Separation set having plate-like separation container with annular pinch valve for blood component preparation

A separation set for blood component preparation and similar separations for use in a centrifuge rotor, the set including a plate-like separation container made of a flexible material, an annular pinch valve which is mounted on and divides the separation container into a central section and an annular outer section, a first component container which is connected to the center of the separation container, a second component container which is connected to the circumference of the separation container, and a blood withdrawal tube for supplying blood to the outer section. The blood is separated in the outer section into plasma, buffy coat and red blood cells. Then the plasma is displaced to the first component container and the buffy coat to the central section where it is enclosed through the action of the pinch valve. The separation set with the pinch valve is then removed from the centrifuge and the red blood cells are transferred to the second component container.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The invention relates to a separation set for blood component preparation
 and similar separations in a centrifuge rotor of a type comprising an
 annular separation compartment and a central compartment, which are
 arranged concentrically with the axis of rotation of the rotor and
 communicate with each other via an annular slot, and comprising means for
 reducing in operation the volume of the separation compartment. The
 separation set comprises a plate-like separation container of a flexible
 material and a first component container which by means of a tube is
 connected to the center of the separation container.
 2. Description of the Related Art
 In blood component preparation, blood is separated into the components
 plasma, buffy coat and red blood cells by centrifugation. A sterile set of
 interconnected flexible containers is used. The presently most common mode
 of operation is to use a sterile set of interconnected rectangular blood
 bags, one bag constituting the separation container, to which the blood is
 supplied, and the others being component containers, to which the
 separated components are then transferred. The entire set is centrifuged
 standing in swing-out centrifuge cups and, after centrifugation, the blood
 components form layers in the separation container according to the
 increasing specific weight, viz. a plasma layer, a buffy coat layer and a
 layer of red blood cells. Then the set of bags is removed from the
 centrifuge and moved to a pressing device for pressing out the plasma
 layer and then the buffy coat layer to associated component containers.
 The manual handling of the bags when the layers are in contact with each
 other results in a certain remixing, and it is inevitable that a certain
 amount of buffy coat remains in the separation container together with the
 red blood cells after the pressing-out operation.
 Modem blood component therapy, however, requires very pure fractions of
 plasma and red blood cells, i.e. they should as little as possible be
 contaminated by the intermediate buffy coat fraction. The pressing-out of
 the various fractions from the separation container constitutes a critical
 operation with respect to the achieving of pure components.
 An improvement in this respect is disclosed in WO 96/29081, where a more
 complete pressing-out of the buffy coat fraction is achieved by applying a
 pulsating pressure to the top of the container.
 A different technique of achieving high purity of the separated fractions
 is to use a centrifuge rotor of the type mentioned by way of introduction,
 in which an annular separation container is compressed in the separation
 compartment of the rotor during rotation, and the separated layers are
 pressed to the central compartment of the rotor while they are affected by
 the prevailing G field. According to WO 87/06857, a centrifuge rotor of
 this type is known, and in one embodiment there is described an annular
 pinch means which acts in the slot-like zone between the annular
 separation compartment and the central compartment arranged inwardly
 thereof. A flexible plate-like separation container extending over the
 separation compartment and central compartment is divided by said pinch
 means into an outer annular container and an inner central container. A
 charge of blood is transferred to the annular part and separated by
 centrifugation. At a certain predetermined rotational speed, the pinch
 means opens the slot-like connection and at the same time the volume of
 the annular separation compartment decreases, whereby plasma is displaced
 via the central part and further on to a centrally connected plasma
 container, and buffy coat is displaced into the central part. Then the
 pinch means closes the connection. Plasma is now available in the
 connected plasma container, buffy coat in the central part of the
 separation container and red blood cells in the outer part of the
 separation container. The buffy coat and the red cells must, however,
 somehow be taken care of before the separation container can be removed
 from the centrifuge since the action of the pinch means ceases when the
 cover of the rotor is opened. This problem has not been satisfactorily
 solved, and therefore this centrifuge variant with the annular pinch means
 has not been used in practice, although it offers a very advantageous way
 of displacing a component layer to another container.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide a set of containers which
 solves the above-mentioned problems and permits effective preparation of
 blood components of high purity by using a plate-like separation container
 in a centrifuge of the type mentioned by way of introduction. The set of
 containers according to the invention thus comprises a plate-like
 separation container of a flexible material and a first component
 container which by means of a tube is connected to the center of the
 separation container. The separation set is characterized by an annular
 pinch valve which is mounted on the separation container and arranged to
 divide this into a central section and an annular outer section, and a
 second component container which by means of a tube is connected to said
 outer section.
 The annular pinch means thus follows the container set during its handling
 in and outside the centrifuge. The transfer of the red blood cells to the
 second component container is carried out outside the centrifuge after the
 separation has been completed and the centrifuge can be utilized
 effectively. In this type of centrifuge, only one charge of blood can be
 processed in each centrifugation, which means that a short process time in
 the centrifuge is very important in routine preparation of blood
 components. The pinch valve can be reused and applied to a new separation
 container after transfer of the red blood cells to a component container.
 The invention is further characterized in that the components plasma and
 red blood cells will be extremely pure by the buffy coat layer being
 affected to a very small extent and being mixed to a minimum extent with
 the neighboring layers during the displacement to the central section of
 the separation container. The buffy coat layer is displaced radially
 inwards to the center of the rotor uniformly from all directions and needs
 not be pressed through a limited outlet opening. Besides the displacement
 takes place during rotation while the layers are acted upon by the
 centrifugal force.
 Two different embodiments of the invention will now be described in more
 detail with reference to the accompanying Figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Further scope of applicability of the present invention will become
 apparent from the detailed description given hereinafter. However, it
 should be understood that the detailed description and specific examples,
 while indicating preferred embodiments of the invention, are given by way
 of illustration only, since various changes and modifications within the
 spirit and scope of the invention will become apparent to those skilled in
 the art from this detailed description.
 In the first place the separation set is intended for separation of whole
 blood into the fractions plasma, buffy coat and red blood cells, but it is
 also suited for separation of other cell suspensions into three fractions
 when it is essential for the process to be carried out in a closed sterile
 system and for the fractions to be isolatable in separate containers
 without opening the system.
 The separation container according to FIGS. 1-2 and 4-5 consists of a
 plate-like separation container 1 of a flexible plastic material, for
 instance, of the same type as used in conventional blood bags. The
 separation container can be made, for instance, of two plastic sheetings
 arranged above each other, which are joined by an annular weld. A first
 component container 2 is by means of a tube 3 connected to the center of
 the separation container. A second component container 4 is by means of a
 tube 5 connected to the separation container in its outer section,
 preferably at its circumference as shown in the Figure. The component
 containers can be rectangular bags of a flexible plastic sheeting of
 conventional type, the plastic sheeting material being selected with
 regard to the type of cells that are to be stored in the container. In the
 separation of whole blood, the second component container 4 is initially
 filled with a certain amount of storage liquid 8 for red blood cells, e.g.
 SAG solution or SAGMAN solution. Use is normally made of about 63 ml of
 such a solution for the red blood cells from a blood donation. The
 component container 4 is in this case temporarily sealed by, for instance,
 a so-called breaking pin 7. In the embodiment illustrated, the separation
 container is also provided with a blood withdrawal tube 8 with a
 withdrawal cannula 9, blood being donated directly from a blood donor to
 the separation container. The different containers may also be provided
 with filling and withdrawal ports 10, 11, 12 and 13 of the type that is
 frequently used on blood bags. The separation container is provided with a
 suspension device 14 which is arranged in the circumference diametrically
 opposite to the connection of the tube 5. The component container 4 is
 provided with a suspension device 15 at its lower edge, i.e. just opposite
 the edge in which the tube 5 is connected. The separation set further
 comprises a detachable annular pinch valve 16 (FIGS. 2 and 5) which is
 mounted on the central part of the separation container and is adapted to
 shut off a central section 17 from a surrounding annular outer section 18.
 The pinch valve comprises two coacting parts 21, 22; 44, 45 which are
 mounted from either side of the separation container.
 In the embodiment shown in FIG. 1, the separation container 1 is formed
 with a number of holes 19 through the container in the central section.
 The opposite walls (plastic sheetings) of the container are in some
 portions welded together, and the holes 19 are formed through these
 portions. The tube 3 between the separation container 1 and the first
 component container 2 is provided with a remote-controlled pinch valve 20
 which is applied directly to the tube. The annular pinch valve (FIG. 2)
 consists of two disks 21 and 22 which are provided with coupling elements
 24, by means of which the disks can be interconnected adjacent to each
 other so as to define a certain space 25 between themselves. Preferably,
 the disks are slightly cupped and the coupling elements are arranged on
 the concave side of each disk. The disks are attached to each other from
 either side of the separation container 1 with the coupling elements 24
 extending through the holes 19. The space 25 between the disks can be
 adapted to accommodate the volume of buffy coat obtained from a separated
 blood donation. The upper disk 21 has a groove-shaped opening 23 (FIG. 1)
 which extends from the circumference to the center and into which the tube
 3 is inserted in connection with the mounting. The disks have a slightly
 angled edge portion 26 along the circumference, which results in an
 essentially V-shaped groove 27 forming between the disks. A pretensioned
 elastic ring 28 is arranged in this groove. The ring 28 presses the
 separation container 1 against the disk 22 such that an annular pinch
 valve function is achieved. In centrifugation above a certain rotational
 speed, the elastic ring 28 expands outwards such that the valve opens. The
 ring 28 can be made of e.g. a rubber material.
 FIG. 3 illustrates the separation set arranged in a centrifuge rotor 29.
 The rotor is of a type whose separation space comprises an annular
 separation compartment 30 and a central compartment 31, which are arranged
 concentrically with the rotary shaft 32 of the rotor and communicate with
 each other through a slot-like zone 33. Moreover the rotor comprises means
 for reducing the volume of the separation compartment during rotation in
 order to displace a separated fraction from the separation compartment
 into the central compartment In the embodiment illustrated, the volume of
 the separation compartment is reduced by pumping hydraulic fluid through a
 duct in the rotor shaft to an annular hydraulic chamber 37 which is
 delimited from the separation compartment by means of a flexible diaphragm
 38. The separation space is covered with a removable rotor cover 34.
 Centrally in the rotor cover there is a space 35 where the component
 container 2 (plasma container) is placed. When the rotor cover is mounted,
 the space can be reached via a lid 36 in the cover. In the embodiment
 shown, there is also an elongate narrow space 40 in the rotor shaft below
 the central compartment The second component container 4 can be placed in
 this space during centrifugation. In the rotor cover there is also a
 groove 41 which receives the elastic ring 28 when it expands from its
 valve-closing position. The rotor cover is suitably made of a transparent
 material to make it possible to monitor the movement of the separated
 layers by means of photocells 39 which are mounted in the surrounding
 casing 43. The remote-controlled tube valve 20 is controlled by the
 control unit 42 which is correspondingly mounted in the casing. The
 control unit 42 may consist of an electromagnet that switches the tube
 valve 20 to its closed position.
 The function of the separation set will be described below, the use for
 separating a blood donation which is donated directly to the separation
 container 1 being taken as an example. Before the donation, the annular
 pinch valve 16 has been mounted on the separation container 1, such that
 it is divided into a central section 17 and an annular outer section 18.
 Blood is withdrawn from a blood donor through a blood withdrawal tube 8 to
 the outer section 18. Normally 450 ml of blood are donated. An
 anticoagulant, for instance CPD solution, is simultaneously supplied or
 has been supplied in advance to the outer section 18. During donation, the
 separation set is placed in a blood cradle.
 After completion of the donation, the separation set and the connected
 pinch valve 16 are placed in the centrifuge rotor, such that the central
 section 17 defined by the pinch valve 16 is positioned in the central
 compartment 31 and the annular outer section 18 is positioned in the
 separation compartment 30. The component container 4 is placed in the
 space 40 in the rotor shaft and the tube 5 is placed in a groove in the
 rotor. The rotor cover 34 is mounted and the plasma container 2, which is
 accessible through the lid 36, is fixed to the walls of the cover space
 35. The rotor is started and the speed is increased to a predetermined
 speed of operation. A free filling of the hydraulic chamber 37 can be
 applied during centrifugation. This means that the space in the separation
 compartment 30 which is not occupied by the blood quantity is
 automatically filled by hydraulic fluid being sucked from the hydraulic
 container (not shown) to the hydraulic chamber 37 by the fact that these
 communicate with each other as communicating vessels via a by-pass of the
 hydraulic pump. The blood-filled outer section 18 consequently obtains a
 somewhat flattened conical shape and its entire radial extent is kept
 filled with liquid, which results in rapid separation and relatively small
 interfaces between the separated layers.
 The tension in the elastic ring 28 is adapted to resist the centrifugal
 force up to a certain rotational speed. At higher speeds the centrifugal
 force surmounts the tension, whereby the ring expands outwards and is
 caught by the groove 41 in the rotor cover 34. In this connection, the
 barrier between the central section 17 of the separation container 1 and
 its outer section 18 opens. The opening and closing of the pinch valve 16
 are thus controlled by means of the rotor speed. After a predetermined
 time the separation is completed. The plasma having the lowest specific
 weight lies in a circular layer closest to the center, then the buffy coat
 and furthest away from the center the red blood cells. The by-pass
 function is now switched off and the hydraulic pump is started. While the
 rotor spins at a speed which holds the pinch valve 16 open, hydraulic
 fluid is pumped in under the diaphragm 38. The volume of the separation
 compartment 30 is reduced and the layers are displaced towards the center.
 Plasma is displaced through the central section 17 and further through the
 tube 3 to the plasma container 2. While the plasma fills the plasma
 container 2, the buffy coat layer moves more and more towards the center
 of the separation container 1. The movement takes place uniformly from all
 sides and against the prevailing G field, which makes the buffy coat layer
 remain intact and mix with the adjoining layers to a minimum extent
 The movement can be monitored by means of the photocell 39 through the
 transparent rotor cover, such that the pumping of hydraulic fluid can be
 stopped when the buffy coat layer is positioned inside the area of the
 annular pinch valve 16. The control unit 42 now doses the tube valve 20
 and the speed of the rotor is reduced such that the tension in the elastic
 ring 28 surmounts the centrifugal force and returns to the initial
 position in the V-shaped groove 27. The buffy coat is thus enclosed in the
 central section 17 of the separation container 1. The centrifuge is braked
 to come to a stop, the rotor is opened and the separation set is removed.
 The plasma container 2 is separated from the separation set by means of a
 tube welding gun and the rest of the separation set is suspended from the
 suspension device 15. The breaking pin 7 is broken such that the storage
 liquid 6 flows through the tube 5 to the separation container and mixes
 with the red blood cell concentrate. The separation set is then turned and
 suspended from the suspension device 14, such that the now diluted and
 somewhat less viscous concentrate of red blood cells flows down into the
 component container 4. The component container 4 is then separated by the
 tube 5 being welded together by means of a tube welding gun. The plasma
 and the red blood cells have thus been isolated in separate component
 containers. The pinch valve 16 can now be removed and used for a new set
 of bags. In the separation container 1 remains the buffy coat fraction
 which can be further processed for recovery of valuable products. For
 instance, buffy coat fractions from several separations can be combined
 and centrifuged for recovery of a thrombocyte cell suspension as disclosed
 in WO 95/01842.
 FIGS. 4 and 5 show an alternative embodiment of the set of bags and the
 pinch valve. FIG. 4 shows the separation container 1 and the associated
 component containers 2 and 4 and the blood withdrawal tube 8. The pinch
 valve 16 has only been indicated by a dashed line. Equivalent components
 in the different Figures have been given the same reference numerals.
 The separation set differs from that described in connection with FIGS. 1
 and 2 mainly by the pinch valve 16 consisting of an annular magnet 44 (an
 annular permanent magnet) and an annular anchor 45 of a magnetically
 actuatable material, preferably iron sheet. The annular magnet 44 is
 applied against the upper side of the separation container 1 and the
 anchor 45 against the opposite side of the container. The annular magnet
 attracts the anchor and compresses the intermediate container, thereby
 achieving a valve function. The separation container 1 is thus divided
 into a central section 17 and a surrounding annular section 18. Holes 19
 in the central section 18 are thus not necessary in this embodiment The
 first component container 2 is provided with a pretensioned non-return
 valve 46, i.e. the valve requires a certain liquid pressure to open for
 the liquid to flow into the container and completely blocks the liquid
 from flowing out The magnetic pinch valve is opened by applying a pump
 pressure, which is also used to open the valve 46.
 FIG. 6 illustrates the separation set arranged in a centrifuge rotor 29.
 The rotor is of a somewhat different type from the one shown in FIG. 3 and
 does not have, for instance, the elongate narrow space 40 along the rotor
 shaft. The centrally arranged space 35 in the rotor cover is in this case
 adapted to hold the two component containers 2 and 4. Equivalent
 components in the two centrifuges have been given the same reference
 numerals and are not described in more detail here. Both types of
 centrifuge can easily be adapted to be used for the two separation sets as
 described.
 Between the central compartment 31 and the space 35 in the cover there is a
 separate insert 47 which defines these two spaces from each other. The
 insert 47 has a groove-like opening 48 which extends from its
 circumference to the center, thereby making it possible to push in the
 insert between the separation container 1 and the first component
 container 2, the tube 3 being placed in said groove Furthermore said
 insert 47 is formed with an annular groove 49 which acts as a guide for
 the annular magnet 44.
 The separation set is placed in the separation compartment of the rotor,
 such that the central section defined by the pinch valve 16 is positioned
 in the central compartment 31 and the annular section is positioned in the
 separation compartment 30. The component containers 2 and 4 are placed in
 the space 35 in the cover. The rotor is formed with a groove, in which the
 tube to the second component container is placed.
 The separation set functions fundamentally in the same manner as described
 in connection with FIGS. 1-3. Before donation of blood to the set, the
 separation container 1 is placed in a fixture (not shown), where the
 annular magnet 44 and the anchor 45 are mounted in the correct place on
 the container. The pinch valve now shuts off a central section 17 from an
 annular outer section 18. Blood is withdrawn from a blood donor through
 the blood withdrawal tube 8 to the outer section 18 in the same manner as
 described above.
 After completion of the donation, the separation set and the associated
 pinch valve are placed in the centrifuge rotor. The insert 47 is mounted
 and the tubes are arranged in grooves intended therefor. The rotor cover
 34 is mounted, and the component containers which are accessible through
 the lid 36 are attached to the walls of the cover space 35. The rotor is
 then run up to the speed of operation with the by-pass function of the
 hydraulic pump activated, such that a free filling of the hydraulic
 chamber occurs in the same manner as described above. The pinch valve 16
 is closed while the separation proceeds and the opening and closing
 thereof are in this case independent of the speed of the rotor.
 When the separation is completed, the rotational speed can be reduced to
 reduce the tension in the cover during the pressing-out of plasma. The
 by-pass function is shut off and the hydraulic pump is started. A pump
 pressure forms in the rotor. This pressure increases until the annular
 magnet 44 comes loose and is pressed upwards to an upper position in the
 groove 49. The magnetic force decreases rapidly as the gap to the anchor
 increases, and the groove is made so deep that the magnetic force
 decreases significantly. The plasma now expands the sheetings in the
 central compartment 31 and is passed on through the tube 3 to the plasma
 container 2, where the pretensioned non-return valve opens completely.
 While plasma fills the plasma container, the buffy coat layer moves more
 and more towards the center of the separation container as described
 above. The displacement of the buffy coat layer can be monitored by means
 of a photocell through the transparent rotor cover, such that the pumping
 of hydraulic fluid can be interrupted when the buffy coat layer is
 positioned inside the area of the annular pinch valve. The pumping
 operation is then interrupted and the by-pass connection is activated,
 whereby the pressure in the separation container immediately drops. The
 non-return valve 46 and the annular pinch valve 16 now dose. The
 centrifuge is stopped, the rotor cover is opened and the separation set is
 removed and then handled in the same manner as described above.
 The invention being thus described, it will be apparent that the same may
 be varied in many ways. Such variations are not to be regarded as a
 departure from the spirit and scope of the invention, and all such
 modifications as would be recognized by one skilled in the art are
 intended to be included within the scope of the following claims.