Membrane for an oxygenator for gas exchange in the bloodstream, oxygenator having such a membrane, and method for producing such a membrane

Abstract

The invention relates to an oxygenator for gas exchange in the bloodstream, comprising a housing, a first interior chamber for blood arranged in the housing, a second interior chamber for gas arranged in the housing, and a membrane separating the interior chambers. According to the invention, the membrane has a silicone layer and a reinforcing structure reinforcing the silicone layer.

Claims

1. A membrane for an oxygenator for gas exchange in a blood-circulation system, the membrane comprising: a silicone layer and a reinforcing structure which reinforces the silicone layer, wherein the membrane is impermeable to liquid, but permeable to gas, wherein the silicone layer comprises silicone rubber, wherein the silicone layer is free from cavities, wherein the reinforcing structure comprises polyether sulfone (PES), wherein the reinforcing structure comprises reinforcing elements and intervening spaces, wherein the totality of the intervening spaces forms an area available for flow through the reinforcing structure, wherein a proportion through said area in the reinforcing structure is at least 90% of a total area of the reinforcing structure; wherein a thickness of the silicone layer is smaller than a thickness of the reinforcing structure.

2. The membrane as claimed in claim 1, wherein the reinforcing structure is a network.

3. The membrane as claimed in claim 1, wherein the reinforcing structure is embedded in the silicone layer.

4. The membrane as claimed in claim 3, wherein the reinforcing structure is embedded in one side of the silicone layer.

5. The membrane as claimed in claim 4, wherein the reinforcing structure is embedded only in one side of the silicone layer.

6. The membrane as claimed in claim 1, wherein a thickness (D.sub.V) of the reinforcing structure is, at most, 0.4 mm.

7. The membrane as claimed in claim 6, wherein the thickness of the reinforcing structure is, at most, 0.35 mm.

8. The membrane as claimed in claim 7, wherein the thickness of the reinforcing structure is, at most, 0.3 mm.

9. The membrane as claimed in claim 1, wherein a thickness (D.sub.S) of the silicone layer is from 0.03 mm to 0.5 mm.

10. The membrane as claimed in claim 9, wherein the thickness of the silicone layer is from 0.05 mm to 0.4 mm.

11. The membrane as claimed in claim 9, wherein the thickness of the silicone layer is from 0.1 mm to 0.3 mm.

12. The membrane as claimed in claim 1, wherein a thickness (D.sub.M) of the membrane is from 0.35 mm to 0.6 mm.

13. The membrane as claimed in claim 12, wherein the thickness of the membrane is from 0.4 mm to 0.5 mm.

14. The membrane as claimed in claim 12, wherein the thickness of the membrane is about 0.45 mm.

15. The membrane as claimed in claim 1, wherein the silicone layer is free from cavities.

16. The membrane as claimed in claim 1, wherein the reinforcing elements are at least one of reinforcing filaments and reinforcing fibers.

17. An oxygenator for gas exchange in a blood-circulation system comprising a housing; a first internal chamber for blood arranged in the housing; a second internal chamber for gas arranged in the housing; and at least one membrane comprising a silicone layer and a reinforcing structure which reinforces the silicone layer, wherein the membrane is impermeable to liquid but permeable to gas, wherein the silicone layer comprises silicone rubber, wherein the silicone layer is free from cavities, wherein the reinforcing structure comprises polyether sulfone (PES), wherein the reinforcing structure comprises reinforcing elements and intervening spaces, wherein the totality of the intervening spaces forms an area available for flow through the reinforcing structure, wherein a proportion through said area in the reinforcing structure is at least 90% of a total area of the reinforcing structure, and wherein the at least one membrane separates the first internal chamber from the second internal chamber, wherein a thickness of the silicone layer is smaller than a thickness of the reinforcing structure.

18. The oxygenator as claimed in claim 17, further comprising an exterior hollow cylinder made of a first membrane of the at least one membrane and an interior hollow cylinder arranged in the exterior hollow cylinder and made of a second membrane of the at least one membrane, wherein the first internal chamber is delimited by an internal side of the exterior hollow cylinder and by an external side of the interior hollow cylinder, wherein the second internal chamber is delimited by the interior hollow cylinder, and wherein a third internal chamber is provided which is delimited by an internal side of the housing and by an external side of the exterior hollow cylinder.

19. The oxygenator as claimed in claim 17, further comprising a first membrane and a second membrane which are respectively arranged spirally with respect to a longitudinal axis of the housing, wherein the first internal chamber is delimited by the first membrane and by the second membrane.

20. The oxygenator as claimed in claim 19, wherein the first membrane and the second membrane are retained on a core.

21. The oxygenator as claimed in claim 20, wherein the first membrane and the second membrane are retained on a core which is arranged concentrically with respect to a longitudinal axis of the housing.

22. The oxygenator as claimed in claim 17, wherein the membrane comprises a meandering structure in a plane perpendicular to a longitudinal axis of the housing, wherein the meandering structure comprises a plurality of layers oriented parallel to one another, wherein two adjacent layers of the plurality of layers are undivided and interconnected by a U-shaped deflection section, and wherein the first internal chamber is delimited by two adjacent layers of the meandering structure of the membrane, and wherein the second internal chamber is arranged adjacent to the first internal chamber.

23. A process for the production of a membrane for an oxygenator for gas exchange in a blood-circulation system, comprising the following steps: providing a silicone layer and a reinforcing structure; using a silicone dispersion to embed the reinforcing structure in the silicone layer; and crosslinking the silicone dispersion to give a homogeneous silicone layer into which the reinforcing structure has been embedded such that the membrane is impermeable to liquid but permeable to gas, wherein the silicone layer comprises silicone rubber, wherein the silicone layer is free from cavities, wherein the reinforcing structure comprises polyether sulfone (PES), wherein the reinforcing structure comprises reinforcing elements and intervening spaces, wherein the totality of the intervening spaces forms an area available for flow through the reinforcing structure, wherein a proportion through said area in the reinforcing structure is at least 90% of a total area of the reinforcing structure, wherein a thickness of the silicone layer is smaller than a thickness of the reinforcing structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a view from one side of a membrane of the invention,

(2) FIG. 2 is a sectional depiction corresponding to section line II-II in FIG. 1,

(3) FIG. 3 is an embodiment of an oxygenator with a membrane of the invention,

(4) FIG. 4 is a cross-sectional depiction corresponding to the section line IV-IV in FIG. 3,

(5) FIG. 5 is a view, corresponding to FIG. 4, of another embodiment of an oxygenator with helical membranes, and

(6) FIG. 6 is a view, corresponding to FIG. 4, of another embodiment of an oxygenator with membrane arranged in loops.

(7) A membrane 1 depicted in FIG. 1 and FIG. 2 comprises a homogeneous, cavity-free silicone layer 2 and a reinforcing structure 3 which reinforces the silicone layer 2.

DESCRIPTION OF AT LEAST ONE PREFERRED EMBODIMENT

(8) The silicone layer 2 consists in particular of silicone rubber. The silicone layer 2 provides, to the membrane 1, semipermeability needed for the use in an oxygenator. The membrane is impermeable to liquid, in particular impermeable to blood. The membrane 1 is permeable to gas, in particular permeable to oxygen (O.sub.2) and/or carbon dioxide (CO.sub.2). The silicone material used has good compatibility with blood.

(9) The silicone layer 2 extends mainly in two dimensions. The expression “extends mainly in two dimensions” means that the length and width of the silicone layer 2 are markedly greater than the thickness D.sub.S of the silicone layer 2. The thickness D.sub.S in the embodiment shown is 0.2 mm. The thickness D.sub.S is advantageously from 0.1 mm to 0.3 mm. In particular, the thickness D.sub.S can be selected to be no greater than the range of thickness D.sub.V of the reinforcing structure 3.

(10) In the embodiment shown, the reinforcing structure 3 has been embedded into the silicone layer 2 on one side. The reinforcing structure 3 has therefore been embedded into the silicone layer 2 on one side which is in particular the underside in FIG. 2. The silicone layer 2 covers the underside of the reinforcing structure 3. On an upper side opposite to the underside, the reinforcing structure 3 has at least some uncovered sections.

(11) It is also possible that the reinforcing structure has been embedded completely in the silicone layer 2. In the case of complete embedment, the silicone layer 2 completely surrounds the reinforcing structure 3. The arrangement then has the reinforcing structure 3 protected completely within the silicone layer 2, in particular with respect to the effects of the exterior environment. Direct contact of the reinforcing structure 3 with the gas and/or the blood in the oxygenator is prevented.

(12) In this case, i.e. in the case of complete embedment of the reinforcing structure 3, it is unimportant whether the reinforcing structure 3 has been produced from a biocompatible material. In the embodiment shown, the reinforcing structure 3 has been produced from biocompatible polyether sulfone (PES). The use of a biocompatible material for the reinforcing structure 3 is advantageous when damage occurs to the silicone layer 2 and the reinforcing structure 3 therefore comes directly into contact with the blood.

(13) The reinforcing structure 3 takes the form of a network. The reinforcing structure 3 extends mainly in two dimensions. The reinforcing structure has longitudinal elements 4 and transverse elements 5. The longitudinal elements 4 and the transverse elements 5 have mutual interconnection. The longitudinal elements 4 and the transverse elements 5 respectively take the form of reinforcing filaments or reinforcing fibers which have been joined to one another. The reinforcing structure is intrinsically stable, i.e. has intrinsic rigidity.

(14) In the embodiment shown, the thickness D.sub.V of the reinforcing structure is about 0.2 mm. D.sub.V is advantageously at most 0.4 mm, in particular 0.25 mm and in particular 0.3 mm.

(15) The longitudinal elements 4 and the transverse elements 5 form a square grid with mesh width m.sub.L, in longitudinal direction and mesh width m.sub.B in transverse direction. In the embodiment shown m.sub.L, =m.sub.B. The mesh widths m.sub.L and m.sub.B can also be different. The mesh widths m.sub.L and m.sub.B are typically from 0.5 mm to 5 mm. It is also possible that the longitudinal elements 4 and the transverse elements 5 do not have orthogonal orientation with respect to one another.

(16) Between the longitudinal elements 4 and the transverse elements 5 of the reinforcing structure 3, the arrangement has intervening spaces 6. The thickness D.sub.V of the reinforcing structure, i.e. the thicknesses of the longitudinal elements 4 and of the transverse elements 5, has been selected in such a way that the mesh widths m.sub.L and m.sub.B are greater than the thicknesses of the longitudinal elements 4 and of the transverse elements 5. In particular, the mesh width m.sub.L in longitudinal direction is at least five times the thickness of the transverse elements 5 and in particular at least eight times, in particular ten times. The mesh width m.sub.B in transverse direction is at least five times the thickness of the longitudinal elements 4, in particular at least eight times, and in particular at least ten times. The totality of the intervening spaces 6 forms an area available for flow through the reinforcing structure 3. The area available for flow is in particular at least 90% of the total area of the reinforcing structure 3. The total area of the reinforcing structure 3 is in particular the same as the total area of the membrane 1. The total area of the membrane 1 in the direction of flow is defined via the length L of the membrane 1 and the width B of the membrane 1. The direction of flow is the direction of thickness of the membrane 1. In the embodiment shown, where the membrane 1 is rectangular, the total area is the product of length L and width B. The depiction of the membrane 1 in FIGS. 1 and 2 is not to scale. In particular, for reasons of clarity the reinforcing structure 3, in particular the longitudinal elements 4 and the transverse elements 5, are depicted enlarged, i.e. depicted with enlarged thickness. In reality it is also possible that the reinforcing structure has reduced thickness D.sub.V.

(17) The thickness D.sub.M of the membrane 1 is from 0.35 mm to 0.6 mm. The thickness D.sub.M in the embodiment shown is about 0.45 mm.

(18) A process for the production of the membrane 1 is explained in more detail below. The reinforcing structure 3 is first provided. In particular, the reinforcing structure 3 is placed on a non-adhering underlay. A non-adhering underlay by way of example has a surface made of polytetrafluoroethylene (PTFE). It is also possible that the entire underlay has been produced from PTFE. A silicone dispersion is used for embedment of the reinforcing structure 3. The viscosity of the silicone dispersion is 80 mPas. The aim is to form a silicone layer that is as thin as possible. A silicone dispersion with lower viscosity can form a thinner silicone layer. The viscosity of the silicone dispersion is in particular at most 200 mPas, in particular at most 100 mPas.

(19) After the embedment procedure, the silicone dispersion crosslinks to give the silicone layer 2. The silicone dispersion crosslinks within a period of about 3 to 4 hours at a temperature of 50° C. It is possible to provide a higher crosslinking temperature. The crosslinking time is then reduced.

(20) There can be a drying step provided, in addition to the crosslinking. The drying can take place during and/or after the crosslinking.

(21) The process for the production of the membrane 1 is in particular environmentally friendly. Microporosity, which by way of example in the case of other membrane materials has to be generated separately, is inherently present. The additional production step for generating microporosity can be omitted.

(22) An embodiment of an oxygenator 7 shown in FIGS. 3 and 4 serves for gas exchange in the human blood-circulation system. The oxygenator 7 comprises a housing 8, a first internal chamber 9 intended for blood and arranged in the housing 8, a second internal chamber 10 intended for gas and arranged in the housing 8, and a third internal chamber 11 intended for gas and arranged in the housing 8. A first membrane separates the first internal chamber 9 from the second internal chamber 10. To this end, the first membrane, which initially has the structure in FIGS. 1 and 2 extending in two dimensions, is subjected to curvature and in particular adhesive-bonded to give an interior hollow cylinder 13. There is moreover a second membrane provided, which analogously has been subjected to curvature and adhesive-bonded to give an exterior hollow cylinder 12.

(23) The housing 8 is hollow-cylindrical, and has a longitudinal axis 14. The arrangement has the interior hollow cylinder 13 within the exterior hollow cylinder 12. The interior hollow cylinder 13 and the exterior hollow cylinder 12 are arranged concentrically with respect to the longitudinal axis 14 in the housing 8. The first internal chamber 9 is delimited in radial direction in relation to the longitudinal axis 14 by the interior hollow cylinder 13 and the exterior hollow cylinder 12. The first internal chamber 9 is delimited in radial direction by an internal side of the exterior hollow cylinder 12 and an external side of the interior hollow cylinder 13.

(24) The first internal chamber 9 is delimited in axial direction of the longitudinal axis 14 by an end cover 15. The first internal chamber 9 can be connected to connecting lines by way of blood ports 16. The blood ports 16 in particular have a Luer-lock connection. The arrangement has a blood port 16 on each cover 15. Blood can flow from one of the blood ports 16 through the first internal chamber, i.e. in essence along the longitudinal axis 14, to the respective other blood port 16.

(25) The second internal chamber 10 is delimited in radial direction by the interior hollow cylinder 13. The second internal chamber 10 has a circular area oriented perpendicularly to the longitudinal axis 14. The first internal chamber 9 and the third internal chamber 11 respectively have an annular cross-sectional area perpendicularly to the longitudinal axis 14. The second internal chamber 10 is delimited by the cover 15 in axial direction. The second internal chamber 10 can be connected to connecting lines by way of gas ports 17 arranged respectively on the cover 15. The gas ports 17 have a Luer connection at which there is in particular a Luer-lock barrier. It is essential that port elements of the blood ports 16 and of the gas ports 17 are different, so that unintended connection of a blood connecting line to the gas port 17 or of a gas connecting line to the blood port 16 is reliably prevented. A difference can also be ensured in that the blood port 16 has a screw-threaded male component for connection to a corresponding female component. In this case, the gas ports 17 are not screw-threaded. Incorrect use of the oxygenator 7 is prevented.

(26) The third internal chamber 11 is delimited in radial direction by an external side of the exterior hollow cylinder 12 and an internal side of the housing 8. The third internal chamber 11 is delimited in axial direction by the cover 15. The third internal chamber 11 can be connected to connecting lines by means of gas ports 17, which in particular are the same as the gas ports 17 of the second internal chamber 10.

(27) The housing 8 can also have two housing halves irreleasably connected to one another, for example by adhesive bonding or embedment. Two housing halves are typically separated by a plane oriented in accordance with the section line IV-IV in FIG. 3. The orientation of a plane of separation is therefore perpendicular to the longitudinal axis 14. The oxygenator 7 ensures that there is direct contact between blood in the first internal chamber 9 and oxygen or carbon dioxide in the second and third internal chamber 10 and 11. The oxygenator 7 has a reduced size. The length L.sub.O of the oxygenator along the longitudinal axis 14 is 36 mm in the embodiment shown. The length L.sub.O of the oxygenator 7 is in particular the same as the width B of the membrane 1. The diameter D.sub.13 of the interior hollow cylinder 13 is 21 mm in the embodiment shown. The diameter D.sub.12 of the exterior hollow cylinder 12 is 27 mm in the embodiment shown.

(28) The oxygenator 7 is in particular operated in that blood flows through the first internal chamber 9 along a blood flow direction 18. The blood flow direction 18 in FIG. 3 is from left to right. Oxygen and carbon dioxide flow through the second internal chamber 10 or the third internal chamber 11 along a gas flow direction 19. The gas flow direction 19 is opposite to the blood flow direction 18. The gas flow direction 19 and the blood flow direction 18 are antiparallel. The gas flow direction in FIG. 3 is from right to left.

(29) The process for the production of the oxygenator 7 is explained in more detail below. The first membrane is first subjected to curvature and adhesive-bonded to give the exterior hollow cylinder 12. The length L of the membrane 1 here in essence forms the circumference of the exterior hollow cylinder 12. The interior hollow cylinder 13 is then formed by subjecting the second membrane to curvature and adhesive-bonding. The interior hollow cylinder 13 is arranged concentrically with respect to the exterior hollow cylinder 12. The two hollow cylinders 12 and 13 are then joined irreleasably to the housing 8. This can be achieved by way of example in that the hollow-cylindrical housing 8 is bonded, in particular adhesive-bonded, to one of the end covers 15. The hollow cylinders 12 and 13 are then introduced into the housing 8 and the ends of these are bonded to the cover 15. This bonding is achieved by either embedment or adhesive bonding. In particular, the material used for the embedment of the hollow cylinders 12 and 13 is the same as that used for the adhesive-bonding of the hollow cylinders 12 and 13. The second end cover 15 can then be placed onto the housing 8 and bonded to the housing 8 and to hollow cylinders 12 and 13.

(30) FIG. 5 shows another embodiment of an oxygenator 20. Components corresponding to those already explained above with reference to FIGS. 1 to 4 bear the same reference numbers, and detailed discussion of these is not repeated.

(31) The essential difference of the oxygenator 20 in comparison with the previous embodiment is that the first membrane 1 and the second membrane 21 are arranged spirally with respect to the longitudinal axis 14. A first end of, respectively, the first membrane 1 and the second membrane 21 has been secured on a core 22. The core 22 is arranged concentrically with respect to the longitudinal axis 14 in the housing 8. The respective opposite ends of the membranes 1 and 21 have been secured on an internal side of the housing 8.

(32) Because of the helical arrangement of the membranes 1 and 21, the first internal chamber 23 is helical. The second internal chamber 24 is likewise helical. There is no third internal chamber provided in the oxygenator 20. Simply for reasons of clarity, the first internal chamber 23 has been depicted with cross-hatching in the embodiment shown. It is clear that the first internal chamber 23 is hollow.

(33) The oxygenator 20 has a blood port and a gas port on respective end covers.

(34) FIG. 6 shows another embodiment of an oxygenator 25. Components corresponding to those already explained above with reference to FIGS. 1 to 5 bear the same reference numbers, and detailed discussion of these is not repeated.

(35) The essential difference in comparison with the previous embodiments is that there is precisely one membrane 1 provided. The membrane is arranged in loops in the housing 26. FIG. 6 depicts the meandering structure in the sectional plane. Layers 27 of the meandering structure are therefore oriented respectively parallel to the longitudinal axis 14 of the oxygenator 25. The layers 27 are in particular orientated parallel to one another. Two parallel, adjacent layers 27 are undivided and interconnected by way of a U-shaped deflected section 28. The deflector units 28 are in particular respectively securely connected at an external end to an internal end of the housing 26. The membrane 1 respectively separates a first internal chamber 29 from an adjacent second internal chamber 30. In the embodiment shown there are three first internal chambers 29 and three second internal chambers 30, with an alternating stacked arrangement of the internal chambers 29 and 30.

(36) At the respective deflector units 28 there are first rollers 31 and second rollers 32 provided. The first rollers 31 are respectively arranged within the first internal chamber 29. The first rollers 31 ensure that adjacent layers 27 are arranged at a defined distance from one another. The defined distance between the adjacent layers 27 is prescribed by the diameter of the first rollers 31. The first roller 31 has a first diameter d.sub.1. The first diameter d.sub.1 is at most 3 mm, in particular at most 2.5 mm.

(37) Correspondingly, the second roller 32 has a second diameter d.sub.2. The second diameter d.sub.2 is smaller than the first diameter d.sub.1. In particular, the second diameter d.sub.2 is less than 2.5 mm, in particular less than 2 mm and in particular less than 1.5 mm.

(38) The shape of the housing 26 is rectangular. The length of the oxygenator 25 perpendicularly to the plane of the drawing of FIG. 6, i.e. along the longitudinal axis 14, is about 15 cm. The oxygenator 25 with the membrane 1 of the invention can provide improved gas exchange because of its compact and multilayered design.