Device for mass transfer, and method of production

Abstract

A device for mass transfer between blood and a transfer medium, in particular a gas/gas mixture, includes a chamber through which blood can flow and in which a plurality of mass-permeable hollow fibers of at least one hollow fiber mat, in which the hollow fibers are held at a spacing by way of warp threads, are disposed in the form of a wound or folded hollow fiber package, wherein a transfer medium is able to flow through, and blood is able to flow around, the hollow fibers, and wherein the density of hollow fibers varies locally in the hollow fiber package in the cross-section perpendicular to length of the hollow fibers. Hollow fiber packages and methods of manufacturing thereof are provided in which the hollow fibers are held at a spacing by warp threads, in which the spacing between adjoining hollow fibers is locally increased, in particular compared to a predominantly equidistant spacing between the hollow fibers.

Claims

1. A device for mass transfer between blood and a gas/gas mixture, comprising a chamber configured for flow of blood therethrough and in which hollow fibers which are mass-permeable, are connected by and held at a spacing from one another by warp threads and are disposed in a form of a wound or folded hollow fiber package configured as layers of the hollow fibers which are connected by and held at a spacing from one another by warp threads, and the device being configured so that a transfer medium is able to flow through, and blood is able to flow around, the hollow fibers, wherein density of hollow fibers varies locally in the hollow fiber package within individual cross-sections of the entire hollow fiber package perpendicular to length of the hollow fibers and independently of any varying of area of the cross-sections of the entire hollow fiber package perpendicular to length of the hollow fibers so that the hollow fiber package has at least one region of lower hollow fiber density than another region, and wherein said at least one region of lower hollow fiber density comprises at least one placeholder inserted into the hollow fiber package at least at an axial end of the hollow fiber package and interposed between two mutually adjacent hollow fiber layers of the hollow fiber layers of the hollow fiber package, the placeholder being separate from and not being connected to the hollow fibers of the hollow fiber package by the warp threads.

2. The device according to claim 1, wherein the placeholder has a cross-section larger than the hollow fibers of the two layers.

3. The device according to claim 1, wherein a region having lower hollow fiber density is disposed radially opposite at least one of a blood inlet region and a blood outlet region of the chamber.

4. A device for mass transfer between blood and a gas/gas mixture, comprising a chamber configured for flow of blood therethrough and in which hollow fibers which are mass-permeable, are held at a spacing from one another by warp threads and are disposed in a form of a wound or folded hollow fiber package, and the device being configured so that a transfer medium is able to flow through, and blood is able to flow around, the hollow fibers, wherein density of hollow fibers varies locally in the hollow fiber package within individual cross-sections perpendicular to length of the hollow fibers and independently of area of the cross-sections so that the hollow fiber package has at least one region of lower hollow fiber density than another region, wherein said at least one region of lower hollow fiber density comprises at least one placeholder inserted into the hollow fiber package at least at an axial end of the hollow fiber package and interposed between two mutually adjacent layers of the hollow fibers connected by warp threads, the placeholder being separate from the hollow fibers of the hollow fiber package and wherein at least one of the placeholders is in the form of a mass-permeable hollow fiber that has a diameter that is larger than the majority of the other mass-permeable hollow fibers.

5. The device according to claim 4, wherein the placeholder is not connected to the hollow fibers of the hollow fiber package by the warp threads.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 shows a preferred design of a device according to the invention;

(2) FIG. 2 shows a first embodiment for creating local fiber density reduction;

(3) FIG. 3 shows a second embodiment for creating local fiber density reduction;

(4) FIG. 4 shows a third embodiment for creating local fiber density reduction;

(5) FIG. 5 shows a fourth embodiment for creating local fiber density reduction; and

(6) FIG. 6 shows a sixth embodiment for creating local fiber density reduction.

DETAILED DESCRIPTION OF THE INVENTION

(7) Exemplary embodiments will be described in detail hereafter based on the figures.

(8) FIG. 1 shows a preferred design of a device according to the invention. The housing 1 forms a cylinder having a circular cross-section, comprising an inner chamber 2 in which mass-permeable hollow fibers, which are not shown, are disposed parallel to the axis. At the axial ends, these are supplied with a transfer medium which flows through the hollow fibers, for example a gas or a gas mixture.

(9) The hollow fibers are disposed around the hollow channel-forming core 3, at least one mat made of such hollow fibers having been wound around the core. The core 3 has an opening 4 at the lower end here, which is thus located at the radial interior, with respect to the housing 1. The upper end of the core 3 forms the blood inlet here.

(10) In the direction of the arrows 5, the blood admitted at the upper end of the core initially flows downward through the core, out of the opening 4 into the chamber 2, and there between the hollow fibers in the direction of the blood outlet 6, which is essentially formed in the circumferential direction and is located at the radial exterior, with respect to the housing 1.

(11) If the hollow fiber density is at least substantially constant (viewed in a cross-section perpendicular to the axis A), the flow primarily takes place from the bottom interior to the top exterior. In the lower region, the flow through the radially exterior regions 7, which is to say those located radially opposite the opening 4 serving as an inlet for the blood into the chamber, is thus inferior. At the upper axial end, the same is true of the radially inner regions 8.

(12) The invention ensures that the local reduction in the hollow fiber density in these regions 7 and 8 located opposite the inlet and the outlet causes the flow resistance to be reduced compared to the case in which the fiber density remains consistent across the cross-section. In this way, the flow also increases in the otherwise disadvantaged regions 7 and 8.

(13) FIG. 2 shows a first option for deliberately reducing the fiber density in a desired region. On the left, FIG. 2 shows a hollow fiber package of the prior art, in which a mat comprising equidistantly spaced hollow fibers 9 in several layers L1 to Ln is wound or folded so as to form a package. Viewed across the cross-section perpendicular to the fiber extension, an overall constant fiber density is achieved in the package, at least to the extent that the fiber density is determined in a defined region that is filled entirely by fibers.

(14) In contrast, the right of FIG. 2 shows a design according to the invention of a hollow fiber package in which individual hollow fibers were removed. This can be done in advance, in the non-wound/non-folded fiber mat, or in the finished package, by axially pulling out the desired fibers. The latter has the advantage that the position of the fibers does not have to be determined in advance. In particular, the warp thread loops of removed hollow fibers remain empty in the package.

(15) The fiber package on the right thus includes fiber gaps 10, 11 and 12. In the region in or around these fiber gaps, it can be seen that the fiber density is thus reduced compared to the surrounding region, which is to say the flow resistance is reduced as well, and thus the flow velocity or the volume flow is increased. Such regions having reduced fiber density, which are only schematically shown here to illustrate the core idea of the invention, may be disposed where the flow would be reduced in a conventional fiber package, which is to say having a density that is otherwise the same throughout, which is to say in particular in a respective predetermined axial position opposite a blood inlet or outlet region. With respect to FIG. 1, this would be in regions 7 and 8, for example.

(16) FIG. 3 shows an alternative method for creating local fiber density reduction. A section of a hollow fiber package formed according to the invention, comprising multiple wound or folded layers L1 to L4, is shown.

(17) A placeholder 13 is disposed between the layers L2 and L3 and can either extend across the entire axial length of the hollow fibers or have a shorter length than a respective hollow fiber and may then, for example, be disposed somewhere between the axial ends of the hollow fibers, for example in a region at the axial end.

(18) In this embodiment, the placeholder 13 has a cross-section that is larger than the cross-section of each fiber 9. Free spaces are created in opposing regions 14 of the placeholder 13 where the layers L2 and L3 lift off the placeholder and are brought together again, resulting in the desired density reduction. The placeholder itself can also contribute, through its own volume, to the density reduction, when blood can flow therethrough, for which purposes the placeholder can be designed as a perforated tube. However, the placeholder can also be designed to have a solid cross-section, so that only the regions 14 have a density-reducing effect. According to the above embodiments, however, this placeholder 13 itself can also form a mass-permeable hollow fiber, which participates in the mass transfer.

(19) Such placeholders can be disposed, for example, based on FIG. 1, in the region 8, which is to say at the top and radial interior, and in the region 7, which is to say at the bottom and radial exterior, so as to favor the flow there locally.

(20) If the placeholders are accessible at the axial end in the wound/folded package, these may be removed from the package prior to the fibers being potted. If these remain, they are preferably also surrounded by the potting compound.

(21) FIG. 4 shows one of the options for causing a density reduction by way of the hollow fiber mat. A section of a mat comprising hollow fibers 9 is shown, in which the hollow fibers 9 are all equidistant and are kept at a spacing by warp threads 15. The warp threads achieve stable bonding of the mat here. In this example, one of the hollow fibers has been pulled out of such a mat, by way of example, whereby the empty loop/stitch 16 of the warp threads 15 remains at this site. During winding or folding, this loop causes a reduction in density, as is essentially shown in FIG. 2. It is also possible, of course, for hollow fibers to be removed in several positions, including in consecutive positions, in such a mat.

(22) FIG. 5 illustrates another embodiment according to the invention of a mat of such hollow fibers 9, which are predominantly held at an equidistant spacing A in the mat by the warp threads 15. In contrast, a minority of hollow fibers, and only one hollow fiber 9a in the section here, has an increased spacing in the mat, and in particular an increased spacing with respect to adjoining hollow fibers. This increased spacing B is implemented by an increased spacing between the loop/stitch centers of the warp thread pair of this hollow fiber 9a compared to that of the other hollow fibers 9.

(23) FIG. 6 shows one embodiment in which a minority of hollow fibers, constituted by one mass-permeable hollow fiber 9b in the section here, has a larger diameter than the other hollow fibers 9 constituting the majority of all the hollow fibers in the mat. As a result of being looped by the warp threads 15, this hollow fiber 9b is part of the mat in the same manner as all the other hollow fibers 9. During winding/folding, the desired density reduction is achieved in the surrounding area of the hollow fiber 9a in a manner similar to that described for a placeholder 13 in FIG. 1, with the difference that layers (not shown here), which are placed around the hollow fiber 9b during folding/winding, are not placed on top of one another in laterally opposing positions next to this hollow fiber 9b, but are placed on the hollow fiber 9 to the right and left next to the hollow fiber 9b.