6), the step defining the first and second fluid-blood interfaces (FBI', FBI");

[0107] - optionally, determining a partial blood restitution through the blood withdrawal line (6) due to the sterile fluid infusion, the blood withdrawal safety clamp (20b) being in the open position;

[0108] - commanding the occlusion element (59) of the gas inlet (49) to be in the open position, the blood withdrawal safety clamp (20b) to be in the closed position, the blood return safety clamp (20a) to be in the open position;

[0109] - commanding the activation of the blood pump (21) in a direction towards the second end of the blood return line (7) to draw a predetermined amount of gas from the gas inlet (49) into the blood circuit (17), the step determining the movement of at least one gas-fluid interface (GFI), in particular of the first gas-fluid interface (GFI') and of the first fluid-blood interface (FBI') towards the second end of the blood return line (7), thereby performing blood restitution to the patient (P) through the blood return line (7).

[0110] In a forty-seventh aspect according to any one of the preceding aspects, the device (1) comprises a gas supply unit (60) connected to at least one gas inlet (49), in particular to the first gas inlet (49a) and / or to the second gas inlet (49b), and configured to force the infusion of gas into the blood circuit (17), in particular the gas supply unit (60) being a gas pump.

[0111] In a forty-eighth aspect according to any one of the preceding aspects, according to a third configuration, the restitution procedure implies the sequential execution of the following steps:

[0112] - commanding the infusion of a predetermined amount of sterile fluid into the blood circuit (17) through the infusion line (39) or through the semi-permeable membrane (5) counter-filtering the dialysis fluid, said step determining the position of the sterile fluid beyond the gas inlet (49), in particular the position of the first gas inlet (49a), said step defining a first fluid-blood interface and a second fluid-blood interface (FBI', FBI");

[0113] - commanding the occlusion element (59) of said at least one gas inlet (49) to be in an open position;

[0114] - commanding at least one of the blood return safety clamp (20a) and the blood withdrawal safety clamp (20b) to be in an open position;

[0115] - commanding the activation of the gas supply unit (60) to infuse gas into the blood circuit (17), the step determining the movement of at least one gas-fluid interface (GFI) and at least one fluid-blood interface (FBI) towards the second end of the blood withdrawal line (6) so as to return an amount of blood to the patient (P) through the blood withdrawal line (6), and / or the movement of at least one gas-fluid interface (GFI) and at least one fluid-blood interface (FBI) towards the second end of the blood return line (7) so as to return an amount of blood to the patient (P) through the blood return line (7), in particular the step determining:

[0116] o the second gas-fluid interface GFI" and the second fluid-blood interface FBI" moving towards the second end of the blood withdrawal line 6 so as to return an amount of blood to the patient P through the blood withdrawal line 6; and / or

[0117] o the first gas-fluid interface GFI' and the first fluid-blood interface FBI' moving towards the second end of the blood return line 7 so as to return an amount of blood to the patient P through the blood return line 7;

[0118] Optionally, before the step of infusing sterile fluid into the blood circuit (17), at least one of the blood return safety clamp (20a) and the blood withdrawal safety clamp (20b) is commanded to be in an open position.

[0119] In a forty-ninth aspect according to any of the preceding aspects, the control unit (12) is configured to, or the method comprises, commanding the position of the blood return safety clamp (20a) or of the blood withdrawal safety clamp (20b) during the step of infusing gas into the blood circuit (17) by the gas supply unit (60) according to the third configuration of the return procedure, so as to determine:

[0120] - simultaneous blood restitution through the blood withdrawal line (6) and the blood return line (7) when both the blood return safety clamp (20a) and the blood withdrawal safety clamp (20b) are commanded in the open position, in particular wherein the first fluid-blood interface (FBI') and the first gas-fluid interface (GFI') move towards the second end of the blood return line (7) and the second fluid-blood interface (FBI") and the second gas-fluid interface (GFI") move towards the second end of the blood withdrawal line (6); or

[0121] - arterial blood restitution through the blood withdrawal line (6) when the blood return safety clamp (20a) is commanded in the closed position and the blood withdrawal safety clamp (20b) is commanded in the open position, in particular wherein the second fluid-blood interface (FBI") and the second gas-fluid interface (GFI") move towards the second end of the blood withdrawal line (6); or

[0122] - venous blood restitution through the blood return line (7) when the blood return safety clamp (20a) is commanded in the open position and the blood withdrawal safety clamp (20b) is commanded in the closed position, in particular wherein the first fluid-blood interface (FBI') and the first gas-fluid interface (GFI') move towards the second end of the blood return line (7).

[0123] In a fiftieth aspect according to any one of the preceding aspects, the second configuration and / or the third configuration and / or the fourth configuration of the blood restitution procedure implies that the device (1) comprises a single gas inlet (49).

[0124] In a fifty-first aspect according to any one of the preceding aspects, the device (1) comprises a single gas inlet (49).

[0125] In a fifty-second aspect according to any one of the preceding aspects, the device (1) comprises a dialysis fluid pump (25) located on the dialysis fluid supply line (8) and optionally a dialysate pump (26) located on the dialysis fluid effluent line (13),

[0126] The control unit (12) is configured to activate the dialysis fluid pump (25) and optionally the dialysate pump (26) to perform the step of infusing a predetermined amount of sterile fluid into the blood circuit (17) through the membrane (5) of the filtration unit (2) or to provide fluid to the infusion line (39).

[0127] In a fifty-third aspect according to any one of the preceding aspects, the device comprises an infusion pump (43) arranged on the infusion line (39) and configured to pump a predetermined amount of sterile fluid into the blood circuit (17).

[0128] In a fifty-fourth aspect according to any of the preceding aspects, the blood pump (21) is a peristaltic occlusion blood pump.

[0129] In a fifty-fifth aspect according to any of the preceding aspects, the blood pump (21) is configured to determine or prevent a flow, in particular of blood, sterile fluid and gas, in particular the blood pump is arranged to prevent a fluid flow towards the second end of the blood withdrawal line (6).

[0130] In a fifty-sixth aspect according to any of the preceding aspects, the control unit (12) is configured to, or the method comprises, stopping the restitution procedure when the at least one fluid blood interface (FBI) approaches at least one of the second end of the blood withdrawal line (6) and the second end of the blood return line (7), or when a pre-set amount of sterile fluid has been infused into the patient.

[0131] In a fifty-seventh aspect according to any of the preceding aspects, the control unit (12) is configured to, or the method comprises, stopping the restitution procedure when at least one gas fluid interface (GFI) reaches a pre-set distance of less than 10 cm, in particular less than 5 cm, from at least one of the second end of the blood withdrawal line (6) and the second end of the blood return line (7), the distance being measured along the respective blood line.

[0132] In a fifty-eighth aspect according to any of the preceding aspects, the control unit is configured to, or the method comprises, infusing sterile fluid into the blood circuit (17) and bringing gas into the blood circuit (17) such that a distance between the fluid blood interface (FBI) and the gas fluid interface (GFI) is comprised between 0.5 cm and 10 cm, in particular between 1 cm and 5 cm, in particular the distance being measured along the respective blood line.

[0133] In a fifty-ninth aspect according to any of the preceding aspects, the pre-determined amount of sterile fluid is comprised between 5% and 80%, in particular between 10% and 60%, of the volume of the pre-determined amount of gas.

[0134] In a sixtieth aspect according to any of the preceding aspects, the blood circuit (17) defines a blood circuit internal volume, in particular the blood circuit internal volume is determined at least by the internal volume of the blood withdrawal line (6), the blood return line (7), optionally the blood circuit internal volume is also determined by the air separator (19), in particular the first air separator (19a) and the auxiliary air separator (19b), and the main chamber (3) of the filtration unit (2).

[0135] In a sixty-first aspect according to the preceding aspects, the predetermined volume of sterile fluid is comprised between 1% and 60%, in particular between 2% and 40%, more particularly between 5% and 30% of the blood circuit internal volume.

[0136] In a sixty-second aspect according to any one of the preceding aspects, the predetermined volume of gas is lower than the blood circuit internal volume.

[0137] In a sixty-third aspect according to any one of the three preceding aspects, the total infusion volume is defined by the sum of the predetermined volume of sterile fluid and the predetermined volume of gas, said total infusion volume being comprised between 60% and 160% of the blood circuit internal volume.

[0138] In a sixty-fourth aspect according to any one of the preceding aspects, the step of infusing the predetermined volume of sterile fluid in the blood circuit (17) precedes the step of bringing the predetermined volume of gas into the blood circuit (17).

[0139] In a sixty-fifth aspect according to any one of the preceding aspects, the blood withdrawal line (6) and the blood return line (7) are made of a transparent material, in particular so that the position of the fluid-blood interface (FBI) and / or of the gas-fluid interface (GFI) is visible at least during the restitution procedure.

[0140] In a sixty-sixth aspect according to any one of the preceding aspects, the blood circuit (17) comprises at least one gas sensor arranged close to the second end of the blood withdrawal line (6) and / or to the second end of the blood return line (7), said gas sensor being configured to provide a signal representative of the presence of gas in the respective blood line, the control unit (12) being configured to, or the method comprising, receiving said signal and stopping the progression of at least one gas-fluid interface (GFI), in particular the control unit being configured to implement at least one of the following operations depending on the signal representative of the presence of gas:

[0141] - stopping the blood pump (21) or the gas supply unit (60);

[0142] - moving the blood withdrawal shut-off element (20b) to the closed position if the presence of gas is detected by the gas sensor of the blood withdrawal line (6);

[0143] - moving the blood return shut-off device (20a) to the closed position if the presence of gas is detected by the gas sensor of the blood return line (7).

[0144] In a sixty-seventh aspect according to any one of the preceding aspects, the gas supply unit (60) is a gas pump configured to supply gas to the blood circuit (17) or to a manually or automatically commanded syringe at a pressure higher than the pressure existing in the blood circuit (17).

[0145] In a sixty-eighth aspect according to any one of the preceding aspects, during a blood return procedure, in particular during gas infusion, both the blood withdrawal line (6) and the blood return line (7) are connected to the cardiovascular access (18) of the patient (P).

[0146] In a sixty-ninth aspect according to any one of the preceding aspects, the step of infusing a predetermined amount of sterile fluid determines a partial return of blood to the patient, in particular a volume of blood returned to the patient that is substantially equal to the volume of the predetermined amount of sterile fluid.

[0147] In the seventieth aspect according to any one of the preceding aspects, the step of infusing a predetermined amount of sterile fluid determines a partial return of blood to the patient, and the step of infusing a predetermined amount of gas determines a further return of blood to the patient, the volume of the partial blood return due to the infusion of the sterile fluid being smaller than the volume of the blood return determined by the infusion of the gas.

[0148] In a seventy-first aspect according to any one of the preceding aspects, the predetermined amount of sterile fluid is comprised between 50 ml and 200 ml.

[0149] In a seventy-second aspect according to any one of the preceding aspects, the predetermined amount of gas is comprised between 200 ml and 700 ml, said values ​​being measured at 25° and atmospheric pressure.

[0150] In a seventy-third aspect according to any one of the preceding aspects, the infused gas is air.

[0151] In a seventy-fourth aspect according to any one of the preceding aspects, during the blood return procedure, in particular during the steps of infusing a predetermined amount of sterile fluid and admitting a predetermined amount of gas into the blood circuit (17), the blood circuit (17) is not a closed loop, in particular, wherein the second ends of the blood extraction line (6) and the blood return line (7) are not connected to each other to define a closed loop.

[0152] In a seventy-fifth aspect according to any one of the preceding aspects, the inlet of the secondary chamber (4) of the filter unit (2) is arranged at a lower level relative to the outlet of the secondary chamber (4) of the filter unit (2).

[0153] In a seventy-sixth aspect according to any one of the preceding aspects, the blood return procedure comprises the step of allowing a predetermined amount of gas to enter the secondary chamber (4) of the filtration unit (2), in particular, the semipermeable membrane is wetted and no gas passes through the semipermeable membrane.

[0154] In a seventy-seventh aspect according to any of the preceding aspects, during the step of back-filtrating the dialysis fluid through the membrane (5), the secondary chamber (4) of the filtration unit is filled with gas and sterile fluid.

[0155] In a seventy-eighth aspect according to any of the preceding aspects, wherein the secondary chamber (4) defines, at least during said blood return procedure, an internal volume filled with a quantity of gas higher than the quantity of said sterile fluid, in particular wherein the internal volume of the secondary chamber (4) is filled with 60% of gas, more particularly with 75% of gas, even more particularly with 90% of gas.

[0156] In a seventy-ninth aspect according to any of the preceding aspects, at least one of the supply line (8) and the dialysis fluid effluent line (13) comprises a gas inlet configured to allow gas to enter the fluid circuit (32), in particular said gas inlet comprises a shut-off element (e.g. a valve or a clamp) movable between an open position and a closed position to allow or prevent gas passage, respectively, said shut-off element being connected to the control unit (12) configured to command the open position or the closed position.

[0157] In an eightieth aspect according to any of the preceding aspects, the step of allowing gas to enter the secondary chamber (4) of the filtration unit comprises commanding at least one of the dialysis supply pump (25) and the dialysate pump (26) to suck gas from the gas inlet of the fluid circuit (32).

[0158] In an eighty-first aspect according to any of the preceding aspects, the fluid circuit (32) comprises a gas supply unit fluidically connected to a gas inlet of the fluid circuit (32), in particular said gas inlet is arranged on at least one of the dialysis fluid supply line (8) and the dialysis fluid effluent line (13), said gas supply unit being configured to infuse gas into the fluid circuit (32) or directly into the secondary chamber (4) of the filtration unit (2).

[0159] In an eighty-second aspect according to any of the preceding aspects, the device comprises a gas sensor, in particular associated with the filtration unit (2), configured to provide a signal representative of the presence of gas and / or of the quantity of gas comprised in the filtration unit (2), in particular in the secondary chamber (4) of the filtration unit (2), said gas sensor being for example a weight sensor or a level sensor of the dialysis fluid present in the secondary chamber (4) of the filtration unit (2).

[0160] In an eighty-third aspect according to any of the preceding aspects, the predetermined quantity of infusion fluid is able to fill the entire blood circuit.

[0161] In an eighty-fourth aspect according to any one of the preceding aspects, the back filtration step means the passage of sterile fluid, in particular dialysis fluid, from the secondary chamber (4) to the primary chamber (3) of the filtration unit (2).

[0162] In an eighty-fifth aspect according to any one of the preceding aspects, the blood restitution procedure comprises a push-pull procedure during the step of back-filtering the sterile fluid, the push-pull procedure comprising the sequential execution of the following steps:

[0163] - commanding the blood withdrawal safety clamp 20b and the blood return safety clamp 20a to be in the closed position, the shut-off element 59 of the gas inlet 49 of the blood return line 7 to be in the open position,

[0164] - activating the blood pump 21 towards the second end of the blood withdrawal line 6, in particular said step determines the suction of gas from said gas inlet 49 into the blood circuit 17 and optionally the compression of the gas comprised between the blood pump 21 and the blood withdrawal safety clamp 20b;

[0165] - commanding the shut-off element 59 of the gas inlet 49 of the blood return line 7 to be in the closed position, the blood return safety clamp 20a to be in the open position;

[0166] - activating the blood pump 21 towards the second end of the blood return line 7, in particular said step determines the movement of the residual fluid through the blood return line 7 towards the patient, more particularly said step determines the movement of the first gas-fluid interface GFI' towards the second end of the blood return line 7;

[0167] - optionally, the previous steps of the push-pull procedure are repeated in a cycle.

[0168] In an eighty-sixth aspect according to the preceding aspects, said push-pull procedure is implemented at the end of the blood restitution procedure according to the second configuration.

[0169] In an eighty-seventh aspect according to any one of the preceding aspects, the blood restitution procedure comprises a push-pull procedure during the step of back-filtering the sterile fluid, the push-pull procedure comprising the sequential execution of the following steps:

[0170] - commanding the blood withdrawal safety clamp 20b and the blood return safety clamp 20a to be in the closed position, the shut-off element 59 of the gas inlet 49 of the blood withdrawal line 6 to be in the open position,

[0171] - activating the blood pump 21 towards the second end of the blood return line 7, in particular said step determines the suction of gas from said gas inlet 49 into the blood circuit 17 and optionally the compression of the gas comprised between the blood pump 21 and the blood return safety clamp 20a;

[0172] - the shut-off element 59 of the gas inlet 49 of the blood withdrawal line 6 is in the closed position and the blood withdrawal safety clamp 20b is in the open position;

[0173] - the blood pump 21 is activated towards the second end of the blood withdrawal line 6, in particular said step determines that the residual fluid moves through the blood withdrawal line 6 towards the patient, more in particular said step determines that the second gas-fluid interface GFI” moves towards the second end of the blood withdrawal line 6;

[0174] - optionally, the previous steps of the push-pull procedure are repeated in a cycle.

[0175] In an eighty-eighth aspect according to the previous aspects, said push-pull procedure is implemented at the end of a blood return procedure according to the fourth configuration.

[0176] In an eighty-ninth aspect according to any one of the previous aspects, the blood return procedure comprises a step of infusing a predetermined amount of sterile fluid from a supply source (50) into the blood circuit (17), said step determining a full blood return to the patient, in particular so that the blood circuit is substantially completely filled with sterile fluid.

[0177] In a ninetieth aspect according to any one of the previous aspects, the blood return procedure comprises a step of back-filtering a predetermined amount of sterile fluid from a supply source (50) into the blood circuit (17), and comprises at least one of:

[0178] - moving the sterile fluid towards the blood withdrawal line and up to the patient’s vascular access to return the extracorporeal blood contained in the blood withdrawal line, in particular wherein the control unit is configured to drive the blood pump (21) to direct the fluid towards the vascular access;

[0179] - moving the sterile fluid towards the blood return line and up to the patient’s vascular access to return the extracorporeal blood contained in the blood return line, in particular wherein the control unit is configured to drive the dialysis pump (25) and / or the dialysate pump (26) and / or the blood pump (21) to direct the fluid towards the vascular access.

[0180] In a ninetieth aspect according to the previous aspects, at the end of the blood return procedure, the blood circuit is substantially completely filled with sterile fluid. BRIEF DESCRIPTION OF DRAWINGS

[0181] Some embodiments and aspects of the present application will be described below with reference to the attached drawings, provided merely for illustrative purposes, in which:

[0182] - Figure 1 is a schematic view of a blood treatment apparatus according to a general embodiment of the present application;

[0183] - Figure 2 andFigure 2A is a magnified schematic view of a blood treatment apparatus according to an embodiment of the present application during a step of sterile fluid infusion into the blood circuit;

[0184] - Figure 3 , Figure 4 and Figure 5 is a magnified schematic view of a blood treatment apparatus according to an embodiment of the present application during sequential steps of gas infusion into the blood circuit;

[0185] - Figure 6 is a magnified schematic view of a blood treatment apparatus according to another embodiment of the present application during a gas infusion step;

[0186] - Figure 7 is a magnified schematic view of a blood treatment apparatus according to another embodiment of the present application during a sterile fluid infusion step;

[0187] - Figure 8 and Figure 9 is a magnified schematic view of a blood treatment apparatus according to another embodiment of the present application during a gas infusion step;

[0188] - Figure 10 and Figure 11 is a magnified schematic view of a blood treatment apparatus according to another embodiment of the present application;

[0189] - Figure 12 and Figure 13 are flowcharts comprising the main steps for performing a blood return procedure according to different embodiments.

[0190] Definitions

[0191] In this detailed description, corresponding parts shown in the various figures are denoted by the same reference numerals. The figures can be shown by non-proportional representation of the present application; therefore, the parts and components shown in the figures that are relevant to the purpose of the present application can only refer to a schematic representation.

[0192] Upstream and / or downstream

[0193] The terms upstream and downstream refer to the direction of travel or trajectory of the fluid, in particular blood, configured to flow within the connectors or along the fluid lines during extracorporeal blood treatment.

[0194] Sterile fluid

[0195] The sterile fluid referred to in the following description and claims can be any fluid that is compatible with infusion in a blood circuit of a treatment device that may be fluidically connected to the patient's vascular system and that also meets sufficient safety standards for infusion into the patient. Thus, the sterile fluid can be a sterile aqueous solution, a saline solution, a replacement fluid containing electrolytes (e.g., glucose, sodium, chloride, potassium, calcium, magnesium, or glucose). The sterile fluid can also be the dialysis fluid employed by the device during extracorporeal blood treatment. DETAILED DESCRIPTION

[0196] Blood processing device 1

[0197] Figure 1 An extracorporeal blood treatment apparatus 1 according to a general embodiment is shown. An example of a hydraulic circuit 100 is also schematically shown, but it should be noted that the specific structure of the hydraulic circuit 100 is irrelevant to the purpose of the present invention, so different structures can be used according to the functions and design requirements of each individual medical device. Figure 1 Other loops that are different from those specifically shown in FIG.

[0198] The hydraulic circuit 100 presents a dialysis fluid circuit 32 having at least one dialysis fluid supply line 8. Depending on the treatment mode of the device, the dialysis fluid supply line 8 may or may not adopt a different hydraulic circuit line configuration.

[0199] In hemodialysis (HD) treatment mode, the supply line 8 is used to transport dialysis fluid from at least one source 14 toward a treatment station 15, where one or more filtration units 2 or dialyzers operate. The dialysis fluid and blood are exchanged primarily by diffusion through the semipermeable membrane 5 in the filtration unit 2. In hemofiltration (HF) treatment mode, the supply line 8 includes an infusion line 39, which is used to transport infusion fluid from at least one source 14 to the blood circuit. The infusion line 39 may include an ultrafilter 44 to additionally filter fluid received upstream of the injection point into the blood circuit. Removal of waste products from the blood is achieved by using large amounts of ultrafiltration in the blood circuit and simultaneously reinfusing sterile replacement fluid. In hemodiafiltration (HDF) treatment mode, the supply line 8 is used to transport dialysis fluid from the source 14 to the treatment station 15, and also includes an infusion line 39 to transport infusion fluid from the source 14 to the blood circuit 17. HDF is a combination of hemodialysis and hemofiltration.

[0200] Typically, although not necessarily, the source 14 of the supply line 8 and the infusion line 39 is the same (i.e., the dialysis fluid preparation device 9). Of course, different sources may be used. Furthermore, the supply line 8 typically branches into the infusion line 39, which infuses the fluid into the blood circuit 17, and into the inlet line 45 which directs the fluid to the processing station 15.Figure 1 , the branch point is indicated by reference numeral 46 .

[0201] Despite the fact that different hydraulic circuits 100 can be used to provide HF, HD, and HDF treatments, and have associated lines dedicated to specific treatments (e.g., no infusion line 39 for HD, no inlet line 45 for HF), the hydraulic circuit 100 is generally Figure 1 and comprises both an infusion line 39 and an inlet line 45, wherein the control unit 12 of the device can then control the passage of fluid through said lines, for example by appropriate valves or clamps, depending on the chosen treatment.

[0202] The dialysis fluid circuit 32 also comprises at least one dialysis effluent line 13 for conveying the dialysis fluid (spent dialysate and fluid ultrafiltered from the blood through the semipermeable membrane 5) from the treatment station 15 towards the evacuation zone (at Figure 1 Schematically represented by 16) transport.

[0203] The hydraulic circuit cooperates with the blood circuit 17 and also Figure 1 The basic components are schematically shown in FIG. 1 . The specific structure of the blood circuit is not essential to the present invention. Figure 1 , a brief description of possible embodiments of the blood circuit is given, which however is provided merely by way of non-limiting example.

[0204] Figure 1 The blood circuit 17 comprises a blood extraction line 6 designed to remove blood from the vascular access 18 and a blood return line 7 designed to return processed blood to the vascular access 18 . Figure 1 The blood circuit 17 also includes a main chamber 3 or blood chamber of the blood filtration unit 2, while the secondary chamber 4 of the blood filtration unit 2 is connected to the hydraulic circuit 100. In more detail, the blood extraction line 6 is connected at the inlet of the main chamber 3, and the blood return line 7 is connected at the outlet of the main chamber 3. In an embodiment, the blood return line 7 and / or the blood extraction line 6 are made of a transparent material so that the fluid flowing inside the pipeline is visible from the outside, that is, the blood line can be made of plastic or PVC or silicone transparent material. Subsequently, the dialysis fluid supply line 8 is connected at the inlet of the secondary chamber 4, and the dialysis effluent line 13 is connected at the outlet of the secondary chamber 4. As mentioned, the filtration unit 2 (e.g., dialyzer or plasma filter or blood filter or hemodialysis filter) includes two chambers 3 and 4, which are separated by a semipermeable membrane 5, for example of hollow fiber type or plate type.

[0205] The blood circuit 17 may also comprise one or more air separators 19, in particular, such as Figure 1As shown, the device comprises an air separator 19a arranged on the blood return line 7 and an auxiliary air separator 19b arranged on the blood withdrawal line 6. Anyway, as shown in Figure 6 , Figure 7 , Figure 8 the device can comprise a single air separator 19a arranged on the blood return line 7, anyway not excluding a device having a single air separator 19b arranged on the blood withdrawal line 6.

[0206] According to an embodiment of the device as shown in Figures 1 to 6 , the air separator 19a of the blood return line 7 is arranged close to the filtration unit 2. According to another embodiment, the air separators 19 of the return line 7 and / or of the withdrawal line 6 can also be arranged at different positions, for example as close as possible to the second end of the return line 7 and / or of the withdrawal line 6, respectively, as shown in Figure 7 and Figure 8 . The blood circuit 17 defines a sum of the internal volumes of at least the blood withdrawal line 6, the blood return line 7, the main chamber 3 of the filtration unit 2, the internal volume of the air separator 19, in particular of the air separator 19a and of the auxiliary air separator 19b.

[0207] The device further comprises a safety clamp 20 arranged close to the vascular access 18 of the patient. In particular, the device can comprise a blood return safety clamp 20a and a blood withdrawal safety clamp 20b arranged on the blood return line 7 and on the blood withdrawal line 6, respectively. According to the blood flow direction assumed during the dialysis treatment from the blood withdrawal line 6 through the filter unit 2 and towards the blood return line 7, the blood return safety clamp 20a is arranged downstream with respect to the air separator 19a, while the blood withdrawal safety clamp 20b is arranged upstream with respect to the auxiliary air separator 19b. When it is necessary to shut down the blood return to the vascular access 18, for example for safety reasons, the safety clamp 20 can be activated by the control unit (or manually) to shut down the blood return line 7.

[0208] The extracorporeal blood treatment device 1 can further comprise one or more blood pumps 21, for example positive displacement pumps such as peristaltic pumps. In Figure 1In the example of Fig. 1, a blood pump 21 is arranged on the blood withdrawal line 6, in particular interposed between the filter unit 2 and the auxiliary air separator 19b. In another embodiment, more than one blood pump 21 can be arranged on the blood circuit 17, for example a first blood pump arranged on the withdrawal line 6 and a second blood pump arranged on the return line 7. The blood return line 7 extends between a first end connected to the outlet of the main chamber 3 of the filter unit 2 and a second end connected to the patient. Similarly, the blood withdrawal line 6 extends between a first end connected to the inlet of the main chamber 3 of the filter unit 2 and a second end connected to the patient. According to the embodiment of the device shown in the figures, the air separator 19a is arranged on the blood return line 7 and interposed between the first and second ends of the blood return line 7. The auxiliary air separator 19b is arranged on the blood withdrawal line 6 and interposed between the first and second ends of the blood withdrawal line 6. In more detail, the auxiliary air separator is interposed between the blood pump 21 and the blood withdrawal safety clamp 20b.

[0209] The device of the above-described embodiments can also comprise a user interface 22 (e.g. a graphical user interface or GUI) and a control unit 12 connected to the user interface, i.e. a programmed / programmable control unit. For example, the control unit 12 can comprise one or more digital microprocessor units or one or more analog units or other combinations of analog and digital units. By way of example of a microprocessor unit, once this unit has executed a specific program (e.g. a program from an external source or directly integrated on the microprocessor card), the unit is programmed, defining a plurality of functional blocks which make up the device designed to perform the respective operations as better described in the following description.

[0210] In combination with one or more of the above-described features, the medical device can also comprise a shut-off device, for example operating in the blood circuit 17 and / or in the dialysis fluid circuit 32, and commandable between a first operating condition, in which the shut-off device allows the passage of the liquid towards the filter unit 2, and a second operating position, in which the shut-off device blocks the passage of the liquid towards the filter unit 2. In this case, the control unit 12 can be connected to the shut-off device and programmed to drive the shut-off device from the first operating condition to the second operating condition in the event of detection of an alarm condition. The shut-off device can comprise a bypass line 23 connecting the dialysis fluid supply line 8 and the dialysate effluent line 13 by-passing the dialyzer and one or more fluid non-return members 24 connected to the control unit 12 for selectively opening and closing the bypass line 23. The assembly (bypass line 23 and fluid non-return members 24) is in the first operating condition of the shut-off device when the bypass line 23 is open and the fluid non-return members 24 are closed, and in the second operating condition of the shut-off device when the bypass line 23 is closed and the fluid non-return members 24 are open. Figure 1indicated by dashed lines, which can be alternative or additional to the presence of the safety clamp 20. The non-return member 24, at the command of the control unit, closes the fluid passage towards the treatment zone and connects the source 14 directly with the dialysis effluent line 13 through the bypass line 23. Also for the control of the fluid passage towards the filtration unit 2, a dialysis fluid pump 25 and a dialysate pump 26 can be included, located on the dialysis fluid supply line 8 and on the dialysate effluent line 13, respectively, and also operatively connected to the control unit 12.

[0211] The apparatus also comprises a dialysis fluid preparation device 9, which can be of any known type, for example comprising one or more concentrate sources 27, 28 and respective concentrate pumps 29, 30 for the delivery, and at least a conductivity sensor 35. Of course, other kinds of dialysis fluid preparation device 9 can be used equivalently, with a single or another concentrate source and / or a single or multiple pumps. Since the dialysis apparatus can comprise various liquid sources 14 (for example, one or more water sources, one or more concentrate sources 27, 28, one or more disinfectant sources 33) connected to the dialysis fluid supply line 8 through respective delivery lines 36, 37 and 38, the apparatus can present respective non-return members (not all shown) at each delivery line and, for example, comprise valve members 31 and 34 and / or occlusion pumps.

[0212] The preparation device 9 can be any known system configured to prepare dialysis fluid on-line from water and a concentrate. The dialysis fluid supply line 8 fluidically connects the preparation device 9 for preparing dialysis fluid to the filtration unit 2 and / or to the blood circuit 17. As shown, the dialysis fluid supply line 8 connects the preparation device 9 for preparing dialysis fluid to the filtration unit 2 and comprises a main line 40, the upstream end of which is intended to be connected to a source of tap water 14. Connected to this main line 40 are delivery lines 36 / 37, the free ends of which are intended to be in fluid communication (e.g. immersed) with containers 27, 28 of concentrated salt solutions, each containing sodium chloride and / or calcium chloride and / or magnesium chloride and / or potassium chloride. Concentrate pumps 29, 30 are arranged in the delivery lines 36 / 37 so as to allow metered mixing of water and concentrated solutions in the main line 40. The concentrate pumps 29, 30 are driven on the basis of a comparison between: 1) a target conductivity value of the liquid mixture formed at the junction of the main line 40 with the delivery lines 36 / 37, and 2) a conductivity value of this mixture measured by a conductivity sensor 35 arranged on the main line 40 immediately downstream of the junction between the main line 40 and the delivery lines 36 / 37. Thus, as mentioned above, the dialysis fluid can contain, for example, sodium ions, calcium ions, magnesium ions and potassium ions, and the preparation device 9 can be configured to prepare the dialysis fluid on the basis of a comparison between a target conductivity value and an actual conductivity value of the dialysis fluid measured by the conductivity sensor 35 of the device 9. The preparation device 9 comprises a regulation means 10 of known type (i.e. the concentrate pumps 29, 30) configured to regulate the concentration of specific substances in the dialysis liquid, in particular ionic substances. In general, it is common to control the sodium concentration of the dialysis fluid. The dialysis fluid supply line 8 forms an extension of the main line 40 of the preparation device 9 for preparing dialysis fluid. Arranged in this dialysis fluid supply line, in the direction of circulation of the liquid, there are a first flowmeter 41 and a dialysis fluid pump 25. The supply line 8 branches, at a branching point 46, into an infusion line 39, which in the example shown is shown as being connected directly to the blood return line 7, in particular to the air separator 19 via a post-infusion tube 47b (solid line). Figure 1 The infusion line 39 is connected to the blood return line 7, in particular to the air separator 19, via a post-infusion tube 47b (solid line).

[0213] Alternatively, the infusion line 39 can infuse infusion fluid in the blood withdrawal line 6 via a pre-infusion branch 47a, in particular downstream of the blood pump 21 at the pre-infusion point 48 (dashed line). According to embodiments, the infusion line 39 can be connected to the blood return line 7 at the air separator 19a. Alternatively or in combination, the infusion line 39 can also be connected to the blood withdrawal line 6 downstream of the blood pump 21 (as shown) or at the auxiliary air separator 19b. Embodiments of the infusion line 39 comprising a pre-infusion branch 47a and a post-infusion branch 47b branching off to direct infusion fluid in the blood withdrawal line 6 and the blood return line 7, respectively, are also within the scope of the present specification. One or more infusion pumps 43 can be used to pump a desired infusion fluid flow into the blood circuit. The infusion pump 43 can be a positive displacement pump (e.g. a peristaltic pump as shown) or any other pump suitable for expelling infusion fluid (e.g. a volumetric pump). The dialysis effluent line 13 can be provided with a dialysate pump 26 and a second flow meter 42. The first flow meter 41 and the second flow meter 42 can be used to control (in a known manner) the fluid balance of the patient connected to the blood circuit 17 during a dialysis session.

[0214] The sensor 11 is provided on the dialysis effluent line 13 immediately downstream of the filtration unit 2 to measure a parameter value of the dialysate in the dialysis effluent line. In detail, the parameter of the dialysate measured by the sensor 11 is at least one selected from the group consisting of: the conductivity of the dialysate, a conductivity-related parameter of the dialysate, at least a concentration of a substance in the dialysate and at least a concentration-related parameter of a substance in the dialysate. In detail, the sensor 11 is a conductivity sensor connected to the dialysis effluent line 13 and configured to detect a conductivity value of the dialysate downstream of the filtration unit 2. Alternatively (or in combination), the sensor 11 can comprise a concentration sensor configured to measure a concentration of at least one substance in the dialysate, e.g. a sodium concentration. Correspondingly, the sensor 35 on the dialysis fluid supply line can differently comprise a concentration sensor configured to measure a concentration of at least one substance in the dialysis fluid, e.g. a sodium concentration. Figure 1 The control unit 12 of the dialysis apparatus shown in Fig. 1 can be connected to a (graphical) user interface 22 through which instructions can be received, e.g. such as a blood flow rate Q b , a dialysis fluid flow rate Q di , an infusion liquid flow rate Q infThe control unit 12 may also receive values ​​detected by the device's sensors (e.g., the aforementioned flow meters 41 and 42, the (e.g., conductivity) sensor 35 of the preparation device 9, and the (e.g., conductivity) sensor 11 in the dialysis effluent line 13). Based on the received instructions and the programmed operating modes and algorithms, the control unit 12 drives the device's actuators, such as the blood pump 21, the aforementioned dialysis fluid pump 25 and dialysate pump 26, the preparation device 9, and the infusion pump 43.

[0215] The device may further comprise one or more gas inlets 49, which are arranged on the blood return line 7 and / or the blood withdrawal line 6 and are configured to allow gas, in particular air, to enter the blood circuit 17. The gas inlet comprises a shut-off element 59, i.e. defined by a valve or a clamp, which is movable between an open position and a closed position to allow or prevent the passage of gas or fluid, respectively. The shut-off element 59 is further connected to the control unit 12, which is configured to selectively command the shut-off element 59 to be in the open position or in the closed position. In an embodiment, the device 1 may comprise one gas inlet 49, i.e. a first gas inlet 49a, such as Figures 6 to 8The first gas inlet 49a is associated with a respective first shut-off element 59a movable between an open position and a closed position to control gas transmission. In another embodiment, the device 1 can comprise a first gas inlet 49a on the blood return line 7 and a second gas inlet 49b arranged on the blood withdrawal line 6 interposed between the blood pump 21 and the blood withdrawal safety clamp 20b. The second gas inlet 49b is also associated with a respective second shut-off element 59b movable between an open position and a closed position to control gas or fluid transmission. The device 1 can also comprise a gas supply unit 60 fluidically connected to one or more gas inlets 49 and configured to forcibly infuse gas (i.e. air) into the blood circuit 17 through the gas inlets 49 (i.e. through the first gas inlet 49a or the second gas inlet 49b). The gas supply unit 60 can be a compressor or a pump configured to provide pressurized gas into the blood circuit 17 through the respective gas inlets. The control unit 12 is configured to control activation, stop or regulation of the gas supply unit 60. In the embodiment shown in the attached figures, the gas inlets 49 can be arranged at the air separator 19. In more detail, the first gas inlet 49a can be arranged at the air separator 19a of the blood return line 7, while the second gas inlet 49b can be arranged at the auxiliary air separator 19b of the blood withdrawal line 6. Moreover, the respective shut-off elements 59a, 59b can also be arranged at the air separator 19. Figure 1The device shown in the figures illustrates a particular embodiment in which the infusion line 39, the first gas inlet 49a and the first shut-off element 59a are all arranged at the air separator 19a of the return line 7. Similarly, the second gas inlet 49b and the second shut-off element 59b are arranged at the auxiliary air separator 19b of the withdrawal line 6, without excluding that the infusion line 39 can be connected to the auxiliary air separator 19b of the withdrawal line 6. The device can also comprise a gas inlet arranged on the fluid circuit 32 and configured to allow the entry of gas into the fluid circuit 32. The gas inlet can be arranged on the dialysis fluid supply line 8 and / or on the effluent line 13. The fluid circuit further comprises a shut-off element connected to the gas inlet of the fluid circuit 32, wherein the shut-off element (not shown in the figures) is movable between an open position and a closed position to allow or prevent, respectively, the entry of gas into the fluid circuit 32. The shut-off element of the fluid circuit 32 can be connected to the control unit 12, which is configured to command the shut-off element to be in the open position or in the closed position. The fluid circuit 32 can also comprise a gas supply unit (not shown in the figures) fluidically connected to the gas inlet of the fluid circuit 32 and configured to infuse gas into the fluid circuit 32. The device can also comprise a gas sensor, in particular associated with the filtration unit 2, configured to provide a signal indicative of the presence of gas and / or of the amount of gas included in the secondary chamber 4 of the filtration unit 2. The gas sensor can be, for example, a weight sensor or a level sensor of the dialysis fluid present in the secondary chamber 4 of the filtration unit 2.

[0216] As already mentioned, the described embodiments are intended as non-limiting examples. In particular, Figure 1 The circuit described should not be interpreted as limiting or restrictive, as a device such as that in the present application can comprise other additional or alternative components to those described. For example, an ultrafiltration line can be included, in which at least one respective pump is connected to the dialysis effluent line 13. Figure 1The blood circuit is intended for double-needle treatment; however, this is a non-limiting example of a blood set. In fact, the device can be configured to perform single-needle treatment, i.e. the patient is connected to the extracorporeal blood circuit by means of a single needle, then the extracorporeal line coming from the patient is divided into a withdrawal line and a return line using, for example, a “Y” connector. During single-needle treatment, the blood withdrawal phase, in which blood is removed from the patient, alternates with the blood return phase, in which blood is returned to the patient. Moreover, one or more devices for measuring the concentration of a specific substance can be implemented in either (or both) the dialysis fluid side or the blood side of the hydraulic circuit. It can be desirable to know the concentration of calcium, potassium, magnesium, bicarbonate and / or sodium. Finally, one or more pumps and all the other necessary temperature, pressure and concentration sensors described above can operate on the dialysis fluid supply line 8 and / or on the dialysis effluent line 13 in order to monitor adequately the preparation and movement of the liquids in the hydraulic circuit. In view of the above description of possible embodiments of the extracorporeal blood treatment device, the specific functioning of the device and the algorithm for programming the control unit are subsequently described.

[0217] Blood return (and emptying) procedure

[0218] The device 1, in particular the blood circuit 17, is filled with blood during extracorporeal blood treatment, which is withdrawn from the patient through the blood withdrawal line 6, treated in the filter unit 2 and then returned to the patient through the blood return line 7: therefore, at the end of extracorporeal blood treatment, the blood circuit 17 is still filled with a significant amount of residual blood of the patient. The device 1 described above is configured to perform, at the end of extracorporeal blood treatment and before disconnection from the patient, a blood return procedure consisting of returning the residual blood present in the blood circuit 17 to the patient. Therefore, the patient needs to be connected to the device by means of at least one blood line. The steps of the blood return procedure are described hereafter according to different embodiments. These steps define the method of blood return or are considered to be performed by the control unit 12 of the device. Figures 2 to 8 A portion of the entire hydraulic circuit 100 is shown in order to magnify a portion of the blood circuit 17 and of the fluid circuit 32. These figures show different steps in which the transfer of sterile fluid, gas and blood within the lines takes place according to the blood return procedure. Therefore, different patterns are drawn on the figures in order to distinguish blood, fluid and gas. A legend is shown in the figures associating each pattern to blood, sterile fluid and gas. The patterns are consistent in all figures. The blood return procedure comprises the step of infusing a predetermined amount of sterile fluid from the supply source 50 into the blood circuit 17, as shown in Figure 2 、 Figure 2A and Figure 7 wherein the sterile fluid can be a substitution fluid, a dialysis fluid or a saline.

[0219] According to Figure 2In the embodiment shown in Fig. 1, the sterile fluid infusion step implies infusing sterile fluid through infusion line 39 into blood return line 7, or according to an alternative embodiment not shown, into blood withdrawal line 6 of blood circuit 17. While the drawings show infusion line 39 always connected to blood return line 7, it is also possible to implement an arrangement in which infusion line 39 is connected to blood withdrawal line 6 or even to both blood lines. The infusion step comprises activating infusion pump 43 operating on infusion line 39 to determine a fluid flow towards blood circuit 17. In case infusion line is connected to fluid circuit 32, dialysis fluid pump 25 can also be activated to provide fluid to infusion line 39, otherwise infusion line 39 can receive sterile fluid from a container or bag connected to the end of infusion line 39 and containing sterile fluid. In this last scenario, infusion pump 43 can be absent, the flow rate of sterile fluid infused can be determined by gravity and controlled by a clamp or a valve.

[0220] According to Figure 2A In the embodiment shown in Fig. 1, the sterile fluid infusion step implies infusing sterile fluid through infusion line 39 into blood return line 7, or according to an alternative embodiment not shown, into blood withdrawal line 6 of blood circuit 17. While the drawings show infusion line 39 always connected to blood return line 7, it is also possible to implement an arrangement in which infusion line 39 is connected to blood withdrawal line 6 or even to both blood lines. The infusion step comprises activating infusion pump 43 operating on infusion line 39 to determine a fluid flow towards blood circuit 17. In case infusion line is connected to fluid circuit 32, dialysis fluid pump 25 can also be activated to provide fluid to infusion line 39, otherwise infusion line 39 can receive sterile fluid from a container or bag connected to the end of infusion line 39 and containing sterile fluid. In this last scenario, infusion pump 43 can be absent, the flow rate of sterile fluid infused can be determined by gravity and controlled by a clamp or a valve.

[0221] In case of dialysis backfiltration, the amount of sterile fluid infused into blood circuit 17 can be determined by controlling dialysis fluid pump 25 and optionally also dialysis liquid pump 26. Otherwise, if sterile fluid is infused from infusion line 39, the amount of sterile fluid infused into blood circuit 17 can be determined by controlling infusion pump 43. In case infusion line is connected to a container or bag and infusion pump is absent, the amount of sterile fluid infused into blood circuit 17 can be determined by monitoring the weight of the container or bag, which changes over time as sterile fluid is infused.

[0222] In both cases, in which the sterile fluid is infused by back filtration or by an infusion line directly in the return line or the extraction line, the sterile fluid infusion step means that the sterile fluid needs to reach the position of the gas inlet 49. More specifically, the amount of sterile fluid infused must be sufficient to reach and exceed the position of the gas inlet 49 to allow subsequent gas infusion. The term "exceed" means that if the sterile fluid enters the blood circuit 17 by back filtration of the membrane 5 of the filtration unit 2, the sterile fluid must be transported through the extraction line 6 or the return line 7 in the direction of the gas inlet 49, reach said gas inlet 49, and pass through the position of the gas inlet 49 so that the position of the gas inlet 49 is between the parts of the sterile fluid, such as Figure 2 、 Figure 2A and Figure 7 The predetermined amount of sterile fluid is typically comprised between 50 ml and 200 ml.

[0223] The infusion step of the sterile fluid into the blood circuit 17 defines at least one fluid-blood interface FBI, where the residual blood and the infused sterile fluid face each other. At this interface, the blood and the sterile fluid may slightly merge with each other. In any case, the interface between the blood and the fluid is defined, so it does not matter if the interface is not completely clear. According to the embodiment shown in the accompanying drawings, the sterile fluid infusion step defines a first fluid-blood interface FBI' and a second fluid-blood interface FBI", wherein the first fluid-blood interface FBI' is between the infused sterile fluid and the second end of the blood return pipeline 7, and the second fluid-blood interface FBI" is between the same infused sterile fluid and the second end of the blood withdrawal pipeline 6.

[0224] During the infusion step, the sterile fluid may push some of the residual blood back to the patient or into the buffer container, so that the fluid-blood interface FBI moves at least upward in the blood line and exceeds the gas inlet 49. In particular, if the device comprises more than one gas inlet 49, the infusion step means that at least one of the first FBI′ and the second FBI″ reaches and exceeds at least one gas inlet 49. For example, Figure 2 and Figure 2A As shown, although the device is provided with the first gas inlet 49a and the second gas inlet 49b, only the first fluid-blood interface FBI' has reached and exceeded the first gas inlet 49a.

[0225] During the aseptic fluid infusion, the shut-off element 59 of the gas inlet 49 is commanded in the closed position, so as not to allow the gas to enter the blood circuit and not to allow the fluid to exit from the blood circuit. Moreover, according to the embodiment, at least one between the blood return safety clamp 20a and the blood withdrawal safety clamp 20b is arranged in the open position to allow a partial blood restitution during the aseptic fluid infusion step. If the infusion line 39 is responsible for infusing the aseptic fluid into the blood circuit 17, the dialysis fluid pump 25 and the dialysate pump 26 are controlled to prevent the blood or the fluid from flowing from the primary chamber 3 to the secondary chamber 4 of the filter unit 2.

[0226] According to Figure 10 and Figure 11 , the restitution procedure comprises a step of allowing a predetermined amount of gas to enter the secondary chamber 4 of the filter unit 2 before or simultaneously with the step of infusing the aseptic fluid into the blood circuit 17, as shown in Figure 10 . The predetermined amount of gas is defined on the basis of the internal volume of the secondary chamber 4 of the filter unit 2 to partially fill the secondary chamber 4 of the filter unit 2 with gas. In particular, the restitution procedure means filling at least 75% of the internal volume of the secondary chamber 4 with gas, more in detail, at least 90% of the internal volume of the secondary chamber 4 with gas. Once the secondary chamber 4 of the filter unit 2 is filled with the predetermined amount of gas, the aforementioned step of back-filtering the membrane 5 with dialysis fluid means that the fluid is forced to flow from the secondary chamber 4 to the primary chamber 3 through a reduced surface of the membrane 5 only, thus defining the point of infusion of the aseptic fluid into the blood circuit 17. This allows to significantly reduce the dilution of the blood with the aseptic fluid during the step of infusing / back-filtering the aseptic fluid into the blood circuit 17. In fact, if the aseptic fluid is infused by back-filtering the entire surface of the membrane 5, the blood contained in the primary chamber 3 would be diluted with the aseptic fluid, thus reducing the sharpness of the fluid-blood interface FBI. On the other hand, if the aseptic fluid is back-filtered through a reduced surface of the membrane 5, the amount of blood diluted with the aseptic fluid would be significantly reduced, thus increasing the sharpness of the fluid-blood interface FBI in the blood circuit.

[0227] In other words, the restitution procedure can mean that the secondary chamber 4 is filled with both gas and aseptic fluid (in particular dialysis fluid), wherein the amount of gas inside the secondary chamber 4 is higher in volume than the amount of aseptic fluid. In particular, during the restitution procedure, 75% of the volume of the secondary chamber 4 is filled with gas, more in particular 90%, while the remaining volume of the secondary chamber 4 is filled with aseptic fluid.

[0228] Figure 10 and Figure 11 , the device shown in Figures 1 to 9 is inverted. In particular, as shown in Figure 10 and Figure 11The arrangement of the device shown in the middle represents an embodiment in which the inlet of the secondary chamber 4 connected to the dialysis supply line 8 is located at a lower level with respect to the outlet of the secondary chamber 4 connected to the dialysis effluent line 13. In more detail, according to the embodiment of the device shown in the middle Figure 10 and Figure 11 The gravitational acceleration of the device is from top to bottom. In other words, the filtration unit 2 is positioned so that the gas occupies the volume above the sterile fluid when it is infused into the secondary chamber 4, since the density between the gas and the sterile fluid is different, in particular where the gas has a lower density than the density of the sterile fluid, so that the gas is interposed between the sterile fluid and the outlet of the secondary chamber 4 of the filtration unit 2. The gas-fluid interface inside the secondary chamber 4 of the filtration unit is marked as GFI F as shown in Figure 10 , Figure 11 .

[0229] The step of allowing the gas to enter the secondary chamber 4 of the filtration unit 2 can mean activating at least one of the dialysis fluid pump 25 and the dialysis liquid pump 26, in which the gas is allowed to enter the fluid circuit 32 through a gas inlet arranged on the fluid circuit 32. This step can mean infusing the gas inside the fluid circuit at a pressure higher than the pressure present inside the fluid circuit by means of a gas supply unit, i.e. a gas compressor, connected to said gas inlet, otherwise it can mean starting at least one of the dialysis fluid pump 25 and the dialysis liquid pump 26 to suck the gas from the gas inlet arranged on the fluid circuit 32.

[0230] Figure 10 The sterile infusion step according to the embodiment in which the secondary chamber is filled with gas is shown. The sterile fluid is back-filtered through the membrane 5 to enter the blood circuit 17. In particular, Figure 10 The embodiment in which the extraction clamp 20a or the occlusion of the blood pump 21 prevents the blood / fluid flow through the extraction line 6 is shown, so that the back-filtered sterile fluid is forced to flow towards the blood return line 7, reaching and exceeding the gas inlet 49. The sterile fluid infusion step in which the secondary chamber 4 is partially filled with gas in the restitution procedure can mean a complete blood restitution according to the embodiment of Figure 11 : the sterile fluid is back-filtered through a reduced surface of the membrane 5 of the filtration unit 2, so that the sterile fluid enters the blood circuit 17 defining a first fluid-blood interface FBI' and a second fluid-blood interface FBI", and in which the infusion step also determines the movement of the blood through the blood extraction line 6 and / or the blood return line 7 towards the patient. In particular, the restitution procedure can mean a simultaneous blood restitution through both the return line and the extraction line or a sequential blood restitution through the extraction line 6 and the return line 7, i.e. in which the blood is first returned to the patient through the extraction blood line 6 and then through the return blood line 7, or vice versa.

[0231] The blood restitution procedure further comprises the step of allowing a predetermined amount of gas to enter the blood circuit 17 from the gas inlet 49 to define at least one gas-fluid interface GFI within the blood circuit 17 . Figures 3 to 6 and Figure 8 The introduction of gas into the blood circuit according to different embodiments and at different times of the blood return procedure is shown. In more detail, the introduction of gas into the blood circuit 17 defines a first gas-fluid interface GFI' between the introduced gas and the second end of the blood return line 7 and a second gas-fluid interface GFI", between the introduced gas and the second end of the blood withdrawal line 6. As the gas enters the blood circuit, the gas introduction determines the return of blood to the patient via the blood return line 7 and / or the blood withdrawal line 6. It should be noted that the partial blood return caused by the infusion of the sterile fluid is generally lower in volume, in particular, much lower in volume, than the blood return determined by the gas introduction.

[0232] The gas introduction step also determines that the sterile fluid infused into the blood circuit 17 is divided into a first sterile fluid portion and a second sterile fluid portion, wherein the first sterile fluid portion is between the first fluid-blood interface FBI' and the first gas-fluid interface GFI', and the second sterile fluid portion is between the second fluid-blood interface FBI" and the second gas-fluid interface GFI".

[0233] The return procedure involves infusing sterile fluid into the blood circuit 17 and introducing gas into the blood circuit 17 so that the distance between the fluid-blood interface FBI and the gas-fluid interface GFI is between 0.5 cm and 10 cm, or between 1 cm and 5 cm. This distance is measured along the corresponding blood line. The amount of fluid that determines this distance between FBI and GFI depends on the geometric characteristics of the blood line. Therefore, the amount of fluid to be infused must be calculated by the control unit 12 based on the geometric characteristics of the blood line.

[0234] The return procedure means that, during the gas introduction step, the shut-off element 59 of the gas inlet 49 to which the sterile fluid to be infused has arrived is in the open position, thereby allowing the gas to enter the blood circuit. Figure 3 and Figure 4In the illustrated embodiment, the gas introduction step is determined by activating the blood pump 21 towards the second end of the blood withdrawal line 6, so that, in the case where the first shut-off element 59a is commanded in the open position, gas is sucked from the first gas inlet 49a into the blood circuit 17. As the blood pump 21 determines a fluid flow towards the patient, a partial blood restitution is performed, in particular in which the residual blood of the withdrawal line 6 is returned to the patient. At the same time, the second fluid-blood interface FBI" and the second gas-fluid interface GFI" move towards the second end of the withdrawal line 6, thus pushing the residual blood into the patient's vascular system, while the first fluid-blood interface FBI' and the first gas-fluid interface GFI' substantially maintain their position within the blood circuit 17. During this gas introduction step, the blood return safety clamp 20a is commanded in the closed position, while the blood withdrawal safety clamp 20b is commanded in the open position. Figure 3 The beginning phase of the introduction of gas from the first gas inlet 49a is illustrated, in which the GFI" travels within the blood withdrawal line 6 towards the blood pump 21 and beyond the blood pump 21 until the residual blood in the withdrawal line 6 is substantially, in particular completely, returned to the patient, as illustrated in Figure 4 .

[0235] Subsequently, according to the same embodiment illustrated in Figure 3 and Figure 4 , the gas introduction step implies closing the first shut-off element 59a of the first gas inlet 49a, closing the blood withdrawal safety clamp 20b, opening the second shut-off element 59b of the second gas inlet 49b, opening the blood return safety clamp 20a, and activating the blood pump 21 in the direction towards the second end of the blood return line 7, so that gas is sucked from the second gas inlet 49b and the first fluid-blood interface FBI' and the first gas-fluid interface GFI' move towards the second end of the blood return line 7, as illustrated in Figure 5 . The movement of the first fluid-blood interface FBI' and the first gas-fluid interface GFI' allows the residual blood in the return line 7 to be returned to the patient through the blood return line 7. In other words, the blood restitution procedure implies, before being disconnected from the patient P, simultaneously moving towards the patient P at least part of the extracorporeal blood remaining in the blood circuit 17, at least part of the sterile fluid interposed between the first fluid-blood interface FBI and the first gas-fluid interface GFI, and at least part of the gas. In other words, the movement of the fluid-blood interface FBI and the gas-fluid interface GFI towards the patient allows blood restitution and emptying of the blood lines 6, 7.

[0236] According to the same embodiment illustrated in Figure 6In another embodiment illustrated in the middle, the device comprises a gas supply unit 60 fluidly connected to a gas inlet 49 of the blood circuit. The gas introduction step comprises activating the gas supply unit 60 to infuse pressurized gas into the blood circuit. By commanding the safety clamp 20a or 20b, or the blood pump 21 (in case the blood pump 21 is an occlusive blood pump), the gas is allowed to travel within the blood circuit towards the second end of the blood return line 7 or towards the second end of the blood withdrawal line 6. For example, the blood return procedure can mean closing the blood withdrawal safety clamp 20b so that the first fluid-blood interface FBI' and the first gas-fluid interface GFI' move towards the second end of the blood return line 7. Otherwise, alternatively, the blood return procedure can mean closing the blood return safety clamp 20a so that the second fluid-blood interface FBI" and the second gas-fluid interface GFI" move towards the second end of the blood withdrawal line 6. Moreover, the blood return procedure can also mean opening both the blood return safety clamp 20a and the blood withdrawal safety clamp 20b so that the first fluid-blood interface FBI' and the first gas-fluid interface GFI' move towards the second end of the blood return line 7 and, simultaneously, the second fluid-blood interface FBI" and the second gas-fluid interface GFI" move towards the second end of the blood withdrawal line 6. In other words, the blood return can occur simultaneously through both the blood return line and the blood withdrawal line, or selectively through one of the blood return line and the blood withdrawal line. According to Figure 6 In another embodiment illustrated in the middle, the device comprises a gas supply unit 60 fluidly connected to a gas inlet 49 of the blood circuit. The gas introduction step comprises activating the gas supply unit 60 to infuse pressurized gas into the blood circuit. By commanding the safety clamp 20a or 20b, or the blood pump 21 (in case the blood pump 21 is an occlusive blood pump), the gas is allowed to travel within the blood circuit towards the second end of the blood return line 7 or towards the second end of the blood withdrawal line 6. For example, the blood return procedure can mean closing the blood withdrawal safety clamp 20b so that the first fluid-blood interface FBI' and the first gas-fluid interface GFI' move towards the second end of the blood return line 7. Otherwise, alternatively, the blood return procedure can mean closing the blood return safety clamp 20a so that the second fluid-blood interface FBI" and the second gas-fluid interface GFI" move towards the second end of the blood withdrawal line 6. Moreover, the blood return procedure can also mean opening both the blood return safety clamp 20a and the blood withdrawal safety clamp 20b so that the first fluid-blood interface FBI' and the first gas-fluid interface GFI' move towards the second end of the blood return line 7 and, simultaneously, the second fluid-blood interface FBI" and the second gas-fluid interface GFI" move towards the second end of the blood withdrawal line 6. In other words, the blood return can occur simultaneously through both the blood return line and the blood withdrawal line, or selectively through one of the blood return line and the blood withdrawal line. According to

[0237] According to any one of the preceding embodiments, the blood return procedure ends when the sterile fluid, in particular the first and second portions of sterile fluid, reaches the vascular access 18 of the patient. A small amount of sterile fluid can also be infused into the patient in order to complete the blood return and improve the cleaning and emptying of the blood lines. According to embodiments, the return procedure is stopped when the fluid-blood interface FBI approaches at least one of the second end of the blood withdrawal line 6 and the second end of the blood return line 7, or when a preset amount of sterile fluid has been infused into the patient. In particular, the return procedure can be stopped when the gas-fluid interface GFI reaches a preset distance from the second end of the blood withdrawal line 6 and / or the second end of the blood return line 7. The preset distance measured along the respective blood line can be set to be lower than 10 cm or 5 cm.

[0238] The blood circuit 17 can also comprise a gas sensor arranged close to the second end of the blood withdrawal line 6 and / or the second end of the blood return line 7. The gas sensor is configured to provide a signal representative of the presence of gas in the respective blood line, so that the control unit 12 is configured to, or the method comprises, receiving the signal and stopping the advancement of the gas fluid interface GFI. In particular, the control unit is configured to stop the blood pump 21 or the gas supply unit 60, to move the blood withdrawal shut-off element 20b to the closed position if the gas sensor of the blood withdrawal line 6 detects the presence of gas, and / or to move the blood return shut-off device 20a to the closed position if the gas sensor of the blood return line 7 detects the presence of gas.

[0239] According to another embodiment, the blood restitution procedure ends when a predetermined amount of gas has been introduced within the blood circuit. This predetermined amount can be calculated as a function of the internal volume of the blood circuit 17, so that the volume of the amount of gas is less than said internal volume of the blood circuit 17.

[0240] Figure 7 and Figure 8 An embodiment of the device is shown, wherein a single gas inlet 49 is provided on the blood return line 7. In particular, this gas inlet 49 can be arranged as close as possible to the vascular access 18 of the patient. According to this embodiment, the blood restitution procedure comprises the previously described step of infusing a predetermined amount of sterile fluid into the blood circuit 17 through the infusion line 39 up to and beyond the gas inlet 49. A reverse filtration infusion can also be performed to infuse a predetermined amount of sterile fluid into the blood circuit 17 up to and beyond the gas inlet 49. Figure 7 A stage is shown in which the sterile fluid infusion step has caused a partial blood restitution to the patient through the blood return line 7. Indeed, the blood previously retained in the blood return line 7 between the gas inlet 49 and the vascular access has been replaced by the sterile fluid, while residual blood still exists in the rest of the blood return line 7 up to the filtration unit 2 and within the entire blood withdrawal line 6. According to a non-limiting configuration, the blood return safety clamp 20a and the blood withdrawal safety clamp 20b are simultaneously or sequentially moved to the open position during the fluid infusion step, thereby allowing the sterile fluid to pass beyond the gas inlet 49 and into the upstream and downstream portions of the blood return line. If the blood pump 21 is an occlusion pump, the infusion step implies activating the blood pump 21 towards the second end of the withdrawal line 6, to allow the sterile fluid to flow into the upstream portion of the blood return line 7 with respect to the gas inlet 49.

[0241] The blood restitution procedure also comprises (see Figure 8) the step of commanding the opening of the shut-off element 59 of the gas inlet 49, the closing of the blood return safety clamp 20a, the opening of the blood withdrawal safety clamp 20b and the activation of the blood pump 21 towards the second end of the withdrawal line 6, so that gas is sucked from the gas inlet 49 of the blood return line 7, as shown in Figure 8 During this step, the second fluid-blood interface FBI" and the second gas-fluid interface GFI" move towards the second end of the withdrawal line 6, thus pushing the residual blood back to the patient through the withdrawal line 6.

[0242] According to an embodiment of the return procedure, the volume of the predetermined amount of sterile fluid infused into the blood circuit 17 is less than the predetermined amount of gas introduced. In fact, the amount of sterile fluid infused must be just enough to define the fluid-blood interface FBI and the gas-fluid interface GFI, so as to prevent the gas-blood interface, since otherwise it would cause local blood clotting. In more detail, the predetermined amount of sterile fluid infused can be comprised between 5% and 80%, in particular between 10% and 60%, of the volume of the predetermined amount of gas. Moreover, the predetermined amount of volume of sterile fluid can be comprised between 1% and 60%, in more detail between 2% and 40% or between 5% and 30%, of the internal volume of the blood circuit. In any case, the predetermined amount of gas introduced into the blood circuit 17 is generally comprised between 50 ml and 150 ml, said values being measured at 25° and at atmospheric pressure. The total infused fluid volume is defined by the sum of the predetermined amount of sterile fluid and the predetermined amount of gas introduced into the blood circuit 17. This total infused fluid volume is comprised between 60% and 160% of the internal volume of the blood circuit.

[0243] Different configurations of the blood return procedure are provided hereafter. Each configuration has been described in detail in order to provide the clearest possible representation of the procedure. Therefore, the return procedure provided hereafter is intended as a non-limiting representation of the scope of the present application, while at the same time as an exemplary representation of the blood return procedure.

[0244] According to the first configuration shown in Figure 2 , Figure 2A , Figure 3 , Figure 4 and Figure 5 , the return procedure means that the following steps are performed sequentially:

[0245] - commanding at least one between the blood return safety clamp 20a and the blood withdrawal safety clamp 20b in the open position, or commanding the blood return safety clamp 20a in the open position and the blood withdrawal safety clamp 20b in the closed position, or commanding the blood return safety clamp 20a in the closed position and the blood withdrawal safety clamp 20b in the open position;

[0246] - commanding the infusion of a predetermined amount of sterile fluid into the blood circuit 17 by:

[0247] o activating the dialysis fluid pump 25 and optionally stopping the dialysate pump 26 or activating the dialysate pump 26 at a lower speed to determine the back filtration of dialysis fluid through the semipermeable membrane 5 Figure 2 ); and / or

[0248] o activating the infusion pump 43 to determine the infusion of fluid through the infusion line 39 Figure 2A ,

[0249] wherein the step determines the position of the sterile fluid beyond the first gas inlet 49a and wherein the step defines a first fluid-blood interface FBI' and a second fluid-blood interface FBI";

[0250] - commanding the first shut-off element 59a of the first gas inlet 49a on the blood return line 7 to be in an open position, the second shut-off element 59b of the second gas inlet 49b on the blood withdrawal line 6 to be in a closed position, the blood return safety clamp 20a to be in a closed position and the blood withdrawal safety clamp 20b to be in an open position;

[0251] - commanding the activation of the blood pump 21 in a direction towards the second end of the blood withdrawal line 6 to draw a predetermined amount of gas from the first gas inlet 49a into the blood circuit 17 Figure 3 and Figure 4 , the step defining a first gas-fluid interface GFI' and a second gas-fluid interface GFI" and determining the movement of the second gas-fluid interface GFI" and of the second fluid-blood interface FBI" towards the second end of the blood withdrawal line 6, thereby performing a partial blood restitution to the patient P through the blood withdrawal line 6;

[0252] - commanding the blood withdrawal safety clamp 20b to be in a closed position, the blood return safety clamp 20a to be in an open position, the first shut-off element 59a of the first gas inlet 49a on the blood return line 7 to be in a closed position and the second shut-off element 59b of the second gas inlet 49b on the blood withdrawal line 6 to be in an open position;

[0253] - commanding the activation of the blood pump 21 in a direction towards the second end of the blood return line 7, the step determining the movement of the first gas-fluid interface GFI' and of the first fluid-blood interface FBI' towards the second end of the blood return line 7, thereby causing a certain amount of blood to be returned to the patient P through the blood return line 7.

[0254] According to the second configuration shown in Figure 7 and Figure 8 , the restitution procedure implies the sequential execution of the following steps:

[0255] - commanding at least one of the blood return safety clamp 20a and the blood withdrawal safety clamp 20b to be in the open position, or commanding the blood return safety clamp 20a to be in the open position and the blood withdrawal safety clamp 20b to be in the closed position, or commanding the blood return safety clamp 20a to be in the closed position and the blood withdrawal safety clamp 20b to be in the open position;

[0256] - commanding the infusion of a predetermined amount of sterile fluid ( Figure 7 ) into the blood circuit 17 by:

[0257] o activating the dialysis fluid pump 25 and optionally stopping the dialysate pump 26 or activating the dialysate pump 26 at a lower speed to determine the back filtration of dialysis fluid ( Figure 2 ) through the semi-permeable membrane 5; and / or

[0258] o activating the infusion pump 43 to determine the infusion of fluid ( Figure 2A ) through the infusion line 39,

[0259] wherein this step determines the position of the sterile fluid beyond the first gas inlet 49a, and wherein this step defines a first fluid-blood interface FBI' and a second fluid-blood interface FBI".

[0260] - determining the partial blood restitution ( Figure 7 ) through the blood return line 7 due to the infusion of sterile fluid, the blood return safety clamp 20a being arranged in the open position;

[0261] - commanding the shut-off element 59 of the gas inlet 49 to be in the open position, the blood return safety clamp 20a to be in the closed position, the blood withdrawal safety clamp 20b to be in the open position;

[0262] - commanding the activation of the blood pump 21 in a direction towards the second end of the blood withdrawal line 6 to draw a predetermined amount of gas from the gas inlet 49 into the blood circuit 17 ( Figure 8 ), the gas inlet 49 being arranged on the blood return line 7, as close as possible to the patient, wherein this step defines a first gas-fluid interface GFI' and a second gas-fluid interface GFI", and determines the movement of the second gas-fluid interface GFI" and of the second fluid-blood interface FBI" towards the second end of the blood withdrawal line 6, thereby determining the blood restitution to the patient P through the blood withdrawal line 6.

[0263] According to a third configuration, the restitution procedure implies a device as shown in Figure 6 , comprising a gas supply unit 60 connected to one gas inlet 49, in particular to the first gas inlet 49a or to the second gas inlet 49b. The procedure implies the sequential execution of the following steps:

[0264] - commanding at least one of the blood return safety clamp 20a and the blood withdrawal safety clamp 20b to be in the open position, or commanding the blood return safety clamp 20a to be in the open position and the blood withdrawal safety clamp 20b to be in the closed position, or commanding the blood return safety clamp 20a to be in the closed position and the blood withdrawal safety clamp 20b to be in the open position;

[0265] - commanding the infusion of a predetermined amount of sterile fluid into the blood circuit 17 by:

[0266] o activating the dialysis fluid pump 25 and optionally stopping the dialysate pump 26 or activating the dialysate pump 26 at a lower speed to determine the back filtration of dialysis fluid through the semi-permeable membrane 5; and / or

[0267] o activating the infusion pump 43 to determine the infusion of fluid through the infusion line 39,

[0268] wherein the step determines the position of the sterile fluid beyond the first gas inlet 49a, and wherein the step defines a first fluid-blood interface FBI' and a second fluid-blood interface FBI".

[0269] - commanding the shut-off element 59 of the gas inlet 49 to be in the open position;

[0270] - commanding at least one of the blood return safety clamp 20a and the blood withdrawal safety clamp 20b to be in the open position;

[0271] - commanding the activation of the gas supply unit 60 to infuse gas into the blood circuit 17, the step determining:

[0272] o the second gas-fluid interface GFI" and the second fluid-blood interface FBI" moving towards the second end of the blood withdrawal line 6, thereby causing a quantity of blood to be returned to the patient P through the blood withdrawal line 6; and / or

[0273] o the first gas-fluid interface GFI' and the first fluid-blood interface FBI' moving towards the second end of the blood return line 7, thereby causing a quantity of blood to be returned to the patient P through the blood return line 7.

[0274] According to a fourth configuration, not shown in the drawings, the return procedure implies the sequential execution of the following steps:

[0275] - commanding the infusion of a predetermined amount of sterile fluid into the blood circuit (17) by back filtration of dialysis fluid through the infusion line (39) or through the semi-permeable membrane (5), said step determining the position of the sterile fluid beyond the gas inlet (49) arranged on the blood withdrawal line (6), said step defining a first fluid-blood interface and a second fluid-blood interface (FBI', FBI");

[0276] - determining the return of a portion of blood through the blood withdrawal line (6) due to the sterile fluid infusion, the blood withdrawal safety clamp (20b) being in the open position;

[0277] - commanding the shut-off element (59) of the gas inlet (49) to be in the open position, the blood withdrawal safety clamp (20b) to be in the closed position, the blood return safety clamp (20a) to be in the open position;

[0278] - commanding the activation of the blood pump (21) in the direction towards the second end of the blood return line (7) to draw a predetermined amount of gas from the gas inlet (49) into the blood circuit (17), the step determining the movement of at least one gas-fluid interface (GFI), in particular of the first gas-fluid interface (GFI’) and of the first fluid-blood interface (FBI’) towards the second end of the blood return line (7), so as to perform the blood return to the patient (P) through the blood return line (7). The blood return procedure can also comprise a push-pull procedure configured to empty an end portion of the blood return line 7 or of the second end of the blood withdrawal line 6, which can still be filled with sterile fluid or residual blood or a mixture of fluid and blood. In particular, the push-pull procedure can be performed in a device having a single gas inlet 49 at the end of the second configuration and / or of the fourth configuration of the blood return procedure. In more detail, the push-pull procedure means the periodic activation of the blood pump 21 in both directions, in particular towards the second end of the withdrawal line 6 and towards the second end of the return line 7, and the periodic opening and closing of the gas inlet 49 to promote the movement of the residual fluid contained in the blood circuit towards the patient.

[0279] In more detail, the second configuration of the blood return procedure can also comprise, at the end, a push-pull procedure comprising the following steps:

[0280] - activating the blood pump 21 towards the second end of the blood withdrawal line 6,

[0281] the blood withdrawal safety clamp 20b and the blood return safety clamp 20a being arranged in the closed position, the shut-off element 59 of the gas inlet 49 of the blood return line 7 being arranged in the open position, in particular said step determining the suction of gas from said gas inlet 49 into the blood circuit 17 and optionally the compression of the gas comprised between the blood pump 21 and the blood withdrawal safety clamp 20b;

[0282] - activating the blood pump 21 towards the second end of the blood return line 7,

[0283] - the blood withdrawal safety clamp 20b is arranged in the closed position, the blood return safety clamp 20a is arranged in the open position, the shut-off element 59 of the gas inlet 49 of the blood return line 7 is arranged in the closed position, in particular, said step determines the movement of the residual fluid through the blood return line 7 towards the patient, more specifically, said step determines the movement of the first gas-fluid interface GFI' towards the second end of the blood return line 7.

[0284] The push-pull procedure can be cyclically repeated to move the gas-fluid interface GFI' towards the second end of the return line 7, so as to fill the return line 7 with gas.

[0285] Similarly, the fourth configuration of the blood restitution procedure can also comprise, at the end, a push-pull procedure comprising the following steps:

[0286] - activating the blood pump 21 towards the second end of the blood return line 7,

[0287] - the blood withdrawal safety clamp 20b and the blood return safety clamp 20a are arranged in the closed position, the shut-off element 59 of the gas inlet 49 of the blood withdrawal line 6 is arranged in the open position, in particular, said step determines the suction of gas from said gas inlet 49 into the blood circuit 17 and optionally the compression of the gas comprised between the blood pump 21 and the blood return safety clamp 20a;

[0288] - activating the blood pump 21 towards the second end of the blood withdrawal line 6,

[0289] - the blood withdrawal safety clamp 20b is arranged in the open position, the blood return safety clamp 20a is arranged in the closed position, the shut-off element 59 of the gas inlet 49 of the blood withdrawal line 6 is arranged in the closed position, in particular, said step determines the movement of the residual fluid through the blood withdrawal line 6 towards the patient, more specifically, said step determines the movement of the second gas-fluid interface GFI" towards the second end of the blood withdrawal line 6. The push-pull procedure can be cyclically repeated to move the gas-fluid interface GFI" towards the second end of the withdrawal line 6, so as to fill the withdrawal line 6 with gas.

[0290] It is noted that the device configured to perform the restitution procedure according to the second configuration and / or the fourth configuration can comprise a single gas inlet, in particular arranged on the blood return line 7 or on the blood withdrawal line 6, respectively.

[0291] According to Figure 10 the fifth configuration shown, the restitution procedure implies the sequential execution of the following steps:

[0292] - allowing a predetermined amount of gas to enter the secondary chamber 4 of the filtration unit 2;

[0293] - commanding at least one of the blood return safety clamp 20a and the blood withdrawal safety clamp 20b to be in the open position, or commanding the blood return safety clamp 20a to be in the open position and the blood withdrawal safety clamp 20b to be in the closed position, or commanding the blood return safety clamp 20a to be in the closed position and the blood withdrawal safety clamp 20b to be in the open position;

[0294] - commanding the infusion of a predetermined amount of sterile fluid (F) into the blood circuit 17 by activating the dialysis fluid pump 25 and optionally stopping the dialysis liquid pump 26 or activating the dialysis liquid pump 26 at a lower speed, to determine a back filtration of the dialysis fluid through the local portion of the semi-permeable membrane 5; Figure 10 ) through the semi-permeable membrane 5;

[0295] wherein the fluid infusion step determines the position of the sterile fluid beyond the gas inlet 49, in particular the first gas inlet 49a or the second gas inlet 49b, and wherein the step defines a first fluid-blood interface FBI' and a second fluid-blood interface FBI",

[0296] and wherein the fluid infusion step implies that the sub-chamber 4 of the filtration unit is filled with both gas and sterile fluid, in particular with a volume of gas higher with respect to the volume of fluid (see Figure 10 or Figure 11 ) ;

[0297] - determining the partial blood restitution (R) through the blood return line 7 due to the sterile fluid infusion ( Figure 7 ), the blood return safety clamp 20a being arranged in the open position;

[0298] - commanding the gas inlet 49 to be in the open position, the blood return safety clamp 20a to be in the closed position, the blood withdrawal safety clamp 20b to be in the open position;

[0299] - commanding the activation of the blood pump 21 in the direction towards the second end of the blood withdrawal line 6 to draw a predetermined amount of gas from the gas inlet 49 into the blood circuit 17 ( Figure 8 ), the gas inlet 49 being arranged on the blood return line 7, as close as possible to the patient, wherein the step defines a first gas-fluid interface GFI' and a second gas-fluid interface GFI", and determines the movement of the second gas-fluid interface GFI" and of the second fluid-blood interface FBI" towards the second end of the blood withdrawal line 6, thus determining the blood restitution to the patient P through the blood withdrawal line 6.

[0300] Figure 12A flow chart representing the main steps of a blood return procedure 400 is shown, including a step 200 of infusing a predetermined amount of sterile fluid from a supply source 50 into the blood circuit 17, and a subsequent step 300 of allowing a predetermined amount of gas to enter the blood circuit 17 from the gas inlet 49. Step 200 determines a sub-step 201' of defining a first fluid-blood interface FBI' and a sub-step 201" of defining a second fluid-blood interface FBI'. In addition, step 200 determines a sub-step 202' of moving the first fluid-blood interface FBI' toward the patient's venous access, thereby causing partial blood return, and a sub-step 202" of moving the second fluid-blood interface FBI' toward the patient's arterial access, thereby causing another partial blood return. Step 300 determines a sub-step 301' of defining a first gas-fluid interface GFI' and a sub-step 301" of defining a second gas-fluid interface GFI". In addition, step 300 determines a sub-step 302' of moving the first fluid-blood interface FBI' and the first gas-fluid interface GFI' toward the patient's venous access to cause blood return and a sub-step 302" of moving the second fluid-blood interface FBI" and the second gas-fluid interface GFI" toward the patient's arterial access to complete blood return.

[0301] Figure 13 A flow chart showing the main steps of a blood return procedure 800 is shown, including a step 500 of allowing a certain amount of gas to enter the secondary chamber 4 of the filtration unit 2, and a step 600 of injecting a predetermined amount of sterile fluid from the supply source 50 into the blood circuit 17. Optionally, the return procedure 800 further includes a subsequent step 700 of allowing a predetermined amount of gas to enter the blood circuit 17 from the gas inlet 49. Step 500 determines a step 501 defining a gas-fluid interface in the secondary chamber of the filtration unit 2, the interface being Figure 10 、 Figure 11 Marked as GFI FStep 600 determines a sub-step 601'of defining a first fluid-blood interface FBI' and a sub-step 601 " of defining a second fluid-blood interface FBI" inside the blood circuit 17. Furthermore, step 600 determines a sub-step 602' of moving the first fluid-blood interface FBI' towards the venous access of the patient thereby causing a partial blood return and a sub-step 602" of moving the second fluid-blood interface FBI" towards the arterial access of the patient thereby causing a further partial blood return. Optional step 700 determines a sub-step 701'of defining a first gas-fluid interface GFI' and a sub-step 701 " of defining a second gas-fluid interface GFI". Furthermore, step 700 determines a sub-step 702' of moving the first fluid-blood interface FBI' and the first gas-fluid interface GFI' towards the venous access of the patient thereby causing a blood return and a sub-step 702" of moving the second fluid-blood interface FBI" and the second gas-fluid interface GFI" towards the arterial access of the patient thereby completing the blood return.

[0302] While this application 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 application is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements.

Claims

1. A device for extracorporeal blood treatment (1), comprising: - a filtration unit (2) having a primary chamber (3) and a secondary chamber (4) separated by a semipermeable membrane (5); - A blood circuit (17), comprising at least: a blood withdrawal line (6) extending between a first end connected to an inlet of the main chamber and a second end adapted to be connected to a patient (P); and a blood return line (7) extending between a first end connected to the outlet of the main chamber (3) and a second end adapted to be connected to the patient (P); - a blood pump (21) operable on said blood circuit (17); - a fluid circuit (32), comprising at least: a dialysis fluid effluent line (13) connected to the outlet of the secondary chamber (4); A fluid supply source (50) for providing sterile fluid; - at least one gas inlet (49) for allowing gas to enter the blood circuit (17); - a control unit (12) configured to perform a blood return procedure to the patient (P) before disconnecting the patient to end the extracorporeal blood treatment, the blood return procedure comprising the following steps: infusing a predetermined amount of sterile fluid from the supply source (50) into the blood circuit (17), the infusing the predetermined amount of sterile fluid defining at least one fluid-blood interface (FBI) in the blood circuit (17); a predetermined amount of gas is allowed to enter the blood circuit (17) from the gas inlet (49) to define at least one gas fluid interface (GFI) in the blood circuit (17), wherein at least a portion of a sterile fluid is interposed between the at least one fluid-blood interface (FBI) and the at least one gas-fluid interface (GFI); Simultaneously move the following towards the patient (P) to return some of the blood to the patient (P) before disconnecting from the patient: o at least part of the extracorporeal blood contained in the blood circuit (17), o said at least partially sterile fluid between the fluid-blood interface (FBI) and the gas-fluid interface (GFI), and oAt least some gas.

2. The device according to claim 1, wherein The fluid circuit (32) further comprises a dialysis fluid supply line (8) connected to the inlet of the secondary chamber (4), the fluid supply source (50) being a dialysis fluid supply source and providing dialysis fluid to at least the dialysis fluid supply line (8), wherein the step of infusing a predetermined amount of sterile fluid from the dialysis fluid supply source (50) into the blood circuit (17) comprises back-filtering the dialysis fluid through the semipermeable membrane (5) into the blood circuit (17), back-filtering sufficient dialysis fluid to at least reach and exceed the location of the gas inlet (49).

3. The device according to claim 1, wherein The fluid circuit (32) further comprises an infusion line (39) fluidly connected to the blood circuit (17), the infusion line (39) being configured to infuse a sterile fluid into the blood circuit (17), the sterile fluid being a replacement fluid or saline, The infusion line (39) is fluidly connected to the blood circuit (17) at an infusion point between the first end and the second end of the blood withdrawal line (6) or the blood return line (7), wherein the fluid supply source (50) is a dialysis fluid supply source connected to the infusion line (39) to provide dialysis fluid to at least the infusion line (39), or wherein the fluid supply source (50) is a replacement fluid supply source, providing replacement fluid to at least the infusion line (39), or wherein the fluid supply source (50) is a sterile fluid supply source, providing sterile fluid to at least the infusion line (39), and The step of infusing a predetermined amount of sterile fluid from the dialysis fluid supply source (50) into the blood circuit (17) comprises infusing the sterile fluid directly into the blood circuit (17) through the infusion line (39), infusing a sufficient amount of sterile fluid to at least reach and exceed the position of the gas inlet (49).

4. The device according to claim 1, wherein The at least one fluid-blood interface (FBI) comprises a first fluid-blood interface (FBI') and a second fluid-blood interface (FBI") in the blood circuit (17), wherein the first fluid-blood interface (FBI') is between the sterile fluid and the second end of the blood return line (7), and the second fluid-blood interface (FBI") is between the sterile fluid and the second end of the blood withdrawal line (6), and wherein the at least one gas-fluid interface (GFI) comprises a first gas-fluid interface (GFI') and a second gas-fluid interface (GFI") in the blood circuit (17), wherein, at least after gas has entered the blood circuit (17), at least part of the sterile fluid is interposed between the first fluid-blood interface (FBI') and the first gas-fluid interface (GFI'), and / or at least part of the sterile fluid is interposed between the second fluid-blood interface (FBI") and the second gas-fluid interface (GFI").

5. The device according to claim 4, wherein The step of allowing gas to enter determines that the sterile fluid infused into the blood circuit (17) is divided into a first sterile fluid portion and a second sterile fluid portion, wherein the first sterile fluid portion is between the first fluid-blood interface (FBI') and the first gas-fluid interface (GFI'), and the second sterile fluid portion is between the second fluid-blood interface (FBI") and the second gas-fluid interface (GFI"). The blood return procedure includes moving the first sterile fluid portion toward the second end of the blood return line (7) and simultaneously or sequentially moving the second sterile fluid portion toward the second end of the blood withdrawal line (6).

6. The device according to claim 5, wherein The blood return procedure includes moving the first fluid-blood interface (FBI') and the first gas-fluid interface (GFI') toward the second end of the blood return line (7), and moving the second fluid-blood interface (FBI") and the second gas-fluid interface (GFI") toward the second end of the blood withdrawal line (6), The volume of the first sterile fluid portion and / or the second sterile fluid portion is comprised between 50 ml and 200 ml.

7. The device according to claim 3, comprising a blood return safety clamp (20a) arranged on the blood return line (7) and a blood extraction safety clamp (20b) arranged on the blood extraction line (6), in, The control unit (12) is configured to command the blood return safety clamp (20a) and the blood withdrawal safety clamp (20b) between an open position allowing flow and a closed position preventing flow, wherein the at least one gas inlet (49) includes a first gas inlet (49a) arranged on the blood return line (7) and a second gas inlet (49b) arranged on the blood extraction line (6), and the safety clips (20a, 20b) are arranged closer to the vascular access (18) of the patient (P) than the corresponding one of the first gas inlet (49a) and the second gas inlet (49b), And wherein the blood pump (21) is arranged on the blood extraction line (6), the second gas inlet (49b) is between the blood pump (21) and the second end of the blood extraction line (6), and the device includes at least one shut-off element (59) connected to the at least one gas inlet (49).

8. The device according to claim 7, comprising a first shut-off element (59a) connected to the first gas inlet (49a) and a second shut-off element (59b) connected to the second gas inlet (49b), The control unit (12) is configured to command the at least one shut-off element (59) between an open position allowing gas flow and a closed position preventing gas flow.

9. The device according to claim 8, wherein The control unit (12) is configured to execute a return procedure according to a first configuration, the return procedure comprising sequentially executing the following steps: - commanding the infusion of a predetermined amount of sterile fluid into the blood circuit (17) through the infusion line (39) or through the back-filtered dialysis fluid through the semipermeable membrane (5), said step determining the position of the sterile fluid beyond the gas inlet (49), said step defining a first fluid-blood interface (FBI') and a second fluid-blood interface (FBI"); - Commanding the first shut-off element (59a) of the first gas inlet (49a) on the blood return line (7) to be in the open position, the second shut-off element (59b) of the second gas inlet (49b) on the blood extraction line (6) to be in the closed position, the blood return safety clamp (20a) to be in the closed position, and the blood extraction safety clamp (20b) to be in the open position; - commanding activation of the blood pump (21) in the direction towards the second end of the blood withdrawal line (6) so as to draw a predetermined amount of gas from the first gas inlet (49a) into the blood circuit (17), said step defining a first gas-fluid interface (GFI') and a second gas-fluid interface (GFI") and determining that the second gas-fluid interface (GFI") and the second fluid-blood interface (FBI") move towards the second end of the blood withdrawal line (6), thereby performing a partial blood return to the patient (P) through the blood withdrawal line (6); - commanding the blood extraction safety clamp (20b) to be in the closed position, the blood return safety clamp (20a) to be in the open position, the first shut-off element (59a) of the first gas inlet (49a) on the blood return line (7) to be in the closed position, and the second shut-off element (59b) of the second gas inlet (49b) on the blood extraction line (6) to be in the open position; - commanding activation of the blood pump (21) in the direction towards the second end of the blood return line (7), said step determining a first gas-fluid interface (GFI') and a first fluid-blood interface (FBI'), moving towards the second end of the blood return line (7), thereby returning a certain amount of blood to the patient (P) through the blood return line (7).

10. The device according to claim 9, wherein The return procedure includes performing the following steps: Prior to the step of infusing sterile fluid into the blood circuit (17), at least one of the blood return safety clamp (20a) and the blood withdrawal safety clamp (20b) is commanded to be in an open position, and: The blood return safety clamp (20a) is in the open position; and The blood extraction safety clamp (20b) is in the closed position or the blood pump (21) is stopped.

11. The device according to claim 8, wherein According to the second configuration, the return procedure means sequentially executing the following steps: - commanding the infusion of a predetermined amount of sterile fluid into the blood circuit (17) through the infusion line (39) or through the back-filtered dialysis fluid through the semipermeable membrane (5), said step determining the position of the sterile fluid beyond the gas inlet (49) arranged on the blood return line (7), said step defining a first fluid-blood interface (FBI') and a second fluid-blood interface (FBI"); - determining the return of part of the blood through the blood return line (7) due to the infusion of sterile fluid, the blood return safety clamp (20a) being in the open position; - commanding the shut-off element (59) of the gas inlet (49) to be in the open position, the blood return safety clamp (20a) to be in the closed position, and the blood extraction safety clamp (20b) to be in the open position; - commanding the activation of the blood pump (21) in the direction towards the second end of the blood withdrawal line (6) so that a predetermined amount of gas is sucked from the gas inlet (49) into the blood circuit (17), said step determining a second gas-fluid interface (GFI") and a second fluid-blood interface (FBI"), moving towards the second end of the blood withdrawal line (6), thereby returning blood to the patient (P) through the blood withdrawal line (6).

12. The device according to claim 9, comprising a gas supply unit (60) connected to the at least one gas inlet (49) and configured to force-infuse gas into the blood circuit (17), in, According to the third configuration, the return procedure means sequentially performing the following steps: - commanding the infusion of a predetermined amount of sterile fluid into the blood circuit (17) through the infusion line (39) or through the back-filtered dialysis fluid through the semipermeable membrane (5), said step determining the position of the sterile fluid beyond the gas inlet (49), said step defining a first fluid-blood interface (FBI') and a second fluid-blood interface (FBI"); - commanding the shut-off element (59) of the at least one gas inlet (49) to be in the open position; - commanding at least one of the blood return safety clamp (20a) and the blood withdrawal safety clamp (20b) to be in an open position; - Commanding activation of the gas supply unit (60) to infuse gas into the blood circuit (17), which step determines that the at least one gas-fluid interface (GFI) and the at least one fluid-blood interface (FBI) move toward the second end of the blood extraction line (6), thereby returning a certain amount of blood to the patient (P) through the blood extraction line (6), and / or at least one gas-fluid interface (GFI) and at least one fluid-blood interface (FBI) move toward the second end of the blood return line (7), thereby returning a certain amount of blood to the patient (P) through the blood return line (7).

13. The device according to claim 12, wherein The step of commanding activation of the gas supply unit (60) to infuse gas into the blood circuit (17) determines: o the second gas-fluid interface (GFI") and the second fluid-blood interface (FBI") move toward the second end of the blood extraction line (6), thereby returning a certain amount of blood to the patient (P) through the blood extraction line (6); and / or o the first gas-fluid interface (GFI') and the first fluid-blood interface (FBI') move toward the second end of the blood return line (7), thereby returning a certain amount of blood to the patient (P) through the blood return line (7); Prior to the step of infusing sterile fluid into the blood circuit (17), at least one of the blood return safety clamp (20a) and the blood withdrawal safety clamp (20b) is commanded to an open position.

14. The device according to claim 12, wherein The gas supply unit (60) is a gas pump.

15. The device according to claim 12, wherein The control unit (12) is configured to command the blood to return to the position of the safety clamp (20a) or the blood extraction safety clamp (20b) during the step of infusing gas into the blood circuit (17) by the gas supply unit (60) according to the third configuration of the return procedure to determine: - when the blood return safety clamp (20a) and the blood extraction safety clamp (20b) are both commanded to the open position, simultaneous blood return is performed through the blood extraction line (6) and the blood return line (7), wherein the first fluid-blood interface (FBI') and the first gas-fluid interface (GFI') move toward the second end of the blood return line (7), and the second fluid-blood interface (FBI") and the second gas-fluid interface (GFI") move toward the second end of the blood extraction line (6); or - arterial blood return is performed through the blood withdrawal line (6) when the blood return safety clamp (20a) is commanded to the closed position and the blood withdrawal safety clamp (20b) is commanded to the open position, wherein the second fluid-blood interface (FBI") and the second gas-fluid interface (GFI") move toward the second end of the blood withdrawal line (6); or - When the blood return safety clamp (20a) is commanded to the open position and the blood withdrawal safety clamp (20b) is commanded to the closed position, venous blood return is performed through the blood return line (7), wherein the first fluid-blood interface (FBI') and the first gas-fluid interface (GFI') move towards the second end of the blood return line (7).

16. The device according to any one of the preceding claims 1 to 6, wherein The control unit (12) is configured to stop the return procedure in the following circumstances: the at least one fluid-blood interface (FBI) is proximate to at least one of the second end of the blood withdrawal line (6) and the second end of the blood return line (7), or a predetermined amount of sterile fluid has been infused into the patient; and / or The at least one gas-fluid interface (GFI) reaches a preset distance of less than 10 cm from at least one of the second end of the blood extraction line (6) and the second end of the blood return line (7), the distance being measured along the respective blood line.

17. The device according to any one of the preceding claims 1 to 6, wherein The control unit is configured to infuse sterile fluid into the blood circuit (17) and to allow gas to enter the blood circuit (17) such that the distance between a fluid-blood interface (FBI) and a gas-fluid interface (GFI) is comprised between 0.5 cm and 10 cm, the distance being measured along the corresponding blood line.

18. The device according to any one of the preceding claims 1 to 6, wherein The blood circuit (17) defines an internal volume of the blood circuit, which is determined by at least the internal volumes of the blood extraction line (6) and the blood return line (7).

19. The device according to claim 18, wherein The blood circuit internal volume is also determined by the air separator (19) and the main chamber (3) of the filter unit (2), Therein, the predetermined volume of sterile fluid is comprised between 1% and 60% of the internal volume of the blood circuit.

20. The device according to any one of the preceding claims 1 to 6, wherein The blood circuit (17) comprises at least one gas sensor, which is arranged close to the second end of the blood withdrawal line (6) and / or the second end of the blood return line (7), the gas sensor being configured to provide a signal indicating the presence of gas in the respective blood line, The control unit (12) is configured to receive the signal and stop the travel of the at least one gas fluid interface (GFI).

21. The device according to claim 20, wherein The control unit is configured to perform at least one of the following operations: - stopping the blood pump (21); - moving the blood withdrawal safety clamp (20b) to the closed position if the gas sensor of the blood withdrawal line (6) detects the presence of gas; - If the gas sensor of the blood return line (7) detects the presence of gas, the blood return safety clamp (20a) is moved to the closed position.

22. The device according to claim 20, comprising a gas supply unit (60) connected to the at least one gas inlet (49) and configured to force-infuse gas into the blood circuit (17), wherein The control unit is configured to perform at least one of the following operations: - stopping the gas supply unit (60); - moving the blood withdrawal safety clamp (20b) to the closed position if the gas sensor of the blood withdrawal line (6) detects the presence of gas; - If the gas sensor of the blood return line (7) detects the presence of gas, the blood return safety clamp (20a) is moved to the closed position.

23. The device according to any one of the preceding claims 1 to 6, wherein During the blood return procedure, during gas infusion, the blood withdrawal line (6) and the blood return line (7) are both connected to the cardiovascular access (18) of the patient (P), The step of infusing the predetermined amount of sterile fluid determines a partial return of blood to the patient, and the volume of blood returned to the patient is substantially equal to the volume of the predetermined amount of sterile fluid.

Images