Abstract:
An extracorporeal blood chamber ( 12 ) comprises an expansion reservoir ( 47 ) having a first access ( 48 ) arranged laterally and a second access ( 49 ) arranged on the bottom of the chamber ( 12 ). The chamber comprises, integrally with the reservoir, a first conduit terminating in the first access, a second conduit terminating in the first access, and a third conduit terminating in the second access. The extracorporeal blood enters the reservoir through the first conduit and there mixes with an infusion fluid which enters through the second conduit. The resulting mixture exits through the third conduit. The chamber is used in a hemo(dia)filtration apparatus to mix the blood optimally with the replacement fluid.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an extracorporeal blood chamber, to an extracorporeal blood line and to an apparatus for treatment of extracorporeal blood. 
     In particular the extracorporeal blood chamber is for air/liquid separation and/or for the mixing of two liquids, for example blood and an infusion liquid. 
     Specifically, though not exclusively, the invention can be usefully applied in a hemo(dia)filtration system for mixing extracorporeal blood with a replacement fluid. 
     U.S. Pat. No. 5,605,540 describes an extracorporeal blood chamber provided with an expansion chamber having on a bottom thereof a first and a second access and at the top thereof at least a third access; the blood chamber is further provided with a first and a second conduit, terminating respectively in the first and second accesses, and with a third conduit terminating in the first conduit. In use the first and the second conduit transport blood, while the third conduit transports an infusion liquid. 
     U.S. Pat. No. 4,681,606 describes an extracorporeal blood chamber provided with an expansion chamber having at a bottom thereof a first access, on a side thereof a second access, and at a top thereof two further accesses; the blood chamber also has a first and a second conduit terminating respectively in the first and the second access. In use the first and the second conduit transport blood, while one of the top accesses is connected to an injection tube. 
     U.S. Pat. No. 5,591,251 describes an extracorporeal blood chamber provided with an expansion chamber having at a bottom thereof a first access, on a side thereof a second access, and at a top thereof another two accesses; the blood chamber further has a conduit terminating in the first lateral access. In use the first and the second access are for the passage of blood, while one of the top accesses is for passage of an infusion liquid. 
     U.S. Pat. No. 4,666,598 describes an extracorporeal blood chamber provided with an expansion chamber having on a bottom thereof a first access and on a side thereof a second access; the blood chamber also has a first conduit terminating in the first access, a second conduit terminating in the second access, and a third conduit terminating in the first conduit. In use the first and the second conduits transport blood, while the third conduit transports an infusion liquid. 
     The prior-art extracorporeal blood chambers can be improved upon in relation to the effectiveness of the mixing between the blood and the infusion liquid, especially in the case of a hemo(dia)filtration treatment with mixing between the blood and the replacement liquid upstream of the hemo(dia)filter (pre-dilution). In a case of pre-dilution the effectiveness of the hemo(dia)filtration treatment depends on the degree of mixing between the blood and the replacement liquid at the inlet of the hemo(dia)filter. 
     SUMMARY OF THE INVENTION 
     An aim of the present invention is to provide an extracorporeal blood chamber with which very good mixing results of the blood with an infusion liquid can be obtained. 
     A further aim of the invention is to realise an extracorporeal blood line comprising the above-mentioned blood chamber. 
     A further aim of the invention is to provide an apparatus for extracorporeal blood treatment comprising the above-cited blood line. 
     An advantage of the invention is that it provides an extracorporeal blood chamber which is able efficiently to separate the air from the liquid, in particular the air contained in the infusion liquid. 
     A further advantage is that it makes available an extracorporeal blood chamber which reduces to a minimum the turbulence in the blood flow in the case of absence of infusion liquid flow, i.e. when the blood is not mixed with the liquid. 
     A still further advantage is that the extracorporeal blood chamber is compact and small. 
     The aims and more besides are all attained by the invention, as it is characterised in one or more of the appended claims. 
     Further characteristics and advantages of the present invention will better emerge from the detailed description that follows, of at least an embodiment of the invention, illustrated by way of non-limiting example in the figures of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description will be made herein below with reference to the appended figures of the drawings, provided by way of non-limiting example, in which: 
         FIG. 1  is a diagram of the hemo(dia)filtration apparatus of the invention; 
         FIG. 2  is a front view of an apparatus made according to the diagram of  FIG. 1 , and applied operatively to the front panel of a machine for dialysis; 
         FIG. 3  is a perspective view from behind of the apparatus of  FIG. 2 , with some parts removed better to evidence others; 
         FIG. 4  is a perspective view from the front of  FIG. 3 ; 
         FIG. 5  is a perspective view from behind of the infusion module of the apparatus of  FIG. 3 , with some parts removed and other parts added with respect to  FIG. 3 ; 
         FIG. 6  is a view from the front of  FIG. 5 ; 
         FIG. 7  is a front view of a component of the infusion module of  FIG. 3  which includes the blood chamber  12  in which the mixing between the blood and the infused liquid takes place; 
         FIG. 8  is a view from behind of  FIG. 7 ; 
         FIG. 9  is a view from above of  FIG. 7 ; 
         FIG. 10  is a view from below of  FIG. 7 ; 
         FIG. 11  is a view from the left of  FIG. 7 ; 
         FIGS. 12 ,  13 ,  14  and  15  are sections according respectively to lines XII, XIII, XIV and XV of  FIGS. 7 ,  8  and  11 . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 ,  1  denotes in its entirety an extracorporeal blood treatment apparatus destined for coupling to a machine is for extracorporeal blood treatment able to provide a treatment fluid. In the following description the extracorporeal blood treatment apparatus will be called a hemo(dia)filtration apparatus  1 , the extracorporeal blood treatment machine will be called a dialysis machine and the treatment fluid will be called dialysis fluid, without any more generalised references being lost by use of this terminology. In particular the dialysis machine produces on-line a dialysis fluid of predetermined chemical composition (for example by mixing water and solid and/or liquid concentrates). The dialysis machine is able to reduce the concentration of endotoxins in the dialysis fluid (for example by passage of dialysis fluid through one or more stages of ultrafiltration). The dialysis machine is able to provide a control system of patient weight loss during the treatment (for example by a control of the difference between the dialysis fluid delivery at the inlet and outlet of the blood treatment device thanks to the use of two pumps arranged before and after the blood treatment device—hereinafter hemo(dia)filter—and of two flow-meters arranged before and after the hemo(dia)filter). The hemo(dia)filtration apparatus  1  can be composed, all or in part, by disposable elements. The dialysis machine (of which the front panel is partially illustrated in  FIG. 2 ) is of known type, is provided with a fresh dialyser fluid port  2  (see the diagram of  FIG. 1 ), from which the dialysis fluid to be introduced in the hemo(dia) filter is taken, an exhausted fluid port  3 , in which the fluid exiting the hemo(dia)filter is discharged (made up of used dialysis fluid and/or of ultrafiltrate), and an on-line port  4  from which the dialysis fluid, to be processed for use as replacement fluid in hemo(dia)filtration treatment, is taken. The dialysis machine is further provided with a system of known type and not illustrated, for preparation of the dialysis fluid; this system is connected to a main dialysis fluid supply line, which terminates in the fresh dialysate port  2 . A secondary dialysis fluid supply line, which branches from the main supply line, terminates in the on-line port  4 . The dialysis machine is further provided with an exhausted liquid discharge line which originates at one end at the exhausted liquid port  3  and which terminates at the other end thereof in a drainage (of known type and not illustrated). When the hemo(dia)filtration apparatus  1  is used as a hemofiltration apparatus  1 , the fresh dialysate port  2  is closed, or non-operative, or, in a further embodiment, absent. 
     The hemo(dia)filtration apparatus  1  comprises the hemo(dia)filter  5  having a blood chamber and a fluid chamber (not illustrated) which are separated from one another by a semipermeable membrane (not illustrated) which, in this case, comprises a bundle of hollow fibres. In this embodiment the blood chamber comprises the space internally of the hollow fibres, while the fluid chamber comprises the space externally of the hollow fibres. The fluid chamber is further at least partially defined by the tubular body containing the bundle of hollow fibres. The hemo(dia)filtration apparatus  1  comprises an extracorporeal blood circuit having an arterial line  6 , or a blood removal line from the patient for the blood to be treated in the hemo(dia)filter  5 , and a venous line  7 , or patient return line for the blood treated in the hemo(dia)filter  5 . The hemo(dia)filtration apparatus  1  further comprises a blood pump  8  for circulation of blood in the extracorporeal circuit. The blood pump  8  is of a tube-deforming rotary type (peristaltic). The extracorporeal blood circuit further comprises the blood chamber of the hemo(dia)filter  5 . The arterial line  6  comprises an arterial patient end  9 , a pre-pump arterial expansion chamber  10 , a blood pump tube tract  11 , a post-pump arterial expansion chamber  12 , an arterial device end  13 . The venous line  7  comprises a venous device end  14 , a venous expansion chamber  15 , a venous patient end  16 . The dialysis machine is provided with an arterial clamp  17  operating on the arterial line  6 , in particular between the patient arterial end  9  and the pre-pump arterial expansion chamber  10 . The dialysis machine is provided with a venous clamp  18  operating on the venous line  7 , in particular between the patient venous end  16  and the venous expansion chamber  15 . The patient arterial end  9 , like the patient venous end  16 , is designed for connection (directly or via a vascular access device of known type) with a vascular access of a patient. The arterial clamp  17 , respectively the venous clamp  18 , serves for closing a squeezable tract of the arterial line  6 , respectively of the venous line  7 , on command of a control unit of the dialysis machine. The pre-pump arterial expansion chamber  10 , which is arranged downstream of the arterial clamp  17  (where “downstream” means with reference to the blood circulation direction during the treatment), serves for separating the air contained in the blood and for monitoring the arterial blood pressure (before the blood pump  8 ). The venous expansion chamber  15 , which is arranged upstream of the venous clamp  18  (where “upstream” means with reference to the blood circulation direction during the treatment), is for separating the air contained in the blood and for monitoring the venous blood pressure. The pre-pump arterial expansion chamber  10 , like the venous expansion chamber  15 , is designed to give rise to a liquid level separating a lower part full of liquid (blood) from an upper part full of gas (air). Each of the expansion chambers  10  and  15  is provided, for example superiorly, with a zone predisposed for pressure reading; this zone comprises, in the specific case, a membrane device, of known type, having a deformable elastic membrane with an internal surface in contact with the fluid (blood and/or air) contained in the chamber and an external surface operatively associable to a pressure sensor of the dialysis machine. The blood pump tube tract  11 , which is designed for removably coupling with the blood pump  8 , is open-ring conformed (in the specific embodiment it is U-shaped with a horizontal lie and with the convexity facing right, with reference to the viewpoint of a user situated in front of the front panel of the dialysis machine) with two ends, one for blood inlet and the other for blood outlet, fluidly and mechanically connected to two tubular extensions  19  ( FIG. 2 ) solidly connected to the pre-pump arterial expansion chamber  10 . The arterial device end  13  and the venous device end  14  are designed for removably coupling with an inlet port (in the specific embodiment, upper) and, respectively, an outlet port (in the specific embodiment, lower) of the blood chamber of the hemo(dia)filter  5 . The pre-pump arterial expansion chamber  10  and the venous expansion chamber  15  are integrated in a cartridge structure of known type. 
     The post-pump arterial expansion chamber  12  is inserted in the arterial line  6  between the blood pump  8  and the hemo(dia)filter  5 . The post-pump arterial expansion chamber  12  comprises a blood inlet port  20 , an infusion fluid inlet port  21  (in the present example of hemo(dia)filtration with pre-dilution, the infusion fluid, or infusate, can be replacement fluid, or substituate; in the following description the specific term “replacement fluid” and “substituate” will be used instead of more general terms like “infusion fluid” and “infusate”, without the generalised meaning being compromised), a mixing zone where the blood and replacement fluid are mixed, and an outlet port for the blood-fluid mixture  22  (where the replacement fluid is present in the mixture in case of pre-dilution and absent in case of no pre-dilution). 
     The post-pump arterial expansion chamber  12  serves to separate the air contained in the replacement fluid. The post-pump arterial expansion chamber  12  monitors the pressure in the replacement fluid supply line. The post-pump arterial expansion chamber  12  also serves to further separate the air contained in the blood along the arterial line  6  downstream of the blood pump  8  and for monitoring the blood pressure in the arterial line  6  between the blood pump and the hemo(dia)filter  5 . The post-pump arterial expansion chamber  12  is designed to produce a liquid level that separates a lower part which is full of liquid (blood or blood/replacement fluid mixture) and an upper part which is full of gas (air). The post-pump arterial expansion chamber  12  is provided, for example superiorly, with a zone predisposed for pressure detection; this zone comprises, in the present embodiment, a membrane device  58 , of known type, having a deformable membrane with an internal surface in contact with the fluid contained in the chamber and an external surface which is operatively associable to a pressure sensor of the dialysis machine. The post-pump arterial expansion chamber  12  will be described in greater detail herein below. 
     The hemo(dia)filtration apparatus  1  comprises a replacement fluid supply line  23  which provides, in this embodiment, the replacement fluid (substituate) to the extracorporeal blood circuit. The supply line  23  takes the dialysis fluid from the on-line port  4  and, after an ultrafiltration treatment to make it suitable as a replacement fluid, conveys it to the extracorporeal blood circuit. 
     The supply line  23  branches out from a main branch  24  into a pre-dilution branch  25  fluidly connected to the arterial line  6  and a post-dilution branch  26  fluidly connected to the venous line  7 . The replacement fluid supply line  23  comprises an inlet end  27  having a connector for removable connection with the on-line port  4  for sourcing the dialysis fluid supplied by the dialysis machine. Alternatively to an on-line port of a machine for dialysis fluid preparation, other fluid sources can be used, for example a ready-prepared dialysis fluid or replacement fluid recipient, or a centralised dialysis fluid supply system, supplying to various units. 
     The replacement fluid supply line  23  comprises an ultrafilter  28  predisposed fluidly in the main branch  24  upstream of the branch-out for ultrafiltering the dialysis fluid taken from the dialysis machine to render the fluid suitable for use as a replacement fluid. The ultrafilter  28  reduces the endotoxin percentage in the fluid. The ultrafilter  28  comprises a semipermeable membrane that separates a first chamber containing the fluid to be ultrafiltered (dialysis fluid) from a second chamber containing the ultrafiltered fluid (replacement fluid). The semipermeable membrane comprises, in the present embodiment, a bundle of hollow fibres. The first chamber of the fluid to be ultrafiltered comprises the inside of the hollow fibres, while the second chamber of the ultrafiltered fluid is defined between the outside of the hollow fibres and the tubular body enclosing the bundle of hollow fibres. 
     The ultrafilter  28  is further provided, for example superiorly, with a vent line of the air communicating with the first chamber of the fluid to be ultrafiltered and having a clamp (for example manually activated) for intercepting and a vent into the atmosphere protected by a protection device (for example a hydrophobic membrane). 
     The replacement fluid supply line  23  can further comprise a check valve predisposed fluidly in the main branch  24  upstream of the branch-out. The check valve, which in the present embodiment is not present, might be located after the ultrafilter  28 . 
     A tract of the replacement fluid pump tube  29  is predisposed in the supply line  23  for coupling with a replacement fluid circulation pump  30 . In to the present embodiment the replacement fluid pump  30  is a tube-deforming rotary pump (peristaltic). The replacement fluid pump tube tract  29  is open-ring shaped with an aspiration end and a delivery end. In particular the replacement fluid pump tube tract  29  is U-shaped, and, in the use configuration with the pump  30 , lies on a vertical plane, with the two end branches arranged horizontally (the convexity of the U is directed oppositely to the blood pump tube tract  11 , i.e. in the present embodiment to the left with reference to the viewpoint of a user situated in front of the front panel of the machine). The rotation axes of the two rotary pumps  8  and  30  are parallel to one another. The pump tube tract  29 , in the engaged configuration with the pump  30 , is arranged symmetrically to the blood pump tube tract  11 , with respect to a plane of symmetry (in the present embodiment, vertical) which is parallel to the rotation axes of the two rotary pumps  8  and  30 . The replacement fluid pump tube tract  29  is fluidly arranged in the main branch  24  upstream of the branch-out (where “upstream” means in reference to the circulation direction of the replacement fluid). The replacement fluid pump tube tract  29  is arranged fluidly upstream of the ultrafilter  28 . 
     The replacement fluid supply line  23  comprises an auxiliary connection  31  fluidly arranged after the ultrafilter  28 . This auxiliary connection  31  is branched out from the replacement fluid line  23 . The auxiliary line is further provided with a clamp  32  (for example a manually operated clamp) for closing the auxiliary line, and a protection hood for removable closure of the auxiliary line  31 . The auxiliary line branches off from the main branch  24  before the branch-out. 
     The auxiliary connection  31  is designed for removable fluid connection with the extracorporeal blood circuit, in particular with the arterial line  6  or the venous line  7 . The auxiliary connection  31  serves to fill the extracorporeal circuit with the replacement fluid, in particular during the circuit priming stage, i.e. during the stage preliminary to the treatment during which the air and any other undesirable particles contained in the blood circuit are evacuated and the circuit is filled with an isotonic liquid, for example a saline solution coming from a bag or, as in the present embodiment, with an isotonic fluid (dialysis fluid or saline) which is prepared by the dialysis machine, supplied to the on-line port  4  of the machine and ultrafiltered by crossing the replacement fluid supply line  23 . In the present embodiment the auxiliary connection  31  is removably couplable to the patient end of the arterial line  9  or to the patient end of the venous line  16 . The auxiliary connection  31  comprises, for example, a female luer connector couplable to a is male luer connector at the patient arterial  9  or venous  16  end. 
     At least one from among the three above-mentioned expansion chambers (arterial pre-pump  10 , arterial post-pump  12  and venous  15 ) is fluidly connected, in particular directly, to the pre-dilution branch  25  or the post-dilution branch  26 . In the present embodiment the post-pump arterial expansion chamber  12  is fluidly connected directly to the pre-dilution branch  25 . 
     The post-dilution branch  26  opens (directly) into a point of venous line  7  comprised between the hemo(dia)filter  5  and the venous chamber  15 . The venous chamber  15  therefore indirectly communicates, via a tract of venous line  7 , with the post-dilution branch  26 . 
     The aspiration and delivery ends of the replacement fluid pump tube tract  29  are rigidly connected to at least one from among the above-mentioned expansion chambers (arterial pre-pump  10 , arterial post-pump  12  and venous  15 ). In the present embodiment the aspiration and delivery ends of the replacement fluid pump tube tract  29  are connected rigidly to the post-pump arterial expansion chamber  12 . As mentioned, the expansion chamber bearing the replacement fluid pump tube tract  29 , i.e. the chamber  12 , is provided with a zone for monitoring the pressure which is predisposed for connection with a pressure sensor provided on the dialysis machine. This monitoring zone is provided with the pressure detecting device  58 . 
     Two tubular extensions for fluid and mechanical connection of the two ends of the pump tube tract  29  are solidly connected (for example are made in a single piece with the chamber itself) to the chamber  12 . The two tubular extensions are not fluidly connected to the chamber  12 , if not indirectly through other parts (for example the ultrafilter  28 ) of the fluid circuit transporting the replacement fluid. 
     The replacement fluid supply line  23  comprises a fluid communication system which is interpositioned fluidly between the delivery end of the replacement fluid pump tube tract  29  and the expansion chamber bearing the replacement fluid pump tube tract  29  (as mentioned in this case the expansion chamber bearing the pump tube tract  29  is the post-pump arterial expansion chamber  12 ). This fluid communication system comprises is one or more from the following elements: the ultrafilter  28 , the check valve (if present), the branch-out, and at least a tube tract which is flexible and closable by elastic deformation, in particular squeezing. 
     In the present embodiment, the fluid communication system, which places the replacement fluid pump tube tract  29  in communication with the extracorporeal blood circuit, comprises a first flexible tube  41  having a first end connected with a first tubular connection  42  which is rigidly connected to (but not fluidly communicating with) the post-pump arterial chamber  12  (the first tubular connection  42  is arranged inferiorly of the chamber  12  itself), and a second end which is opposite the first end and connected to a second tubular connection  43  for inlet of the ultrafilter  28  (the second tubular connection  43  for inlet is located inferiorly of the ultrafilter  28  and communicates with the chamber of the fluid to be ultrafiltered). Each of these tubular connections  42  and  43  faces downwards, with reference to an operative configuration of the apparatus  1 . Each of these tubular connections  42  and  43  has a longitudinal axis which extends, at least prevalently, in a vertical direction. 
     The above-described fluid communication system comprises the ultrafilter  28  and a second three-way flexible tube  44  having a first end which is connected to a tubular connection for outlet of the ultrafilter  28  (the tubular outlet connection is located on a side of the ultrafilter  28  itself, in particular superiorly, and communicates with the ultrafiltrate fluid chamber, i.e. with the outside of the hollow fibres), a second end (arranged superiorly and facing upwards) to which the auxiliary connection  31  is connected by means of the auxiliary line, and a third end (arranged inferiorly and facing downwards). 
     The above-mentioned three ends of the second flexible tube  44  are in reciprocal fluid communication (for example with reciprocal T or Y arrangement). The second three-way flexible tube  44 , which in the present embodiment is T-shaped with the first end arranged at 90° to the other two, is press-formed by injection of a soft plastic material. 
     The fluid communication system comprises a third three-way flexible tube  45  having a first end which is connected to the third end of the second flexible tube  44 , a second end connected to the inlet port  21  of the replacement fluid to the chamber  12 , and a third end connected to a zone of the venous line  7  arranged upstream of the venous expansion chamber  15 . In the present embodiment the first end is arranged superiorly (facing upwards), the third end is arranged inferiorly (facing downwards), while the second end is arranged obliquely (facing upwards) with respect to the other two, forming an angle which is less than a right-angle with the first upper end. The third three-way flexible tube  45  is made by press-forming by injection of a soft plastic material. The third three-way flexible tube  45  exhibits the branch-out in the pre-dilution branches  25  and the post-dilution branches  26 , which comprise two of the three ways of the third flexible tube  45  (in particular the ways that exhibit the second and third ends). 
     The hemodiafiltration apparatus  1  is made in two distinct modules which are fluidly connected one to the other. A first module A (on the right in  FIG. 2 ) comprises an initial tract of arterial line  6  which goes from the patient arterial end  9  to the pre-pump expansion chamber  10 . The first module A further comprises the pre-pump expansion chamber  10 , the blood pump tube tract  11  and the venous expansion chamber  15  (integrated with the chamber  10  in the cartridge structure of known type). The first module A further comprises a final tract of venous line  7  which goes from the venous expansion chamber  15  to the patient venous end  16 . The first module A also comprises a tract of arterial line  6  which is arranged downstream of the blood pump  8  and which is integrated into the cartridge body structure. As mentioned, the cartridge structure, which incorporates the chambers  10  and  15 , supports the two ends, aspiration and delivery, of the blood pump tube tract  11 . 
     A second module B (on the left in  FIG. 2 ) comprises the replacement fluid supply line  23  (starting from the inlet end  27 , and including the replacement fluid pump tube tract  29 , the ultrafilter  28  and the pre-dilution and post-dilution branches  25  and  26 ). The second module B further comprises the post-pump arterial expansion chamber  12 . Also included are an intermediate tract of arterial line  33  which fluidly connects an arterial outlet of the first module A (connected to an outlet of the blood pump tube tract) with an arterial inlet of the second module B (connected to the blood inlet of the post-pump arterial expansion chamber), and an intermediate tract of venous line  34  which fluidly connects a venous outlet of the second module B (connected with the post-dilution branch  26 ) with a venous inlet of the first module A (connected with an inlet of the venous expansion chamber). 
     The second module B comprises a support element to which the supply line of the replacement fluid  23  is constrained in order that the pre-dilution  25  and post-dilution branches  25  and  26  are positioned in a prefixed position with respect to the post-pump arterial expansion chamber. The correct and stable positioning of the pre-dilution and post-dilution branches  25  and  26  with respect to the front panel of the dialysis machine enables operatively efficient use of the above-said branches with two control valves, a pre-dilution control valve  52  and a post-dilution control valve  53  arranged on the front panel. 
     The support element comprises, in the present embodiment, one or more extensions  35  which emerge from the expansion chamber which bears the replacement fluid pump tube tract  29  (i.e. the post-pump arterial chamber  12 ). The extensions  35  emerge from a side of the chamber  12  located on the opposite side with respect to the replacement fluid pump tube tract  29  and extend in an opposite direction with respect to the extension of the pump tract  29  itself. The extensions  35 , in the present embodiment, are rigidly connected to the chamber  12  that bears the replacement fluid pump tube tract  29 . The extensions  35 , in the present embodiment, are made (for example by press-forming of plastic material) in a single piece with the chamber  12  itself. The support element further comprises a casing  36  engaged to one or more of the extensions  35 . The casing  36  in the present embodiment is joint-coupled to one or more of the extensions  35 . In particular the casing  36  is coupled to one or more of the extensions  35  in at least two joint zones. The casing  36 , made of plastic material, is provided with a front part which at least partially contains the tubular body of the ultrafilter  28 . 
     One of the extensions  35  exhibits a mounting extension  37  which, in collaboration with the two tubular extensions  38  for engagement of the ends of the replacement fluid pump tube tract  29 , serve for removably mounting the second module B on the front panel of the dialysis machine. 
     The pre-dilution  25  and post-dilution  26  branches each comprise at least a tract of flexible tube which can be obstructed by squeezing. These tracts of flexible tube are positioned in a prefixed position with respect to the post-pump arterial expansion chamber  12 . The correct positioning of the prefixed position is easily reached when mounting the module B on the front panel of the machine, by virtue of the fact that the fluid connection system formed by the second flexible tube  44  and the third flexible tube  45  are positioned stably with respect to the support element of module B, so that the pre-dilution  25  and post-dilution  26  branches (made from the third flexible tube  45 ) are immobile with respect to the support element of module B, although each of them is elastically deformable and therefore closable by squeezing of the valves  52  and  53 . 
     The branch from the pre-dilution  25  and post-dilution  26  branches which is not fluidly connected to the expansion chamber bearing the replacement fluid pump tube tract  29  can be constrained, directly or via a tract of the extracorporeal blood circuit, to the support element. In the present embodiment, in which the expansion chamber bearing the replacement fluid pump tube tract  29  is the post-pump expansion chamber  12  (which chamber  12  is connected to the pre-dilution branch  25 ), the post-dilution branch  26  can be constrained to the support element via a tract of venous line  7  of the extracorporeal blood circuit. In particular, a tract of venous line  7  is engaged in two recesses afforded in the casing  36 , and the post-dilution branch  26  is fluidly connected to this tract of venous line  7 . 
     The main branch  24  of the supply line  23  is constrained (for example directly, as in the present embodiment) to the support element. In particular the main branch  24  exhibits at least a support zone that interacts (in a gripping and/or direct contact coupling) with the support element in a tract to that is downstream of the ultrafilter  28 . In more detail, a tract of the main branch  24  arranged downstream of the ultrafilter  28  is engaged (by, for example, a removable joint) in a seating afforded on one of the extensions  35 . This tract of the main branch  24  (which in the present embodiment is part of the second flexible tube  44 ) exhibits, at the ends thereof, two annular projections which are axially distanced from one another and which are arranged externally of the opposite ends of the seating  46 , functioning as stable centring and positioning tabs of the tract of main branch  24  in the seating  46 . 
     The ultrafilter  28  is supportedly constrained to the support element of module B, in particular to the casing  36 . 
     The support element can realise at least a mechanical and not fluid interconnection between the expansion chamber bearing the replacement fluid pump tube tract  29  (i.e. the chamber  12 ) and the replacement fluid supply line  23  and/or between the expansion chamber bearing the replacement fluid pump tube tract  29  (chamber  12 ) and the extracorporeal blood circuit. A mechanical and not fluid interconnection can also be operating between the expansion chamber  12  and the venous line  7  (or the post-dilution branch  26  or, respectively, the arterial line  6  (or the pre-dilution branch  25 ). 
     One of these mechanical and not fluid interconnections comprises, in the present embodiment, one of the extensions  35  in the form of an arm that emerges (on the opposite side with respect to the replacement fluid pump tube tract  29 ) from the expansion chamber  12  which bears the replacement fluid pump tube tract. As already mentioned, this arm exhibits at an end thereof an attachment point (seating  46 ) for the main branch  24  of the supply line  23 . As already mentioned, the support element realises both the mechanical and not fluid interconnection between the chamber  12  and the line  23 , and the mechanical and not fluid interconnection between the chamber  12  and the blood circuit. 
     The support element of the second module B comprises, in the present embodiment, two elements which are assembled one to the other, i.e. the extensions  35  (integrated with the chamber  12 ) and the protection casing  36 . However it would be possible, in further embodiments of the invention, to have the support element made in an integrated single piece or an assembly of three or more distinct elements. 
     The second module B comprises an integrated element which defines the expansion chamber supporting the replacement fluid pump tube is tract  29 , i.e. the chamber  12 . This integrated element also defines a part of the support element of the second module B, in particular the extensions  35 . 
     The integrated element further defines a first conduit  39  for blood inlet into the expansion chamber  12 , a second conduit  50  for replacement fluid inlet, and a third conduit  40  for blood outlet (or blood mixed with replacement fluid) from the expansion chamber  12 . 
     The first and third blood conduit  39  and  40  belong to the extracorporeal blood circuit and are located on two opposite sides of the above-described expansion chamber  12  and extend in length in a vertical direction, with reference to an operative configuration in which the pump tube tract  29  is coupled to the replacement fluid circulation pump  30 . 
     The first and third blood conduits  39 ,  40  also each have a bottom end which is fluidly connected to an expansion reservoir  47  of the post-pump arterial expansion chamber  12 , and an upper end which is fluidly connected (via the ports  20  and  22 ) to the rest of the arterial line  6 , respectively before and after the post-pump arterial expansion chamber  12 . In particular the first inlet conduit  39  is connected to an initial part of the arterial blood line  6  having the patient end  9  destined for connection with the arterial vascular access; the third outlet conduit  40  is connected to a final part of the arterial blood line  6  having the device end  13  destined for connection to the hemo(dia)filter  5 . 
     With reference to figures from  7  to  14 , the integrated element defining the chamber  12  is described in greater detail. The chamber  12  comprises the expansion reservoir  47  which is provided with a bottom, a top, at least a first side extending between the bottom and the top, a first access  48  arranged on the first side at a distance from the bottom and top, and a second access  49 . 
     The first conduit  39  terminates in the first access  48 . A second conduit  50  terminates in the first conduit  39  or, as in the present embodiment, in the expansion reservoir  47 . The first conduit  39  and the second conduit  50  terminate in the first access  48  with, respectively, a first flow direction and a is second flow direction which are incident to one another. 
     The first conduit  39  terminates in the first access  48  with a first flow direction having at least a motion component directed towards the bottom. The first flow direction has at least a motion component directed towards a second side of the expansion reservoir  47 ; the second side extends between the bottom and top and is opposite the first side. 
     The second conduit  50  terminates in the expansion reservoir  47  with a second flow direction having at least a motion component directed towards the second side of the expansion reservoir  47 . The second flow direction has at least a motion component directed towards the top. The second flow direction has at least a first motion component that is horizontal and directed towards the inside of the expansion reservoir  47 . 
     The second conduit  50  comprises an intermediate tract  59  having a flow direction provided with at least a second horizontal motion component going in an opposite direction to the first horizontal motion component. The flow direction of the intermediate tract  59  is provided with at least a vertical motion component. 
     The first conduit  39  has a diverging tract  51  with a fluid passage that broadens in the direction of the first access  48 . The diverging tract  51  broadens towards the bottom of the reservoir  47 . The expansion reservoir  47  extends prevalently on a lie plane; the diverging tract  51  enlarges prevalently in a perpendicular direction to the lie plane. The diverging tract  51  terminates at the first access  48 . 
     The first access  48  is elongate and extends in a perpendicular direction to the first side of the reservoir  47 . 
     The second access  49  is arranged on the bottom of the reservoir  47 . The third conduit  40  terminates in the second access  49 . The third conduit  40  extends in length by the side of the second side of the expansion reservoir  47 . 
     The first conduit  39  terminates in the first access  48  with a first flow direction directed towards the second access  49 . The first flow direction has at least a motion component which is direction towards the bottom. 
     The second conduit  50  terminates on the first side of the expansion reservoir  47  below the end of the first conduit  39 . The second conduit  50  terminates either in the first access  48  contiguously below the end of the first conduit  39  (as in the present embodiment), or, in a further embodiment, not illustrated, it terminates in an intermediate access arranged between the first access  48  and the bottom of the reservoir  47 . 
     The expansion reservoir  47  has an upper part, comprised between the first access  48  and the top, having a greater width than a lower part comprised between the bottom and the first access  48 . 
     The first conduit  39  meets the second conduit  50  in a connecting zone, and joins the connecting zone in a position above the second conduit  50 . 
     The first conduit  39  extends lengthwise by the side of the first side of the reservoir  47 . The first conduit  39  is designed to introduce the transported flow (in the present embodiment the arterial blood) into the connecting zone with at least one motion component directed in a downwards direction. The second conduit  50  is designed to introduce the transported flow (in this case the replacement fluid) into the connecting zone with at least a motion component directed upwards. The first conduit  39  and the second conduit  50  are designed so that each of the respective transported flows is introduced into the connecting zone with at least a horizontal motion component directed internally of the expansion reservoir  47 . 
     The first conduit  39  and the second conduit  50  are arranged on a same side (the first side) of the expansion reservoir  47 . The first conduit  39  is situated above the second conduit  50 . 
     The first side of the expansion reservoir  47  has an upper zone with a vertical inclination, and a lower zone with an oblique inclination. The oblique lower zone of the first side is inclined in a direction nearing the second side. This oblique inclination determines a narrowing of the expansion reservoir  47 . The zone of the second side that is facing the oblique zone of the first side is substantially vertically oriented. The first conduit  39  has an upper tract having a substantially vertical longitudinal axis, and a lower tract having an oblique longitudinal axis. The oblique axis is inclined in a direction nearing the second side of the expansion reservoir  47 . The first conduit  39  terminates in the expansion reservoir  47  with an oblique inclination. 
     The first conduit  39  is made in a single piece with the expansion reservoir  47 . The second conduit  50  is made in a single piece with the expansion reservoir  47 . The third conduit  40  is made in a single piece with the expansion reservoir  47 . The chamber  12  is realised by assembly of two half-shells. The two half-shells are obtained by press-forming of a plastic material. 
     The extracorporeal blood line which includes the chamber  12  is, in the present embodiment, the arterial line  6 . The chamber  12  can, however, be associated (alternatively or in addition to the arterial line  6 ) to the venous line  7 . The chamber  12  in this case would be a mixing chamber for replacement fluid (in post-dilution) for degassing and for monitoring pressure, arranged downstream of the hemo(dia)filter; the inlet port  20  would be connected to the hemo(dia) filter  5 , while the outlet port  22  would be connected to the vascular access. 
     During treatment, in which the arterial line  6  and the venous line  7  are connected to the patient, the blood pump  8  is activated, so that the blood is removed from the patient via the arterial line  6 , is sent to the hemo(dia)filter  5 , and is returned to the patient via the venous line  7 . The replacement fluid pump  30  is also activated, so that the dialysis fluid is removed from the on-line port  4  of the machine, is made to pass first through the pump tube tract  29  and then the ultrafilter  28 , and is then sent selectively to the chamber  12  on the arterial line  6  (opening the pre-dilution valve  52  operating on the branch  25  and closing the post-dilution valve  53  operating on the branch  26 ) or to the venous line  7  (valve  52  closed and valve  53  open), or to both (valves  52  and  53  both open). 
     In a case of pre-dilution, the replacement fluid flow enters the expansion reservoir  47  from below, transversally encountering the blood flow that enters the reservoir from above. Both flows are obliquely directed, each with an inlet component into the expansion reservoir  47  which is horizontally directed (with reference to the work position of the chamber  12 ) towards the second side of the expansion reservoir  47 , and a vertical component having an opposite direction to the direction of the flow. The meeting of the two flows causes an effective remixing between the blood and the replacement fluid, so that the mixed liquid (blood and replacement fluid) that exits through the third conduit  40  is homogeneously mixed. 
     The special conformation and arrangement of the chamber  12  enables both an effective remixing of the blood and replacement fluid and an effective degassing of the liquids entering the expansion reservoir  47 , especially the replacement fluid, thus preventing any air bubbles exiting through the third conduit  40 . 
     In the absence of pre-dilution (valve  52  closed), the replacement fluid does not reach the chamber  12 , while the blood enters through the first conduit  39  and exits through the third conduit  40 ; since the first conduit  39  terminates directly facing the inlet of the third conduit  40 , the turbulence created is relatively low, reducing to a minimum the formation of foam and flow resistors, while at the same time enabling separation of the air which may still be present in the blood. 
     Before the treatment is performed the circuit is primed by connecting the patient venous end  16  to the connector  31  and the patient arterial end  9  to a discharge (for example a collection bag or a discharge connected to the exhausted fluid circuit of the dialysis machine). Then the clamp  32  is opened, the valves  52  and  53  are closed, the pump  8  is activated (with the tract  29  not coupled to the pump  30 ) in order to aspirate fluid from the port  4  and to circulate the fluid along the venous line  7 , the blood filter of the hemodiafilter  5 , and the arterial line  6  up to the end  9 . The priming of the post-dilution branch  26  is performed by activating the pump  8 , closing the venous clamp  18  and opening the valve  53  (with the valve  52  closed), while the priming of the pre-dilution branch  25  is done by opening the valve  52  (with the venous clamp  18  and the valve  53  closed). 
     In a further embodiment (not shown) the support element comprises a selector configured to selectively squeeze the flexible tube tracts of the pre-dilution and post-dilution branches. The selector comprises a movable (e.g. rotatable) member mounted on (e.g. rotatably coupled to) the support element. The movable member includes a first end and a second end and can assume at least two configurations. In a first configuration the first end squeezes one of the flexible tube tracts and in a second configuration the second end squeezes the other of the flexible tube tracts. 
     LEGEND 
     
         
         
           
               1 . Hemo(dia)filtration apparatus 
               2 . Fresh dialyser fluid port 
               3 . Exhausted fluid port 
               4 . On-line port 
               5 . Hemo(dia)filter 
               6 . Arterial line 
               7 . Venous line 
               8 . Blood pump 
               9 . Patient arterial end 
               10 . Pre-pump arterial expansion chamber 
               11 . Blood pump tube tract 
               12 . Post-pump arterial expansion chamber 
               13 . Arterial device end 
               14 . Venous device end 
               15 . Venous expansion chamber 
               16 . Venous patient end 
               17 . Arterial clamp 
               18 . Venous clamp 
               19 . Tubular extensions connected to the chamber  10  for attachment of the blood pump tube tract  11   
               20 . Blood inlet port of the post-pump arterial expansion chamber 
               21 . Replacement fluid inlet port of the post-pump arterial expansion chamber  12   
               22 . Outlet port for blood(-replacement fluid) from post-pump arterial expansion chamber  12   
               23 . Replacement fluid supply line 
               24 . Main branch of line  23   
               25 . Pre-dilution branch of line  23   
               26 . Post-dilution branch of line  23   
               27 . Inlet end of line  23   
               28 . Ultrafilter of replacement fluid 
               29 . Replacement fluid pump tube tract 
               30 . Replacement fluid pump 
               31 . Auxiliary connection of line  23  (for priming) 
               32 . Auxiliary connection  31  intercept clamp 
               33 . Intermediate tract of arterial line between the two modules of the hemodiafiltration apparatus 
               34 . Intermediate tract of venous line between the two modules of the hemodiafiltration apparatus 
               35 . Support extensions emerging from the post-pump arterial expansion chamber 
               36 . Casing 
               37 . Mounting extension 
               38 . Tubular extensions for supporting the replacement fluid tube tract 
               39 . First conduit for blood inlet into the post-pump arterial expansion chamber 
               40 . Third blood outlet conduit of the post-pump arterial expansion chamber 
               41 . First flexible tube 
               42 . First tubular connection 
               43 . Second tubular connection 
               44 . Second flexible tube 
               45 . Third flexible tube 
               46 . Seating predisposed on the support element for fixing the main branch  24   
               47 . Expansion reservoir 
               48 . First access of reservoir  47   
               49 . Second access of reservoir  47   
               50 . Second inlet conduit of replacement fluid into the post-pump arterial expansion chamber 
               51 . Diverging tract of the first conduit  39   
               52 . Pre-dilution control valve 
               53 . Post-dilution control valve 
               54 . Connection for service line located at top of expansion reservoir  47   
               55 . Connection for an ultrafilter vent line 
               56 . Connection for the auxiliary line provided with the auxiliary connector  31   
               57 . Connection for an end of the initial tract of replacement fluid line  23  having the inlet  27  at the opposite end 
               58 . Device for detecting pressure in the blood chamber  12   
               59 . Intermediate tract of second conduit  50