Abstract:
A blood collection system has a container for holding blood, and a filter communicating with the container, which are mutually arranged for handling as a unit. The filter contains a fibrous filter medium housed within two flexible sheets of plastic. A first seal joins the sheets directly to the filter medium inboard of the peripheral edge of the filter medium, and a second seal joins the sheets outboard of the peripheral edge of the filter medium. A region of the filter medium extends between the first and second seals to cushion contact with the filter housing during handling.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention generally relates to blood collection and processing systems and methods.  
         BACKGROUND OF THE INVENTION  
         [0002]    Systems composed of multiple, interconnected plastic bags have met widespread use and acceptance in the collection, processing and storage of blood components. Using these systems, whole blood is collected and separated into its clinical components (typically red blood cells, platelets, and plasma). The components are individually stored and used to treat a multiplicity of specific conditions and diseased states.  
           [0003]    Before storing blood components for later transfusion, it is believed to be desirable to minimize the presence of impurities or other materials that may cause undesired side effects in the recipient. For example, because of possible febrile reactions, it is generally considered desirable to remove substantially all the leukocytes from blood components before storage, or at least before transfusion.  
           [0004]    Filtration is conventionally used to accomplish leuko-reduction. Systems and methods for reducing the number of leukocytes by filtration in multiple blood bag configurations are described, e.g., in Stewart U.S. Pat. No. 4,997,577, Stewart et al. U.S. Pat. No. 5,128,048, Johnson et al. U.S. Pat. No. 5,180,504, and Bellotti et. al. U.S. Pat. No. 5,527,472.  
         SUMMARY OF THE INVENTION  
         [0005]    The invention provides a blood collection system comprising a container for holding blood, and a filter communicating with the container. The container and filter are mutually arranged for handling as a unit. The filter contains a fibrous filter medium housed within two flexible sheets of plastic. A first seal joins the sheets directly to the filter medium inboard of the peripheral edge of the filter medium, and a second seal joins the sheets outboard of the peripheral edge of the filter medium. A region of the filter medium extends between the first and second seals to cushion contact with the filter housing during handling.  
           [0006]    Other features and advantages of the invention will become apparent upon review of the following description, drawings, and appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a schematic view of a blood collection and storage system that includes an integral flexible filter that removes leukocytes from red blood cells;  
         [0008]    [0008]FIG. 2 is top view of the integral flexible filter that forms a part of the system shown in FIG. 1;  
         [0009]    [0009]FIG. 3 is a side section view of the filter shown in FIG. 2, taken generally along line  3 - 3  in FIG. 2. an assembled perspective view of the integral flexible filter shown in FIG. 2; and  
         [0010]    [0010]FIG. 4 is an exploded perspective view of the filter shown in FIG. 2, showing the assembly of a molded port to the filter. 
     
    
       [0011]    The invention is not limited to the details of the construction and the arrangements of parts set forth in the following description or shown in the drawings. The invention can be practiced in other embodiments and in various other ways. The terminology and phrases are used for description and should not be regarded as limiting.  
       DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    [0012]FIG. 1 shows a manual blood collection and storage system  10  having an integral flexible filter  20 , which are arranged for handling as a unit. The system  10  provides red blood cells for long term storage that are substantially free of leukocytes. The system  10  also provides platelet concentrate and the platelet-poor plasma for long term storage. The blood collection and storage assembly  10 , once sterilized, constitutes a sterile, “closed” system, as judged by the applicable standards in the United States. The system  10  is a disposable, single use item.  
         [0013]    As shown in FIG. 1, the system  10  includes a primary bag  12  and three transfer bags or containers  14 ,  16 , and  18 . Like the flexible filter  20 , the transfer bags  14 ,  16 , and  18  are integrally attached to the system  10 .  
         [0014]    In use, the system  10  is handled in conventional ways. The primary bag  12  (which is also called a donor bag) receives whole blood from a donor through integrally attached donor tube  22  that carries an phlebotomy needle  24 . A suitable anticoagulant A is contained in the primary bag  12 . The system  10 , with attached filter  20 , is placed into a bucket of a centrifuge (not shown). The entire system  10 , with attached filter, is spun within the centrifuge bucket. Whole blood is centrifugally separated inside the primary bag  12  into red blood cells and platelet-rich plasma. Leukocytes dwell in the interface between the red blood cells and platelet-rich plasma.  
         [0015]    The transfer bag  14  is intended to receive platelet-rich plasma separated from the whole blood collected in the primary bag  12 . Attempts are made when transferring the platelet-rich plasma out of the primary bag  12  to keep as many leukocytes in the primary bag  12  as possible. The transfer of platelet-rich plasma into the transfer bag  14  leaves the red blood cells and the leukocytes behind in the primary bag  12 .  
         [0016]    The transfer bag  16  contains a suitable storage solution S for red blood cells. One such solution is disclosed in Grode et al U.S. Pat. No. 4,267,269, which is sold by Baxter Healthcare Corporation under the brand name ADSOL® Solution. The storage solution S is transferred into the primary bag  12  after transfer of the platelet-rich plasma into the transfer bag  14 .  
         [0017]    The platelet-rich plasma is centrifugally separated by conventional means in the transfer bag  14  into platelet concentrate and platelet-poor plasma. The platelet-poor plasma is transferred into the transfer bag  16 , which is now emptied of storage solution S. The transfer bag  16  serves as the storage container for the platelet-poor plasma. The transfer bag  14  serves as its storage container for the platelet concentrate.  
         [0018]    The storage solution S is mixed with the red blood cells and leukocytes remaining in the primary bag  12 . The mixture of storage solution S, red blood cells, and leukocytes is transferred from the primary bag  12  through tubing  26 .  
         [0019]    The tubing  26  carries in-line the integral, flexible filter  20 . The flexible filter  20  includes a filtration medium  28  contained within a housing  30 . The filtration medium is selected to remove leukocytes from red blood cells. The filter  20 , being flexible, facilitates handling and reduces the incidence of damage to other flexible plastic components of the system  10  during centrifugal processing.  
         [0020]    The leukocyte-reduced red blood cells enter the transfer bag  18 . The transfer bag  18  serves as the storage container for the leukocyte-reduced red blood cells.  
         [0021]    The bags and tubing associated with the processing system  10  can all be made from conventional approved medical grade plastic materials, such as polyvinyl chloride plasticized with di-2-ethylhexyl-phthalate (PVC-DEHP). The bags are formed using conventional heat sealing technologies, e.g., radio frequency (RF) heat sealing.  
         [0022]    Alternatively, since the transfer bag  14  is intended to store the platelet concentrate, it can be made of polyolefin material (as disclosed in Gajewski et al U.S. Pat. No. 4,140,162) or a polyvinyl chloride material plasticized with tri-2-ethylhexyl trimellitate (TEHTM). These materials, when compared to DEHP-plasticized polyvinyl chloride materials, have greater gas permeability that is beneficial for platelet storage.  
         [0023]    The flexible filter  20  includes a filter housing  30  comprising first and second sheets  32  and  34  of flexible, medical grade plastic material, such as polyvinyl chloride plasticized with di-2-ethylhexyl-phthalate (PVC-DEHP). Other medical grade plastic materials can be used that are not PVC and/or are DEHP-free.  
         [0024]    The filtration medium  28  is made from a fibrous material, which is sandwiched between the sheets  32  and  34 . The filtration medium  28  can be arranged in a single layer or in a multiple layer stack. The medium  28  can include melt blown or spun bonded synthetic fibers (e.g., nylon or polyester or polyethylene or polypropylene), semi-synthetic fibers, regenerated fibers, or inorganic fibers. In use, the medium  28  removes leukocytes by depth filtration.  
         [0025]    According to the invention (see FIGS. 2 and 3), the filter  20  includes an inboard main seal  36  and an outboard secondary seal  38 . The main seal  36  joins the two sheets  32  and  34  to each other, as well as joins the filtration medium  28  to the two sheets  32  and  34 . The secondary seal  38  is spaced outboard of the peripheral edge  40  of the filtration medium  28  and joins just the two sheets  32  and  34  to each other.  
         [0026]    As a result of this construction, a region  42  of filtration medium  28  extends between the main seal  36  and the secondary seal  38 . The region  42  provides a “soft” periphery or “cushion” about the filter  20 . The cushioned periphery provides enhanced protection against damage to tubing and bags of the system  10  when the bags, tubing and filter are handled as a unit, e.g., when centrifuged in the same centrifuge bucket. The combination of the main seal  36  inboard of the filtration medium  28  and the secondary seal  38  outboard of the filtration medium  28  also prevents edge flow and provides duplicate seal protection against leaks.  
         [0027]    The main seal  36  can be formed by the application of pressure and radio frequency heating to the two sheets  32  and  34  and filtration medium  28 . The secondary seal  38  can likewise be formed by the application of pressure and radio frequency heating to the two sheets  32  and  34 . The main seal  36  and secondary seal  38  can be formed in sequential heat sealing processes, or simultaneously in a single heat sealing process.  
         [0028]    The filter  20  also includes inlet and outlet ports  44  and  46 . As FIG. 4 shows, the ports  44  and  46  comprise separately molded parts that are heat sealed by radio frequency energy over a hole  48  formed in the sheets  32  and  34 , preferably before the main seal  36  and secondary seal  38  are created.  
         [0029]    A flexible filter  20 ′ (shown in phantom lines in FIG. 1) can be also be integrated into a multiple blood bag system in-line between the primary bag  12  and the transfer bag  14 . In this arrangement, the filtration medium  28  is selected to remove leukocytes from platelet-poor plasma prior to entering the transfer bag  14 .  
         [0030]    Various features of the invention are set forth in the following claims.