Air separator extracorporeal fluid treatment sets

[0001] The invention relates to an air separator of an extracorporeal fluid therapy kit. The air separator of this invention may for example be used in extracorporeal blood therapy procedures, or in procedures involving extracorporeal dislocation of blood or blood components or medical fluids.

Background of the invention [0002] As a non-limiting example and to provide a background for the present invention, reference is made to the field of extracorporeal blood therapy. As is well known in the art, blood therapy apparatus such as hemodialysis machines are used to remove impurities from the patient's blood continuously. Blood is typically pumped through tubes and moved through arterial and / or venous bubble traps (air separators), connected to disposable sets of tubing connecting the patient's body to a dialyzer or other therapeutic unit mounted on a hemodialysis machine.

[0003] US Patent No. 4,263,808 discloses a one-piece hydraulic circuit that includes arterial and venous alveolar capture chambers in which the blood enters through the entrances above the bottom of the chamber and also exits near the bottom of the chamber. The pressure in these chambers can be determined by transducers placed on impermeable latex membranes covering the openings in communication with the upper parts of the chambers.

[0004] US Patent No. 4,666,598 discloses a fluid flow chamber cassette that can be mounted with its front or rear wall at a support machine, such as a hemodialysis machine, and also has a flexible tube that extends from the side wall and forms a loop, which is symmetrical around the axis of the loop, transverse to the side wall, as a result of which the pump roller on the machine can act on this loop, both when the front wall is pressed against the machine, as and when the back wall is pressed against the machine. The orientation of the cassette and the fluid flow through the cassette can therefore be changed by simply changing the front or rear wall that is mounted on the machine. This cassette contains an arterial and venous chamber. The arterial chamber inlet enters the arterial chamber in a higher position than the arterial chamber outlet, while the venous chamber inlet enters the venous chamber in a higher position than the venous chamber outlet. During priming, by causing reverse flow, fluid rises in the venous and arterial chamber to the inlet entry level, and the amount of air in these chambers remains constant, even after the flow is reversed during normal operation with blood. Each of the arterial and venous chambers has a suitable impervious and flexible diaphragm at the opening in the rigid wall of the chamber to detect pressure. The so-called "bottom entry" chambers, in which the blood inlet port is at the bottom of the chamber and the blood enters the blood space at the bottom or side wall of the chamber, are known from US Patent No. 4,681,606, US Patent No. 4,668,598 and European Patent No. 0058325.

[0005] US Patent No. 5 605 540 discloses a single piece, made of plastic, blow molding, arterial or arteriovenous blood chamber, with an entrance at the bottom, having an inlet and 1

ΕΡ 2 407 191 Β1 outlet at the same height, where both the inlet and outlet have a gradually increasing cross-section as they move from the bottom to the top of the chamber.

[0006] US Patent Application No. US 2004/0186416 discloses a non-tuning blood circulation circuit that is used for single needle dialysis, comprising a blood draining line having an arterial pump and a blood recycling line having a zinc pump. The discharge line contains an arterial expansion chamber located on the line directly above the pump and the return line contains a venous expansion chamber located on the line directly below the pump, the arterial and vein expansion chamber being hydraulically separated from each other and are integrated into one box-like structure with rigid walls. This box-like structure (indicated by reference number 8 in Figure 1 of US 2004/0186416) comprises a first chamber that can receive fluid, the first chamber having a bottom wall, a top wall a side wall extending between the top wall and a bottom wall an inlet port and an outlet port connected to the bottom wall and in fluid communication with the first chamber and the first channel extending along at least part of the side wall and having a first end connected to the inlet port, and the other end. The first channel has a first part extending from the first end. The box-like structure has a filter connected to the bottom wall relative to the outlet port and projecting axially to the first chamber in a direction substantially parallel to the first channel, the latter being parallel to the side wall.

[0007] US Patent 4 061 031 discloses a combination of a flow meter and a blood bubble trolley that has been derived for extracorporeal therapy, especially for dialysis. This combination includes a container divided by a vertical partition wall into a vertically elongated inlet chamber having a blood receiving inlet that is to be measured and treated, and has an outlet chamber with a cross section much larger than the inlet chamber and in fluid communication with the outlet opening . According to US 4 061 031, a narrow corridor with a cross section much smaller than the inlet is passed through the partition wall, preferably near its lower end, causing the fluid level in the longitudinal inlet chamber to rise significantly above that narrow corridor.

[0008] Furthermore, the applicant has in the past introduced air separators to the market as schematically illustrated in the accompanying Figures 7A and 8A.

Summary of the invention [0009] The applicant has found that the structure of blood chambers or medical fluids can be further improved in order to:

- improving air separation to avoid unwanted air bubbles reaching the chamber outlet.

- minimizing foam formation in relation to the blood inlet that could lead to problems during effective air separation, and

- reducing areas of stagnation that could contribute to the formation of clots.

[0010] The above objects are achieved by an air separator according to the appended claims.

[0011] According to one aspect of the present invention, the opening for introducing blood or other fluid into the air separator chamber is relatively distant from the outlet port.

[0012] According to a further feature of this invention, this opening is oriented so as to direct the liquid towards the top of the blood chamber.

ΕΡ2 407 191 Β1 [0013] These features give time to slow down the flow and allow the bubbles to separate from the blood before the latter reaches the outlet port.

[0014] In another aspect of this invention, an (first) inlet channel is used in which the flow velocity is significantly reduced and the flow stability increased, using two or more consecutive parts of a gradually increasing cross-section. This results in a significant reduction in foam formation and contributes to the separation of air bubbles present in the incoming blood.

[0015] According to a further aspect of this invention, the air separator has a filter inside the chamber and the opening is positioned far enough away from the filter's impact area because it is desirable that the bubbles be separated before reaching any zone in which they could be caught and then uncontrolledly released into the patient's body. Furthermore, if the filter is positioned and extends to an area sufficiently distant from the inlet opening of the channel, the presence of stagnation areas corresponding to the filter surface is less likely.

[0016] Further features and benefits will be more readily apparent from the following description in connection with several preferred but non-exclusive embodiments of the air separator of this invention.

Brief description of the drawings [0017] The description will be given with reference to the figures of the attached drawing, shown in the framework of a non-limiting example, in which:

Fig. 1 is a front elevational view of the air separator according to the invention;

Figs. 2 and 3 are side views of the separator of Fig. 1;

Figs. 4 and 5 are top and bottom views of the separator of Fig. 1;

Fig. 6 is a cross-sectional view of the separator according to Fig. 1;

Figures 7A and 7B are schematic vertical views showing respectively blood in a blood chamber of known design and in an air separator;

Figures 8A and 8B are schematic vertical views showing the blood flow velocity system in a blood chamber of known design and in an air separator, respectively;

Fig. 9 is a schematic vertical view showing a separator according to an embodiment of the invention;

Fig. 10 does not illustrate the invention

Fig. 11 is a vertical view showing a blood circuit where the air separator according to Fig. 1 can be used;

Fig-12 is a diagram of the extracorporeal blood circuit with the air separator used in the present invention.

Detailed description [0018] Referring to the attached figures, several non-limiting (embodiments of the air separator 1 according to the invention) are presented there. As a non-limiting example, the detailed description will make references to the use of the air separator to separate air bubbles from blood, as when separator 1 is used in extracorporeal blood therapy kits. This air separator comprises first and second chambers 2 and (see Fig. 6) arranged side by side. Of course, depending on the circumstances, this separator after 3

ΕΡ 2 407 191 Β1 air can only contain the first chamber. The first chamber has a bottom wall 4, a top wall 5 as well as a side wall 6, respectively, extending between the top and bottom walls 4 and 5. Similarly, the second chamber has a bottom wall 7, a top wall 8 and a side wall 9, respectively, extending between upper and lower walls 7 and 8. The side wall in the embodiments shown in the figures of the attached drawing is formed by flat parts: it should be understood, however, that the side wall may be curved. Also, the shape of the upper and lower walls is not limited to the specific shape shown in the figures of the attached drawing.

[0019] The bottom wall of each chamber is provided with respective inlet and outlet ports for fluid entering and leaving the chamber. For the sake of clarity, the inlet and outlet ports 10 and 11 of the first chamber 2 are referred to herein as the first inlet port 10 and the first outlet port 11, while the inlet and outlet ports of the second chamber are referred to herein as the second inlet port 12 and second outlet port 13.

[0020] In all the embodiments illustrated in the figures of the attached drawing, the air separator comprises a first channel 14, running parallel to at least the lateral brine portion 6a 6 of the first chamber 2 and having a first end 14a connected to the first inlet port 10 and a second end 14b , ending in the first chamber at a position closer to said upper wall 5 than said lower wall 4; wherein part 6a is the lower side part of the side wall. The second end 14b of the first channel 14 defines by its end an opening 15 which opens into the chamber and faces the said upper wall. Referring to the operating condition, the plane of Fig. 1 represents a vertical plane, and thus the first channel extends vertically and the end opening is substantially horizontal and faces the top of the air separator.

[0021] In all embodiments, the first channel has a first portion 16 directly connected to the first inlet port 10 and also a second portion 18 defining a cross section of the flow corridor larger than that of the first portion. It should be noted that 3 or more consecutive parts can be envisaged here, in which case also the cross section of the part will increase as it moves away from the inlet port 10. By the definition of "cross-section of a flow corridor" is meant in this document an area effectively available for fluid flow according to a particular cross-section of a fluid channel or fluid chamber.

[0022] Fluid entering the first inlet port moves through the first relatively narrow portion and then through the second relatively wide portion in such a way that the fluid velocity is proportionally reduced when passing from the first to the second portion, before entering chamber 2. [0023] ] In the embodiment according to Figs. 1-6 and in the embodiment according to Fig. 10, the cross-section of the first flow corridor and the cross-section of the second flow corridor are constant and thus define two tubular portions, the effective area of ​​fluid transfer being constant and thus the flow velocity can be stabilized. The alternative embodiment of Fig. 10 has only one chamber: namely, the first chamber. It should be noted, however, that this first chamber according to Fig. 10 it may be connected to the second chamber in a manner similar to the embodiment according to Figs. 1-6.

[0024] In order to better understand the geometry of the air separators according to the invention and by making reference to non-limiting examples according to Figs. 6, 9 and 10, the following definitions are given:

ΕΡ 2 407 191 Β1

- D1 represents the distance between the inner surface of the top wall 5 and the inner surface of the bottom wall 4 (in some cases the top and / or bottom wall may not be flat and parallel: in such cases D1 is the distance between the lowest area of ​​the bottom wall and the top area of ​​the top) .

- D2 represents the distance between the horizontal plane in which the opening of the first channel runs and the bottom wall (in some cases the bottom wall may not be flat and parallel to the level: in such cases, D1 is the distance between the horizontal plane containing the hole and the lowest bottom area )

- A1 represents the dimension of the cross-sectional area of ​​the flow corridor for the first channel 14 respectively for the said opening (with reference to the attached examples, A1 is measured taking into account the horizontal section corresponding to the opening),

- A2 represents the dimension of the cross-sectional area of ​​the flow corridor for the first chamber respectively for the said opening (with reference to the attached examples, A2 is measured taking into account the horizontal cross-section of the first chamber at the same vertical position of the opening),

- A3 represents the cross-sectional area dimension of the flow corridor for the first channel respectively for the first part 16 (with reference to the attached examples, A3 is measured taking into account the horizontal section according to the first part).

[0025] In the embodiment of Figs. 1-6, the first channel includes a connecting portion 17, successively connecting the second portion to the first portion, and also having a gradually increasing cross-section of the flow corridor. In practice, this connecting part can be obtained as a wall part inclined with respect to the longitudinal direction of each of the parts 16 and 18. In the embodiment according to Fig. 10 two further parts 16 and 18 are placed one after the other and behind the aperture according to the area of ​​connection of the two parts. This aperture, together with the above-mentioned opening 15, serves to position the channel 14 in communication with the chamber and gives a preferential path for the fluid coming from the inlet port 10, which does not have sufficient kinetic energy to reach the opening 15. In the embodiments of Figs. 1- 6 and 10, A1 is between 1.5 and 2.5 times A3.

[0026] Fig. 9 shows an alternative embodiment in which the air separator 1 has only one chamber: namely, the first chamber. It should be noted, however, that this first chamber according to the embodiment shown in Fig. 9 can be connected to the second chamber in a similar manner as in the embodiment according to Figs. 1-6. In the embodiment according to Fig. 9, channel 14 has a second portion 18 in which the cross section of the flow corridor increases successively and continuously as it moves toward said second end (i.e., referring to the attached figures, the effective area for fluid passage increases as moving closer and closer to the top wall). According to a possible variant, the embodiment according to Fig. 9, the channel 14 may have a continuously and successively increasing cross-sectional view of the flow corridor from the first to the second end.

Also in the embodiments of Fig. 9, A1 is between 1.5 and 2.5 times the dimension A3.

Returning to the description of the features common to all embodiments, the first channel 14 has a longitudinal course parallel to the side wall of the first chamber in such a way that the opening is positioned in a specific position relative to said upper and lower walls. Using the above definitions, D2 / D1 is above 0.5, for example between 0.55 and 0.7.

ΕΡ 2 407 191 Β1 [0028] Furthermore, the A1 / A2 ratio is above 0.25, which means that the fluid does not pass rapidly from the narrow channel to the large channel, but instead the cross-sectional area of ​​the flow corridor to the corresponding hole is at least 1/4 (in the embodiments shown here about 1/3) of the cross-sectional area of ​​the flow passage of the first chamber to the corresponding opening (i.e. the area of ​​the flow corridor in the first chamber, measured at the same opening height as shown in Fig. 9, see designations A1 and A2). The A1 / A2 ratio as defined above also also has an upper limit below 1.00 and preferably below 0.75, which means that the area of ​​the opening is preferably smaller than the surface area of ​​the first chamber respectively of the same air separator section.

[0029] The air separator may also comprise a filter 19 connected to the bottom wall of the respective outlet port 11 and extending into the chamber in a direction substantially parallel to the first channel part. The filter may have a generally overall cylindrical or frustoconical shape and a screen may be designed as required.

[0030] The filter extends axially into the chamber from the lowest area 4a of the bottom wall 4 and has an overall axial extent leading to the interior of the first chamber (which is referred to as D3 in the figures of the attached drawing) within a reasonable range smaller than D2. According to the embodiment of Fig. 1, the filter has an overall axial range D3 substantially not greater than 0.70 of the D3 value. In the embodiments shown here, the axial length of the filter is less than the axial length of the first portion 16 of the first channel 14 such that the filter 19 remains at a sufficient distance from the opening 15 of the first channel.

[0031] The air separator may also include a second channel 20 (as for example in the embodiment according to Fig. 1 - 6) running parallel to the side wall of the second chamber 3 and having a first end 20a connected to the second inlet port 12 and a second end 20b ending inside the second chamber; wherein the second channel has a constant cross section and has a deflector 21 corresponding to its second end defining the opening 22 facing the side wall 9 of the second chamber. In practice, the flow coming from the second inlet moves through the second channel and (depending on the conditions of use) turns essentially by 90 °, whereby it enters horizontally into the second chamber.

The opening 22 faces the side wall 9 and extends through an area that is below the horizontal plane on which the opening of the first channel lies (again according to the conditions of use of the separator).

[0032] From a structural perspective, the entire air separator according to the embodiments shown here has a flattened configuration in which said first channel and said first chamber have a substantially square cross-section. The separator can be made of a rigid and transparent plastic material. As a non-limiting example, one of the following plastic materials may be used: PETG, PVC; nevertheless, any suitable material for this purpose can of course be used without departing from the scope of this invention, which relates to the geometry of the separator, and not the specific materials used for production.

For example, alternative selection elements for the manufacture of a separator may represent the following materials: copolyester (e.g. Eastar PETG copolyester from Eastman Chemical Company), multi-polymer acrylic based substances (e.g. bearing the Cyrolite® trademark of Cyro Industries), kopo6

ΕΡ 2 407 191 Β1 styrene-butadiene (S / B / S) block limer (e.g. Styrolux® from BASF), MABS (e.g. Terlux® from BASF), styrene-methyl-methacrylate-butadiene polymers (e.g. Zylar® or NAS® from Nova Chemicals).

The whole air separator can be made as one piece, for example by injection molding. More specifically, the first channel 14 and the walls 4, 5, 6 of the first chamber form a single plastic element, where the channel 14 has a side wall having a longitudinal part in common with a side wall part of the first chamber. Similarly, when present, the second blood chamber may be one element with the first blood chamber and has an integral second channel 20.

In the embodiment of Fig. 6, each of the first and second blood chambers has a side wall formed by a front wall, a rear wall spaced from the front wall, and side walls extending between said front and rear walls. The first and second chambers are connected respectively to one common side wall 25, which extends according to the central zone of the air separator; wherein the front and rear walls of each chamber are coplanar and cooperate to define the front and rear walls of the entire air separator. The intermediate wall 23 extends between the front and back walls of each blood chamber and laterally limits the respective channel to one of said side walls. In Fig. 6, the intermediate wall 23, connected to the first blood chamber, has a first wall portion 23a, parallel to one of the side walls, a second wall portion 23b, parallel to the same side wall, and a deflecting portion 23c connecting said first and second parts, thereby forming said first and second parts 16 and 18 as well as part 17. In Fig. 9, the wall 23 has an end curved portion defining a second part 18 of the first channel 14. In Fig. 10 the intermediate wall 23 is defined by two (or more) wall portions 23a and 23b, separated by an aperture 23d.

[0033] The side wall of the first chamber may be designed to contain pressure transducer elements 24. In this case, the first channel terminates immediately below said pressure transducer elements. Also, the second chamber may have suitable pressure transducer elements 24.

Pressure transducer elements may include an opening on the wall of the air separator and a suitable diaphragm tightly plugging the opening. This diaphragm is deformed under the influence of the pressure difference between the inside and outside of each chamber and sends the appropriate pressure signal to a tube connected to a pressure sensor inside the dialysis machine (or other therapeutic machine). US Patent No. 4,666,598 discloses in detail a possible embodiment of pressure transducer elements of the type just described. These pressure transducer elements can also be different from the above-described solution: for example, the diaphragm can be integrally obtained in the sidewall by reducing the wall thickness, defining a movable part integral with the remaining part of the wall. According to another alternative concept, pressure can be detected through appropriate air supply lines to appropriate transducers distant from the air separator. In yet another alternative concept, pressure sensors are used, which are directly integrated on the wall of the separator and directly providing the function of an electric signal for the pressure inside the separator (piezoelectric sensors can be used). However, the way the pressure in the blood chambers is detected is not relevant to the present invention and any alternative elements may be used equivalent.

ΕΡ 2 407 191 Β1 [0034] Fig. 11 discloses an extracorporeal blood circuit 60 in which an air separator 1 of the type shown in Figs. 1-6 is used.

This blood circuit 60 includes an arterial line 70 that has at least one end 71 designed to be connected to the patient's body, and the other end 72 designed to be connected to the blood therapy unit, and a venous line 73, which has at least one end 74, designed to be connected to the patient's body, and another end 75, designed to be connected to the blood therapy unit.

The air separator according to the present invention is connected to the venous and arterial line as described in detail in this document below.

Venous line 73 comprises a first flexible tube 79 having one end connected to the inlet port 10 of the first blood chamber 2, and an opposite end 75 where a connector may be present. The venous line also includes a second flexible tube 80 having one end coupled to the outlet port 11 of the first blood chamber, as well as the other end, which has already been designated by reference numeral 74, in connection with the patient's body (via an access device that does not is shown in the attached figures of the drawing). Arterial line 70 includes a third flexible tube 81 coupled to the second blood inlet port 12 and ending at said end 71, respectively. The arterial line also includes a fourth flexible tube 82 coupled to the second blood chamber outlet port 13 and with one wall of said second chamber blood to form a loop 83 that is symmetrical about the axis of the loop, transversely to the side wall of the second chamber. In the embodiment according to Fig. 4 the tube 82 connects the outlet port 13 to the rigid channel 84 extending above the chambers 2 and 3, which then leads to the fifth flexible tube 85 ending at end 72, respectively, where a connector may be present. [0035] Of course, depending on the therapy, the blood circuit may also be provided with one or more infusion lines that may be branched to any of tubes 79 and / or 80 and / or 81 and / or 85.

[0036] In use, tubular extensions 86 engaging the tube 82 together with one or more projections 87 are used to lock in the operative position of the air separator to the therapy machine panel. The looping tube 82 fits around the peristaltic pump rollers (not shown) supported on the front of the machine, and fluid (blood or other fluid) can be pumped into the blood circuit. Of course, depending on the fluid to be pumped and the procedure to be implemented, correct connections must be made to the patient's body and to the therapeutic unit, as is already well known in the art.

The described tubing can be made of any plastic material suitable for medical applications, such as single-layer tubing made of plasticized PVC (DEHP, or DEHP-free alternatives as a plasticizer); multilayer pipes containing an outer layer of plasticized PVC (DEHP, or DEHP-free alternatives as a plasticizer), or chlorine-free polymeric materials (e.g. thermoplastic elastomeric polyurethanes, SEBS or compounds based on SEPS) and containing an inner layer of polymer material obtained from a combination of at least a polyolefin selected from the group of polyethylene or polypropylene and at least one elastomer selected from the group formed by SEPS or SEBS. Fig. 12 schematically shows the fluid flow circuit defined by the blood circuit and the air separator according to Fig. 11 when they are connected to the blood therapy unit 76 in the blood therapy machine.

This blood therapy unit may for example be formed by a housing having a half-passage 8 in it

ΕΡ 2 407 191 Β1 a separable membrane separating the blood chamber and the therapeutic fluid chamber. The blood chamber in unit 76 is connected to terminals 72 and 75 of the arterial and venous line.

The therapeutic fluid chamber is in use connected to the outlet line 77 for spent therapeutic fluid and also to the inlet line 78 for fresh therapeutic fluid, prepared by a blood therapy machine or from appropriate containers. Of course, for therapies where no fresh fluid is required, the therapeutic fluid chamber is connected only to outlet line 77.

Depending on the blood therapy to be performed, the blood circuit may be connected to appropriate connectors leading to the blood chamber of a dialyzer, hemofilter, plasmofilter, ultrafilter, hemodiafilter or other therapeutic unit.

[0037] During therapy or during other procedures (such as prime or rinsing), fluid is pumped into the first blood chamber via tube 79, channel 14 directs fluid toward the upper wall of the air separator, and contributes to evenly reducing flow velocity because the channel is relatively long compared to the vertical chamber and relatively wide in relation to the opening. Thus, the fluid leaves the channel in a position in which it is sufficiently distant from the outlet port; moreover, the direction of flow, reduction of speed and uniform flow allow very efficient bubble evacuation without foam formation and with minimal disturbance in the air-blood contact (see Fig. 7B). The comparison of Fig. 7A and 7B, it being easily seen how the air separator according to the invention provides a significant reduction of disturbances and contributes to a more stable fluid level. Moreover, the distance of the opening 15 from the outlet port 11, the geometry of the first channel and the first chamber, a well as the special location of the filter, result in a filter surface that does not show stagnation areas, and thus reduces the risk of clots or entrapment. FIG. 8A and 8B emphasize the improvement offered by the present invention because the entire surface of the filter 19 is penetrated by a fluid having a specific, sufficiently high speed. In contrast, the prior art chamber filter of Fig. 8A has an upper fluid stagnation area.