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WO2002011855A1 - Filtre - Google Patents

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Publication number
WO2002011855A1
WO2002011855A1 PCT/GB2001/003474 GB0103474W WO0211855A1 WO 2002011855 A1 WO2002011855 A1 WO 2002011855A1 GB 0103474 W GB0103474 W GB 0103474W WO 0211855 A1 WO0211855 A1 WO 0211855A1
Authority
WO
WIPO (PCT)
Prior art keywords
filter
section
liquid
downstream
upstream
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB2001/003474
Other languages
English (en)
Inventor
Terence Gourlay
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
PHERESIS RESEARCH Ltd
Original Assignee
PHERESIS RESEARCH Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by PHERESIS RESEARCH Ltd filed Critical PHERESIS RESEARCH Ltd
Priority to AU2001275750A priority Critical patent/AU2001275750A1/en
Publication of WO2002011855A1 publication Critical patent/WO2002011855A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
    • A61M1/02—Blood transfusion apparatus
    • A61M1/0209—Multiple bag systems for separating or storing blood components
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
    • A61M1/02—Blood transfusion apparatus
    • A61M1/0209—Multiple bag systems for separating or storing blood components
    • A61M1/0218—Multiple bag systems for separating or storing blood components with filters
    • A61M1/0222—Multiple bag systems for separating or storing blood components with filters and filter bypass
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
    • A61M1/02—Blood transfusion apparatus
    • A61M1/0209—Multiple bag systems for separating or storing blood components
    • A61M1/0231—Multiple bag systems for separating or storing blood components with gas separating means, e.g. air outlet through microporous membrane or gas bag
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
    • A61M1/36—Other treatment of blood in a by-pass of the natural circulatory system, e.g. temperature adaptation, irradiation ; Extra-corporeal blood circuits
    • A61M1/3621—Extra-corporeal blood circuits
    • A61M1/3627—Degassing devices; Buffer reservoirs; Drip chambers; Blood filters
    • A61M1/3633—Blood component filters, e.g. leukocyte filters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2201/00—Details relating to filtering apparatus
    • B01D2201/20—Pressure-related systems for filters
    • B01D2201/202—Systems for applying pressure to filters

Definitions

  • the present invention relates to a filter for filtering of a solid from a liquid, for instance filtering of leukocytes from blood to yield leukoreduced blood, and is particularly, although not exclusively, concerned with a process by which blood filters can be modified to enhance blood recovery.
  • Human blood transfusion that involves the transfer of donor leukocytes can be harmful to the patient.
  • the donor leukocytes can give rise to febrile reactions or immune system suppression in the patient.
  • the donor leukocytes can also result in the transmission of harmful infectious viruses to the patient, examples being human immunodeficiency virus (HIV), hepatitis, Epstein- Barr and cytomegalovirus.
  • HIV human immunodeficiency virus
  • hepatitis hepatitis
  • Epstein- Barr Epstein- Barr
  • cytomegalovirus examples being human immunodeficiency virus
  • blood transfusions involving the donor leukocytes can cause an immunological response in the patient which leads to future blood transfusions being rejected.
  • a typical blood filter device for yielding leukoreduced blood has a filter housing which defines a filter chamber which is divided into upstream and downstream sides by a blood filter membrane.
  • An inlet port in the housing enables the donor blood to be conveyed into the upstream side and an outlet port enables the filtered blood to be conveyed from the downstream side to a collection bag.
  • Blood filters by their nature are made of hydrophilic materials. Once filtration is complete, blood is recovered by allowing air into the upstream side of the filter housing. This air may potentially become contaminated. Moreover, whilst this technique allows the displacement of the upstream blood volume, the filter membrane, being hydrophilic and coated in blood, resists the passage of air.
  • the liquid can only be displaced with "considerable" pressure, air passing only when the bubble point pressure of the membrane is exceeded. This is impractical and potentially dangerous in clinical applications. Failure to completely drain blood filters leads to significant amounts of blood being lost to waste during both clinical transfusion and blood processing during the collection procedure.
  • WO-A-9524255 Hemasure, Inc.
  • a filter device for producing leukoreduced blood in which the hydrophilic multi-sheet filter membrane is apertured therethrough and an open-ended tube received in the aperture such that the tube open ends are respectively disposed in the upstream and downstream sides of the filter chamber.
  • the upstream open end of the tube is closed by a hydrophobic filter whilst the downstream open end is left uncovered.
  • the hydrophobic filter prevents blood passing from the upstream side to the downstream side through the tube.
  • the hydrophobic filter permits the passage of air from the upstream side to the downstream side when the blood in the upstream side has receded sufficiently for the hydrophobic filter to be exposed.
  • the filter device disclosed in WO-A-9524255 is highly complex, requiring close tolerances between the tube and the filter membrane, on the one hand, and the tube and the filter housing, on the other hand. If an ineffective seal is formed between the tube and the aperture in the filter membrane, donor blood can pass downstream into the downstream side with minimal leukoreduction. To combat this potential problem, highly complex mechanical solutions are needed.
  • a filter structure for filtering a solid from a liquid having a body which:- has an upstream outer surface, has a downstream outer surface, is permeable to the liquid, is adapted to selectively filter the solid from the liquid on passage therethrough in a downstream direction, and is impermeable, or substantially impermeable, to a vent gas when wetted by the liquid, a section of the body which extends from the upstream outer surface to the downstream outer surface being impermeable, or substantially impermeable, to the liquid and permeable to the vent gas so as to provide a pathway for the vent gas to pass in a downstream direction through the body.
  • the filter structure may be a single filter element or sheet or comprise a plurality of filter elements/sheets juxtaposed with one another.
  • a filter sheet for filtering a solid from a liquid having a body which has an upstream outer surface and a downstream outer surface, a first section of the body extending from the upstream outer surface to the downstream outer surface being permeable to the liquid, adapted to selectively filter the solid from the liquid on passage therethrough in a downstream direction and impermeable, or substantially impermeable, to a vent gas when wetted by the liquid, and a second section of the body extending from the upstream outer surface to the downstream outer surface being impermeable, or substantially impermeable, to the liquid and permeable to the vent gas so as to provide a pathway for the vent gas to pass in a downstream direction through the body.
  • substantially impermeable impermeable to a practical extent so that, in its context with reference to the vent gas, insufficient vent gas is able to pass through the wetted body or first section in the downstream direction to recover the filtrate and so that, in its context with reference to the liquid, sufficient vent gas is able to pass through the section or the second section for recovery of the filtrate.
  • a deviation from absolute impermeability which does not prevent the invention performing its function.
  • the body of the filter structure and the first section of the filter sheet are impermeable, or substantially impermeable, to the vent gas when the filter structure body/first section is wetted by the liquid and the pressure of the vent gas is less than the bubble point pressure of the filter structure body/first section for the liquid.
  • the section of the filter structure and the second section of the filter sheet are permeable to the vent gas at this vent gas pressure.
  • the filter structure or sheet is preferably for filtering a solid from an aqueous liquid, more preferably for filtering cellular material from a body liquid and most preferably for filtering leukocytes from blood.
  • the vent gas is typically air.
  • a filter device for filtering a solid from a liquid having a housing which defines a chamber and which has an inlet and an outlet to the chamber for the liquid and a filter structure according to the first aspect of the invention mounted in the chamber so that the upstream outer surface faces the inlet and the downstream outer surface faces the outlet.
  • a filter device for filtering a solid from a liquid having a housing which defines a chamber and which has an inlet and an outlet to the chamber for the liquid and a filter sheet according to the second aspect of the invention mounted in the chamber so that the upstream outer surface faces the inlet and the downstream outer surface faces the outlet.
  • the housing of the filter device has a vent to the chamber for the vent gas to which the upstream outer surface faces towards.
  • the impregnated section of the filter structure may be made by chemical means as may be the second section of the filter sheet. For instance, in the case of the impregnated section of the filter structure, by applying the material to the body on one of the outer surfaces thereof and allowing the material to pass through the body to the other outer surface to impregnate or coat the body.
  • the material is preferably applied in a liquid or vapour form, for example as one or more liquid droplets or in an aerosol formulation.
  • the impregnated section of the filter structure (when a single filter element) and the second section of the filter sheet are preferably an integral hydrophobic vent.
  • An integral vent of this nature can be created by treating a small area of the filter medium chemically to create a hydrophobic channel, connecting the upstream and downstream portions of the filter chamber.
  • chemical insertion of a hydrophobic vent will involve the use of a penetrative aerosol applicator of known design containing the hydrophobic chemical of known formula.
  • a hydrophobic vent designed for enhancing blood recovery during transfusion, collection or processing.
  • the vent may be provided by chemical means. Such a vent will permit air to pass through and de-prime the filter and administration/processing tubing, increasing the volume of blood recovered after processing.
  • the hydrophobic vent may be provided by applying a hydrophobic chemical to and through the filter medium using an aerosol applicator. Alternately, the hydrophobic vent may be provided by applying a hydrophobic chemical to and through the filter medium using a fluid dropper.
  • the expanse of the hydrophobic vent may be limited by the shape of the nozzle of the applicator. The position and number of such vents is not limited in number or position.
  • the system may be used in the processing of materials other than blood.
  • a process for enhancing the recovery of blood when processing or administering it which consists of the introduction of a hydrophobic vent into the filter medium of the blood filter used during this procedure.
  • This hydrophobic channel is chemical in structure. Chemical channelling is introduced by spraying a hydrophobic chemical onto and through a discrete section or sections of the filter medium. The hydrophobic channel permits the passage of air through the filter medium, thus permitting the filter to de-prime, enhancing the recovery of blood by the quantity of blood normally disposed of due to the inability to de-prime filters in the absence of a hydrophobic vent.
  • a filter sheet for filtering a solid from an aqueous liquid having a body with an upstream outer surface and a downstream outer surface, the body having first and second sections extending from the upstream outer surface to the downstream outer surface, the first section being a hydrophilic filtering section and the second section being a hydrophobic vent section.
  • This filter sheet may replace the filter sheet in the filter device of the fourth aspect of the invention.
  • hydrophilic may be defined as meaning able to be wetted out so as to initiate and sustain bulk liquid flow under a pressure generated by a gravity head of approximately 1 m.
  • hydrophobic may be defined as meaning unable to wet out under pressure generated by a gravity head of approximately 1 m but which will allow air flow.
  • hydrophilic and hydrophobic may also be defined using the concept of surface tension of liquids and the Critical Wetting Surface Tension (CWST) of a material.
  • CWST Critical Wetting Surface Tension
  • the CWST has to be greater than the surface tension of the liquid. Accordingly, a filter made from a material with a CWST greater than the surface tension of a blood preparation to be filtered will wet out and be classed as "hydrophilic”. Conversely, a material with a CWST less than the surface tension of the blood preparation will not wet out and be classed as "hydrophobic".
  • a typical blood (red cell) preparation has a surface tension of around 68-72 dynes/cm. In practice, the lower the CWST of the filter material vis- a-vis the surface tension of the blood preparation the better.
  • the hydrophobic material for the hydrophobic section may be formed from a mixture of paraffin wax and an oleophobic hydrocarbon.
  • each aspect of the invention can be combined with one or more of the features of another aspect of the invention.
  • FIGURE 1 is a perspective view of a filtering apparatus comprising a filter device in accordance with the present invention
  • FIGURE 2 is an exploded perspective view of the filter device showing the upstream and downstream halves of a filter housing of the filter device and the individual filter sheets contained therein:
  • FIGURES 3A and 3B are internal views of the upstream and downstream halves of the filter housing, respectively.
  • FIGURES 4A and 4B are diagrammatic views of different stages of the operation of the filter device.
  • FIGURE 1 there is shown a gravity-driven filtering apparatus 1 for filtering leukocytes from a source of donor blood preparation 3 contained in a sealed, sterile source bag 5 preparatory to transfusing the donor blood preparation 3 to a human patient.
  • the donor blood preparation 3 is not whole blood.
  • the blood plasma in the whole blood taken from the human donor is separated off by centrifuging and the cellular component of the whole blood, i.e. leukocytes, erythrocytes and thrombocytes, is typically added to an aqueous liquid such as the so-called 'optimal additive solution', or OAS for short, as is known in the art.
  • OAS 'optimal additive solution'
  • the filtering apparatus 1 comprises a sterile, sealed filter device 7 having a transparent filter housing 9 having an internal chamber within which a filter media for filtering leukocytes from the donor blood preparation 3 is disposed, as will be described in more detail hereinafter.
  • the filter housing 9 is provided with an inlet port 11 (see FIGURE 2) to which a downstream end of a sterile inlet tube 13 is sealably connected.
  • An upstream end of the inlet tube 13 is sealably connected to a sterile hollow connector 15 having a sharp tip 17 which, when not in use, is covered by a sterile protective cap 19.
  • a sterile protective cap 19 Slidably mounted on the inlet tube 13 is an inlet clamp 21 having a clamping state which closes off the lumen of the inlet tube 13 and an unclamping state which leaves the lumen open.
  • the protective cap 19 is removed from the connector 15 and the sharp tip 17 used to pierce a relatively short, closed outlet tube 22 located at the base of the source bag 5 and in fluid communication with the donor blood preparation 3.
  • the connector 15 is sealably connected to the outlet tube 22.
  • SCDTM Sterile Connecting Device
  • the filter housing 9 has an outlet port 23 to which an upstream end of a sterile outlet tube 25 is sealably connected.
  • the outlet tube 23 has a downstream end which in turn is sealably connected to an inlet port 27 located at the top of a sealed, sterile collection bag 29 and in fluid communication with the interior thereof.
  • Slidably mounted on the outlet tube 25 is an outlet clamp 31 which is adapted to close off and open the lumen of the outlet tube 25 in the same manner as the inlet clamp 21.
  • the top of the collection bag 29 is further provided with an outlet port 33 in fluid communication with the interior of the collection bag 29.
  • An interior of a sterile satellite bag 35 is placed in fluid communication with the interior of the collection bag 29 through a sterile auxiliary tube 37 having its upstream end sealably connected to the outlet port 33 of the collection bag 29 and its downstream end sealably connected to an inlet port 39 of the satellite bag 35 at the top thereof.
  • an auxiliary clamp 41 is slidably mounted on the auxiliary tube 37 to open and close the lumen thereof.
  • the filtering apparatus 1 operates as follows. Firstly, the individual clamps
  • the protective cap 19 is then removed from the connector 15 and the sharp tip 17 used to puncture the outlet tube 22 of the source bag 5 to place the inlet tube 13 in fluid communication with the donor blood preparation 3 in the source bag 5.
  • the source bag 5 is then hung on a transverse bar of a stand (not shown) so that the filtering apparatus 1 is suspended from the stand.
  • the collection bag 29 is laid flat, e.g. on a base of the stand.
  • the conveyance of the donor blood preparation 3 through the filtering apparatus 1 into the collection bag 29 results in air contained in the inlet and outlet tubes 13, 25 and the filtering device 7 being conveyed into the collection bag 29.
  • the inlet and outlet clamps 21 , 31 are returned to their clamping state, with the outlet clamp 31 being located in close proximity to the inlet port 27 of the collection bag 29.
  • the auxiliary clamp 41 is then moved to its unclamping state and the collection bag 29 squeezed to express the air contained therein into the satellite bag 35 via the auxiliary tube 37.
  • the auxiliary clamp 41 is then returned to its clamping state.
  • the collection bag 29 can be shaken gently and the auxiliary clamp 41 moved back to the unclamping state so that some of the leukoreduced blood is conveyed into the auxiliary tube 37.
  • the auxiliary clamp 41 is then moved back to the clamping state and the tube 37 heat sealed at its opposed ends and at positions intermediate the ends so as to give sealed tube segments containing samples of the leukoreduced blood. These samples can be analyzed to determine whether the donor blood preparation 3 has been leukoreduced to a sufficient degree for use in a blood transfusion.
  • the collection and satellite bags 29, 35 are separated from the rest of the filtering apparatus 1 which is disposed of.
  • the auxiliary tube 37 and satellite bag 35 are then separated from the collection bag 29 to enable the collection bag 29 to be connected to a blood transfusion line through one or other of a pair of closed auxiliary outlet ports 43a, 43b on the collection bag 29, sample analysis permitting, of course.
  • the filter housing 9 has a transparent, cylindrical upstream half 45 and a transparent, cylindrical downstream half 47.
  • the upstream and downstream halves 45, 47 are formed by injection moulding of a blood compatible plastics material, non-limiting examples being an acrylic plastic, such as acrylonitrile-butadiene-styrene (ABS), and polycarbonate.
  • ABS acrylonitrile-butadiene-styrene
  • the upstream and downstream halves 45, 47 have complementary outer circumferences which enable the halves 45, 47 to be connected by a push-fit.
  • the connection of the outer circumferences of the upstream and downstream halves 45, 47 is sealed either through an O-ring (not shown), an adhesive seal or by welding. Other sealing methods could, of course, be adopted as will be understood by the person skilled in the art.
  • the upstream half 45 of the filter housing 9 is integrally formed with the inlet port 11 whereas the downstream half 47 is integrally formed with the outlet port 23.
  • the upstream half 45 is also integrally formed with a projection 49 having an eyelet 51 through which the filter device 7 can be hung in position on the inlet tube 13, as shown in FIGURE 1.
  • a cylindrical filter chamber 53 is defined between them.
  • a series of circular hydrophilic filter sheets 55a, 55b, 55c Disposed in the filter chamber 53 is a series of circular hydrophilic filter sheets 55a, 55b, 55c that are juxtaposed into a filter stack 57.
  • the filter sheets 55a, 55b, 55c are sealably secured in place in the filter chamber 53 through a precision interference fit between the outer circumferences of the filter sheets 55a, 55b, 55c and an inner circumferential wall 59 of the filter chamber 53.
  • each filter sheet 55a, 55b, 55c has an upstream face 61 and a downstream face 63, with the upstream faces 61 facing the inlet port 11 and the downstream faces 63 facing the outlet port 23.
  • the outermost filter sheets 55a, 55c of the filter stack 57 present upstream 65 and downstream faces 67 of the filter stack 57.
  • the filter stack 57 divides the filter chamber 53 into an upstream compartment 69, in fluid communication with the inlet port 11 and the upstream face 65 of the filter stack 57, and a downstream compartment 71 , in fluid communication with the outlet port 23 and the downstream face 67 of the filter stack 57.
  • the filter stack 57 has 3 distinct stages, namely an upstream flow enhancement stage (FES) 72 consisting of the two outermost filter sheets 55a at the upstream end, a central leukocyte depleting stage (LDS) 74 consisting of the seven core filter sheets 55b and a downstream particle trap stage (PTS) 76 consisting of the two outermost filter sheets 55c at the downstream end.
  • FES upstream flow enhancement stage
  • LDS central leukocyte depleting stage
  • PTS downstream particle trap stage
  • the filter sheets 55a, 55b, 55c are of varying filtering grades, that is to say, the filter sheets 55a, 55b, 55c have different porosities. More particularly, the filter sheets 55a of the FES 72 have a larger mean pore size than the mean pore size of the filter sheets 55b, 55c of the LDS 74 and the PTS 76. Conversely, the filter sheets 55c of the PTS 76 have a smaller mean particle size than the mean pore size of the filter sheets 55a, 55b of the FES 72 and LDS 74. In addition, the filter sheets 55a, 55c of the FES 72 and PTS 76 have a lower bubble point pressure than the filter sheets 55b of the LDS 74.
  • the FES 72 functions to remove gels and clots that may have formed in the donor blood preparation 3 which, if not removed, would block the finer filter sheets 55b of the LDS 74.
  • the filter sheets 55b of the LDS 74 are of the same filtering grade, that is to say, have essentially the same mean pore size.
  • the filter sheets 55b may be of different porosities, e.g. arranged so that the mean pore size in the LDS 74 decreases in the downstream direction.
  • the mean pore size of the filter sheets 55b is such as to permit passage of erythrocytes whilst filtering leukocytes on downstream passage of the donor blood preparation 3 through the LDS 74.
  • the PTS 76 functions to filter out particles entrained in the donor blood preparation 3, e.g. foreign body particles picked up during the downstream passage of the donor blood preparation 3 through the FES 72 and/or the LDS 74.
  • the PTS 76 may function to remove particles having a particle size of approximately 10 ⁇ m and above.
  • the filter sheets 55a of the FES 72 are preferably of a polyester which is modified to improve its wettability, i.e. to increase its Critical Wetting Surface Tension (CWST).
  • the filter sheets 55b of the LDS 74 are preferably formed from glass microfibres, although other hydrophilic materials can, of course, be used, for instance a non-woven polyester such as polybutylene terephthalate (PBT) or polyethylene terephthalate (PET) surface-treated to increase its CWST, or a polyurethane etc..
  • PBT polybutylene terephthalate
  • PET polyethylene terephthalate
  • the filter sheets 55b of the LDS 74 are made from glass
  • the filter sheets 55c of the PTS 76 be of a non-glass material which is adapted to filter out any glass picked up by the donor blood preparation 3 on its passage through the filter stack 57.
  • the upstream half 45 of the filter housing 9 has an interior surface 73 in which the inlet port 11 opens and from which a series of baffles 75 project.
  • the baffles 75 act to regulate and smooth the flow of the donor blood preparation 3 from the inlet port 11 into the upstream compartment 69 of the filter housing 9, in particular to cause the donor blood preparation 3 to spread.
  • the upstream face 65 of the filter stack 57 is supported on the baffles 75.
  • the downstream half 47 of the filter housing 9 has an interior surface 77 in which the outlet port 23 opens and from which a series of parallel ribs 79 project.
  • the ribs 79 form a similar function as the baffles 75, namely to regulate and smooth the flow of the filtrate and to support the downstream face 67 of the filter stack 57.
  • the upstream half 45 of the filter housing 9 has an integrally formed air vent 81 adjacent the base thereof and lying on an axis A-A.
  • a hydrophobic membrane or cover 83 is mounted on the interior surface 73 of the upstream half 45 to cover the air vent 81 , thereby preventing donor blood preparation 3 from discharging from the upstream compartment 69 through the air vent 81 while permitting the passage of air into the upstream compartment 69.
  • each hydrophilic filter sheet 55b of the LDS 74 has a hydrophobic section 85 extending through its body from the upstream face 61 to the downstream face 63.
  • the filter sheets 55b of the LDS 74 are arranged so that each hydrophobic section 85 is positioned on the axis A-A thereby being aligned with one another and with the air vent 81.
  • a continuous hydrophobic channel 87 extends through the LDS 74 of the filter stack 57 from the upstream face 61 of the most upstream filter sheet 55b to the downstream face 63 of the most downstream filter sheet 55b, as shown diagrammatically in FIGURES 4A and 4B.
  • the hydrophobic channel 87 functions as a hydrophobic vent through which the donor blood preparation 3 is unable to permeate, at least to a significant extent, but which, when uncovered by donor blood preparation 3, provides a pathway for air to pass from the upstream compartment 69 of the filter housing 9 to the downstream compartment 71 , even though having been wetted by the donor blood preparation 3.
  • the hydrophilic material of the filter sheets 55b of the LDS 74 is wetted by the donor blood preparation 3
  • the passage of air therethrough is prevented, unless the bubble pressure point of the filter sheets 55b is exceeded.
  • the hydrophobic channel 87 thus enables the passage of air into the downstream compartment 71 of the filter housing 9 to assist in the recovery of the leukoreduced blood, as will be understood more clearly shortly hereinafter.
  • the bubble point pressure of the filter sheets 55a, 55c of the FES 72 and PTS 76 is such that the donor blood preparation 3 will clear from them under the pressure of the gravity head. Accordingly, it is not necessary for these filter sheets 55a, 55c to be provided with a hydrophobic section, although they may include it if desired, for example for manufacturing convenience.
  • the hydrophobic sections 85 of the filter sheets 55b are formed by impregnating the hydrophilic material in that section with a hydrophobic material. This may be done in a number of ways. As examples there may be mentioned the following:-
  • the hydrophobic sections 85 of the filter sheets 55b can be provided concurrently by stacking the untreated filter sheets 55b into the LDS 74 and then applying the hydrophobic chemical to either the upstream or downstream face of the stack so as to cause the chemical to penetrate into and through the stack to the opposite face.
  • the material of the hydrophobic section 85 has a Critical Wetting Surface
  • the hydrophobic material has a CWST in the range of 19-67 dynes/cm, most preferably towards the lower end of this range.
  • the hydrophobic material has a CWST corresponding closely to that of polytetrafluoroethylene (PTFE), namely approximately 19-21 dynes/cm.
  • PTFE polytetrafluoroethylene
  • FIGURES 4A and 4B diagrammatically illustrate the function of the hydrophobic channel 87 in the filter stack 57.
  • FIGURE 4A shows the filter device 7 in an early stage of the filtering process in which the upstream compartment 69 of the filter housing 9 is filled to a level above the level of the axis A-A whereby the hydrophobic membrane 83 over the air vent 81 and the upstream end of the hydrophobic channel 87 are covered by the donor blood preparation 3.
  • the donor blood preparation 3 permeates through the hydrophilic section of the filter stack 57 in a downstream direction, as indicated by the full-line arrows, and the resultant leukoreduced blood 89 is deposited in the downstream compartment 71 for discharge from the outlet port 23.
  • the passage of air through the filter stack 57 is prevented due to the hydrophilic material thereof being wetted by the donor blood preparation 3.
  • FIGURE 4B shows a terminal stage of the filtering process in which the level of the donor blood preparation 3 in the upstream compartment 69 has receded to expose the hydrophobic membrane 83 and the upstream end of the hydrophobic channel 87.
  • air at the ambient pressure of the local environment about the filter apparatus 1 e.g. atmospheric pressure
  • the amount of leukoreduced blood 89 recovered from the filter device 7 and downstream processing tubing 25 is increased compared to the case where no hydrophobic vent 87 is provided.
  • the air vent 81 While it is preferable for the air vent 81 to be aligned with the hydrophobic channel 87, it is not strictly necessary. As an example, the air vent 81 could be located at a higher level than the hydrophobic channel 87. The air vent 81 could also be dispensed with and the air provided through the inlet tube 13, e.g. through use of an in-line air vent of the type disclosed in WO-A-9524255 supra.
  • the embodiment of the invention described hereinabove provides a simple solution to the problem of recovering leukoreduced blood from the downstream side of the filtering medium which can be readily adopted in existing filter devices since it does not require a new filter housing.
  • the filter stack 57 was hand assembled and sealed into the filter housing 9 using an O-ring and a clamp.
  • the inlet and outlet tubes 13, 25 have a nominal inner diameter of 3 mm and a volume of approximately 0.07 cm 3 per 1 cm length. Using just tubing, the volume of the 1.25 m outlet tube 25 is only 8.75 cm 3 . This is too small to reliably detect differences using the apparatus of FIGURE 1.
  • the head height of the filtering apparatus 1 as measured from the top of the 100 ml blood preparation 3 in the source bag 5 to the floor was set at 1.75 m with the inlet 11 to the filter device 7 being approximately 0.50 m from the initial blood level in the source bag 5.
  • the LDS 74 was formed by 7 hydrophilic filter sheets 55b made from glass micro-fibre.
  • Each filter sheet 55b (but not the filter sheets 55a, 55c of the FES 72 and PTS 76) was provided with a hydrophobic section 85 by placing 1 drop of a hydrophobic liquid onto it.
  • Each hydrophobic section 85 was 9mm in diameter and placed using a template as close to the outer circumferential edge of the filter sheet 55b as possible.
  • the filter sheets 55b were then placed by hand in the filter housing 9 together with the filter sheets 55a, 55c so that the hydrophobic sections 85 overlapped each other and lay on axis A-A (see FIGURES 2 and 4A).
  • the hydrophobic liquid used was a 80:20 volume/volume mixture of Repellan KFCTM and Repellan HY-NTM (both from Henkel Ltd).
  • Repellan HY-NTM is a dispersion of fatty modified melamine derivative and paraffin.
  • Repellan KFCTM is a perflouro alkyl acrylic co-polymer.
  • One drop was placed, using a pipette, on each filter sheet 55b and the filter sheets 55b were then dried in an oven at 130°C for 5 minutes.
  • the CWST is determined using liquids of different surface tensions and dropping a spot onto the surface to be tested. The surface tension of the liquid that does not soak into the filter is considered to be the CWST of the material.
  • the upstream chamber 69 of the filter device 7 in each test emptied as air entered from the atmosphere via the vent 81.
  • air was seen in the outlet port 23 some 15-20 seconds after the upstream chamber 69 had emptied and this drained the downstream tubing 25 and the drip chamber.
  • the upstream chamber 69 of the filter device 7 not having the hydrophobic-treated LDS 74 emptied of red cells flow into (and out of) the downstream drip chamber ceased virtually immediately and the downstream volume did not drain.
  • the weight of the blood recovered in each filter run was determined and, as shown in the Table below, the inclusion of the hydrophobic section 85 in the filter sheets 55b resulted in an approximate 45% increase in the average weight of leukoreduced blood 89 recovered compared to the case where the hydrophobic section 85 was omitted.
  • the filter structure/sheet may be made by casting from Nylon®, a polyvinylidene fluoride (PVDF), a modified polyether sulphone (PES), cellulose acetate or mixed esters; or as a track etched membrane such a CycloporeTM or NucleporeTM; or from non-woven fibres of e.g. polyester, polypropylene (PP) etc.; or from anodised alumina (AnoporeTM).
  • PVDF polyvinylidene fluoride
  • PES modified polyether sulphone
  • cellulose acetate or mixed esters or as a track etched membrane such a CycloporeTM or NucleporeTM
  • non-woven fibres of e.g. polyester, polypropylene (PP) etc. or from anodised alumina (AnoporeTM).

Landscapes

  • Health & Medical Sciences (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
  • Engineering & Computer Science (AREA)
  • Anesthesiology (AREA)
  • Biomedical Technology (AREA)
  • Hematology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Cardiology (AREA)
  • External Artificial Organs (AREA)

Abstract

Dans un mode de réalisation de l'invention, une structure de filtrante (55b, 57) destinée à filtrer une matière solide contenu dans un liquide (3), comprend un corps qui présente une surface externe amont (61, 65) et une surface externe aval (63, 67), est perméable au liquides, conçue pour filtrer de façon sélective la matière solide contenue dans le liquide lorsqu'il la traverse dans une direction amont-aval, et imperméable, ou sensiblement imperméable, à un gaz de ventilation lorsqu'elle est humidifiée par le liquide. Une partie (85) du corps qui s'étend de la surface externe amont à la surface externe aval, est imperméable, ou sensiblement imperméable, au liquide, et perméable au gaz de ventilation, de manière à matérialiser un passage pour le gaz de ventilation lui permettant de passer à travers le corps dans une direction amont-aval. Dans un deuxième mode de réalisation de l'invention, une feuille filtrante (55b) destinée à filtrer une matière solide contenue dans un liquide (3), comprend un corps qui présente une surface externe amont (61) et une surface externe aval (63). Une première partie du corps s'étendant de la surface externe amont à la surface externe aval, est perméable au liquide, conçue pour filtrer de manière sélective la matière solide contenue dans le liquide lorsqu'il la traverse dans une direction amont-aval, et imperméable, ou sensiblement imperméable, à un gaz de ventilation lorsqu'elle est humidifiée par le liquide. Une seconde partie (85) s'étendant de la surface externe amont à la surface externe aval est imperméable, ou sensiblement imperméable, au liquide, et perméable au gaz de ventilation, de manière à matérialiser un passage pour le gaz de ventilation lui permettant de passer à travers le corps dans une direction amont-aval. La structure ou feuille filtrante comprend ainsi des éléments qui peuvent être traversés par le gaz de ventilation jusqu'au côté aval de la structure ou feuille filtrante, et qui leur permettent d'assister la récupération du filtrat du côté aval.
PCT/GB2001/003474 2000-08-04 2001-08-02 Filtre Ceased WO2002011855A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001275750A AU2001275750A1 (en) 2000-08-04 2001-08-02 A filter

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0019034.8 2000-08-04
GBGB0019034.8A GB0019034D0 (en) 2000-08-04 2000-08-04 A process for enhancing blood recovery when processing blood

Publications (1)

Publication Number Publication Date
WO2002011855A1 true WO2002011855A1 (fr) 2002-02-14

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ID=9896887

Family Applications (1)

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PCT/GB2001/003474 Ceased WO2002011855A1 (fr) 2000-08-04 2001-08-02 Filtre

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Country Link
AU (1) AU2001275750A1 (fr)
GB (1) GB0019034D0 (fr)
WO (1) WO2002011855A1 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003092573A3 (fr) * 2002-05-03 2004-04-01 Gambro Inc Appareil et procede de detection de bacteries dans des produits sanguins
WO2008124678A3 (fr) * 2007-04-06 2008-12-18 Fenwal Inc Systèmes et procédés de filtration de fluides biologiques
US8875893B2 (en) 2010-02-05 2014-11-04 Fenwal, Inc. Medical containers for use in blood collection and processing and medical systems, methods and apparatus for use in blood collection and processing
US9782707B2 (en) 2014-03-24 2017-10-10 Fenwal, Inc. Biological fluid filters having flexible walls and methods for making such filters
US9796166B2 (en) 2014-03-24 2017-10-24 Fenwal, Inc. Flexible biological fluid filters
US9968738B2 (en) 2014-03-24 2018-05-15 Fenwal, Inc. Biological fluid filters with molded frame and methods for making such filters
US10159778B2 (en) 2014-03-24 2018-12-25 Fenwal, Inc. Biological fluid filters having flexible walls and methods for making such filters
US10376627B2 (en) 2014-03-24 2019-08-13 Fenwal, Inc. Flexible biological fluid filters

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3520416A (en) * 1968-02-12 1970-07-14 Pall Corp Liquid and gas-permeable microporous materials and process for making the same
US5472605A (en) * 1994-03-10 1995-12-05 Hemasure, Inc. Filtration device useable for removal of leukocytes and other blood components
WO1998017369A2 (fr) * 1996-10-21 1998-04-30 Pall Corporation Filtre a poche

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3520416A (en) * 1968-02-12 1970-07-14 Pall Corp Liquid and gas-permeable microporous materials and process for making the same
US5472605A (en) * 1994-03-10 1995-12-05 Hemasure, Inc. Filtration device useable for removal of leukocytes and other blood components
WO1998017369A2 (fr) * 1996-10-21 1998-04-30 Pall Corporation Filtre a poche

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003092573A3 (fr) * 2002-05-03 2004-04-01 Gambro Inc Appareil et procede de detection de bacteries dans des produits sanguins
WO2008124678A3 (fr) * 2007-04-06 2008-12-18 Fenwal Inc Systèmes et procédés de filtration de fluides biologiques
US7993531B2 (en) 2007-04-06 2011-08-09 Fenwal, Inc. Biological fluid filtration systems and methods
US8875893B2 (en) 2010-02-05 2014-11-04 Fenwal, Inc. Medical containers for use in blood collection and processing and medical systems, methods and apparatus for use in blood collection and processing
US9682014B2 (en) 2010-02-05 2017-06-20 Fenwal, Inc. Medical containers for use in blood collection and processing and medical systems, methods and apparatus for use in blood collection and processing
US9782707B2 (en) 2014-03-24 2017-10-10 Fenwal, Inc. Biological fluid filters having flexible walls and methods for making such filters
US9796166B2 (en) 2014-03-24 2017-10-24 Fenwal, Inc. Flexible biological fluid filters
US9968738B2 (en) 2014-03-24 2018-05-15 Fenwal, Inc. Biological fluid filters with molded frame and methods for making such filters
US10159778B2 (en) 2014-03-24 2018-12-25 Fenwal, Inc. Biological fluid filters having flexible walls and methods for making such filters
US10183475B2 (en) 2014-03-24 2019-01-22 Fenwal, Inc. Flexible biological fluid filters
US10343093B2 (en) 2014-03-24 2019-07-09 Fenwal, Inc. Biological fluid filters having flexible walls and methods for making such filters
US10376627B2 (en) 2014-03-24 2019-08-13 Fenwal, Inc. Flexible biological fluid filters

Also Published As

Publication number Publication date
AU2001275750A1 (en) 2002-02-18
GB0019034D0 (en) 2000-09-27

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