U.S. patent application number 10/204181 was filed with the patent office on 2003-08-21 for filter device, preferably a hollow fibre dialyser, comprising curled hollow fibres.
Invention is credited to Fritzsche, Steffen, Heilmann, Klaus.
Application Number | 20030155294 10/204181 |
Document ID | / |
Family ID | 7631359 |
Filed Date | 2003-08-21 |
United States Patent
Application |
20030155294 |
Kind Code |
A1 |
Heilmann, Klaus ; et
al. |
August 21, 2003 |
Filter device, preferably a hollow fibre dialyser, comprising
curled hollow fibres
Abstract
The invention relates to a filter device, preferably for
hemodialysis, that consists of a cylindrical filter housing and a
bundle of curled hollow fibers. The bundle is arranged in the
filter housing. According to the invention, the curled hollow
fibers are provided with an essentially sinusoidal texture and a
wavelength that is defined by means of certain limits. The
invention also relates to a curled hollow fiber and a method for
filling a hollow fiber dialyser.
Inventors: |
Heilmann, Klaus; (Wendel,
DE) ; Fritzsche, Steffen; (Aalen, DE) |
Correspondence
Address: |
Glen K Beaton
Suite 4100
1801 California Street
Denver
CO
80202
US
|
Family ID: |
7631359 |
Appl. No.: |
10/204181 |
Filed: |
February 3, 2003 |
PCT Filed: |
February 16, 2001 |
PCT NO: |
PCT/EP01/01752 |
Current U.S.
Class: |
210/500.23 ;
210/321.78; 210/321.79 |
Current CPC
Class: |
B01D 63/02 20130101;
B01D 2313/08 20130101; B01D 69/084 20130101; B01D 65/00 20130101;
B01D 63/021 20130101; B01D 61/28 20130101; B01D 69/00 20130101;
B01D 69/08 20130101 |
Class at
Publication: |
210/500.23 ;
210/321.78; 210/321.79 |
International
Class: |
B01D 063/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 2000 |
DE |
10007327.1 |
Claims
What is claimed is:
1. Filter device, preferably a hollow fiber dialyser for
hemodialysis, consisting of a cylindrical filter housing and a
bundle of curled hollow fibers arranged in it, characterized in
that the hollow fibers have an essentially sinusoidal texture and
are curled according to the following geometric pattern: 7 5 d <
< L 12 1 1 + 2 D L , ( 1 ) whereby .lambda. represents the
wavelength of the curled hollow fiber, d represents the outer
diameter of the hollow fiber, L represents the effective length of
the hollow fiber, and D represents the diameter of the fiber
bundle.
2. Filter device according to claim 1, characterized in that
amplitude a of the essentially sinusoidal curling results from the
following equation: 8 d 5 < a < 5 . ( 2 )
3. Filter device according to claims 1 or 2, characterized in that
the curling of the hollow fiber has a three-dimensional position
according to the following formula: 9 x ( z ) = ( a sin ( 2 z u )
sin ( 2 z ) a cos ( 2 z u ) sin ( 2 z ) z ) , ( 3 ) whereby the
following is true: 0.05<u<0.14, and whereby {overscore
(.chi.)}(z) represents the space vector between the coordinate
origin and the spatial position of a hollow fiber that extends
along the z-axis, and u represents the amount of rotations per
wavelength .lambda..
4. Filter device according to one of the claims 1 to 3,
characterized in that the fiber allocation in the cylindrical
filter housing is 60.5% to 70%.
5. Filter device according to one of the claims 1 to 4,
characterized in that the fiber allocation in the cylindrical
filter housing is 60.5% to 67.5%.
6. Filter device according to one of the claims 1 to 5,
characterized in that the fiber allocation in the cylindrical
filter housing is between 63.5% and 65.5%.
7. Filter device according to one of the claims 1 to 6,
characterized in that at least 10% of the hollow fibers are
three-dimensional curled hollow fibers.
8. Curled hollow fiber for optional use in the shape of a bundle in
filter devices, preferably hollow fiber dialysers, which may have
various diameters D, from a minimum diameter D.sub.MIN up to a
maximum diameter D.sub.MAX, characterized in that the curled hollow
fiber has only one curl for the use in filter housings of various
diameters, resulting from the following equations: 10 5 d < <
L 12 1 1 + 2 DMax L , ( 4 ) whereby .lambda. represents the
wavelength of the curled hollow fiber, d represents the outer
diameter of the hollow fiber, L represents the effective length of
the hollow fibers, and D.sub.MAX represents the diameter of the
fiber bundle for the fiber housing with the maximum interior
diameter.
9. Curled hollow fiber according to claim 8, characterized in that
the curling of the hollow fiber has a three-dimensional position
according to the following formula: 11 x ( z ) = ( a sin ( 2 z u )
sin ( 2 z ) a cos ( 2 z u ) sin ( 2 z ) z ) , ( 3 ) whereby the
following is true: 0.05<u<0.14, and whereby {overscore
(.chi.)}(z) represents the space vector between the coordinate
origin and the spatial position of a hollow fiber that extends
along the z-axis, and u represents the amount of rotations per
wavelength .lambda..
10. Curled hollow fiber according to claims 8 or 9, characterized
in that it consists of 90 to 99 weight percent of a hydrophobic
first polymer, and 10 to 1 weight percent of a hydrophilic second
polymer, whereby the hydrophobic first polymers are selected from
the following group: polyarylsulfons, polycarbonates, polyamides,
polyvinyl chlorides, modified acrylic acid, polyether,
polyurethane, or their co-polymers, and whereby the hydrophilic
second polymers are selected from the following group:
polyvinylpyrrolidon, polyethylene glycol, polyglycolmonoesther,
co-polymers from polyethylene glycol with polypropylenglycol, water
soluble derivatives of cellulose or polysorbates.
11. Method for the filling of a filter device, especially a hollow
fiber dialyser, according to one of the claims 1 to 7,
characterized in that the air present at the beginning of the
filling operation in the exterior space, i.e., in the space
surrounding the hollow fibers, is displaced by means of a fluid
volume flow that is guided from top to bottom through the filter
housing.
12. Method according to claim 11, characterized in that the fluid
volume flow is approximately 500 ml/min.
13. Use of a filter device according to one of the claims 1 to 7
for the filling of the filter housing by means of a fluid volume
flow that is guided from top to bottom through the filter housing.
Description
FIELD OF THE INVENTION
[0001] The invention relates to filter devices, and more
particularly to hollow fiber dialysers for hemodialysis having an
essentially sinusoidal texture and curled geometric pattern.
BACKGROUND OF THE INVENTION
[0002] Hollow fiber dialysers of a common design have a cylindrical
fiber bundle that is arranged in a cylindrical filter housing.
Blood flows through the inside of the fibers, and the dialysate
flows in the area between the fibers and the filter housing in a
counter flow to the blood. The task of a dialyser is the exchange
of matter through the wall of the hollow fibers. The blood usually
flows at an even velocity within all fibers. For an optimum of
exchange effect, the dialysate should be constantly exchanged
externally of the hollow fibers. This way a permanently high
concentration difference between the interior and exterior of the
fibers is ensured as the driving force for a diffuse exchange of
matter.
[0003] In a common design dialyser, both the inflow and outflow of
the dialysate is connected with the externally positioned fibers of
the fiber bundle. That is why it cannot be ensured initially that
all fibers in the fiber bundle are flushed with the same amount of
dialysate. If a laminar flow of the dialysate in the dialysate area
is assumed, the entire dialysate can theoretically flow through
between the fiber bundle and the housing without the dialysate
entering into the bundle interior. The exchange surface provided by
the hollow fiber bundle would not be utilized in this way. In this
case, the dialysate flows on a route of the least resistance from
the entrance along the fibers in-relating to the dialyser-axial
direction toward the output.
[0004] From DE 2851687 C2 it is known that the hollow fibers are
designed curled, or crimped for an improved penetration of the
hollow fiber bundle by the fluid flowing externally of the hollow
fibers.
[0005] From U.S. Pat. No. 3,616,928 a matter exchange apparatus
with crimped hollow fiber bundles is also known.
[0006] An oxygenator is described in EP 314581 B1 that has a hollow
fiber membrane bundle in the cylindrical housing that is also
crimped.
[0007] Crimped or curled fibers of a wavelength of about 28 mm are
used in known dialysers. The hollow fibers according to prior art
with their crimping or curling are used independently of the
geometric conditions of the dialyser.
[0008] In order to increase the performance of the dialyser,
solution approaches already exist in which other fibers have been
added to the dialysis fibers in the bundle.
[0009] Other solutions intend to wind or knot small bundles of
dialysis fibers with a thread, and to combine these small bundles
to large bundles. This should enable an improved through flow of
the hollow fiber bundle through the fluid flushing the hollow
fibers, i.e., the dialysate in the case of a dialyser.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a longitudinal section, or cross section,
through a hollow fiber bundle.
[0011] FIG. 2 shows an embodiment of the geometry of an individual
hollow fiber according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0012] It is the task of the invention to make available a generic
filter device, such as a hollow fiber dialyser, in which the fluid
flow through the hollow fiber bundle and the fluid flow external to
the hollow fibers is as even as possible, and the exchange of
matter is therefore optimized.
[0013] According to the invention, this task, based on the generic
filter device consisting of a cylindrical filter housing, and in
which a bundle of curled hollow fibers is arranged, is solved in
that the hollow fibers have an essentially sinusoidal texture, and
are curled according to the following geometrical pattern: 1 5 d
< < L 12 1 1 + 2 D L , ( 1 )
[0014] whereby .lambda. represents the wavelength of the curled
hollow fibers, d represents the exterior diameter of the hollow
fiber, L represents the effective length of the hollow fibers, and
D represents the diameter of the fiber bundle.
[0015] Through the geometric-based definition of the curling of the
individual hollow fibers of the hollow fiber bundle, the flow
resistance in axial direction, i.e., along the fibers, increased
relative to the flow resistance into the interior of the bundle is
achieved. The latter flow resistance value is generally even
absolutely reduced. The result is that the part of the dialysate
that flows through the interior of the bundle in a dialysis is
increased, and the hollow fibers positioned in the interior are
better utilized. This achieves an increased performance of matter
exchange in comparison to long-wave curled fibers, or fibers
completely without curling. The creation of a turbulent flow of the
fluid flushing the hollow fiber, as well as the fluid distribution
resulting from this, should be responsible as such for this
purpose. The invention is based on the knowledge that the ratio of
the fluid partial current flowing exterior of the fiber bundle
flows to the fluid partial current that flows through the bundle
depends on the ratio of the fiber bundle diameter to its utilized
length, as well as on the flow resistances in axial direction
(along the fibers) and in radial direction (lateral to the fibers
in the direction of the bundle center).
[0016] In addition to the wavelength .lambda., the amplitude a
plays an additional role in the effectiveness of the hollow fiber
curling. Therefore, according to a preferred embodiment of the
invention, the hollow fibers have the following amplitude a of the
essentially sinusoidal curling according to the following equation:
2 d 5 < a < 5 . ( 2 )
[0017] If a falls below the value of d/5, the space between two
values next to each other (wave consumption) becomes too small to
conduct the necessary dialysate amount into the interior of the
fiber bundle. However, if a>.lambda./5 is selected, the dialyser
loses effectiveness due to the fact that the possible packing
density of the fiber bundle is reduced in a predetermined dialyser
housing.
[0018] According to a special embodiment of the invention, the
curling of the hollow fiber may have a three-dimensional
orientation according to the following formulas: 3 x ( z ) = ( a
sin ( 2 z u ) sin ( 2 z ) a cos ( 2 z u ) sin ( 2 z ) z ) , ( 3
)
[0019] whereby: 0.05<u<0.14, and whereby {overscore
(.chi.)}(z) represents the space vector between the coordinate
origin and the spatial position of a hollow fiber that extends
along the z-axis, and u represents the amount of rotations per
wavelength .lambda..
[0020] Corresponding to the previously mentioned equation, the
curling of the hollow fibers rotates in a circular pattern. This
means that the mathematical vector of the amplitude that is based
on the z-axis and ends at the fiber, runs through a certain angle
area within the distance .lambda.. This creates a three-dimensional
structure similar to a helix. While it may happen in a
two-dimensional structure that all fibers "fall over," and thereby
form an isotropic structure that makes the penetration of the
dialysate into the bundle dependent upon the direction, a
three-dimensionally curled fiber bundle is isotropic, and ensures
the even penetration of the dialysate into the interior of the
bundle from all sides.
[0021] Preferably, the fiber allocation in the cylindrical filter
housing can be between 60.5% and 70%, even more preferably from
60.5% to 67.5%. Dense packing with a seal by means of grouting in
the end area of the hollow fiber bundle is possible with these
packing densities.
[0022] Particularly advantageous, the fiber allocation in the
cylindrical filter housing can be between 63.5% and 65.5%. The
fiber allocation is calculated from the percentages of the cross
section surface allocated by the fibers per utilizable cross
section surface in the filter housing. The utilizable cross section
surface is 0.907 times the cross section surface. This value is
calculated from the maximum packing density (hexagonal
arrangement), which should correspond to an allocation of 100%. The
above stated allocation information can be achieved particularly
with the use of the dimensions appropriate to this invention of the
hollow fibers, and simultaneously ensure that the polyurethane
matter evenly penetrates the fiber bundle with the grouting of the
fibers similar to--as previously described--the dialysate evenly
entering the interior of the bundle in the dialysis. Especially by
the even penetration of the polyurethane matter, which subsequently
solidifies and firmly fixes the fiber bundle as such at both ends,
the simultaneous allocation of the fiber bundle, and therefore the
previously mentioned high packing density can be achieved.
[0023] The effect of the invention is also achieved by a
combination of elongated flat and three-dimensionally curled
fibers, if at least 10% of three-dimensionally curled fibers are
used in the fiber bundle.
[0024] The invention is based on a curled hollow fiber for optional
use in the form of a bundle in hollow fiber dialysers that may have
different diameters D, from a minimum diameter D.sub.MIN up to a
maximum diameter D.sub.MAX. In this case, an optimal hollow fiber
shape should be provided, if possible, which can be used for hollow
fiber dialysers of various diameters. The curled hollow fiber for
use in filter housings of various diameters is calculated from the
following equation: 4 5 d < < L 12 1 1 + 2 DMax L , ( 4 )
[0025] whereby .lambda. represents the wavelength of the curled
hollow fiber, d represents the diameter of the hollow fiber, L
represents the effective length of the hollow fibers, and D.sub.MAX
represents the diameter of the fiber bundle for the fiber housing
with the maximum interior diameter.
[0026] An example embodiment of the hollow fibers consists of 90 to
99 weight percent of a hydrophobic first polymer, and 10 to 1
weight percent of a hydrophilic second polymer, whereby the
hydrophobic first polymers are selected from the following group:
polyarylsulfons, polycarbonates, polyamides, polyvinyl chlorides,
modified acrylic acid, polyether, polyurethane, or their
co-polymers, and whereby the hydrophilic second polymers are
selected from the following group: polyvinylpyrrolidon,
polyethylene glycol, polyglycolmonoesther, co-polymers from
polyethylene glycol with polypropylenglycol, water soluble
derivatives of cellulose or polysorbates. This composition of
microporous hollow fibers has already been described in detail in
EP 0168783 A1, which also includes additional details for this
example.
[0027] Additional examples for the embodiment of the hollow fibers
regarding their composition and morphology are found in EP 0 305
787 A1, as well as in the published application DE 21 45 183. We
expressly refer to the disclosure of these applications.
[0028] The invention is also based on a method for filling a filter
device, especially a hollow fiber dialyser, whereby the air present
at the beginning of the filling operation in the exterior space,
i.e., in the space surrounding the hollow fibers, is displaced by
means of a fluid volume flow that is guided from top to bottom
through the filter housing. The fluid volume flow for the filling
of the filter housing is preferably approximately 500 ml/min.
Surprisingly it has been shown that both fluid chambers of the
dialyser can be filled by means of the construction of the hollow
fiber dialyser as described above, without having to turn the
dialyser by 180.degree..
[0029] According to prior art, in which the fiber bundle was not
constructed as evenly and as densely packed, as it is possible
according to the invention at hand, the system had to be filled
from the bottom to the top at a vertical filter position for the
air-free filling of said system. As for the dialyzing fluid pump,
and the blood pump discharge in reverse of one another, the filling
of each chamber with dialyzing fluid according to prior art had to
occur on the dialyser side, or with isotone salt solution
successively on the blood side, whereby the filter had to be turned
by 180.degree. before performing the second step. This procedural
step for the filling operation is no longer necessary with the new
filter. The dialysate space can be filled from the top to the
bottom. The filling can occur simultaneously with the filling on
the blood side, without having to turn the dialyser.
[0030] Finally, the invention relates to the use of the previously
described filter device for the filling of the filter housing by
means of a fluid volume flow that is guided through the filter
housing from top to bottom. This use of the filter device enables a
quick, and especially air-free filling of the system. The higher
filling velocity results from the fact that both fluid chambers of
the dialyser, i.e., the chambers on the dialyser side and on the
blood side, can be filled simultaneously without having to turn the
filter device.
[0031] FIG. 1 shows a micro-curled hollow fiber bundle at the
effective length L with the diameter D. It is arranged in a known
and usual way in a filter housing that is not illustrated in
detail. The construction of the filter device is generally
extensively known, and is therefore not explained in detail.
Generally, a known filter device exists, such as a hollow fiber
dialyser, comprised of a tube-shaped housing that includes the
hollow fiber bundle, whereby the ends of the hollow fiber bundle
are connected at the ends of the tube-shaped housing by means of a
compound. In this filter device, the housing is arranged in a
limited way to the compounds with radial connectors, which form the
inputs and outputs to the second flow area. For the opening of the
capillary tubes of the hollow fiber bundle that are enclosed by the
compounds, they are spliced at their ends.
[0032] Sealing caps are then placed on the ends of the tube-shaped
jackets that are equipped with connectors, which form the inputs
and outputs of the first flow area.
[0033] Reference is made to the disclosure of DE 198 57 850 and
EP-A-0844015.
[0034] According to the invention, a sinusoidal texture is
preferably created from hollow fiber membranes, whereby the
wavelength .lambda. of the periodic structure is closely tied to
the outer diameter d of the hollow fiber (compare FIG. 2), as well
as with the effective fiber length L and the bundle diameter D
(compare FIG. 1) of the fiber bundle. The optimal .lambda. is
within the following range: 5 5 d < < L 12 1 1 + 2 D L . ( 1
)
[0035] According to equation 1 it is not appropriate to choose a
wavelength that is smaller than five times the outer diameter d of
the fiber (FIG. 2). This can be explained by the fact that, falling
short of 5 d, wave loops are no longer created in the hollow fiber
that enable the dialysate to enter the interior of the fibers. The
wavelength .lambda. is limited in the upper range by means of the
effectiveness in the performance increase. It was surprisingly
found that the presence of 12 wavelengths per fiber length L is
sufficient for "thin dialysers," i.e., diameter to length ratios of
D/L <0.14, in common fiber diameters. In the case of "thicker
dialysers" with an unfavorable ratio of diameter to length, i.e.,
of D/L, it becomes more difficult for the dialysate to reach the
center of the fiber bundle at the same wavelength .lambda.. In
order to compensate for this, the geometry for the calculation of
the maximum wavelength by the factor 1/(1+2 D/L) is considered in
the equation.
[0036] If the same wavelength .lambda.is to be used for all
dialyser sizes for a hollow fiber, the equation (1) D must be
replaced by the maximum diameter D.sub.MAX. Here a penetration of
the fiber bundle is ensured even with unfavorable diameter to
length conditions, especially when the dialysate flows through
comparably narrower dialysers.
[0037] For dialysis fibers with a diameter of d=0.28 mm, and the
dialyser with the largest thickness, having an effective length of
L=225 mm, and a maximum inner diameter D.sub.MAX of=48 mm, a range
of
1.4 mm<.lambda.<13.1 mm
[0038] is created for the wavelength .lambda..
[0039] In practical applications, values for the wavelength
.lambda. of
4 mm<.lambda.<12 mm
[0040] have proven particularly effective.
[0041] In addition to the wavelength .lambda., amplitude also plays
a major role in the effectiveness of the micro-curling. The
amplitude a (compare FIG. 2) should be within the following range:
6 d 5 < a < 5 . ( 2 )
[0042] If a falls short of the value of d/5, the space between two
adjoining waves becomes too small in order to feed the required
amount of dialysate into the interior of the fiber bundle.
[0043] However, if a is larger than .lambda./5, a comparatively
smaller packing density is put up with, which leads to a decrease
of the effectiveness of the matter exchange.
[0044] By means of the so-called micro-curling, it is ensured that
the dialysate is fed everywhere along the hollow fibers into the
hollow fiber interior through the wave loops, and the flow along
the hollow fibers is simultaneously always re-directed and
decelerated. In this way, an optimal matter exchange can occur
along the exchange surface.
[0045] Particular benefits arise from the use of the hollow fibers
equipped with the previously mentioned micro-curling in the shape
of a tightly packed fiber bundle, in particular corresponding to
the previously discussed packing density, as a filter device with
such a hollow fiber package can be filled more easily. Here, both
fluid chambers, namely the one on the dialysate side, as well as
the chamber on the blood side, can be filled simultaneously, and
especially air-free. This results in a decisive advantage as
opposed to the current prior art, in which the chamber for the
dialysis fluid, and the chamber on the blood side must be filled
successively, whereby the filter device additionally had to be
turned by 180 degrees for an air-free filling. This was due to a
complicated handling procedure, which is no longer necessary with
the use of the micro-curled hollow fiber in the filter device
described herein.
* * * * *