CA2360406A1 - Bundle of hollow fibres for a device for extracorporeal treatment of blood and plasma, and process for its production - Google Patents
Bundle of hollow fibres for a device for extracorporeal treatment of blood and plasma, and process for its production Download PDFInfo
- Publication number
- CA2360406A1 CA2360406A1 CA002360406A CA2360406A CA2360406A1 CA 2360406 A1 CA2360406 A1 CA 2360406A1 CA 002360406 A CA002360406 A CA 002360406A CA 2360406 A CA2360406 A CA 2360406A CA 2360406 A1 CA2360406 A1 CA 2360406A1
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- Prior art keywords
- bundle
- hollow fibres
- fibres
- hollow
- hydraulic permeability
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- 239000008280 blood Substances 0.000 title claims abstract description 30
- 210000004369 blood Anatomy 0.000 title claims abstract description 30
- 238000000034 method Methods 0.000 title claims description 21
- 230000008569 process Effects 0.000 title claims description 16
- 238000004519 manufacturing process Methods 0.000 title abstract description 9
- 230000035699 permeability Effects 0.000 claims abstract description 89
- 239000012528 membrane Substances 0.000 claims abstract description 27
- 230000004087 circulation Effects 0.000 claims abstract description 21
- 239000000835 fiber Substances 0.000 claims description 38
- 238000002834 transmittance Methods 0.000 claims description 16
- 239000007788 liquid Substances 0.000 claims description 15
- 238000005259 measurement Methods 0.000 claims description 15
- 238000009826 distribution Methods 0.000 claims description 13
- 238000004804 winding Methods 0.000 claims description 7
- 239000000853 adhesive Substances 0.000 claims description 6
- 230000001070 adhesive effect Effects 0.000 claims description 6
- 238000006073 displacement reaction Methods 0.000 claims description 5
- 102000018832 Cytochromes Human genes 0.000 claims description 4
- 108010052832 Cytochromes Proteins 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 238000007789 sealing Methods 0.000 claims description 4
- 230000015572 biosynthetic process Effects 0.000 claims description 2
- 229920002492 poly(sulfone) Polymers 0.000 claims description 2
- 230000004907 flux Effects 0.000 description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- 238000001914 filtration Methods 0.000 description 8
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 5
- 239000000385 dialysis solution Substances 0.000 description 5
- 238000001125 extrusion Methods 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 239000003053 toxin Substances 0.000 description 4
- 231100000765 toxin Toxicity 0.000 description 4
- 108700012359 toxins Proteins 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 3
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 3
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 3
- 108090000623 proteins and genes Proteins 0.000 description 3
- 102000004169 proteins and genes Human genes 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- -1 alkyl radicals Chemical class 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000000502 dialysis Methods 0.000 description 2
- 230000001376 precipitating effect Effects 0.000 description 2
- 230000001698 pyrogenic effect Effects 0.000 description 2
- 230000001225 therapeutic effect Effects 0.000 description 2
- 238000000108 ultra-filtration Methods 0.000 description 2
- 208000001647 Renal Insufficiency Diseases 0.000 description 1
- 238000004026 adhesive bonding Methods 0.000 description 1
- 238000002617 apheresis Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 150000005840 aryl radicals Chemical class 0.000 description 1
- 230000017531 blood circulation Effects 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 229920002457 flexible plastic Polymers 0.000 description 1
- 238000002615 hemofiltration Methods 0.000 description 1
- 239000008240 homogeneous mixture Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 201000006370 kidney failure Diseases 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000000813 microbial effect Effects 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000001706 oxygenating effect Effects 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 238000002616 plasmapheresis Methods 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 230000001954 sterilising effect Effects 0.000 description 1
- 238000004659 sterilization and disinfection Methods 0.000 description 1
- 125000001174 sulfone group Chemical group 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000003809 water extraction Methods 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
- B01D63/031—Two or more types of hollow fibres within one bundle or within one potting or tube-sheet
-
- 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
-
- 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
- B01D63/021—Manufacturing thereof
-
- 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
- B01D63/021—Manufacturing thereof
- B01D63/0233—Manufacturing thereof forming the bundle
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
- B01D65/10—Testing of membranes or membrane apparatus; Detecting or repairing leaks
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
- G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2319/00—Membrane assemblies within one housing
- B01D2319/06—Use of membranes of different materials or properties within one module
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N2015/084—Testing filters
Abstract
The invention relates to a bundle of hollow fibres intended to constitute the membrane of a device for treating blood or plasma by extracorporeal circulation, in which:
.cndot. the hydraulic permeability of the hollow fibres in the bundle is heterogeneous; and .cndot. the ratio of the highest hydraulic permeability measured on some hollow fibres of the bundle to the lowest hydraulic permeability measured on other hollow fibres in the same bundle is at least about 5.
The invention also relates to a method for producing such a bundle, and a device comprising such a bundle.
.cndot. the hydraulic permeability of the hollow fibres in the bundle is heterogeneous; and .cndot. the ratio of the highest hydraulic permeability measured on some hollow fibres of the bundle to the lowest hydraulic permeability measured on other hollow fibres in the same bundle is at least about 5.
The invention also relates to a method for producing such a bundle, and a device comprising such a bundle.
Description
BUNDLE OF HOLLOW FIBRES FOR A DEVICE FOR EXTRACORPOREAL
TREATMENT OF BLOOD AND PLASMA, AND PROCESS FOR ITS
PRODUCTION
The present invention relates to a bundle of hollow fibres for a device for treating blood or plasma by extracorporeal circulation, and to a process for producing a bundle of hollow fibres constituting the semi-permeable membrane of the device.
Membrane devices for treating blood or plasma by extracorporeal circulation are 1 o used in many different medical or paramedical applications, such as treating renal insufficiency by dialysis or haemofiltration, plasmapheresis and apheresis for therapeutic and non-therapeutic purposes, oxygenating blood, immunopurification, etc.
In general, semi-permeable membranes can be classified by their hydraulic permeability into low flux membranes, medium flux membranes and high flux membranes.
Hydraulic permeability describes the quantity of water that can be ultrafiltered through a semi-permeable membrane with a given active surface area, at a given transmembrane pressure over a given time period. Simultaneously with the water ultrafiltration, salts and toxins traverse the semi-permeable membrane.
Eliminating the 2 0 different solutes depends on a property of the membrane known as the rejection rate or transmittance (transmittance = 1 or rejection rate = 0 for solutes traversing the membrane with no change in concentration, rejection rate = 100% and transmittance = 0 for completely cleared solutes). The transmittance of a particular molecule is defined as the ratio of the concentration of the molecule in ultrafiltered water (ultrafiltrate) to its mean concentration in the unfiltered fraction of the blood.
With high flux semi-permeable membranes, i.e., with a hydraulic permeability of at least 31 x 10-12 m3/s.Pa.m2 (15 mllh.mmHg.m2), the quantity of water extracted from the blood must be regulated using a water extraction controller. Devices provided with a high 3 0 flux membrane run the risk of reverse filtration or back filtration, which consists of migration of a portion of the dialysis solution into the blood.
la The dialysis solution, which has an electrolytic composition that is close to that of a normal extracellular liquid, is usually a non-sterile aqueous solution.
Before use, the dialysis solution is normally free of solutes to be eliminated from the blood, but can contain foreign substances or pyrogenic substances, for example as a result of microbial contamination. Dialysis solution is not intended for injection into the blood and thus does not have the quality of an injectable liquid. With back filtration, then, there is then a risk of causing foreign or pyrogenic substances to enter the blood with the dialysis solution.
As is known, back filtration can be minimised by using semi-permeable low flux membranes with a hydraulic permeability of less than 12.5 x 10-12 m3/s.Pa.m2 (6 s ml/h.mmHg.m2), or medium flux semi-permeable membranes with a permeability of between about 12.5 and about 31 x 10-~Z m3/s.Pa.m2 (between about 6 and about ml/h.mmHg.m2). However, the reduction in hydraulic permeability is generally accompanied by a reduction in transmittance, i.e., a reduction in the fraction of certain molecules that pass by convection through the pores of the membrane and which are t o intended to be eliminated from the blood.
Thus, one aim of the invention is to provide a device for treating blood or plasma by extracorporeal circulation, comprising a semi-permeable membrane with a reduced overall hydraulic permeability to limit the risks of reverse filtration, while retaining satisfactory transmittances, in particular those for toxins and proteins.
15 A further aim of the invention is to provide a device for treating blood or plasma by extracorporeal circulation comprising a semi-permeable membrane, the characteristics (hydraulic permeability, transmittances) of which can be adjusted independently of each other to a certain extent such that the hydraulic permeability of the membrane is low flux, medium flux or high flux, while the transmittances, in particular as regards toxins and 2o proteins, are maintained at satisfactory values.
In a first aspect of the invention, these aims are achieved by a bundle of hollow fibres intended to constitute the semi-permeable membrane of a device for treating blood or plasma by extracorporeal circulation, in which:
~ the distribution of the hollow fibres in the bundle is heterogeneous; and 25 ~ the internal diameter and wall thickness of the hollow fibres located in the zones most dense in hollow fibres are respectively greater than the internal diameter and wall thickness of the hollow fibres located in the least dense zones.
Preferably, the internal diameter and wall thickness of the hollow fibres located in the zones least dense in hollow fibres are respectively a minimum of 180 microns and 40 30 microns.
J
In a variation of the invention:
~ the heterogeneity of the distribution of the hollow fibres in the bundle corresponds to a higher density of hollow fibres around at least a portion of the periphery of the bundle compared with a density of hollow fibres at the centre of the bundle; and ~ the internal diameter and wall thickness of the hollow fibres located at the periphery of the bundle are respectively greater than the internal diameter and wall thickness of the hollow fibres located at the centre of the bundle.
In a second aspect of the present invention, the above aims are achieved by a bundle of hollow fibres intended to constitute the semi-permeable membrane of a device for treating blood or plasma by extracorporeal circulation, in which:
~ the hydraulic permeability of the hollow fibres in the bundle is heterogeneous; and ~ the ratio of the highest hydraulic permeability measured on some hollow fibres of the bundle to the lowest hydraulic permeability measured on other hollow fibres of the t 5 same bundle is at least about 5.
In a variation of the invention, the heterogeneity of the hydraulic permeability in the bundle corresponds to a higher hydraulic permeability around at least a portion of the periphery of the bundle compared with a hydraulic permeability of the bundle fibres, such that the ratio of the highest hydraulic permeability measured at the periphery of the bundle 2o to the lowest hydraulic permeability measured at the centre of the bundle is at least about In a further variation of the invention, the heterogeneity of the hydraulic permeability is associated with a heterogeneity of the distribution of the hollow fibres in the bundle, the hydraulic permeability being higher in the zones most dense in hollow fibres 25 and lower in the zones least dense in hollow fibres.
Advantageously, the internal diameter and wall thickness of the hollow fibres located in the zones most dense in hollow fibres are respectively greater than the internal diameter and wall thickness of the hollow fibres located in the zones least dense in hollow fibres. Advantageously again, the internal diameter and wall thickness of the hollow fibres located in the zones least dense in hollow fibres are respectively a minimum of 180 microns and 40 microns.
In one embodiment of the invention, the overall hydraulic permeability of the bundle of hollow fibres is in the range 10 x 10-2 to 312 x 10-2 m3/s.Pa.m2 (5 to 150 m1/h.mmHg.m2), the lowest hydraulic permeability measured at the centre of the bundle is less than 17 x 10-2 m3/s.Pa.m~ (8 ml/h.mmHg.m2) and the highest hydraulic permeability measured at the periphery of the bundle is more than 42 x 10-~2 m3/s.Pa.m2 (20 ml/h.mmHg.m2).
In a further embodiment, the overall hydraulic permeability of the bundle of hollow ~o fibres is in the range 42 x 10-2 to 146 x 10-2 m3/s.Pa.m2 (20 to 70 ml/h.mmHg.mZ), the lowest hydraulic permeability measured at the centre of the bundle is less than 17 x 10-2 m3/s.Pa.m2 (8 ml/h.mmHg.mz), the highest hydraulic permeability measured at the periphery of the bundle is more than 83 x 10-2 m3/s.Pa.m2 (40 ml/h.mmHg.m2) and the ratio of the highest hydraulic permeability measured at the periphery of the bundle to the lowest hydraulic permeability measured at the centre of the bundle is at least 10.
Within the context of the present invention, the overall hydraulic permeability Lp of the bundle is conventionally obtained by measuring the filtration time t of a volume V of water at a mean transmembrane pressure P of the order of 50 to 500 mmHg tluough a surface area S of membrane at a given temperature (see European standard EN
12.83). The 2o hydraulic permeability Lp is expressed in m3/s.Pa.mZ or ml/h.mmHg.m2 and corresponds to formula (I):
Lp = V/(tPS) (I) , To evaluate the heterogeneity of the hydraulic permeability of hollow fibres inside a bundle, within the context of the present invention a method has been developed for measuring the hydraulic permeability of a sub-group of hollow fibres of the bundle, the number of hollow fibres in the evaluated sub-group being substantially the same for each measurement. The hydraulic permeability of a sub-group of hollow fibres will be termed the ''local hydraulic permeability Lpi" in the description. In general, the method for measuring the local hydraulic permeability Lpi of a sub-group of hollow fibres of a bundle of hollow fibres mounted in a tubular casing comprising a lateral opening at one of its ends, the bundle of hollow fibres being fixed in the casing by an adhesive seal at each of its ends, and the adhesive seals having been cut perpendicular to a longitudinal axis of the bundle to open the fibres, comprises the principal steps defined in Claiin 26 below. The conditions for this measurement are diagrammatically shown in the accompanying Figure 1 and are 5 described in detail below. The local hydraulic permeability Lpi measurements are preferably carned out on a ready-to-use hollow fibre device for the treatment of blood or plasma by extracorporeal circulation, i.e. after assembling the various components of the hollow fibre device, in particular by mounting bundle 1 of hollow fibres in a tubular casing 2 comprising, at each of its ends, a lateral opening 5 and 6 (inlet/outlet channel) and by setting ~ 0 seals 3 and 4, after having separated the hollow fibres from each other at their ends, for example by riffling or brushing their ends, manually or with a stream of air.
This allows the ends of hollow fibres that have stuck together to be separated and eliminates the risk of leakage into the seal. As is well known, the sealing operation consists of securing the two ends of the bundle of hollow fibres by adhesive bonding using a seal in which a portion of I S the length of the fibres is embedded, the ends of the fibres being left open. Then the adhesive seals, in which the open ends of the hollow fibres are secured by adhesive and substantially uniformly distributed, are cut. To measure the local hydraulic permeability, casing 2 containing the bundle of hollow fibres is placed in a vertical position, and a seal is produced at the lower end of the casing (and as a result the lower cut surface of the bundle) 2o by pressing it on a plate 11 to ensure a seal, for example a plate of a flexible plastics material such as a silicone. A liquid, for example water or a dialysis liquid, is then passed at a flow rate of 80 ml/min, for example, through the lower lateral opening 6 while the upper lateral opening 5 is closed. A calibrated tube 12, in the vertical position, is applied to a portion of the upper cut surface of the bundle to measure the local flow rate at the upper 25 end of the casing. To carry out the measurement, calibrated tube 12 is firmly applied against the portion of the upper cut surface to be evaluated (in the figure, against the centre of the bundle of hollow fibres), to form an intimate connection between the upper cut surface and the calibrated tube 12. A flow of liquid is applied via lower lateral opening 6 of casing 2 and the time t that the liquid takes to pass from a given first graduation 13 to a 3o second given graduation 14 provided on calibrated tube 12 is measured. From the local measured flow rate (corresponding to the defined volume V of tube 12 between the two graduations 13, 14 related to the time t for the liquid to pass from graduation 13 to graduation 14) and the known values of the transmembrane pressure P and the surface area Si of the hollow fibres in the sub-group on which the local flow rate is being measured, the local hydraulic permeability Lpi is measured using the following formula (II):
Lpi = V/(tPSi) (II).
The dimensions of the calibrated tube 12 are not critical. They are suitable to allow local measurement of the flow rate. Thus the diameter of calibrated tube 12 can be 3.2 cm and its height can be of the order of 50 cm.
It should be noted that the local hydraulic permeability measured with the above method corresponds in fact to back filtration (passage of liquid from the dialysate compartment to the blood compartment, as conventionally defined, in particular via the insides of the hollow fibres), but other tests carried out by the Applicant have shown that the value of the hydraulic permeability of the hollow fibres does not depend on the i 5 direction of passage of the liquid.
By carrying out local hydraulic permeability measurements over the whole of the upper cut surface of the bundle of hollow fibres, the local hydraulic permeability can be mapped to show the variation with measurement zone. In this respect, it should be noted that the number of hollow fibres evaluated during each local hydraulic permeability 2o measurement is substantially constant. The operation of separating the hollow fibres from each other at their ends prior to sealing homogenises the hollow fibre density at the ends of the bundle.
In accordance with the present invention, the devices for treating blood or plasma by extracorporeal circulation contain a bundle composed of an assembly of hollow fibres 25 that differ from each other by their hydraulic permeability, certain hollow fibres being low flux while other hollow fibres are high flux. Overall, devices according to the present invention have the advantage of being capable of being high flux, medium flux or low flux depending on the local hydraulic penneabilities of the hollow fibres in the bundle.
TREATMENT OF BLOOD AND PLASMA, AND PROCESS FOR ITS
PRODUCTION
The present invention relates to a bundle of hollow fibres for a device for treating blood or plasma by extracorporeal circulation, and to a process for producing a bundle of hollow fibres constituting the semi-permeable membrane of the device.
Membrane devices for treating blood or plasma by extracorporeal circulation are 1 o used in many different medical or paramedical applications, such as treating renal insufficiency by dialysis or haemofiltration, plasmapheresis and apheresis for therapeutic and non-therapeutic purposes, oxygenating blood, immunopurification, etc.
In general, semi-permeable membranes can be classified by their hydraulic permeability into low flux membranes, medium flux membranes and high flux membranes.
Hydraulic permeability describes the quantity of water that can be ultrafiltered through a semi-permeable membrane with a given active surface area, at a given transmembrane pressure over a given time period. Simultaneously with the water ultrafiltration, salts and toxins traverse the semi-permeable membrane.
Eliminating the 2 0 different solutes depends on a property of the membrane known as the rejection rate or transmittance (transmittance = 1 or rejection rate = 0 for solutes traversing the membrane with no change in concentration, rejection rate = 100% and transmittance = 0 for completely cleared solutes). The transmittance of a particular molecule is defined as the ratio of the concentration of the molecule in ultrafiltered water (ultrafiltrate) to its mean concentration in the unfiltered fraction of the blood.
With high flux semi-permeable membranes, i.e., with a hydraulic permeability of at least 31 x 10-12 m3/s.Pa.m2 (15 mllh.mmHg.m2), the quantity of water extracted from the blood must be regulated using a water extraction controller. Devices provided with a high 3 0 flux membrane run the risk of reverse filtration or back filtration, which consists of migration of a portion of the dialysis solution into the blood.
la The dialysis solution, which has an electrolytic composition that is close to that of a normal extracellular liquid, is usually a non-sterile aqueous solution.
Before use, the dialysis solution is normally free of solutes to be eliminated from the blood, but can contain foreign substances or pyrogenic substances, for example as a result of microbial contamination. Dialysis solution is not intended for injection into the blood and thus does not have the quality of an injectable liquid. With back filtration, then, there is then a risk of causing foreign or pyrogenic substances to enter the blood with the dialysis solution.
As is known, back filtration can be minimised by using semi-permeable low flux membranes with a hydraulic permeability of less than 12.5 x 10-12 m3/s.Pa.m2 (6 s ml/h.mmHg.m2), or medium flux semi-permeable membranes with a permeability of between about 12.5 and about 31 x 10-~Z m3/s.Pa.m2 (between about 6 and about ml/h.mmHg.m2). However, the reduction in hydraulic permeability is generally accompanied by a reduction in transmittance, i.e., a reduction in the fraction of certain molecules that pass by convection through the pores of the membrane and which are t o intended to be eliminated from the blood.
Thus, one aim of the invention is to provide a device for treating blood or plasma by extracorporeal circulation, comprising a semi-permeable membrane with a reduced overall hydraulic permeability to limit the risks of reverse filtration, while retaining satisfactory transmittances, in particular those for toxins and proteins.
15 A further aim of the invention is to provide a device for treating blood or plasma by extracorporeal circulation comprising a semi-permeable membrane, the characteristics (hydraulic permeability, transmittances) of which can be adjusted independently of each other to a certain extent such that the hydraulic permeability of the membrane is low flux, medium flux or high flux, while the transmittances, in particular as regards toxins and 2o proteins, are maintained at satisfactory values.
In a first aspect of the invention, these aims are achieved by a bundle of hollow fibres intended to constitute the semi-permeable membrane of a device for treating blood or plasma by extracorporeal circulation, in which:
~ the distribution of the hollow fibres in the bundle is heterogeneous; and 25 ~ the internal diameter and wall thickness of the hollow fibres located in the zones most dense in hollow fibres are respectively greater than the internal diameter and wall thickness of the hollow fibres located in the least dense zones.
Preferably, the internal diameter and wall thickness of the hollow fibres located in the zones least dense in hollow fibres are respectively a minimum of 180 microns and 40 30 microns.
J
In a variation of the invention:
~ the heterogeneity of the distribution of the hollow fibres in the bundle corresponds to a higher density of hollow fibres around at least a portion of the periphery of the bundle compared with a density of hollow fibres at the centre of the bundle; and ~ the internal diameter and wall thickness of the hollow fibres located at the periphery of the bundle are respectively greater than the internal diameter and wall thickness of the hollow fibres located at the centre of the bundle.
In a second aspect of the present invention, the above aims are achieved by a bundle of hollow fibres intended to constitute the semi-permeable membrane of a device for treating blood or plasma by extracorporeal circulation, in which:
~ the hydraulic permeability of the hollow fibres in the bundle is heterogeneous; and ~ the ratio of the highest hydraulic permeability measured on some hollow fibres of the bundle to the lowest hydraulic permeability measured on other hollow fibres of the t 5 same bundle is at least about 5.
In a variation of the invention, the heterogeneity of the hydraulic permeability in the bundle corresponds to a higher hydraulic permeability around at least a portion of the periphery of the bundle compared with a hydraulic permeability of the bundle fibres, such that the ratio of the highest hydraulic permeability measured at the periphery of the bundle 2o to the lowest hydraulic permeability measured at the centre of the bundle is at least about In a further variation of the invention, the heterogeneity of the hydraulic permeability is associated with a heterogeneity of the distribution of the hollow fibres in the bundle, the hydraulic permeability being higher in the zones most dense in hollow fibres 25 and lower in the zones least dense in hollow fibres.
Advantageously, the internal diameter and wall thickness of the hollow fibres located in the zones most dense in hollow fibres are respectively greater than the internal diameter and wall thickness of the hollow fibres located in the zones least dense in hollow fibres. Advantageously again, the internal diameter and wall thickness of the hollow fibres located in the zones least dense in hollow fibres are respectively a minimum of 180 microns and 40 microns.
In one embodiment of the invention, the overall hydraulic permeability of the bundle of hollow fibres is in the range 10 x 10-2 to 312 x 10-2 m3/s.Pa.m2 (5 to 150 m1/h.mmHg.m2), the lowest hydraulic permeability measured at the centre of the bundle is less than 17 x 10-2 m3/s.Pa.m~ (8 ml/h.mmHg.m2) and the highest hydraulic permeability measured at the periphery of the bundle is more than 42 x 10-~2 m3/s.Pa.m2 (20 ml/h.mmHg.m2).
In a further embodiment, the overall hydraulic permeability of the bundle of hollow ~o fibres is in the range 42 x 10-2 to 146 x 10-2 m3/s.Pa.m2 (20 to 70 ml/h.mmHg.mZ), the lowest hydraulic permeability measured at the centre of the bundle is less than 17 x 10-2 m3/s.Pa.m2 (8 ml/h.mmHg.mz), the highest hydraulic permeability measured at the periphery of the bundle is more than 83 x 10-2 m3/s.Pa.m2 (40 ml/h.mmHg.m2) and the ratio of the highest hydraulic permeability measured at the periphery of the bundle to the lowest hydraulic permeability measured at the centre of the bundle is at least 10.
Within the context of the present invention, the overall hydraulic permeability Lp of the bundle is conventionally obtained by measuring the filtration time t of a volume V of water at a mean transmembrane pressure P of the order of 50 to 500 mmHg tluough a surface area S of membrane at a given temperature (see European standard EN
12.83). The 2o hydraulic permeability Lp is expressed in m3/s.Pa.mZ or ml/h.mmHg.m2 and corresponds to formula (I):
Lp = V/(tPS) (I) , To evaluate the heterogeneity of the hydraulic permeability of hollow fibres inside a bundle, within the context of the present invention a method has been developed for measuring the hydraulic permeability of a sub-group of hollow fibres of the bundle, the number of hollow fibres in the evaluated sub-group being substantially the same for each measurement. The hydraulic permeability of a sub-group of hollow fibres will be termed the ''local hydraulic permeability Lpi" in the description. In general, the method for measuring the local hydraulic permeability Lpi of a sub-group of hollow fibres of a bundle of hollow fibres mounted in a tubular casing comprising a lateral opening at one of its ends, the bundle of hollow fibres being fixed in the casing by an adhesive seal at each of its ends, and the adhesive seals having been cut perpendicular to a longitudinal axis of the bundle to open the fibres, comprises the principal steps defined in Claiin 26 below. The conditions for this measurement are diagrammatically shown in the accompanying Figure 1 and are 5 described in detail below. The local hydraulic permeability Lpi measurements are preferably carned out on a ready-to-use hollow fibre device for the treatment of blood or plasma by extracorporeal circulation, i.e. after assembling the various components of the hollow fibre device, in particular by mounting bundle 1 of hollow fibres in a tubular casing 2 comprising, at each of its ends, a lateral opening 5 and 6 (inlet/outlet channel) and by setting ~ 0 seals 3 and 4, after having separated the hollow fibres from each other at their ends, for example by riffling or brushing their ends, manually or with a stream of air.
This allows the ends of hollow fibres that have stuck together to be separated and eliminates the risk of leakage into the seal. As is well known, the sealing operation consists of securing the two ends of the bundle of hollow fibres by adhesive bonding using a seal in which a portion of I S the length of the fibres is embedded, the ends of the fibres being left open. Then the adhesive seals, in which the open ends of the hollow fibres are secured by adhesive and substantially uniformly distributed, are cut. To measure the local hydraulic permeability, casing 2 containing the bundle of hollow fibres is placed in a vertical position, and a seal is produced at the lower end of the casing (and as a result the lower cut surface of the bundle) 2o by pressing it on a plate 11 to ensure a seal, for example a plate of a flexible plastics material such as a silicone. A liquid, for example water or a dialysis liquid, is then passed at a flow rate of 80 ml/min, for example, through the lower lateral opening 6 while the upper lateral opening 5 is closed. A calibrated tube 12, in the vertical position, is applied to a portion of the upper cut surface of the bundle to measure the local flow rate at the upper 25 end of the casing. To carry out the measurement, calibrated tube 12 is firmly applied against the portion of the upper cut surface to be evaluated (in the figure, against the centre of the bundle of hollow fibres), to form an intimate connection between the upper cut surface and the calibrated tube 12. A flow of liquid is applied via lower lateral opening 6 of casing 2 and the time t that the liquid takes to pass from a given first graduation 13 to a 3o second given graduation 14 provided on calibrated tube 12 is measured. From the local measured flow rate (corresponding to the defined volume V of tube 12 between the two graduations 13, 14 related to the time t for the liquid to pass from graduation 13 to graduation 14) and the known values of the transmembrane pressure P and the surface area Si of the hollow fibres in the sub-group on which the local flow rate is being measured, the local hydraulic permeability Lpi is measured using the following formula (II):
Lpi = V/(tPSi) (II).
The dimensions of the calibrated tube 12 are not critical. They are suitable to allow local measurement of the flow rate. Thus the diameter of calibrated tube 12 can be 3.2 cm and its height can be of the order of 50 cm.
It should be noted that the local hydraulic permeability measured with the above method corresponds in fact to back filtration (passage of liquid from the dialysate compartment to the blood compartment, as conventionally defined, in particular via the insides of the hollow fibres), but other tests carried out by the Applicant have shown that the value of the hydraulic permeability of the hollow fibres does not depend on the i 5 direction of passage of the liquid.
By carrying out local hydraulic permeability measurements over the whole of the upper cut surface of the bundle of hollow fibres, the local hydraulic permeability can be mapped to show the variation with measurement zone. In this respect, it should be noted that the number of hollow fibres evaluated during each local hydraulic permeability 2o measurement is substantially constant. The operation of separating the hollow fibres from each other at their ends prior to sealing homogenises the hollow fibre density at the ends of the bundle.
In accordance with the present invention, the devices for treating blood or plasma by extracorporeal circulation contain a bundle composed of an assembly of hollow fibres 25 that differ from each other by their hydraulic permeability, certain hollow fibres being low flux while other hollow fibres are high flux. Overall, devices according to the present invention have the advantage of being capable of being high flux, medium flux or low flux depending on the local hydraulic penneabilities of the hollow fibres in the bundle.
The devices of the invention have the further advantage of having higher transmittance values than those obtained with conventional devices with an equivalent hydraulic permeability.
Thus, in the present invention, the devices can have a transmittance for cytochrome C of about 0.1 to about 0.6 (measured under the conditions specified in standard EN 12.83) with overall hydraulic permeability values of 20 x 10-~Z to 312 x 10-2 m3/s.Pa.m2 (10 to 150 ml/h.mmHg.mZ) In a variation of the invention, to produce the hollow fibre devices of the invention, hollow fibres consisting mainly of polyaiylsulphone are selected. Preferably, they contain 1 o repeating units with formula (I) or (II) below:
C p- O S02- ~ (~) o-~ O ~ n I
CHs O -~ 502 -n The polyarylsulphone with formula (I), the chain of which contains alkyl radicals, l5 in particular methyl radicals, is termed a polysulphone. The polyaiylsulphone with formula (II), which simply contains aryl radicals connected together by an ether or a sulphone group, is termed polyethersulphone.
The invention also pertains to a process for producing a bundle of hollow fibres consisting mainly of polarylsulphone, useful as a semi-permeable membrane in a device for 2o treating blood or plasma by extracorporeal circulation, the process comprising the following steps:
(a) preparing a bundle of hollow fibres with a heterogeneous distribution of fibres within the bundle insofar as the density of the hollow fibres .is higher in certain zones of the bundle than in other zones;
g (b) mounting the bundle of hollow fibres in a tubular casing comprising two axial openings;
(c) causing a hot, dry gas that is chemically inert towards the hollow fibres, preferably hot, dry air, to circulate through the bundle of hollow fibres, not held at its ends, at a temperature and flow rate that are suitable to cause geometrical heterogeneity of the hollow fibres in the bundle as regards the internal diameter and wall thickness of the hollow fibres;
(d) stopping the hot, dry gas from circulating when the geometrical heterogeneity of the hollow fibres has been obtained.
Adjusting the operating conditions of steps a) and c) affects the characteristics of devices for extracorporeal treatment of blood, in particular the hydraulic permeabilities.
The term "hot, dry gas" as used in the context of the present invention means a hot gas with a relative humidity that does not exceed 10% at the temperature at which the gas is used. Preferably, the temperature of the hot, dry gas at the inlet to the bundle of hollow fibres is 75°C to 130°C, more preferably 90°C to 120°C.
Preferably, the flow rate of the hot, dry gas at the inlet to the bundle of hollow fibres is 2 to 5 m3 per hour.
Preferably, the duration of step (c), consisting of circulating a hot, dry gas tluough the bundle of hollow fibres, is of the order of 1 to 4 hours.
2o Preferably, circulation of the hot, dry gas is stopped when the temperature of the gas at the outlet from the tubular casing is substantially equal to the temperature of the gas at the inlet to the tubular casing.
The invention also concerns a bundle of hollow fibres resulting from carrying out the production process described above.
Further characteristics and advantages of the invention will become apparent from the detailed description below, concerning variations and embodiments of the present invention.
Reference should also be made to the accompanying drawings, in which:
~ Figure 1 shows a diagrammatic view in longitudinal section of the device for ;o measuring local hydraulic permeability in accordance with the invention;
~ Figure 2 shows a partial diagrammatic perspective view of a fibre guiding device;
~ Figure 3 shows a perspective diagrammatic view of two carriages of the fibre guiding device that guide the hollow fibres into a semi-cylindrical trough;
~ Figure 4 shows an example of the variation with time of the amplitude of the reciprocating motion of the hollow-fibre guide carriages;
~ Figure 5 shows a diagrammatic view in transverse section of a bundle of hollow fibres after a fibre guiding step carried out in the manner described for Figure 4;
~ Figures 6a, 6b, 6c and 6d show the influence of the conditions of circulation of hot, dry air through the bundle of hollow fibres on the hydraulic permeability of i o the hollow fibres;
~ Figure 7 shows the correlation between the length of the hollow fibre after circulating hot, dry air and its hydraulic permeability.
To provide a detailed illustration of the invention, the production of a pauticular type of device for extracorporeal treatment of blood in accordance with the present invention will now be described.
1. Production of hollow fibre A polymer solution for extrusion is prepared that contains:
~ 14% by weight of polyarylsulphone, in particular a polyethersulphone (with a weight average molecular weight Mw of 70000 Daltons) miscible with N-2o methylpyrrolidone (NMP);
~ 5% by weight of a mixture of polyvinylpyrrolidone (PVP) of the K30 and K90 type, miscible with water and NMP;
~ 1% by weight of water;
~ 80% by weight of NMP.
Mixing is carned out at high temperature, of the order of 80-90°C, applying high shear forces. The solution is then cooled, preferably to 20°C.
To obtain a hollow fibre, the above polymer solution is extruded through a die comprising two concentric circular openings, an external annular opening to extrude the polymer solution and an internal central opening for passage of the hollow-fibre centring 3o and precipitating liquid. The external and internal diameters of the annular opening of the die are respectively 500 microns and 350 microns, and the diameter of the internal central opening is 170 microns.
The composition of the hollow-fibre centring and precipitating liquid in this example is a homogeneous mixture of 44% by weight of NMP, 55% by weight of water and 1 % by weight of PVP.
Under the conditions of this example, a hollow fibre is formed with an internal diameter of 215 ~.m and a wall thickness of 50 p.m.
The hollow fibre is then carefully washed with water that is free of pyrogenous elements by passing it through a plurality of baths without stretching it.
t o 2. Production of bundle of hollow fibres In accordance with the invention, when extrusion is complete, after precipitation and washing the hollow fibres, a bundle of hollow fibres is prepared that is substantially rectilinear with a heterogeneous distribution of fibres inside the bundle whereby the density of the hollow fibres is higher at the periphery of the bundle and lower at the centre of the bundle. The chemical nature of the hollow fibres in this example is identical throughout the bundle.
In this example, preparation of the fibre bundle comprises a fibre guiding step carried out using a fibre guiding device (shown diagrammatically in the accompanying Figures 2 and 3). Fibre guiding is an operation that consists of structuring the fibre bundle 2o and results in a criss-crossed arrangement of fibres. To this end, the fibre-guiding device comprises:
~ a drum 20 with a winding surface 21 with a regular polygonal cross section that can be rotated about its axis of symmetry 22, each side of the winding surface 21 of drum 20 being provided with a semi-cylindrical trough 23, the axes 24 of the semi-cylindrical troughs 23, which are aligned about the drum 20, being coplanar; and ~ at least one carriage 30 (in this case two carriages 30) carrying at least one set of guide rollers (not shown). located a certain distance from the drum 20, to guide and supply at least one hollow fibre 40 (or at least one strand of hollow fibres) 3o to the semi-cylindrical troughs 23, each carriage 30 being movable in a reciprocating motion perpendicular to the plane containing the axes 24 of troughs 23, with a variable amplitude not exceeding the diameter of the semi-cylindrical troughs.
The fibre guiding step consists of winding at least one hollow fibre 40 onto the s drum 20, which drum is rotated about its axis of symmetry 22, the hollow fibre being supplied and guided by the guide rollers on at least one carriage 30 to semi-cylindrical troughs 23 turning with the drum 20, to fill the troughs 23. In this example, the reciprocating motion of the two carnages 30 is in phase opposition and the reciprocating motion of each carriage 30 varies with time as shown in Figure 4 as the troughs 23 are filled, i o leading to the formation of bundles of hollow fibres:
( 1 ) initially, to fill the bottom of the semi-cylindrical troughs 23, the reciprocating motion amplitude is small;
(2) then the reciprocating motion amplitude varies regularly, increasing to reach a plateau corresponding to a value less than the diameter of the 15 semi-cylindrical troughs 23;
(3) then the reciprocating motion amplitude is kept constant for a certain period; and (4) finally, the reciprocating motion amplitude varies regularly, reducing to a very small value.
20 Further, during steps (1) to (4) above, the speed of rotation of drum 20 is substantially constant and the speed of displacement of each carnage 30 is substantially constant.
Preferably, the fibres are arranged into a bundle immediately after their production.
Between the extrusion device and the fibre-guiding device, they are kept under tension 25 without stretching them. They are wound onto drum 20 at a constant circumferential speed (circumferential speed of drum 20 in rotation about its axis of symmetry 22) in the range 20 to 80 metres/minute. As indicated above, semi-cylindrical troughs 23 corresponding to the number of bundles to be manufactured are fixed to the winding surface 21 of drum 20. In this example, the diameter of the troughs 23 is slightly larger than the diameter of the 3o bundles of hollow fibres before they are subjected to a circulation of hot, dry air, while the length of the troughs is slightly less than that of the bundles of hollow fibres. In this example, the trough diameter is 45 mm with a length of 280 mm. Twelve semi-cylindrical troughs 23 are mounted on the drum 20.
In this example, the hollow fibres leaving the extrusion step are distributed into two groups of fibres using fixed separating rollers (not shown), each group of fibres beiizg separately guided by a set of integral movable rollers carried by each of the respective carriages 30. The two groups of hollow fibres finally meet on the troughs 23 whereupon they are wound around the drum 20. As indicated above, the two carriages 30 are displaced in a reciprocating motion in phase opposition, with a variable amplitude, in this case from 0 to to 40 mm. Advantageously, each carriage 30 carries out an odd, non-integer number of movements in one direction per turn of the drum 20 that varies from 3 to 15, preferably 7.1 movements in one direction.
The displacement of the two carriages 30 that guide the fibres 40 towards the troughs 23 with a constant circumferential speed and a variable amplitude influences the structure of the bundle of hollow fibres. The density of the fibres disposed in the trough is inversely proportional to the amplitude of the displacement of the carriages 30: the smaller the displacement amplitude, the higher the density of the fibres placed in the troughs 23.
The fibre-guiding step contributes towards heterogeneous distribution of the hollow fibres with a higher fibre density in certain parts of the bundle. In this case, the bundles of hollow 2o fibres, after they have satisfied the conditions regarding the time variation of the amplitude of the reciprocating motion of the guide carriages 30 indicated in Figure 4, have a higher density at the periphery compared with the density at the centre (see Figure 5). Further, each bundle. comprises two longitudinal peripheral and opposed zones where the densities in hollow fibres are at their highest: these two zones correspond to the start and finish of filling of the troughs 23.
Clearly, the reciprocating motion amplitude of carriages 30 can be varied with time in a different way, and a different distribution of hollow fibres from that described above thus be produced, the zones most dense in hollow fibres then not necessarily being at the periphery of the bundle.
When the predefined number of hollow fibres per trough 23 has been reached, drum 20 is stopped from rotating, troughs 23 are closed with a semi-cylindrical cover (not shown) and the fibres between each trough 23 are cut.
In this example, each bundle of hollow fibres is then transferred into a tubular casing comprising two axial openings and two lateral openings.
After equalising the length of the hollow fibres for each bundle, the operations required to dry the bundles of fibres are carried out. If necessary, firstly, the liquid present in the hollow fibres is eliminated, preferably by centrifuging.
Then, in accordance with the invention, hot, dry air is passed through the bundles of ~ o hollow fibres that are not held at their ends, the hot, dry air entering via one axial opening iil the casing and leaving via the other axial opening in the casing, the two lateral openings in the casing being closed.
The hot, dry air is circulated under the temperature, flow rate and duration conditions described above, to cause a geometrical heterogeneity of the hollow fibres in the t 5 bundle (i.e., differences in the internal diameter and wall thickness of the fibres) and a heterogeneity in the density of the hollow fibres in the bundle.
Advantageously, the hot, dry air is injected via one of the axial openings of the casing with the speed of the circulation front homogeneous over the whole of this opening, under turbulent flux.
20 The hot, dry air introduced into the casing encounters the zones most dense in hollow fibres (at the periphery of the bundle) and preferentially passes along the less dense zones (in particular at the centre of the bundle). Further, circulating hot air in the casuig tends to displace and constrain the hollow fibres towards the periphery of the bundle, against the walls of the casing. This drying step, therefore, also contributes to 25 heterogeneity in the distribution of the hollow fibres in the bundle.
Further, because of the preferential passage of the hot air along the central portion of the bundle, the fibres of the interior of the bundle shrink more (length, internal and external diameters and thickness) than those at the periphery of the bundle.
With such a bundle of hollow fibres, a device can be produced to treat blood or 3o plasma with reduced risks of reverse filtration, an overall hydraulic permeability that can be adjusted to requirements and with transmittances that are higher than those of a conventional device with a similar hydraulic permeability.
Further, with such a bundle, a device can be produced for treating blood or plasma with characteristics (hydraulic permeability, transmittances) that can be independently adjusted to a certain extent so that the hydraulic permeability of the membrane is low flux, medium flux or high flux, while the transmittances, in particular those for toxins and proteins, are maintained at values that are higher than those of a conventional device with a similar hydraulic permeability.
The last steps necessary for finishing the manufacture of a device for treating blood ~o or plasma by extracorporeal circulation in accordance with the invention after stopping the circulation of the hot, dry air as soon as the bundle of hollow fibres is sufficiently dry to allow it to be sealed, are conventional. The principal steps are:
~ homogenising the distribution of the fibres, limited to the ends of the bundle;
~ sealing, consisting of securing the two ends of the bundle of hollow fibres by adhesion using a seal in which a portion of the length of the fibres is embedded, the ends of the fibres being left open;
~ cutting the ends of the bundle;
~ closing the tubular casing at its two ends with caps;
~ sterilising the medical device.
2o EXAMPLES 1 TO 5 Dialysers comprising about 8000 hollow polyethersulphone fibres were produced and assembled as in the above detailed description.
Only the conditions for circulating the hot, dry air differed between the examples.
The table below summarises these conditions.
Example Air flow rate Temperature of hot, (m3/h) dry air at inlet into tubular casing, C
Comparative example 2 60 q 4 110 From the results for the measurements of local permeability Lpi, four maps were established by mathematical regression: see Figures 6a, 6b, 6c and 6d, which correspond to Examples 2, 3, 4 and 5, respectively. In Figures 6a, 6b, 6c and 6d:
5 ~ the axes of the abscissas and ordinates, graduated from -50 mm to +50 rnm, represent two directions that are perpendicular to each other, of one of the cut surfaces of the ends of the bundle of hollow fibres;
~ each curve, closed or otherwise, marked in dotted lines or as a solid line, represents points with the same local hydraulic permeability Lpi, expressed in 1 o ml/h.mmHg.m2;
the central curve, shown in dotted lines, represents points with a local hydraulic permeability Lpi of 0 ml/h.mmHg.m2;
~ the difference between two successive curves is 10 ml/h.mmHg.m2;
~ the key given with each figure notes successive values of the local hydraulic ~ 5 permeability Lpi at each curve starting from the central curve.
Figures 6a, 6b, 6c and 6d demonstrate that the local hydraulic permeabilities Lpi are higher at the periphery of the bundle than at the centre of the bundle.
The table below also shows the influence of the conditions for circulating hot, dry air on the overall and local hydraulic permeabilities, Lpi, measured before sterilisation.
Hydraulic permeability (mUh.mmHg.m2) Example n Overall Minimum at Maximum at Max/min bundle centrebundle peripheryratio 1 (comparative)200 200 200 1 2 30 1.5 80 53 3 25 0.9 63 70 4 23 4.1 98 24 S 18 1.5 46 30 The table below shows the dimensions of certain hollow fibres before and after circulating hot, dry air through the bundle of Example 2. The fibre dimensions were measured using an optical microscope and the results shown below in the table correspond to an average of measurements over 36 fibres.
Internal diameterExternal diameterWall thickness (Nnl) (l~nl) (I~m) Before circulating215 315 50 hot, dry air After circulating hot, dry air:
hollow fibres 213.7 313.6 49.9 at periphery of bundle hollow fibres 205.7 299.1 46.7 at centre of bundle Dialysers comprising about 8000 hollow polyethersulphone fibres were produced and assembled as in the above detailed description.
The conditions for producing the dialysers were substantially similar, with the exception of the conditions for circulating the hot, diy air, which differed from one example to another.
The table below shows the conditions and the results of measurements of the overall hydraulic permeability.
Example Hot air flow Temperature Overall hydraulic n rate of hot, permeability (m3/h) dry air at inlet(ml/h.mmHg.mz) (C) 6 ~ 2, then 1 85-90 37 7 ~ 4, then 2 85-90 51 8 ~ 4, then 2 75-80 54 9 ~ 2 90 33 ~ 1 90 29 Dialysers comprising about 8000 hollow polyethersulphone fibres were produced and assembled as described in the above detailed description.
1 o The conditions for producing the dialysers were substantially similar with the exception of the hot, dry air circulation conditions, which differed between examples.
The table below shows the conditions and the results of measurements of the overall hydraulic permeability Lp and cytochrome C transmittance (Tr), and measurements of the length (L) of the hollow fibres, maximum and minimum, after circulating hot, dry air.
~ 5 The transmittance measurement conditions were: a starting concentration of cytochrome C
of 0.05 g/1, a blood flow rate of about 400 ml/min and an ultrafiltration flow rate of about 80 ml/min. The maximum length, Lmax, and the minimum length, L min, corresponded to the length of the longest fibre and shortest fibre in the bundle respectively. The longest fibre was located at the periphery of the bundle, while the shortest was located at the centre of 2o the bundle.
Example Air TemperatureLp Tr for Lmax L min Difference no. flow of hot, (ml/h.mmcytochrome(mm) (mm) between rate dry Hg.mm2) C Lmax and (m3/h)air at Lmin inlet (nun) to tubular casing, C
11 4.5 102 46.9 n.m. 269.6 268.3 1.3 12 4.5 97.5 55.8 n.m. 270.4 269.4 1.0 13 4.0 97.5 48.7 n.m. 270.2 269.5 0.7 14 4.5 100 42.6 0.23 269.8 268.9 0.9 15 4.5 100 34.1 0.22 269.8 268.5 1.3 16 4.8 93 58.4 0.36 270.2 269.5 0.7 17 4.8 93 63.3 0.39 271.0 269.5 1.5 18 4.8 93 53.2 0.37 270.1 269.3 0.8 19 4.8 93 47.0 0.36 270.1 269.3 0.8 20 4.8 93 46.7 0.34 270.3 269.4 0.9 21 2 105 45.5 0.47 270.3 267.3 3.0 22 2 105 41.8 0.47 270.1 267.4 2.7 23 2 105 44.5 0.47 270.6 267.2 3.4 24 2 105 35.7 0.41 270.2 267.0 3.2 25 4 109 27.3 0.46 269.7 267.7 2.0 26 4 109 27.2 0.52 269.1 267.1 2.0 27 4 109 24.8 0.48 269.2 267.4 1.8 28 4 109 24.9 0.52 269.1 267.2 1.9 29 4.8 93 68.8 n.m. 269.9 269.3 0.6 n.m. means: not measured.
Figure 7 illustrates the relationship between the mean fibre length of the bundle after circulating hot, dry air (along the abscissa) and the overall hydraulic permeability, Lp, of the bundle (up the ordinate), established from Examples 11 to 29.
The mean fibre length corresponds to the mean of values Lmax and Lmin given above.
Figure 7 shows a correlation between this mean fibre length and the overall hydraulic permeability of the bundle.
Thus, in the present invention, the devices can have a transmittance for cytochrome C of about 0.1 to about 0.6 (measured under the conditions specified in standard EN 12.83) with overall hydraulic permeability values of 20 x 10-~Z to 312 x 10-2 m3/s.Pa.m2 (10 to 150 ml/h.mmHg.mZ) In a variation of the invention, to produce the hollow fibre devices of the invention, hollow fibres consisting mainly of polyaiylsulphone are selected. Preferably, they contain 1 o repeating units with formula (I) or (II) below:
C p- O S02- ~ (~) o-~ O ~ n I
CHs O -~ 502 -n The polyarylsulphone with formula (I), the chain of which contains alkyl radicals, l5 in particular methyl radicals, is termed a polysulphone. The polyaiylsulphone with formula (II), which simply contains aryl radicals connected together by an ether or a sulphone group, is termed polyethersulphone.
The invention also pertains to a process for producing a bundle of hollow fibres consisting mainly of polarylsulphone, useful as a semi-permeable membrane in a device for 2o treating blood or plasma by extracorporeal circulation, the process comprising the following steps:
(a) preparing a bundle of hollow fibres with a heterogeneous distribution of fibres within the bundle insofar as the density of the hollow fibres .is higher in certain zones of the bundle than in other zones;
g (b) mounting the bundle of hollow fibres in a tubular casing comprising two axial openings;
(c) causing a hot, dry gas that is chemically inert towards the hollow fibres, preferably hot, dry air, to circulate through the bundle of hollow fibres, not held at its ends, at a temperature and flow rate that are suitable to cause geometrical heterogeneity of the hollow fibres in the bundle as regards the internal diameter and wall thickness of the hollow fibres;
(d) stopping the hot, dry gas from circulating when the geometrical heterogeneity of the hollow fibres has been obtained.
Adjusting the operating conditions of steps a) and c) affects the characteristics of devices for extracorporeal treatment of blood, in particular the hydraulic permeabilities.
The term "hot, dry gas" as used in the context of the present invention means a hot gas with a relative humidity that does not exceed 10% at the temperature at which the gas is used. Preferably, the temperature of the hot, dry gas at the inlet to the bundle of hollow fibres is 75°C to 130°C, more preferably 90°C to 120°C.
Preferably, the flow rate of the hot, dry gas at the inlet to the bundle of hollow fibres is 2 to 5 m3 per hour.
Preferably, the duration of step (c), consisting of circulating a hot, dry gas tluough the bundle of hollow fibres, is of the order of 1 to 4 hours.
2o Preferably, circulation of the hot, dry gas is stopped when the temperature of the gas at the outlet from the tubular casing is substantially equal to the temperature of the gas at the inlet to the tubular casing.
The invention also concerns a bundle of hollow fibres resulting from carrying out the production process described above.
Further characteristics and advantages of the invention will become apparent from the detailed description below, concerning variations and embodiments of the present invention.
Reference should also be made to the accompanying drawings, in which:
~ Figure 1 shows a diagrammatic view in longitudinal section of the device for ;o measuring local hydraulic permeability in accordance with the invention;
~ Figure 2 shows a partial diagrammatic perspective view of a fibre guiding device;
~ Figure 3 shows a perspective diagrammatic view of two carriages of the fibre guiding device that guide the hollow fibres into a semi-cylindrical trough;
~ Figure 4 shows an example of the variation with time of the amplitude of the reciprocating motion of the hollow-fibre guide carriages;
~ Figure 5 shows a diagrammatic view in transverse section of a bundle of hollow fibres after a fibre guiding step carried out in the manner described for Figure 4;
~ Figures 6a, 6b, 6c and 6d show the influence of the conditions of circulation of hot, dry air through the bundle of hollow fibres on the hydraulic permeability of i o the hollow fibres;
~ Figure 7 shows the correlation between the length of the hollow fibre after circulating hot, dry air and its hydraulic permeability.
To provide a detailed illustration of the invention, the production of a pauticular type of device for extracorporeal treatment of blood in accordance with the present invention will now be described.
1. Production of hollow fibre A polymer solution for extrusion is prepared that contains:
~ 14% by weight of polyarylsulphone, in particular a polyethersulphone (with a weight average molecular weight Mw of 70000 Daltons) miscible with N-2o methylpyrrolidone (NMP);
~ 5% by weight of a mixture of polyvinylpyrrolidone (PVP) of the K30 and K90 type, miscible with water and NMP;
~ 1% by weight of water;
~ 80% by weight of NMP.
Mixing is carned out at high temperature, of the order of 80-90°C, applying high shear forces. The solution is then cooled, preferably to 20°C.
To obtain a hollow fibre, the above polymer solution is extruded through a die comprising two concentric circular openings, an external annular opening to extrude the polymer solution and an internal central opening for passage of the hollow-fibre centring 3o and precipitating liquid. The external and internal diameters of the annular opening of the die are respectively 500 microns and 350 microns, and the diameter of the internal central opening is 170 microns.
The composition of the hollow-fibre centring and precipitating liquid in this example is a homogeneous mixture of 44% by weight of NMP, 55% by weight of water and 1 % by weight of PVP.
Under the conditions of this example, a hollow fibre is formed with an internal diameter of 215 ~.m and a wall thickness of 50 p.m.
The hollow fibre is then carefully washed with water that is free of pyrogenous elements by passing it through a plurality of baths without stretching it.
t o 2. Production of bundle of hollow fibres In accordance with the invention, when extrusion is complete, after precipitation and washing the hollow fibres, a bundle of hollow fibres is prepared that is substantially rectilinear with a heterogeneous distribution of fibres inside the bundle whereby the density of the hollow fibres is higher at the periphery of the bundle and lower at the centre of the bundle. The chemical nature of the hollow fibres in this example is identical throughout the bundle.
In this example, preparation of the fibre bundle comprises a fibre guiding step carried out using a fibre guiding device (shown diagrammatically in the accompanying Figures 2 and 3). Fibre guiding is an operation that consists of structuring the fibre bundle 2o and results in a criss-crossed arrangement of fibres. To this end, the fibre-guiding device comprises:
~ a drum 20 with a winding surface 21 with a regular polygonal cross section that can be rotated about its axis of symmetry 22, each side of the winding surface 21 of drum 20 being provided with a semi-cylindrical trough 23, the axes 24 of the semi-cylindrical troughs 23, which are aligned about the drum 20, being coplanar; and ~ at least one carriage 30 (in this case two carriages 30) carrying at least one set of guide rollers (not shown). located a certain distance from the drum 20, to guide and supply at least one hollow fibre 40 (or at least one strand of hollow fibres) 3o to the semi-cylindrical troughs 23, each carriage 30 being movable in a reciprocating motion perpendicular to the plane containing the axes 24 of troughs 23, with a variable amplitude not exceeding the diameter of the semi-cylindrical troughs.
The fibre guiding step consists of winding at least one hollow fibre 40 onto the s drum 20, which drum is rotated about its axis of symmetry 22, the hollow fibre being supplied and guided by the guide rollers on at least one carriage 30 to semi-cylindrical troughs 23 turning with the drum 20, to fill the troughs 23. In this example, the reciprocating motion of the two carnages 30 is in phase opposition and the reciprocating motion of each carriage 30 varies with time as shown in Figure 4 as the troughs 23 are filled, i o leading to the formation of bundles of hollow fibres:
( 1 ) initially, to fill the bottom of the semi-cylindrical troughs 23, the reciprocating motion amplitude is small;
(2) then the reciprocating motion amplitude varies regularly, increasing to reach a plateau corresponding to a value less than the diameter of the 15 semi-cylindrical troughs 23;
(3) then the reciprocating motion amplitude is kept constant for a certain period; and (4) finally, the reciprocating motion amplitude varies regularly, reducing to a very small value.
20 Further, during steps (1) to (4) above, the speed of rotation of drum 20 is substantially constant and the speed of displacement of each carnage 30 is substantially constant.
Preferably, the fibres are arranged into a bundle immediately after their production.
Between the extrusion device and the fibre-guiding device, they are kept under tension 25 without stretching them. They are wound onto drum 20 at a constant circumferential speed (circumferential speed of drum 20 in rotation about its axis of symmetry 22) in the range 20 to 80 metres/minute. As indicated above, semi-cylindrical troughs 23 corresponding to the number of bundles to be manufactured are fixed to the winding surface 21 of drum 20. In this example, the diameter of the troughs 23 is slightly larger than the diameter of the 3o bundles of hollow fibres before they are subjected to a circulation of hot, dry air, while the length of the troughs is slightly less than that of the bundles of hollow fibres. In this example, the trough diameter is 45 mm with a length of 280 mm. Twelve semi-cylindrical troughs 23 are mounted on the drum 20.
In this example, the hollow fibres leaving the extrusion step are distributed into two groups of fibres using fixed separating rollers (not shown), each group of fibres beiizg separately guided by a set of integral movable rollers carried by each of the respective carriages 30. The two groups of hollow fibres finally meet on the troughs 23 whereupon they are wound around the drum 20. As indicated above, the two carriages 30 are displaced in a reciprocating motion in phase opposition, with a variable amplitude, in this case from 0 to to 40 mm. Advantageously, each carriage 30 carries out an odd, non-integer number of movements in one direction per turn of the drum 20 that varies from 3 to 15, preferably 7.1 movements in one direction.
The displacement of the two carriages 30 that guide the fibres 40 towards the troughs 23 with a constant circumferential speed and a variable amplitude influences the structure of the bundle of hollow fibres. The density of the fibres disposed in the trough is inversely proportional to the amplitude of the displacement of the carriages 30: the smaller the displacement amplitude, the higher the density of the fibres placed in the troughs 23.
The fibre-guiding step contributes towards heterogeneous distribution of the hollow fibres with a higher fibre density in certain parts of the bundle. In this case, the bundles of hollow 2o fibres, after they have satisfied the conditions regarding the time variation of the amplitude of the reciprocating motion of the guide carriages 30 indicated in Figure 4, have a higher density at the periphery compared with the density at the centre (see Figure 5). Further, each bundle. comprises two longitudinal peripheral and opposed zones where the densities in hollow fibres are at their highest: these two zones correspond to the start and finish of filling of the troughs 23.
Clearly, the reciprocating motion amplitude of carriages 30 can be varied with time in a different way, and a different distribution of hollow fibres from that described above thus be produced, the zones most dense in hollow fibres then not necessarily being at the periphery of the bundle.
When the predefined number of hollow fibres per trough 23 has been reached, drum 20 is stopped from rotating, troughs 23 are closed with a semi-cylindrical cover (not shown) and the fibres between each trough 23 are cut.
In this example, each bundle of hollow fibres is then transferred into a tubular casing comprising two axial openings and two lateral openings.
After equalising the length of the hollow fibres for each bundle, the operations required to dry the bundles of fibres are carried out. If necessary, firstly, the liquid present in the hollow fibres is eliminated, preferably by centrifuging.
Then, in accordance with the invention, hot, dry air is passed through the bundles of ~ o hollow fibres that are not held at their ends, the hot, dry air entering via one axial opening iil the casing and leaving via the other axial opening in the casing, the two lateral openings in the casing being closed.
The hot, dry air is circulated under the temperature, flow rate and duration conditions described above, to cause a geometrical heterogeneity of the hollow fibres in the t 5 bundle (i.e., differences in the internal diameter and wall thickness of the fibres) and a heterogeneity in the density of the hollow fibres in the bundle.
Advantageously, the hot, dry air is injected via one of the axial openings of the casing with the speed of the circulation front homogeneous over the whole of this opening, under turbulent flux.
20 The hot, dry air introduced into the casing encounters the zones most dense in hollow fibres (at the periphery of the bundle) and preferentially passes along the less dense zones (in particular at the centre of the bundle). Further, circulating hot air in the casuig tends to displace and constrain the hollow fibres towards the periphery of the bundle, against the walls of the casing. This drying step, therefore, also contributes to 25 heterogeneity in the distribution of the hollow fibres in the bundle.
Further, because of the preferential passage of the hot air along the central portion of the bundle, the fibres of the interior of the bundle shrink more (length, internal and external diameters and thickness) than those at the periphery of the bundle.
With such a bundle of hollow fibres, a device can be produced to treat blood or 3o plasma with reduced risks of reverse filtration, an overall hydraulic permeability that can be adjusted to requirements and with transmittances that are higher than those of a conventional device with a similar hydraulic permeability.
Further, with such a bundle, a device can be produced for treating blood or plasma with characteristics (hydraulic permeability, transmittances) that can be independently adjusted to a certain extent so that the hydraulic permeability of the membrane is low flux, medium flux or high flux, while the transmittances, in particular those for toxins and proteins, are maintained at values that are higher than those of a conventional device with a similar hydraulic permeability.
The last steps necessary for finishing the manufacture of a device for treating blood ~o or plasma by extracorporeal circulation in accordance with the invention after stopping the circulation of the hot, dry air as soon as the bundle of hollow fibres is sufficiently dry to allow it to be sealed, are conventional. The principal steps are:
~ homogenising the distribution of the fibres, limited to the ends of the bundle;
~ sealing, consisting of securing the two ends of the bundle of hollow fibres by adhesion using a seal in which a portion of the length of the fibres is embedded, the ends of the fibres being left open;
~ cutting the ends of the bundle;
~ closing the tubular casing at its two ends with caps;
~ sterilising the medical device.
2o EXAMPLES 1 TO 5 Dialysers comprising about 8000 hollow polyethersulphone fibres were produced and assembled as in the above detailed description.
Only the conditions for circulating the hot, dry air differed between the examples.
The table below summarises these conditions.
Example Air flow rate Temperature of hot, (m3/h) dry air at inlet into tubular casing, C
Comparative example 2 60 q 4 110 From the results for the measurements of local permeability Lpi, four maps were established by mathematical regression: see Figures 6a, 6b, 6c and 6d, which correspond to Examples 2, 3, 4 and 5, respectively. In Figures 6a, 6b, 6c and 6d:
5 ~ the axes of the abscissas and ordinates, graduated from -50 mm to +50 rnm, represent two directions that are perpendicular to each other, of one of the cut surfaces of the ends of the bundle of hollow fibres;
~ each curve, closed or otherwise, marked in dotted lines or as a solid line, represents points with the same local hydraulic permeability Lpi, expressed in 1 o ml/h.mmHg.m2;
the central curve, shown in dotted lines, represents points with a local hydraulic permeability Lpi of 0 ml/h.mmHg.m2;
~ the difference between two successive curves is 10 ml/h.mmHg.m2;
~ the key given with each figure notes successive values of the local hydraulic ~ 5 permeability Lpi at each curve starting from the central curve.
Figures 6a, 6b, 6c and 6d demonstrate that the local hydraulic permeabilities Lpi are higher at the periphery of the bundle than at the centre of the bundle.
The table below also shows the influence of the conditions for circulating hot, dry air on the overall and local hydraulic permeabilities, Lpi, measured before sterilisation.
Hydraulic permeability (mUh.mmHg.m2) Example n Overall Minimum at Maximum at Max/min bundle centrebundle peripheryratio 1 (comparative)200 200 200 1 2 30 1.5 80 53 3 25 0.9 63 70 4 23 4.1 98 24 S 18 1.5 46 30 The table below shows the dimensions of certain hollow fibres before and after circulating hot, dry air through the bundle of Example 2. The fibre dimensions were measured using an optical microscope and the results shown below in the table correspond to an average of measurements over 36 fibres.
Internal diameterExternal diameterWall thickness (Nnl) (l~nl) (I~m) Before circulating215 315 50 hot, dry air After circulating hot, dry air:
hollow fibres 213.7 313.6 49.9 at periphery of bundle hollow fibres 205.7 299.1 46.7 at centre of bundle Dialysers comprising about 8000 hollow polyethersulphone fibres were produced and assembled as in the above detailed description.
The conditions for producing the dialysers were substantially similar, with the exception of the conditions for circulating the hot, diy air, which differed from one example to another.
The table below shows the conditions and the results of measurements of the overall hydraulic permeability.
Example Hot air flow Temperature Overall hydraulic n rate of hot, permeability (m3/h) dry air at inlet(ml/h.mmHg.mz) (C) 6 ~ 2, then 1 85-90 37 7 ~ 4, then 2 85-90 51 8 ~ 4, then 2 75-80 54 9 ~ 2 90 33 ~ 1 90 29 Dialysers comprising about 8000 hollow polyethersulphone fibres were produced and assembled as described in the above detailed description.
1 o The conditions for producing the dialysers were substantially similar with the exception of the hot, dry air circulation conditions, which differed between examples.
The table below shows the conditions and the results of measurements of the overall hydraulic permeability Lp and cytochrome C transmittance (Tr), and measurements of the length (L) of the hollow fibres, maximum and minimum, after circulating hot, dry air.
~ 5 The transmittance measurement conditions were: a starting concentration of cytochrome C
of 0.05 g/1, a blood flow rate of about 400 ml/min and an ultrafiltration flow rate of about 80 ml/min. The maximum length, Lmax, and the minimum length, L min, corresponded to the length of the longest fibre and shortest fibre in the bundle respectively. The longest fibre was located at the periphery of the bundle, while the shortest was located at the centre of 2o the bundle.
Example Air TemperatureLp Tr for Lmax L min Difference no. flow of hot, (ml/h.mmcytochrome(mm) (mm) between rate dry Hg.mm2) C Lmax and (m3/h)air at Lmin inlet (nun) to tubular casing, C
11 4.5 102 46.9 n.m. 269.6 268.3 1.3 12 4.5 97.5 55.8 n.m. 270.4 269.4 1.0 13 4.0 97.5 48.7 n.m. 270.2 269.5 0.7 14 4.5 100 42.6 0.23 269.8 268.9 0.9 15 4.5 100 34.1 0.22 269.8 268.5 1.3 16 4.8 93 58.4 0.36 270.2 269.5 0.7 17 4.8 93 63.3 0.39 271.0 269.5 1.5 18 4.8 93 53.2 0.37 270.1 269.3 0.8 19 4.8 93 47.0 0.36 270.1 269.3 0.8 20 4.8 93 46.7 0.34 270.3 269.4 0.9 21 2 105 45.5 0.47 270.3 267.3 3.0 22 2 105 41.8 0.47 270.1 267.4 2.7 23 2 105 44.5 0.47 270.6 267.2 3.4 24 2 105 35.7 0.41 270.2 267.0 3.2 25 4 109 27.3 0.46 269.7 267.7 2.0 26 4 109 27.2 0.52 269.1 267.1 2.0 27 4 109 24.8 0.48 269.2 267.4 1.8 28 4 109 24.9 0.52 269.1 267.2 1.9 29 4.8 93 68.8 n.m. 269.9 269.3 0.6 n.m. means: not measured.
Figure 7 illustrates the relationship between the mean fibre length of the bundle after circulating hot, dry air (along the abscissa) and the overall hydraulic permeability, Lp, of the bundle (up the ordinate), established from Examples 11 to 29.
The mean fibre length corresponds to the mean of values Lmax and Lmin given above.
Figure 7 shows a correlation between this mean fibre length and the overall hydraulic permeability of the bundle.
Claims (26)
1. Bundle of hollow fibres intended to constitute the semi-permeable membrane of a device for treating blood or plasma by extracorporeal circulation, in which:
.cndot. the distribution of the hollow fibres in the bundle is heterogeneous;
and .cndot. the internal diameter and wall thickness of the hollow fibres located in the zones most dense in hollow fibres are respectively greater than the internal diameter and wall thickness of the hollow fibres located in the zones least dense in hollow fibres.
.cndot. the distribution of the hollow fibres in the bundle is heterogeneous;
and .cndot. the internal diameter and wall thickness of the hollow fibres located in the zones most dense in hollow fibres are respectively greater than the internal diameter and wall thickness of the hollow fibres located in the zones least dense in hollow fibres.
2. Bundle of hollow fibres according to Claim 1, in which the internal diameter and wall thickness of the hollow fibres located in the zones least dense in hollow fibres are respectively a minimum of 180 microns and 40 microns.
3. Bundle of hollow fibres according to Claim 1 or Claim 2, in which:
.cndot. the heterogeneity of the distribution of the hollow fibres in the bundle corresponds to a higher density of hollow fibres around at least a portion of the periphery of the bundle compared with a density of hollow fibres at the centre of the bundle; and .cndot. the internal diameter and wall thickness of the hollow fibres located at the periphery of the bundle are respectively greater than the internal diameter and wall thickness of the hollow fibres located at the centre of the bundle.
.cndot. the heterogeneity of the distribution of the hollow fibres in the bundle corresponds to a higher density of hollow fibres around at least a portion of the periphery of the bundle compared with a density of hollow fibres at the centre of the bundle; and .cndot. the internal diameter and wall thickness of the hollow fibres located at the periphery of the bundle are respectively greater than the internal diameter and wall thickness of the hollow fibres located at the centre of the bundle.
4. Bundle of hollow fibres intended to constitute the membrane of a device for treating blood or plasma by extracorporeal circulation, in which:
.cndot. the hydraulic permeability of the hollow fibres in the bundle is heterogeneous; and .cndot. the ratio of the highest hydraulic permeability measured on some hollow fibres of the bundle to the lowest hydraulic permeability measured on other hollow fibres of the same bundle is at least about 5.
.cndot. the hydraulic permeability of the hollow fibres in the bundle is heterogeneous; and .cndot. the ratio of the highest hydraulic permeability measured on some hollow fibres of the bundle to the lowest hydraulic permeability measured on other hollow fibres of the same bundle is at least about 5.
5. Bundle of hollow fibres according to Claim 4, in which the heterogeneity of the hydraulic permeability of the hollow fibres in the bundle corresponds to a higher hydraulic permeability around at least a portion of the periphery of the bundle compared with a hydraulic permeability of the bundle fibres at the centre of the bundle, such that the ratio of the highest hydraulic permeability measured at the periphery of the bundle to the lowest hydraulic permeability measured at the centre of the bundle is at least 5.
6. Bundle of hollow fibres according to Claim 4, in which the heterogeneity of the hydraulic permeability is associated with a heterogeneity of the distribution of the hollow fibres in the bundle, the hydraulic permeability being higher in the zones most dense in hollow fibres and lower in the zones least dense in hollow fibres.
7. Bundle of hollow fibres according to Claim 6, in which the overall hydraulic permeability of the bundle of hollow fibres is in the range 10 x 10-12 to 312 x 10-12 m3/s.Pa.m2, the lowest hydraulic permeability measured at the centre of the bundle is less than 17 x 10-12 m3/s.Pa.m2 and the highest hydraulic permeability measured at the periphery of the bundle is more than 42 x 10-12 m3/s.Pa.m2.
8. Bundle of hollow fibres according to Claim 6, in which the overall hydraulic permeability of the bundle of hollow fibres is in the range 42 x 10-12 to 146 x 10-12 m3/s.Pa.m2, the lowest hydraulic permeability at the centre of the bundle is less than 17 X 10-12 m3/s.Pa.m2, the highest hydraulic permeability measured at the periphery of the bundle is more than 87 x 10-12 m3/s.Pa.m2 and the ratio of the highest hydraulic permeability measured at the periphery of the bundle to the lowest hydraulic permeability measured at the centre of the bundle is at least 10.
9. Bundle of hollow fibres according to Claim 6, in which the internal diameter and wall thickness of the hollow fibres located in the zones most dense in hollow fibres are respectively greater than the internal diameter and wall thickness of the hollow fibres located in the zones least dense in hollow fibres.
10. Bundle of hollow fibres according to Claim 9, in which the internal diameter and wall thickness of the hollow fibres located in the zones least dense in the hollow fibres are respectively a minimum of 180 microns and 40 microns.
11. Bundle of hollow fibres according to one of Claims 1 to 10, in which the transmittance is from about 0.1 to 0.6 for cytochrome C.
12. Bundle of hollow fibres according to one of Claims 1 to 11, in which the hollow fibres consist mainly of polyarylsulphone.
13. Bundle of hollow fibres according to Claim 12, in which the polyarylsulphone is a polysulphone, a polyethersulphone or a mixture of said two polyarylsulphones.
14. Device for treating blood or plasma by extracorporeal circulation, comprising a bundle of hollow fibres according to one of Claims 1 to 13.
15. Process for producing a bundle of hollow fibres consisting mainly of polyarylsulphone, useful as a semi-permeable membrane in a device for extracorporeal treatment of blood, the method comprising the following steps:
a) preparing a bundle of hollow fibres with a heterogeneous distribution of fibres within the bundle insofar as the density of the hollow fibres is higher in certain zones of the bundle than in other zones;
b) mounting the bundle of hollow fibres in a tubular casing comprising two axial openings;
c) causing a hot, dry gas that is chemically inert towards the hollow fibres, preferably hot, dry air, to circulate through the bundle of hollow fibres, not held at its ends, at a temperature and flow rate that are suitable to cause geometrical heterogeneity of the hollow fibres in the bundle as regards the internal diameter and wall thickness of the hollow fibres;
d) stopping the hot, dry gas from circulating when the geometrical heterogeneity of the hollow fibres has been obtained.
a) preparing a bundle of hollow fibres with a heterogeneous distribution of fibres within the bundle insofar as the density of the hollow fibres is higher in certain zones of the bundle than in other zones;
b) mounting the bundle of hollow fibres in a tubular casing comprising two axial openings;
c) causing a hot, dry gas that is chemically inert towards the hollow fibres, preferably hot, dry air, to circulate through the bundle of hollow fibres, not held at its ends, at a temperature and flow rate that are suitable to cause geometrical heterogeneity of the hollow fibres in the bundle as regards the internal diameter and wall thickness of the hollow fibres;
d) stopping the hot, dry gas from circulating when the geometrical heterogeneity of the hollow fibres has been obtained.
16. Process according to Claim 15, in which the temperature of the gas at the inlet to the bundle of hollow fibres is 75°C to 130°C.
17. Process according to Claim 15, in which the temperature of the gas at the inlet to the bundle of hollow fibres is 90°C to 120°C.
18. Process according to Claim 15, in which the flow rate of the gas at the inlet to the bundle of hollow fibres is 2 to 5 m3 per hour.
19. Process according to Claim 15, in which the duration of step (c) is of the order of 1 to 4 hours.
20. Process according to Claim 15, in which circulation of the gas is stopped when the temperature of the gas at the outlet from the tubular casing is substantially equal to the temperature of the gas at the inlet to the tubular casing.
21. Process according to Claim 15, in which step (a) comprises a fibre guiding step:
.cndot. carried out using a fibre guiding device comprising:
.cndot. a drum (20) with a winding surface (21) with a regular polygonal cross section that can be rotated about its axis of symmetry (22), each side of the winding surface (21) of drum (20) being provided with a semi-cylindrical trough (23), the axes (24) of the troughs (23), which are aligned about the drum (20), being coplanar; and .cndot. at least one carriage (30) carrying at least one set of rollers located a certain distance from the drum (20), to guide and supply at least one hollow fibre (40) to the troughs (23) and wind the hollow fibre (40) onto the drum (20), each carriage (30) being movable in a reciprocating motion perpendicular to the plane containing the axes (24) of troughs (23), with a variable amplitude not exceeding the diameter of the troughs (23);
.cndot. consisting of winding at least one hollow fibre (40), which is supplied and guided by at least one set of rollers carried by at least one carriage (30), around the drum (20) into the troughs (23) turning with the drum (20), to fill the troughs (23).
.cndot. carried out using a fibre guiding device comprising:
.cndot. a drum (20) with a winding surface (21) with a regular polygonal cross section that can be rotated about its axis of symmetry (22), each side of the winding surface (21) of drum (20) being provided with a semi-cylindrical trough (23), the axes (24) of the troughs (23), which are aligned about the drum (20), being coplanar; and .cndot. at least one carriage (30) carrying at least one set of rollers located a certain distance from the drum (20), to guide and supply at least one hollow fibre (40) to the troughs (23) and wind the hollow fibre (40) onto the drum (20), each carriage (30) being movable in a reciprocating motion perpendicular to the plane containing the axes (24) of troughs (23), with a variable amplitude not exceeding the diameter of the troughs (23);
.cndot. consisting of winding at least one hollow fibre (40), which is supplied and guided by at least one set of rollers carried by at least one carriage (30), around the drum (20) into the troughs (23) turning with the drum (20), to fill the troughs (23).
22. Process according to Claim 21, in which the reciprocating motion of the carriage or carriages (30) varies with time during formation of the bundles of hollow fibres, as follows:
a) initially, to fill the bottom of the troughs (23), the reciprocating motion amplitude is small;
b) then the reciprocating motion ,amplitude varies regularly, increasing to reach a plateau corresponding to a value less than the diameter of the troughs (23);
c) then the reciprocating motion amplitude is kept constant for a certain period; and d) finally, the reciprocating motion amplitude varies regularly, reducing to a very small value;
and in that, during steps (a) to (d) above for forming bundles of hollow fibres, the speed of displacement of each carriage (30) is substantially constant and the speed of rotation of the drum (20) is substantially constant.
a) initially, to fill the bottom of the troughs (23), the reciprocating motion amplitude is small;
b) then the reciprocating motion ,amplitude varies regularly, increasing to reach a plateau corresponding to a value less than the diameter of the troughs (23);
c) then the reciprocating motion amplitude is kept constant for a certain period; and d) finally, the reciprocating motion amplitude varies regularly, reducing to a very small value;
and in that, during steps (a) to (d) above for forming bundles of hollow fibres, the speed of displacement of each carriage (30) is substantially constant and the speed of rotation of the drum (20) is substantially constant.
23. Process according to Claim 21 or Claim 22, in which the fibre guiding device comprises two carriages (30) carrying at least one set of guide rollers, the two carriages (30) moving in a reciprocating motion in phase opposition.
24. Process according to Claim 21, Claim 22 or Claim 23, in which each carriage (30) makes an odd number of from 3 to 15 movements in one direction per rotation of the drum (20).
25. Process according to Claim 24, in which each carriage (30) carries out 7.1 movements in one direction per rotation of the drum (20).
26. Method for measuring the local hydraulic permeability Lpi of a sub-group of hollow fibres of a bundle of hollow fibres mounted in a tubular casing comprising a lateral opening at one of its ends, the bundle of hollow fibres being fixed in the casing by an adhesive seal at each of its ends, and the adhesive seals having been cut perpendicular to the longitudinal axis of the bundle to open the fibres, in which it comprises the steps of:
.cndot. placing the casing containing the bundle in a vertical position, the lateral opening being disposed towards the bottom, and sealing the lower end of the casing;
.cndot. applying a graduated, calibrated tube (12) in a vertical position over a portion of the upper cut surface of the bundle, to form a sealed connection between them;
.cndot. passing a liquid at a defined flow rate through the lateral opening of the casing;
.cndot. measuring the time t taken by the liquid to pass from a first graduation to a second graduation of the graduated tube (12) and calculating the local hydraulic permeability Lpi from the formula Lpi = V/tPSi in which:
- V represents the volume of the tube between the two graduations;
- t represents the time that the liquid takes to pass from the first graduation to the second graduation of the tube;
- P represents the transmembrane pressure;
- Si represents the surface area of the hollow fibres belonging to the sub-group under consideration for the measurement.
.cndot. placing the casing containing the bundle in a vertical position, the lateral opening being disposed towards the bottom, and sealing the lower end of the casing;
.cndot. applying a graduated, calibrated tube (12) in a vertical position over a portion of the upper cut surface of the bundle, to form a sealed connection between them;
.cndot. passing a liquid at a defined flow rate through the lateral opening of the casing;
.cndot. measuring the time t taken by the liquid to pass from a first graduation to a second graduation of the graduated tube (12) and calculating the local hydraulic permeability Lpi from the formula Lpi = V/tPSi in which:
- V represents the volume of the tube between the two graduations;
- t represents the time that the liquid takes to pass from the first graduation to the second graduation of the tube;
- P represents the transmembrane pressure;
- Si represents the surface area of the hollow fibres belonging to the sub-group under consideration for the measurement.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR0013920 | 2000-10-30 | ||
| FR0013920A FR2815886B1 (en) | 2000-10-30 | 2000-10-30 | HOLLOW FIBER BEAM FOR AN APPARATUS FOR THE EXTRACORPORAL TREATMENT OF BLOOD AND PLASMA AND ITS MANUFACTURING PROCESS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2360406A1 true CA2360406A1 (en) | 2002-04-30 |
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| Application Number | Title | Priority Date | Filing Date |
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| CA002360406A Abandoned CA2360406A1 (en) | 2000-10-30 | 2001-10-29 | Bundle of hollow fibres for a device for extracorporeal treatment of blood and plasma, and process for its production |
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| US (2) | US6773591B2 (en) |
| EP (1) | EP1201293A1 (en) |
| JP (1) | JP4456307B2 (en) |
| AU (1) | AU8363301A (en) |
| CA (1) | CA2360406A1 (en) |
| FR (1) | FR2815886B1 (en) |
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| SE460521B (en) | 1987-08-31 | 1989-10-23 | Gambro Dialysatoren | PERMSELECTIVE ASYMMETRIC MEMBRANE AND PROCEDURES FOR ITS PREPARATION |
| JPH01310668A (en) | 1988-06-09 | 1989-12-14 | Nikkiso Co Ltd | Hollow yarn type blood cleaning device |
| US5084349A (en) | 1988-09-07 | 1992-01-28 | Terumo Kabushiki Kaisha | Hollow cellulose fibers, method for making, and fluid processing apparatus using same |
| US5578267A (en) * | 1992-05-11 | 1996-11-26 | Minntech Corporation | Cylindrical blood heater/oxygenator |
| BR8907905A (en) | 1989-10-01 | 1992-09-29 | Minntech Corp | CYLINDRIC BLOOD HEATER / OXYGENER |
| DE4038247A1 (en) | 1990-11-30 | 1992-06-04 | Akzo Gmbh | CELLULOSE HOLLOW DIALYSIS THREAD |
| US5176725A (en) | 1991-07-26 | 1993-01-05 | Air Products And Chemicals, Inc. | Multiple stage countercurrent hollow fiber membrane module |
| DE4230077A1 (en) | 1992-09-09 | 1994-03-10 | Akzo Nv | Polysulfone membrane and process for its preparation |
| JP3392141B2 (en) | 1992-11-16 | 2003-03-31 | バクスター インターナショナル インコーポレイテッド | High flow rate hollow fiber membrane |
| US5645778A (en) | 1992-11-16 | 1997-07-08 | Althin Medical, Inc. | Process of making a cellulose acetate semipermeable membrane |
| US5320747A (en) * | 1992-12-21 | 1994-06-14 | Claude Laval Corp. | Apparatus for removing solid matter from fluid systems |
| DE59308928D1 (en) | 1992-12-30 | 1998-10-01 | Hoechst Ag | Semipermeable membranes made of homogeneously miscible polymer alloys |
| US5700372A (en) * | 1994-09-02 | 1997-12-23 | Terumo Kabushiki Kaisha | Dialyzer with a constricted part made of a material capable of swelled by dializing liquid |
| CA2165221C (en) | 1994-12-16 | 2003-09-23 | Kazuhisa Shibata | Module for blood purification, blood purification membrane and its production |
| DE19514540A1 (en) | 1995-04-20 | 1996-10-24 | Gambro Dialysatoren | Membrane sterilizable with heat |
| DE19518624C1 (en) * | 1995-05-24 | 1996-11-21 | Akzo Nobel Nv | Synthetic separation membrane |
| US5693694A (en) | 1996-03-20 | 1997-12-02 | W.R. Grace & Co.-Conn. | Low and medium flux membranes |
| EP0807460A1 (en) | 1996-05-15 | 1997-11-19 | Akzo Nobel N.V. | Cellulosic dialysis membrane |
| NL1005432C2 (en) | 1997-03-04 | 1998-09-07 | Stork Friesland Bv | Membrane filtration module and like modules comprising membrane filtration system. |
| NL1005430C2 (en) * | 1997-03-04 | 1998-09-07 | Stork Friesland Bv | Membrane filtration module and like modules comprising membrane filtration system. |
| US6258321B1 (en) * | 1999-05-06 | 2001-07-10 | Dideco S.P.A. | Apparatus and method for cardioplegia delivery |
-
2000
- 2000-10-30 FR FR0013920A patent/FR2815886B1/en not_active Expired - Fee Related
-
2001
- 2001-10-24 EP EP01204054A patent/EP1201293A1/en not_active Withdrawn
- 2001-10-25 AU AU83633/01A patent/AU8363301A/en not_active Abandoned
- 2001-10-29 US US09/984,225 patent/US6773591B2/en not_active Expired - Fee Related
- 2001-10-29 CA CA002360406A patent/CA2360406A1/en not_active Abandoned
- 2001-10-30 JP JP2001370708A patent/JP4456307B2/en not_active Expired - Fee Related
-
2004
- 2004-06-24 US US10/874,303 patent/US7250108B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP4456307B2 (en) | 2010-04-28 |
| JP2002239348A (en) | 2002-08-27 |
| US6773591B2 (en) | 2004-08-10 |
| US20040232062A1 (en) | 2004-11-25 |
| US7250108B2 (en) | 2007-07-31 |
| FR2815886B1 (en) | 2002-12-06 |
| AU8363301A (en) | 2002-05-09 |
| EP1201293A1 (en) | 2002-05-02 |
| US20020079260A1 (en) | 2002-06-27 |
| FR2815886A1 (en) | 2002-05-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |