Patent Publication Number: US-6902539-B2

Title: Extracorporeal blood processing methods and apparatus

Description:
This application is a divisional of U.S. application Ser. No. 08/914,405 filed on Aug. 19, 1997, now U.S. Pat. No. 6,613,019, which is a divisional of U.S. application Ser. No. 08/480,617 filed Jun. 7, 1995, now U.S. Pat. No. 5,702,357. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to the field of extracorporeal blood processing and, more particularly, to methods and apparatus which may be incorporated into an apheresis system (e.g., blood component collection, therapeutic). 
     BACKGROUND OF THE INVENTION 
     One type of extracorporeal blood processing is an apheresis procedure in which blood is removed from a donor or patient, directed to a blood component separation device (e.g., centrifuge), and separated into various blood component types (e.g., red blood cells, white blood cells, platelets, plasma) for collection or therapeutic purposes. One or more of these blood component types are collected (e.g., for therapeutic purposes), while the remainder are returned to the donor or patient. 
     A number of factors affect the commercial viability of an apheresis system. One factor relates to the operator of the system, specifically the time and/or expertise required of an individual to prepare and operate the apheresis system. For instance, reducing the time required by the operator to load and unload the disposables, as well as the complexity of these actions, can increase productivity and/or reduce the potential for operator error. Moreover, reducing the dependency of the system on the operator may lead to reductions in operator errors and/or to reductions in the credentials desired/required for the operators of these systems. 
     Donor-related factors may also impact the commercial viability of an apheresis system and include donor convenience and donor comfort. For instance, donors typically have only a certain amount of time which may be committed to visiting a blood component collection facility for a donation. Consequently, once at the collection facility the amount of the donor&#39;s time which is actually spent collecting blood components is another factor which should be considered. This also relates to donor comfort in that many view the actual collection procedure as being somewhat discomforting in that at least one and sometimes two access needles are in the donor throughout the procedure. 
     Performance-related factors continue to affect the commercial viability of an apheresis system. Performance may be judged in terms of the “collection efficiency” of the apheresis system, which may in turn reduce the amount of donation time and thus increase donor convenience. The “collection efficiency” of a system may of course be gauged in a variety of ways, such as by the amount of a particular blood component type which is collected in relation to the number of this blood component type which passes through the apheresis system. Performance may also be evaluated based upon the effect which the apheresis procedure has on the various blood component types. For instance, it is desirable to minimize the adverse effects on the blood component types as a result of the apheresis procedure (e.g., reduce platelet activation). 
     SUMMARY OF THE INVENTION 
     The present invention generally relates to extracorporeal blood processing. Since each of the various aspects of the present invention may be incorporated into an apheresis system (e.g., whether for blood component collection in which “healthy” cells are removed from the blood or for therapeutic purposes in which “unhealthy” cells are removed from the blood), the present invention will be described in relation to this particular application. However, at least certain of the aspects of the present invention may be suited for other extracorporeal blood processing applications and such are within the scope of the present invention. 
     An apheresis system which may embody one or more aspects of the present invention generally includes a blood component separation device (e.g., a membrane-based separation device, a rotatable centrifuge element, such as a rotor, which provides the forces required to separate blood into its various blood component types (e.g., red blood cells, white blood cells, platelets, and plasma)). In one embodiment, the separation device includes a channel which receives a blood processing vessel. Typically, a healthy human donor or a patient suffering from some type of illness (donor/patient) is fluidly interconnected with the blood processing vessel by an extracorporeal tubing circuit, and preferably the blood processing vessel and extracorporeal tubing circuit collectively define a closed, sterile system. When the fluid interconnection is established, blood may be extracted from the donor/patient and directed to the blood component separation device such that at least one type of blood component may be separated and removed from the blood, either for collection or for therapy. 
     A first aspect of the present invention relates to enhancing the ease of loading a blood processing vessel into a channel which is associated with a centrifuge rotor. In one embodiment of this first aspect, the centrifuge rotor includes a blood processing vessel loading aperture in its sidewall which extends only part of the way through the centrifuge rotor and then extends upwardly through the top of the centrifuge rotor. The centrifuge rotor thereby provides an opposing surface to the portion of the loading aperture which may be characterized as laterally extending. The loading aperture within the centrifuge rotor may then be properly characterized as being substantially L-shaped. When the disposable blood processing vessel is inserted into this opening, it is deflected upwardly through the centrifuge rotor. The operator may then grasp the blood processing vessel and load it into the channel. 
     Another embodiment of this first aspect relates to a drive assembly for a centrifuge rotor assembly. The rotor assembly includes a rotor housing, a channel mounting having a channel associated therewith, and a single gear which rotatably interconnects the rotor housing and channel mounting. Through use of this single gear and by having this single gear be radially offset in relation to the above-described loading aperture in the centrifuge rotor, the access to the loading aperture is not substantially affected by the drive assembly for the centrifuge rotor. For instance, by radially offsetting the single drive gear in relation to a plane which bisects the loading aperture, any counterweights which are used to establish rotational balance of the centrifuge rotor will be disposed so as to not adversely affect access to the loading aperture. 
     A second aspect of the present invention relates to the cross-sectional configuration of at least a portion of a channel associated with a channel housing which is interconnectable with a blood component separation device. Generally, the channel itself is configured so as to retain the blood processing vessel therein during the apheresis s procedure. This is particularly desirable in the case of the blood component collection device being a Centrifuge which is operated at high rotational speeds, such as greater than 2,500 RPM and even up to about 3,000 RPM. In one embodiment, for at least a portion of the length of the channel a lip extends partially across an upper portion of the channel. 
     The lip in this second aspect may be provided by configuring at least one of the inner and outer channel walls with a generally C-shaped cross-sectional configuration. In this case, both the upper and lower portions of the channel having the noted lip would have reduced widths in comparison with the middle portion of the channel. These reduced width upper and lower portions of the channel may receive portions of a blood processing vessel which are sealed together. The channel configuration would then also serve to reduce the stresses experienced by these seals when the blood processing vessel is pressurized during the apheresis procedure. 
     A third aspect of the present invention relates to a blood processing vessel, and more specifically to a blood processing vessel which may be effectively loaded within a channel. In one embodiment of this third aspect, the blood processing vessel provides a continuous flow path by overlapping and radially off-setting first and second ends and utilizing first and second connectors. The first and second connectors are each positioned between the two ends of the blood processing vessel, communicate with the interior of the blood processing vessel, and when engaged facilitate the loading the blood processing vessel into the channel in the correct position. One of the connectors may be a stub-like structure which extends outwardly from the inner sidewall of the blood processing vessel, while the other connector may be a stub-like structure which extends outwardly from the outer sidewall of the blood processing vessel. 
     Another embodiment of this third aspect is a blood processing vessel which is particularly useful for the channel described in the second aspect above. In this regard, the blood processing vessel is sufficiently rigid so as to not only be free-standing, but to be loaded into the channel of the second aspect as well. However, the blood processing vessel is still sufficiently flexible so as to be able to substantially conform to the shape of the channel during an apheresis procedure. This is particularly desirable when the channel is shaped to provide one or more desired functions regarding the apheresis procedure. 
     Once the blood processing vessel is loaded into the channel, at least the blood processing vessel must be primed. In this regard, a fourth aspect of the present invention relates to priming, preferably with blood. A channel associated with a channel housing, which is rotatably interconnected with a centrifuge rotor, includes a first cell separation stage. The first cell separation stage is sized such that a ratio of a volume of the channel which does not have RBCs to a volume of the channel which does have RBCs is no greater than one-half of one less than the ratio of the hematocrit of blood entering the channel to the hematocrit of red blood cells exiting the channel. With this configuration, blood may be used to prime the blood processing vessel when disposed within the channel, and thus the channel may be properly characterized as “blood-primable.” 
     In one embodiment of this fourth aspect, the channel extends generally curvilinearly about a rotational axis of the channel housing in a first direction. The channel includes, progressing in the first direction, the first cell separation stage, a red blood cell dam, a platelet collection area, a plasma collection area, and an interface control region for controlling a radial position of at least one interface between red blood cells and an adjacent blood component type(s) (e.g., a buffy coat of WBCs, lymphocytes, and platelets). Blood introduced into the channel is separated into layers of red blood cells, white blood cells, platelets, and plasma in the first cell separation stage. Preferably, throughout the apheresis procedure and including the priming of the blood processing vessel, only separated platelets and plasma flow beyond the red blood cell dam where the platelets may be removed from the channel in the platelet collection area. This is provided by an interface control mechanism which is disposed in the interface control region of the channel and which maintains the position of the interface between separated red blood cells and the buffy coat such that this condition is maintained. 
     Although the term “blood prime” is subject to a variety of characterizations, in each case blood is the first fluid introduced into the blood processing vessel. One characterization of the blood prime is that separated plasma is provided to the interface control region before any separated red blood cells flow beyond the red blood cell dam into the platelet collection area. Another characterization is that blood and/or blood component types occupy the entire fluid-containing volume of the blood processing vessel before any separated red blood cells flow beyond the red blood cell dam into the platelet collection area. 
     One configuration of the channel which allows for a blood priming of the blood processing vessel when loaded within the channel is one in which the volume of that portion of the channel which principally contains plasma during the apheresis procedure is small in comparison to the volume of that portion of the channel which principally contains red blood cells during the apheresis procedure. This allows plasma to be provided to the interface control region of the channel before red blood cells flow beyond the red blood cell dam into the platelet collection stage to provide the red blood cell-buffy coat interface control function. That degree of “small” of the noted channel portion volume which allows for blood priming may be specifically defined in relation to a reference circle which has its origin on the rotational axis of the centrifuge housing and which intersects the channel at a predetermined location on the red blood cell dam. The volume of the channel which principally contains separated plasma in the apheresis procedure is disposed inside of this reference circle (e.g., V PL ) and the volume of the channel which principally contains separated red blood cells in the apheresis procedure is disposed outside of this reference circle (e.g., V RBC ). In one embodiment the ratio of V PL /V RBC  is no greater than about 0.3, and preferably no greater than about 0.25. This desired ratio may be achieved by having the width of the channel between the platelet collection area and the plasma collection area be less than the width of the channel throughout the first cell separation stage. By utilizing this reduced width, the configuration of the channel between the platelet collection area and the plasma collection area may utilize substantially vertically extending and planar inner and outer channel walls. 
     A fifth aspect of the present invention relates to priming a blood processing vessel disposed in a channel of a channel housing. Blood is used in the prime and the invention also accommodates for the removal of air from the blood processing vessel during this prime. A donor/patient blood transfer assembly fluidly interconnects the blood processing vessel and a donor/patient, and may include an air receptacle for receiving air which is displaced from the blood processing vessel by the blood priming. The various features associated with the channel of the above-noted fourth aspect of the invention may be utilized in this fifth aspect as well. 
     A sixth aspect of the present invention relates to blood priming an apheresis system which includes a channel housing having a blood processing channel associated therewith, a blood processing vessel disposed in the channel and which has a blood inlet port, red blood cell outlet port, and an interface control port. The interface control port is used to control the radial position of at least one interface between separated red blood cells and a blood component type(s) disposed adjacent the separated red blood cells. 
     A method of this sixth aspect includes the steps of rotating the channel housing with the blood processing vessel positioned in its channel, introducing blood into the blood processing vessel to prime the same, and separating the blood into at least red blood cells, platelets, and plasma. The red blood cells are restricted from flowing beyond the red blood cell dam throughout the procedure, including in the priming of the blood processing vessel. In this regard, a flow of plasma is provided to the interface control port before any of the red blood cells are able to flow beyond the red blood cell dam. Once this plasma reaches the interface control port, control is established of the radial position of the interface between the separated red blood cells and the adjacent blood component type(s) such that the potential for red blood cells flowing beyond the red blood cell dam is reduced. One or more of the various features discussed above with regard to the fourth and fifth aspects noted above may be incorporated into this sixth aspect as well. 
     A seventh aspect of the present invention is a method which may be utilized to prime a blood processing vessel disposed in a channel of a channel housing with blood. In this method, the blood processing vessel is disposed in the channel on the channel housing and a donor/patient blood transfer assembly fluidly interconnects a donor/patient with this blood processing vessel. The method generally includes the steps of initiating the flow of blood from the donor/patient to the donor/patient blood transfer assembly while rotating the channel housing at a first rotational velocity. Once the flow of blood reaches the blood processing vessel, the rotational velocity of the channel housing is increased to a second rotational velocity. Once the entirety of the blood processing vessel contains either blood and/or one or more blood component types, the rotational velocity of the channel housing is once again increased to a third rotational velocity. In one embodiment, the first rotational velocity ranges from about 180 RPM to about 220 RPM, and is preferably about 200 RPM, the second rotational velocity ranges from about 1,800 RPM to about 2,200 RPM and is preferably about 2,000 RPM, and the third rotational velocity ranges from about 2,700 RPM to about 3,300 RPM, and is preferably about 3,000 RPM. Although a three-step approach may be utilized in the practice of the method of this seventh aspect, the centrifuge speed need not stay at a fixed velocity during each of the three “stages” (e.g., the first stage being priming the extracorporeal circuit from the donor/patient to the blood processing vessel, the second stage being priming the blood processing vessel, and the third stage being the remainder of the apheresis procedure). One or more of the various features discussed above with regard to the fourth, fifth and sixth aspects noted above may be incorporated into this seventh aspect as well. 
     An eighth aspect of the invention relates to priming the apheresis system with blood. The apheresis system includes a channel housing having a channel associated therewith, a blood processing vessel disposed in the channel, a donor/patient blood transfer assembly which fluidly interconnects a donor/patient with the blood processing vessel and which includes a blood reservoir. A method in accordance with this eighth aspect includes performing first and second drawing steps. The first drawing step includes drawing blood from the donor/patient through a first portion of the donor/patient blood transfer assembly and into the blood reservoir. After this first drawing step is terminated, the blood processing vessel is primed with the donor/patient&#39;s blood by performing the second drawing step. The second drawing step includes drawing blood from the donor/patient, through a second portion of the donor/patient blood transfer assembly, through the blood processing vessel, and back into the blood reservoir. One or more of the various features discussed above with regard to the fourth, fifth, sixth, and seventh aspects noted above may be incorporated into this eighth aspect as well. 
     A ninth aspect of the present invention relates to the introduction of blood into the blood processing vessel such that the blood may be separated into at least two blood component types and further such that at least one of these blood component types may be removed from the blood processing vessel via a blood component outlet port. The blood processing vessel includes two interconnected sidewalls (e.g, substantially planar surfaces which define the main body of the fluid-containing volume of the blood processing vessel) and the blood inlet port extends through one of these sidewalls. Generally, the blood exits the blood inlet port within the interior of the blood processing vessel in a direction which is at least partially in the direction of the primary flow of blood through the channel. This introduction of blood into the blood processing vessel is subject to a number of characterizations. For instance, the introduction may be characterized as the blood exiting the blood inlet port into the interior of the blood processing vessel at an angle of less than 90° relative to a reference line extending perpendicularly to the channel wall which interfaces with the blood inlet port. The introduction may be further characterized as exiting the blood inlet port in a direction which is substantially parallel with a direction of flow adjacent the blood inlet port. In one embodiment, red blood cells may actually flow along the outer wall of the blood processing vessel past the blood inlet port such that the noted introduction of blood into the blood processing vessel may be further characterized as reducing the potential for disturbing this flow of red blood cells and/or as reducing an effect on flow characteristics in the area of the blood processing vessel in which blood is introduced. The introduction may be further characterized as exiting the blood inlet port in a direction which is substantially parallel with the sidewall of the blood processing vessel which interfaces with the blood inlet port. 
     A tenth aspect of the present invention relates to the removal of platelets from the blood processing vessel. This tenth aspect is based upon the blood processing vessel and part of the adjacent channel wall of the channel collectively defining a generally funnel-shaped blood component collect well which collects at least one blood component type flowing thereby (e.g., platelets). In one embodiment, the blood processing vessel includes a blood inlet port and a first blood component outlet port. A support is disposed proximate the blood component outlet port and exteriorly relative to the fluid-containing volume of the blood processing vessel. This support is contoured to direct the desired blood component type(s) toward the blood component outlet port and is in an overlapping relation with the exterior surface of the blood processing vessel. The support may be separable from the blood processing vessel such that it may be positioned between the blood processing vessel and the associated channel wall after the vessel is loaded into the channel. The support may also be fixedly interconnected with the blood processing vessel in some manner. For instance, the support may be pivotally or hingedly interconnected with the exterior of the blood processing vessel to facilitate loading of the blood processing vessel and/or to allow the support to move into a predetermined position upon pressurization of the blood processing vessel during an apheresis procedure to perform the desired function. Moreover, the support may be integrally formed with the associated blood component outlet port. 
     In another embodiment relating to this tenth aspect, the channel includes inner and outer channel walls and part of a generally funnel-shaped blood component collect well is formed in at least one of these channel walls. That is, the remainder of the funnel-shaped blood component collect well is defined by the blood processing vessel, such as described above in relation to the first embodiment of this tenth aspect. In order to allow the above-described blood processing vessel to be effectively loaded into the blood processing channel, specifically one of its blood component outlet ports, a blood component outlet port recess extends radially beyond the portion of the blood component collect well defined by the channel wall (e.g., if the well is on the outer wall of the channel, this would be further radially outwardly, whereas, if the well is on the inner wall of the channel, this would be further radially inwardly). This recess may also be configured so as to allow the above-noted contoured support, which interfaces with the exterior of the blood processing vessel, to move into a predetermined position upon pressurization of the blood processing vessel to direct the desired blood component type(s) into the blood component collect port. 
     In another embodiment of this tenth aspect, a method for processing blood in an apheresis system includes the steps of loading a blood processing vessel in a channel on a channel housing. A contoured support is disposed between the channel and the blood processing channel. When blood is introduced into the blood processing vessel and the channel housing is rotated to separate the blood into various blood component types, a generally funnel-shaped platelet collect well is defined by conforming one part of the blood processing vessel to the channel and by further conforming another part of the blood processing vessel to the shape of the support interfacing with the blood processing vessel. In order to further define this generally funnel-shaped platelet collect well, pressurization of the blood processing vessel may move the support into a predetermined position. For instance, this may then allow the support to direct the platelets toward a platelet collect port on the blood processing vessel. 
     An eleventh aspect of the present invention relates to a control port which assists in automatically controlling (i.e., without operator action) the location of an interface between red blood cells and a buffy coat relative to a red blood cell dam. The red blood cell dam restricts the flow of separated red blood cells to a platelet collect port. The control port extends through the blood processing vessel and removes plasma and red blood cells as required in order to reduce the potential for red blood cells flowing “over” the red blood cell dam to the platelet collect port. The “selective” removal of red blood cells from the blood processing vessel through the control port function is based at least in part upon its position within the channel. That is, the automatic control provided at least in part by the control port is predicated upon the control port assuming a predetermined radial position within the channel. In order to facilitate achieving this predetermined radial position within the channel, the disposition of the control port is provided independently of the thickness of the blood processing vessel. Specifically, the position of the control port is not dependent upon the thickness of the materials which form the blood processing vessel. 
     The desired objective for the control of this eleventh aspect of the present invention may be affected by interconnecting a support or shield-like structure with the control port and disposing this support over an exterior surface of the blood processing vessel. This support may then be positioned against an interior surface of the channel, preferably within a recess which is specifically designed to receive the support. This support may also be more rigid than the blood processing vessel itself which reduces the potential for any significant change in the radial position of the control port when the blood processing vessel is pressurized (e.g., any radial movement within a slot which receives the control port and which allows the control port to extend within the channel). These support or shield-like members may also be used for other blood inlet/outlet ports on the blood processing vessel to similarly maintain the associated port in a predetermined position and/or to reduce the discontinuity along the part of the channel with which the port interfaces. 
     A twelfth aspect of the present invention relates to a packing factor associated with the separated blood component types in a separation stage(s) of the blood processing vessel. The packing factor is a number which reflects the degree with which the blood component types are “packed together” in the separation stage(s) and is dependent at least upon the rotational speed of the channel housing and the flow rate into the blood processing vessel. The packing factor may be characterized as a dimensionless “density” of sorts of the blood component types in the separation stage(s). 
     One embodiment of this twelfth aspect is a method which includes the steps of rotating the channel housing, providing a flow to the blood processing (e.g., the flow includes blood and typically anticoagulant as well), separating the blood into a plurality of blood component types, and adjusting the rotational speed of the channel housing based upon a certain change in the flow rate. Since the packing factor is dependent upon the rotational speed of the channel housing and the flow rate into the blood processing vessel, the methodology of this eleventh aspect may be used to maintain a substantially constant and predetermined packing factor. In this regard, preferably the packing factor is maintained between about 11 and about 15, and preferably about 13. 
     Another embodiment of this twelfth aspect is a method for processing blood in an apheresis system in which a blood processing vessel is disposed in a channel of a channel housing. The method includes the steps of rotating the channel housing, providing a flow of blood (typically anticoagulated) to the blood processing vessel at a rate ranging from about 40 milliliters per minute to about 70 milliliters per minute, separating the blood into a plurality of blood component types in a first stage of the channel, and removing at least one of the blood component types from the blood processing vessel. Throughout the separating step, a packing factor of at least about 10, and more preferably at least about 10.2, is maintained in the first stage. For flow rates up to about 50 milliliters per minute, the packing factor is more preferably maintained at about 13 which may be achieved by rotating the channel housing at speeds greater than 2,500 RPM and typically closer to about 3,000 RPM. 
     Another embodiment of this twelfth aspect of the present invention relates to the configuration of a channel associated with a channel housing which is rotatably interconnected with a centrifuge rotor. The channel includes a first cell separation stage and a first blood component collection stage which are separated by a cell dam. At least one type of blood component is separated from remaining portions of the blood in the first cell separation stage and flows beyond the cell dam into the first blood component collection stage, while at least one other type of blood component is preferably precluded from flowing beyond the cell dam into the first blood component collection stage. The width or sedimentation distance of the channel on the end of the first cell separation stage disposed closest to the cell dam is less than the width or sedimentation distance of the channel on the opposite end of the first cell separation stage. In one embodiment, the width/sedimentation distance of the channel in the first cell separation stage is progressively reduced approaching the cell dam. When the above-identified types of packing factors are utilized, this channel configuration may be used to reduce the volume of a buffy coat (white blood cells, lymphocytes, and platelets) between separated red blood cells and platelets in the first stage, and thus reduces the number of platelets that are retained within the first cell separation stage. 
     A thirteenth aspect of the present invention relates to the rinseback operation at the end of the apheresis procedure in which attempts are made to remove the remaining contents of the blood processing vessel and provide the same back to the donor/patient. In one embodiment, one or more ports of the blood processing vessel, which interface with the sidewall of the blood processing vessel, are configured in a manner which reduces the potential for any closure of the port(s) during the rinseback procedure due to interconnecting one or more pumps with these ports. The port(s) is configured so as to have an orifice displaced from the radially outwardmost end of the port. This may be provided by configuring the end of the port to have the orifice positioned between two protrusions such that the orifice is recessed inwardly of the protrusions. Consequently, if the opposing portion of the blood processing vessel engages the protrusions during rinseback, the orifice is retained away from the blood processing vessel so as to not block the flow to the orifice. 
     In another embodiment relating to this thirteenth aspect, at least one narrowed portion within the blood processing vessel extends downwardly from at least one of the blood component outlet ports interfacing with the sidewall of the blood processing vessel toward a lower portion of the blood processing vessel. As such, during rinseback a drawing-like action, for instance achieved by pumping from the blood processing vessel out the blood component outlet port(s), is initiated in a lower portion of the blood processing vessel where the contents of the blood processing vessel will be if rotation of the channel housing is terminated during rinseback as preferred. A second narrowed portion may extend downwardly from the noted blood component outlet port such that one passageway extend away from the port in opposing directions and such that the drawing-like action is initiated in two displaced locations. 
     A fourteenth aspect of the present invention relates to facilitating insertion/loading and removal of a blood processing vessel to and from, respectively, a channel associated with a channel housing upon completion of an apheresis procedure. Generally, the blood processing vessel may be removed from and loaded into the channel by engaging structure which does not have any flow therethrough during the apheresis procedure. This may be achieved by interconnecting at least one and preferably a plurality of tabs or the like with the blood processing vessel. These tabs extend beyond the fluid-containing volume of the blood processing vessel and preferably extend beyond the channel when the vessel is loaded within the channel. As such, the tab(s) may be grasped by the operator of the apheresis system to load and unload the blood processing vessel to/from the channel. These tabs or the like may be particularly useful when there is some resistance to insertion/removal of the blood processing vessel from the channel, such as when a lip is formed on the upper portion of the channel as discussed in relation to the second aspect. 
     A fifteenth aspect of the present invention relates to providing a graphical operator interface for the procedure. This graphical operator interface pictorially displays to the operator at least a portion of the steps for the apheresis procedure, at least one of which requires some type of operator action. These steps may be pictorially displayed in the order in which they are to be performed. In order to further enhance operator recognition of the ordering of the pictorially displayed apheresis steps, the pictorials may also be numbered. Although the pictorials may alone convey to the operator the desired/required action, short textual descriptions may also be used in combination with the pictorials. 
     The pictorials may also be utilized to indicate the status of the apheresis procedure to the operator, such as by color or shade differentiation. For instance, three-way color or “shade” differentiation (e.g., in the case of colors using three different colors, and in the case of shade using the same general color but different levels of “darkness”) may be utilized to indicate to the operator one of three conditions pertains to the step(s) associated with a particular pictorial. One color or shade may be utilized to indicate that the step(s) associated with the pictorial are untimely (e.g., not yet ready for execution), while another color or shade may be utilized to indicate that the step(s) associated with the pictorial are timely (e.g., ready for execution and/or are currently being executed), while yet another color or shade may be utilized to indicate that the step(s) associated with the pictorial have been executed. The status may also be conveyed by providing further indicia that the step(s) associated with a given pictorial have been completed. 
     The pictorials may further function as an operator input device. For instance, touch screen principles may be utilized such that the operator will touch one of the pictorials on the display when the operator is ready to execute the step(s) associated with the pictorial. This touch screen activation may generate one or more additional pictorials which graphically convey to the operator one or more steps or substeps which need to be undertaken at that particular time in the apheresis procedure. 
     A sixteenth aspect of the present invention also relates to an interface between the apheresis system and the operator. One embodiment of this sixteenth aspect is a method which includes the steps of instructing the apheresis system to address a first condition associated with the apheresis system by performing a first protocol. Typically, this “first condition” will be some type of problem associated with the apheresis system which may be resolved in a multiplicity of ways (e.g., at least two), such as by performing the first protocol or by performing a second protocol. That is, the methodology relates to “programming” the apheresis system to address or “correct” the first condition in one out of a plurality of ways and which does not allow/require the operator to make any decisions regarding how to address or “correct” the first condition. 
     In this embodiment of the sixteenth aspect, the methodology includes the steps of introducing blood into a blood separation device, separating the blood into a plurality of blood component types, and removing at least one of the blood component types from the device. The methodology also includes the step of identifying the existence of the first condition relating to the apheresis system and thereafter having the apheresis system perform the first protocol. This “identification” of the first condition may be based upon the operator observing the first condition and inputting information relating to the existence of the first condition to the apheresis system. This methodology may be effectively integrated into and/or utilize the graphical interface discussed above in relation to the fifteenth aspect of the invention. 
     Another embodiment relating to this sixteenth aspect relates to the apheresis system utilizing the operator to address potential problems associated with the apheresis procedure. A method of this sixteenth aspect includes the steps of introducing blood to the blood separation device, separating the blood into a plurality of blood component types, and removing at least one of these blood component types from the blood separation device. The method further includes the step of detecting the potential existence of a “first condition” associated with the apheresis procedure. This “first condition” is typically some potential problem and may be detected by the system itself (e.g., through appropriate detectors/sensors/monitors), the operator, and/or the donor/patient. Once this first condition is detected, the operator is prompted by the apheresis system (e.g., via a computer interface) to perform an investigation of the system or a particular portion thereof. The operator is also prompted to specify the result of this investigation to the system. Based upon the operator&#39;s response to the investigation, the system may prompt the operator to take further action (e.g., to address the first condition in a particular manner). Once again, this methodology may be effectively integrated into and/or utilize the graphical interface discussed above in relation to the fifteenth aspect of the invention. 
     A seventeenth aspect of the present invention relates to a disposable assembly for extracorporeal blood processing that utilizes a single pressure sensing device to monitor positive and negative pressure changes in both the blood removal line and blood return line interconnectable with a donor/patient. In one embodiment, a pressure sensitive diaphragm member contacts blood on one side within a module of a molded cassette member, which cassette member may also include an integrally defined internal passageway fluidly interconnecting the module with both the blood removal and blood return lines. The use of a single pressure sensor reduces component costs and complexity, and yields significant accuracy advantages. 
     An eighteenth aspect of the present invention further pertains to a disposable assembly for extracorporeal blood processing having a single needle for removal/return of whole blood/uncollected blood components, a reservoir fluidly interconnected to the single needle for accumulating blood components, and a gas holding means fluidly interconnected to the reservoir for receiving gas from the reservoir and returning the gas to the reservoir as the reservoir cyclically accumulates and disposes uncollected blood components during a blood processing operation. In one embodiment, the reservoir is integrally defined within a molded cassette member. The provision of a gas holding means avoids a high internal pressure buildup as the reservoir is filled with returned blood components, thereby reducing gas entrainment at the liquid/gas interface and lowering the seal requirements for the reservoir and interconnected components. 
     A nineteenth aspect of the present invention relates to an extracorporeal blood processing device which includes a cassette member having a reservoir for accumulating uncollected blood components, and upper and lower ultrasonic sensors positionable adjacent to the reservoir and being responsive to the presence or absence, respectively, of fluid adjacent thereto within the reservoir to trigger the start and stop of blood return cycles. In a related aspect, each of the upper and lower ultrasonic sensors may advantageously comprise a contact surface for direct, dry-docking with the reservoir, thereby avoiding the need for the use of a docking gel or other like coupling medium. 
     A twentieth aspect of the present invention relates to an extracorporeal blood processing device that comprises a cassette member having a reservoir, at least first and second flexible tubing lines adjacently interconnected to the cassette member in predetermined spaced relation, a collection means interconnected to one of the flexible tubing lines, and an interfacing valve assembly having a moveable member selectively positionable to occlude one of the tubings lines, such that in a first mode of operation a separated blood component will be collected in the collection means, and in a second mode of operation the separated blood component will be diverted into the reservoir. In one embodiment, multiple sets of corresponding first and second tubing lines/collection means/and valve assemblies are provided, with each of the sets providing for selective diversion of a blood component into a separate collection means or common reservoir. Utilization of this arrangement yields a compact disposable that can be readily mounted relative to the divert valve assemblies in a reliable manner. 
     A twenty-first aspect of the present invention relates to loading of a disposable cassette member having a plurality of tubing loops extending therefrom relative to a plurality of flow control devices and at least one sensing device for extracorporeal blood processing. A mounting means is employed for selectively, securably and supportably receiving the cassette member in a substantially fixed position relative thereto, and the mounting means is selectively moveable between first and second locations wherein upon moving the mounting means from the first to second location, the tubing loops move into an operative position with corresponding ones of the flow control devices and the cassette member moves into a proper position for operation of the sensing means. In one embodiment, the sensing means includes at least one pressure sensor for monitoring the fluid pressure within a blood removal passageway of the cassette member, and further includes ultrasonic sensors for monitoring the fluid level of accumulated, uncollected blood components within a reservoir of the cassette. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of an apheresis system; 
         FIGS. 2A-2B  illustrate an extracorporeal tubing circuit and cassette assembly thereof for the system of  FIG. 1 ; 
         FIG. 3  is a front view of a pump/valve/sensor assembly for the system of  FIG. 1 ; 
         FIGS. 4A-4B  are cross-sectional side views of first and second pressure sensing modules of the extracorporeal tubing circuit of  FIGS. 2A-2B  coupled with corresponding pressure sensors of the pump/valve/sensor assembly of  FIG. 1 ; 
         FIG. 5  is a cross-sectional side view of the upper and lower ultrasound sensors of the pump/valve/sensor assembly of  FIG. 3  coupled with a reservoir of the cassette assembly of the extracorporeal tubing circuit of  FIGS. 2A-2B ; 
         FIG. 6  is a cross-sectional side view of a platelet divert valve subassembly of the pump/valve/sensor assembly of  FIG. 3 ; 
         FIG. 7  is illustrates a loading assembly for a cassette mounting plate of the pump/valve/sensor assembly of  FIG. 3 ; 
         FIG. 8  is an exploded, perspective view of the channel assembly from the system of  FIG. 1 ; 
         FIGS. 9-9B  is a top view of the channel housing from the channel assembly of  FIG. 8  illustrating various dimensions; 
         FIG. 10  is a cross-sectional view taken along line  10 — 10  of  FIG. 9 ; 
         FIG. 11A  is a cutaway, perspective view of the platelet collect well region of the channel housing of  FIG. 8 ; 
         FIG. 11B  is a lateral cutaway view, looking upwardly of the platelet collect well region of the channel housing of  FIG. 8 ; 
         FIG. 12  is a cross-sectional view of the channel housing taken along line  12 — 12  in  FIG. 9 ; 
         FIG. 13  is a cross-sectional view of the channel housing taken along line  13 — 13  in  FIG. 9 ; 
         FIG. 14A  is a top view of the blood inlet port slot, the RBC outlet slot, and the control port slot on the channel housing of  FIG. 8 ; 
         FIG. 14B  is a cutaway, perspective view of the whole blood inlet port slot region of the channel housing of  FIG. 8 ; 
         FIG. 14C  is a cutaway, perspective view of the control port slot region of the channel housing of  FIG. 8 ; 
         FIG. 15  is a top view of the channel of  FIG. 8  illustrating the ratio of the plasma volume to the red blood cell volume; 
         FIG. 16  is a perspective view of the blood processing vessel of the channel assembly of  FIG. 8  in a disassembled state; 
         FIG. 17  is a cross-sectional view of the blood processing vessel at the interconnection; 
         FIG. 18  is cross-sectional view of the blood processing vessel taken along lines  18 — 18  in  FIG. 16 ; 
         FIG. 19A  is a cutaway, perspective view of the blood inlet port assembly for the blood processing vessel of  FIG. 8 ; 
         FIG. 19B  is a longitudinal cross-sectional view of the blood inlet port assembly for the blood processing vessel of  FIG. 8 ; 
         FIG. 19C  is a cross-sectional view of the blood inlet port assembly interfacing with the blood processing vessel of  FIG. 8 ; 
         FIG. 19D  is a perspective view of the interior of the vane of the blood inlet port of  FIG. 19C ; 
         FIG. 19E  is a cutaway, perspective view of blood being introduced into the blood processing vessel of  FIG. 8  during an apheresis procedure; 
         FIG. 19F  is a cross-sectional view of blood being introduced into the blood processing vessel and channel of  FIG. 8  during an apheresis procedure; 
         FIG. 19G  is a cross-sectional view, looking downwardly, of blood being introduced into the blood processing vessel and channel of  FIG. 8  during an apheresis procedure; 
         FIG. 20A  is a cutaway, perspective view of the red blood cell outlet port assembly interfacing with the blood processing vessel of  FIG. 8 ; 
         FIG. 20B  is a longitudinal, cross-sectional view of the red blood cell outlet port assembly of  FIG. 20A ; 
         FIG. 20C  is a cutaway, perspective view of the red blood cell port assembly interfacing with the blood processing vessel of  FIG. 8  during rinseback at the end of an apheresis procedure; 
         FIG. 20D  is a cross-sectional view, looking downwardly, of the red blood cell outlet port assembly interfacing with the blood processing vessel in the channel of  FIG. 8  during rinseback at the end of an apheresis procedure; 
         FIG. 21A  is a cross-sectional view of the platelet outlet port assembly for the blood processing vessel of  FIG. 8 ; 
         FIG. 21B  is a plan view of the platelet outlet port assembly of  FIG. 21A  from the interior of the channel; 
         FIG. 22  is a cutaway, perspective view of the plasma port assembly for the blood processing vessel of  FIG. 8 ; 
         FIG. 23A  is a cutaway, perspective view of the control port assembly for the blood processing vessel of  FIG. 8 ; 
         FIG. 23B  is a cross-sectional view of the control port assembly interfacing with the blood processing vessel of  FIG. 8 ; 
         FIG. 24  is a perspective view of the centrifuge rotor assembly for the system of  FIG. 1 ; 
         FIG. 25A  is a longitudinal cross-sectional view of the rotor assembly of  FIG. 24 ; 
         FIG. 25B  is a top view of the rotor body of the rotor assembly of  FIG. 24 ; 
         FIG. 25C  is a top view of the rotor body of the rotor assembly of  FIG. 24  with the upper counterweight removed so as to illustrate the lower counterweight; 
         FIG. 25D  is a front view of the rotor body of  FIG. 24 ; 
         FIG. 25E  is a perspective view of the left side of the blood processing vessel aperture in the rotor body of  FIG. 24 ; 
         FIG. 25F  is a cross-sectional view of the rotor body of  FIG. 24 ; 
         FIG. 26  is a “master screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 27  is a “loading procedures screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 28  is one embodiment of a “help screen” for the loading procedures screen of  FIG. 27 ; 
         FIG. 29  is a “disposable pressure test screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 30  is a “pressure test in progress screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 31  is a “AC interconnect screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 32  is the “master screen” of  FIG. 26  which has been updated to reflect completion of the loading of the disposables; 
         FIG. 33  is a “donor/patient data screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 34  is a “weight input screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 35  is a “lab data screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 36  is the “master screen” of  FIG. 26  which as been updated to reflect completion of the donor/patient preps; 
         FIG. 37  is a first “donor/patient preps screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 38  is a second “donor/patient preps screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 39  is a “run screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 40  is one embodiment of an “alarm screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 41  is a “supplemental alarm screen” for the alarm screen of  FIG. 40 ; 
         FIG. 42  is one embodiment of a “trouble shooting screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 43  is a “final run data display screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 44  is a “rinseback screen” for the computer graphics interface of the apheresis system of  FIG. 1 ; 
         FIG. 45  is an “unload screen” for the computer graphics interface of the apheresis system of FIG.  1 ; 
     
    
    
     DETAILED DESCRIPTION 
     The present invention will be described in relation to the accompanying drawings which assist in illustrating the pertinent features thereof. Generally, all aspects of the present invention relate to improvements in a blood apheresis system, both procedural and structural. However, certain of these improvements may be applicable to other extracorporeal blood processing applications and such are within the scope of the present invention as well. 
     A blood apheresis system  2  is illustrated in FIG.  1  and allows for a continuous blood component separation process. Generally, whole blood is withdrawn from a donor/patient  4  and is provided to a blood component separation device  6  where the blood is separated into the various component types and at least one of these blood component types is removed from the device  6 . These blood components may then be provided for subsequent use by another or may undergo a therapeutic treatment and be returned to the donor/patient  4 . 
     In the blood apheresis system  2 , blood is withdrawn from the donor/patient  4  and directed through a disposable set  8  which includes an extracorporeal tubing circuit  10  and a blood processing vessel  352  and which defines a completely closed and sterile system. The disposable set  8  is mounted on the blood component separation device  6  which includes a pump/valve/sensor assembly  1000  for interfacing with the extracorporeal tubing circuit  10 , and a channel assembly  200  for interfacing with the disposable blood processing vessel  352 . 
     The channel assembly  200  includes a channel housing  204  which is rotatably interconnected with a rotatable centrifuge rotor assembly  568  which provides the centrifugal forces required to separate blood into its various blood component types by centrifugation. The blood processing vessel  352  is interfitted with the channel housing  204 . Blood thus flows from the donor/patient  4 , through the extracorporeal tubing circuit  10 , and into the rotating blood processing vessel  352 . The blood within the blood processing vessel  352  is separated into various blood component types and at least one of these blood component types (e.g., platelets, plasma, red blood cells) is continually removed from the blood processing vessel  352 . Blood components which are not being retained for collection or for therapeutic treatment (e.g., red blood cells, white blood cells, plasma) are also removed from the blood processing vessel  352  and returned to the donor/patient  4  via the extracorporeal tubing circuit  10 . 
     Operation of the blood component separation device  6  is preferably controlled by one or more processors included therein, and may advantageously comprise a plurality of embedded personal computers to accommodate interface with ever-increasing PC user facilities (e.g., CD ROM, modem, audio, networking and other capabilities). Relatedly, in order to assist the operator of the apheresis system  2  with various aspects of its operation, the blood component separation device  6  includes a graphical interface  660 . 
     Disposable Set: Extracorporeal Tubing Circuit 
     As illustrated in  FIGS. 2A-2B , blood-primable extracorporeal tubing circuit  10  comprises a cassette assembly  110  and a number of tubing assemblies  20 ,  50 ,  60 ,  80 ,  90 ,  100  interconnected therewith. Generally, blood removal/return tubing assembly  20  provides a single needle interface between a donor/patient  4  and cassette assembly  110 , and blood inlet/blood component tubing subassembly  60  provides the interface between cassette assembly  110  and blood processing vessel  352 . An anticoagulant tubing assembly  50 , platelet collection tubing assembly  80 , plasma collection tubing assembly  90 , and vent bag tubing subassembly  100  are also interconnected with cassette assembly  110 . As will be appreciated, the extracorporeal tubing circuit  10  and blood processing vessel  352  are interconnected to combinatively yield a closed disposable for a single use. 
     The blood removal/return tubing assembly  20  includes a needle subassembly  30  interconnected with blood removal tubing  22 , blood return tubing  24  and anticoagulant tubing  26  via a common manifold  28 . The needle subassembly  30  includes a needle  32  having a protective needle sleeve  34  and needle cap  36 , and interconnect tubing  38  between needle  32  and manifold  28 . Needle subassembly  30  further includes a D sleeve  40  and tubing clamp  42  positioned about the interconnect tubing  38 . Blood removal tubing  22  may be provided with a Y-connector  44  interconnected with a blood sampling subassembly  46 . 
     Cassette assembly  110  includes front and back molded plastic plates  112  and  114  (see  FIGS. 4A ,  4 B and  5 ) that are hot-welded together to define a rectangular cassette member  115  having integral fluid passageways. The cassette assembly  110  further includes a number of outwardly extending tubing loops interconnecting various integral passageways. The integral passageways are also interconnected to the various tubing assemblies. 
     Specifically, cassette assembly  110  includes a first integral anticoagulant passageway  120   a  interconnected with the anticoagulant tubing  26  of the blood removal/return tubing assembly  20 . The cassette assembly  110  further includes a second integral anticoagulant passageway  120   b  and a pump-engaging, anticoagulant tubing loop  122  between the first and second integral anticoagulant passageways  120   a ,  120   b . The second integral anticoagulant passageway  120   b  is interconnected with anticoagulant tubing assembly  50 . The anticoagulant tubing assembly  50  includes a spike drip chamber  52  connectable to an anticoagulant source, anticoagulant feed tubing  54  and a sterilizing filter  56 . During use, the anticoagulant tubing assembly  50  supplies anticoagulant to the blood removed from a donor/patient  4  to reduce or prevent any clotting in the extracorporeal tubing circuit  10 . 
     Cassette assembly  110  also includes a first integral blood inlet passageway  130   a  interconnected with blood removal tubing  22  of the blood removal/return tubing assembly  20 . The cassette assembly  110  further includes a second integral blood inlet passageway  130   b  and a pump-engaging, blood inlet tubing loop  132  between the first and second integral blood inlet passageways  130   a ,  130   b . The first integral blood inlet passageway  130   a  includes a first pressure-sensing module  134  and inlet filter  136 , and the second integral blood inlet passageway  130   b  includes a second pressure-sensing module  138 . The second integral blood inlet passageway  130   b  is interconnected with blood inlet tubing  62  of the blood inlet/blood component tubing assembly  60 . 
     Blood inlet tubing  62  is also interconnected with input port  392  of blood processing vessel  352  to provide whole blood thereto for processing, as will be described. To return separated blood components to cassette assembly  110 , the blood inlet/blood component tubing assembly  60  further includes red blood cell(RBC)/plasma outlet tubing  64 , platelet outlet tubing  66  and plasma outlet tubing  68  interconnected with corresponding outlet ports  492  and  520 ,  456 , and  420  of blood processing vessel  352 . The RBC/plasma outlet tubing  64  includes a Y-connector  70  to interconnect tubing spurs  64   a  and  64   b . The blood inlet tubing  62 , RBC/plasma outlet tubing  64 , plasma outlet tubing  68  and platelet outlet tubing  66  all pass through first and second strain relief members  72  and  74  and a braided bearing member  76  therebetween. This advantageously allows for a sealless interconnection, as taught in U.S. Pat. No. 4,425,112. As shown, multi-lumen connectors  78  can be employed in the various tubing lines. 
     Platelet outlet tubing  66  of the blood input/blood component tubing assembly  60  includes a cuvette  65  for use in the detection of red blood cells (via an interfacing RBC spillover detector provided on blood component separation device  6 ) and interconnects with a first integral platelet passageway  140   a  of cassette assembly  110 . As will be appreciated, a transparent member could alternatively be integrated into cassette assembly  110  in fluid communication with first integral platelet passageway  140   a  to interface with an RBC spillover detector. 
     The cassette assembly  110  further includes a pump-engaging, platelet tubing loop  142  interconnecting the first integral platelet passageway  140   a  and a second integral platelet passageway  140   b . The second integral platelet passageway  140   b  includes first and second spurs  144   a  and  144   b , respectively. The first spur  144   a  is interconnected with platelet collection tubing assembly  80 . 
     The platelet collection tubing assembly  80  can receive separated platelets during operation and includes platelet collector tubing  82  and platelet collection bags  84  interconnected thereto via a Y-connector  86 . Slide clamps  88  are provided on platelet collector tubing  82 . 
     The second spur  144   b  of the second integral platelet passageway  140   b  is interconnected with platelet return tubing loop  146  of the cassette assembly  110  to return separated platelets to a donor/patient  4  (e.g., upon detection of RBC spillover during platelet collection). For such purpose, platelet return tubing loop  146  is interconnected to the top of a blood return reservoir  150  integrally formed by the molded front and back plates  112 ,  114  of cassette member  115 . As will be further described, one or more types of uncollected blood components, collectively referred to as return blood, will cyclically accumulate in and be removed from reservoir  150  during use. Back plate  114  of the cassette member  115  also includes an integral frame corner  116  defining a window  118  through a corner of cassette member  115 . The frame corner  116  includes keyhole recesses  119  for receiving and orienting the platelet collector tubing  82  and platelet return tubing loop  146  in a predetermined spaced relationship within window  118 . 
     The plasma outlet tubing  68  of blood inlet/blood component tubing assembly  60  interconnects with a first integral plasma passageway  160   a  of cassette assembly  110 . Cassette assembly  110  further includes a pump-engaging, plasma tubing loop  162  interconnecting the first integral plasma passageway  160   a  and a second integral plasma passageway  160   b . The second integral plasma passageway  160   b  includes first and second spurs  164   a  and  164   b . The first spur  164   a  is interconnected to the plasma collection tubing assembly  90 . 
     The plasma collection tubing assembly  90  may be employed to collect plasma during use and includes plasma collector tubing  92  and plasma collection bag  94 . A slide clamp  96  is provided on plasma collector tubing  92 . 
     The second spur  164   b  of the second integral plasma passageway  160   b  is interconnected to a plasma return tubing loop  166  to return plasma to donor/patient  4 . For such purpose, the plasma return tubing loop  166  is interconnected to the top of the blood return reservoir  150  of the cassette assembly  110 . Again, keyhole recesses  119  in the frame  116  of cassette assembly  110  are utilized to maintain the plasma collector tubing  92  and plasma return tubing loop  166  in a predetermined spaced relationship within window  118 . 
     The RBC/plasma outlet tubing  64  of the blood inlet/blood component tubing assembly  60  is interconnected with integral RBC/plasma passageway  170  of cassette assembly  110 . The integral RBC/plasma passageway  170  includes first and second spurs  170   a  and  170   b , respectively. The first spur  170   a  is interconnected with RBC/plasma return tubing loop  172  to return separated RBC/plasma to a donor/patient  4 . For such purpose, the RBC/plasma return tubing loop  172  is interconnected to the top of blood return reservoir  150  of the cassette assembly  110 . The second spur  170   b  may be closed off as shown, or may be connected with an RBC/plasma collection tubing assembly (not shown) for collecting RBC/plasma during use. The RBC/plasma return tubing loop  172  (and RBC/plasma collector tubing if provided) is maintained in a desired orientation within window  118  by keyhole recesses  119  of the frame  116 . 
     Vent bag tubing assembly  100  is also interconnected to the top of blood return reservoir  150  of cassette assembly  110 . The vent bag tubing assembly  100  includes vent tubing  102  and a vent bag  104 . During use, sterile air present since packaging within cassette assembly  110 , and particularly within blood return reservoir  150 , cyclically passes into and back out of vent tubing  102  and vent bag  104 , as will be further described. 
     Vent bag  94  may be provided with a sterile, gas pressure-relief valve at a top end (not shown). Further, it should be noted that, as opposed to vent bag tubing assembly  100 , is additional integral passageways, integrated chambers and tubing loops could be included in cassette assembly  110  to perform the same functions as the vent bag tubing assembly  100 . 
     The platelet return tubing loop  146 , plasma return tubing loop  166  and RBC/plasma return tubing loop  172  are interconnected in a row to the top of blood return reservoir  150  immediately adjacent to forwardly projecting sidewalls  152  thereof so that the blood components returned thereby will flow down the inner walls of the blood return reservoir  150 . The blood return reservoir  150  includes an enlarged, forwardly projecting mid-section  154 , a reduced top section  156  and reduced bottom section  158  (see also  FIG. 5 ) A filter  180  is disposed in a bottom cylindrical outlet  182  of the blood return reservoir  150 . 
     A first integral blood return passageway  190   a  is interconnected to the outlet  182  of blood return reservoir  150 , and is further interconnected to a second integral blood return passageway  190   b  via a pump-engaging, blood return tubing loop  192 . The second integral blood return passageway  190   b  is interconnected with the blood return tubing  24  of the blood removal/return tubing assembly  20  to return blood to the donor/patient  4  via needle assembly  30 . 
     As illustrated in  FIGS. 2A-2B , pump-engaging tubing loops  122 ,  132 ,  142 ,  162  and  192  extend from cassette member  115  to yield an asymmetric arrangement thereby facilitating proper mounting of cassette assembly  110  on blood component separation device  6  for use. Relatedly, to further facilitate loading of cassette assembly  110 , it is noted that the back plate  114  of cassette member  115  is preferably molded to present a shallow pan-shaped back having a rim extending around the entire periphery and around window  118 , the edge of the rim being substantially coplanar with the back surface of the top, mid and bottom sections  154 ,  156 ,  158  of reservoir  150  and further defining a recessed region within which first and second pressure sensing modules  134  and  138  project. 
     Tubing assemblies  20 ,  50 ,  60 ,  80 ,  90  and  100  and cassette assembly  110  preferably comprise PVC tubing and plastic components that permit visual observation and monitoring of blood/blood components therewithin during use. Further, it should be noted that thin-walled PVC tubing (e.g., less than about 0.023 inch) may be advantageously employed for approved, sterile docking (i.e., the direct connection of two pieces of tubing) for platelet collector tubing  82  and plasma collector tubing  92  and RBC/plasma collector tubing, if provided. Thicker-walled PVC tubing (e.g., about 0.037 inch or more) is preferably utilized for pump-engaging tubing loops  132 ,  142 ,  162  and  192 . 
     Pump/Valve/Sensor Assembly 
     As noted, cassette assembly  110  is mounted upon and operatively interfaces with the pump/valve/sensor assembly  1000  of blood component separation device  6  during use. The pump/valve/sensor assembly  1000  is angled upward at about 450° (see  FIG. 1 ) and as illustrated in  FIG. 3  includes a cassette mounting plate  1010 , and a number of peristaltic pump assemblies, flow divert valve assemblies, pressure sensors and ultrasonic level sensors interconnected to face plate  6   a  of blood collection device  6  for pumping, controlling and monitoring the flow of blood/blood components through extracorporeal tubing circuit  10  during use. 
     More particularly, anticoagulant pump assembly  1020  is provided to receive anticoagulant tubing loop  122 , blood inlet pump assembly  1030  is provided to receive blood inlet tubing loop  132 , platelet pump assembly  1040  is provided to receive platelet tubing loop  142 , plasma pump assembly  1060  is provided to receive plasma tubing loop  162 , and blood return pump assembly  1090  is provided to receive blood return tubing loop  192 . Each of the peristaltic pump assemblies  1020 ,  1030 ,  1040 ,  1060 , and  1090  includes a rotor  1022 ,  1032 ,  1042 ,  1062  and  1092 , and raceway  1024 ,  1034 ,  1044 ,  1064 , and  1094  between which the corresponding tubing loop is positioned to control the passage and flow rate of the corresponding fluid. 
     Platelet divert valve assembly  1100  is provided to receive platelet collector tubing  82  and platelet return tubing loop  146 , plasma divert valve assembly  1110  is provided to receive plasma collector tubing  92  and plasma return tubing loop  166 , and RBC/plasma divert valve assembly  1120  is provided to receive RBC/plasma return tubing loop  172  and RBC/plasma collector tubing if provided. As noted above, each pair of tubing for collection or return of separated blood components is disposed in a predetermined spaced relationship within window  118  of cassette assembly  110 , thereby facilitating loading relative to the corresponding divert value assemblies. As will be further described, platelet divert valve assembly  1100 , plasma divert valve assembly  1110  and RBC/plasma divert valve assembly  1120  each include a rotary occluding member  1400   a ,  1400   b  and  1400   c  that is selectively positionable between stationary occluding walls  1104  and  1106 ,  1114  and  1116 , and  1124  and  1126 , respectively, for diverting fluid flow through one tubing of the corresponding pairs of tubings. 
     Pressure sensors  1200  and  1260  (See also  FIGS. 4A and 4B ) are provided within pump/valve/sensor assembly  1000  to operatively engage the first and second pressure-sensing modules  134  and  138  of cassette assembly  110  through openings  1120  and  1140  of cassette mounting plate  1100 . Similarly, ultrasonic level sensors  1300  and  1320  (see also  FIG. 5 ) are provided to operatively engage the blood return reservoir  150  cassette assembly  110  through openings  1160  and  1180  of cassette mounting plate  1100 . 
     As shown in  FIGS. 4A and 4B , the first and second pressure sensing modules  134 ,  138  of cassette assembly  110  each comprise a circular diaphragm  134   a ,  138   a  positioned on a raised cylindrical seat  134   b ,  138   b  formed into the back plate  114  of cassette assembly  110  with a ring-shaped, plastic diaphragm retainer  134   c ,  138   c  hot-welded to the raised cylindrical seats  134   b ,  138   b  to establish a seal therebetween. This arrangement allows the diaphragms  134   a ,  138   b  to be directly responsive to the fluid pressures within the first and second integral blood inlet passageways  130   a ,  130   b , respectively, and pressure sensors  1200 ,  1260  to directly access the diaphragms  134   a ,  138   a  through the ring-shaped retainers  134   c ,  138   c . By monitoring the diaphragms  134   a ,  138   a , the pressure sensors  1200 ,  1260  can monitor the fluid pressure within the first and second integral blood inlet passageways  130   a ,  130   b . In this regard, it should also be noted that since first integral blood inlet passageway  130   a  is in direct fluid communication with blood removal tubing  22 , and since blood removal tubing  22  and blood return tubing  24  are fluidly interconnected via the common manifold  28 , the first pressure sensing module  134  will be responsive to and first pressure sensor  1200  will actually sense the substantially common pressure in both the blood removal tubing  22  and blood return tubing  24  during operation. 
     With further regard to the first pressure sensing module  134  and first pressure sensor  1200 ,  FIG. 4A  illustrates an air coupling arrangement that allows for the sensing of positive and negative pressure changes (i.e., causing outward and inward flexure of diaphragm  134   a ). To achieve an air seal between the first pressure sensor  1200  and first pressure sensing module  134 , the sensor  1202  includes a resilient (e.g., rubber), cone-shaped engaging member  1202 . The engaging member  1202  is attached to an air channel member  1204  having a nipple-end  1206  that is received by beveled cylindrical extension  134   d  of retainer  134   c . Air channel member  1204  further includes an outer, annular projecting channel portion  1208  that contains an O-ring  1210  for sealed sliding engagement of the air channel member  1204  within housing  1212 . As illustrated, housing  1212  includes ears  1214  which interface with a floating positioning member  1216  secured to the face plate  6   a  of blood component separation device  6 . As shown, a slight clearance is provided in such interface so as to permit slight lateral movement of the engaging member  1202  and air channel member  1204  during loading of the cassette assembly  110 . A threaded end  1218  of housing  1212  extends through the face plate  6   a  of blood component separation device  6  and receives nut  1220  thereupon, while leaving a slight clearance between the nut  1220  and face plate  6   a . A spring  1222  is positioned within the housing  1212  and acts upon the annular channel portion  1208  of the air channel member  1204  to provide a spring-loaded interface between the first pressure sensor  1200  and first pressure sensing module  134 . Pressure sensing transducer  1224  engages air channel member  1204  to sense positive and negative pressure changes within sensing module  134  and provide an output signal in response thereto during use. As will be further described, the output signal of pressure transducer  1224  can be employed to control the operation of blood inlet pump  1030  and blood return pump  1090  during operation. 
     With regard to the second pressure sensing module  138  and the second pressure sensor  1260 ,  FIG. 4B  illustrates a direct contact coupling approach that allows for sensing of positive pressure changes (i.e., causing outward flexure of diaphragm  138   a ). Such contact coupling facilitates loading since the precise position of the diaphragm  138   a  relative to the second pressure sensor  1260  is not critical. As shown, second pressure sensor  1260  includes a projecting end portion  1262  that is received by the ring retainer  138   c  of sensing module  138  to directly contact diaphragm  138   a . Pressure transducer  1264  is mounted relative to the face plate  6   a  of the blood component separation device  6  via a ring  1266  that threadingly engages a portion of pressure transducer  1264  extending through the face plate  6   a . Pressure transducer  1264  provides an output signal responsive to positive pressure changes acting upon diaphragm  138   a.    
     As shown in  FIG. 5 , when cassette assembly  110  is mounted on pump/valve/sensor assembly  1000 , the ultrasonic level sensors  1300  and  1320  will be positioned to monitor the fluid level in the blood return reservoir  150 . More particularly, upper ultrasonic level sensor  1300  will be positioned in contact with the reduced top section  156  of blood return reservoir  150  and lower ultrasonic level sensor  1320  will be positioned in contact with the reduced bottom section  158  of blood return reservoir  150 . 
     Ultrasonic sensors  1300 ,  1320  each comprise pulse/echo transducers  1302 ,  1322  having a contact surface (e.g., urethane)  1304 ,  1324  that facilitates divert dry coupling (i.e., without a gel or other like coupling medium) with the blood return reservoir  150 . By way of example, ultrasonic sensors may comprise model Z-11405 transducers offered by Zevex Inc. of 5175 Greenpine Drive, Salt Lake City, Utah. Pulse/echo transducers  1302 ,  1322  are disposed within housings  1306 ,  1326  for interconnection with face plate  6   a  of the blood component separation device  6 . Housings  1306 ,  1326  include a flange  1308 ,  1328  for engaging the front of face plate  6   a , and further include a threaded end  1308 ,  1328  that extends through the face plate  6   a  to receive corresponding retaining nuts  1310 ,  1330 . A slight clearance is provided for between flanges  1308 ,  1328  and face plate  6   a . Springs  1312 ,  1332  are positioned within housings  1306 ,  1326  to act upon the corresponding pulse/echo transducers  1302 ,  1332  via E-clips  1314 ,  1334  disposed therebetween. Such spring loading of pulse/echo transducers  1302 ,  1332  yields a predetermined desired loading pressure for pulse/echo transducers  1302 ,  1332  relative to reservoir  150  during operation (e.g., at least about 5 lbs.). O-rings  1316 ,  1336  are provided intermediate pulse/echo transducers  1302 ,  1322  and housings  1306 ,  1326  to provide a sliding seal therebetween. Cables  1318 ,  1338  are interconnected to transducers  1302 ,  1322  to provide pulsing signals and return detected echo signals. 
     By gauging the presence and timing of return ultrasonic echo pulses each of sensors  1300  and  1320  can be employed to monitor the presence or absence of fluid within their corresponding echo regions within the blood return reservoir  150 , and permit blood component separation device  6  to provide pump control signals in response thereto. More particularly, when return blood accumulates up into the echo region of upper level sensor  1300  during blood processing, ultrasonic pulses emitted by upper level sensor  1300  will readily pass through the return blood and reflect off of the opposing reservoir outside sidewall/air interface to yield echo pulses having a predetermined minimum strength that are detected by upper sensor  1300  within a predetermined time period after transmission. When such echo pulses are received, upper sensor  1300  provides a signal that is used by blood component separation device  6  to initiate operation of blood return pump  1090  so as to remove accumulated return blood from the blood return reservoir  150  and transfer the same to the donor/patient  4 . 
     When blood return pump  1090  has removed return blood from the reservoir  150  down into the lower echo region, ultrasonic pulses emitted by lower level sensor  1320  will not be reflected at the opposing reservoir outside sidewall/air interface to yield echo pulses having a predetermined minimum strength for detection by lower level sensor  1320  within a predetermined time period after transmission. When this occurs, lower level sensor  1320  will fail to provide corresponding signals to blood component separation device  6 , and blood component separation device  6  will automatically stop blood return pump  1090  to stop further removal of return blood from the blood return reservoir  150 , and return blood will again begin accumulating in reservoir  150 . Thus, in the blood processing mode, blood component separation device  6  will not initiate operation of blood return pump  1090  unless and until it receives signals from upper ultrasonic sensor  1300  (the provisions of such signals indicating the presence of return blood in the upper echo region), and will thereafter automatically stop operation of blood return pump  1090  if it fails to receive signals from ultrasonic sensor  1320  (the failure to receive such signals indicating the absence of return blood in the lower echo region). 
     In an initial blood prime mode, whole blood is introduced to reservoir  150  from a donor/patient  4  through blood return tubing  24 , integral passageways  190   a ,  190   b , and tubing loop  192  via reverse operation of blood return pump  1090 . When such whole blood accumulates up into the echo region of lower level sensor  1320 , ultrasonic pulses emitted by lower level sensor  1320  will pass through the blood and reflect off of the opposing reservoir outside sidewall/air interface to yield echo pulses having a predetermined minimum strength that are detected by lower level sensor  1320  within a predetermined time period after transmission When such echo pulses are received in the blood prime mode, lower level sensor  1320  provides a signal that is used by blood component separation device  6  to turn off blood return pump  1090  and end the blood prime mode. Blood component separation device  6  then initiates the blood processing mode. 
     It is contemplated that ultrasonic sensors  1300 ,  1320  can be utilized for indicating and/or confirming the desired mounting relationship of cassette member  15  on cassette mounting plate  1010  for blood processing operations. For such purposes, if the desired mounting has been achieved, the sensors  1300 ,  1320  should be coupled to reservoir  150  so that ultrasonic pulses reflect off the interface between the inside surface of the back sidewall of reservoir  150  (i.e., the sidewall contacted by the sensors  1300 ,  1320 ) and contained air within reservoir  150 , and be received with a predetermined minimum strength within a predetermined time period after transmission. If such echo pulses are received with respect to both ultrasonic sensors  1300 ,  1320 , the desired loading relationship will be indicated and/or confirmed. Further, it is noted that ultrasonic sensors  1300 ,  1320  may be employable to sense echo pulses from the interfaces between fluid contained within the reservoir  150  and the inside surface of the outer sidewall of reservoir  150  in the upper and lower echo regions of the reservoir during operation. If such echo pulses are detectible within corresponding, predetermined time windows, corresponding signals provided by ultrasonic sensors  1300 ,  1320  can provide a further input for blood component separation device  6  to control operation of blood return pump  1090 . 
     It should be noted that in the illustrated arrangement, the upper. and lower ultrasonic sensors  1300  and  1320  advantageously operate via coupling with reduced cross-sectional portions  156  and  158  of reservoir  150 . The reduced upper and lower reservoir portions  154 ,  158 , accommodate reliable detection of echo pulses when fluid is present in the upper and lower echo regions, and the enlarged mid-portion  158  provides satisfactory return blood holding capabilities. 
       FIG. 6  shows the components of each of the platelet divert valve subassembly  1100 , plasma divert valve subassembly  1100  and RBC/plasma divert valve subassembly  1120 . Each subassembly includes a rotary occluder member  1400  having a headed shaft member  1402  and barrel sleeve  1404  positioned thereupon and rotatable relative thereto. The subassembly further comprises a main valve shaft  1406  positioned within a valve body  1408  that is secured to face plate  6   a  of blood component separation device  6 . An O-ring  1410  is provided in a recess on the main valve shaft  1406  to provide a sliding seal between main valve shaft  1406  and extensions  1412  of main valve body  1408 . The main valve shaft  1406  is driven by a motor  1414  mounted on mount plate  1416  that in turn is mounted to and set off from face plate  6   a  by standoff legs  1418 . 
     For positioning rotary occluder member  1400  for occlusion relative to one of the co-acting walls (e.g.  1104  or  1106  of the plasma divert valve subassembly  1100 ) or for loading/removal of the cassette assembly  110  on the blood component separation device  6 , each divert valve subassembly comprises three optical through-beam sensors  1420  (two shown) interconnected to standoff legs  1418  via support layer  1419 , and an optical interrupter member  1422  interconnected to the main valve shaft  1406 . Each through-beam sensor  1420  is of a U-shape configuration with a radiation source and radiation receiver disposed on opposing legs. The optical interrupter member  1422  has an inverted cup configuration with its sidewalls interposed and rotatable between the opposing legs of sensors  1420 . The optical interrupter member  1422  includes a single window  1424  therethrough. As will be appreciated, the position of the rotary occluder member  1400  relative to the window  1424  of the optical interrupter  1422  is known, such that when the optical window  1424  passes between the opposing radiation source/receiver for a given optical sensor  1420 , the optical sensor  1420  will provide a signal in response to the through-beam (indicating the position of the rotary occluder member  1400 ), and the signal is employed to control the operation of motor  1414  to dispose rotary occluder member  1400  in the desired position. To provide/route such signals, the support layer  1419  may advantageously comprise a printed circuit board. Optical sensors  1420  are preferably positioned slightly “upstream” of predetermined stop regions for occlusion or cassette loading so that motor  1414  will be able to dynamically slow down and position rotary occluder member  1400  within such regions as desired. To insure the desired positioning for occlusion, however, stops  1426  are provided on main valve shaft  1406  to co-act with cross-pin  1428  interconnected to main valve shaft  1406  to insure stop positioning of rotary occluder member  1400  relative to the desired occluding wall. 
     Each of the occluding walls  1104  and  1106 ,  1114  and  1116 , and  1124  and  1126 , are provided with arcuate recesses (not shown) for receiving the rotatable barrel sleeve on  1404  of rotary occluder members  1400   a ,  1400   b  and  1400   c . By way of example, such arcuate recesses may have an arc length of 20° and provide a tolerance range for positioning the rotary occluder members  1400   a ,  1400   b ,  1400   c  to achieve the desired tubing occlusion. As illustrated in  FIG. 3 , occluding wall  1106  may be provided with a resilient pad to best accommodate the use of approved, sterile-docking tubing for platelet collector tubing  82 . Further, and as noted above, sterile-docking tubing may be advantageously employed for plasma collector tubing  92  and, if provided, RBC/plasma collector tubing (not shown), and corresponding resilient pads (not shown) may be provided on occluding walls  1114  and  1124 . In this regard, given the thinness and relatively high-spring rate of sterile-docking tubing, the use of resilient pads in connection therewith increases the wearability of the sterile docking tubing. 
     In order to establish an initial predetermined set position of the cassette assembly  110  relative to the pump/valve/sensor assembly  1000 , the cassette assembly  110  includes downwardly extending corner positioning tabs  15  and top and bottom edge lips  17  that engage corresponding lower channel projections  1102   a  on cassette mounting plate  1010  and upper channel projections  1102   b  on a pivotable spring-loaded interlock member  1104  that extends across the top edge of cassette mounting plate  1010 . The interlock member  1104  is spring-loaded to positively engage cassette assembly  110  upon loading via a spring positioned within housing  1106 , and is provided with a tab  1108  for pivotable movement during cassette loading against the spring loading pressure. Preferably, interlock member  1104  is disposed relative to the raceway  1094  of return pump assembly  1090 , such that when cassette assembly  110  is fully loaded for operation on blood component separation device  6 , raceway  1094  will physically restrict interlock member  1104  from being pivoted, thereby advantageously restricting removal and/or movement of cassette assembly  110  during use. 
     After cassette assembly  110  has been secured on the cassette mounting plate  1010 , a loading assembly  1500  retracts the cassette mounting plate  1010  towards face plate  6   a  of the blood component separation device  6  to establish the above-noted, fully-loaded pump, valve and sensor relationships. As illustrated in  FIG. 7 , loading assembly  1500  includes two posts  1502  upon which cassette mounting plate  1010  is supportably interconnected. The posts  1502  extend through the face plate  6   a  of blood collection device  6   a  and are interconnected to a cross-connect member  1504 . A drive nut  1506  is secured to cross-connect member  1504  and engages a drive screw  1508 . The drive screw  1508  is in turn rotatably interconnected to a drive motor  1510  via coupling  1512 , the drive motor  1510  being mounted on a platform  1514  which is supportively interconnected to face plate  6   a  via standoff legs  1516 . The drive motor  1510  operates to turn drive screw  1508  so as to cause cross-connect member  1504  and posts  1502  to selectively move cassette mounting plate  1010  perpendicularly towards face plate  6   a  during loading procedures and perpendicularly away from face plate  6   a  for unloading of the cassette assembly  110 . 
     To establish the desired position of cassette mounting plate  1010 , U-shaped optical through-beam sensors  1520   a  and  1520   b  are mounted on post bearing holders  1522  and an optical occluder member  1524  having a window  1526  is interconnected to the cross-connect member  1504 . Each of the U-shaped optical sensors  1520   a ,  1520   b  includes a radiation source and radiation receiver positioned on opposing extending legs, and the optical occluder member  1524  extends between such legs. Since the relative positions between cassette mounting plate  1010  and optical sensors  1520   a ,  1520   b  are known, by detecting the passage of radiation through window  1526  using optical sensors  1520 , and providing a signal responsive thereto,the position of cassette mounting plate  1010  for loading and unloading can be automatically established. For example, when a through-beam is received by optical sensor  1520   b , a signal will be provided to stop motor  1510  in a position wherein cassette assembly  110  will be fully loaded on the pump/valve/sensor assembly  1000  for operation. 
     To confirm such loaded condition, first and second pressure sensors  1200  and  1260  and upper and lower ultrasonic sensors  1300  and  1320  may be employed. For example, predetermined minimum pressure values can be established and actual pressures measured for each of the first and second pressure sensors  1200  and  1260  to confirm the desired loading of cassette assembly  110 . Further, and of particular interest, ultrasonic sensors  1300  and  1320  can be advantageously employed to confirm the desired loading, since upon proper coupling to reservoir  150  echo pulses should be reflected off of the internal sidewall/air interface with a predetermined minimum strength within a predetermined time period as noted above. 
     It should be noted that drive motor  1510  preferably includes a number of reduction gears with the last gear being operatively associated with a slip clutch plate to limit the maximum amount of force that may be applied by cassette mounting plate  1010  (e.g., to an object between cassette mounting plate  1010  and face plate  6   a ). Relatedly, it is preferable to include control capabilities wherein during a load cycle if the window  1526  of optical occluder  1524  has not moved from its position within the first optical pass through sensor  1520   a  to a position within the second optical pass through sensor  1520   b  within a predetermined time period, drive motor  1510  will automatically either stop or reverse operations. 
     To summarize the loading process, loading assembly  1500  initially disposes cassette mounting plate  1010  in an extended position. With the cassette mounting plate  1010  in such extended position, interlock member  1104  is pivoted away from cassette mounting plate  1010  and cassette assembly  110  is positioned on cassette mounting plate  1010  with bottom edge lips  17  of cassette assembly  110  being received by lower channel projections  1102   a  of cassette mounting plate  1010  and, upon return pivotal movement of interlock member  1104 , top edge lips  17  of cassette assembly  110  being engaged by upper channel projections  1102   b  on interlock member  1104 . Loading assembly  1500  is then operated to retract cassette mounting plate  1010  from its extended position to a retracted position, wherein tubing loops  122 ,  132 ,  162 ,  142 ,  192  of cassette assembly  110  are automatically positioned within the corresponding peristaltic pump assemblies  1020 ,  1030 ,  1060 ,  1040  and  1090 . For such purposes, the rotors of each of the peristaltic pump assemblies are also operated to achieve loaded positioning of the corresponding tubing loops. Further, it should be noted that for loading purposes, the rotary occluder members  1400   a ,  1400   b  and  1400   c  of the divert valve assemblies  1100 ,  1110  and  1120  are each positioned in an intermediate position so as to permit the corresponding sets of tubing to be positioned on each side thereof. 
     Upon retraction of the cassette mounting plate  1010 , spring-loaded, ultrasonic sensors  1300  and  1320  will automatically be coupled to reservoir  150  and first and second pressure sensors  1200  and  1260  will automatically couple to first and second pressure sensing modules  134  and  138  of cassette assembly  110 . In this fully-loaded, retracted position, the cassette assembly  110  will be restricted from movement or removal by the above-noted physical restriction to pivotal movement of interlock member  1104  provided by raceway  1094  of return pump assembly  1090 . 
     It is also noted that during loading of cassette assembly  110  on the blood component separation device  6 , cuvette  65  is positioned within an RBC spillover detector  1600  (e.g., an optical sensor for detecting the presence of any red blood cells in the separated platelet fluid stream and providing a signal. response thereto) provided on the face plate  6   a . Similarly, a portion of anticoagulant tubing  54  is positioned within an AC sensor  1700  (e.g., an ultrasonic sensor for confirming the presence of anticoagulant and providing a signal in the absence thereof) also provided in face plate  6   a.    
     To unload cassette assembly  110  after use, the occluding members  1400   a ,  1400   b  and  1400   c  of each divert value assembly are again positioned in an intermediate position between the corresponding occluding walls and loading assembly  1500  is operated to move cassette mounting plate  1010  from its retracted position to its extended position. Contemporaneously, the rotors of the various peristaltic pump assemblies are operated to permit the corresponding tubing loops to exit the same. In the extended position, the interlock member  1104  is pivoted out of engagement with cassette assembly  110  and cassette assembly  110  is removed and disposed of. 
     Operation of Extracorporeal Tubing Circuit and Pump/Valve/Sensor Assembly 
     In an initial blood prime mode of operation, blood return pump  1090  is operated in reverse to transfer whole blood through blood removal/return tubing assembly  20 , integral blood return passageway  190 , blood return tubing loop  192  and into reservoir  150 . Contemporaneously and/or prior to the reverse operation of blood return pump  1090 , anticoagulant peristaltic pump  1020  is operated to prime and otherwise provide anticoagulant from anticoagulant tubing assembly  50 , through anticoagulant integral passageway  120 , and into blood removal tubing  22  and blood return tubing  24  via manifold  28 . When lower level ultrasonic sensor  1320  senses the presence of the whole blood in reservoir  150  a signal is provided and blood component separation device  6  stops blood return peristaltic pump  1090 . As will be further discussed, during the blood prime mode blood inlet pump  1030  is also operated to transfer blood into blood inlet integral passageway  130 , through blood inlet tubing loop  132  and into blood inlet/blood component tubing assembly  60  to prime the blood processing vessel  352 . 
     During the blood prime mode, vent bag assembly  100  receives air from reservoir  150 . Relatedly, the occluding members  1400   a ,  1400   b ,  1400   c  of divert assemblies  1100 ,  1110 ,  1120  are each preferably positioned to divert flow to the reservoir  150 . It should also be noted that to facilitate blood priming, the cassette assembly  110  is angled upward at about 45° in its loaded position, and the integral passageways of cassette member  115  are disposed so that all blood and blood component inlet paths provide for a bottom-to-top plug flow. 
     In the blood processing mode, the blood inlet peristaltic pump  1030 , platelet peristaltic pump  1040  and plasma peristaltic pump  1060  are operated continuously, and the occluding members  1400   a ,  1400   b ,  1400   c  are positioned for collection or return of corresponding blood components, as desired. During a blood removal submode, blood return peristaltic pump  1090  is not operated so that whole blood will pass into blood removal/return tubing assembly  20  and transferred to processing vessel  352  via the cassette assembly  110  and blood inlet/blood component tubing assembly  60 . In the blood removal submode, uncollected blood components are transferred from the processing vessel  352  to cassette assembly  110 , and uncollected components are passed into and accumulate in reservoir  150  up to a predetermined level at which upper level ultrasonic sensor  1300  provides signals used by blood component separation device  6  to end the blood removal submode and initiate a blood return submode. More particularly, blood return submode is initiated by forward operation of blood return peristaltic pump  1090 . In this regard, it should be appreciated that in the blood return submode the volume transfer rate of return blood through blood return tubing loop  192  utilizing blood return peristaltic pump  1090  is established by blood component separation device  6 , according to a predetermined protocol, to be greater than the volume transfer rate through blood inlet tubing loop  132  utilizing blood inlet peristaltic pump  1030 . As such, the accumulated blood in reservoir  150  is transferred into the blood return tubing of blood removal/return tubing assembly  20  and back into the donor/patient  4 . During the blood processing mode, when the accumulated return blood in reservoir  150  is removed down to a predetermined level, lower level ultrasonic sensor  1320  will fail to provide signals to blood component separation device  6 , whereupon blood component separation device  6  will automatically stop blood return peristaltic pump  1090  to end the blood return submode. This automatically serves to reinitiate the blood removal submode since blood inlet peristaltic pump  1030  continuously operates. 
     During the blood processing mode, pressure sensor  1200  senses negative/positive pressure changes within the blood removal tubing  22  blood return tubing  26 , via first integral blood inlet passageway  130   a . Such monitored pressure changes are communicated to blood component separation device  6  which in turn controls blood inlet pump  1030  and return pump  1090  so as to maintain fluid pressures within predetermined ranges during the blood removal and the blood return submodes. Specifically during the blood removal submode, if a negative pressure is sensed that exceeds (i.e., is less than) a predetermined negative limit value, then blood component separation device  6  will slow down operation of blood inlet pump  1030  until the sensed negative pressure is back within an acceptable range. During the blood return submode, if a positive pressure is sensed that exceeds (i.e., is greater than) a predetermined positive limit value, then blood component separation device  6  will slow down operation of blood return pump  1090  until the sensed positive pressure is back within an acceptable range. 
     Pressure sensor  1260  monitors the positive pressure within the second integral blood inlet passageway  130   b  and blood inlet tubing  62 . If such sensed positive pressure exceeds a predetermined maximum value, blood component separation device  6  will initiate appropriate responsive action, including, for example, slowing or stoppage of the centrifuge and peristaltic pumps. 
     During the blood processing mode, blood component separation device  6  controls the operation of anticoagulant pump  1020  according to a predetermined protocol and responsive to signals provided by AC sensor  1700  (e.g., indicating a depleted anticoagulant source). Also, blood component separation device  6  also controls the operation of divert assemblies  1100 ,  1110 ,  1120  according to predetermined instructions and further pursuant to any detect signals provided by RBC spillover detector  1600 . In the latter regard, if an RBC spillover in the separated platelet stream is detected, blood component separation device  6  will automatically cause occluder member  1400   a  to divert the separated platelet stream to the return reservoir  150  until the RBC spillover has cleared, thereby keeping red blood cells from undesirably passing into platelet collector tubing assembly  80 . 
     In normal operation, whole blood will pass through needle assembly  30 , blood removal tubing  22 , cassette assembly  110  and blood inlet tubing  62  to processing vessel  352 . As will be further described in detail, the whole blood will then be separated in vessel  352 . A platelet stream will pass out of port  420  of the vessel, through platelet tubing  66 , back through cassette assembly  110 , and will then be either collected in collector assembly  80  or diverted to reservoir  150 . Similarly, separated plasma will exist vessel  352  through port  456  to plasma tubing  68  back through cassette assembly  110 , and will then either be collected in platelet tubing assembly  90  or diverted to reservoir  150 . Further, red blood cells and plasma (and potentially white blood cells) will pass through ports  492  and  520  of vessel  352  through RBC/plasma tubing  64 , through cassette assembly  110  and into reservoir  150 . In this regard, it is contemplated that second spur  170   b  of integral passageway  170  may be connected to a separate RBC/plasma collector tubing assembly (not shown) and RBC/plasma divert valve assembly  1120  could be operated for the collection of RBC/plasma. 
     As noted above, when uncollected platelets, plasma, and RBC/plasma (and potentially white blood cells) have accumulated in reservoir  150  up to upper ultrasonic level sensor  1300 , operation of return peristaltic pump  1090  will be initiated to remove the noted components from reservoir  150  and transfer the same back to the donor/patient  4  via the return tubing  24  and needle assembly  20  When the fluid level in the reservoir  150  drops down to the level of the lower ultrasonic level sensor  1320 , the return peristaltic pump  1090  will automatically turn off reinitating the blood removal submode. The cycle between blood removal and blood return submodes will then continue until a predetermined amount of platelets or other collected blood components have been harvested. 
     In one embodiment, reservoir  150  and upper and lower ultrasonic sensors  1300  and  1320  are provided so that, during the blood processing mode, approximately 50 milliliters of return blood will be removed from reservoir  150  during each blood return submode and accumulated during each blood removal submode. Relatedly, in such embodiment, lower and upper level triggering by ultrasonic sensors  1300  and  1320  occurs at fluid volumes of about 15 milliliters and 65 milliliters, respectively, within reservoir  150 . For such embodiment, it is also believed desirable to provide for a volume transfer operating rate range of about 30 to 300 milliliters/minute through blood return tubing loop  192  utilizing return pump  1090 , and a volume transfer operating rate range of about 20 to 140 milliliters/minute through blood inlet tubing loop  132  utilizing inlet pump  1030 . Additionally, for such embodiment a negative pressure limit of about −250 mmHg and positive pressure limit of about 350 mmHg is believed appropriate for controlling the speed of inlet pump  1030  and return pump  1090 , respectively, in response to the pressures sensed in first pressure sensing module  134 . A positive pressure limit of about 1350 mmHg within second sensing module  138  is believed appropriate for triggering slow-down or stoppage of the centrifuge and pumps. 
     Channel Housing 
     The channel assembly  200  is illustrated in  FIGS. 8-23B  and includes a channel housing  204  which is disposed on the rotatable centrifuge rotor assembly  568  ( FIGS. 1 and 24 ) and which receives a disposable blood processing vessel  352 . Referring more specifically to  FIGS. 8-15 , the channel housing  204  has a generally cylindrically-shaped perimeter  206  with a diameter of preferably no more than about 10 inches to achieve a desired size for the blood component separation device  6  (e.g., to enhance its portability). An opening  328  extends longitudinally through the channel housing  204  and contains an axis  324  about which the channel housing  204  rotates. The channel housing  204  may be formed from materials such as delrin, polycarbonate, or cast aluminum and may include various cut-outs or additions to achieve weight reductions and/or rotational balance. 
     The primary function of the channel housing  204  is to provide a mounting for the blood processing vessel  352  such that the blood may be separated into the blood component types in a desired manner. In this regard, the channel housing  204  includes a generally concave channel  208  in which the blood processing vessel  352  is positioned. The channel  208  is principally defined by an inner channel wall  212 , an outer channel wall  216  which is radially spaced from the inner channel wall  212 , and a channel base  220  which is positioned therebetween. The channel  208  also extends from a first end  284  generally curvilinearly about a rotational axis  324  of the channel housing  204  to a second end  288  which overlaps with the first end  284  such that a continuous flow path is provided about the rotational axis  324 . That is, the angular disposition between the first end  284  of the channel  208  and the second end  288  of the channel  208  is greater than 360° and up to about 390°, and in the illustrated embodiment is about 380°. Referring to  FIG. 15 , this angular disposition is measured by the angle β, along a constant radius arc, between a first reference ray  336  which extends from the rotational axis  324  to the first end  284 , and a second reference ray  340  which extends from the rotational axis  324  to the second end  288  of the channel  208 . 
     The blood processing channel vessel  352  is disposed within the channel  208 . Generally, the channel  208  desirably allows blood to be provided to the blood processing vessel  352  during rotation of the channel housing  204 , to be separated into its various blood component types by centrifugation, and to have various blood component types removed from the blood processing vessel  352  during rotation of the channel housing  204 . For instance, the channel  208  is configured to allow for the use of high packing factors (e.g., generally a value reflective of how “tightly packed” the red blood cells and other blood component types are during centrifugation and as will be discussed in more detail below). Moreover, the channel  208  also desirably interacts with the blood processing vessel  352  during centrifugation (e.g., by retaining the blood processing vessel  352  in the channel  208  and by maintaining a desired contour of the blood processing vessel  352 ). In addition, the channel  208  allows for a blood priming of the blood processing vessel  352  (i.e., using blood as the first liquid which is provided to the blood processing vessel  352  in an apheresis procedure). 
     The above-identified attributes of the channel  208  are provided primarily by its configuration. In this regard, the channel housing  204  includes a blood inlet slot  224  which is generally concave and which intersects the channel  208  at its inner channel wall  212  in substantially perpendicular fashion (e.g., the blood inlet slot  224  interfaces with the inner channel wall  212 ). A blood inlet port assembly  388  to the interior of the blood processing vessel  352  is disposed in this blood inlet slot  224  such that blood from the donor/patient  4  may be provided to the blood processing vessel  352  when in the channel  208 . In order to retain a substantially continuous surface along the inner channel wall  212  during an apheresis procedure and with the blood processing vessel  352  being pressurized, namely by reducing the potential for the blood inlet port assembly  388  deflecting radially inwardly within the blood inlet slot  224 , a recess  228  is disposed on the inner channel wall  212  and contains the end of the blood inlet slot  224  (e.g., FIG.  14 A). This recess  228  receives a shield  408  which is disposed about the blood inlet port assembly  388  on the exterior surface of the blood processing vessel  352  as will be discussed in more detail below. 
     As illustrated in  FIGS. 8-9 , an RBC dam  232  of the channel  208  is disposed in a clockwise direction from the blood inlet slot  224  and whose function is to preclude RBCs and other large cells such as WBCs from flowing in a clockwise direction beyond the RBC dam  232 . Generally, the surface of the RBC dam  232  which interfaces with the fluid containing volume of the blood processing vessel  352  may be defined as a substantially planar surface or as an edge adjacent the collect well  226 . At least in that portion of the channel  208  between the blood inlet port  224  and the RBC dam  232 , blood is separated into a plurality of layers of blood component types including, from the radially outermost layer to the radially innermost layer, red blood cells (“RBCs”), white blood cells (“WBCs”), platelets, and plasma. The majority of the separated RBCs are removed from the channel  208  through an RBC outlet port assembly  516  which is disposed in an RBC outlet slot  272  associated with the channel  208 , although at least some RBCs may be removed from the channel  208  through a control port assembly  488  which is disposed in a control port slot  264  associated with the channel  208 . 
     The RBC outlet port slot  272  is disposed in a counterclockwise direction from the blood inlet slot  224 , is generally concave, and intersects the channel  208  at its inner channel wall  212  in substantially perpendicular fashion (e.g., the RBC outlet slot  272  interfaces with the inner channel wall  212 ). An RBC outlet port assembly  516  to the interior of the blood processing vessel  352  is disposed in this RBC outlet slot  272  such that separated RBCs from the apheresis procedure may be continually removed from the blood processing vessel  352  when in the channel  208  (e.g., during rotation of the channel housing  204 ). In order to retain a substantially continuous surface along the inner channel wall  212  during an apheresis procedure and with the blood processing vessel  352  being pressurized, namely by reducing the potential for the RBC outlet port assembly  516  deflecting radially inwardly within the RBC outlet slat  272 , a recess  276  is disposed on the inner channel wall  212  and contains the end of the RBC outlet slot  272  (e.g.,  FIGS. 14A ,  14 B). This recess  276  receives a shield  538  which is disposed about the RBC outlet port assembly  516  on the exterior surface of the blood processing vessel  352  as will be discussed in more detail below. 
     The control port slot  264  is disposed in a counterclockwise direction from the RBC outlet slot  272 , is generally concave, and intersects the channel  208  at its inner channel wall  212  in substantially perpendicular fashion (e.g., the control port slot  264  interfaces with the inner channel wall  212 ). A control port assembly  488  to the interior of the blood processing vessel  352  is disposed in the control port slot  264  (e.g., FIGS.  14 A and C). In order to retain a substantially continuous surface along the inner channel wall  212  during an apheresis procedure and with the blood processing vessel  352  being pressurized, namely by reducing the potential for the control port assembly  488  deflecting radially inwardly within the control port slot  264 , a recess  268  is disposed on the inner channel wall  212  and contains the end of the control port slot  264 . This recess  268  receives a shield  508  which is disposed about the control port assembly  488  on the exterior surface of the blood processing vessel  352  as will be discussed in more detail below. 
     The portion of the channel  208  extending between the control port slot  264  and the RBC dam  232  may be characterized as the first stage  312  of the channel  208 . The first stage  312  is configured to remove primarily RBCs from the channel  208  by utilizing a reverse flow in relation to the flow of platelet-rich plasma through the channel  208  which is in a clockwise direction. In this regard, the outer channel wall  216  extends along a curvilinear path from the RBC dam  232  to the blood inlet slot  224  generally progressing outwardly away from the rotational axis  324  of the channel housing  204 . That is, the radial disposition of the outer channel wall  216  at the RBC dam  232  is less than the radial disposition of the outer channel wall  216  at the blood inlet slot  224 . The portion of the RBC outlet slot  272  interfacing with the channel  208  is also disposed more radially outwardly than the portion of the blood inlet slot  224  which interfaces with the channel  208 . 
     In the first stage  312 , blood is again separated into a plurality of layers of blood component types including, from the radially outermost layer to the radially innermost layer, red blood cells (“RBCs”), white blood cells (“WBCs”), platelets, and plasma. As such, the RBCs sediment against the outer channel wall  216  in the first stage  312 . By configuring the RBC dam  232  such that it is a section of the channel  210  which extends further inwardly toward the rotational axis  324  of the channel housing  204 , this allows the RBC dam  232  to retain separated RBCs and other large cells as noted within the first stage  312 . That is, the RBC dam  232  functions to preclude RBCs from flowing in a clockwise direction beyond the RBC dam  232 . 
     Separated RBCs and other large cells as noted are removed from the first stage  312  utilizing the above-noted configuration of the outer channel wall  216  which induces the RBCs and other large cells as noted to flow in a counterclockwise direction (e.g., generally opposite to the flow of blood through the first stage  312 ). Specifically, separated RBCs and other large cells as noted flow through the first stage  312  along the outer channel wall  216 , past the blood inlet slot  224  and the corresponding blood inlet port assembly  388  on the blood processing vessel  352 , and to an RBC outlet slot  272 . In order to reduce the potential for counterclockwise flows other than separated RBCs being provided to the control port assembly  488  disposed in the control port slot  264  (e.g., such that there is a sharp demarcation or interface between RBCs and plasma proximate the control port slot  264  as will be discussed in more detail below), a control port dam  280  of the channel  208  is disposed between the blood inlet slot  224  and the RBC outlet slot  272 . That is, preferably no WBCs nor any portion of a buffy coat, disposed radially adjacent to the separated RBCs, is allowed to flow beyond the control port dam  280  and to the control port slot  264 . The “buffy coat” includes primarily WBCs, lymphocytes, and the radially outwardmost portion of the platelet layer. As such, substantially only the separated RBCs and plasma are removed from the channel  208  via the RBC control slot  264  to maintain interface control as noted. 
     The flow of RBCs to the control port assembly  488  is typically relatively small. Nonetheless, the ability for this flow is highly desired in that the control port assembly  488  functions in combination with the RBC outlet port assembly  516  to automatically control the radial position of an interface between separated RBCs and the “buffy coat” in relation to the RBC dam  232  by controlling the radial position of an interface between separated RBCs and plasma in relation to the control port assembly  488 . The control port assembly  488  and RBC outlet port assembly  516  automatically function to maintain the location of the interface between the separated RBCs and the buffy coat at a desired radial location within the channel  208  which is typically adjacent the RBC dam  232  such that there is no spillover of RBCs or the buffy coat beyond the RBC dam  232 . This function is provided by removing separated RBCs from the channel  208  at a rate which reduces the potential for RBCs and the other large cells as noted flowing beyond the RBC dam  232  and contaminating the platelet collection. 
     Separated platelets, which are disposed radially inwardly of the RBC layer and more specifically radially inwardly of the buffy coat, flow beyond the RBC dam  232  with the plasma (e.g., via platelet-rich plasma) in a clockwise direction. A generally funnel-shaped platelet collect well  236  is disposed in a clockwise direction from the RBC dam  232  and is used to remove platelets from the channel  208  in the platelet-rich plasma. The configuration of the platelet collect well  236  is defined by only part of the outer channel wall  216 . The portion of the platelet collect well  236  defined by the configuration of the outer channel wall  216  includes a lower face  240 , a left side face  244 , and a right side face  248 . These faces  240 ,  244 ,  248  are each substantially planar surfaces and taper generally outwardly relative to the rotational axis  324  and inwardly toward a central region of the platelet collect well  236 . is. The remainder of the platelet collect well  236  is defined by the blood processing vessel  352  when loaded in the channel  208 , namely a generally triangularly-shaped  428  which is disposed above the platelet outlet port assembly  416  to the interior of the blood processing vessel  352  and discussed in more detail below. A platelet support recess  249  extends further radially outwardly from those portions of the platelet collect well  236  defined by the configuration of the outer channel wall  216  and primarily receives the support  428  associated with the platelet collect port assembly  416 . Generally, the upper portion of the support  428  is disposed below and engages an upper lip  252  of the platelet support recess  249 , while portions of the fourth face  444  of the support  428  are seated against the two displaced shoulders  252 . This positions the support  428  when the blood processing vessel  352  is pressurized to direct platelets toward the platelet collect port assembly  416 . 
     The outer channel wall  216  is further configured to receive the platelet collect tube  424 . An upper platelet collect tube recess  254  and a lower platelet collect tube recess  255  are disposed yet further radially outwardly from the platelet support recess  249  to provide this function. As such, the platelet collect tube  424  may extend radially outwardly from the outer sidewall  376  of the blood processing vessel  352 , extend upwardly through the lower platelet collect tube recess  255  and the upper platelet collect tube recess  254  behind or radially outwardly from the support  428 , and extend above the channel housing  204 . 
     Platelet-poor plasma continues to flow in a clockwise direction through the channel  208  after the platelet collect well  236  and may be removed from the channel  208 . In this regard, the channel  208  further includes a generally concave plasma outlet slot  256  which is disposed proximate the second end  288  of the channel  208  and intersects the channel  208  at its inner channel wall  212  in substantially perpendicular fashion (e.g., the plasma outlet slot  256  interfaces with the inner channel wall  212 ). A plasma outlet port assembly  452  to the interior of the blood processing vessel  352  is disposed in this plasma outlet slot  256  such that plasma may be continually removed from the blood processing vessel  352  during an apheresis procedure (e.g., during continued rotation of the channel housing  204 ). This plasma may be collected and/or returned to the donor/patient  4 . In order to increase the number of platelets that are separated and removed from the vessel  352  in a given apheresis procedure, the configuration of the channel  208  between the platelet collect well  236  and the plasma outlet slot  256  may be such that platelets which separate from plasma in this portion of the channel  208  actually flow in a counterclockwise direction back towards the platelet collect well  236  for removal from the channel  208 . This may be provided be configuring the outer channel wall  216  such that it extends generally curvilinearly about the rotational axis  324  from the platelet collect well  236  to the plasma outlet slot  256  progressing generally inwardly toward the rotational axis  324  of the channel housing  204 . Consequently, the portion of the channel  208  including the platelet collect well  236  and extending from the platelet collect well  236  to the second end  288  may be referred to as a second stage  316  of the channel  208 . 
     The channel  208  is also configured to provide platelet-poor plasma to the control port slot  264  and thus to the control port assembly  488  in order to assist in automatically controlling the interface between the RBCs and the buffy coat in relation to the RBC dam  232 . In this regard, the first end  284  of the channel  208  is interconnected with the second end  288  of the channel  208  by a connector slot  260 . With the first connector  360  and second connector  368  of the blood processing vessel  352  being joined, they may be collectively disposed in this connector slot  260 . As such, a continuous flowpath is provided within the blood processing vessel  352  and, for purposes of the automatic interface control feature, RBCs may flow to the control port slot  264  in a counterclockwise direction and plasma may flow to the control port slot  264  in a clockwise direction. The portion of the channel  208  extending from the first end  284  to the control port slot  264  may be referred to as a third stage  320  of the channel  208 . 
     As noted above, the configuration of the channel  208  is desirable/important in a number of respects. As such, the dimensions of one embodiment of the channel  208  are provided herein and which may contribute to the functions of the channel  208  discussed below. The dimensions for one embodiment of the channel  208  are identified on FIG.  9 B. All radius and thicknesses, etc., are expressed in inches. 
     One of the desired attributes of the channel  208  is that it facilitates the loading the of blood processing vessel  352  therein. This is provided by configuring the channel  208  to include a chamfer  210  on both sides of the channel  208  along the entire extent thereof. Generally, the chamfer  210  extends downwardly and inwardly toward a central portion of the channel  208  as illustrated, for instance, in  FIGS. 12-13 . In embodiment, the angle of this chamfer  210  ranges from about 30° to about 60° relative to horizontal, and preferably is about 45°. Moreover, the configuration of the channel  208  retains the blood processing vessel  352  within the channel  208  throughout the apheresis procedure. This is particularly relevant in that the channel housing  254  is preferably rotated a relatively high rotational velocities, such as about 3,000 RPM. 
     Another desirable attribute of the channel  208  is that it provides a self-retaining function for the blood processing vessel  352 . The configuration of the channel  208  in at least the first stage  312 , and preferably in the region of the platelet collect well  236  and in the region of the RBC dam  232  as well, is configured such that the upper portion of the channel  208  includes a restriction (e.g., such that the upper part of the channel  208  in this region has a reduced width in relation to a lower portion thereof). Although this configuration could also be utilized in the portion of the second stage  316  disposed between the platelet collect well  236  and the plasma outlet slot  256 , in the illustrated embodiment the width or sedimentation distance of the channel  208  in this region is less than the width or sedimentation distance of the channel  208  throughout the entire first stage  312 . This use of a “reduced width” can itself sufficiently retain the blood processing vessel  352  in the channel  208  in the “reduced-width” portion of the second stage  316  such that the inner channel wall  212  and outer channel wall  216  in this portion of the second stage  316  may be generally planar and vertically extending surfaces. 
     In the illustrated embodiment and as best illustrated in  FIG. 12 , the noted “restriction” in the channel  208  is provided by configuring the outer channel wall  216  with a generally C-shaped profile. In this portion of the channel  208 , the channel  208  includes an upper channel section  292  having a first width, a mid-channel section  300  having a second width greater than the first width, and a lower channel section  304  having a width less than that of the mid-channel section  300  and which is typically equal to that of the upper channel section  292 . This profile is provided by an upper lip  296  which extends radially inwardly from the outer channel wall  216  toward, but displaced from, the inner channel wall  212 , and by a lower lip  308  which extend ends radially inwardly from the outer channel wall  216  toward, but displaced from, the inner channel wall  212 . This lower lip  308  actually defines a portion of the channel base  220  but does extend entirely from the outer channel wall  216  to the inner channel wall  212  such that it defines a notch  218 . 
     When the blood processing vessel  352  is loaded into the channel  208 , the fluid-containing volume of the coinciding portion of the blood processing vessel  352  is disposed below the upper channel section  292  and is principally contained within the mid-channel section  300 . That is, the upper lip  296  “hangs over” the fluid-containing volume of the blood processing vessel  352  over at least a portion of its length. The upper lip  296  thereby functions to retain the blood processing vessel  352  within the channel  208  during rotation of the channel housing  204 . Moreover, the upper lip  296  reduces the potential for creep by supporting the vessel  352  proximate the upper seal  380 . The upper channel section  292  and the lower channel section  304  are multi-functional in that they also serve to receive and support an upper seal  380  and lower seal  384  of the blood processing vessel  352  to a degree such that the stresses induced on these portions of the blood processing vessel  352  during an apheresis procedure are reduced as will be discussed in more detail below. As can be appreciated, a similarly configured upper lip and lower lip could extend outwardly from the inner channel wall  212  toward, but displaced from, the outer channel wall  216 , alone or in combination with the upper lip  296  and lower lip  308 , and still retain this same general profile for the channel  208  to provide the noted functions. 
     Another desirable attribute of the channel  208  is that it allows for the use of blood as the liquid which primes the blood processing vessel  352  versus, for instance, saline solutions. Priming with blood allows for the actual collection of blood components to begin immediately (i.e., blood used in the prime is separated into blood component types, at least one of which may be collected). Blood priming is subject to a number of characterizations in relation to the apheresis system  2  and is based upon the configuration of the channel  208 . For instance, the configuration of the channel  208  allows for blood to be the first liquid introduced into the blood processing vessel  352  which is loaded in the channel  208 . Moreover, the configuration of the channel  208  allows separated plasma to flow in a clockwise direction through the channel  208  and to reach the control port slot  264  (and thus the control port assembly  488  of the blood processing vessel  352 ) before any separated RBCs or any of the other noted large cells flow in the same clockwise direction beyond the RBC dam  232  and thus into the second stage  316  (i.e., a spillover condition). That is, blood priming may be utilized since control of the interface between the separated RBCs and the buffy coat is established before any RBCs or WBCs spill over into the second stage  316 . Blood priming may also be characterized as providing blood and/or blood components to the entire volume of the blood processing vessel  352  prior to any RBCs or any of the other noted large cells flowing beyond the RBC dam  232  and into the second stage  316 . 
     In order to achieve this desired objective of priming the blood processing vessel  352  with blood, generally the volume of the channel  208  which does not have RBCs to the volume of the channel  208  which does have RBCs must be less than one-half of one less than the ratio of the hematocrit of the RBCs leaving the channel  208  through the RBC outlet port assembly  516  to the hematocrit of the blood being introduced into the channel  208  through the blood inlet port assembly  388 . This may be mathematically expressed as follows:
 
 V   2   /V   1 &lt;( H   RP   /H   IN −1)/2, where:
         V 2 =the volume of the channel  208  containing only plasma or platelet-rich plasma;   V 1 =the volume of the channel  208  containing RBCs of the first stage  312  and third stage  320 ;   H RP =the hematocrit of the packed RBCs leaving the channel  208  through the RBC outlet port assembly  516 ; and   H IN =the hematocrit of the blood entering the channel  208  through the blood inlet port assembly  388 .
 
This equation assumes that the hematocrit in the RBC volume and is calculated as (H in +H RP )/2. In the case where the H IN  is equal to 0.47 and H RP  is equal to 0.75, this requires that the ratio of V 1 /V 2  be less than 0.30 in order for a blood prime to be possible.
       

     The noted ratio may be further characterized as the ratio of that portion of the channel  208  which may be characterized as containing primarily plasma (e.g., V PL ) to the volume of that portion of the channel  208  which may be characterized as containing primarily RBCs (e.g., V RBC ). Referring to  FIG. 15 , these respective volumes may be defined by a reference circle  332  which originates at the rotational axis  324  and which intersects the RBC dam  232  at the illustrated location which would be at the border of a spillover condition. Portions of the channel  208  which are disposed outside of this reference circle  232  are defined as that portion of the channel  208  which includes primarily RBCs or which defines V RBC  (e.g., about 77.85 cc in the illustrated embodiment), while those portions of the channel  208  which are disposed inside of the reference circle  232  are defined as that portion of the channel  208  which includes primarily plasma or which defines V PL  (e.g., about 19.6 cc in the illustrated embodiment). In the illustrated embodiment, the ratio of V PL /V RBC  is about 0.25 which is less than that noted above for the theoretical calculation for the blood prime (i.e., 0.30 based upon comparison of the hematocrits). In order to further achieving the noted desired ratio, the width and height of the channel  208  throughout that portion of the second stage  316  disposed in a clockwise direction from the platelet collect well  236 , also in third stage  320 , are each less than the width and height of the channel  208  throughout the entire first stage  312 . 
     Another important feature relating to the configuration of the channel  208  is that the radially inwardmost portion of the inner channel wall  212  is at the interface with the plasma outlet slot  256 . That is, the entirety of the inner channel wall  212  slopes toward the plasma outlet slot  256 . This allows any air which is present in the blood processing vessel  352  during priming to be removed from the blood processing vessel  352  through the plasma outlet slot  256  and more specifically the plasma outlet port assembly  452  since the air will be the least dense fluid within the blood processing vessel  352  at this time. 
     Another desirable attribute of the channel  208  is that it contributes to being able to utilize a high packing factor in an apheresis procedure. A “packing factor” is a dimensionless quantification of the degree of packing of the various blood component types in the first stage  312  and is thus reflective of the spacings between the various blood component types. The packing factor may thus be viewed similarly to a theoretical density of sorts (e.g., given a quantity of space, what is the maximum number of a particular blood component type that can be contained in this space). 
     The packing factor is more specifically defined by the following equation:
 
 PF=ω   2   ×R ×( v   RBC   /W )× V/Q   IN , where:
         PF=packing factor;   ω=rotational velocity;   R=the average radius of the outer channel wall  216  in the first cell separation stage  312 ;   v RBC =the sedimentation velocity of RBCs at 1G;   V=the functional volume of the first cell separation stage  312 ;   W=the average sedimentation distance or width of the channel  208 ; and   Q IN =the total inlet flow to the channel  208 .
 
Consequently, the packing factor as used herein is dependent upon not only the configuration of the channel  208 , particularly the first stage  312 , but the rotational velocities being used in the apheresis procedure as well as the inlet flow to the blood processing vessel  352 . The following are packing factors associated with the blood processing channel  208  having the above-described dimensions:
       

                                                             N   Q in     V       G   P@R1st           (rpm)   ml/mi   (ml)   PF   @R avg     (psi)                                                                    0   0   62.8   0.0   0.0   0.0           905   5   62.8   13.0   100.1   8.1           1279   10   62.8   13.0   200.2   16.2           1567   15   62.8   13.0   300.2   24.3           1809   20   62.8   13.0   400.3   32.5           2023   25   62.8   13.0   500.4   40.6           2216   30   62.8   13.0   600.5   48.7       FF8   2394   35   62.8   13.0   700.6   56.8       SLOPE = .02   2559   40   62.8   13.0   800.6   64.9           2714   45   62.8   13.0   900.7   73.0           2861   50   62.8   13.0   1100.9   81.1           3001   55   62.8   13.0   1100.9   89.3           3001   60   62.8   11.9   1100.9   89.3           3001   65   62.8   11.0   1100.9   89.3           3001   70   62.8   10.2   1100.9   89.3           3001   75   62.8   9.5   1100.9   89.3           3001   80   62.8   8.9   1100.9   89.3           3001   85   62.8   8.4   1100.9   89.3           3001   90   62.8   7.9   1100.9   89.3           3001   95   62.8   7.5   1100.9   89.3           3001   100   62.8   7.1   1100.9   89.3           3001   105   62.8   6.8   1100.9   89.3           3001   110   62.8   6.5   1100.9   89.3           3001   115   62.8   6.2   1100.9   89.3           3001   120   62.8   6.0   1100.9   89.3           3001   125   62.8   5.7   1100.9   89.3           3001   130   62.8   5.5   1100.9   89.3           3001   135   62.8   5.3   1100.9   89.3           3001   140   62.8   5.1   1100.9   89.3                    
Note the G forces are listed for the various rotational speeds at the middle of the first stage  312  and for a 10 inch outer diameter for the channel housing  204 . At about 2,560 RPM, the G force is about 800 G, while at about 3,000 RPM the G force is about 1,100 Gs.
 
     Increasing the packing factor beyond a certain point produces diminishing returns regarding the collection of blood component types. That is, further increases in packing factor may not produce correspondingly increased collection efficiencies and may in fact impede the collection of blood component types. It is believed that a packing factor ranging from about 11 to about 15, and more preferably about 13, is optimum for collection of blood component types. As such, the rotational velocity of the channel housing  204  may be adjusted based upon the inlet flows being provided to the blood processing vessel  352  to maintain the packing factor. For instance, the desired operating speed for the centrifuge housing  204  during the normal course of an apheresis procedure is about 3,000 RPM. However, this rotational speed may be reduced to “match” the inlet flow to the blood processing vessel  352  in order to retain the desired packing factor. Similarly, the rotational speed of the channel housing  204  may be increased to “match” an increased inlet flow to the blood processing vessel  352  in order to retain the desired packing factor. 
     Due to constraints regarding the blood processing vessel  352 , more specifically the various tubes interconnected therewith (e.g., which provide the seal-less loop), the above-noted desired packing factor of about 13 may be realized for inlet flows of up to about 55 ml/min. (instantaneous). Beyond 55 ml/min., the rotational speed would have to be increased above 3000 RMP to maintain the desired packing factor of about 13. Although tubes exist which will withstand those rotational speeds, presently they are not approved for use in an apheresis system. With the presently approved tubing, the packing factor may be maintained at a minimum of about 10, and preferably at least about 10.2, for inlet flows (instantaneous) of about 40-70 ml/min. 
     At the above noted increased rotational speeds, the channel  208  not only provides for achieving an increased packing factor, but reduces the impact of this high packing factor on the collection efficiency regarding platelet collection. Specifically, the configuration of the channel  208  is selected to reduce the number of platelets that are retained within the first stage  312 . The configuration of the channel  208  in the first stage  208  utilizes a progressively reduced width or sedimentation distance progressing from the blood inlet slot  224  to the RBC dam  232 . That is, the width of the channel  208  proximate the blood inlet slot  224  is less than the width of the channel  208  proximate the RBC dam  232 . This configuration of the channel  208  in the first stage  312  reduces the volume of the “buffy coat” or more specifically layer between the RBCs and platelets to be collected. As noted, this buffy coat includes primarily WBCs and lymphocytes, as well as the radially outwardmost portion of the platelet layer. The “buffy coat” is preferably retained in the first stage  312  during an apheresis procedure. Since the volume of the “buffy coat” is reduced by the reduced width of the channel  208  proximate the RBC dam  232 , this reduces the number of platelets which are retained in the first stage  312 , and thus increases the number of platelets which flow to the platelet collect well  236 . 
     Disposable Set: Blood Processing Vessel 
     The blood processing vessel  352  is disposed within the channel  208  for directly interfacing with and receiving a flow of blood in an apheresis procedure. The use of the blood processing vessel  352  alleviates the need for sterilization of the channel housing  204  after each apheresis procedure and the vessel  352  may be discarded to provide a disposable system. There are initially two important characteristics regarding the overall structure of the blood processing vessel  352 . The blood processing vessel  352  is constructed such that it is sufficiently rigid to be free standing in the channel  208 . Moreover, the blood processing vessel  352  is also sufficiently rigid so as to loaded in the channel  208  having the above-identified configuration (i.e., such that the blood processing vessel  352  must be directed through the reduced width upper channel section  292  before passage into the larger width mid-channel section  300 ). However, the blood processing vessel  352  must also be sufficiently flexible so as to substantially conform to the shape of the channel  208  during an apheresis procedure. 
     In order to achieve the above-noted characteristics, the blood processing vessel  352  may be constructed as follows. Initially, materials for the blood processing vessel  352  include PVC, PETG, and polyolifins, with PVC being preferred. Moreover, the wall of thickness of the blood processing vessel  352  will typically range between about 0.030″ and 0.040″. Furthermore, the durometer rating of the body of the blood processing vessel  352  will generally range from about 50 Shore A to about 90 Shore A. 
     Referring primarily to  FIGS. 16-23B , the blood processing vessel  352  includes a first end  356  and a second end  364  which overlaps with the first end  356  and is radially spaced therefrom. A first connector  360  is disposed proximate the first end  356  and a second connector  368  is disposed proximate the second end  364 . When the first connector  360  and second connector  368  are engaged (typically permanently), a continuous flow path is available through the blood processing vessel  352 . This construction of the blood processing vessel  352  facilitates loading in the channel  208  in the proper position and as noted also contributes to the automatic control of the interface between the separated RBCs and the buffy coat relative to the RBC dam  232 . 
     The blood processing vessel  352  includes an inner sidewall  372  and an outer sidewall  376 . In the illustrated embodiment, the blood processing vessel  352  is formed by sealing two pieces of material together (e.g., RF welding). More specifically, the inner sidewall  372  and outer sidewall  376  are connected along the entire length of the blood processing vessel  352  to define an upper seal  380  and a lower seal  384 . Seals are also provided on the ends of the vessel  352 . The upper seal  380  is disposed in the reduced width upper channel section  292  of the channel  208 , while the lower seal  384  is disposed in the reduced width lower channel section  304  of the channel  208  (e.g., FIG.  19 F). This again reduces the stresses on the upper seal  380  and lower seal  384  when a flow of blood is provided to the blood processing vessel  352  and pressurizes the same. That is, the upper seal  380  and lower seal  384  are effectively supported by the channel  208  during an apheresis procedure such that a resistance is provided to a “pulling apart” of the upper seal  380  and lower seal  384 . By utilizing two separate sheets to form the blood processing vessel  352 , a “flatter” profile may also be achieved. This type of profile is beneficial during rinseback, and also facilitates loading and unloading of the vessel  352  relative to the channel  208 . 
     Blood is introduced into the interior of the blood processing vessel  352  through a blood inlet port assembly  388  which is more particularly illustrated in  FIGS. 19A-G . Initially, the port  392 , as all other ports, is welded to the blood processing vessel  352  over a relatively small area. This results in less movement of materials due to the welding procedure which provides a smoother surface for engagement by the blood and/or blood component types. 
     The blood inlet port assembly  388  includes a blood inlet port  392  and a blood inlet tube  412  which is fluidly interconnected therewith exteriorly of the blood processing vessel  352 . The blood inlet port  392  extends through and beyond the inner sidewall  372  of the blood processing vessel  352  into an interior portion of the blood processing vessel  352 . Generally, the blood inlet port assembly  388  is structured to allow blood to be introduced into the blood processing vessel  352  during an apheresis procedure without substantially adversely affecting the operation of the apheresis system  2 . 
     The blood inlet port  392  includes a substantially cylindrical sidewall  396 . A generally vertically extending slot  404  is disposed proximate an end of the sidewall  396  of the blood inlet port  392  such that the slot  404  is substantially parallel with the inner sidewall  372  and outer sidewall  376  of the blood processing vessel  352 . The slot  404  projects in the clockwise direction, and thus directs the flow of blood in the channel  208  generally toward the RBC dam  232 . A vane  400  is positioned on the end of the cylindrical sidewall  396 , is disposed to be substantially parallel with the inner sidewall  372 , and thereby directs the flow of blood out through the slot  404 . As illustrated in  FIG. 19D , the vane  400  includes a generally V-shaped notch on the interior of the blood inlet port  392 , the arcuate extent of which defines the “height” of the slot  404 . 
     The desired manner of flow of blood into the blood processing vessel  352  during an apheresis procedure is subject to a number of characterizations, each of which is provided by the above-described blood inlet port assembly  388 . Initially, the flow of blood into the blood processing vessel may be characterized as being at an angle of less than 90° relative a reference line which is perpendicular to the inner sidewall  372  of the blood processing vessel  352 . That is, the blood is injected in a direction which is at least partially in the direction of the desired flow of blood through the blood processing vessel  352 . Moreover, the desired flow of blood into the blood processing vessel  352  may be characterized as that which reduces the effect on other flow characteristics within blood processing vessel  352  at the blood inlet port  392 . 
     Separated RBCs  556  again flow along the outer sidewall  376  of the blood processing vessel  352  adjacent the outer channel wall  216 , past the blood inlet port  392 , and to the RBC outlet port assembly  516  as illustrated in  FIGS. 19E and 19G . The desired flow of blood into the blood processing vessel  352  may then be further characterized as that which is substantially parallel with at least one other flow in the region of the blood inlet port  392  (e.g., inject the blood substantially parallel with the flow of RBCs  556 ). This manner of introducing blood into the blood processing vessel  352  may then be further characterized as that which does not significantly impact at least one other flow in the region of the blood inlet port  392 . 
     As noted above, the blood inlet port assembly  388  interfaces with the inner sidewall  372  of the blood processing vessel  352  in a manner which minimizes the discontinuity along the inner channel wall  212  in the region of the blood inlet slot  224  in which the blood inlet port  392  is disposed. Specifically, a shield  408  may be integrally formed with and disposed about the blood inlet port  392 . The shield  408  is disposed on an exterior surface of the blood processing vessel  352  and interfaces with its inner sidewall  372 . The shield  408  is at least in partial overlapping relation with the inner sidewall  372 ). Moreover, in the case where the shield  408  is integrally formed with the port  392 , it need not be attached to the inner sidewall  372 . The port  392  is installed asymmetrical relative to the shield  408  which is beneficial for manufacturability. All shields and their blood-related ports discussed below also include this feature. 
     Generally, the shield  408  is more rigid than the inner sidewall  372  of the blood processing vessel  352 . This increased rigidity may be provided by utilizing a more rigid material for the shield  408  than is used for the inner sidewall  372 . For instance, the durometer rating of the material forming the shield  408  may range from about 90 Shore A to about 130 Shore A, while the durometer rating of the material forming the inner sidewall  372  of the blood processing vessel  352  again ranges from about 50 Shore A to about 90 Shore A in one embodiment. This durometer rating (when the shield  408  and port  392  are integrally formed) also enhances the seal between the port  392  and the tube installed therein. 
     When the blood inlet port  392  is disposed in the blood inlet slot  224  when loading the blood processing vessel  352  in the channel  208 , the shield  408  is positioned within the recess  228  formed in the inner channel wall  212 . Again, the blood inlet slot  224  intersects with the inner channel wall  212 , and more specifically the recess  228 . That is, the recess  228  contains and is disposed about one end of the blood inlet slot  224 . Preferably, the thickness of the shield  408  is substantially equal to the depth or thickness of the recess  228  such that the amount of discontinuity along the inner channel wall  212  in the region of the blood inlet slot  224  is reduced or minimized. Due to the increased rigidity of the shield  408  in comparison to the materials forming the blood processing vessel  352 , when the blood processing vessel  352  is pressurized during an apheresis procedure the shield  408  restricts movement of the blood processing vessel  352  and/or the blood inlet port  392  into the blood inlet slot  224 . That is, the shield  408  restricts and preferably minimizes any deflection of the blood processing vessel  352  into the blood inlet slot  224  during the procedure. Moreover, with the shield  408  being integrally formed with the blood inlet port  392 , the radial position of the vertical slot  404  in the blood inlet port  392  is not dependent upon the thickness of the materials forming the blood processing vessel  352 . 
     In the first stage  312 , blood which is provided to the blood processing vessel  352  by the blood inlet port assembly  388  is separated into RBCs, WBCs, platelets, and plasma. The RBCs, as well as the WBCs, are retained within the first stage  312  and are preferably precluded from flowing in a clockwise direction past the RBC dam  232  into the platelet collect well  236 . Instead, the RBCs and WBCs are induced to flow along the outer channel wall  216  in a counterclockwise direction past the blood inlet port  392  and toward the RBC outlet port assembly  516  of the blood processing vessel  352 . That is, the RBC outlet port assembly  516  is disposed in a counterclockwise direction from the blood inlet port assembly  388 . However, as noted above, the control port dam  280  impedes the flow buffy coat control port assembly  488  to provide a sharp interface between the separated RBCs and the plasma proximate the control port assembly  488  such that this may be used to control the radial position of the interface between the RBCs and the buffy coat in the area of the RBC dam  232 . 
     The RBC outlet port assembly  516  is more specifically illustrated in  FIGS. 20A-D  and generally includes an RBC outlet port  520  and an RBC outlet tube  540  fluidly interconnected therewith exteriorly of the blood processing vessel  352 . The RBC outlet port  520  extends through and beyond the inner sidewall  372  of the blood processing vessel  352  into an interior portion of the blood processing vessel  352 . In addition to removing separated RBCs from the blood processing vessel  352  during an apheresis procedure, the RBC outlet port assembly  516  also functions in combination with the control port assembly  488  to automatically control the radial position of the interface between separated RBCs and the buffy coat relative to the RBC dam  232  (e.g., to prevent RBCs from flowing beyond the RBC dam  232 ) in a manner discussed in more detail below. 
     The RBC outlet port  520  is also configured to reduce the potential for the flow therethrough being obstructed during rinseback (i.e., during an attempted evacuation of the blood processing vessel  352  upon completion of blood component separation so as to provide as much of the contents thereof back to the donor/patient  4 ). During rinseback, the rotation of the channel housing  204  is terminated and a relatively significant drawing action (e.g., by pumping) is utilized to attempt to remove all contents from the blood processing vessel  352 . The end of the RBC outlet port  520  includes a first protrusion  524  and a second protrusion  528  displaced therefrom, with a central recess  532  being disposed therebetween which contains the noted orifice  536  for the blood outlet port  520 . The first protrusion  524  and the second protrusion  528  each extend further beyond the inner sidewall  372  of the blood processing vessel  352  a greater distance then the central recess  532 . As such, during rinseback if the outer sidewall  376  attempts to contact the inner sidewall  372 , the first protrusion  524  and second protrusion  528  will displace the central recess  532  and its orifice  536  away from the outer sidewall  376 . This retains the orifice  536  in an open condition such that the flow therethrough is not obstructed during rinseback. 
     As noted above, the RBC outlet port assembly  516  interfaces with the inner sidewall  372  of the blood processing vessel  352  in a manner which minimizes the discontinuity along the inner channel wall  212  in the region of the RBC outlet  272  in which the RBC outlet port  520  is disposed. Specifically, a shield  538  is integrally formed with and disposed about the RBC outlet port  520 . The shield  538  is disposed on an exterior surface of the blood processing vessel  352  and interfaces with its inner sidewall  372 . The shield  538  is at least in partial over-lapping. relation with the inner sidewall  372 . Moreover, in the case where the shield  538  is integrally formed with the port  520 , it need not be attached to the inner sidewall  372 . Generally, the shield  538  is more rigid than the inner sidewall  372 . This increased rigidity may be provided by utilizing a more rigid material for the shield  538  than is used for the inner sidewall  372 . For instance, the durometer rating of the material forming the shield  538  may range from about 90 Shore A to about 130 Shore A, while the durometer rating of the material forming the inner sidewall  372  of the blood processing vessel  352  again ranges from about 50 Shore A to about 90 Shore A in one embodiment. 
     When the RBC outlet port  520  is disposed in the RBC outlet slot  272  when loading the blood processing vessel  352  in the channel  208 , the shield  538  is positioned within the recess  276  formed in the inner channel wall  212 . Again, the RBC outlet slot  272  intersects with the inner channel wall  212 , and more specifically the recess  276 . That is, the recess  276  contains and is disposed about one end of the RBC outlet slot  272 . Preferably, the thickness of the shield  538  is substantially equal to the depth or thickness of the recess  276  such that the amount of discontinuity along the inner channel wall  212  in the region of the RBC outlet slot  272  is reduced or minimized. Due to the increased rigidity of the shield  538  in comparison to the materials forming the blood processing vessel  352 , when the blood processing vessel  352  is pressurized during an apheresis procedure, the shield  538  restricts movement of the blood processing vessel  352  and/or the RBC outlet port  520  into the RBC outlet slot  272 . That is, the shield  538  restricts and preferably minimizes any deflection of the blood processing vessel  352  into the RBC outlet slot  272 . Moreover, with the shield  538  being integrally formed with the RBC outlet port  520 , the radial position of the orifice  536  is not dependent upon the thickness of the materials forming the blood processing vessel  352 . 
     Separated platelets are allowed to flow beyond the RBC dam  232  and into the second stage  316  of the channel  208  in platelet-rich plasma. The blood processing vessel  352  includes a platelet collect port assembly  416  to continually remove these platelets from the vessel  352  throughout an apheresis procedure and such is more particularly illustrated in  FIGS. 8 ,  16 , and  21 A-B. Generally, the platelet collect port assembly  416  is disposed in a clockwise direction from the blood inlet port assembly  388 , as well as from the RBC dam  232  when the blood processing vessel  352  is loaded into the channel  208 . Moreover, the platelet collect port assembly  416  interfaces with the outer sidewall  376  of the blood processing vessel  352 . 
     The platelet collect port assembly  416  is disposed in the platelet support recess  249  and the platelet outlet tube recess  254  which are disposed radially outwardly from the portion of the platelet collect well  236  defined by the outer channel wall  216  of the channel  208 . The platelet collect port assembly  416  generally includes a platelet collect port  420  and a platelet collect tube  424  which is fluidly interconnected therewith exteriorly of the blood processing vessel  352 . The orifice  422  of the port  420  may be substantially flush with the interior surface of the outer sidewall  376  of the blood processing vessel  352 . Moreover, the radial position of the orifice  422  is established by engagement of part of the platelet collect port  420  with boundaries of the recess  249  and/or  254 . 
     The platelet collect port  420  is welded to the blood processing vessel  352 . The thickness of the overlapping portions of the port  420  and vessel  352  are substantially equal. The weld area is overheated such that there is a mixing of the two materials. This results in the platelet collect port  420  being able to flex substantially against the outer channel wall  216  when the vessel  352  is pressurized. 
     The blood processing vessel  352  and the outer channel wall  216  of the channel  210  collectively define the platelet collect well  236 . The contribution of the blood processing vessel  352  to the platelet collect well  236  is provided by a substantially rigid support  428  which is disposed vertically above the platelet collect port  420  and hingedly interconnected at location  430  with the outer sidewall  376  and/or a mounting plate  426  of the platelet collect port  420 . The contoured support  428  includes a first face  432  and a second face  436  which interface with the exterior surface of the outer sidewall  376  of the blood processing vessel  352  (i.e., the support overlaps with the sidewall  376  of the blood processing vessel  352  and need not be attached thereto over the entire interface therewith) and which are disposed in different angular positions. The upper portion of the first face  432  extends over the top of the blood processing vessel  352 , while the lower portion of the first face  432  generally coincides with the upper seal  380  on the blood processing vessel  352 . The second face  436  interfaces with the outer sidewall  376  in a region of the fluid-containing volume of the blood processing vessel  352  and is the primary surface which directs platelets toward the platelet collect port  420 . 
     When the blood processing vessel  352  is pressurized, the support  428  moves into a predetermined position defined by portions of the platelet collect recess  252 . Specifically, a third face  440  is retained under an upper lip  254  on the upper perimeter of the platelet support recess  249 , and the two sides of a fourth face  444  seat against a shoulder  252  disposed on each side of the platelet support recess  249 . A platelet tubing notch  448  is formed in the support  428  at generally the intersection between the third face  440  and the fourth face  444 . The platelet collect tube  426  thus may extend out from the platelet collect port  420 , up the platelet collect tube recess  254 , against the platelet tube notch  448  if necessary, and above the channel housing  204  to pass down through the central opening  328  therein. 
     In order to increase the purity of platelets that are collected, a platelet purification system as described in U.S. patent application Ser. Nos. 08/423,578 and 08/423,583 may be disposed in the platelet collect tube 424, and the entire disclosures of these patent applications is incorporated by reference in their entirety herein. 
     Platelet-poor plasma flows beyond the platelet collect well  236  and to the plasma outlet port assembly  452 . Here, some of the platelet-poor plasma may be removed from the blood processing vessel  352  and collected, although this “separated” plasma may also be returned the donor/patient  4  in some instances. The plasma port  456  is also used in the blood priming of the vessel  352  in that air is removed from the vessel  352  through the plasma port  456 . Referring to  FIG. 22 , the plasma outlet port assembly  452  includes a plasma outlet port  456  and a plasma outlet tube  476  which is fluidly interconnected therewith exteriorly of the blood processing vessel  352 . The plasma outlet port  456  extends through and beyond the inner sidewall  372  of the blood processing vessel  352  into an interior of the blood processing vessel  352 . The plasma outlet port  456  is disposed between the second end  364  of the blood processing vessel  352  and the second connector  368 . 
     The plasma outlet port  456  is configured to reduce the potential for the flow therethrough being obstructed during rinseback (i.e., during an attempted evacuation of the blood processing vessel  352  upon completion of an apheresis procedure so as to provide as much of the contents thereof back to the donor/patient  4 ). During rinseback, the rotation of the channel housing  204  is terminated and a relatively significant drawing action (e.g., by pumping) is utilized to attempt to remove all contents from the blood processing vessel  352 . The end of the plasma outlet port  456  includes a first protrusion  460  and a second protrusion  464  displaced therefrom, with a central recess  468  being disposed therebetween which contains an orifice  472  for the plasma outlet port  456 . The first protrusion  460  and the second protrusion  464  each extend further beyond the inner sidewall  372  of the blood processing vessel  352  a greater distance then the central recess  468 . As such, during rinseback if the outer sidewall  376  attempts to contact the inner sidewall  372 , the first protrusion  460  and second protrusion  464  will displace the central recess  468  and its orifice  472  away from the outer sidewall  376 . This retains the orifice  472  in an open condition such that the flow therethrough is not obstructed during rinseback. 
     In order to further assist in withdrawal from the blood processing vessel  352  after completion of an apheresis procedure and thus during rinseback, a first passageway  480  and a second passageway  484  are formed in the blood processing vessel  352  (e.g., via heat seals, RF seals) and generally extend downwardly from the plasma outlet port  456  toward a lower portion of the blood processing vessel  352 . The first passageway  480  and second passageway  484  are disposed on opposite sides of the plasma outlet port  456 . With this configuration, a drawing action through the plasma outlet port  456  is initiated in a lower portion of the blood processing vessel  352  at two displaced locations. 
     Some of the separated plasma is also utilized to automatically control the location of the interface between separated RBCs and the buffy coat in the first stage  312 , specifically the radial position of this interface relative to the RBC dam  232 . Plasma which provides this interface control function is removed from the blood processing vessel  352  by a control port assembly  488  which is illustrated in  FIGS. 23A-B . The control port assembly  488  is disposed in a clockwise direction from the plasma outlet port assembly  452  and proximate the RBC outlet port assembly  516 , and thus between the first end  284  of the channel  208  and the RBC outlet port assembly  516 . This plasma thus flows from the second stage  316  and into the third stage  320  to provide this function. 
     The control port assembly  488  generally includes a control port  492  and control port tube  512  which is fluidly interconnected therewith exteriorly of the blood processing vessel  352 . The control port  492  extends through and beyond the inner sidewall  372  of the blood processing vessel  352  into an interior portion of the blood processing vessel  352 . The radial positioning of the orifice  504  of the control port  492  is not dependent upon the thickness of the material forming the blood processing vessel  352 . Instead, the control port  492  includes a shoulder  496  which engages or seats upon structure within the control port slot  264  to accurately place the orifice  504  at a predetermined radial position within the channel  208 . Moreover, this predetermined radial position is substantially maintained even after the blood processing vessel is pressurized. In this regard, the control port assembly  488  interfaces with the inner sidewall  372  of the blood processing vessel  352  in a manner which minimizes the discontinuity along the inner channel wall  212  in the region of the control port slot  264  in which the control port  492  is disposed. Specifically, a shield  508  is integrally formed with and disposed about the control port  492 . The shield  508  is disposed on an exterior surface of the blood processing vessel  352  and interfaces with its inner sidewall  372 . The shield  508  is at least in partial over-lapping relation with the inner sidewall  372 . Moreover, in the case where the shield  508  is integrally formed with the port  492 , it need not be attached to the inner sidewall  372 . Generally, the shield  508  is more rigid than the inner sidewall  372  and this assists in maintaining the orifice  504  of the control port  492  at the desired radial position within the channel  208 . This increased rigidity may be provided by utilizing a more rigid material for the shield  508  than is used for the inner sidewall  372 . For instance, the durometer rating of the material forming the shield  508  may range from about 90 Shore A to about 130 Shore A, while the durometer rating of the material forming the inner sidewall  372  of the blood processing vessel  352  again ranges from about 50 Shore A to about 90 Shore A in one embodiment. 
     The control port assembly  488  and the RBC outlet port assembly  516  function in combination to control the radial position of the interface between separated RBCs and the buffy coat relative to the RBC dam  232 . Two structural differences between the RBC outlet port assembly  516  and the control port assembly  488  contribute to achieving this automatic control. Initially, the orifice  536  to the RBC outlet port  520  is disposed further into the interior of the blood processing vessel  352  than the control port  492 . In one embodiment, the orifice  538  of the RBC outlet port  520  is disposed more radially outwardly than the orifice  504  of the control port  492 . Moreover, the diameter of the RBC outlet tube  540  is greater than that of the control port tube  512 . In one embodiment, the inner diameter of the RBC outlet tube  54  is about 0.094″, while the inner diameter of the control port tube  512  is about 0.035″. The control port tube  512  and RBC outlet tube  540  also join into a common return tube  546  via a three-way tubing jack  544  which further assists in providing the automatic interface control feature. 
     The automatic interface position control is provided as follows utilizing the RBC outlet port assembly  516  and the control port assembly  488 . Initially, there are two interfaces in the channel  208  of significance with regard to this automatic interface position control feature. One of these interfaces is the RBC/buffy coat interface in relation to the RBC dam  232 . However, there is also an RBC/plasma interface in the region of the control port assembly  488  which again is available through use of the control port dam  280 . The control port dam  280  allows substantially only RBCs to flow to the control port assembly  488  in a counterclockwise direction. 
     In the event that the interface between the RBCs and plasma moves radially inwardly toward the rotational axis  324 , RBCs will begin flowing out the control port tube  512  in addition to the RBC outlet tube  540 . This decreases the flow through the smaller diameter control port tube  512  due to the higher viscosity and density of the RBCs compared to the plasma which typically flows through the control port tube  512 . Consequently, the flow through the larger diameter RBC outlet tube  540  must increase since the flow through the return tube  546  must remain the same. This removes more RBCs from the first stage  312  such that both the interface between the RBCs and the buffy coat in relation to the RBC dam  232  and the interface between the RBCs and the plasma both move radially outwardly. That is, this changes the radial position of each of these interfaces. As such, the potential for RBCs flowing beyond the RBC dam  232  and into the platelet collect well  236  is reduced. 
     In the event that the location of the interface between the RBCs and plasma progresses radially outward, the flow through the control port tube  512  will increase since the quantity of RECs exiting the blood processing vessel  352  through the control port  512  will have decreased. Since the flow through the return tube  546  must remain the same, this results in a decrease in the flow of RBCs through the RBC outlet tube  540 . This reduces the number of RBCs being removed from the channel  208  such that both the interface between the RBCs and the buffy coat in relation to the RBC dam  232  and the interface between the RBCs and the plasma both move radially inwardly. That is, this changes the radial position of each of these interfaces. 
     The above-described tubes which interface with the blood processing vessel  352 , namely the blood inlet tube  412 , the platelet collect tube  424 , the plasma outlet tube  476 , the return tube  546 , each pass downwardly through the central opening  328  in the channel housing  204 . A tubing jacket  548  is disposed about these various tubes and protects such tubes during rotation of the channel housing  204 . These tubes are also fluidly interconnected with the extracorporeal tubing circuit  10  which again provides for fluid communication between the donor/patient  4  and the blood processing vessel  352 . 
     The blood processing vessel  352  also includes features for loading and unloading the same from the channel  208 . Referring back to  FIG. 16 , the vessel  352  includes at least one and preferably a plurality of tabs  552 . The tabs  552  may be integrally formed with the blood processing vessel  352  (e.g., formed by the seal which also forms the upper seal  380 ). However, the tabs  552  may also be separately attached. The tabs  552  nonetheless extend vertically above the fluid-containing volume of the blood processing vessel  352 , preferably a distance such that the tabs  552  actually project above the channel housing  204 . The tabs  552  thereby provide a convenient non-fluid-containing structure for the operator to grasp and load/remove the blood processing vessel  352  into/from the channel  208  (i.e., they provide structure for the operator to grasp which has had no blood-related flow therethrough during the apheresis procedure). The tabs  552  are particularly useful since there may be resistance provided to a loading and an unloading of the blood processing vessel  352  into/from the channel  208 . 
     Centrifuge Rotor Assembly 
     The channel assembly  200  is mounted on the centrifuge rotor assembly  568  which rotates the channel assembly  200  to separate the blood into the various blood component types by centrifugation. The centrifuge rotor assembly  568  is principally illustrated in  FIGS. 24-25  and generally includes a lower rotor housing  584  having a lower gear  588 . An input or drive shaft  576  is disposed within the lower rotor housing  584  and is rotatably driven by an appropriate motor  572 . The input/drive shaft  576  includes a platform  580  mounted on an upper portion thereof and a rotor body  592  is detachably interconnected with the platform  580  such that it will rotate therewith as the input/drive shaft  576  is rotated by the motor  572 . 
     The centrifuge rotor assembly  568  further includes an upper rotor housing  632  which includes a mounting ring  644  on which the channel housing  204  is positioned. In order to allow the channel housing  204  to rotate at twice the speed of the rotor body  592 , the upper rotor housing  632  and lower rotor housing  584  are rotatably interconnected by a pinion assembly  612 . The pinion assembly  612  is mounted on the rotor body  592  and includes a pinion mounting assembly  616  and a rotatable pinion  620 . The pinion  620  interfaces with the lower gear  588  and a driven gear  636  which is mounted on the mounting ring  644 . The gear ratio is such that for every one revolution of the rotor body  592 , the upper rotor housing  632  rotates twice. This ratio is desired such that no rotary seals are required for the tubes interfacing with the blood processing vessel  352 . In one embodiment, the lower gear  588 , the pinion  620 , and the driven gear  636  utilize straight bevel gearing. 
     The centrifuge rotor assembly  568  is also configured for easy loading of the blood processing vessel  352  in the channel  208  of the channel housing  204 . In this regard, the rotor body  592  includes a generally L-shaped blood processing vessel loading aperture  597 . The aperture  597  includes a lower aperture  600  which extends generally horizontally into the rotor body  592  through its sidewall  596  of the rotor body  592 , but only partially therethrough. The perimeter of the lower aperture  600  is defined by a left concave wall  601 , a back concave wall  603 , and a right concave wall  602 . 
     The loading aperture  597  also includes an upper aperture  598  which intersects with the lower aperture  600  at  599  and extends upwardly through an upper portion of the rotor body  592 . The upper aperture  598  is aligned with a generally vertically extending central opening  640  in the upper rotor housing  632 . As noted above, the channel housing  204  also includes a central opening  328 . As such, a blood processing vessel  352  may be folded if desired, inserted into the lower aperture  600 , deflected upwardly by the back concave wall  603 , through the upper aperture  598 , through the central opening  640  in the upper rotor housing  632 , and through the central opening  328  of the channel housing  204 . The operator may then grasp the blood processing vessel  352  and load the same in the channel  208 . 
     The centrifuge rotor assembly  568  includes a number of additional features to facilitate the loading of the blood processing vessel  352  in the channel  208 . Initially, the pinion  620  is radially offset in relation to the lower aperture  600  of the rotor body  592 . In one embodiment, a reference axis laterally bisects the lower aperture  600  and may be referred to as the “zero axis”. The axis about which the pinon  620  rotates is displaced from this “zero axis” by an angle α of about 40° in the illustrated embodiment. An angle α of −40° could also be used. Positioning the pinion  620  at an angle of “greater” than ±40° will result in the pinion  620  beginning to interfere with the access to the loading aperture  597 . Although the angle α may be less than 40° and may even be 0°, having the pinion  620  at 0° will result in the counterweights  608  potentially interfering with the access to the loading aperture  597 . Based upon the foregoing, in  FIG. 25  the pinion assembly  612  has therefore been rotated about the axis which the centrifuge rotor assembly  568  rotates for ease of illustration. 
     Since only a single drive gear is utilized to rotate the upper rotor housing  632  relative to the rotor body  592 , an upper counterweight  604  and lower counterweight  608  are disposed or detachably connected to the rotor body  592  proximate the upper and lower extremes of the lower aperture  600 . Due to the offset positioning of the pinion  620  in relation to the lower aperture  600 , the upper and lower counterweights  604 ,  608  are also radially offset in relation to the lower aperture  600 . That is, the upper and lower counterweights  604 ,  608  are “off to the side” in relation to the lower aperture  600  such that access thereto is not substantially affected by the counterweights  604  and  608 . A tube mounting arm  624  is also appropriately attached to the rotor body  592  and engages the tubing jacket  548 . The tubing mounting arm  624  serves to further the rotational balance of the rotor body  592 . 
     Another feature of the centrifuge rotor assembly  568  which contributes to the loading of the blood processing vessel  352  upwardly through the rotor body  592  is the size of the lower aperture  600 . As illustrated in  FIG. 25B , the “width” of the lower aperture may be defined by an angle θ which may range from about 70° to about 90°, and in the illustrated embodiment is about 74°. The back wall  603 , left wall  601 , and right wall  602  are also defined by a radius ranging from about 1.75″ to about 2.250″, and in the illustrated embodiment this radius is between about 2.008″ and about 2.032″. 
     Apheresis Protocol 
     One protocol which may be followed for performing an apheresis procedure on a donor/patient  4  utilizing the above-described system  2  will now be summarized. Initially, an operator loads the cassette assembly  110  onto the pump/valve/sensor assembly  1000  of the blood component separation device  6  and hangs the various bags (e.g., bags  114 ,  94 ,  84 ) on the blood component separation device  6 . The operator then loads the blood processing vessel  352  within the channel  208  which is disposed on the channel housing  204  which is in turn mounted on the centrifuge rotor assembly  568 , particularly the mounting ring  644 . More specifically, the operator may fold the blood processing vessel  352  and insert the same into the blood processing vessel loading aperture  597  on the rotor body  592 . Due to the arcuately-shaped, concave configuration of the loading aperture  597 , specifically the lower aperture  600 , the blood processing vessel  352  is deflected upwardly through the upper aperture  598 , the central opening  640  in the upper rotor housing, and the central opening  328  in the channel housing  294 . The operator then grasps the blood processing vessel  352  and pulls it upwardly away from the channel housing  204 . 
     Once the blood processing vessel  352  has been installed up through the centrifuge rotor assembly  568 , the operator loads the blood processing vessel  352  into the channel  208  on the channel housing  204 . The operator generally aligns the blood processing vessel  352  relative to the channel  208  (e.g., such that the blood inlet port  392  is vertically aligned with the blood inlet slot  224 , such that the platelet collect port  420  is vertically aligned with the platelet support recess  249  and the platelet collect tube recess  254 , such that the plasma outlet port  456  is vertically aligned with the plasma outlet slot  256 , such that the control port  492  is vertically aligned with the control port slot  264 , and such that the RBC outlet port  520  is vertically aligned with the RBC outlet slot  272 ). Once again, the interconnection of the first connector  360  and second connector  368 , which is preferably fixed, facilitates the loading of the blood processing vessel  352 , as well as the existence of the chamfer  210 . 
     With the blood processing vessel  352  properly aligned, the operator directs the blood processing vessel  352  through the reduced width upper channel section  292  of the channel  208  until the blood processing vessel  352  hits the channel base  220 . In this case, the longitudinal extent of the blood processing vessel  352  located in the portion of the channel  208  which includes the first stage  312 , the RBC dam  232 , and the platelet collect stage  316  will be disposed as follows: 1) the upper seal  380  will be disposed in the upper channel section  292 ; 2) the fluid-containing volume of the blood processing vessel  352  will be disposed in the mid channel section  300 ; and 3) the lower seal  384  will be disposed in the lower channel section  304 . The above-noted ports will also be disposed in their respective slots in the channel housing  204  by the operator at this time. Moreover, the shield  408  associated with the blood inlet port assembly  388  will be disposed in the recess  228  associated with the blood inlet slot  224 . Similarly, the shield  538  associated with the RBC outlet port assembly  516  will be disposed in the recess  276  associated with the RBC outlet slot  272 . Furthermore, the shield  508  associated with the control port assembly  488  will be disposed in the recess  268  associated with the control port slot  264 . 
     With the extracorporeal tubing circuit  10  and the blood processing vessel  352  loaded in the above-described manner, the circuit  10  and vessel  352  are pressure tested to verify that there are no leaks. The donor/patient  4  is then fluidly interconnected with the extracorporeal tubing circuit  10  (by inserting an access. needle  32  into the donor/patient  4 ). Moreover, the anticoagulant tubing  54  is primed between the anticoagulant supply (which interfaces with the spike drip member  52 ) and the manifold  48 . Furthermore, blood return tubing  28  is primed with blood from the donor/patient  4  by running the blood return peristaltic pump  1090  pump in reverse to draw blood from the donor/patient  4 , through the blood return tubing  28 , and into the reservoir  150  until blood is detected by the low level sensor  1320 . 
     The blood processing vessel  352  must also be primed for the apheresis procedure. In one embodiment, a blood prime may be utilized in that blood will be the first liquid introduced into the blood processing vessel  352 . The flow of blood from the donor/patient  4  to the extracorporeal tubing circuit  10  is initiated with the centrifuge rotor assembly  568  rotating the channel housing  204  at a rotational velocity of from about 150 RPM to about 250 RPM for a rotor diameter of about 10″, and typically about 200 RPM. This lower rotational velocity not only reduces the potential for air locks developing the in the blood processing vessel  352 , but also minimizes any preheating of the blood processing vessel  352 . The rotational velocity in this “first stage” need not be fixed, but may vary. 
     Once the flow of blood reaches the blood processing vessel  352 , the rotational speed of the channel housing  204  is increased from about 1,500 RPM to about 2,500 RPM for a rotor diameter of about 10″, preferably about 2000 RPM, such that blood being provided to the blood processing vessel  352  will be separated into the various blood component types even during the priming procedure. Once again, in this “second stage”, the rotational velocity during need not be fixed, but may vary. In order for a blood prime to be successful, a flow must be provided to the control port assembly  488  before any RBCs flows beyond the RBC dam  232  in a clockwise direction. This is again provided by the configuration of the channel  208 . 
     Importantly, during this “second stage” of the blood priming procedure, air present in the blood processing vessel  352  is removed from the blood processing vessel  352  and due to the noted rotational velocities in this “second stage”, the potential for air locks is also reduced. More specifically, air which is present in the blood processing vessel  352  is less dense than the whole blood and all of its blood component types. As noted above, the radially inwardmost portion of the inner channel wall  212  is at the intersection between the plasma outlet slot  256  and the inner channel wall  212 . Consequently, the air present in the blood processing vessel  352  collects near the plasma outlet port  456  and is removed from the blood processing vessel  352  through the plasma outlet tubing  476 , and is provided to the vent bag  114 . 
     When the blood processing vessel  352  contains blood and/or blood components throughout its entirety, the rotational velocity of the channel housing  204  is increased to its normal operation speed from about 2,750 RPM to about 3,250 RPM for a rotor diameter of about 10″, and preferably about 3,000 RPM. This completes the blood priming procedure. 
     During the above-noted blood priming procedure, as well as throughout the remainder of the apheresis procedure, blood component types are separated from each other and removed from the blood processing vessel  352  on a blood component type basis. At all times during the apheresis procedure, the flow of whole blood is provided to the blood processing vessel  352  through the blood inlet port assembly  416  and is directed to the first stage  312 . The control port dam  280  again reduces the potential for blood flowing in a counterclockwise direction in the channel  208 . 
     In the first stage  312 , blood is separated into a plurality of layers of blood component types including, from the radially outermost layer to the radially innermost layer, RBCs, WBCs, platelets, and plasma. As such, the RBCs sediment against the outer channel wall  216  in the first cell separation stage  312 . By configuring the RBC dam  232  such that it is a section of the channel  208  which extends further inwardly toward the rotational axis  324  of the of the channel housing  204 , this allows the RBC dam  232  to retain separated red blood cells in the first stage  312 . 
     Separated RBCs are removed from the first stage  312  utilizing the above-noted configuration of the outer channel wall  216  which induces the RBCs to flow in a counterclockwise direction (e.g., generally opposite to the flow of blood through the first cell separation stage  312 ). That is, the portion of the channel  208  proximate the RBC outlet port assembly  516  is disposed further from the rotational axis  324  of the channel housing  204  than that portion of the channel  210  proximate the RBC dam  232 . As such, separated RBCs flow through the first stage  312  in a counterclockwise direction along the outer channel wall  216 , past blood inlet port assembly  388  on the blood processing vessel  352 , and to an RBC outlet port assembly  516 . Since the vertical slot  404  of the blood inlet port  392  is substantially parallel with the inner channel wall  212 , the outer channel wall  216 , the inner sidewall  372  of the blood processing vessel  352  and the outer sidewall  376  of the blood processing vessel  352 , since it directs the flow of blood in a clockwise direction in the channel  208  and thus toward the RBC dam  232 , since it is disposed proximate the inner channel wall  212 , the introduction of blood into the blood processing vessel  352  does not substantially affect the flow of RBCs along the outer channel wall  216 . Consequently, RBCs effectively flow undisturbed past the blood inlet port  392  and to the RBC outlet port assembly  516  for removal from the blood processing vessel  352 . These RBCs may either be collected and/or provided back to the donor/patient  4 . 
     Platelets are less dense then RBCs and are thus able to flow beyond the RBC dam  232  and to the platelet collect well  236  in platelet-rich plasma where they are removed from the blood processing vessel  352  by the platelet collect port assembly  416 . Again, the blood processing vessel  352  via the support  428  and the outer channel wall  216  collectively define the platelet collect well  236  when the blood processing vessel  352  is pressurized. That is, part of the platelet collect well  236  is defined by the lower face  240  and side faces  244 ,  248  formed in the outer channel wall  216 , while the remainder thereof is defined by the second face  436  of the support  428  when the support  428  is moved into a predetermined position within and against portions of platelet support recess  249  upon pressurization of the blood processing vessel  352 . 
     Platelet-poor plasma is less dense than the platelets and continues to flow in a clockwise direction through the second stage  316  to the plasma outlet port assembly  452  where at least some of the plasma is removed from the blood processing vessel  352 . This plasma may be collected and/or returned to the donor/patient  4 . However, some of the plasma flow continues in the clockwise direction into and through the third stage  320  to the control port assembly  488  to provide for automatic control of the location of the interface between the RBCs and platelets in the above-described manner. 
     Graphical Computer Interface 
     In order to assist an operator in performing the various steps of the protocol being used in an apheresis procedure with the apheresis system  2 , the apheresis system  2  further includes a computer graphical interface  660  illustrated in FIG.  1 . The following description describes an interface for use by an English language speaking operator. For other operations and/or languages, the textual portions of the interface would, of course, be adapted accordingly. The graphical interface  660  includes a computer display  664  which has “touch screen” capabilities. Other appropriate input devices (e.g., keyboard) may also be utilized alone or in combination the touch screen. For example, a pump pause and a centrifuge stop button of the well known membrane type may be provided. The graphics interface  660  not only allows the operator to provide the necessary input to the apheresis system  2  such that the parameters associated with operation of the apheresis system may be determined (e.g,. data entry to allow determination of various control parameters associated with the operation of the apheresis system  2 ), but the interface  660  also assists the operator by providing pictorials of at least certain steps of the apheresis procedure. Moreover, the interface  660  also effectively conveys the status of the apheresis procedure to the operator. Furthermore, the interface  660  also may be used to activate standardized corrective actions (i.e., such that the operator need only identify the problem and indicate the same to the interface  660  which will then direct the apheresis system  2  to correct the same). 
     Referring to  FIG. 26 , at the start of an apheresis procedure a master screen  696  is displayed to the operator on the display  664 . The master screen  696 , as well as each of the screens displayed to the operator by the interface  600 , includes a status bar  676 . The status bar  676  includes a system prep icon set  700 . The system prep icon set  700  includes a load icon  704  (representing the shape of blood component separation device  6 ) with a downwardly extending arrow which collectively pictorially conveys to the operator that the disposable set  8  must be loaded onto the blood component separation device  6 . The word “LOAD” is also positioned below the load icon  704  to provide a short textual instruction to the operator of the required action(s). 
     The system prep icon set  700  also includes an information icon  708  (representing the shape of an open filing folder) which pictorially conveys to the operator that certain information relating to the donor/patient  4 , the procedure protocol, and/or the blood component separation device  6  must be obtained and entered. This information may be utilized by the apheresis system  2  to calculate one or more of the parameters associated with the apheresis procedure (e.g., inlet flow rate to the blood processing vessel  352 ) and/or to generate predicted yields of one or more blood component types (e.g., the amount of a certain blood component type which is anticipated to be collected based upon certain parameters such as donation time). The word “INFO” is also positioned below the information icon  708  to provide a short textual instruction to the operator of the required action(s). The information icon  708  is also positioned to the right of the load icon  704  to indicate to the operator that it is preferred, although not required, to perform the step(s) associated with the information icon  708  after the step(s) associated with the load icon  704  have been completed. 
     The status bar  676  also includes a collection icon set  712 . The collection icon set  712  includes a donor/patient prep icon  716  (representing the shape of the donor/patient  4 ) which pictorially conveys to the operator that the donor/patient  4  must now be fluidly interconnected with the blood component separation device  6 . The word “PREPARE” is also positioned below the donor/patient prep icon  716  to provide a short textual instruction to the operator of the required action(s). The donor/patient prep icon  716  is also positioned to the right of the information icon  708  to indicate to the operator that the step(s) associated with the donor/patient prep icon  716  may only be performed after the step(s) associated with the load icon  704  and the information icon  708  have been completed. 
     The collection icon set  712  also includes a donate icon  720  with a laterally extending arrow which collectively pictorially conveys to the operator that the actual collection procedure may be initiated and that the step(s) to initiate this action should now be performed. The word “DONATE” is also positioned below the donate icon  720  to provide a short textual instruction to the operator of the required action(s). The donate prep icon  720  is also positioned to the right of the donor/patient prep icon  716  to indicate to the operator that the step(s) associated with the donate icon  720  must be performed after the step(s) associated with the donor/patient prep icon  716  have been completed. 
     The status bar  676  also includes an unload icon  724  (representing the shape of the blood component separation device  6 ) and a generally upwardly extending arrow which collectively pictorially convey to the operator that the disposable set must now be removed from the blood component separation device  6 . The word “UNLOAD” is also positioned below the unload icon  724  to provide a short textual instruction to the operator of the required action(s). The unload icon  724  is also positioned to the right of the donate icon  720  to indicate to the operator that the step(s) associated with the unload icon  724  must be performed after the step(s) associated with the donate icon  720  have been completed. 
     The system preparation icon set  700 , collection icon set  712 , and unload icon  724  in the status bar  676  sequentially set forth certain basic steps for the apheresis procedure. That is, the left to right positioning of the various icons conveys to the operator the desired/required order in which the step(s) associated with the icons should/must be performed. Moreover, the individual icons  704 ,  708 ,  716 ,  720 ,and  724  are also utilized to convey the status of the apheresis procedure to the operator via three-way color differentiation (i.e., one status per color) and/or by three-way shade differentiation. “Shades” includes variations of a given color and also encompasses using variations based upon being “lighter” and/or “darker” (e.g., using light gray, medium gray, and dark gray). That is, a “gray-scale” technique may also be utilized and is encompassed by use of color and/or shade differentiation. 
     The first status conveyed to the operator by the icons in the status bar  676  is that the step(s) associated with respective icon are not ready to be performed. That is, the performance of this step(s) would be premature. This first status is conveyed to the operator by displaying the associated icon in a first color, such as white. The corresponding textual description may also be presented in this first color as well. As noted, a first “shade” may also be utilized to convey this first status as well. 
     The second status conveyed to the operator by the icons in the status bar  676  is that the step(s) associated with the respective icon is either ready for execution or is in fact currently being executed. That is, an indication is provided to the operator that performance of this step(s) of the apheresis procedure is now timely. This second status is conveyed to the operator by displaying the associated icon in a second color, such as yellow. The corresponding textual description may also be presented in this second color as well. As noted, second “shade” may also be utilized to convey this second status as well. 
     The third status conveyed to the operator by the icons in the status bar  676  is that the step(s) associated with the respective icon has been executed. That is, an indication is provided to the operator that performance of this step(s) of the apheresis procedure has been completed. This third status is conveyed to the operator by displaying the associated icon in a third color, such as gray. The corresponding textual description may also be presented in this third color as well. As noted, third “shade” may also be utilized to convey this third status as well. 
     Based upon the foregoing, it will be appreciated that significant information is conveyed to the operator by merely viewing the status bar  676 . For instance, the operator is provided with a pictorial graphic indicative of the fundamental steps of an apheresis procedure. Moreover, the operator is provided with a textual graphic indicative of the fundamental steps of an apheresis procedure. Furthermore, the operator is provided with a desired/required order in which these steps should/must be performed. Finally, the operator is provided with the status of the apheresis procedure via the noted three-way color/shade differentiation. 
     The master screen  696 , as well all other screens displayed to the operator by the interface  660  during an apheresis procedure, also include a work area  688 . The work area  688  provides multiple functions. Initially, the work area  688  displays additional information (pictorially and textually in some instances) on performing the apheresis procedure to the operator (e.g., certain additional substeps of the apheresis procedure, addressing certain “conditions” encountered during the apheresis procedure). Moreover, the work area  688  also displays additional information on the status of the apheresis procedure to the operator. Furthermore, the work area  688  also provides for operator interaction with the computer interface  660 , such as by allowing/requiring the operator to input certain information. 
     Continuing to refer to  FIG. 26 , the work area  688  of the master screen  696  displays a load system button  728  and a donor/patient info button  780 . The operator may touch either of these buttons  728 ,  780  (i.e., since the display  696  has “touch screen” capabilities) to generate further screens for providing information to the operator and/or to facilitate the inputting of information to the computer interface  660 . The operator may initially touch either the load system button  728  or the donor/patient info button  780  at the start of an apheresis procedure. That is, the order in which the step(s) associated with the load system button  728  are performed in relation to the apheresis step(s) associated with the donor/patient info button  780  are performed is not important (i.e., the steps associated with the load system-button  728  may be performed before or after the steps associated with the donor/patient info button  780 ). The apheresis procedure will be described with regard to the operator electing to initially activate the load system button  728  via the touch screen feature. 
     Activation of the load system button  728  generates a loading procedure screen  732  on the computer display  664  which is illustrated in FIG.  27 . The loading procedure screen  732  displays multiple pictorials to the operator in the work area  688  which relate to the steps which need to be performed to prepare the blood component separation device  6  for an apheresis procedure. Initially, a hang pictorial  736  is displayed which pictorially conveys to the operator that the various bags (e.g., an AC bag(s) (not shown), plasma collect bag(s)  94  platelet collect bag(s)  84 ) need to be hung on the blood component separation device  6  and generally how this step may be affected by the operator. The word “HANG” is also positioned above the hang pictorial  736  to provide a short textual instruction to the operator of the required action(s). Consequently, there are two different types of graphical representations provided to the operator relating to a specific operator action which is required to prepare the blood component separation device  6  for the apheresis procedure. Moreover, the hang pictorial  736  is disposed on the left side of the loading procedure screen  732  which indicates that this is the first step or substep associated with the load icon  704 . In order to provide further indications of the desired order to the operator, the number “1” is also disposed adjacent to the word “HANG.” 
     A focus color (e.g., yellow) or shade may be used to direct the operator&#39;s attention to specific areas of the machine or screen. The loading procedure screen  732  also displays an insert pictorial  740  to the operator in the work area  688 . The insert pictorial  740  pictorially conveys to the operator that the cassette assembly  110  needs to be mounted on the pump/valve/sensor assembly  1000  of the blood component separation device  6  and generally how this step may be affected by the operator. The word “INSERT” is also positioned above the insert pictorial  740  to provide a short textual instruction to the operator of the required action(s). The insert pictorial  740  is also positioned to the right of the hang pictorial  736  to indicate to the operator that it is preferred, although not required, to perform the step(s) associated with the insert pictorial  740  after the step(s) associated with the hang pictorial  736  have been completed. In order to provide further indications of the desired order to the operator, the number “2” is also disposed adjacent to the word “INSERT.” 
     The loading procedure screen  732  also displays a load pictorial  744  to the operator in the work area  688 . The load pictorial  744  pictorially conveys to the operator that the blood processing vessel  352  needs to be loaded into the channel  208  of the channel housing  204  on the centrifuge rotor assembly  568  and generally how this step may be affected by the operator. The word “LOAD” is also positioned above the load pictorial  744  to provide a short textual instruction to the operator of the required action(s). The load pictorial  744  is also positioned to the right of the insert pictorial  740  to indicate to the operator that it is preferred, although not required, to perform the step(s) associated with the load pictorial  744  after the step(s) associated with the insert pictorial  740  have been completed. In order to provide further indications of the desired order to the operator, the number “3” is also disposed adjacent to the word “LOAD.” 
     Finally, the loading procedure screen  732  displays a close pictorial  748 . The close pictorial  748  pictorially conveys to the operator that the door of the blood component collection device housing the centrifuge rotor assembly  568  needs to be closed and generally how this step may be affected by the operator. The word “CLOSE” is also positioned above the close pictorial  748  to provide a short textual instruction to the operator of the required action(s). The close pictorial  748  is also positioned to the right of the load pictorial  744  to indicate to the operator that it is required to perform the step(s) associated with the close pictorial  748  after the step(s) associated with the load pictorial  744  have been completed. In order to provide further indications of the desired order to the operator, the number “41” is also disposed adjacent to the word “CLOSE.” 
     In summary, the work area  688  of the loading procedure screen  732  not only conveys to the operator what type of steps must be performed for this aspect of the apheresis procedure and generally how to perform these steps, the work area  688  of the loading procedure screen  732  also specifies the order in which these steps should be performed by two “methods.” Initially, the pictorial graphics  736 ,  740 ,  744  and  748  are sequentially displayed in left-to-right fashion to specify the desired/required order of performance. Moreover, the four steps are also numerically identified next to their associated one-word textual description. 
     In the event that the operator requires additional guidance with regard to any of the steps presented on the loading procedure screen  732 , the operator may touch the help button  692  provided on the loading procedure screen  732 . This may display a menu of screens which the operator may view and/or may sequentially present a number of help screens associated with the loading procedure screen  732 .  FIG. 28  illustrates a help screen  764  which relates to the loading of the blood processing vessel  352  into the channel  208  on the channel housing  204 . Note that in the case of the help screen  764  the upper portion of the work area  688  of the loading procedure screen  732  is retained (i.e., the one word textual descriptions of the four basic steps and the associated numerical ordering identifier). Moreover, the help screen  764  provides the operator with more detail, in the nature of additional pictorials, regarding one or more aspects of the particular step(s) or substep or in this case on the loading of the blood processing vessel  352  in the channel  208 . Once the operator exits the help screen  764  via touching the continue button  752  on the help screen  764 , the operator is returned to the loading procedure screen  732  of FIG.  22 . Various other screens in the graphics interface  660  may include a help button  692  to provide this type of feature. 
     When the operator has completed each of the four steps or substeps presented on the loading procedure screen  732 , the operator touches the continue button  752  on the bottom of the loading procedure screen  732 . In the event that during the time in which the operator is performing the steps or substeps associated with the loading procedure screen  732  the operator wants to return to the begin operations screen  696 , the operator may touch the display screen  664  in the area of the return button  756 . The return button  756  may be provided on various of the screens to return the operator to the previous screen when acceptable. Moreover, in the event that during the time in which the operator is performing the steps or substeps associated with the loading procedure screen  732  the operator wants to terminate the loading procedure, the operator may touch the display screen  664  in the area of the exit load or cancel button  760 . The exit load or cancel button  760  may be provided on various of the other screens to provide the operator with the option to exit the loading procedure where appropriate. 
     When the operator touches the continue button  752  on the loading procedure screen  732 , a disposable pressure test screen  768  is produced on the display  664 , one embodiment of which is illustrated in FIG.  29 . Generally, the disposable pressure test screen  768  pictorially conveys to the operator that certain steps must be undertaken to allow for pressure testing of the disposable set  8  and how this may be affected by the operator. In this regard, a donor/patient access line clamp pictorial  769  pictorially conveys to the operator that the blood removal/return tubing assembly  20 , specifically the interconnect tubing  38 , to the donor/patient  4  must be sealed off. A donor/patient sample line clamp pictorial  770  pictorially conveys to the operator that the sample line of the sample subassembly  46  must also be sealed off as well. When the operator has completed these steps, the operator touches the continue button  752  and a test in progress screen  772  is displayed to the operator to pictorially and textually convey to the operator that the testing procedure is underway and such is illustrated in FIG.  30 . 
     After the pressure test of the disposable set  8  is complete, an AC interconnect screen  776  is produced on the display  664  and one embodiment of which is illustrated in FIG.  31 . The AC interconnect screen  776  pictorially conveys to the operator that the anticoagulant tubing assembly  50 , specifically the spike drip member  52 , of the extracorporeal tubing circuit  10  needs to be fluidly interconnected with the AC bag (not shown), as well as generally how this step may be affected by the operator. When this step has been completed by the operator, the operator touches the continue button  752  on the display  664 . 
     The AC interconnect is the last of the steps associated with the load icon  704  such that the operator is returned to the master screen  696 . The master screen  696  now reflects the current status of the apheresis procedure and is illustrated in FIG.  32 . That is, the color or shade of the load icon  704  is changed from the second color/shade to the third color/shade to that which indicates that all steps associated with the load icon  704  have been completed by the operator. Moreover, a status check  730  appears on the load system button  728  in the work area  688  as well. The load system button  728  is grayed out for the duration of the procedure and thus indicates that the system setup may not be repeated. Consequently, two different types of indications are provided to the operator of the current status regarding the loading procedure. The change in status of the donor/patient data entry portion of the apheresis procedure is also updated by presenting the information icon  708  in the status bar  676  in the second color/shade which indicates to the operator that it is now appropriate to begin this aspect of the apheresis procedure. 
     The operator enters the information entry portion of the apheresis procedure by touching the info button  780  on the display  664  of the master screen  696 . This produces a donor/patient data screen  788  on the display  664 , one embodiment of which is illustrated in FIG.  33 . The donor/patient data screen  788  which includes a sex-type button  792 , a height button  796 , and a weight button  808 . The operator may indicate the sex of the donor/patient  4  by touching the relevant portion of the split sex-type button  792  and the selected sex may be displayed to the operator (e.g, via color differentiation). Moreover, the operator may enter the height and weight of the donor/patient  4  by touching the height button  796  and the weight button  808 , respectively. When the height button  796  and weight button  808  are engaged by the operator, a keypad  804  is superimposed over the button whose information is to be entered as illustrated in FIG.  34 . The keypad  804  may be used to enter the donor/patient&#39;s  4  height and weight and this information may also be displayed to the operator. 
     The information entered by the operator on the donor/patient data screen  788  is used to calculate, for instance, the donor/patient&#39;s  4  total blood volume which is presented in a total blood volume display  790  on the donor/patient data screen  788 . The donor/patient&#39;s  4  total blood volume may be utilized in the determination of various parameters associated with the apheresis procedure and/or in the estimation of the number of blood components which are anticipated to be collected in the procedure. When the operator has completed these data entry procedures, the operator touches the continue button  752  which will be displayed on the bottom of the donor/patient data screen  788  after all requested information has been input. 
     A lab data entry screen  810  is generated on the computer display  664  after the steps associated with the donor/patient data screen  788  have been completed and as indicated by the operator, one embodiment of which is illustrated in FIG.  35 . The lab data entry screen  810  requests the operator to enter the time for the collection procedure by touching a donation time button  840  which results in the keypad  804  being superimposed over the donation time button  832  (not shown). The donation time entered by the operator will be displayed on a time display  860 , which specifies the duration for the procedure. Moreover, the donation time entered by the operator may also be displayed on the donation time button  840 . The donation time is used, for instance, to predict the number of the blood component(s) (e.g., platelets, plasma) which is anticipated to be collected during the procedure. 
     The lab data screen  810  also prompts the operator to enter the donor/patient&#39;s  4  hematocrit by touching a hematocrit button  842 . This results in the keypad  804  being superimposed over the hematocrit button  842 . The operator may then enter the donor/patient&#39;s  4  hematocrit (e.g., as determined via laboratory analysis of a blood sample from the donor/patient  4 ) and such may be displayed on the hematocrit button  842 . The donor/patient&#39;s  4  hematocrit is also utilized by one or more aspects of the apheresis procedure. 
     The lab data screen  810  also prompts the operator to enter the donor/patient&#39;s  4  platelet precount by touching a platelet precount button  843 . This results in the keypad  804  being superimposed over the platelet precount button  843 . The operator may then enter the donor/patient&#39;s  4  platelet precount (e.g., as determined via laboratory analysis of a blood sample from the donor/patient  4 ) and such may be displayed on the platelet precount button  843 . The donor/patient&#39;s  4  platelet precount is also utilized by one or more aspects of the apheresis procedure. 
     Once the operator has entered all of the requested information, the operator touches the continue button  752  which returns the operator to the master screen  696  which now reflects the current status of the apheresis procedure and as illustrated in FIG.  36 . Since all of the steps associated with the information icon  708  have now been completed, the color/shade of the information icon  708  is changed from the second color/shade to the third color/shade to convey to the operator that all associated steps have been completed. Moreover, a status check  784  appears on the donor/patient info button  780  in the work area  688  as well. Consequently, two different types of indications are provided to the operator of the current status of this aspect of the apheresis procedure. Moreover, the change in status of the collection icon set  712  of the apheresis procedure is updated by changing the color/shade of the donor/patient prep icon  716  in the status bar  676  from the first color/shade to the second color/shade. A run button  802  is also now presented on the master screen  696  such that the steps associated with the collection icon set  712  may now be undertaken and further such that. pictorial representations of the same may be provided to the operator. 
     The initial screen for steps associated with the collection icon set  712  is a donor/patient prep screen  812 A which is illustrated in FIG.  37 . The donor/patient prep screen  812 A pictorially conveys to the operator the steps which must be undertaken in relation to the donor/patient  4  being fluidly interconnected with the blood component separation device. Initially, a donor/patient connect pictorial  816  is displayed which pictorially conveys to the operator that an access needle  32  must be installed on the donor/patient  4 , as well as generally how this step may be affected by the operator. The word “CONNECT” is also positioned above the donor/patient connect pictorial  816  to provide a short textual instruction to the operator of the required action(s). The donor/patient connect pictorial  816  is disposed on the left side of the donor/patient prep screen  812 A which indicates that this is the first step or substep associated with the donor/patient prep icon  716 . In order to provide further indications of the desired order to the operator, the number “1” is also disposed adjacent the word “CONNECT.” 
     The donor/patient prep screen  812 A also displays an open pictorial  820  on the display  664 . The open pictorial  820  pictorially conveys to the operator that the clamps  42  in the interconnect tubing  38  and the clamp in the tubing of the sample subassembly  46  must be removed, as well as generally how these steps may be affected by the operator. The word “OPEN” is also positioned above the open flow pictorial  820  to provide a short textual instruction to the operator of the required action(s). The open pictorial  820  is disposed to the right of the donor/patient connect pictorial  816  which indicates that the step(s) associated with the open pictorial  820  should be performed only after the step(s) associated with the donor/patient connect pictorial  816  have been completed. In order to provide further indications of the desired order to the operator, the number “2” is also disposed adjacent the word “OPEN.” 
     The donor/patient prep screen  812 A also displays a flow pictorial  824  on the display  664 . The flow pictorial  824  pictorially conveys to the operator that there should now be a flow of blood from the donor/patient  4  into the blood removal/return tubing assembly  20 , specifically the blood removal tubing  22 , and in the sample tubing of the sample subassembly  46 . The word “FLOW” is also positioned above the flow pictorial  824  to provide a short textual description to the operator of what should be occurring at this time. The flow pictorial  824  is disposed to the right of the open pictorial  820  which indicates that the conditions associated with the flow pictorial  824  should occur only after the step(s) associated with the open pictorial  820  have been completed. In order to provide further indications of the desired order to the operator, the number  113  is also disposed adjacent the word “FLOW.” 
     In summary, the work area  688  of the donor/patient prep screen  812 A not only conveys to the operator what type of steps must be performed for this aspect of the apheresis procedure and how to generally perform these steps, but also specifies the order in which these steps should be performed by two methods. Initially, the pictorial graphics  816 ,  820 , and  824  are sequentially displayed in left-to-right fashion. Moreover, the three steps are also numerically identified next to their associated one-word textual description. 
     Once the operator completes all of the steps associated with the donor/patient prep screen  812 A, the operator touches the continue button  752  which results in the display of a second donor/patient prep screen  812 B as illustrated in FIG.  38 . The donor/patient prep screen  812 B includes a close pictorial  828  which pictorially conveys to the operator to terminate the flow of blood from the donor/patient  4  to the sample bag of the sample subassembly  46  by clamping the sample line and generally how this step may be affected by the operator. The word “CLOSE” is also positioned above the close pictorial  828  to provide a short textual instruction to the operator of the required action(s). The close pictorial  828  is disposed on the left side of the donor/patient prep screen  812 B which indicates that this is the first step or substep associated with the donor/patient prep screen  812 B. In order to provide an indication that this is in fact, however, the fourth step associated with the donor/patient preps, the number “4” is also disposed adjacent the word “CLOSE.” 
     The donor/patient prep screen  812 B also displays a seal pictorial  832  on the display  664 . The seal flow pictorial  832  pictorially conveys to the operator that the sample line of the sample subassembly  46  should now be sealed off and generally how this step may be affected by the operator. The word “SEAL” is also positioned above the seal pictorial  832  to provide a short textual instruction to the operator of the required action(s). The seal pictorial  832  is disposed to the right of the close pictorial  828  which indicates that the step(s) associated with the seal pictorial  832  should be performed only after the step(s) associated with the close pictorial  828  have been completed. In order to provide further indications of the desired order to the operator, the number “5” is also disposed adjacent the word “SEAL” to indicate that this is actually the fifth step associated with the donor/patient preps. 
     In summary, the work area  688  of the donor/patient prep screen  812 B not only conveys to the operator what type of steps must be performed for this aspect of the apheresis procedure and how to generally perform these steps, the work area  688  of the donor/patient prep screen  812 B also specifies the order in which these steps should be performed by two methods. Initially, the pictorials  828 ,  832 , and  836  are sequentially displayed in left-to-right fashion. Moreover, the four steps are also numerically identified next to their associated one-word textual description. 
     Once the operator completes all of the donor/patient preps, the operator may touch the start prime button  846  on the donor/patient prep screen  812 B which initiates the above-described blood prime of the extracorporeal tubing circuit  10  and blood processing vessel  352  and which results in the display of the run screen  844  illustrated in FIG.  39 . The run screen  844  primarily displays information to the operator regarding the apheresis procedure. For instance, the run screen  844  includes a blood pressure display  848  (i.e., to convey to the operator the donor/patient&#39;s extracorporeal blood pressure), a platelet collect display  852  (i.e., to convey to the operator an estimate of the number of platelets which have been currently collected), a plasma collect display  856  (i.e., to convey to the operator the amount of plasma which has been currently collected), and a time display  860  (e.g., both the amount of time which has lapsed since the start of the collection procedure (the left bar graph and noted time), as well as the amount of time remaining in the collection procedure (the right bar graph and noted time). A control button (not shown) may be provided to toggle between the time remaining display and the start and stop time display. 
     The run screen  844  may also display, in the case of a single needle procedure (i.e., where only one needle is utilized to fluidly interconnect the donor/patient  4  with the blood component separation device  6 ), whether blood is being withdrawn from the donor/patient  4  (e.g., by displaying “draw in progress”) or is being returned to the donor/patient  4  (e.g., by displaying “return in progress”). This information may be useful to the donor/patient  4  in that if the donor/patient  4  is attempting to maintain a certain blood pressure by squeezing an article to assist in removal of blood from the donor/patient  4 , the donor/patient  4  will be provided with an indication to suspend these actions while blood is being returned to the donor/patient  4 . 
     During the apheresis procedure, certain conditions may be detected by the apheresis system  2  which would benefit from an investigation by the operator. If one of these types of conditions is detected, an appropriate alarm screen is displayed to the operator. One embodiment of an alarm screen  864  is illustrated in FIG.  40 . Initially, the alarm screen  864  textually conveys a potential problem with the system  2  via a problem graphic  868 . The text may be useful in ensuring that the operator understands the problem. The alarm screen  864  also includes an action pictorial  872  which graphically conveys to the operator the action which should be taken in relation to the problem. These are actions which may be difficult or impossible for the system  2  to take itself. Finally, the alarm screen includes an inspection results array  876  which allows the operator to indicate the results of the inspection. In the illustrated embodiment, the array  876  includes a blood leak button  906 , a moisture button  908 , and a no leak button  910 . 
     Depending upon the selection made by the operator on the inspection results array  876 , additional questions may be posed to the operator in further screens which require further investigation and/or which specify the desired remedial action. For instance, the supplemental alarm screen  878  of  FIG. 41  may be generated by the operator touching the moisture button  908  on the alarm screen  864 . The supplemental alarm screen  878  includes a remedial action pictorial  912  and remedial action text  914  to convey to the operator how to correct the identified problem. 
     The computer interface  660  may also allow the operator to initiate some type of corrective action based upon observations made by and/or conveyed to the operator. For instance, various screens of the interface  660  may include a trouble shooting button  898  which will generate one or more trouble shooting screens. These trouble shooting screens may include menus or the like to allow the operator to indicate what type of potential problem exists. 
     One embodiment of a trouble shooting screen  880  is presented in FIG.  42 . The trouble shooting screen  880  includes a donor/patient tingling button  922 . This button  922  would be utilized by the operator to attempt to remedy the effects of AC on the donor/patient  4  in response to the donor/patient indicating a “tingling sensation” or, alternatively, “AC reaction.” When the operator hits the “down arrow” of the donor/patient tingling button  922 , the system  2  attempts to correct the condition in a predetermined manner (i.e., a predetermined protocol is employed preferably this protocol does not require operator actions or decisions). Once the tingling sensation no longer exists, the operator may use the “up arrow” button to return the bar on the donor/patient tingling button  922  to its original position. 
     The trouble shooting screen  880  also includes a clumping button  924 . This button  924  would be utilized by the operator if any undesired clumping of the collected product (e.g., platelets) was observed. When the operator hits the “down arrow” of the clumping button  924 , the system  2  attempts to correct the condition in a predetermined manner (i.e., a predetermined protocol is employed and preferably this protocol does not require operator actions or decisions). Once the clumping is no longer observed by the operator, the operator may use the “up arrow” button to return the bar on the clumping button  924  to its original position. 
     The trouble shooting screen  880  may also include a spillover button  916  and an “air in plasma line” button  918 . The spillover button  916  would be engaged by the operator if red blood cells were observed in the platelet outlet tubing  66 , in the platelet collect bag  84 , and/or flowing beyond the RBC dam  232 . Activation of the spillover button  916  via the touch screen capabilities would result in the system  2  using a predetermined and preferably automatic protocol is performed by the system  2  to correct this condition. Similarly, if the operator observes air in the plasma line  918  and engages the button  918 , the system  2  again will preferably automatically employ a predetermined protocol to correct this condition. 
     The “other problem button”  920  may be utilized to generate further trouble shooting screens to list further problems which may occur in the apheresis procedure. Again, preferably upon the operator touching the associated button indicative of a particular problem, a predetermined protocol will be preferably automatically employed to attempt to correct the same. 
     Upon completion of the collection portion of the apheresis procedure, the rinseback screen  884  is produced on the display  664  which indicates that the rinseback procedure will now be performed and which is illustrated in FIG.  44 . Once the rinseback is completed, the color/shade of the donate icon  720  changes from the second color to the third color/shade to indicate that all steps associated with this aspect of the apheresis procedure have been completed. Moreover, the color/shade of the unload icon  724  will also change from the first color/shade to the second color/shade to indicate to the operator that the step(s) associated therewith may now be performed. 
     Upon completion of the rinseback, a run finish screen may be produced on the display  664  to provide the final collection data as illustrated in  FIG. 43  (e.g., the associated yields of platelets and plasma collected during the procedure) as well as the fact that the procedure is over (e.g., by displaying “run completed”). The operator may then touch the continue button  752 . 
     Once the rinseback procedure is completed, an unload screen  892  will be presented on the display  664  and is illustrated in FIG.  45 . The unload screen  892  may sequentially display a number of pictorials to the operator to convey the steps which should be completed to terminate the procedure. For instance, a seal/detach pictorial  900  may be initially displayed on the unload screen  892  to pictorially convey to the operator that the tubes leading to the platelet and plasma collect bag(s)  84 ,  94  should each be sealed such that the platelet and plasma collect bag(s)  84 ,  94  respectively, may be removed. Once the operator touches the continue button  752 , a disconnect pictorial  902  may be presented on the unload screen  892  to pictorially convey to the operator that the access needle  32  should be removed from the donor/patient  4 . Once the operator touches the continue button  752 , a remove pictorial  904  is presented on the unload screen  892  to pictorially convey to the operator that the disposable set  8  should be removed from the blood component separation device  6  and disposed of properly. 
     The computer interface  660  provides a number of advantages. For instance, the computer interface  660  utilizes a three-way color/shade differentiation to conveniently convey the status of the apheresis procedure to the operator. An icon is presented in one color/shade if the step(s) associated with the icon are not yet ready to be performed, while the icon is presented in another color/shade if the step(s) associated with the icon are ready to be performed or are being performed, while the icon is presented in yet another color/shade if the step(s) associated with the icon have been completed. Moreover, the computer interface  660  provides pictorials to the operator of at least certain of the steps of the apheresis procedure. Furthermore, the desired/required ordering of at least the fundamental steps of the apheresis procedure is conveyed to the operator. Finally, the interface  660  allows for correction of certain conditions, which after appropriate operator input, are remedied by the system  2  in accordance with a predetermined protocol. 
     The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described hereinabove are further intended to explain best modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.