Abstract:
A method of processing blood establishes communication between a donor and a blood flow path and pumps whole blood from the donor into a container through the blood flow path. The method centrifugally separates the whole blood in the container into concentrated red blood cells and a plasma constituent. After the method interrupts communication between the donor and the blood flow path, the method pumps the concentrated red blood cells from the container to mix the concentrated red blood cells with a nutritive solution to restore the hematocrit of the concentrated red blood cells to a desired value. The method also removes the plasma constituent.

Description:
RELATED APPLICATIONS 
     This is a divisional of application Ser. No. 09/222,751, Filed Dec. 29, 1998, U.S. Pat. No. 6,071,423 which is a divisional of application Ser. No. 08/943,750 filed Oct. 3, 1997, U.S. Pat. No. 5,849,203, which is a divisional of application Ser. No. 08/593,719 filed Jan. 29, 1996 U.S. Pat. No. 5,693,232 which is a divisional of application Ser. No. 08/199,082 filed Feb. 22, 1994 U.S. Pat. No. 5,494,578 which is a divisional of application Ser. No. 07/748,244 filed Aug. 21, 1991 U.S. Pat. No. 5,322,620 which is a continuation of application Ser. No. 07/514,995 filed May 26, 1989 (now U.S. Pat. No. 5,104,526); which is a continuation of application Ser. No. 07/009,179 filed Jan. 30, 1987 (now U.S. Pat. No. 4,834,890). 
    
    
     TECHNICAL FIELD 
     The invention-pertains to the field of blood component separation and collection. More particularly, the invention pertains to the collection of platelets or plasma from volunteer donors at temporary sites, remote from medical facilities; with portable lightweight equipment capable of easy transport. 
     BACKGROUND OF THE INVENTION 
     The collection of blood from volunteer donors has become a very successful cold very refined activity. The development of single needle, single use, disposable blood collection sets has provided a safe, relatively inexpensive and donor comfortable medium for use in the blood collection process. Such sets have made possible large-scale collection of blood from volunteer donors at sites such as church halls, schools or offices which might be remote from medical facilities. The availability of volunteer donors is important in that such donors tend to be relatively healthy. In addition, they provide a potentially much larger reservoir of donatable blood than is available from the available group of paid donors. 
     In recent years, processing of whole blood from a donor has come to routinely include separating the blood into therapeutic components. These components include red blood cells, platelets and plasma. Various techniques and apparatus have been developed to facilitate the collection of whole blood and the subsequent separation of therapeutic components therefrom. 
     The collection of platelets or plasma from volunteer donors, as opposed to the collection of whole blood, has not been nearly as successful. As a result, much of the plasma now collected comes from paid donors, as opposed to volunteer donors. It would be very desirable to be able to upgrade the collection of plasma so that it becomes a volunteer based activity to a much greater extent than it is currently. 
     Various methods are known for the collection of platelets or plasma. For example, a unit of blood can be drawn from a human donor in a conventional fashion and accumulated in a blood bag or other standard collection container. This unit of blood can then be processed by a centrifuge to separate the plasma from the other components of the blood unit. The separated platelets and plasma can subsequently be removed from the blood bag. Although allowing all blood components to be harvested, this process has the disadvantage that the donor must internally replace the complete unit of blood from which the plasma was extracted. The replacement process can take 6 to 12 weeks during which time the donor cannot again give blood. Further, this process yields only a small portion of available plasma/donor. 
     In a modification of the above system, plasmapheresis can be performed by centrifugation at the time of donation. The non-plasma portion of the blood is then returned to the donor immediately. While this process allows more frequent donation, often as frequently as once per week, the blood is physically separated from the donor for centrifugation. 
     Such physical separation is undesirable because of the cost and complexity of systems and procedures that have been developed to minimize the risk of error when several donors are being processed simultaneously. In addition, physical separation of the blood from the donor could potentially raise concerns in the collection staff of exposure to infectous agents in the collected blood if fluid drips or leaks occur. 
     Separation systems in which the accumulated whole blood is not physically separated from the donor are also known. These can be either batch or continuous systems. 
     One continuous centrifuge based system is disclosed in Judson et al. U.S. Pat. No. 3,655,123 entitled “Continuous Flow Blood Separator.” The system of the Judson et al. patent uses two needles, an outflow needle and an inflow needle. Whole blood is drawn from a donor via the outflow needle. The whole blood fills a buffer bag. Blood from the buffer bag drains, under the force of gravity into a centrifuge. The system of the Judson et al. patent uses the centrifuge to separate blood components. The plasma can be collected in a container. The red blood cells can be returned to the donor via the inflow needle. 
     Various systems are known that utilize annular separation chambers for plasma pheresis. For example, U.S. Pat. No. 4,531,932 to Luppin et al. entitled Centrifugal Plasmapheresis Device discloses a system which incorporates a centrifuge with a rotating annular rotor. A centrally located rotating seal couples stationary fluid flow lines to the rotating rotor. 
     Whole blood is drained from a donor, passed through the rotating seal and subjected to separating rotational forces in the rotating rotor. Separated plasma is drawn off and concentrated whole blood cells are passed back through the rotating seal and returned to the donor. 
     Related types of systems which incorporate rotatable, disposable annular separation chambers coupled via rotary seals to stationary tubing members are disclosed in U.S. Pat. No. 4,387,848; 4,094,461; 4,007,871; and 4,010,894. 
     One consideration in the processing of whole blood is the requirement that the processing take place under sterile conditions. A second consideration is the requirement that processing take place so as to maximize storage life. Unless the processing takes place within a single sealed system, the permitted storage duration and usable lifetime of the blood components is substantially shortened. Components processed within a sealed system can be stored for four to six weeks or longer before use. On the other hand, whole blood or components thereof must be used within 24 hours if the system seal is broken. 
     To promote the desired ends of sterile processing within a single sealed system, a family of dual member centrifuges can be used to effect cell separation. One example of this type of centrifuge is disclosed in U.S. Pat. No. RE 29,738 to Adams entitled “Apparatus for Providing Energy Communication Between a Moving and a Stationary Terminal.” 
     As is now well known, due to the characteristics of such dual member centrifuges, it is possible to rotate a container containing a fluid, such as a unit of donated blood and to withdraw a separated fluid component, such as plasma, into a stationary container, outside of the centrifuge without using rotating seals. Such container systems can be formed as closed, sterile transfer sets. 
     The Adams patent discloses a centrifuge having an outer rotatable member and an inner rotatable member. The inner member is positioned within and rotatably supported by the outer member. 
     The outer member rotates at one rotational velocity, usually called one omega, and the inner rotatable member rotates at twice the rotational velocity of the outer housing or two omega. There is thus a one omega difference in rotational speed of the two members. For purposes of this document, the term “dual member centrifuge” shall refer to centrifuges of the Adams type. 
     The dual member centrifuge of the Adams patent is particularly advantageous in that, as noted above no seals are needed between the container of fluid being rotated and the non-moving component collection containers. The system of the Adams patent, provides a way to process blood into components in a single, sealed, sterile system wherein whole blood from a donor can be infused into the centrifuge while the two members of the centrifuge are being rotated. 
     An alternate to the apparatus of the Adams patent is illustrated in U.S. Pat. No. 4,056,224 to Lolachi entitled “Flow System for Centrifugal Liquid Processing Apparatus.” The system of the Lolachi patent includes a dual member centrifuge of the Adams type. The outer member of the Lolachi centrifuge is rotated by a single electric motor which is coupled to the internal rotatable housing by belts and shafts. 
     U.S. Pat. No. 4,108,353 to Brown entitled “Centrifugal Apparatus With Oppositely Positioned Rotational Support Means” discloses a centrifuge structure of the Adams type which includes two separate electrical motors. One electric motor is coupled by a belt to the outer member and rotates the outer member at a desired nominal rotational velocity. The second motor is carried within the rotating exterior member and rotates the inner member at the desired higher velocity, twice that of the exterior member. 
     U.S. Pat. No. 4,109,855 to Brown et al. entitled “Drive System For Centrifugal Processing Apparatus” discloses yet another drive system. The system of the Brown et al. patent has an outer shaft, affixed to the outer member for rotating the outer member at a selected velocity. An inner shaft, coaxial with the outer shaft, is coupled to the inner member. The inner shaft rotates the inner member at twice the rotational velocity as the outer member. A similar system is disclosed in U.S. Pat. No. 4,109,854 to Brown entitled “Centrifugal Apparatus With Outer Enclosure”. 
     Centrifuges of the type disclosed in the above indentified Brown et al. and Brown patents can be utilized in combination with a sealed fluid flow transfer set of the type disclosed in U.S. Pat. No. 4,379,452 to DeVries. The disclosure of the DeVries patent is incorporated herein by reference. The set of the DeVries patent incorporates a blood collection container that has a somewhat elongated shape similar to those of standard blood collection sets. One embodiment of this combined system is the CS3000 cell separator system marketed by Travenol Laboratories, Inc. 
     The CS3000 incorporates a dual member centrifuge in combination with a sealed set of the type disclosed in DeVries. This is a continuous system that requires the donor to receive two needle punctures. Such systems have been extensively used in blood centers for plasma and platelet pheresis. 
     The CS3000 is a large and expensive unit that is not intended to be portable. Further, the DeVries type transfer sets are quite complex to install and use. They are also an order of magnitude more expensive than a standard, multi-container blood collection set. 
     A further alternate to the Adams structure is illustrated in U.S. Pat. No. 4,530,691 to Brown entitled “Centrifuge With Movable Mandrel.” The specification and figures of this Brown patent are hereby incorporated by reference herein. The centrifuge of this latter Brown patent also is of the Adams-type. However, this latter centrifuge has an exterior member which is hinged for easy opening. When the hinged upper section is pivoted away from the bottom section, it carries the rotatable inner member along with it. 
     The inner member supports a receiving chamber with a spring biased mandrel which continually presses against a sealed, blood containing container positioned within the receiving chamber. The system of this latter Brown patent also discloses the use of two separate electric motors to rotate the inner and outer members. The motors are coupled to a control system. 
     There thus continues to be a need for methods and related apparatus of platelet or plasmapheresis which can readily be used with volunteer donors at various temporary locations. This method and related apparatus should be usable by technicians with a level of skill commensurate with the level of skill now found at volunteer-based blood collection centers. Further, both the method and related apparatus should be readily portable to locations such as churches or schools where blood collection centers are temporarily established. Preferably the apparatus will be essentially self-contained. Preferably, the equipment needed to practice the method will be relatively inexpensive add the blood contacting set will be disposable each time the plasma has been collected from a single donor. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, a method is provided of continuously separating a selected component from a fluid. The method includes providing an elongated flexible separation chamber which has an input port. The separation chamber or member has at least one output port. 
     A first fluid flow conduit, a plastic tubing member for example, is coupled at one end to the input port. A second fluid flow conduit, also a plastic tubing member, is coupled to the output port. 
     A centrifuge is provided which has a hollow cylindrical receiving chamber. The separation member is placed in the receiving chamber adjacent an interior curved peripheral wall thereof. Distal ends of the two tubing members are brought out to a fixed location. 
     The centrifuge, including the receiving chamber is then rotated at predetermined first and second rates. Simultaneously, an input fluid flow is provided at the fixed distal end of the first fluid flow conduit. The input fluid flow partly fills the separation member. The input fluid is separated in the separation member by centrifugal forces. An interface is formed between a portion of the separated fluid component and a portion of the residual fluid. The interface is formed adjacent a selectively oriented surface of the receiving chamber. 
     The location of the interface on the surface is sensed. A portion of the separated component is withdrawn through the output port via the second fluid flow conduit and out the fixed distal end thereof in response to the interface being sensed at a predetermined location. 
     The withdrawing step can include pumping the separated fluid component through the second fluid flow conduit. The separated component can then be accumulated in a component container. 
     In one embodiment of the invention, a blood collection and component separation set is provided. The set includes an elongated flexible separation chamber which is formed with at least one interface region thereon. The interface region is, at least in part, transmissive of radiant energy. The chamber has a whole blood input port, a separated component output port and a residual fluid output port. The separated component can be for example plasma or platelets. 
     First, second and third fluid flow conduits are provided, each of which, for example being a plastic tubular member. Each fluid flow conduit has a proximal end coupled to a respective input or output port of the separation chamber. 
     The first fluid flow conduit is coupled to the whole blood input port. A distal end thereof can in turn be coupled to donor collection means which can include a piercing cannula. The second fluid flow conduit is coupled to the selected component output port. A distal end thereof can be coupled to a collection container. The third fluid flow conduit is coupled to the residual fluid output port. 
     In accordance with this embodiment of the invention, a quantity of whole blood can be withdrawn from a donor and drawn into the separation chamber. The whole blood can be separated into plasma or platelets and packed red blood cells in the separation chamber. The plasma or platelets can be drawn off or pumped into the component collection container. The packed red blood cells can then be collected or returned to the donor. The process can then be repeated a number of times until the desired quantity of plasma or platelets has been collected. 
     This embodiment requires that the donor only receive a single needle puncture. In addition, if the concentrated red blood cells and plasma are to be returned to the donor, the donor is never physically disconnected from the pheresis system until that return process has been completed. 
     In yet another embodiment of the invention, platelets can be separated from the plasma and collected in a second component collection container. In this embodiment, the platelets can be accumulated in the separation chamber while the plasma is being drawn off. Subsequently, after the plasma has been drawn off the platelets can be drawn off and collected. 
     The blood collection set can be formed with a single cannula which is used for both drawing whole blood and returning packed red blood cells to the donor. Alternately, if desired, the set can be configured as a two cannula set with one cannula used for withdrawing whole blood and a second cannula used for returning packed red blood cells to the donor. 
     In yet another embodiment of the invention, the separation chamber can be formed in two parts. The first part can include the whole blood input port and the packed red blood cell output port. This first part is in fluid flow communication with a second part. Platelet rich plasma separated from the whole blood in the first part flows into the second part and is in turn separated from the platelets therein. The plasma can then be drawn off into a collection container or returned to the donor along with the red blood cells. The platelets can continue to accumulate in the second part. Additional quantities of whole blood can be drawn from the donor and passed through the separation chamber. Subsequently, the collected platelet concentrate can be sealed in the second part. 
     The receiving chamber in the dual member centrifuge can be formed with an annular slot. The slot receives and supports the elongated separation chamber. 
     Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings in which the details of the invention are fully and completely disclosed as a part of this specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view, fragmented and partly in section of a system and method of pheresis in accordance with the present invention; 
     FIG. 2 is an enlarged sectional view of the receiving chamber of FIG. 1; 
     FIGS. 3A and 3B illustrate schematically a particular transfer set and method of pheresis in accordance with the present invention; 
     FIG. 4 is a sectional view taken along plane  4 — 4  of FIG. 3B; 
     FIG. 5A is a top plan view of a separation chamber in accordance with the present invention illustrating the pheresis process; 
     FIG. 5B is a perspective view of the separation chamber and pheresis process illustrated in FIG. 5A; 
     FIG. 5C is a perspective view of an alternate embodiment of the separation chamber illustrating the pheresis process therein; 
     FIG. 6 is a graph of varying hematocrit of fluid in a rotating separation chamber as a function of distance along the separation chamber in accordance with the present invention; 
     FIG. 7A is a top plan view of an alternate separation chamber in accordance with the present it invention; 
     FIG. 7B is a perspective view of the alternate separation chamber of FIG. 7A; 
     FIG. 8 is a schematic fluid flow circuit illustrating an alternative fluid flow transfer set and method of practicing the present invention; 
     FIG. 9 is a schematic perspective view of a two part separation chamber; 
     FIG. 10 is a schematic fluid flow circuit illustrating an alternative fluid flow transfer set and method of practicing the present invention; and 
     FIG. 11 is a schematic fluid flow circuit illustrating an alternative fluid flow transfer set and method of practicing the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there is shown in the drawing and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and are not intended to limit the invention to the specific embodiments illustrated. 
     FIG. 1 illustrates a readily transportable system  10  in accordance with the present invention. The system  10  includes a relatively light-weight dual member centrifuge  12  and an associated fluid flow transfer set  14 . 
     The dual member centrifuge  12  is of the Adams type having a stationary support  20  on which is mounted a first motor  22 . The first motor  22  has a rotary output shaft  24  which rotates at a first angular velocity conventionally referred to as one omega. Fixedly attached to the rotary shaft  24  is a yoke  26 . The yoke  26  supports a second electric motor  28 . The electric motor  28  has a rotary output shaft  30 . The shaft  30  rotates at an angular velocity twice that of the shaft  24 , conventionally referred to as two omega. The motor  28  is pivotably attached to the yoke  26  at pivot points  36  and  38 . 
     Affixed to the rotating shaft  30  is a cylindrical receiving chamber  40 . The details of the chamber  40  are illustrated in detail in FIG.  2 . The receiving chamber  40  is rotated by the shaft  30 . The chamber  40  includes a region  40   a  that is transparent to selected, incident radiant energy. The chamber  40  has a cylindrical exterior peripheral region  42 . Spaced apart from the exterior region  42  is a generally cylindrical interior peripheral region  44 . Between the exterior region  42  and the interior region  44  is a selectively shaped annular slot  46 . The slot  46  has a closed end  46   a . The slot  46  slidably receives a separation chamber  50 . The chamber  46  has an exterior diameter on the order of six inches and an internal length on the order of 2.3 inches. The slot  46  has a length on the order of 2.1 inches. The width of the slot  46  is on the order of 0.2 inches. 
     The separation chamber  50  is in fluid flow communication via a flexible multi-channel conduit  52  with the remainder of the set  14 . A proximal end  54  of the flexible fluid flow conduit  52  is coupled to the separation chamber  50 . 
     The fluid flow conduit  52  is supported by a stationary torque arm  56 . The use of such torque arms is well known to those skilled in the use of dual member centrifuges of the Adams type. A distal end  60  of the fluid flow conduit  52  separates into a plurality of discrete flexible conduits  60   a ,  60   b  and  60   c . The distal ends  60   a ,  60   b  and  60   c  are each in fluid flow communication with a respective container as seen in FIGS. 3 a  and  3   b.    
     The conduits  60   a ,  60   b  and  60   c  could be formed of various flexible, medical grade plastics. 
     The system  10  also includes a control system  66  which is coupled to the motors  22  and  28 . Control systems for use with dual member centrifuges of the Adams type are known in the art. One type of suitable control system is a proportional-integral-differential control system. Various of the above noted patents disclose a variety of ways to rotate and control dual member centrifuges. 
     The control system  66  receives feedback from vibration and fluid leak sensors  68  and  70 . The sensors  68  and  70  are fixedly supported by at stationary suspension system  72 . The system  72  can be connected to resilient members  74  to stabilize the centrifuge  12  during operation. 
     A source of radiant energy  76  is affixed to the 2 w motor  28 . The source  76  directs a beam of radiant energy  76   a  toward the radiant energy transmitting region  40   a  of the rotatable chamber  40 . The region  40   a  permits the beam of radiant energy  76   a  to inpinge on an interface region of the separation chamber  50 . A portion  76   b  of the beam  76   a  will pass through the interface region of the separation chamber  50  and emerge to be detected at an interface sensor  80 . 
     The source  76  could be any emitter of radiant energy such as infrared or incandescent light. The sensor  80  could be any compatible energy sensitive detector. The interface sensor  80  can be used to detect the location of the interface between the separated plasma and packed red blood cells in the separation chamber  50  during the centrifugation process. The sensor  80  is also coupled to the control system  66 . 
     FIG. 2 illustrates the shape of the slot  46  in the receiving chamber  40 . The slot  46  has two spaced apart annular surfaces  46   b ,  46   c . This spacing is on the order of 0.2 inches. The slot  46  has a downwardly oriented opening  46   d . The separation chamber  50  is slid into the slot  46  via the opening  46   d . If necessary, the opening  46   d  can be covered by a metal cover to initially retain the separation chamber  50  in position. Once the chamber  40  is rotated and the chamber  50  has been filled with fluid, the rotational forces set up adequate frictional forces such that the separation chamber  50  will be locked in place. 
     The chamber  40  can be molded of polycarbonate, a transparent plastic. The radiant energy beam  76   a  readily passes through this material. The chamber  40  can be selectively painted or masked so as to limit those regions through which the radiant energy  76   a  can pass. 
     FIGS. 3 a  and  3   b  schematically illustrate the details of the fluid transfer set  14  as well as one mode of using same. In FIGS. 3 a  and  3   b  arrows along a conduit or tubing member indicate a direction of fluid flow. 
     The set  14  in addition to the separation chamber  50  and the multi-channel conduit  52  includes a whole blood collection container  86 . Attached to the collection container  86  is a draw conduit  88  which terminates at a free end in a draw cannula  88   a . The draw cannula  88   a  is intended to be inserted into a vein of a donor. The set  14  also includes a plasma collection container  90  and a red blood cell nutritive container  92 . 
     The solution in the container  92  is of a known type which provides nutrients to packed red blood cells subsequent to the plasma pheresis process. Contents of such solutions include dextrose, sodium chloride, mannitol and adenine. One appropriate solution is marketed by Travenol Laboratories, Inc. under the trademark ADSOL. The container  92  is sealed with a frangible member  92   a  which can be broken at an appropriate point in the plasma pheresis process. 
     The set  14  is initially used to collect a unit of blood in the whole blood collection container  86  using standard procedures. Once the unit of whole blood  86  has been collected, the cannula  88   a  is removed from the arm of the donor and the tubing  88  is closed by heat sealing. The set  14  is now a closed sterile system. The separation chamber  50  is positioned in the slot within the rotatable receiving chamber  40 . The separation chamber  50  can then be rotated. 
     A whole blood pump  94  can be utilized to meter whole blood from the container  86  into the chamber  50  for separation into concentrated red blood cells and plasma. The plasma can be withdrawn after separation into the container  90 . A second pump  96  can be used to pump the concentrated red blood cells into the container  92  containing the nutritive solution. The containers  90  and  92  can then be closed by heat sealing and separated from the remainder of the set  14 . 
     While the set and method illustrated in FIGS. 3 a  and  3   b  are primarily suited for processing of whole blood on a batch basis, one of the advantages of the present invention lies in the fact that it should be possible to separate to a great extent the white cells from the plasma. It is known that from time to time the white cells from a donor infused into a recipient cain cause an adverse reaction. Hence, removal of these white cells would be both desirable and beneficial. 
     In a preferred mode, the separation chamber  50  has a volume on the order of 80 to 90 ml. The preferred separation centrifugation speeds are in a range on the order of 3800 to 4200 rpm. 
     FIG. 4, a sectional view taken along plane  4 — 4  of FIG. 3 b , illustrates the overall shape of the chamber  50  prior to the centrifugation process. The chamber  50  can be formed of a single plastic sheet member. That member is folded on itself and sealed in a region  51 . An internal volume  513  results. The fluid being separated flows in this volume. 
     FIG. 5A through 5C schematically illustrate the separation process as the separation chamber  50  is being rotated. As is illustrated in 
     FIGS. 5A-5C the chamber  40  and the separation chamber  50  are rotated-in a direction  100 . Whole blood is infused at the input port  50   a  and flows into the separation chamber  50  in a direction  102 . The whole blood input port  50   a  is positioned centrally with respect to the centrifugal force field F. 
     Under the influence of the centrifugal force field F, the whole blood separates into high density packed red blood cells in an outer annular region  104  adjacent the maximum centrifugal force region  42  of the rotatable chamber  40 . Lower density plasma separates out into an inner annular region  106  adjacent a relatively lower centrifugal force region adjacent the inner region  44 . Between the outer annular region  104  of packed red blood cells and the inner annular region  106  of plasma, a substantially smaller layer  108  of platelets forms. 
     A surface  110  can be provided which is at a predetermined angle with respect to the direction of flow  102 . The surface  110  provides a very sharp and highly transmissive interface between the region of plasma  106  and the region of packed red blood cells  104 . The incident radiant energy  76   a  passes through the surface member  110 , which is essentially transparent thereto, and out the transparent region  40   a  of the chamber  40  as the output radiant energy beam  76   b . When sensed by the interface sensor  80  the precise location of the interface between the plasma in the region  106  and the packed red blood cells in the region  104  can be determined. 
     The output port  50   b  for the platelet rich plasma is located adjacent the low force inner surface  50   d  of the separation chamber  50 . Platelet poor plasma can be withdrawn therefrom under the control of the control system  66  in response to the sensed position of the interface between the red blood cells and the plasma on the surface  110 . 
     The residual fluid output port  50   c  from which the paced red blood cells can be withdrawn is positioned adjacent the relatively high force outer surface of the separation chamber  50  adjacent the outer peripheral surface  40   a.    
     The transparent surface  110  can be formed as part of the separation chamber  50 . Alternatively, the surface  110  can be affixed to the rotatable chamber  40 . In this instance, a region of the chamber  50  can be positioned adjacent thereto. 
     Depending on the location of the annular region  108  of platelets with respect to the surface  110 , the system  10  can operate in several different modes. 
     If the location of the region  108  has moved adjacent an interior end  110   a  of the surface  110 , the platelets will spill through the port  50   b  resulting, in platelet rich plasma as the separated fluid component. 
     If the region  10 B is centrally located as in FIG. 5A, platelets will accumulate in the chamber. Platelet poor plasma will then flow out the port  50   b . In this mode, the plasma continually flows inwardly through the platelet region  108 . This fluidizes the platelets and minimizes sedimenting and aggregating of the platelet concentrate. 
     In a third mode of operation, the platelet region  108  can be positioned adjacent an outer region  110   b.  In this instance, the platelets will be swept out of the chamber, via the port  50   c  with the packed red blood cells. 
     As illustrated in FIG. 5C, a dam  112  can also be provided adjacent the plasma output port  50   b . As is discussed subsequently, the dam  112  is effective to retain a fluid, such as air, in the chamber  50  during start up of the centrifugation process. 
     As was the case with the surface  110 , the dam  112  can be integrally formed with either the separation chamber  50  or can be formed as part of the rotatable chamber  40 . 
     It will be understood that FIG. 5 a  through  5   c  are schematic in nature and are intended to illustrate the separation process. The shape of the separation chamber  50  during the pheresis operation will be determined by the shape of the slot  46 . 
     The graph of FIG. 6 illustrates the expected change of hematocrit as whole blood is infused through the input port  50   a  and travels along the rotating separation chamber  50 . Assuming an input hematocrit on the order of 0.45, the hematocrit of the output packed red blood cells ranges between 0.80 and 1.0. One of the functions of the nutritive mixture provided in the container  92  is to restore the hematocrit of the packed red blood cells to a value such that infusion into a receipient is possible. 
     FIGS. 7A and 7B illustrate schematically an alternate separation chamber  51 . In the separation chamber  51 , whole blood is injected into the chamber at a centrally located input port  51   a . Unlike the separation chamber  50 , an output port  51   c  for the concentrated red blood cells is provided at the same end of the chamber  51  as is the whole blood input port  51   a.  In this embodiment, the red blood cells are withdrawn in the opposite direction as the input flow of the whole blood. The output port  51   c  is located adjacent the high force outer peripheral wall of the separation chamber  51 . Thus, there are two directions of flow of fluid within the chamber  51 . 
     The chamber  51  also includes a supplemental ramp  111  to urge or push the packed cells towards the packed cell removal port  51   c.  This flow is opposite the flow of whole blood  51   a.  The ramp  111  may be integrally formed as part of the separation chamber  51 . Alternately, the ramp  111  can be formed as part of the rotatable member  40 . 
     FIG. 8 illustrates yet another system  120  which incorporates the elongated flexible separation chamber  50 . The system  120  is a centrifugely based pheresis system which can provide as a separated component from whole blood either platelet poor plasma or platelet concentrate. 
     The system  120  includes a fluid flow transfer set  122  which is useable in conjunction with the dual member centrifuge  12 . The transfer set  122  includes the draw conduit  88  with the associated cannula  88   a . In the set  122 , the cannula  88   a  is used for drawing whole blood from a donor and for returning concentrated red blood cells and/or plasma, to the donor during the pheresis operation. The system  120  is intended to be coupled to the donor continuously throughout the entire pheresis operation. 
     The draw/return conduit  88  is coupled at a junction connector  124  to respective tubing lines  126 ,  128  and  130 . The tubing member  126  is coupled via an anticoagulant pump  132  to a container of anticoagulant  134 . The tubing member  128  is coupled via a connector  136  and a feed blood pump  138  to the whole blood input port  50   a  of the separation chamber  50 . 
     The separated component output port  50   b  of the separation chamber  50  is coupled via a tubing member  140  to a plasma pump  141 . A tubing member  142  is coupled alternately either to a separated component container  144  or a tubing member  146 . The member  146  feeds either a reservoir  148  or a bubble trap/bubble detector,  150  in the return conduit line  130 . Clamps  1  through  6  would be manually opened and closed to regulate the desired directions of flow. 
     The residual output port  50   c  is coupled via a tubing member  147  and a junction member  149  to the bubble trap/bubble detector  150 . 
     In operation, the set  122  would be coupled to the donor by means of the cannula  88   a . The chamber  50 , as previously discussed, would be positioned in the receiving chamber of the dual member centrifuge  12 . Clamps  1 ,  4 , and  5  would be opened. Clamps  2 ,  3  and  6  would be closed. 
     Whole blood would be drained from the donor via conduit  128 . Anticoagulant would be simultaneously infused into the whole blood via the conduit  126 . The feed blood pump  138  would draw the blood from the donor at approximately a 70 ml per minute rate. The pump  138  would also supply the drawn blood to the input port  50   a  of the rotating separation chamber  50  at the same rate. 
     The rotating separation chamber  50  would separate the whole blood into platelet poor plasma at the output port  50   b  and red blood cells at the output port  50   c . Red blood cells from the output port  50   c  would be accumulated in the reservoir  148  simultaneously with platelet poor plasma being accumulated in the container  144 . 
     When the volume and weight detector associated with the reservoir  148  indicates that a maximum extracorporeal volume has been accumulated therein, clamps  1 ,  4  and  5  would be closed. Clamps  2 ,  3  and  6  would be opened. 
     The concentrated cells in the reservoir  148  would be pumped, via the feed pump  138 , through the separation chamber  50  a second time. Output from the separation chamber  50  via conduits  140  and  147  would be passed through the bubble trap  150  and, via the conduit  130 , returned through the cannula  88   a  to the donor. When the weight and volume detector indicated that the reservoir  148  was sufficiently empty, the draw process would be reinitiated. 
     Hence, the system  120  would be capable of accumulating platelet poor plasma in the container  144 . In addition, the platelets would be accumulated in the region  108  of the separation chamber  50 . Subsequent to the plasma having been collected, the container  144  can be replaced and the platelets could be drawn off and accumulated in the replacement container. 
     Densities of platelets which could be accumulated and drawn off in this fashion range from 200 billion to 300 billion cells in 100 ml of fluid. Such densities might take 3 to 4 cycles of whole blood drawn from the donor to build up the necessary platelet concentration in the separation chamber  50 . 
     Alternately, the platelet poor plasma could be pumped into the reservoir  142  and returned after the second pass to the donor. The platelet concentrate can then be accumulated in the container  144 . 
     FIG. 9 illustrates yet another separation chamber  160 . The separation chamber  160  has two fluid separating portions  162  and  164 . The fluid separating portion  162  includes a whole blood input port  162   a  centrally located at an input end of the portion  162 . A concentrated red blood cell output port  162   c  is also provided adjacent the input port  162   a . The portion  162  thus includes whole blood flowing into the region and packed red blood cells flowing out of the region. The portion  162  could have a relatively small volume on the order of 20-30 ml. 
     Separated platelet rich plasma can be drawn out of the portion  162  via a conduit  166 . The platelet rich plasma can then be separated in the second portion  164  into platelet poor plasma and platelets. The platelets accumulate in the second portion  164  along the outer, high force, wall  164   a . The second portion  164  includes an output port  162   b . The platelet poor plasma can be returned to the donor. The portion  164  can have a volume on the order of 50-60 ml. 
     FIG. 10 illustrates a system  170  usable for platelet pheresis. The system  170  incorporates a single use disposable fluid transfer set  172 . The set  172  includes the two part separation chamber  160  of FIG.  9 . Other elements of the set  172  which correspond to elements of the previously discussed set  122  have been given identical identification numerals. 
     The two part chamber  160  would be positioned in the receiving chamber of the dual member centrifuge  12 . Clamps  1 ,  4  and  6  would be opened. Clamps  2 ,  3  and  5  would be closed. The set  172  could be mounted on an automated fixture which could automatically operate the clamps  1 - 6 . 
     In operation, the set  172  would be coupled to the donor by means of the cannula  88   a . Whole blood would be drawn from the donor by the cannula  88   a . The whole blood will flow through the conduit  88 , the conduit  128  and, via the feed blood pump  132 , would be pumped into the input port  162   a  of the separation chamber  160  at a 70 ml per minute rate. 
     Concentrated red blood cells from the output port  162   c  would flow into the reservoir  148  via the conduit  147 . Platelet rich plasma, via the tubing member  166 ; will flow into the rotating platelet separation chamber  164 . Output from the platelet separation chamber  164 , via the output port  162   b  will be platelet poor plasma. The platelet poor plasma will be pumped via the plasma pump  141  in the conduit  146  into the reservoir  148 . While the whole blood is passing through the separation chamber portion  162  and the platelet poor plasma is being separated in the platelet chamber  164 , platelets will continue to accumulate in the chamber  164 . 
     When the volume and weight detector associate with the reservoir  148  indicates that a maximum extracorporeal volume of drawn blood has accumulated in the set  172 , the appropriate detector signal will be generated. The operator or fixture will then close clamps  1  and  4 . The operator or fixture will open clamps  2  and  3 . Fluid in the reservoir  148  will be pumped via the feed pump  138  through the separation chamber  160  a second time. This fluid includes plasma and packed red blood cells which had previously accumulated therein thus providing a second opportunity to collect those platelets not collected with the first pass. However, with clamp  4  closed, output fluid on the line  147  and the line  166  will pass through the bubble trap/bubble detector  150  through the line  130  and be returned to the donor via conduit  88  and cannula  88   a.    
     When the reservoir  148  has been sufficiently emptied, the volume weight detector will again generate a indicator signal. The operator or fixture will reclose clamps  2  and  3  and reopen clamps  1  and  4  to reinitiate the draw cycle. Whole blood will again be drawn from the donor at the 70 ml per minute rate. This process may be repeated as many times as desired so as to accumulate the desired quantity of platelets in the chamber  164 . 
     Subsequent to the desired quantity of platelets having been accumulated in chamber  164 , clamps  1 ,  3  find  6  can be closed and clamp  5  can be opened. The platelets must then be resuspended, for example, by shaking the platelet chamber  164 . Platelets can be pumped from the chamber  164  by the pump  141  into the platelet accumulation container  174 . By means of this process, platelets on the order of 4×10 11  cells can be accumulated from a single donor. This represents approximately 90 percent of the platelets which were in the blood drawn from the donor. 
     FIG. 11 illustrates an alternate system  180  which incorporates a disposable fluid flow transfer set  182 . The transfer set  182  includes the draw return cannula  88   a  and associated conduit  86 . Whole blood is drawn through and concentrated cells are returned through a conduit member  184  which is coupled to an input to the bubble trap/bubble detector  150 . Output from the bubble trap/bubble detector  150  via a bidirectional pump  186  flows into a reservoir  188  at an input port  188   b.  A deflector member  188   d  in the container  188  directs and regulates the flow of fluid among the ports  188   a ,  188   b  and  188   c.    
     During the draw cycle, whole blood which flows through the conduit  184 , the conduit  184   a  and into the input port  188 B of the reservoir  188  is deflected by the member  188 D and flows out the port  188 A. Output whole blood flow from the port  188 A via a conduit  189  is pumped by the feed pump  190  at a flow rate of 70-80 ml per minute into the input port  162   a  of the two part separation chamber  160 . 
     Red blood cells separated in the chamber  162  flow via conduit  192  into the input port  188 C of the reservoir  188  and are accumulated therein. Assuming clamp  2  is closed and clamp  1  is open, platelet poor plasma separated in the platelet chamber  164  flows via the output port  162   b  and the pump  141  through a fluid flow conduit  194  also into the reservoir  188 . 
     In operation, set  182  would be coupled to the donor by means of the cannula  88   a . The chamber  160  would be positioned in the receiving chamber of the dual member centrifuge  12 . Clamp  1  would be opened and clamp  2  would be closed. 
     Whole blood would then be drained through the conduit  184  as discussed above at a 70 to 80 ml per minute rate. When the reservoir  188  is filled with a predetermined maximum extracorporeal volume, the volume/weight detector will generate an appropriate signal. At such time, the bidirectional donor pump  186  will be reversed. Fluid will then be drawn from the reservoir  188  out the port  188 B via the fluid flow conduit  138   a  and the bubble trap/bubble detector  15 D to the fluid flow conduit  184 . The fluid will then be returned to the donor via the conduit  88  and the cannula  88   a.    
     The return rate of the concentrated cells, including red blood cells and plasma, is on the order of 130 to 150 ml per minute. This substantially increased return fluid flow rate provides the important advantage in that the time necessary to return the concentrated cells to the donor is approximately half of the time required for the draw cycle. While the concentrated cells are being returned to the donor, fluid continues to be pumped from the reservoir  188  via the port  188   a  via the feed pump  190  through the separation chamber  160  and back to the donor via the port  188   c . Additional volume flow rate can come directly from the reservoir  188 . Platelets continue to accumulate in the chamber  164 . 
     The draw cycle can then be reinitiated and an additional quantity of blood drawn from the donor. When the desired quantity of platelets has been accumulated in the chamber  164 , clamp  1  can be closed and clamp  2  can be opened. The platelets then need to be resuspended. By means of the pump  141 , the platelets in the chamber  164  can then be pumped into the container  198 . Quantities of platelets on the order of 4×10 11  tells can be accumulated using the system and apparatus in FIG. 11 in a time interval on the order of 50 minutes. 
     With respect to the embodiment of FIG. 5C, the use of the dam or shim  112  illustrated therein allows priming of a dry fluid transfer system with whole blood and prevents the occurence of potential air locks which would hinder the flow of plasma and/or platelets in the fluid flow conduits during high speed centrifugation. The shim or dam  112 , as noted previously, can be formed as part of the separation chamber  50 . Alternately, it can be formed as part of the rotatable receiving chamber  40 . 
     Many of the known cell separation systems require saline priming of the separation chambers prior to the pheresis operation. As a result, it is necessary to supply a container of sterile saline as part of the transfer set. During set up, a frangible in the saline container is broken permiting the saline to flow into the separation chamber driving out any air present therein and providing a liquid filled separation chamber. 
     The separation chamber  50  of FIG. 5C does not require the use of saline for priming. The various ports have been located on the separation chamber  50 , taking into account different fluid densities. The ports are located in different planes of the centrifugal force field F. For example, the input whole blood port  50 A is centrally located with respect to the force field. The plasma output port  50 B is located adjacent the relatively low force interior wall of the separation chamber  50 . The residual fluid output port  50 C for the concentrated or packed red blood cells is located adjacent the maximum force exterior wall of the separation chamber  50 . 
     Directing of the fluids to the various output ports is accomplished by means of essentially rigid deflecting members such as the shim or dam  112  adjacent the separated component or plasma output port  50 B. A shim or dam  112 A is associated with the concentrated red blood cell output port  50 C. The interface surface  110  which is illustrated in FIG. 5C formed as part of the outer wall  40   a  of the receiving chamber  40  directs the flow of separated plasma cells. 
     The dams or shims  112  and  112 A are also effective to prevent the flow of air through the plasma port. Since air has a lower density then plasma, a certain amount of air will remain in the inner most region of the separation chamber  50 . This air is also compressed at higher centrifuge speeds. 
     The problem posed by air in the system is a result of pressures induced by the centrifugal force field F. These forces are proportional to the square of the radius of the receiving chamber as well as the square of the rotational velocity of the receiving chamber and the separation chamber  50  along with the density of the fluid. If air gets into the fluid flow conduit associated with the output port  50 B, a pressure drop will occur in that line. This pressure drop may force the plasma pump to clamp the tubing shut and stop the flow of plasma by requiring too high a vacuum in the conduit. Alternately, the pump may degas the plasma. 
     Overcoming this condition requires that the receiving chamber  40  and separating chamber  50  be slowed down until the plasma pump can overcome this pressure drop. Hence, the use of the saline in the known devices to drive all of the air out of the separation chamber and the related fluid flow conduits. On the ocher hand, in the embodiment of. FIG. 5C the shims or dams  112  and  112   a  prevent movement of the air out of the separation chamber  50  by creating a reservoir which will trap the air within the chamber during a low speed prime with blood. At high speed operation, the centrifugal induced pressure will compress this air away from the dam  112 . The presence of a small amount of air in the chamber will not interfere with the pheresis process as long as the air is not permitted to escape into the fluid flow conduits associated with the output port of the chamber. 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the true spirit and scope of the novel concept of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.