CA2229843A1 - Hollow fiber oxygenator - Google Patents
Hollow fiber oxygenator Download PDFInfo
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- CA2229843A1 CA2229843A1 CA002229843A CA2229843A CA2229843A1 CA 2229843 A1 CA2229843 A1 CA 2229843A1 CA 002229843 A CA002229843 A CA 002229843A CA 2229843 A CA2229843 A CA 2229843A CA 2229843 A1 CA2229843 A1 CA 2229843A1
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- fibers
- blood
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- hollow fiber
- core
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- 239000012510 hollow fiber Substances 0.000 title claims abstract description 100
- 239000000835 fiber Substances 0.000 claims abstract description 227
- 239000008280 blood Substances 0.000 claims abstract description 161
- 210000004369 blood Anatomy 0.000 claims abstract description 161
- 239000007789 gas Substances 0.000 claims abstract description 83
- 238000007789 sealing Methods 0.000 claims abstract description 65
- 230000017531 blood circulation Effects 0.000 claims abstract description 28
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 25
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 25
- 239000001301 oxygen Substances 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 17
- 230000001706 oxygenating effect Effects 0.000 claims abstract description 8
- 238000000638 solvent extraction Methods 0.000 claims description 34
- 239000010410 layer Substances 0.000 claims description 18
- -1 polypropylene Polymers 0.000 claims description 7
- 239000004743 Polypropylene Substances 0.000 claims description 6
- 229920001155 polypropylene Polymers 0.000 claims description 6
- 239000002356 single layer Substances 0.000 claims description 4
- 241001465754 Metazoa Species 0.000 claims description 2
- 239000011148 porous material Substances 0.000 claims description 2
- 230000001225 therapeutic effect Effects 0.000 claims description 2
- 238000004804 winding Methods 0.000 description 17
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 10
- 239000000463 material Substances 0.000 description 7
- 230000005465 channeling Effects 0.000 description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 description 5
- 238000010276 construction Methods 0.000 description 5
- 239000001569 carbon dioxide Substances 0.000 description 4
- 239000012530 fluid Substances 0.000 description 4
- 230000002612 cardiopulmonary effect Effects 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229920000515 polycarbonate Polymers 0.000 description 3
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- 229920000193 polymethacrylate Polymers 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000001356 surgical procedure Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229920013683 Celanese Polymers 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 241000543375 Sideroxylon Species 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000036772 blood pressure Effects 0.000 description 1
- 238000009534 blood test Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
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- 229920001577 copolymer Polymers 0.000 description 1
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- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 210000004072 lung Anatomy 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
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- 238000006213 oxygenation reaction Methods 0.000 description 1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
- B01D63/02—Hollow fibre modules
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
- A61M1/14—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis
- A61M1/16—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis with membranes
- A61M1/1698—Blood oxygenators with or without heat-exchangers
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
- A61M1/36—Other treatment of blood in a by-pass of the natural circulatory system, e.g. temperature adaptation, irradiation ; Extra-corporeal blood circuits
- A61M1/3621—Extra-corporeal blood circuits
- A61M1/3623—Means for actively controlling temperature of blood
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
- B01D63/02—Hollow fibre modules
- B01D63/026—Wafer type modules or flat-surface type modules
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
- B01D63/02—Hollow fibre modules
- B01D63/04—Hollow fibre modules comprising multiple hollow fibre assemblies
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2313/00—Details relating to membrane modules or apparatus
- B01D2313/13—Specific connectors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2313/00—Details relating to membrane modules or apparatus
- B01D2313/22—Cooling or heating elements
- B01D2313/221—Heat exchangers
Landscapes
- Health & Medical Sciences (AREA)
- Heart & Thoracic Surgery (AREA)
- Vascular Medicine (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Chemical & Material Sciences (AREA)
- Hematology (AREA)
- Anesthesiology (AREA)
- Biomedical Technology (AREA)
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
- Public Health (AREA)
- Veterinary Medicine (AREA)
- Urology & Nephrology (AREA)
- Emergency Medicine (AREA)
- Cardiology (AREA)
- External Artificial Organs (AREA)
Abstract
The present invention relates to a hollow fiber oxygenerator, comprising a housing, comprising a core wall and an outer wall spaced from the core wall thus forming a chamber between the walls, at least one blood inlet to and at least one blood outlet from said chamber, first and second caps closing the chamber at a first and, respectively, a second end thereof, one of the caps having at least one gas inlet, the other having at least one gas outlet associated therewith, selectively permeable continuous hollow fiber filaments extending inside the chamber between the first cap and the second cap, wherein the ends of the fibers are sealed between the core wall and the outer wall at the ends of the chamber spaced from the caps, thus leaving a header space between the sealings and the caps, the ends of the fibers being open, wherein the circumferential angle difference for the fibers between the two sealings is between 0~ and 180~ and to a method for oxygenating blood, comprising passing a free oxygen containing gas through a plurality of hollow fiber filaments extending principally axially through an oxygenerator chamber and passing blood through the oxygenator chamber, wherein the blood flows primarily axially through the chamber along the plurality of fibers, characterized in that the fibers are arranged in such a way that they cause integrally a helical flow of the blood around the axis of the chamber.
Description
W O 97/08933 PCT~US96/14148 Hollow fiber oxygenator The present invention relates to a hollow fiber oxygenator, a specific hollow fiber arrangement and a method for oxygenating blood.
In the field of cardiopulmonary surgery which often involves an extra-15 corporeal blood circulation, there is a demand for blood ~ygenators toreplace the bre~thing function of the lungs by removing carbon dio~cide from the blood and feeding oxygen to the blood. The extraco~
blood circulation is required to replace all functions of the patients heart and blood circulation system, thus f~ illing its special requirements as to ~o blood flow, blood temperature, e~ h~n~e of carbon dioxide and odygen.
The physiological properties of the blood shall not be altered in the extracorporeal blood circulation system. Various blood o~ygenators for use in cardiopulmonary surgery are known.
2s EP-A-0 089 122 discloses a hollow fiber blood a~ygenator having a mat of a plurality of contiguous fiber layers around a porous core, wherein contiguous fiber mat layers exhibit an angle of divergence from the longitll~iin~l axis of the core, wherein the sense of divergence changes in every layer. The blood flows radially across the fiber mat. The fibers do not substantially fill the whole of an ~nnni~r chamber around the core.
EP-B-0 187 708 discloses a hollow fiber blood oxygenator, wherein fibers or small fiber ribbons are wound helically around a core, wherein a first CA 02229843 l998-02-l9 plurality of fibers is wound in one sense and a second plurality of fibers is wound in ehe other sense similar to a yarn winding operation. The blood flows axially through the fiber win(~ingc, which occupy substantially all of an ~nn~ r chamber around the core. Gas flow and blood flow s may be counter-current.
US-4,239,729 discloses a hollow fiber blood o~ygenator, wherein fibers are arranged axially in an elongated housing and do not substantially fill the housing. Blood flows through the fibers whereas the o~ygenating gas o flows radially with respect to the fibers.
US-3,422,008 discloses a hollow fiber blood oxygenator and a method for forming it, wherein hollow fibers are helically wound on the core in such a way that intermediate helical windings are reversed. Thus, successive 5 layers have opposite winding sense with respect to the core axis. The blood flow is radial. The ~nnl~l~r space is not substantially filled with the fibers.
US-4,031,012 discloses a separatory apparatus which can be used as an oxygenator comprising a card-shaped core on which hollow fibers are wound either parallel to the core, having an angle to the core axis, or having a criss-cross arrangement or zigzag arrangement with respect to successive layers in which the angle is reversed. A counter-current flow of blood and oxygen is preferred, wherein the blood flows outside the 2s hollow fibers.
GB-1 481 064 discloses a membrane apparatus which may be an oxyge-nator having hollow fiber bundles being contained in a receptacle but not substantially filling it. An angle of 10 to 40~ may be formed between adjacent layers of fiber bundles. The fluid flow is principally radial.
US ~,141,835 discloses a dialysis apparatus, wherein a number of separa-ted fibers are arranged in a straight line in a housing. The housing is not filled with the fibers which may also be arranged in helical lines. A
fluid flows axially outside the fibers.
s EP-A-O 093 677 discloses an apparatus which can be used as an oxyge-nator in which rolled mats of fibers are arranged, in which the fibers may be crossed in an angle between 1 and 5~. The blood flows in the fibers.
The known hollow fiber oxygenators exhibit a number of disadvantages depending on their construction. They are bully, have a short blood flow path through the oxygenator and have, thus, a small contact zone for the blood and the gas and consequently a short residence time for the blood in the oxygenator which leads to a poor gas exchange rate. Blood and gas pressure drops may occur as well as channelling of blood or stagna-tion of blood in certain areas of the contact zone between blood and gas.
The invention It is thus one object of the invention to provide a blood oxygenator of a small construction size but retaining a high gas çY~h~nge rate.
A further object of this invention is to provide a blood o~ygenator which is of simple construction, allowing in particular a simple arrangement on and application to a core of hollow fibers.
A further object of this invention is to provide a blood axygenator allowing a improved contact of blood and gas.
A further object of this invention is to provide a blood oxygenator in s which the channeling of blood and areas of blood st~gn~tion are avoid-ed.
Still a further object of the present invention is to provide a blood oxygenator which exhibits a low pressure drop of the blood flowing o through the oxygenator.
These and other objects, advantages, details, features and embodiments of this invention will become apparent to those skilled in the art from the following detailed description of the invention, the appended claims, s the drawings, and the examples.
In accordance with this invention a hollow fiber oxygenator is provided, which comprises a housing, comprising - a core wall and an outer wall spaced from the core wall thus forming a chamber between the walls, - at least one blood inlet to and at least one blood outlet from said chamber, - first and second caps closing the chamber at a first and, respec-tively, a second end thereof, one of the caps having at least one gas inlet, the other having at least one gas outlet associated therewith, selectively permeable continuous hollow fiber filaments extending inside the chamber between the first cap and the second cap, wherein the ends of the fibers are sealed between the core wall and the outer wall at the ends of the chamber spaced from the caps, thus leaving a header space between the se~lingc and the caps, W O 97/08933 PCT~US96/14148 the ends of the fibers being open, wherein the circumferential angle difference for the fibers between the two sealings is between 0~ and 180~.
s ~n a preferred embodiment, the fibers are arranged in a first plurality of fibers and in a second plurality of fibers, wherein the first plurality of the fibers and the second plurality of the fibers have the same directio-nal sense but different circumferential angle differences, the length of the fibers of the first pluraliy of fibers being different o from the length of the fibers of the second plurality of fibers.
In prior art devices the fibers have been wound around the core in a technique similar to winding yarn on a bobbin (continuous rotation of the core coupled with oscill~ting axial movement of the fiber guide also known as cross winding). Thereby the circumferential angle difference of a given fiber between the two sealings was always well above 360~, frequently involved several full rotations, i.e. multiples of 360~. This prior art procedure had the disadvantage that a wrapping process and thus very long fibers between the se~lings was required. The present invention avoids this drawback and allows the use of much shorter fibers as well as a simpler production of the oxygenator.
Furthermore in accordance with this invention a hollow fiber oxygenator is provided, which comprises a housing, comprising 2s - a core wall and an outer wall spaced from the core wall thus forming a chamber between the walls, - at least one blood inlet to and at least one blood outlet from said chamber, -W O 97/08933 PCT~US96/1~148 - first and second caps closing the chamber at a first and, respec-tively, a second end thereof, one of the caps having at least one gas inlet, the other having at least one gas outlet associated therewith, selectively permeable continuous hollow fiber filaments extending inside the chamber between the first cap and the second cap, wherein the ends of the fibers are sealed between the core wall and the outer wall at the ends of the chamber spaced from the caps, thus leaving a header space between the sealings and the caps, the ends of the fibers being open, o wherein at least one partitioning wall is located between the core wall and the outer wall spaced therefrom, extending from one of the sealings towards the other sealing, thus dividing the chamber into sections, having a flow connection between the sections in the vicinity of the other sealing, allowing for counter-current flow of S blood and gas in one section and co-current flow of blood and gas in another section.
By the specific arrangement of the fibers and/or the partitioning wall the residence time of the blood inside the oxygenator is increased, thereby ~o improving the gas ç~r~h~nge rate of the oxygenator. By the specific orientation of the fibers inside the oxygenator a longer flow path of the blood is achieved which results in a better gas transfer, a longer residen-ce time and thus a smaller construction size of the whole oxygenator arrangement while retaining the same performance or even improved 2s performance. With the specific arrangement of the fibers and the blood flow path through the oxygenator no channeling of blood occurs, areas of blood stagnation are avoided and the pressure drop for the blood is rather low, thus allowing a treatment of the blood under moderate conditions which prevent or reduce the damage of the components of the blood. The specific arrangement of fibers allows a very simple W O 97/08~33 PCT~US96/14148 construction of the blood oxygenator, especially a very simple arrange-ment of the fibers around the core of the oxygenator. ~n the following preferred embodiments of this invention will be described with reference to the drawings in which s Fig. 1 is a perspective view of an assembled oxygenator according to the present invention with a partly cross-sectional view;
Fig. 2 is a perspective view of a second preferred embodiment of an assembled oxygenator according to the present invention with a o partly cross sectional view;
Fig. 3 is a cross-sectional view of a second preferred embodiment of the oxygenator according to the present invention of Fig. 2; and Fig. 4 is a perspective view of a hollow fiber arrangement according to the present invention;
15 Fig. 5 is a perspective view of a hollow fiber arrangement according to the present invention showing the blood flow path through the fiber filaments and gives an illustration of the definitions of fiber directions.
Housing The housing of the oxygenator according to the present invention may be formed of any suitable material which does not adversely interfere with 2s the blood and the free oxygen cont~ining gas, flowing through the oxygenator, respectively. Suitable materials include, but are not limited to, glass, ceramics, metals and alloys as well as polymeric materials like polycarbonate, polyesters, polyacrylates and polymethacrylates. Copolymers and mixtures of polymers are suitable as well. The preferred materials are polymeric m~teri~ls and alloys thereof.
W O 97/08933 PCT~US96/14148 The housing of the oxygenator comprises a core wall which may be of any desirable shape. The core wall may be of cylindrical form. It may have a circular or polygonal cross-section. Preferably, the core wall has a cylindrical shape with a circular cross-section, the diameter being s approximately equal to the height of the cylinder.
The oxygenator further comprises an outer wall which is spaced from the core wall, thus forming a chamber between the walls. Preferably outer wall and core wall are parallel to each other leaving a space of equal o width in between. Thus, the chamber may be annular, in particular having a circular or polygonal cross section. In the preferred embodiment the outer wall forms a cylinder of circular cross-section surrounding the core cylinder and leaving a chamber in between. In a preferred embodi-ment the inner core has an outer diameter of 100 to 104 mm and a lS height of 130 to 150 mm, the outer wall having an inner diameter of 132 to 134 mm. Thus, between the two cylinders there is an ~nn~ r space with a width of 13 to 17 mm.
In the walls at least one blood inlet to and at least one blood outlet from the chamber are formed. The blood inlet and the blood outlet may be formed in the core wall or in the outer wall or in both walls. The blood inlet and the blood outlet may be located at opposite ends of the core wall or the outer wall or at the same ends, respectively.
2s In the preferred embodiment as depicted in Fig. 1 the blood inlet is formed in the bottom section of the core wall. Preferably, a plurality of blood inlets are formed at the circumference of the chamber or of the core wall so that blood being introduced in the space between the core wall and the outer wall may be evenly distributed around the circumfer-ence at the bottom of the core wall.
W O 97/08933 PCTrUS96/141 According to the preferred embodiment depicted in Fig. 1 the blood outlet is formed at the outside of the outer wall at the top thereof.
Like for the blood inlet a plurality of outlets are located at the circum-ference of the chamber, especially of the top of the outer wall. Thereby the blood is removed from the space between the core wall and the outer wall evenly distributed around the circumference of the outer wall.
lBy this arrangement the blood flows principally axially through the space between the core wall and the outer wall.
o According to another preferred embodiment the blood inlet and the blood outlet may be respectively located at the same ends of the core wall and the outer wall.
In the preferred embodiment depicted in Fig. 2 and 3 the blood outletss are arranged in the same manner as in the embodiment of Fig. 1 with the difference that the outlets are located at the bottom of the outer wall.
The chamber formed between the core wall and the outer wall is closed by first and second caps at a first and, respectively, a second end there-of. The caps may be integrally formed in the core wall and the outer wall but may as well be formed separately and joined to the core wall and the outer wall at a later stage.
2s In the caps there are at least one gas inlet and at least one gas outlet formed which may be connected with tubings for feeding and withdraw-ing a gas, preferably a free oxygen cont~ining gas. In the preferred embodiment in Fig. 2 and 3 the gas inlet is formed in the top cap and the gas outlet is formed in the bottom cap.
-W O 97/08933 PCT~US96/14148 Apart from the gas inlet, the gas outlet, the blood inlet and the bloodoutlet further connections may be provided in the core wall, the outer wall, or the caps in order to introduce e.g. means for measuring the temperature of the blood or to withdraw blood test samples.
WO 97/08933 PCT~US96/14148 Hollow fibers The hollow fibers or hollow fiber filaments used in this invention may be any fibers that are selectively permeable and have continuous lumens therethrough.
The fibers are preferably made of polypropylene which has been modi-fied by silicones or other types of polymers.
o The hollow fiber filaments may have any desirable diameter, with an outer diameter of from 365 to 400 ,(Lm preferred, from 365 to 380 ~m being especially preferred. Useful hollow fiber filaments are commercially available from AKZO and CELANESE companies and under the name oxiphan and celgard, respectively.
Another preferred hollow fiber is a microporous polypropylene hollow fiber with an inner diameter of 50 ~lm, an external diameter of 280 ~Lm, an average pore size of 0,04 ~Lm and a porosity of 50~o.
~0 lHollow fiber arrangement The selectively permeable continuous hollow fiber filaments extend inside the chamber between the first cap and the second cap. In a preferred 2s embodiment the hollow fibers substantially fill the chamber between the core wall and the outer wall.
The ends of the fibers are sealed between the core wall and the outer wall at the ends of the chamber spaced from the caps, thus leaving a header space between the se~lingc and the caps. The ends of the fibers W O 97/08933 PCT~US96/14148 - 12 -are open, so that gas m~y flow from the gas inlet of one of the caps through the fibers and finally through the gas outlet in the other cap.
~ n the preferred embodiment depicted in Fig. 1 the fibers are arranged in the chamber in such a way that the circumferential angle difference for the fibers between the two sealings is between 0~ and 180~. The term "circumferential angle difference" describes the angle through which the core must be turned around its longitudinal axis in order to arrive from one sealing of the hollow fiber to the other sealing of the hollow lO fiber. It may also be described as the angle between the projections of the longitudinal aYis of the core, the first sealing point of the fiber and the second sealing point of the fiber into a plane which is perpendicular to the longitudinal axis of the core. Fig. S illustrates the term "circumferential angle difference".
This circumferential angle difference is between 0~ and 180~ for the fibers, preferably between 0~ and 90~.
The hollow fibers are divided into a first plurality of fibers and a second plurality of fibers. Both pluralities of fibers have the same direc-tional sense with respect to the circumferential angle difference formed by them, but they have different circumferential angle differences. This means that the path of one of the pluralities of fibers from one sealing to the other sealing is steeper than the path of the other plurality of fibers.
Furthermore, the length of the fibers of the first plurality of fibers is different from the length of the fibers of the second plurality of fibers.
This is a result of the path of one of the plurality of fibers being steeper than the path of the other plurality of fibers. Thus, one plurality of fibers has a longer path from one sealing to the other sealing thus forming a different length of this plurality of fibers from the other plurality of fibers. Preferably, the filaments in each of the plurality of fibers are parallel to each other and pass from one sealing to the other s sealing substantially without any additional curves or bends. In this way the steeper plurality of fibers necessarily has a smaller length between the se~lings than the less steeper plurality of fibers.
With a circumferential angle difference of 0~ the fiber filaments extend 10 principally parallel to the longitudinal axis of the core from one sealing to the other sealing. With a circumferential angle difference of 180~ the fibers pass halfway around the core on their way from one sealing to the other sealing. Thus, none of the fibers passes more than halfway around the core of the oxygenator chamber.
In the oxygenators according to the state of the art usually a plurality of fibers is wound around the core in a helical fashion. At the end of the core the winding direction is reversed but the winding sense is m~int~ined. ThUs, the winding of the fibers on the core is similar to a ~o yarn winding operation wherein the yarn is passed up and down on the turning core on which it is wound. This manner of winding fibers around the core has several restrictions: each fiber must be wound around the core several times in order to fix it to the core. Thus, usually the circurnferential angle difference for the fibers between the se~lingc is a ~s multiple of 360~. This large circumferential angle difference is necessary to fix the fibers on the core when ~he winding direction of the fiber is ~ reversed at the end of the core. Otherwise, the fibers would fall off the core. The reversal of the winding direction but not of the winding sense leads necessarily to an arrangement of fibers in which (after cutting the fibers in the region of the se~lingc) one plurality of the fibers has one W O 97/08933 PCTrUS96/14148 directional sense on the core and one circumferential angle difference, and a second plurality of fibers has the opposite directional sense around the core and the same circumferential angle difference but in the oppo-site directional sense.
Consequently it is not possible to arrange fibers around the core with a circumferential angle difference being less than 180~ (for practical reasons not less than at least several hundred degrees). Furthermore, it is not possible that two pluralities of fibers have the same directional sense but o different circumferential angle differences since the arrangement of the second plurality of fibers is just the reversed arrangement of the first plurality of fibers, thus always leading to the same circumferential angle difference but different directional senses.
s As a consequence the hollow fiber arrangement according to the first embodiment of the present invention cannot be obtained by rotating the core and winding the filaments from a continuous roll of filaments onto the core by reversing the feed direction of the filament at the top and bottom ends of the core, since this process for m;lnl~f~cturing the fiber ~o mat is only applicable when the second plurality of the fibers are wound in the other sense with respect to the first plurality. In a preferred embodiment of the present invention the circumferential angle differences of the first plurality of fibers and the second plurality of fibers differ by at least 5~.
2s The direction of the fibers around the core may be further described by the inclination angle between the fiber filaments and the longitudinal axis of the core. If this inclin~tion angle amounts to 0~, the fiber fila-ments are principally parallel to the longitudinal axis of the core. When this angle is 90~, the fibers run around the core in one plane each with which is perpendicular to the longitudinal axis of the core. According to a first embodiment of the present invention the preferably parallel fibers of the first plurality of fibers have an inclination angle with the longitu-~ dinal axis of the core of less than 90~ and the preferably parallel fibers of the second plurality of fibers have an inclination angle with the longitudinal axis of the core of between 0~ and the inclination angle of the fibers of the first plurality of fibers. Thus, the two pluralities of fibers have different inclination angles with respect to the longitudinal axis of the core. This is shown in Fig. 4.
Preferably the fibers of the first plurality of fibers have an inclinationangle with the longitudinal axis of ~he core of from 10~ to 40~ and the fibers of the second plurality of fibers have an inclination angle with the longitudinal axis of the core of between 0~ and the inclination angle of the fibers of the first plurality of fibers. In a further preferred embodi-ment the fibers of the first plurality of fibers have an inclination angle of from 10~ to 25~, especially 10~ to 20~, and the fibers of the second plurality of fibers have an inclinatio~ angle of from 0~ to 7~, preferably 0~ to 4~, more preferably 2~ to 4~. In an especially preferred embodi-ment, the pluralities of fibers have an inclination angle of 12~ and 4~,respectively.
The hollow fiber filament filling of the chamber may be achieved by arranging continuous strips of layers of fiber filaments around the core ~s with the proviso that the axial width of said strips is longer than the axial distance between the sealings. Thus, continuous strips of layers of fiber filaments are formed and then these strips are in a second step arranged around the core, e.g. by spirally winding the continuous strip around the core. Since the axial width of the strips is longer than the axial distance between the se~lin~.s, the continuous strip need not be CA 02229843 1998-02-l9 W O 97/08933 PCT~US96/14148 - 16 -wound helically around the core which would involve passing the feed of the continuous strips along the longitudinal axis of the core. Thus, the arrangement of the continuous strips of layers of fiber filaments is much simpler in comparison to the yarn spool-like winding of the fibers ac-s cording to the state of the art.
According to a preferred embodiment of the present invention twocontinuous strips of layers of fiber filaments are arranged around the core, wherein the strips have two parallel edges between which at least o one layer of parallel spaced fiber filaments extends being inclined with respect to the parallel edges, wherein one strip contains the first plurality of parallel fibers with the first inclination angle and the second strip contains the second plurality of parallel fibers having the second inclina-tion angle. The strips may have single layers of the fiber filaments and the two strips may be arranged around the core in a manner that contiguous layers of the core in radial directions have different inclina-tion angles. This is indicated in Fig. 4.
The hollow fiber filament filling of the chamber may as well be achie-ved by successive layers of short single layer woven mats of the fiberfilaments.
In these embodiments strips of mats of single layers of fiber filaments are prepared by first arranging a layer of long parallel fibers substantial-2s Iy equally spaced from each other which are then fixed in their positionby a connecting element, preferably a cross thread which is a flexible small diameter monofilament. The thread must be sufficiently flexible to be easily bent around the hollow fibers. Furthermore, it must have sufficient tensile strength and tension to fix the filaments in their posi-, W O 97/08933 PCT~US96/14148 - 17 -tion, like in known tissues of clothes. This monofilament allows a regular spacing between the short single fiber filaments.
The essentially parallel fibers in each of the strips are spaced from each other by preferably 0,8 to 1,2 fiber diameters. The connecting element, preferably the thin filament-like connector or cross-thread is arranged transversely in all fibers of the strip in said strips or parallel to the upper and lower edges thereof.
o In the embodiment of the present invention depicted in Fig. 2 and 3 a known hollow fiber filament filling may be applied in which the hollow fiber filaments extend inside the chamber between the first cap and the second cap. The circumferential angle difference of the fiber filaments between the sealings is not restricted and the directional sense of the fibers is not restricted either. However, a partitioning wall described below has to be provided in this embodiment.
The hollow fiber filaments may be cross wound around the core as it is known from the prior art. This results in a first plurality of fibers being wound in one sense around the core, having one inclination angle, a second plurality of fibers, being wound around the core in the opposite sense, having the opposite inclination angle. The circurnferential angle differences are the same for both pluralities of fibers and this difference exceeds 360~.
Preferably the hollow fiber filaments have the arrangement described above for the first embodiment.
The hollow fibers are sealed in the space between the core wall and the outer wall at the top and the bottom thereof the ends of the filaments W O 97/08933 PCT~US96/14148 being open so that a gas can flow through the fiber filaments. Prefera-bly, the fibers are sealed with a polymeric resin which has the same thermal expansion coefficient as the hollow fibers and the housing.
Useful resins are polyurethane resins, wherein epoxy resins are preferred.
s The resin sealing of the filaments is such that a chamber is formed between the core wall, the outer wall and the resin se~lin~s in which chamber blood can flow but not penetrate the se~lingc. In the preferred embodiment the sealings are arranged in such a way that between the caps and the sealings a header space is left for the introduction or 10 removal of the free oxygen containing gas. Furthermore, the se~lin~c are arranged in such a way that the blood inlets and blood outlets are arranged in the walls inside the chamber formed by the core wall, the outer wall and the se~lingc Partitioning wall According to one aspect of the present invention a partitioning wall is provided between the core wall and the outer wall in a spaced position therefrom, which extends from one sealing towards the other sealing, thus forming sections in the chamber. The sections have a flow connec-tion in the vicinity of the other sealing. The flow connection in the vicinity of the other sealing may be provided in several ways. The partitioning wall may extend into the other sealing being sealed there 2s and exhibiting apertures in the vicinity of this other sealing. Annular slits may be provided in this partitioning wall. On the other hand, the whole partitioning wall may extend only to a distance from the other sealing thus leaving an ~nn~ r space between the end of the partitioning wall and the sealing. The size of this space or the size of the holes or ~nn~ r slits m~y be varied depending on the flow conditions of the W O 97t08933 PCT~US96/14148 blood. If flow restrictions shall be irnposed on the blood, the distance or holes or slits may be formed small. Preferably, the distance or slits or holes are so big that they do not affect the flow properties of the blood ~ and do not impose a pressure drop on the blood. By this arrangements the chamber is divided into sections for counter-current flow of blood and gas and co-current flow of blood and gas, respectively.
The partitioning wall may be provided in each of the embodiments of the present invention, i.e. in connection with a hollow fiber filament o arrangement in which the circumferential angle difference for the fibers between the sealings of the chamber is between 0~ and 180~, wherein the first plurality of the fibers and the second plurality of the fibers have the same directional sense but different circumferential angle differences, the length of the fibers of the first plurality of fibers being different from the length of the fibers of the second plurality of fibers or in an arrangement in which the hollow fiber filaments extend inside the chamber between the first cap and the second cap.
Preferably, the partitioning wall is combined with the first arrangement ~o of hollow fiber filaments. Preferably at least one partitioning wall extends from one of the sealings of the chamber to a position spaced from the other sealing of the chamber.
With respect to Fig. 2 and 3 one partitioning wall is provided in the 2s oxygenator. The partitioning wall is arranged cylindrically between the core wall and the outer wall and sealed in the bottom sealing. The partitioning wall extends to a position spaced from the top sealing.
The partitioning wall may consist of any appropriate material, e.g. sheets of polymeric material like polyethylene, polypropylene, polycarbonate or W O 97/08933 PCT~US96/14148 - 2n -polymethacrylate. The preferred material is polycarbonate. The partition-ing wall may have a thickness of from S to 12 ,um, preferably 8 to 10 ,lLm. The partitioning wall divides the ~nnnl~r chamber into two sections through which the blood is passed. The two sections of the ~nnnl~r s chamber may have different sizes depending on the position of the partitioning wall between the core wall and the outer wall. The partitioning wall may be located in the center of the chamber, thus forming two sections of equal thickness, but depending on the desired flow properties or desired gas exchange properties the partitioning wall o may be located nearer to the core wall or nearer to the outer wall. The position of the partitioning wall can affect the oxygenation results when passing blood through the chamber. By locating the partitioning wall nearer to the outer wall two sections of appr xim~tely equal volume may be obtained whereas by locating the partitioning wall in the center of S the chamber two sections of different volume are obtained. The blood entering the chamber at the bottom of the core wall first flows upwardly to the top sealing of the chamber in a counter-current to the gas flow.
At a position near the top sealing of the chamber the flow direction of the blood is reversed and it flows downwardly to the bottom sealing in the second section, thus co-current with the gas flow. The blood leaves the chamber at the blood outlet. By this arrangement the blood path through the chamber is apprnxim~tely doubled. Furthermore, the blood flow is not only co-current or counter-current with the gas flow but counter-current and co-current with the gas flow. This leads to an en-zs hanced gas e~rh~nge rate between blood and gas.
Further partitioning walls being sealed in the bottom sealing or top sealing may be arranged inside the chamber to further enlarge the flow path of the blood and enhance the gas exchange rate. In connection with the partitioning wall the ,mn~ r chamber m~y be filled with the CA 02229843 l998-02-l9 W O 97/08933 PCT~US96/14148 hollow fiber filaments in an arrangement wherein the fibers of the first plurality of fibers have an inclination angle with the longitudinal axis of the core of less than 90~ and the fibers of the second plurality of fibers have an inclination angle with the longitudinal axis of the core of s between 0~ and the inclination ~ngle of the fibers of the first plurality of fibers, preferably 10~ to 25~ and 0~ to 7~, respectively.
Best results are obtained when the fibers are arranged in the latter manner, especially at angles of 4~ and 12~, respectively.
Heat ~Y~h~nger Optionally the blood inlet of the hollow fiber oxygenator according to the present invention may be provided with a heat t-~rh:~nger for con-trolling the temperature of the incoming blood. According to the prefer-red embodiments depicted in Figs. 1 to 3 the heat ~Yrhz~nger is located in the bottom of the oxygenator inside the core of the o~ygenator. It comprises a plurality of metal tubes in which a heat e~r~ nging fluid is ~o circulated. The blood is passed along the outsides of the metal tubes which are spaced from each other. The fluid used to control the tempe-rature inside the heat exch~nger is preferably water.
2s Method for o~ygen~ti~g blood According to the present invention a method for oxygenating blood is provided, comprising passing a free oxygen cont~ining gas through a plurality of hollow fiber filaments extending principally axially through an oxygenator chamber and passing blood through the oxygenator chamber, wherein the blood flows primarily axially through the chamber along the plurality of fibers, characterized in that the fibers are arranged in such a way that they cause integrally a helical flow of the blood around the axis of the chamber.
According to a second embodiment of the present invention a method for oxygenating blood is provided, comprising passing a free oxygen containing gas through a plurality of hollow fiber filaments extending principally axially through an oxygenator chamber and passing blood o through the oxygenator chamber, wherein blood flows primarily axially through the chamber along the plurality of fibers, characterized in that the blood in the first section of said chamber flows essentially in the opposite direction as the flow of the free oxygen cont~ining gas through the fibers in said first section and that the blood in a second section of S said chamber flows essentially in the same direction as the flow of the free oxygen containing gas through the fibers in said second section.
According to another embodiment of the present invention a method for oxygenating blood is provided, comprising passing blood via blood inlet ~o and blood outlet through the oxygenator as described above and passing a free oxygen containing gas via the gas inlet and gas outlet through the oxygenator, and optionally controlling the temperature of the blood, in particular with the proviso that the method is not used for therapeutical treatment of the human or animal body.
Operating conditions s The gas used in the hollow fiber oxygenator according to the present invention may be any gas containing free oxygen which is apt to transfer oxygen through the semipermeable hollow fibers into the blood and to receive carbon dioxide from the blood. Preferably, the gas should have a free oxygen content of from 21 to 100 vol~O, preferably from 60 to 90 10 vol~. The preferred gas is air, which has an oxygen content of 21%, preferably mixed with a second free oxygen containing gas, so that the preferred oxygen content of from 60 to 90 vol.~o is obtained. The gas pressure difference applied at the gas inlet and gas outlet may be from 0 to 13,3 kPa, preferably from 0 to 4 kPa. This results in a gas flow of S from 0,2 to 10 l/min. for a preferred embodiment of the oxygenator according to the present invention as depicted in Figs. 1 to 3.
To be useful in a cardiopulmonary bloodstream circulation of a human body the blood flow through the oxygenator must be in the range of from 1 to 6 I/min. In the blood ~xygenator according to the present invention the blood flow may be arranged from 0,2 to 6 I/min., prefera-bly from 1 to 6 l/min. To effect this blood flow a pressure difference of from 8 to 27 kPa must be applied between the blood inlet and the blood outlet. With a blood flow of 6 l/min. the typical residence time of the blood inside the hollow fiber oxygenator according to the present invention is 1/6 min. The flow path of the blood along the hollow fibers is approxim~tely 180 mm. Details of the blood flow path can be seen in Fig. 5. Without being bound to any theory it is believed that the blood flows along the hollow filament fibers helically around the axis of the W O 97/08933 PCT~US96/14148 chamber. This ensures an effective contact of the blood with the outer surface of the hollow fibers resulting in an improved oxygen eY~h~nge.
In comparison to the known blood oxygenators the hollow fiber blood oxygenator according to the present invention exhibits a high gas ex-change rate while having a small size of the chamber filled with hollow filament fibers. No channeling of blood is observed in the oxygenator according to the present invention nor are areas of blood stagnation observed. The pressure drop of the blood flowing through the oxygenator 10 lS low.
The following examples demonstrate the advantages of the hollow fiber oxygenator according to the present invention with regard to the prefer-red embodiments.
Example 1 A hollow fiber blood oxygenator according to Fig. 1 was assembled by ~o using 3,2 up to 3,6 m2 of the hollow filament fibers m~nllf~ctllred by AKZO ENKA GROUP to fill the annual chamber between the core wall and the outer wall. One half of the filaments were arranged with an inclination angle of 4~ respect to the lonEit--~lin:~l axis of the core and the other half of the fibers were arranged around the core with an 25 inclin~tion angle of 12~ with respect to the lonEitu~1in~l axis of the core.
This corresponds to circumferential angle difference of 8~ and 25~, respectively. Two strips of fibers each having one of the different inclina-tion angles were arranged in the chamber. The blood oxygenator was used to treat the blood coming from a patient in an extracorporeal circulation having an initial oxygen content of l l ml/dl and an initial carbon dioxide content of 55 rnl/dl. The applied blood pressure differ-ence was 26,6 kPa and the applied pressure difference for the air was 4 kPa. Thus, flow rates for the gas were 6 l/min. and 6 l/min. for the blood. The blood leaving the oxygenator had an oxygen content of 19,3 s ml/dl and a carbon dioxide content of 50 ml/dl. Thus, the blood oxy-genator according to the present invention showed a superior gas ex-change rate. No stagnation or channeling of blood and no agglomeration of blood particles was observed.
~xample 2 A hollow fiber blood oxygenator was arranged according to Fig. 2 and 3 by using hollow filament fiber, m~nuf~ctured by the AKZo ENKA
GROUP. The annual chamber was filled with the fibers by cross winding.
~urther experimental conditions were as follows:
A partitioning wall made of polypropylene was inserted in the annual chamber equally spaced to the outer wall at a distance of 7 - 8 mm.
The partitioning wall was sealed in the bottom sealing of the chamber.
I~ extended parallel to the outer and core wall and terminated at a distance of 13 - 15 mm from the top sealing.
The blood oxygenator according to example 2 showed a high gas ex-change rate. No channeling or stagnation of blood was observed.
W O 97/08933 PCT~US96/14148 E~ample 3 A hollow fiber blood oxygenator was arranged according to Fig. 2 and 5 3 by using hollow filament fiber, In~nl~f~ctured by the AKZO ENKA
GROUP. The annual chamber was filled with the fibers by the same method as applied in example 1. Further experimental conditions were as follows:
o A partitioning wall made of polypropylene was inserted in the annual chamber equally spaced to the outer wall at a distance of 7 - 8 mm.
The partitioning wall was sealed in the bottom sealing of the chamber.
It extended parallel to the outer and core wall and terminated at a distance of 13 - 15 mm from the top sealing.
The blood oxygenator according to example 3 showed a high gas ex-change rate. No channeling or stagnation of blood was observed.
20 Example 4 (Comparative example) A commercially available hollow fiber blood oxygenator (DIDECO 7003 ITALIA~ COMPANY) was used in a comparative experiment. Experimental conditions were as follows:
Blood in: CO2 content = 60 ml/dl ~2 content = 11.2 ml/dl Blood out: COz content = 54 ml/dl ~2 content = 17,6 ml/dl W O 97/08933 PCT~US96/14148 The pressure drop for the blood was 22,6 kPa. The flow rate for the gas was 6 I/min. and the flow rate for the blood was 6 I/rnin.
The results from Examples 1, 2 and 3 and comparative Example 4 show s that the specific arrangement of hollow fiber filaments inside the hollow fiber blood o~ygenator according to the present invention results in an improvement of gas e~ch~nge rate, while preventing channelling or stagnation of blood.
In the field of cardiopulmonary surgery which often involves an extra-15 corporeal blood circulation, there is a demand for blood ~ygenators toreplace the bre~thing function of the lungs by removing carbon dio~cide from the blood and feeding oxygen to the blood. The extraco~
blood circulation is required to replace all functions of the patients heart and blood circulation system, thus f~ illing its special requirements as to ~o blood flow, blood temperature, e~ h~n~e of carbon dioxide and odygen.
The physiological properties of the blood shall not be altered in the extracorporeal blood circulation system. Various blood o~ygenators for use in cardiopulmonary surgery are known.
2s EP-A-0 089 122 discloses a hollow fiber blood a~ygenator having a mat of a plurality of contiguous fiber layers around a porous core, wherein contiguous fiber mat layers exhibit an angle of divergence from the longitll~iin~l axis of the core, wherein the sense of divergence changes in every layer. The blood flows radially across the fiber mat. The fibers do not substantially fill the whole of an ~nnni~r chamber around the core.
EP-B-0 187 708 discloses a hollow fiber blood oxygenator, wherein fibers or small fiber ribbons are wound helically around a core, wherein a first CA 02229843 l998-02-l9 plurality of fibers is wound in one sense and a second plurality of fibers is wound in ehe other sense similar to a yarn winding operation. The blood flows axially through the fiber win(~ingc, which occupy substantially all of an ~nn~ r chamber around the core. Gas flow and blood flow s may be counter-current.
US-4,239,729 discloses a hollow fiber blood o~ygenator, wherein fibers are arranged axially in an elongated housing and do not substantially fill the housing. Blood flows through the fibers whereas the o~ygenating gas o flows radially with respect to the fibers.
US-3,422,008 discloses a hollow fiber blood oxygenator and a method for forming it, wherein hollow fibers are helically wound on the core in such a way that intermediate helical windings are reversed. Thus, successive 5 layers have opposite winding sense with respect to the core axis. The blood flow is radial. The ~nnl~l~r space is not substantially filled with the fibers.
US-4,031,012 discloses a separatory apparatus which can be used as an oxygenator comprising a card-shaped core on which hollow fibers are wound either parallel to the core, having an angle to the core axis, or having a criss-cross arrangement or zigzag arrangement with respect to successive layers in which the angle is reversed. A counter-current flow of blood and oxygen is preferred, wherein the blood flows outside the 2s hollow fibers.
GB-1 481 064 discloses a membrane apparatus which may be an oxyge-nator having hollow fiber bundles being contained in a receptacle but not substantially filling it. An angle of 10 to 40~ may be formed between adjacent layers of fiber bundles. The fluid flow is principally radial.
US ~,141,835 discloses a dialysis apparatus, wherein a number of separa-ted fibers are arranged in a straight line in a housing. The housing is not filled with the fibers which may also be arranged in helical lines. A
fluid flows axially outside the fibers.
s EP-A-O 093 677 discloses an apparatus which can be used as an oxyge-nator in which rolled mats of fibers are arranged, in which the fibers may be crossed in an angle between 1 and 5~. The blood flows in the fibers.
The known hollow fiber oxygenators exhibit a number of disadvantages depending on their construction. They are bully, have a short blood flow path through the oxygenator and have, thus, a small contact zone for the blood and the gas and consequently a short residence time for the blood in the oxygenator which leads to a poor gas exchange rate. Blood and gas pressure drops may occur as well as channelling of blood or stagna-tion of blood in certain areas of the contact zone between blood and gas.
The invention It is thus one object of the invention to provide a blood oxygenator of a small construction size but retaining a high gas çY~h~nge rate.
A further object of this invention is to provide a blood o~ygenator which is of simple construction, allowing in particular a simple arrangement on and application to a core of hollow fibers.
A further object of this invention is to provide a blood axygenator allowing a improved contact of blood and gas.
A further object of this invention is to provide a blood oxygenator in s which the channeling of blood and areas of blood st~gn~tion are avoid-ed.
Still a further object of the present invention is to provide a blood oxygenator which exhibits a low pressure drop of the blood flowing o through the oxygenator.
These and other objects, advantages, details, features and embodiments of this invention will become apparent to those skilled in the art from the following detailed description of the invention, the appended claims, s the drawings, and the examples.
In accordance with this invention a hollow fiber oxygenator is provided, which comprises a housing, comprising - a core wall and an outer wall spaced from the core wall thus forming a chamber between the walls, - at least one blood inlet to and at least one blood outlet from said chamber, - first and second caps closing the chamber at a first and, respec-tively, a second end thereof, one of the caps having at least one gas inlet, the other having at least one gas outlet associated therewith, selectively permeable continuous hollow fiber filaments extending inside the chamber between the first cap and the second cap, wherein the ends of the fibers are sealed between the core wall and the outer wall at the ends of the chamber spaced from the caps, thus leaving a header space between the se~lingc and the caps, W O 97/08933 PCT~US96/14148 the ends of the fibers being open, wherein the circumferential angle difference for the fibers between the two sealings is between 0~ and 180~.
s ~n a preferred embodiment, the fibers are arranged in a first plurality of fibers and in a second plurality of fibers, wherein the first plurality of the fibers and the second plurality of the fibers have the same directio-nal sense but different circumferential angle differences, the length of the fibers of the first pluraliy of fibers being different o from the length of the fibers of the second plurality of fibers.
In prior art devices the fibers have been wound around the core in a technique similar to winding yarn on a bobbin (continuous rotation of the core coupled with oscill~ting axial movement of the fiber guide also known as cross winding). Thereby the circumferential angle difference of a given fiber between the two sealings was always well above 360~, frequently involved several full rotations, i.e. multiples of 360~. This prior art procedure had the disadvantage that a wrapping process and thus very long fibers between the se~lings was required. The present invention avoids this drawback and allows the use of much shorter fibers as well as a simpler production of the oxygenator.
Furthermore in accordance with this invention a hollow fiber oxygenator is provided, which comprises a housing, comprising 2s - a core wall and an outer wall spaced from the core wall thus forming a chamber between the walls, - at least one blood inlet to and at least one blood outlet from said chamber, -W O 97/08933 PCT~US96/1~148 - first and second caps closing the chamber at a first and, respec-tively, a second end thereof, one of the caps having at least one gas inlet, the other having at least one gas outlet associated therewith, selectively permeable continuous hollow fiber filaments extending inside the chamber between the first cap and the second cap, wherein the ends of the fibers are sealed between the core wall and the outer wall at the ends of the chamber spaced from the caps, thus leaving a header space between the sealings and the caps, the ends of the fibers being open, o wherein at least one partitioning wall is located between the core wall and the outer wall spaced therefrom, extending from one of the sealings towards the other sealing, thus dividing the chamber into sections, having a flow connection between the sections in the vicinity of the other sealing, allowing for counter-current flow of S blood and gas in one section and co-current flow of blood and gas in another section.
By the specific arrangement of the fibers and/or the partitioning wall the residence time of the blood inside the oxygenator is increased, thereby ~o improving the gas ç~r~h~nge rate of the oxygenator. By the specific orientation of the fibers inside the oxygenator a longer flow path of the blood is achieved which results in a better gas transfer, a longer residen-ce time and thus a smaller construction size of the whole oxygenator arrangement while retaining the same performance or even improved 2s performance. With the specific arrangement of the fibers and the blood flow path through the oxygenator no channeling of blood occurs, areas of blood stagnation are avoided and the pressure drop for the blood is rather low, thus allowing a treatment of the blood under moderate conditions which prevent or reduce the damage of the components of the blood. The specific arrangement of fibers allows a very simple W O 97/08~33 PCT~US96/14148 construction of the blood oxygenator, especially a very simple arrange-ment of the fibers around the core of the oxygenator. ~n the following preferred embodiments of this invention will be described with reference to the drawings in which s Fig. 1 is a perspective view of an assembled oxygenator according to the present invention with a partly cross-sectional view;
Fig. 2 is a perspective view of a second preferred embodiment of an assembled oxygenator according to the present invention with a o partly cross sectional view;
Fig. 3 is a cross-sectional view of a second preferred embodiment of the oxygenator according to the present invention of Fig. 2; and Fig. 4 is a perspective view of a hollow fiber arrangement according to the present invention;
15 Fig. 5 is a perspective view of a hollow fiber arrangement according to the present invention showing the blood flow path through the fiber filaments and gives an illustration of the definitions of fiber directions.
Housing The housing of the oxygenator according to the present invention may be formed of any suitable material which does not adversely interfere with 2s the blood and the free oxygen cont~ining gas, flowing through the oxygenator, respectively. Suitable materials include, but are not limited to, glass, ceramics, metals and alloys as well as polymeric materials like polycarbonate, polyesters, polyacrylates and polymethacrylates. Copolymers and mixtures of polymers are suitable as well. The preferred materials are polymeric m~teri~ls and alloys thereof.
W O 97/08933 PCT~US96/14148 The housing of the oxygenator comprises a core wall which may be of any desirable shape. The core wall may be of cylindrical form. It may have a circular or polygonal cross-section. Preferably, the core wall has a cylindrical shape with a circular cross-section, the diameter being s approximately equal to the height of the cylinder.
The oxygenator further comprises an outer wall which is spaced from the core wall, thus forming a chamber between the walls. Preferably outer wall and core wall are parallel to each other leaving a space of equal o width in between. Thus, the chamber may be annular, in particular having a circular or polygonal cross section. In the preferred embodiment the outer wall forms a cylinder of circular cross-section surrounding the core cylinder and leaving a chamber in between. In a preferred embodi-ment the inner core has an outer diameter of 100 to 104 mm and a lS height of 130 to 150 mm, the outer wall having an inner diameter of 132 to 134 mm. Thus, between the two cylinders there is an ~nn~ r space with a width of 13 to 17 mm.
In the walls at least one blood inlet to and at least one blood outlet from the chamber are formed. The blood inlet and the blood outlet may be formed in the core wall or in the outer wall or in both walls. The blood inlet and the blood outlet may be located at opposite ends of the core wall or the outer wall or at the same ends, respectively.
2s In the preferred embodiment as depicted in Fig. 1 the blood inlet is formed in the bottom section of the core wall. Preferably, a plurality of blood inlets are formed at the circumference of the chamber or of the core wall so that blood being introduced in the space between the core wall and the outer wall may be evenly distributed around the circumfer-ence at the bottom of the core wall.
W O 97/08933 PCTrUS96/141 According to the preferred embodiment depicted in Fig. 1 the blood outlet is formed at the outside of the outer wall at the top thereof.
Like for the blood inlet a plurality of outlets are located at the circum-ference of the chamber, especially of the top of the outer wall. Thereby the blood is removed from the space between the core wall and the outer wall evenly distributed around the circumference of the outer wall.
lBy this arrangement the blood flows principally axially through the space between the core wall and the outer wall.
o According to another preferred embodiment the blood inlet and the blood outlet may be respectively located at the same ends of the core wall and the outer wall.
In the preferred embodiment depicted in Fig. 2 and 3 the blood outletss are arranged in the same manner as in the embodiment of Fig. 1 with the difference that the outlets are located at the bottom of the outer wall.
The chamber formed between the core wall and the outer wall is closed by first and second caps at a first and, respectively, a second end there-of. The caps may be integrally formed in the core wall and the outer wall but may as well be formed separately and joined to the core wall and the outer wall at a later stage.
2s In the caps there are at least one gas inlet and at least one gas outlet formed which may be connected with tubings for feeding and withdraw-ing a gas, preferably a free oxygen cont~ining gas. In the preferred embodiment in Fig. 2 and 3 the gas inlet is formed in the top cap and the gas outlet is formed in the bottom cap.
-W O 97/08933 PCT~US96/14148 Apart from the gas inlet, the gas outlet, the blood inlet and the bloodoutlet further connections may be provided in the core wall, the outer wall, or the caps in order to introduce e.g. means for measuring the temperature of the blood or to withdraw blood test samples.
WO 97/08933 PCT~US96/14148 Hollow fibers The hollow fibers or hollow fiber filaments used in this invention may be any fibers that are selectively permeable and have continuous lumens therethrough.
The fibers are preferably made of polypropylene which has been modi-fied by silicones or other types of polymers.
o The hollow fiber filaments may have any desirable diameter, with an outer diameter of from 365 to 400 ,(Lm preferred, from 365 to 380 ~m being especially preferred. Useful hollow fiber filaments are commercially available from AKZO and CELANESE companies and under the name oxiphan and celgard, respectively.
Another preferred hollow fiber is a microporous polypropylene hollow fiber with an inner diameter of 50 ~lm, an external diameter of 280 ~Lm, an average pore size of 0,04 ~Lm and a porosity of 50~o.
~0 lHollow fiber arrangement The selectively permeable continuous hollow fiber filaments extend inside the chamber between the first cap and the second cap. In a preferred 2s embodiment the hollow fibers substantially fill the chamber between the core wall and the outer wall.
The ends of the fibers are sealed between the core wall and the outer wall at the ends of the chamber spaced from the caps, thus leaving a header space between the se~lingc and the caps. The ends of the fibers W O 97/08933 PCT~US96/14148 - 12 -are open, so that gas m~y flow from the gas inlet of one of the caps through the fibers and finally through the gas outlet in the other cap.
~ n the preferred embodiment depicted in Fig. 1 the fibers are arranged in the chamber in such a way that the circumferential angle difference for the fibers between the two sealings is between 0~ and 180~. The term "circumferential angle difference" describes the angle through which the core must be turned around its longitudinal axis in order to arrive from one sealing of the hollow fiber to the other sealing of the hollow lO fiber. It may also be described as the angle between the projections of the longitudinal aYis of the core, the first sealing point of the fiber and the second sealing point of the fiber into a plane which is perpendicular to the longitudinal axis of the core. Fig. S illustrates the term "circumferential angle difference".
This circumferential angle difference is between 0~ and 180~ for the fibers, preferably between 0~ and 90~.
The hollow fibers are divided into a first plurality of fibers and a second plurality of fibers. Both pluralities of fibers have the same direc-tional sense with respect to the circumferential angle difference formed by them, but they have different circumferential angle differences. This means that the path of one of the pluralities of fibers from one sealing to the other sealing is steeper than the path of the other plurality of fibers.
Furthermore, the length of the fibers of the first plurality of fibers is different from the length of the fibers of the second plurality of fibers.
This is a result of the path of one of the plurality of fibers being steeper than the path of the other plurality of fibers. Thus, one plurality of fibers has a longer path from one sealing to the other sealing thus forming a different length of this plurality of fibers from the other plurality of fibers. Preferably, the filaments in each of the plurality of fibers are parallel to each other and pass from one sealing to the other s sealing substantially without any additional curves or bends. In this way the steeper plurality of fibers necessarily has a smaller length between the se~lings than the less steeper plurality of fibers.
With a circumferential angle difference of 0~ the fiber filaments extend 10 principally parallel to the longitudinal axis of the core from one sealing to the other sealing. With a circumferential angle difference of 180~ the fibers pass halfway around the core on their way from one sealing to the other sealing. Thus, none of the fibers passes more than halfway around the core of the oxygenator chamber.
In the oxygenators according to the state of the art usually a plurality of fibers is wound around the core in a helical fashion. At the end of the core the winding direction is reversed but the winding sense is m~int~ined. ThUs, the winding of the fibers on the core is similar to a ~o yarn winding operation wherein the yarn is passed up and down on the turning core on which it is wound. This manner of winding fibers around the core has several restrictions: each fiber must be wound around the core several times in order to fix it to the core. Thus, usually the circurnferential angle difference for the fibers between the se~lingc is a ~s multiple of 360~. This large circumferential angle difference is necessary to fix the fibers on the core when ~he winding direction of the fiber is ~ reversed at the end of the core. Otherwise, the fibers would fall off the core. The reversal of the winding direction but not of the winding sense leads necessarily to an arrangement of fibers in which (after cutting the fibers in the region of the se~lingc) one plurality of the fibers has one W O 97/08933 PCTrUS96/14148 directional sense on the core and one circumferential angle difference, and a second plurality of fibers has the opposite directional sense around the core and the same circumferential angle difference but in the oppo-site directional sense.
Consequently it is not possible to arrange fibers around the core with a circumferential angle difference being less than 180~ (for practical reasons not less than at least several hundred degrees). Furthermore, it is not possible that two pluralities of fibers have the same directional sense but o different circumferential angle differences since the arrangement of the second plurality of fibers is just the reversed arrangement of the first plurality of fibers, thus always leading to the same circumferential angle difference but different directional senses.
s As a consequence the hollow fiber arrangement according to the first embodiment of the present invention cannot be obtained by rotating the core and winding the filaments from a continuous roll of filaments onto the core by reversing the feed direction of the filament at the top and bottom ends of the core, since this process for m;lnl~f~cturing the fiber ~o mat is only applicable when the second plurality of the fibers are wound in the other sense with respect to the first plurality. In a preferred embodiment of the present invention the circumferential angle differences of the first plurality of fibers and the second plurality of fibers differ by at least 5~.
2s The direction of the fibers around the core may be further described by the inclination angle between the fiber filaments and the longitudinal axis of the core. If this inclin~tion angle amounts to 0~, the fiber fila-ments are principally parallel to the longitudinal axis of the core. When this angle is 90~, the fibers run around the core in one plane each with which is perpendicular to the longitudinal axis of the core. According to a first embodiment of the present invention the preferably parallel fibers of the first plurality of fibers have an inclination angle with the longitu-~ dinal axis of the core of less than 90~ and the preferably parallel fibers of the second plurality of fibers have an inclination angle with the longitudinal axis of the core of between 0~ and the inclination angle of the fibers of the first plurality of fibers. Thus, the two pluralities of fibers have different inclination angles with respect to the longitudinal axis of the core. This is shown in Fig. 4.
Preferably the fibers of the first plurality of fibers have an inclinationangle with the longitudinal axis of ~he core of from 10~ to 40~ and the fibers of the second plurality of fibers have an inclination angle with the longitudinal axis of the core of between 0~ and the inclination angle of the fibers of the first plurality of fibers. In a further preferred embodi-ment the fibers of the first plurality of fibers have an inclination angle of from 10~ to 25~, especially 10~ to 20~, and the fibers of the second plurality of fibers have an inclinatio~ angle of from 0~ to 7~, preferably 0~ to 4~, more preferably 2~ to 4~. In an especially preferred embodi-ment, the pluralities of fibers have an inclination angle of 12~ and 4~,respectively.
The hollow fiber filament filling of the chamber may be achieved by arranging continuous strips of layers of fiber filaments around the core ~s with the proviso that the axial width of said strips is longer than the axial distance between the sealings. Thus, continuous strips of layers of fiber filaments are formed and then these strips are in a second step arranged around the core, e.g. by spirally winding the continuous strip around the core. Since the axial width of the strips is longer than the axial distance between the se~lin~.s, the continuous strip need not be CA 02229843 1998-02-l9 W O 97/08933 PCT~US96/14148 - 16 -wound helically around the core which would involve passing the feed of the continuous strips along the longitudinal axis of the core. Thus, the arrangement of the continuous strips of layers of fiber filaments is much simpler in comparison to the yarn spool-like winding of the fibers ac-s cording to the state of the art.
According to a preferred embodiment of the present invention twocontinuous strips of layers of fiber filaments are arranged around the core, wherein the strips have two parallel edges between which at least o one layer of parallel spaced fiber filaments extends being inclined with respect to the parallel edges, wherein one strip contains the first plurality of parallel fibers with the first inclination angle and the second strip contains the second plurality of parallel fibers having the second inclina-tion angle. The strips may have single layers of the fiber filaments and the two strips may be arranged around the core in a manner that contiguous layers of the core in radial directions have different inclina-tion angles. This is indicated in Fig. 4.
The hollow fiber filament filling of the chamber may as well be achie-ved by successive layers of short single layer woven mats of the fiberfilaments.
In these embodiments strips of mats of single layers of fiber filaments are prepared by first arranging a layer of long parallel fibers substantial-2s Iy equally spaced from each other which are then fixed in their positionby a connecting element, preferably a cross thread which is a flexible small diameter monofilament. The thread must be sufficiently flexible to be easily bent around the hollow fibers. Furthermore, it must have sufficient tensile strength and tension to fix the filaments in their posi-, W O 97/08933 PCT~US96/14148 - 17 -tion, like in known tissues of clothes. This monofilament allows a regular spacing between the short single fiber filaments.
The essentially parallel fibers in each of the strips are spaced from each other by preferably 0,8 to 1,2 fiber diameters. The connecting element, preferably the thin filament-like connector or cross-thread is arranged transversely in all fibers of the strip in said strips or parallel to the upper and lower edges thereof.
o In the embodiment of the present invention depicted in Fig. 2 and 3 a known hollow fiber filament filling may be applied in which the hollow fiber filaments extend inside the chamber between the first cap and the second cap. The circumferential angle difference of the fiber filaments between the sealings is not restricted and the directional sense of the fibers is not restricted either. However, a partitioning wall described below has to be provided in this embodiment.
The hollow fiber filaments may be cross wound around the core as it is known from the prior art. This results in a first plurality of fibers being wound in one sense around the core, having one inclination angle, a second plurality of fibers, being wound around the core in the opposite sense, having the opposite inclination angle. The circurnferential angle differences are the same for both pluralities of fibers and this difference exceeds 360~.
Preferably the hollow fiber filaments have the arrangement described above for the first embodiment.
The hollow fibers are sealed in the space between the core wall and the outer wall at the top and the bottom thereof the ends of the filaments W O 97/08933 PCT~US96/14148 being open so that a gas can flow through the fiber filaments. Prefera-bly, the fibers are sealed with a polymeric resin which has the same thermal expansion coefficient as the hollow fibers and the housing.
Useful resins are polyurethane resins, wherein epoxy resins are preferred.
s The resin sealing of the filaments is such that a chamber is formed between the core wall, the outer wall and the resin se~lin~s in which chamber blood can flow but not penetrate the se~lingc. In the preferred embodiment the sealings are arranged in such a way that between the caps and the sealings a header space is left for the introduction or 10 removal of the free oxygen containing gas. Furthermore, the se~lin~c are arranged in such a way that the blood inlets and blood outlets are arranged in the walls inside the chamber formed by the core wall, the outer wall and the se~lingc Partitioning wall According to one aspect of the present invention a partitioning wall is provided between the core wall and the outer wall in a spaced position therefrom, which extends from one sealing towards the other sealing, thus forming sections in the chamber. The sections have a flow connec-tion in the vicinity of the other sealing. The flow connection in the vicinity of the other sealing may be provided in several ways. The partitioning wall may extend into the other sealing being sealed there 2s and exhibiting apertures in the vicinity of this other sealing. Annular slits may be provided in this partitioning wall. On the other hand, the whole partitioning wall may extend only to a distance from the other sealing thus leaving an ~nn~ r space between the end of the partitioning wall and the sealing. The size of this space or the size of the holes or ~nn~ r slits m~y be varied depending on the flow conditions of the W O 97t08933 PCT~US96/14148 blood. If flow restrictions shall be irnposed on the blood, the distance or holes or slits may be formed small. Preferably, the distance or slits or holes are so big that they do not affect the flow properties of the blood ~ and do not impose a pressure drop on the blood. By this arrangements the chamber is divided into sections for counter-current flow of blood and gas and co-current flow of blood and gas, respectively.
The partitioning wall may be provided in each of the embodiments of the present invention, i.e. in connection with a hollow fiber filament o arrangement in which the circumferential angle difference for the fibers between the sealings of the chamber is between 0~ and 180~, wherein the first plurality of the fibers and the second plurality of the fibers have the same directional sense but different circumferential angle differences, the length of the fibers of the first plurality of fibers being different from the length of the fibers of the second plurality of fibers or in an arrangement in which the hollow fiber filaments extend inside the chamber between the first cap and the second cap.
Preferably, the partitioning wall is combined with the first arrangement ~o of hollow fiber filaments. Preferably at least one partitioning wall extends from one of the sealings of the chamber to a position spaced from the other sealing of the chamber.
With respect to Fig. 2 and 3 one partitioning wall is provided in the 2s oxygenator. The partitioning wall is arranged cylindrically between the core wall and the outer wall and sealed in the bottom sealing. The partitioning wall extends to a position spaced from the top sealing.
The partitioning wall may consist of any appropriate material, e.g. sheets of polymeric material like polyethylene, polypropylene, polycarbonate or W O 97/08933 PCT~US96/14148 - 2n -polymethacrylate. The preferred material is polycarbonate. The partition-ing wall may have a thickness of from S to 12 ,um, preferably 8 to 10 ,lLm. The partitioning wall divides the ~nnnl~r chamber into two sections through which the blood is passed. The two sections of the ~nnnl~r s chamber may have different sizes depending on the position of the partitioning wall between the core wall and the outer wall. The partitioning wall may be located in the center of the chamber, thus forming two sections of equal thickness, but depending on the desired flow properties or desired gas exchange properties the partitioning wall o may be located nearer to the core wall or nearer to the outer wall. The position of the partitioning wall can affect the oxygenation results when passing blood through the chamber. By locating the partitioning wall nearer to the outer wall two sections of appr xim~tely equal volume may be obtained whereas by locating the partitioning wall in the center of S the chamber two sections of different volume are obtained. The blood entering the chamber at the bottom of the core wall first flows upwardly to the top sealing of the chamber in a counter-current to the gas flow.
At a position near the top sealing of the chamber the flow direction of the blood is reversed and it flows downwardly to the bottom sealing in the second section, thus co-current with the gas flow. The blood leaves the chamber at the blood outlet. By this arrangement the blood path through the chamber is apprnxim~tely doubled. Furthermore, the blood flow is not only co-current or counter-current with the gas flow but counter-current and co-current with the gas flow. This leads to an en-zs hanced gas e~rh~nge rate between blood and gas.
Further partitioning walls being sealed in the bottom sealing or top sealing may be arranged inside the chamber to further enlarge the flow path of the blood and enhance the gas exchange rate. In connection with the partitioning wall the ,mn~ r chamber m~y be filled with the CA 02229843 l998-02-l9 W O 97/08933 PCT~US96/14148 hollow fiber filaments in an arrangement wherein the fibers of the first plurality of fibers have an inclination angle with the longitudinal axis of the core of less than 90~ and the fibers of the second plurality of fibers have an inclination angle with the longitudinal axis of the core of s between 0~ and the inclination ~ngle of the fibers of the first plurality of fibers, preferably 10~ to 25~ and 0~ to 7~, respectively.
Best results are obtained when the fibers are arranged in the latter manner, especially at angles of 4~ and 12~, respectively.
Heat ~Y~h~nger Optionally the blood inlet of the hollow fiber oxygenator according to the present invention may be provided with a heat t-~rh:~nger for con-trolling the temperature of the incoming blood. According to the prefer-red embodiments depicted in Figs. 1 to 3 the heat ~Yrhz~nger is located in the bottom of the oxygenator inside the core of the o~ygenator. It comprises a plurality of metal tubes in which a heat e~r~ nging fluid is ~o circulated. The blood is passed along the outsides of the metal tubes which are spaced from each other. The fluid used to control the tempe-rature inside the heat exch~nger is preferably water.
2s Method for o~ygen~ti~g blood According to the present invention a method for oxygenating blood is provided, comprising passing a free oxygen cont~ining gas through a plurality of hollow fiber filaments extending principally axially through an oxygenator chamber and passing blood through the oxygenator chamber, wherein the blood flows primarily axially through the chamber along the plurality of fibers, characterized in that the fibers are arranged in such a way that they cause integrally a helical flow of the blood around the axis of the chamber.
According to a second embodiment of the present invention a method for oxygenating blood is provided, comprising passing a free oxygen containing gas through a plurality of hollow fiber filaments extending principally axially through an oxygenator chamber and passing blood o through the oxygenator chamber, wherein blood flows primarily axially through the chamber along the plurality of fibers, characterized in that the blood in the first section of said chamber flows essentially in the opposite direction as the flow of the free oxygen cont~ining gas through the fibers in said first section and that the blood in a second section of S said chamber flows essentially in the same direction as the flow of the free oxygen containing gas through the fibers in said second section.
According to another embodiment of the present invention a method for oxygenating blood is provided, comprising passing blood via blood inlet ~o and blood outlet through the oxygenator as described above and passing a free oxygen containing gas via the gas inlet and gas outlet through the oxygenator, and optionally controlling the temperature of the blood, in particular with the proviso that the method is not used for therapeutical treatment of the human or animal body.
Operating conditions s The gas used in the hollow fiber oxygenator according to the present invention may be any gas containing free oxygen which is apt to transfer oxygen through the semipermeable hollow fibers into the blood and to receive carbon dioxide from the blood. Preferably, the gas should have a free oxygen content of from 21 to 100 vol~O, preferably from 60 to 90 10 vol~. The preferred gas is air, which has an oxygen content of 21%, preferably mixed with a second free oxygen containing gas, so that the preferred oxygen content of from 60 to 90 vol.~o is obtained. The gas pressure difference applied at the gas inlet and gas outlet may be from 0 to 13,3 kPa, preferably from 0 to 4 kPa. This results in a gas flow of S from 0,2 to 10 l/min. for a preferred embodiment of the oxygenator according to the present invention as depicted in Figs. 1 to 3.
To be useful in a cardiopulmonary bloodstream circulation of a human body the blood flow through the oxygenator must be in the range of from 1 to 6 I/min. In the blood ~xygenator according to the present invention the blood flow may be arranged from 0,2 to 6 I/min., prefera-bly from 1 to 6 l/min. To effect this blood flow a pressure difference of from 8 to 27 kPa must be applied between the blood inlet and the blood outlet. With a blood flow of 6 l/min. the typical residence time of the blood inside the hollow fiber oxygenator according to the present invention is 1/6 min. The flow path of the blood along the hollow fibers is approxim~tely 180 mm. Details of the blood flow path can be seen in Fig. 5. Without being bound to any theory it is believed that the blood flows along the hollow filament fibers helically around the axis of the W O 97/08933 PCT~US96/14148 chamber. This ensures an effective contact of the blood with the outer surface of the hollow fibers resulting in an improved oxygen eY~h~nge.
In comparison to the known blood oxygenators the hollow fiber blood oxygenator according to the present invention exhibits a high gas ex-change rate while having a small size of the chamber filled with hollow filament fibers. No channeling of blood is observed in the oxygenator according to the present invention nor are areas of blood stagnation observed. The pressure drop of the blood flowing through the oxygenator 10 lS low.
The following examples demonstrate the advantages of the hollow fiber oxygenator according to the present invention with regard to the prefer-red embodiments.
Example 1 A hollow fiber blood oxygenator according to Fig. 1 was assembled by ~o using 3,2 up to 3,6 m2 of the hollow filament fibers m~nllf~ctllred by AKZO ENKA GROUP to fill the annual chamber between the core wall and the outer wall. One half of the filaments were arranged with an inclination angle of 4~ respect to the lonEit--~lin:~l axis of the core and the other half of the fibers were arranged around the core with an 25 inclin~tion angle of 12~ with respect to the lonEitu~1in~l axis of the core.
This corresponds to circumferential angle difference of 8~ and 25~, respectively. Two strips of fibers each having one of the different inclina-tion angles were arranged in the chamber. The blood oxygenator was used to treat the blood coming from a patient in an extracorporeal circulation having an initial oxygen content of l l ml/dl and an initial carbon dioxide content of 55 rnl/dl. The applied blood pressure differ-ence was 26,6 kPa and the applied pressure difference for the air was 4 kPa. Thus, flow rates for the gas were 6 l/min. and 6 l/min. for the blood. The blood leaving the oxygenator had an oxygen content of 19,3 s ml/dl and a carbon dioxide content of 50 ml/dl. Thus, the blood oxy-genator according to the present invention showed a superior gas ex-change rate. No stagnation or channeling of blood and no agglomeration of blood particles was observed.
~xample 2 A hollow fiber blood oxygenator was arranged according to Fig. 2 and 3 by using hollow filament fiber, m~nuf~ctured by the AKZo ENKA
GROUP. The annual chamber was filled with the fibers by cross winding.
~urther experimental conditions were as follows:
A partitioning wall made of polypropylene was inserted in the annual chamber equally spaced to the outer wall at a distance of 7 - 8 mm.
The partitioning wall was sealed in the bottom sealing of the chamber.
I~ extended parallel to the outer and core wall and terminated at a distance of 13 - 15 mm from the top sealing.
The blood oxygenator according to example 2 showed a high gas ex-change rate. No channeling or stagnation of blood was observed.
W O 97/08933 PCT~US96/14148 E~ample 3 A hollow fiber blood oxygenator was arranged according to Fig. 2 and 5 3 by using hollow filament fiber, In~nl~f~ctured by the AKZO ENKA
GROUP. The annual chamber was filled with the fibers by the same method as applied in example 1. Further experimental conditions were as follows:
o A partitioning wall made of polypropylene was inserted in the annual chamber equally spaced to the outer wall at a distance of 7 - 8 mm.
The partitioning wall was sealed in the bottom sealing of the chamber.
It extended parallel to the outer and core wall and terminated at a distance of 13 - 15 mm from the top sealing.
The blood oxygenator according to example 3 showed a high gas ex-change rate. No channeling or stagnation of blood was observed.
20 Example 4 (Comparative example) A commercially available hollow fiber blood oxygenator (DIDECO 7003 ITALIA~ COMPANY) was used in a comparative experiment. Experimental conditions were as follows:
Blood in: CO2 content = 60 ml/dl ~2 content = 11.2 ml/dl Blood out: COz content = 54 ml/dl ~2 content = 17,6 ml/dl W O 97/08933 PCT~US96/14148 The pressure drop for the blood was 22,6 kPa. The flow rate for the gas was 6 I/min. and the flow rate for the blood was 6 I/rnin.
The results from Examples 1, 2 and 3 and comparative Example 4 show s that the specific arrangement of hollow fiber filaments inside the hollow fiber blood o~ygenator according to the present invention results in an improvement of gas e~ch~nge rate, while preventing channelling or stagnation of blood.
Claims (31)
1. Hollow fiber oxygenator, comprising a housing, comprising - a core wall and an outer wall spaced from the core wall thus forming a chamber between the walls, - at least one blood inlet to and at least one blood outlet from said chamber, - first and second caps closing the chamber at a first and, respectively, a second end thereof, one of the caps having at least one gas inlet, the other having at least one gas outlet associated therewith, selectively permeable continuous hollow fiber filaments extending inside the chamber between the first cap and the second cap, wherein the ends of the fibers are sealed between the core wall and the outer wall at the ends of the chamber spaced from the caps, thus leaving a header space between the sealings and the caps, the ends of the fibers being open, wherein the circumferential angle difference for the fibers between the two sealings is between 0° and 180°.
2. Hollow fiber oxygenator according to claim 1, wherein a first plurality of parallel fibers and a second plurality of parallel fibers have the same directional sense but different circumferential angle differences, the length of the fibers of the first plurality of parallel fibers being different from the length of the fibers of the second plurality of parallel fibers.
3. Hollow fiber oxygenator according to claim 1 or 2, wherein the circumferential angle difference is between 0° and 90°.
4. Hollow fiber oxygenator according to one of the preceding claims, wherein the circumferential angle differences of the first plurality of fibers and the second plurality of fibers differ by at least 5°.
5. Hollow fiber oxygenator according to one of the preceding claims, wherein the fibers of the first plurality of parallel fibers have an inclination angle with the longitudinal axis of the core of less than 90° and the fibers of the second plurality of parallel fibers have an inclination angle with the longitudinal axis of the core of between 0° and the inclination angle of the fibers of the first plurality of parallel fibers.
6. Hollow fiber oxygenator according to claim 4, wherein the fibers of the first plurality of fibers have an inclination angle with the longitudinal axis of the core of from 5° to 50° and the fibers of the second plurality of fibers have an inclination angle with the longitudinal axis of the core of between 0° and the inclination angle ofthe fibers of the first plurality of fibers.
7. Hollow fiber oxygenator according to claim 5, wherein the fibers of the first plurality of fibers have an inclination angle with the longitudinal axis of the core of from 10° to 25° and the fibers of the second plurality of fibers have an inclination angle with the longitudinal axis of the core of from 0° to 7°.
8. Hollow fiber oxygenator, comprising a housing, comprising - a core wall and an outer wall spaced from the core wall thus forming a chamber between the walls, - at least one blood inlet to and at least one blood outlet from said chamber, - first and second caps closing the chamber at a first and, respectively, a second end thereof, one of the caps having at least one gas inlet, the other having at least one gas outlet associated therewith, selectively permeable continuous hollow fiber filaments extending inside the chamber between the first cap and the second cap, wherein the ends of the fibers are sealed between the core wall and the outer wall at the ends of the chamber spaced from the caps, thus leaving a header space between the sealings and the caps, the ends of the fibers being open, wherein at least one partitioning wall is located between the core wall and the outer wall spaced therefrom, extending from one of the sealings towards the other sealing, thus dividing the chamber into sections, having a flow connection between the sections in the vicinity of the other sealing, allowing for substantially counter-current flow of blood and gas in one section and for co-current flow of blood and gas in another section.
9. Hollow fiber oxygenator according to one of claims 1 to 6, wherein at least one partitioning wall is located between the core wall and the outer wall spaced therefrom, extending from one of the sealings towards the other sealing, thus dividing the chamber in at least two sections, having a flow connection between the sections in the vicinity of the other sealing, allowing for counter-current flow of blood and gas in one section and co-current flow of blood and gas in another section.
10. Hollow fiber oxygenator according to claim 8 or claim 9, wherein the at least one partitioning wall extends from one of the sealings to a position spaced from the other sealing.
11. Hollow fiber oxygenator according to one of the preceding claims, wherein the hollow fiber filaments substantially fill the chamber.
12. Hollow fiber oxygenator according to one of the preceding claims, wherein continuous strips of layers of fiber filaments are arranged around the core with the proviso that the axial width of said strips is longer than the axial free distance between the sealings.
13. Hollow fiber oxygenator according to claim 11, wherein two continuous strips of layers of fiber filaments are arranged around the core, wherein the strips have two parallel edges between which at least one layer of parallel spaced fiber filaments extends being inclined with respect to the parallel edges, wherein one strip contains the first plurality of parallel fibers with the first inclination angle and the second strip contains the second plurality of parallel fibers having the second inclination angle.
14. Hollow fiber oxygenator according to claim 11 or 12, wherein the strips have single layers of the fiber filaments and contiguous layers of the core (in radial direction) have different inclination angles.
15. Hollow fiber oxygenator according to one of claims 1 to 6, wherein the blood inlet and the blood outlet are located at opposite ends of the core wall or the outer wall.
16. Hollow fiber oxygenator according to one of claims 7 or 8, wherein the blood inlet and the blood outlet are respectively located at the same ends of the core wall and the outer wall.
17. Hollow fiber oxygenator according to claim 15, wherein the blood inlet is located at the bottom of the core wall and the blood outlet is located at the bottom of the outer wall.
18. Hollow fiber oxygenator according to one of the preceding claims, wherein a plurality of blood inlets and blood outlets are located along the circumference of the chamber.
19. Hollow fiber oxygenator according to one of the preceding claims, wherein the gas inlet is located in the top cap and the gas outlet is located in the bottom cap.
20. Hollow fiber oxygenator according to claim 7 or 8 or a claim referring to claim 7 or 8, wherein the partitioning wall extends from the bottom sealing to a position spaced from the top sealing.
21. Hollow fiber oxygenator according to one of the preceding claims, wherein the chamber is annular, in particular has a circular cross-section.
22. Hollow fiber oxygenator according to one of claims 1 to 19, wherein the chamber has a polygonal cross section.
23. Hollow fiber oxygenator according to one of the preceding claims, wherein the fibers are microporous polypropylene hollow fibers with an inner diameter of 50 µm, an external diameter of 280 µm, an average pore size of 0,04 µm and a porosity of 50%.
24. Hollow fiber oxygenator according to one of the preceding claims, further comprising an integral heat exchanger for controlling the temperature of the blood.
25. Hollow fiber oxygenator according to one of the preceding claims, wherein said fibers are arranged in at least one strip having a width greater than the axial free distance between the sealing and wherein said fibers in one strip are essentially parallel to each other spaced from each other, preferably 0,8 to 1,2 fiber diameters, and are held together by one or more connecting elements, preferably thin filament-like connectors, arranged transversally in all fibers of the strip in said strips.
26. Hollow fiber oxygenator according to claim 25, wherein 16,8 to 18,5 fibers are arranged per cm of length of said strips.
27. Hollow fiber oxygenator according to claim 1, wherein the fibers are cross wound around the core, wherein a first plurality of the fibers is cross wound around the core in one sense and a second plurality of the fibers is cross wound around the core in the opposite sense.
28. Hollow fiber oxygenator according to one of claims 1 to 11 and 15 to 24, wherein the fibers are arranged as one or more fiber mats, comprising parallel hollow fibers, preferably at least two groups of hollow fibers, wherein said parallel fibers of said mats are held in place relative to each other by one or more connecting elements, preferably thin filament-like connectors.
29. Method for oxygenating blood, comprising passing a free oxygen containing gas through a plurality of hollow fiber filaments extending principally axially through an oxygenator chamber and passing blood through the oxygenator chamber, wherein the blood flows primarily axially through the chamber along the plurality of fibers, characterized in that the fibers are arranged in such a way that they cause integrally a helical flow of the blood around the axis of the chamber.
30. Method for oxygenating blood, comprising passing a free oxygen containing gas through a plurality of hollow fiber filaments extending principally axially through an oxygenator chamber and passing blood through the oxygenator chamber, wherein blood flows primarily axially through the chamber along the plurality of fibers, characterized in that the blood in the first section of said chamber flows essentially in the opposite direction as the flow of the free oxygen containing gas through the fibers in said first section and that the blood in a second section of said chamber flows essentially in the same direction as the flow of the free oxygen containing gas through the fibers in said second section.
31. Method for oxygenating blood, comprising passing blood via blood inlet and blood outlet through the oxygenator according to one of claims 1 to 23 and passing a free oxygen containing gas via the gas inlet and gas outlet through the oxygenator, and optionally controlling the temperature of the blood, in particular with the proviso that the method is not used for therapeutical treatment of the human or animal body.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002229843A CA2229843A1 (en) | 1995-09-01 | 1996-08-29 | Hollow fiber oxygenator |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19532365.3 | 1995-09-01 | ||
| CA002229843A CA2229843A1 (en) | 1995-09-01 | 1996-08-29 | Hollow fiber oxygenator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2229843A1 true CA2229843A1 (en) | 1997-03-13 |
Family
ID=4162117
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002229843A Abandoned CA2229843A1 (en) | 1995-09-01 | 1996-08-29 | Hollow fiber oxygenator |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2229843A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109364314A (en) * | 2018-12-07 | 2019-02-22 | 江苏美思康医疗科技有限公司 | A kind of two-chamber membrane oxygenator and oxygen close method |
| CN112108011A (en) * | 2020-09-29 | 2020-12-22 | 杭州富阳万博空分设备有限公司 | Precision filter sealing shell and using method thereof |
-
1996
- 1996-08-29 CA CA002229843A patent/CA2229843A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109364314A (en) * | 2018-12-07 | 2019-02-22 | 江苏美思康医疗科技有限公司 | A kind of two-chamber membrane oxygenator and oxygen close method |
| CN109364314B (en) * | 2018-12-07 | 2023-10-24 | 江苏美思康医疗科技有限公司 | Double-cavity membrane type oxygenator and oxygenation method |
| CN112108011A (en) * | 2020-09-29 | 2020-12-22 | 杭州富阳万博空分设备有限公司 | Precision filter sealing shell and using method thereof |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |