CENTRIFUGE WITH MOVABLE MANDREL

Abstract: A liquid processing apparatus (10) for use in centrifugal apheresis in which whole blood is received from a donor, separated into therapeutic components and selectively collected. The apparatus (10) includes a processing chamber support system (14) for cooperating in controlling the volume of a variable-volume blood processing chamber during apheresis. The support system (14) is contructed to spin about a spin axis and is substantially symmetric about said axis. The elements of the support system (14) include a chamber cover (30) for receiving a variable-volume chamber (40). A mandrel (32) is provided for engaging the variable-volume chamber (40) and applying a conforming force to the chamber (40) by urging the chamber (40) toward the cover (30) and thereby causing the chamber (40) to conform to the shape of the cover (30). Thus the chamber (40) is positioned between the cover (30) and mandrel (32) during apheresis, and the cover (30) and mandrel (42) cooperate in controlling the volume and shape of the chamber (40). The apparatus (10) and chamber (40) define an annular blood volume having a blood sedimentation surface (52) and a cylindrical plasma volume (50) having a cylindrical blood/plasma interface. The area of the blood sedimentation surface is greater than the interface area so as to maximize blood cell separation while minimizing platelet separation during the red blood cell separation and collection.

Description: CENTRIFUGE WITH MOVABLE MANDREL BACKGROUND OF THE INVENTION This invention relates to a centrifugal liquid processing apparatus, and more particularly, to an im- proved apparatus for centrifugal apheresis, such as plas apheresis or plateletapheresis. In recent years the separation of whole blood into therapeutic components, such as red blood cells, platelets and plasma, and collection of those σompon- ents has increased significantly. The separation is generally achieved in a centrifuge and is referred to as centrifugal apheresis. In centrifugal processing, whole blood is de¬ livered to a processing chamber where the blood is σentrifugally separated into therapeutic components. The processing chamber is commonly bowl-shaped, rigid and disposable. Presently whole blood is taken from a donor at a donation site and is then transported in a ster- ile container to a central processing laboratory where it is processed for separation and collection of the therapeutic components. The apparatus used at the processing laboratory for centrifugal apheresis is bulky, expensive and usually not conducive for use at the donation site. However, on-site processing is becoming more popular since the time, handling and storage between donation and proces-sing can be minimized. Furthermore, thera¬ peutic component yield can be increased if processing for separation and collection is performed during do¬ nation. For example, in on-site processing greater quantities of platelets can be collected because greater quantities of whole blood can be processed for platelets ' and returned to the donor. Since the volume of blood being processed may vary and the chamber ' volume may vary during component separation and processing, the processing bowls and the appara¬ tus which cooperates with the bowls must be.capable of handling the varying volumes. In U.S. Patent Application, Serial No. filed on even date herewith and entitled "Flexible Disposable Centrifuge Chamber", there is disclosed a flexible, variable-volume, bowl-shaped chamber which can be used in on-site processing apparatus. It is the object of this invention to provide an apparatus for on-site centrifugal apheresis which is constructed for use in systems where the volume of biological fluids processed is variable. It is another object of this invention to pro¬ vide an apparatus for on-site apheresis which is con¬ venient to use and of a lower cost to manufacture. These and other objects of this invention will become apparent from the following description and ap¬ pended claims. SUMMARY OF THE INVENTION There is provided by this invention a centri- fugal liquid processing apparatus for use in the on- site processing of whole blood into therapeutic con¬ stituents by centrifugal apheresis (e.g., plasma- pheresis or plateletpheresis) . The apparatus is par¬ ticularly useful with a flexible, variable-volume, processing chamber and includes a chamber bowl or cover for receiving the processing chamber. A cham¬ ber-engaging mandrel is provided for engaging said chamber and causing the chamber to conform to the cover and for cooperation in controlling the volume of said chamber. The cover and mandrel are spun about a spin axis and the processing chamber spins there¬ with for separating the components. • Fluid conduits OMPI are provided for connecting the chamber to the donor and to external sites for the collection of. the thera¬ peutic components. The mandrel, cover and chamber cooperate to define a blood-collecting volume generally along the side walls of the chamber and a central plasma collec¬ ting volume at the base of the chamber. These vol¬ umes are substantially equal and remain equal as the total chamber volume changes. Furthermore, the chamber is configured so that the surface area at which red blood cells will separate is greater than the surface area of the red blood cell/ plasma interface. The result of the volume and surface area relationships is to maximize red blood cell (RBC) separation while minimizing platelet sedimentation back into the red blood cell bed or packed cell bed during RBC separation and collection. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a vertical, sectional view showing the basic elements of an on-site centrifugal apheresis apparatus, including a rotatable external housing and an internal chamber support system; FIGURE 2 is a vertical sectional view showing the housing in an open position and the processing chamber mounted on the mandrel; FIGURE 3 shows the chamber support system in the operative position; and FIGURE 4 shows the processing chamber being filled for separation. DESCRIPTION OF THE PREFERRED.-EMBODIMENT The System in General Referring now to Figure 1, an apparatus for centrifugal apheresis 10 generally is shown and in- eludes a rotatable external assembly or housing 12 and a rotatable inner chamber support assembly 14 which carries the variable-volume chamber and movable mandrel. The housing 12 is generally cylindrical in shape and includes top and bottom half sections 16 and 18 which are connected by hinge 20. The bottom section 18 is connected to a drive system 22, which spins the outer housing at a first predetermined speed about a spin axis A-A. Different types of drive systems are known in the art and can be employed. See U.S. Patents 3,986,442 Khoja et al and Re. 29,738 Adams for exemplary drive systems. The top section 16 carries the inner chamber support assembly 14, which is positioned within the outer housing 12 and aligned with the spin axis A-A for rotation with the outer housing 12. An inner assembly drive 23 is mounted to the top section 16 and supports the chamber and cooperating members via drive shaft 24. The inner assembly drive spins the inner assembly 14 in the same direction as the outer assembly 12, but at twice the rate. If the rate of rotation for the outer hous¬ ing is designated as one-omega (i.e., 1C ) , then the rate of rotation for the inner assembly is two-omega (2 ) ) in the same direction. Use of the 1 CJ/20J drive permits the entire apparatus to be connected to the stationary external blood sources and collection sites using conduits or stationary seals (i.e., non- rotating seals) . OMPI Systems which employ such drives and fluid connections * are disclosed in the previously identified patents as well as 4,108,353 Brown; 4,109,852 Brown et al; and 4,109,855 Brown et al. Furthermore, mechanical and electrical control systems are known for maintaining the 1C /2 U drive relationship. A control system designated by block diagram 26 is connected to both drives 22 and 23. The inner assembly includes an inverted cup-shaped chamber support plate 28, which carries the chamber bowl or cover 30 and.spring-biased cham¬ ber mandrel 32. A flexible, variable-volume, bowl- shaped chamber is positioned in the cover between the cover and mandrel, as best seen in Figures 2-4. A fluid conduit, which is sometimes referred to as an umbilicus 34, extends from the cover through the outer housing to a stationary external connection 36. The umbilicus can be either a single or multi-lumen tube. See, for example, 4,132,349 Khoja et al and 4,389,207 Bacehowski et al. The cover 30 is fixed to the chamber support plate 28 by a removable band 38 which releasably secures the cover to the support plate. Both the outer and inner housings are sub- stantially symmetric about the central spin axis A-A, and during operation, the chamber conforms to the shape of the mandrel and cover and assumes a generally axially symmetric shape. Mounting of the Chamber Referring to Figure 2, the processing chamber, which is a flexible, variable-volume, bowl-shaped member 40, is shown with a fluid communication port 42. * This port is to be located on the spin axis A-A and is referred to as the low-gravity (low-G) port. In some systems a port is also located at the radially outermost point and is referred to as the high-G port. In a distended shape the chamber has a bladder-like shape that can be formed to the bowl¬ like shape. In order to mount the chamber to the support assembly, the top section 16 of the outer housing is swung open about hinge 20 to an inverted horizontal position, the retainer band 38 is " removed, and the chamber bowl cover is removed as shown in Figure 2. Thereafter, a flexible, variable-volume chamber 40 is fitted to the mandrel 32 by rolling the chamber there¬ on. This chamber 40 has been fabricated from two heat- sealed and vacuum-formed polyvinylchloride sheets. The sealing flange 44 is shown engaging the support plate 28. In a sense, the chamber is fitted to the man¬ drel as a glove is fitted to a hand. In this inver- ted position the mandrel is extended under a biasing action, but its movement is limited by the drive shaft. After the chamber is fitted to the mandrel, the bowl cover 30 is refitted and secured with the retainer band and the top section is returned to its closed position. The Internal Assembly Figure 3 shows the fully assembled inner assembly with the variable-volume chamber in place. More specifically, the internal drive 23 is supported by the outer housing top section 16. The drive shaft 24 is aligned with the spin axis A-A and ex¬ tends downwardly from the drive 23 through the sup¬ port plate 28. _ O PI The drive shaft 24 includes a support plate connecting pin 24a for establishing a driving, connec¬ tion with the support plate 28. The support plate 28 includes a transverse top wall 28a which has a downwardly-extending boss- like stub 28b. The stub includes an aperture 28c through which the drive shaft 24 extends and defines a spring seat 28d. A drive pin connecting groove 28e_ is provided on the drive side of the stub 28b for driving connection with the pin 24a. The support plate also includes a peripheral side wall 28f_ that terminates in an outwardly-extending flange 28g. The flange 28g may include one-half.of a. high-G port opening 28h. The bowl cover 30, which is secured to the. support plate 28, includes a transverse bottom wall portion 30a_, and an upwardly-extending and outwardly- tapering side wall portion 30b which terminates in flange 30c_ that cooperates with the support plate flange 28g for securing the bowl 30 to the plate 28. A conduit-receiving aperture 30d extends through the bottom wall, is aligned with the spin axis A-A and the low-G port 42 passes therethrough. The flange also includes a high-G port opening 30e_ which can be aligned with port opening 28h to form a high-G outlet. The cover 30 has a slot 30f_ which extends through the side wall from the flange to the port. The mandrel 32 is positioned inside the cover 30, is shaped to generally conform to the interior of the rotor and has a bottom wall 32a, tapering side wall 32b and skirt 32c_. The bottom wall is provided with a retainer recess 32d. A spring-biasing mechanism is provided for urging the mandrel 32 toward the bowl 30 and against the chamber 40. The biasing mechanism includes a coiled compression spring 46 that surrounds the drive shaft 24, and is held in position at the top end by the stub 28b and spring seat 28d and at the bottom end by post-like keeper 48. The post 48 is an elongated, hollow, cylindri- cally-shaped member which seats in the mandrel recess 32cL The post includes a body portion 48a which fits within the spring 46 and an outwardly-extending flange or spring seat 48b on which the lower end of the spring rests. At the upper end, the post 48 has a top wall 48£ with an aperture 48d through which the drive shaft 24 extends. The drive shaft has at its lower end a retain¬ er groove 24b which is positioned within the post 48 and a C-shaped retainer spring 24c which fits within the groove to retain the post 48 on the drive shaft and limits the extension of the spring 46. Thus the biasing spring cooperates with the support plate stub 28b, post 48, drive shaft 24, pin 24a_, and retainer 24c to urge the mandrel against the processing chamber 40 and toward the bowl 30. The maximum extension of the spring is controlled by the length of the drive shaft, between the pin 24a and retainer 24c_, positioning of the retainer 24c, as shown in Figure 2 , and by the position at which the mandrel engages the bowl 30 as shown in Figure 3. The limit for compression of the spring 46 is defined by its solid height; abutment of the post 48 and the stub 28b; and/or engagement of the mandrel skirt 32d and support plate. After assembly and installation of the cham¬ ber and closure of the housing, the biasing spring 46 urges the post 48 and, thus the mandrel, downward¬ ly toward the bowl cover. The downward travel of the mandrel is limited by the restraint of the bowl and the engagement of the shaft retainer 24£ and post 48. In the fully extended position, the mandrel ex¬ presses substantially all fluid from the chamber, and, as shown, the chamber is prepared for receiving whole blood and component separation. In operation the centrifuge is started with drives 22 and 23, and whole blood drawn from the donor is delivered to the chamber via the umbilicus 34. The whole blood entering the chamber causes the cham- ber to expand and push against the mandrel 32. As the chamber fills, it conforms to the shape of the mandrel and cover and urges the mandrel toward a re¬ tracted position. As the mandrel retracts, the post 48 is pushed upwardly, which causes the spring 46 to compress until the chamber is fully expanded or until the spring reaches its fully compressed solid height where the post abuts the support plate stub. During separation, therapeutic components may be selectively withdrawn from the chamber through the low-G port 42 (or other ports if provided) , thus decreasing the chamber volume. As the chamber volume decreases, the mandrel advances toward the cover, thus maintaining a conforming force against the cham¬ ber. As the mandrel advances , and retracts in re- sponse to volume changes, the rim edge 40a_ of the chamber rolls up and down. The chamber is sufficiently flexible so as to permit- adjustment in volume without fracturing or tear¬ ing. It will be noted that the chamber walls may fold back against themselves during this process. At the end of the procedure, the chamber is removed by open¬ ing the housing and interior casing and then sliding the chamber off the mandrel. From the foregoing it will be seen that the apparatus disclosed herein provides an apparatus for O PI centrifugal apheresis in which the volume of the pro¬ cessing chamber is variable. The RBC and Plasma Volumes The shape of the bowl 30 and mandrel 32 coop- erates with the chamber 40 to define a red blood cell collection volume and a plasma collection volume. Referring to Figure 4, the plasma collection volume 50 is a cylindrical,, disc-like space between the bowl bottom wall 30a_ and the mandrel bottom wall 32a_. The blood cell collection volume is the annularly-shaped space 52 defined by the bowl side wall 30b and- -the - mandrel side wall 32b_. The blood cell collection volume 52 and plasma collection volume 50 are approximately equal as shown in the filled condition in Figure 4. Furthermore, the volumes remain approximately equal to each other as the total volume of the chamber varies. In other words, throughout the range of chamber volumes from empty to full, the ratio of red blood cell or packed cell collection volume to plasma collection volume remains substantially constant at about 1:1. Referring now to the packed cell collection volume 52, it is seen that during operation the red blood cells sediment toward or are driven toward the bowl wall 30b. This wall has a large surface area so as to maximize separation of the red blood cells. The interface between the packed or red blood cell volume and plasma volume is a cylindrically- shaped surface, shown with dotted lines, which ex- tends between the outer edge of the mandrel bottom wall 32a_ and the outer edge of the cover bottom wall 30a. During separation, a layer known as the "buffy layer" forms at that interface due to the separation of the platelets from the plasma. As shown, the in¬ terface surface area is smaller than the RBC sedimenta¬ tion surface. The reason the interface surface area is smaller is to minimize platelet separation during RBC collection. In the embodiment shown herein, the RBC sedimentation surface area is greater than the plate- . let interface surface area. Desirably, the ratio of RBC surface area to interface surface area is at least 2:1 and even as great as 4:1. These relation¬ ships are selected so as to maximize RBC separation while minimizing platelet from plasma separation and loss into the buffy layer during RBC separation. During RBC separation"fluids άn the ^ red *** blood ** cell— • -- volume 52 are exposed to high-G forces, while fluids in the plasma volume 50 are exposed to low-G forces. In operation, the chamber is filled with whole blood and then subjected to a first or hard spin to obtain RBC separation. During this spin, red blood cells sediment and move radially outward¬ ly and into the volume 52 where the cells then sedi¬ ment toward the outer wall. During this operation plasma and platelets are displaced inwardly toward the plasma volume 50. Platelet-rich plasma collects in the volume 50 and is subjected to much lower G or separation forces since its radial distance from the spin axis is less than that for the RBC's. Hence platelet * separation from the plasma is minimized. In one example, the chamber is filled with about 500 milliliters of whole blood having a hema- tocrit of 40 (i.e., 40 volume percent red blood cells) . After spinning and separation, about 250 milliliters of packed red blood cells, with a hema- tocrit of 80, is obtained in the volume 52 and OMPI about 250 milliliters of platelet-rich plasma is available in the plasma volume 50. Collection of the RBC or platelet-"rich plas¬ ma can be effected through the high or low-G ports as desired. Thereafter, in subsequent separations platelets can be separated from the plasma so as to permit separate collection of platelets and platelet- free plasma.- It will be appreciated that numerous changes and modifications can be made to the embodiment shown herein without departing from the spirit and scope of this invention. OMPI

Claims: WHAT IS CLAIMED IS: Claim 1. A liquid processing apparatus for use in centrifugal apheresis in which whole blood is received from a donor, separated into therapeutic components and selectively collected; said apparatus including a processing chamber support system for supporting and cooperating in con¬ trolling the volume of a variable-volume blood pro¬ cessing chamber during apheresis, said support system being constructed to spin about a spin axis; said system including: chamber cover means for receiving--a- ar-i- able-volume chamber; mandrel means for engaging a variable-volume chamber and applying a conforming force to a chamber by urging a chamber toward the cover means and caus¬ ing a chamber to conform to the shape of the cover means; whereby said chamber is positioned between the cover means and mandrel means during centrifugal apheresis and said cover means and mandrel means cooperate in controlling the volume of a chamber. Claim 2. An apparatus as in Claim 1, wherein said support system is substantially symmetric about said spin axis. Claim 3. An apparatus as in Claim 2, wherein said cover means defines a rigid, bowl-like shape for receiving a processing chamber within said cover means. Claim 4. An apparatus as in Claim 3, wherein said mandrel means is positioned to engage and urge a processing chamber into said bowl-like cover means and against the inner surfaces thereof. Claim 5. An apparatus as in Claim 4, wherein said mandrel is shaped to conform with said bowl-like cover means and nest therein. Claim 6. An apparatus as in Claim 5, wherein the outer surface of said mandrel means has a cup- like shape. Claim 7. An apparatus as in Claim 6, wherein said mandrel means and cover means cooperate to cause a processing chamber to conform to a bowl-like shape. Claim 8. An apparatus as in Claim 2, wherein said mandrel means is axially movable along the spin axis toward and away from said cover means. Claim 9. An apparatus as in Claim 8, where¬ in said mandrel means is biased for movement along the spin axis toward said cover means and into engagement with said flexible chamber. Claim 10. An apparatus as in Claim 9, where¬ in said mandrel means is axially movable against said bias and away from said cover means in response to expansion of said flexible chamber means. Claim 11. An apparatus as in Claim 10, where¬ in there is further provided drive means which is operatively associated with said cover means, mandrel OMPI means and a chamber for spinning said cover means, mandrel means and a chamber at a controllable and predetermined rate. Claim 12. An apparatus as in Claim 11, wherein said chamber support drive means is carried on a rotatable support and said chamber support ro¬ tates at twice the rate of the rotatable support and . in the same direction. Claim 13. An apparatus as in Claim 12, wherein said fluid-carrying conduit means is construc¬ ted for connection to a stationary external site using stationary fluid seals. Claim 14. An apparatus as in Claim 2, where¬ in said mandrel is adapted to nest within said cham- ber cover so as to completely compress said flexible chamber and express substantially all fluid there¬ from. Claim 15. An apparatus as in Claim 2, where¬ in said chamber cover includes port means for connec- tion with said exterior. Claim 16. A liquid processing apparatus for use in centrifugal apheresis in which whole blood is received from a donor, separated into therapeutic components and selectively collected; said apparatus comprising: an external housing having top and bottom portions which is constructed to spin about a spin axis; an internal processing chamber support system for supporting and cooperating in controlling the volume of a variable-volume blood processing cham¬ ber; said support system being rotatably secured to said external housing and constructed to sp n about said spin axis; said support system including: drive means supported by said external housing; support plate means drivingly connected to said drive means for spinning about said axis; chamber cover means for receiving a var¬ iable-volume chamber being releasably secured to said support plate means; said support-plate-means and-said-cham¬ ber cover means defining an internal chamber-receiving space; mandrel means positioned within the in¬ ternal space defined by the support plate and chamber cover, said mandrel means being mounted therein for movement along said spin axis and toward said cover means; so as to engage a variable- olume cham¬ ber in said cover and apply a conforming force thereto so as to cause said chamber to conform to the shape of said cover means and mandrel means. Claim 17. An apparatus as in Claim 16, where¬ in .said external housing and said chamber support system are substantially symmetric about said spin axis. Claim 18. An apparatus as in Claim 17, where- in: said cover means is substantially bowl-shaped; said mandrel means is σonformingly cup-shaped; and ' OMPI said mandrel means and cover means cooperate to cause a variable-volume chamber to form a bowl-like shape. Claim 19. An apparatus as in Claim 17, where- in said biasing means comprise compression spring means aligned with the spin axis and seated at one end against said support plate means and at the other end against an inner surface of sai mandrel means for urging said mandrel means away from said support plate means and toward said cover means. Claim 20. * An * apparatus-as-άn * ~C aim- 9', * - here¬ in said support plate means includes stub means which acts as a keeper for one end of the spring and there is further provided post means for engaging the inter- nal surface of said mandrel means and acting as a keeper for the other end of said spring. Claim 21. An apparatus as in Claim 20, where¬ in said drive means includes a drive shaft which ex¬ tends through said support plate stub and said post means, and retainer means on the post end of said drive shaft for retaining the post means on the drive shaft. Claim 22. An apparatus as in Claim 21, where¬ in said stub means includes a drive pin-receiving groove transverse to said spin axis, and said drive shaft is provided with a transverse drive pin which is adapted to engage said groove for drivingly con¬ necting said groove and said pin. Claim 23. An apparatus as in Claim 22, where- in.said post is cylindrically shaped, has a hollow OMPI interior and apertured transverse top wall, whereby said drive shaft extends through said " aperture and said retainer is within said hollow interior. Claim 24. An apparatus as in Claim 23, where- in the extension of the biasing spring is limited by the length of the drive shaft between the drive pin and retainer. Claim 25. An apparatus as in Claim 20, where¬ in said mandrel means includes a post-receiving re- cess for positioning said post means on said spin axis. Claim 26. An apparatus as in Claim 17, where¬ in drive means drive the external housing in a direc¬ tion at a first rate of rotation and drive the inter- nal support in the same direction at twice the first rate. Claim 27. An apparatus as in Claim 26, where¬ in said chamber cover is provided with at least one fluid flow aperture which is positioned in the bottom wall at the spin axis, and there is provided conduit means -extending from said chamber aperture, through • said external housing and to a stationary external connection. Claim 28. A centrifugal processing apparatus which includes: an enclosed blood processing chamber; a bowl-shaped cover member for receiving and shap¬ ing said chamber, said bowl-shaped member having a transverse bottom wall and upwardly-extending side wall; a cup-shaped mandrel having a transverse bottom wall and upwardly-extending side wall, said mandrel shaped to conform with said cover member, nest there¬ in and cooperate in shaping said processing chamber; wherein said cover member side walls, mandrel side walls and chamber define an annularly-shaped blood volume between said side walls, and the cover member wall defining a blood sedimentation surface, said cover member and mandrel bottom walls defining a cylindrical plasma volume therebetween, said volume defining a blood/plasma interface; and wherein the area of the blood sedimentation sur- face is gr * eater"thanrthe *~ su-_ira- * ce ^^ plasma interface. Claim 29. An apparatus as in Claim 28, wherein said chamber is flexible and of variable volume. Claim 30. An apparatus as in Claim 28, wherein the blood volume and plasma volume are sub- stantially the same throughout the range of chamber volumes. Claim 31. An apparatus as in Claim 28, wherein the blood sedimentation surface area is at least about twice that of the interface surface area. Claim 32. An apparatus as in Claim 31, wherein the blood sedimentation surface area is about four times greater than the blood/plasma interface area.

Inventors: BROWN RICHARD I, BROWN, RICHARD, I.
Applicants: BAXTER TRAVENOL LAB, BAXTER TRAVENOL LABORATORIES, INC.
Application year: 1984
Main classification: B04B1
IPC codes: B04B5, B04B7