Abstract:
A pneumatic pump manifold disposable system, configured as a cassette, is used for the purpose of red cell and plasma apheresis. The cassette integrates a separation device, manifold system, macro-aggregate filter, and five pumping chambers for the purpose of separating plasma and red cells from the whole blood. The cassette system, with the separation device directly attached without tubing, simplifies the loading of the disposable set into the hardware, and reduces the manufacturing complexity of the set. The system allows for plasma, plasma and red cells, or just red cells to be stored in long term storage containers after a procedure.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to an apparatus for the separation of liquid suspensions, especially suspensions of cellular material such as blood and blood components. More particularly, the invention relates to a novel integral flow control cassette and separation device for the separation or fractionation of one or more constituents of blood. 
     Broadly speaking, whole blood is a suspension of red blood cells, white blood cells and platelets in liquid plasma. Separation of one or more of the constituents or components of blood from whole blood or from a suspension comprising fewer than all of the usual blood components is referred to as “apheresis.” Often, apheresis is carried out at the time of blood collection from a donor—and the collected component is stored for later administration to a patient in need of that blood constituent. Alternatively, apheresis may be used as a therapeutic procedure, wherein the blood component is being withdrawn or depleted as part of the treatment of a patient. 
     Machines have long been available for automatically processing the blood of donors or patients by withdrawing the desired constituent and returning to the donor or patient the remaining blood components. For example, platelets may be collected from healthy donors and red cells and plasma returned to the donor. Similarly, concentrated red cells may be collected for later transfusion, and platelets and/or plasma returned to the donor. Other procedures may be used for collecting other components, such as plasma or white cells. 
     Machines for separating blood components, i.e. for performing apheresis, have been based on different operating principles. Centrifugation is one widely-recognized technique, which takes advantage of the slight differences in the density of blood constituents to separate them in a centrifugal field. Commercial apheresis centrifuges include the CS-3000® and Amicus® separators sold by Baxter Healthcare Corporation of Deerfield, Ill., and the Spectra® and Trima® separators by Cobe Laboratories of Golden, Colo. Other manufacturers of commercial blood separators include Fresenius AG, Germany, and Haemonetics Corporation of Braintree, Mass. 
     Separation of blood components by use of a filter membrane has also been used. One remarkable advance in blood separation technology using membrane filtration has employed a spinning rotor. More particularly, this technique employs the relative rotation between two concentric members and the generation of Taylor vortices in the gap between the relatively rotating members. In a commercial separator employing the principle, marketed as the Autopheresis C® separator by Baxter Healthcare Corporation, the separator includes a membrane-covered spinner, having an interior collection system, disposed within a stationary shell. Anticoagulated blood is fed through a radial gap between the spinner and the shell. Taylor vortices are created in the gap by the spinning roter, and provide an interior sweeping motion which tends to clear the membrane of cellular matter that would otherwise deposit on the membrane and clog the pores. As a result of the membrane cleaning, plasma filtrate can be rapidly extracted through the membrane. U.S. Pat. No. 5,194,145, incorporated by reference herein, more specifically describes the construction and operation of this device. 
     While both the centrifugation and spinning rotor techniques have worked exceptionally well, the equipment employing the techniques is relatively complicated and operators are required to undergo extensive training. For convenience, health, and safety reasons, blood separation or apheresis machines utilize disposable tubing sets and separation chambers for the separation and collection of the various blood components. The disposable tubing set and separation chamber are mounted on a reusable device which controls flow through the tubing set in accordance with an operator-selected procedure or other operator instruction. 
     The reusable separation device includes pumps, clamps, sensors and monitors to control flow of blood, blood components and other fluids, such as anticoagulant and saline, through the tubing set and associated separation chamber. Accordingly, it is very important that the tubing set be properly mounted on the hardware to assure proper and safe operation. Due to the large number of guides, pumps, clamps, monitors and sensors onto which the tubing must be carefully mounted, set up of these apheresis devices is often time consuming, tedious, and subject to the possibility of human error. The set-up may be further complicated when the tubing set-up or installation procedure varies with the blood component to be collected. As in any task requiring operator involvement, there is a risk, even if very small, of mis-installation of the tubing set. Although such mis-installation does not typically endanger the donor or patient because of built-in safeguards, it may require time consuming and costly replacement of the tubing set or delay while the operator trouble-shoots and corrects the mis-installation. 
     Of course, complex tubing sets have the added drawback of being expensive to manufacture because of the intensive amount of labor involved, and the increased vigilance required to assure proper assembly. 
     Steps have been taken to design apheresis tubing sets that are easier and less time consuming to install, and less subject to error. One example of such a system is the Baxter Amicus® separation system. The Amicus system employs cassettes that are mounted on pump and valving stations on the reusable device, eliminating much of the manual installation of the tubing set. The cassettes have pre-formed passageways that are controlled by the valving stations in accordance with the procedure pre-selected by the operator. An example of this cassette arrangement is disclosed in U.S. Pat. No. 5,462,416, which is incorporated by reference herein. 
     Although the Amicus system eliminates a significant portion of the tubing set-up steps in the older apheresis devices, it continues to require some mounting steps, as well as assembly of the disposable separation chamber with a reusable centrifuge bowl or chamber in the device. Thus, there continues to be room for more improvement. 
     In addition to the desire to simplify the tubing set installation procedure, there is a continuing desire to reduce the size and weight of the separation devices. The CS-3000® and Amicus® centrifuges, for example, are relatively large roll-about machines. Although the Amicus® is significantly lighter and easier to move than the CS-3000®, there are many situations where a transportable, such as a small suitcase size, apheresis device would be advantageous. A readily transportable device could have particular application, for example, to blood collection drives which are conducted off-site, at a location away from the main blood bank or hospital laboratory, or to treatment of ill patients who cannot be readily moved and are located where it is not possible to bring a larger apheresis device. Whether the apheresis device is of the conventional size or the transportable type, there remains a need to reduce the possibility for error during the tubing connection process, to reduce or simplify operator training for loading and operation of the equipment, and to reduce manufacturing complexity and cost. 
     SUMMARY OF THE INVENTION 
     The present invention is generally embodied in a disposable module adapted for cooperative mounting on a reusable device or module for processing a suspension comprising blood or blood components, and in the system including the disposable module and reusable device. In accordance with the present invention, the disposable module includes an integral flow control cassette and separator. The separator includes a rotor rotatably mounted therewithin, and may be based on a centrifugation, membrane separation or such other rotor-based technique or principle as is desired. The flow control cassette includes an inlet for communicating with a suspension source, and the cassette defines a first flow path communicating between the suspension inlet and an inlet in the separator. A separator outlet is provided for removing a separated portion of the suspension, and the cassette defines a second flow path communicating with the separator outlet. 
     More specifically, the flow control cassette defines a plurality of flow path segments and a plurality of valve stations interconnecting two or more flow path segments to selectively open or close communication between the segments. The valve stations, which in their broader aspects are operable pneumatically, hydraulically, mechanically or otherwise, are cooperative with the reusable module to control fluid flow through the flow path segments and to define the first and second flow paths. An array of flow path segments and valve stations defined within the cassette may, by operation of the reusable hardware, be selectively connected to provided a variety of different fluid flow configurations, depending on the apheresis process requested. 
     To move fluid through the disposable flow control cassette may also include pre-formed pump stations, also operable pneumatically, hydraulically, mechanically or otherwise, to pump fluid through the flow path defined by flow path segments and valve stations, as configured by the reusable device in response to a control program for a procedure selected by the user. This arrangement eliminates the routing of tubing through or around pump heads, as required on many prior devices. The integral flow control cassette and separator of the present invention provide a particularly compact arrangement. When the separator is based on the spinning rotor membrane separation principle, the entire disposable module and reusable module can be reduced to the size of a small suitcase, which is readily transportable for off-site collection or depletion procedures. 
     In a more preferred form, the present invention is embodied in a disposable blood separation set, alone and in combination a reusable actuator device having a plurality of pressure actuators responsive to a control program, in which the separation set includes a cassette including pre-formed pressure actuated pump stations, preformed fluid flow path segments and preformed pressure-actuated valve stations. The cassette also includes an integral fluid separation device communicating with fluid path segments and a plurality of cassette ports communicable with the path segments to convey the flow of fluids to and from the cassette and separation device via flow paths created by the pressure actuators selectively changing pressure to the valve and pump stations in response to a control program. The pressure change to actuate the pump or valve stations may be an increase in pressure such as at or above atmospheric pressure (i.e., a positive pressure), or a decrease in pressure such as to at or below atmospheric pressure (i.e., a negative pressure). 
     The reusable actuator device or module may be programmable for a plurality of different user-selected separation processes, for example collection of plasma or red cell concentrate or other, and the disposable set can preferably accommodate two or more different blood processing procedures. The cassette in the more preferred form lends itself to different procedures due to the plurality of flow path segments interconnected at valve stations so that selective operation of the valve stations by the actuators establishes the different flow paths needed for different procedures. 
     More specifically, the cassette may include a rigid plastic base and a flexible membrane covering at least one side of the base. The rigid plastic base includes upstanding walls on one side of the cassette defining valve and pump wells. When the cassette is mounted into the actuator device, the flexible membrane is pressed against the edges of the walls to seal each well to define a closed valve or pump station. Actuators in the reusable device or module control the valving and pumping action by changing the increasing or decreasing pressure applied to the outside surface of the membrane overlying the valves and pump chambers. For example, by increasing pressure against the membrane, it may be pressed against a valve port in the valve well to block flow. Similarly, repeated flexing of the membrane into and out of the pump chamber in response to pressure changes by the actuator may be used to pump fluid through the cassette in sequential draw and pump cycles. 
     Upstanding walls on the other side of the cassette base define a plurality of flow path segments that extend between valves, pumps and/or separator. These walls may be sealed by a rigid plastic cover or by a flexible membrane as with the one side of the cassette. Thus, fluid flow paths may defined in the cassette for different separation procedures in response to the selected control program in the actuator device by selective pressure changes applied to the flexible membrane at the valve stations, and fluid pumped through the cassette as required for the selected procedure. Accordingly, the same cassette may be used for a variety of different procedures with minimum operator setup required and with greatly reduced opportunity for operator error. 
     These and other features and aspects of the present invention are set forth below in the detailed description of the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a system that embodies features of the present invention, with the disposable module or processing set shown out of association with the reusable module or actuator device (also called a processing device) prior to use. 
     FIG. 2 is a perspective view of the system shown in FIG. 1, with the door of the reusable module to the pump and valve actuators shown open to accommodate mounting of the disposable module with integral cassette and separator. 
     FIG. 3 is a perspective view of the system shown in FIG. 1, with the disposable module or processing set fully mounted on the reusable module or processing device and ready for use. 
     FIG. 4 is a perspective front view of the case that houses the reusable processing device or module shown in FIG. 1, with the lid closed for transporting the device. 
     FIG. 5 is a schematic view of a blood processing circuit provided by the disposable module which, in combination with the reusable module of the present invention, can be programmed to perform a variety of different blood processing procedures. 
     FIG. 6 is an exploded perspective view of an integral cassette (with integral separator) of the present invention, which contains the blood processing circuit shown in FIG. 5, and the pump and valve stations on the reusable processing device shown in FIG.  1 . 
     FIG. 7 is a plan view of the front side of the integral cassette and separator shown in FIG.  6 . 
     FIGS. 8A-8C are perspective views of the connection of the separator and the cassette. 
     FIG. 9 is a perspective view, partially broken away to show detail, of one type of separator embodiment, but not the only one, that may be employed in accordance with the invention. 
     FIG. 10 is a perspective view of the back side of the cassette and separator shown in FIG. 6 illustrating pre-formed fluid flow paths, valve stations and pumping chambers. 
     FIG. 11 is a plan view of the back side of the cassette and separator shown in FIG.  10 . 
     FIGS. 12A-12C are side views, taken along lines  12 A- 12 -A,  12 B— 12 B and  12 C— 12 C respectively of FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a transportable version of the present invention suitable for carrying to the patient or to an off-site blood collection location. As pointed out earlier, although the present invention is particularly well suited to transportable applications, it is not limited to such applications, and may be employed with significant benefit in larger, less portable systems. 
     More specifically, FIG. 1 shows an overall blood or blood component processing system  10 , which includes a disposable plastic tubing set or fluid circuit module  12  and a reusable controller or device module  14 . As will be apparent from the following description, the two modules cooperate to carry out a variety of selected blood processing or collection procedures. 
     The disposable tubing set or module  12  includes an integral fluid flow cassette and separator, generally at  16 , and a plurality of plastic containers, generally at  18 , pre-connected by flexible plastic tubing to the cassette. As will be described in more detail later, the pre-connected containers may be pre-filled with anticoagulant or saline solutions for use in the collection procedure or may be empty for receiving or storing blood components during or after the separation procedure. 
     Fluid flow through the tubing set is controlled by the integral cassette and separator in cooperation with the reusable controller or actuator module  14 . The controller  14  may be of any desired configuration, and it is shown in a small suitcase style configuration for ease of transporting. 
     While the fluid circuit module  12  is intended, for safety and convenience, to be disposable after a single use, the controller  14  is intended to be a durable reusable module suitable for long-term use. In the illustrated and preferred embodiment, the controller  14  is mounted inside a portable housing or case  20 . The case  20  can be formed into any desired configuration, e.g. by molding, and is preferably made from lightweight, yet durable, plastic material. The case presents a compact footprint, suited for set up and operation upon a table top or other relatively small surface. 
     The case  20  includes a base  22  and a hinged lid  24 , which opens for using (as FIG. 1 shows) and closes for transporting or storing (as FIG. 4 shows). The lid  24  includes a latch  26 , for releasably locking the lid  24  closed and a carrying handle  28 . In use, the base  22  is intended to rest in a generally horizontal support surface such as a small table or desk. 
     As noted above, the disposable module  12 , including the integral cassette/separator  16 , is intended to be sterilized, for one-time use only then discarded. FIG. 1 shows the disposable module  12  prior to installation or assembly onto the reusable module or controller  14 . The controller  14  is mounted within the case  20 , and may include suspension hooks for liquid filled bags, scales for measuring fluid volumes dispensed or collected, as well as a valve and pump control station to control fluid flow through the cassette and a drive member for the separator device. As shown more specifically in FIG. 2, the case  20  may include a control panel area  30 , for operator input and for data display, an actuator area  32  for cooperation with the integral cassette and separator, a recessed bag hanging area  34 , an inclined bag rest surface  36 , and a scaled hanger  38  for determining volumes dispensed or collected. 
     The control panel area  30  preferably includes both input and display capabilities. The input capabilities may be in the form of a keypad, touch screen or other suitable input device to allow the operator to input the desired processing information, such as the apheresis procedure to the carried out, patient identification and relevant patient data, desired run time or collection characteristics, or other such information. 
     The device  14  may be controlled by a programmable microprocessor and include pre-programmed instructions for carrying out several different apheresis procedures, allowing the operator to select from a menu the particular procedure desired or the particular blood component to be collected. The microprocessor may also include data storage capability for storing donor/patient information, processing or collection information and other data for later downloading or compilation. 
     The control panel area may include an output or display device such as flat screen display, cathode ray tube, light emitting diode, or the like for display of the desired processing information. The output and input capabilities may also be combined in a single feature such as touch panel screen that displays information while simultaneously allowing user input or selection. Data output capability may also include standard parallel or serial ports or other network or ethernet connection capability, as desired, for communication with other computers or networks. 
     For supporting containers in a hanging position the lid of the case includes the recessed area  34 . Hooks (not shown) on the inside of lid  24  provide support for hanging bags of saline, anticoagulant or the like. Similarly, a retractable hanger  38  is provided for supporting a collection bag in which a blood component is at least temporarily stored. Hanger  38  is preferably mounted on a scale located within the lid to allow automated measurement of the amount of blood component collected. 
     Inclined bag support surface  36  provides additional areas within the case for supporting containers associated with the disposable tubing set or circuit  12 . One or more areas of the inclined surface may be heated, if desired, to warm the solution of the bag prior to circulation within the donor or patient. 
     Taken together, the above features of the controller or reusable module provides a uniquely compact, simple and efficient arrangement for locating and arranging the various components of the disposable module or fluid circuit with reduced opportunity for operator error. 
     As FIG. 2 shows, before beginning a given blood processing and collection procedure, the operator loads the various components of the tubing set into the case  20 . The controller  14  implements the procedure based upon preset software protocols, taking into account other input from the operator. Upon completing the procedure, the operator removes the disposable module. The portion of the module holding the collected blood component or components is removed from the case  20  and retained for storage, transfusion, or further processing. The remainder of the disposable module, after removal from the case  20 , is safely discarded. 
     The set  12 , in combination with the device  14 , defines a programmable blood processing circuit that permits various flow configurations. FIG. 5 schematically shows one representative configuration. Referring to FIG. 5, the system can be programmed to perform a variety of different blood processing procedures, in which, e.g., red blood cells are collected, or plasma is collected, or both plasma and red blood cells are collected, or the buffy coat is collected, or other blood component. 
     The fluid flow circuit  42  shown in FIG. 5, and defined in the fluid flow cassette, includes several pump stations PP(N), which are interconnected by a pattern of fluid flow path segments through an array of in-line valves V(N). These components provide the capability of pumping at least three fluids simultaneously through the use of three separate pumping systems. The cassette is coupled to the remainder of the disposable tubing set by a plurality of ports P(N). 
     The circuit  36  defined in the cassette includes a programmable network of flow paths, comprising eight ports P 1 , P 2  and P 5  to P 10  and four pump stations PP 1  to PP 4 . By selective operation of the line valves V 1  to V 5 , V 8  to V 15  and V 17  to V 25 , any port can be placed in flow communication with any pump station. By selective operation of the valves, fluid flow can be directed through any pump station in a forward or reverse direction between two valves, or an in-out direction through a single valve. 
     In the illustrated embodiment, the circuit also includes an isolated flow path comprising two ports P 3  and P 4  and one pump station PP 5 . The flow path is termed “isolated,” because it cannot be placed (via operation of any valve) into direct flow communication with any other flow path in the fluid flow circuit  42 . The pump station PP 5  in the isolated flow path is used as a dedicated anticoagulant pump, to draw anticoagulant from a source through port P 3  and to meter anticoagulant through P 4  into the blood drawn from the patent or donor. 
     The pneumatic pumping chambers on the cassette are used to move whole blood, blood components, anticoagulant, saline or other solutions, through the fluid circuit and separation device, into storage bags or containers, and possibly back to the donor. The device  14  can be programmed to control flow through circuit  42  by assigning dedicated pumping functions to the various pump stations. For example, in one embodiment, the pump stations PP 1  and PP 2  may serve as general purpose donor interface pumps, regardless of the particular blood procedure performed, to either draw blood from the donor through port P 6 , for example, or return blood to the donor through, for example, port P 5 . Also, these pumps may be actuated exactly out of phase so as to keep the flow of blood smooth. In particular, when one pump draws blood from the donor, the other pump pumps blood to the separator  44  for processing, and then the one pump directs blood to the separator while the other pump withdraws blood from the donor. 
     Similarly, processed plasma exiting the separator  44  may be acted upon by pump stations PP 3  and PP 4 . Again, these pumps may be actuated exactly out of phase in order to provide a continuous plasma flow. In particular, one pump may draw the plasma from the separator  44  as the other pump pumps plasma to either a sample depository through port P 9  or to a plasma collection bag through port P 10 . For a membrane separation device, these pump stations (PP 3  and PP 4 ) may also serve to provide the desired transmembrane pressure (TMP) across the membrane of separator  44  to facilitate processing. For a centrifugal separator, these pumps may assist in maintaining an interface between blood components at a selected position in the centrifuge for the most efficient separation and collection. 
     In a preferred embodiment, a red blood cell filter (FIG. 5) may include in the cassette to remove the red blood cells after separation of whole blood occurs in the separator  44 . The red blood cells can then be either pumped to a temporary or final red cell container through port P 8  or port P 7 . Port P 2  provides the necessary means for supplying red cell preservative (such as Baxter Healthcare&#39;s Adsol® solution) to any collected red blood cells. Once a predetermined red blood cell count has been reached, as measured, for example by a detector associated with the cassette and controller, the draw process may be stopped and the return to donor process started. During any process, port P 1  is available to provide for a means to supply a saline solution through the set and/or as a means to remove waste fluids from the set. 
     The preferred embodiment includes the ten ports (P 1  to P 10  of FIG. 5) that connect to flexible tubing of the disposable module  12 . As illustrated within FIGS. 1-3, a container  46  holding saline for priming and the like is coupled by plastic tubing to the cassette port P 1 . A container  48  suitable for holding a red blood cell additive solution is coupled via tubing to the cassette port P 2 . The tubes connecting these two containers ( 42 , 44 ) may also carry external, manually operated line clamps  48  or internal frangible flow-control connectors, as desired. 
     A container  50  containing anticoagulant is coupled via tubing to cassette port P 3 , and also carries a line clamp  48 . Port P 4  of the anticoagulant circuit is connected to the donor withdrawal and return line  52  which terminates in a needle  54 . In the preferred embodiment, the donor tubing line  52  joins, via Y connector  56 , with donor return line that communicates with port P 5  and the donor draw line that is connected to port P 6 . 
     The remaining ports are typically used for the collection of processed fluids. A plasma collection container  58  may be coupled by a tube to the cassette port P 10 , while the plasma sample port P 9  is available for the sampling of processed plasma through a rubber septum (Interlink® connector, or similar) using a syringe, Vacutainer® device or the like. A red blood cell collection container  60  is coupled by a tube to the cassette port P 7 . A whole blood reservoir  62  may be coupled by a tube to the cassette port P 8 , to serve as a temporary reservoir for whole blood during processing, but may also serve to receive a second unit of red blood cells for storage. 
     Thus, the circuit  42  can be programmed, depending upon the objectives of the particular blood processing procedure, to retain all or some of the plasma, the red cells, the buffy coat or the platelets, or to return all or some of those components to the donor. 
     In a preferred embodiment, the programmable fluid circuit  42  is embodied in the integral cassette and separator  16 . FIG. 6 illustrates the mounting of the cassette and separator onto the reusable module or controller  14 . The cassette  16  has a base  62  made of a rigid injection molded material (such as acrylic, HD polyethylene, polypropylene, or the like). The cassette is covered on one side by flexible plastic sheeting  64  (such as PVC or the like). The cassette contains preformed flow channel segments, valve and pump stations and porting arrangements to direct the flow of whole blood, saline, anticoagulant, plasma, red cells, and preservative solutions to the correct destinations at the correct time. As a result, the cassette  16  provides a centralized, programmable, integrated platform for all the pumping and valving functions required for a given blood processing procedure. In the illustrated embodiment, the fluid pressure comprises positive and negative pneumatic pressure, although other types of fluid pressure can be used, as well as mechanical actuators if so desired. 
     As seen in FIG. 6, when loaded, the cassette  16  lies against the actuator area  32  of the reusable module. The actuator area includes an array  66  of valve and pump actuators for controlling the valve and pump stations on the cassette and a separator-receiving area  68  for receiving the separator into operative position on the reusable module. The pump and valve actuators may apply positive or negative pneumatic pressure upon the flexible membrane  64  to control liquid flow through the circuit. 
     The cassette can take various forms. As illustrated (see FIG. 6) and irrespective of the integral separation device, the cassette  16  comprises the injection molded body or base  62  having a front side  70  and a back side  72 . For purposes of the description, the front side  70  is the side of the cassette  16  that, when the cassette is mounted in the reusable module, faces against the actuator area. The flexible diaphragm sheet or membrane  64  overlies the front side  70  while a rigid backing  74  overlies the back side of the cassette in the preferred embodiment. 
     The cassette body  62  and backing  74  are preferably made of a rigid medical grade plastic material. The diaphragm  64  is preferably made of a flexible sheet of medical grade plastic. The diaphragm  64  is sealed about its periphery to the peripheral edges of the front side of the cassette body  62 . Interior regions of the diaphragm  64  can also be permanently or temporarily sealed to the interior regions of the cassette body  62 , as described in more detail later. 
     The cassette body  62  has an array of interior cavities or channels formed on the front and back sides  70  and  72  (see FIGS. 7,  10  and  11 ). The interior cavities define the valve stations, pump stations and flow paths shown schematically in FIG.  5 . 
     Referring to FIG. 7, the pump stations PP 1  to PP 5  are formed as large concave wells  76  that are open on the front side  70  of the cassette body  62 . Upstanding edges  77  peripherally surround the open wells of the pump stations. The pump wells are closed on the back side  72  of the cassette body  60 , except for a spaced pair of through holes  78 , which serve as inlet or outlets to each pump chamber for each pump station. The through holes  78  extend through the back side  72  of the cassette body  62 . As will become apparent, either through hole can serve its associated pump station as an inlet or an outlet, or both an inlet and outlet. 
     The in-line valves V 1  to V 25  are likewise formed in wells that are open on the front side  70  of the cassette base or body. Each valve well is defined by an upstanding peripheral wall  82  terminates in a raised edge  77  that surrounds the well on the front side of the cassette body. Each valve well also has at least two apertures or through holes  84  and  86  that extend through the cassette body between the front and back sides. The valves are closed on the back side  72  of the cassette body, except for the through holes. As shown in more detail later, one through hole communicates with a selected liquid flow path segment on the back side  72  of the cassette body  62  and the other through hole communicates with another selected liquid flow path segment on the back side of the cassette body. 
     In each valve, a raised peripheral surface  88  circumscribes one of the through holes to define a valve seat. The peripheral surface is, in turn, bordered by a recessed area  90  that also extends to the other through hole. The flexible diaphragm  64  overlying the front side  70  of the cassette body rests against the edge of the upstanding peripheral walls that surround each of the pump valve stations and valves. With the application of positive force uniformly against this side of the cassette body when it is mounted in the reusable module, the flexible diaphragm  64  seats against the upstanding edges  77 , forming a peripheral seal about each of the pump and valve stations. This, in turn, isolates the pumps and valves from each other and the rest of the system. 
     As pointed out earlier, pressure is applied against the flexible membrane to seal the individual pump and valve stations of the cassette when it is loaded into the reusable module and door  92  of the reusable module is closed. More specifically, the valve and pump actuator area  32  of the reusable module includes surfaces arranged to press against the flexible membrane or diaphragm  64  in the areas of the upstanding peripheral walls  82  that surround each of the valve and pump stations. The door  92  of the reusable module captures the cassette and presses it against the valve and pump actuator area to form the peripheral seals around the pump and valve stations. The control program stored in the reusable module may include a series of pre-run checks to assure that the valve and pump stations are properly sealed by the membrane  64  so there will be no leakage between adjacent valve or pump stations. 
     With this arrangement, localized application of positive and negative fluid pressures upon the regions of the diaphragm  64  overlying these peripherally sealed valve and pump stations serve to flex the diaphragm in these regions. These localized applications of positive and negative fluid pressures on the diaphragm overlying the pump stations serve to expel liquid out of the pump stations (with application of positive pressure which pushes the membrane into the pump well) and draw liquid into the pump stations (with application of negative pressure which pulls the membrane from the pump well). similarly, localized applications of positive and negative fluid pressure on the diaphragm regions overlying the valves will serve to seat (with application of positive pressure) and unseat (with application of negative pressure) these diaphragm regions against the valve seats, thereby closing and opening the associated valve port. The flexible diaphragm is responsive to an applied negative pressure or even atmospheric pressure for flexure out of the valve seat to open the respective port. The flexible diaphragm is responsive to an applied positive pressure for flexure into the valve seat to close the respective port. Sealing is accomplished by forcing the flexible diaphragm to flex into the recessed valve well to seal against the valve seat that surrounds one of the through holes. 
     Integral with the cassette body  62  is the separation device or separator  44 . The separator  44  in the preferred embodiment, is mounted to the cassette at a separator mounting section  94 . Referring to FIGS. 8A-8C, the separation device  44  of the preferred embodiment has an outer generally cylindrical housing  96  with support posts  98  a-f that extend into recesses within the mounting section  94  of the cassette. Posts  98  c, e and f are hollow and provide a fluid flow path between the cassette and separator, as well as support for the separator. 
     Although the separator  44  may be based on any suitable separation principle, such as centrifugal or membrane separation, the present invention will now be described through the illustration of FIG. 9 with respect to a spinning membrane separator generally comparable in principle to the Autopheresis C® separator sold by Baxter Healthcare Corporation. In particular, the preferred embodiment incorporates a separator much like the one disclosed within U.S. Pat. No. 5,194,145, incorporated herein by reference. 
     Referring now to FIGS.  9  and  12 A-C, whole blood (which may be combined with an anticoagulant) is introduced into the separator  44  at the inlet  100 . The separator  44  has a generally cylindrical spinner  102  rotatable about a central longitudinal axis within the stationary housing  96 . Magnetic elements  104  attached at one end of the spinner provide for coupling the spinner magnetically to a magnetic driver  106  located within the reusable module. Magnetic drive  106  (not shown in detail) is located at the one end within the reusable module for encompassing and magnetically coupling to the magnetic elements  104  attached to the spinner. The other end of the separator  44  has an port  108  that communicates with the spinner via hollow pivot pin  110 . 
     The surface of the spinner  102  is covered by a filter membrane  112  of a type conventionally used in blood filtration, and having surface apertures in the range of 0.1 to 1.0 microns, preferably in the range of 0.8 to 1.0 microns. Beneath the filter  112 , the spinner surface is configured to define a plurality of circumferential grooves  114  interconnected by longitudinal grooves  116 , which in turn communicate via radial conduits  118  with a central manifold  120 . The manifold  120  is in communication, through an end seal and bearing arrangement (not shown in detail), with the plasma outlet port  108 . 
     As plasma is removed from the blood, the remainder of the blood (high hematocrit blood or red cell concentrate) is removed via a tangential outlet orifice  122  located at the opposite end of the housing from the whole blood inlet  100 . 
     The inlet and outlet ports of the separator communicates via hollow posts  98  c, e and f (best seen in FIGS. 8 a-   8   c ) with flow paths or flow path segments  124  formed on the back side  72  of the cassette base or body  62  (best seen in FIG.  10 ). These flow path segments  124  (see FIGS. 10 and 11) are closed on the front side  70  of the cassette body  62 , except where the channel segments intersect the valve stations through holes or apertures  84 , or the pump stations through holes or ports  78 . The flow path segments  124  are defined by upstanding walls  126  and open outwardly toward the back of the cassette base  62 . The open sides of the flow path segments are closed by a rigid plastic cover  128  sealed over the back side of the cassette base  62  and sealed to the edges of the upstanding walls  126  by sonic or adhesive welding or the like. Alternatively, a flexible membrane could be used in place of the rigid cover, with pressure applied against the membrane to seat it against the upstanding walls in a manner similar to membrane sealing used on the front side of the cassette base. 
     As best seen in FIG. 11, molded ports P 1 -P 10  communicate directly with flow path segments  104  on the back side of the cassette body  62 . These flow path segments may be placed in communication with other flow path segments, pump stations or separator by operation of the valve stations to open or block flow between respective segments. The ports P 1  to P 10  extend out along side edge  130  of the cassette body. As shown in FIGS. 2 and 6, the cassette is vertically mounted in the reusable module and, in this orientation, the ports P 1  to P 10  are vertically arrayed, one above the other. This ordered orientation of the ports provides a centralized, compact unit aligned with the operative regions of the actuator area. 
     A selected physical feature or interfering surface on the cassette may allow the hardware to verify, for example by optical detection, that the correct disposable has been loaded for the specific procedure selected, although with the present invention a single disposable set may be used with different procedures. 
     During operation, measurements of flow rates, collection volumes as well as level monitoring are all accomplished through the hardware and disposable set interface. Flow rates can be measured by at least two means within the system. One simple method is for the control program to count the number of pump strokes, knowing that each stroke pumps a certain volume of fluid. The second means which may be used in combination with the first is based on air flow measurement techniques. The airflow to each pumping chamber can be measured, and hence one can deduce how much fluid is flowing as the fluid flow would be proportional to the volume and pressure of air supplied. 
     Referring back to FIG. 7, transparent or refractive windows  114  and  116 , on the cassette are designed to interface with optical hematocrit and hemolysis detection systems of the hardware, respectively. These windows allow for continuous monitoring of hematocrit and hemolysis levels during any particular procedure, and do not require the operator to input the hematocrit prior to the procedure. Similar windows for monitoring these characteristics such as platelet count or white cell, also could be included in the cassette. 
     While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made therein without departing from the invention in its broader aspects.