Liquid purification or separation – Processes – Separating
Reexamination Certificate
1999-03-18
2001-05-15
Kim, John (Department: 1723)
Liquid purification or separation
Processes
Separating
C210S420000, C210S422000, C210S428000, C210S436000, C210S456000, C210S472000
Reexamination Certificate
active
06231770
ABSTRACT:
This application is filed under 35 U.S.C. 371 of PCT/US97/11733 filed Jul. 3, 1997.
TECHNICAL FIELD
This invention relates to the processing of biological fluids such as blood and blood components, particularly to remove undesirable material such as leukocytes from the biological fluid.
BACKGROUND OF THE INVENTION
Many biological fluid processing protocols include filtering the fluid before use. For example, a biological fluid such as blood or at least one blood component can be filtered to remove undesirable material such as debris, gels, microaggregates and/or leukocytes before transfusing the biological fluid. In some protocols, for example, involving bedside administration of blood or blood components, two or more units of blood components such as red blood cells or platelet concentrate can be leukocyte depleted and administered.
However, some of these protocols have suffered from a number of drawbacks. For example, some filters have suffered from clogging, which can prevent or delay the administration of the desired number of units. Alternatively, the use of a separate filter for each unit of blood or blood component can be time consuming, since each filter has to be attached to the blood processing system, and primed. Additionally, some fluid remains in each filter after filtration, and is not transfused to the patient. Thus, the cumulative loss of this held up fluid can be significant.
In an attempt to overcome the problem of clogging, some filter devices include two filter elements, separated by a partition plate, in a single housing. The elements are pressed against the opposite sides of the partition plate, and the elements can be sealed to the opposing sides of the plate. In typical use, blood enters the top of the device, and contacts the partition plate. The blood is then directed to, and passes through, a filter element. The filtered blood subsequently exists the bottom of the device.
These filter devices have also suffered from a number of problems, particularly with respect to difficulty in priming. Air can be trapped in the device, making it difficult to wet either or both of the filter elements. As a result, it may be difficult to pass blood through the device, or blood may flow through one of the filter elements, and little or no blood flows through the other element. Also, since air is trapped, it can be difficult to efficiently drain the device. Additionally, or alternatively, since the device must be of sufficient size to accommodate two filter elements, the device may retain an undesirably large amount of the valuable blood or blood component.
Another disadvantage of at least some of these filters, e.g., those used with one unit of blood, is that they are difficult to include in a centrifugable blood bag system. For example, the filter may be too large to fit in a centrifuge cup, and/or the filter or blood bags may be damaged during centrifugation.
The present invention provides for ameliorating at least some of the disadvantages of the prior art. These and other advantages of the present invention will be apparent from the description as set forth below.
SUMMARY OF THE INVENTION
In accordance with the present invention, a biological fluid filter device is provided having first and second fluid flow paths, with a first porous medium across the first fluid flow path, and a second porous medium across the second fluid flow path, and a space therebetween, wherein the first surface of the first porous medium opposes, and has at least a portion of the surface spaced apart from, the first surface of the second porous medium, and the device essentially lacks a solid partition between the first and second media. For example, the space between the media, which typically has a dimension that changes (e.g., a tapered diametric cross-sectional area), can be bounded on one side by the first porous medium, and bounded on the other side by the second porous medium.
In some embodiments, a biological fluid filter device is provided having first and second fluid flow paths, with a first porous medium across the first fluid flow path, and a second porous medium across the second fluid flow path, and essentially lacking a solid partition between the first and second media. The device can also include at least one element such as a screen or spacer that is capable of allowing biological fluid flow therethrough, interposed between the first and second porous media. For example, the device can include a first screen upstream of the first porous medium, and a second screen upstream of the second porous medium, and the device can also include a space between the first and second porous media, wherein the space is bounded on one side by the first screen, and bounded on the other side by the second screen. In a more preferred embodiment, the first and second porous media each comprise a leukocyte depletion medium.
In another embodiment of the invention, a biological fluid filter device is provided comprising a housing having an inlet and an outlet and defining at least one fluid flow path flow path between the inlet and the outlet, and having a porous medium interposed between the inlet and the outlet and across the fluid flow path, wherein the housing includes at least one semicircular fluid flow channel that directs fluid from one end to the housing to the substantially opposite end of the housing before contacting the porous medium and/or directs the fluid passing through the porous medium to the outlet of the device. In one embodiment, the device includes a semicircular fluid flow channel that directs fluid from one end to the housing to the substantially opposite end of the housing before contacting the porous medium and includes another semicircular fluid flow channel that directs the fluid passing through the porous medium to the outlet of the device.
The present invention also provides a method of filtering a biological fluid such as blood or a blood component comprising passing at least one unit of biological fluid through a filter device having first and second fluid flow paths, and a first porous medium across the first fluid flow path, and a second porous medium across the second fluid flow path, and a space between the first and second porous media, wherein the device essentially lacks a solid partition between the media. The method includes passing a portion of the biological fluid along a first fluid flow path through the first porous medium and through the outlet, and, without substantially utilizing a solid partition to separate one portion from another, passing another portion of the biological fluid along a second fluid flow path through the second porous medium and through the outlet. The method can include passing biological fluid through at least one element upstream of the first porous medium and the second porous medium. For example, embodiments of the method include passing a portion of the biological fluid along a first fluid flow path through the first screen and the first porous medium and through the outlet, and passing another portion of the biological fluid along a second fluid flow path through the second screen and the second porous medium and through the outlet.
In some embodiments, the method provides for filtering more than one unit of biological fluid through the same device to remove leukocytes from the multiple units of fluid.
In preferred embodiments according to the invention, the filter device directs unfiltered biological fluid to contact the first and second porous media at the bottom of the housing, and the housing fills from the bottom. The rising front of biological fluid displaces air from the device while minimizing or eliminating the presence of trapped air.
Typically, the device is utilized without prewetting or priming the porous media with a non-biological fluid such as saline or an additive solution.
REFERENCES:
patent: 4009714 (1977-03-01), Hammer
patent: 4009715 (1977-03-01), Forberg et al.
patent: 4021353 (1977-05-01), Raines et al.
patent: 4056476 (1977-11-01), Mouwen et al.
patent: 4267053 (1981-05-01), Hashino et al.
p
Bormann Thomas J.
DelGiacco Gerard R.
Franovic Mladen
Matkovich Vlado I.
Kim John
Leydig , Voit & Mayer, Ltd.
Pall Corporation
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