BLOOD SEPARATION METHOD AND APPARATUS

Abstract: The invention relates to a method for separating blood into blood components and to apparatus for removing blood components from a blood container which has at least one outlet opening. The method comprises introducing blood into a blood container which has at least one outlet opening in the upper limit of the container, centrifuging the blood container in a relatively high centrifugal field to form three mutually superimposed component layers, applying pressure to the blood container to remove the upper component through the outlet opening and, during or after this pressure stage, forming in the blood container a channel through which a second component is connected with the outlet opening or with a second outlet opening, and then applying further pressure to remove the second component through the channel formed. The apparatus for removing centrifuged and stratified blood components from a blood container (1a) having at least one outlet opening includes a housing (16) which has mounted therein a first and a second pressure plate (3, 2) which are movable in relation to one another, a suspension means (50) by means of which the blood container (1a) can be positioned between the pressure plates (3, 2), and means for achieving relative movement of the pressure plates. The apparatus also includes a mandrel (5) in the second pressure plate (2) which is operative in forming a channel in the container (1a) as the blood container (1a) is compressed to remove the uppermost blood component, this channel connecting a blood container outlet opening with the bottom blood component and being formed only when the upper component has been removed from the blood container.

Description: BLOOD SEPARATION METHOD AND APPARATUS Technical Field The present invention relates to a method of separating blood into blood components and of transferring stratified components obtained by centrifugation to component containers and also to an arrangement of apparatus for trans¬ ferring the stratified components obtained by centrifugation to respective connected component containers. Background Art Whole blood is collected in flexible blood containers to which one or more component containers are connected. In order to utilize the whole blood effec¬ tively, the blood collected is typically divided into three fractions, i.e. a plasma fraction, buffycoat fraction and cell concentrate fraction, of which two fractions are normally then transferred to their respective component containers. This division or stratification of the blood into said components is effected by centrifugation. When whole blood is centrifuged, the plasma fraction, which is the specifically lightest fraction, is uppermost, whereas the erythrocyte fraction, which is the specifically heaviest fraction, is undermost and the buffycoat fraction is located therebetween. Volumet cally speaking, the plasma fraction is the largest and therewith the most fluid of the components concerned. The most common type of blood container has an outlet opening to which there is connected a pipe which has at least one branch line leading to individual blood-component containers. Normally, two component containers are connected to the blood container. An arrangement for use in pressing stratified blood components from a blood container to respective component containers is known from EP-A- 0,348,682. This known arrangement includes a vertical plate which is provided with means on which a blood container containing stratified blood component layers can be hung. A second plate is mounted in the upper part of the first- mentioned plate, on a level with the upper limitation of the blood container. This second plate is pivotally mounted to the first plate by means of a vertical pivot axle spaced from said first plate. When transferring the blood components to respective component containers, the second plate is brought into abutment with the blood container and exerts pressure thereonto until essentially all plasma fraction has been transferred to its intended container. This component container is then closed and the next fraction, which is the buffycoat fraction, is transferred to the second container. This second container is closed when all buffycoat has been transferred. The erythrocyte fraction remains in the blood container. One problem with this arrangement resides in the difficulty of transferring all of the buffycoat fraction to its intended container, since the buffycoat components have a highly pronounced tendency to adhere to the walls of the blood container and therewith contaminate the erythrocyte fraction that remains therein. Prior publication EP-A-0,446,713 discloses a blood bag system in which the lightest component, blood plasma, is pressed-out first and then the heaviest component, the red blood corpuscles, with the aid of a press means. This publication does not disclose the structural elements of the press means mentioned therein. The blood bag system disclosed in this reference has two outlet openings in the upper limit of the container. The first outlet opening is connected to the plasma component container by means of a first conduit, and the second outlet opening is connected to the erythrocyte fraction container by means of a second conduit. The second conduit has a length which enables it to extend to the bottom of the blood container. When the plasma fraction has been forced from the blood container, the conduit leading to the plasma container is closed and the conduit leading to the erythrocyte fraction is opened. Because the mouth of the conduit is located immediately above the bottom of the container, the erythrocyte fraction will be pressed out of the container before the buffycoat fraction, which remains in the blood container. This avoids contamination of the erythrocyte fraction by the blood platelets of the buffycoat, these platelets having a pronounced tendency to adhere to the wall of the wall of the blood container. The drawback with this system is that the blood container is more expensive to manufacture, since it requires two outlets in the upper limit of the container and the provision of a conduit which extends into the blood container and down to the bottom thereof. Another blood bag system is known from US-A 4,608,178. This system also includes a container with two outlet openings, one at the upper limit of the container and the other at its bottom limit. The drawback with this known system is that it is much more expensive to produce in relation to systems which have openings solely at the upper container limit. One object of the present invention is to provide a method of using a typical blood container having an outlet opening solely in the upper container limit while, at the same time, enabling the erythrocyte fraction to be removed from the container without being contaminated by the buffycoat fraction. Another object of the invention is to enable the use of blood containers having two outlet openings in the upper container limit instead of one outlet opening at both the upper and the lower limit of said container. A further object of the invention is to enable the use of blood containers which have no conduit that extends into the blood container and down to the container bottom. Still a further object of the invention is to provide a simple arrangement with which blood components that have been stratified by centrifugation can be transferred from the blood container to their intended respective component containers connected to the blood container through the intermediary of one or two openings. Summary of the Invention In accordance with the present invention, these objects are achieved with a method for separating blood into blood components, comprising introducing blood into a blood container which has at least one blood component outlet opening in the upper limit of the container; centrifuging the blood container in a relatively high centrifugal field to form an upper plasma fraction, an intermediate buffycoat fraction and an erythrocyte fraction. The method is characterized by applying pressure to the blood container so as to remove the plasma fraction through the outlet opening; forming in the blood container during said pressure applying stage or subsequent to said stage a connecting passage through which a second fraction is in communication with said outlet opening or with a second outlet opening; and then applying an elevated pressure to remove this second fraction through the connection passage thus formed. Further embodiments of the invention will be evident from the Claims depending from the first main Claim. The inventive method is carried out by means of an arrangement for removing blood components from a blood container having at least one outlet opening, in which the blood components exist in a stratified form subsequent to centrifuging blood. The arrangement includes a housing which accommodates two first and second pressure plates which are movable relative to each other, a suspension means provided in the housing for positioning the blood container between the pressure plates, and means provided in the housing and functioning to move the pressure plates relative to one another and to create in the blood container an internal overpressure which can take both a lower and a higher value. The arrangement is characterized in that one of the pressure plates includes a mandrel which, when the blood container is compressed for the removal of the plasma fraction therefrom, forms a passage which connects the blood container outlet opening with the bottom fraction and which is not formed until the plasma fraction has been removed from the blood container. Advantageous embodiments of the inventive arrangement will be evident from the Claims depending from the apparatus Claim. Brief Description of the Drawings The invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 is a schematic, sectional view of an arrangement for transferring stratified blood components to connected component containers; Figure 2 is a schematic front view of a plate on which there is hung an empty, transparent blood container which is connected to two component containers, and also shows a pressure bladder mounted behind said plate; Figure 3 illustrates schematically a second plate which coacts with the first plate to press blood fractions from the blood container into two component containers shown in Figure 2; and Figure 4 is a schematic cross-sectional view of the plate in Figure 3, taken from the line A-A. Detailed Description of the Invention The apparatus illustrated in Figure 1 includes a housing 16 which is defined by a rear wall 13, a front wall 2, a floor 18 and side walls not shown. Mounted on the front side of the rear wall 13 is a drive means in the form of bellows 15. Mounted on the front side of the bellows 15 is a first plate 3. In the illustrated example, the front wall 2 forms a door which is hinged (not shown) to one of the side walls. Gas is delivered to the bellows through an opening 14 in the rear wall 13, so as to move the front side of the bellows, and therewith also the plate 3, towards the front wall 2. The gas source, control devices, hoses and connections to the opening 14 in the rear wall are not shown. The first plate 3 is provided with suspension means 50 which function to support a blood container 1a on the front side of the plate 3. In the illustrated embodiment (Figure 2), the blood container 1a is connected by means of a hose or like conduit 19 to two component containers which are located outside the housing, which has no roof. Mounted on the rear wall 13 and extending towards the front wall 2 are two guide rods 20. These guide rods 20 pass through openings in the plate 3 on each side of the blood container 1a and the bellows 15. The openings through which the rods 20 extend are configured so as to obviate the risk of sticking or jamming. The front wall 2 coacts with the first plate 3 subsequent to said plate having been driven forwards by the bellows. The front wall 2 will hereafter be referred to as the second plate 2. The plate 2 is described in more detail with reference to Figure 3. Figure 2 illustrates the first plate 3 with suspension means 50 comprising two arms from which there is hung a blood container having two openings 49 which are adapted to the suspension means 50. The blood container 1a has an outlet opening 17 which connects the blood container with two component containers through the medium of a conduit 19. The conduit 19 terminates in a three-way coupling 23 having connected thereto a conduit 21 which leads to a component container 1c, and a conduit 22 which leads to a component container 1b. The blood container 1a also has an inlet opening and an inlet conduit 24 which is provided with a blood-tapping needle on the end thereof distal from the container. Subsequent to filling the container 1 a with a predeter¬ mined quantity of blood, the needle is fused-off and the conduit 24 therewith closed. The first plate 3 only covers about half of the area of the blood contain¬ er, and then its upper half, but widens upwards and beyond the sides of the blood container 1a. The plate 3 is provided on each side of the blood container 1 a with holes through which respective guide rods 20 (Figure 1 ) are passed. A groove 26 of inverted U cross-section is provided in that part of the plate 3 which lies against the blood container. This groove 26 coacts with a mandrel (bar) in the second plate 2. The bellows 15 by means of which the first plate 3 is displaced is shown in broken lines. An area 51 in the plate 3 located inwardly of the groove 26 may be sunken in relation to the remainder of the plate. This sunken area 51 is intended to take-up the buffycoat with the aid of the mandrel 5, when the plates 2 and 3 are pressed together. The second plate 2 of the Figure 3 and Figure 4 illustration has a rectangular shape. The contours of the blood container 1a when coacting with the first plate are indicated in broken lines, wherein reference numeral 6 indicates the joining line and the reference numeral 7 its outer contour. The blood container 1a and the component containers typically consist of two mutually welded foil sheets. In the illustrated embodiment, a rectangular recess 9 having the shape of an inverted U is provided in the upper part of the plate 2. A strip 4 is mounted in the recess 9. Mounted between the strip 4 and the bottom 10 of the recess 9 are springs 8 which allow the strip 4 to move relative to the bottom of the recess and therewith relative to the upper surface of the plate 2. The ends of the springs 8 are attached respectively to the strip 4 and the bottom 10 of the recess. When the blood container is hung on the plate 2, the outer defining limi¬ tation of the strip 4 will follow the inner defining line 6 of the blood container 1a when the blood container is empty or almost empty. The strip 4 has a rectangu¬ lar cross-sectional area, which is constant in the case of the illustrated embodiment. The strip 4 has a passage 11 on a level with the outlet opening 17 of the blood container 1 a, this passage having the form of a recess in that part of the strip remote from the plate 2. Provided inwardly of the strip 4 is a mandrel in the form of a bar 5. The bar 5 is attached to the plate 2 and projects out to a given distance from the plate surface, for instance a distance of 3-5 mm. The bar 5 follows the inner defining line of the strip 4 slightly spaced therefrom or in contact therewith, although not to prevent the strip 4 from moving. When transferring blood components from the blood container 1 a to the component containers 1 b and 1c, the centrifuged blood container 1a is placed in the apparatus 48, the blood components being present in said blood container in mutually superimposed layers. The bottom layer is comprised of the erythrocyte fraction, i.e. the red blood corpuscles, which are the heaviest components of whole blood. The top layer in the blood container 1a is comprised of blood plasma, which is the specifically lightest fraction. The buffycoat fraction lies between these fractions. In Figure 1, the bellows 15 are located in a rearward position, which is the starting position of the bellows at the beginning of a blood component transfer operation. The centrifuged blood container is hung on the suspension means 50 at the beginning of this transfer procedure. The front wall or the second plate 2 is brought to the position shown in Figure 1. Gas, for instance air, is then delivered through the opening 14 in the rear wall 13, so as to inflate the bellows 15 and therewith drive the first plate 3 towards the second plate 2. As will be seen from Figure 2, the lower part of the bellows 15 has roughly the same pres¬ sure area as the container 1a, while the upper part of the bellows has a much larger pressure area. Consequently, the upper part of the blood container is initially compressed more powerfully than its bottom part. The connection to the component container 1c is initially open, while the connection to the second component container 1b is initially closed- As the blood container 1a comes into contact with the second plate, the liquid in the container is displaced and plasma begins to flow to the component container 1 c. As the plate 3 moves towards the plate 2, the blood container 1a will first come into contact with the strip 4 which, upon continued movement of the plate 3 towards the plate 2, will force the plasma fraction from the edge region of the container against which it abuts. Plasma will also flow through a passageway 11a which connects the interior of the blood container 1 a with the outlet opening 17. The passageway 11 a is formed as a result of the pressure in the blood container 1a or through the medium of the passageway 11 in the strip 4. During the plasma transfer stage, the pressure exerted on the blood container 1 a is not sufficiently large to force the strip past the mandrel or bar 5 and into the grove 9. The pressure applied is thus counteracted by the force exerted by the springs 8. When the strip 4 has expelled plasma from said edge or border region, there is thus obtained a barrier with a passageway 11a through which plasma leaves the blood container 1 a. The transference of plasma is terminated, for instance, when a predeter¬ mined quantity of plasma has been transferred or when a device, for instance a photocell, mounted adjacent the outlet opening 17 registers that all plasma has been transferred. The conduit 21 leading to the container 1c and the conduit 22 are closed and opened respectively in a conventional manner and at a time point not described in detail here. Preferably, there is a delay between closing the conduit 21 and opening the conduit 22, so as to increase the pressure in the container 1 a and therewith open the passageway 33 completely before transferring the second fraction. The purpose of this delay is to prevent hemolysis, which would otherwise occur if the erythrocytes were pressed through a passageway which was not fully open. The pressure in the bellows 15 is increased when transfer of the plasma fraction is complete. As a result, the pressure on the strip 4 will be so great as to overcome the force exerted by the springs and the mandrel 5 will press the container walls, which consist of plastic foil sheets, into the groove 26 in the plate 3. This results in the formation of the aforesaid U-shaped channel 33 around the upper periphery of the blood container 1a. As a result of direct contact between the bellows 15 and the bottom part of the blood container 1a, the higher pressure in the bellows 15 provides a correspondingly high pressure in the blood container 1 a, this pressure causing the channel 33 to open fully. The overpressure in the container 1a disappears when essentially the whole of the erythrocytes have been pressed out of the blood container 1 a. The strip 4 will thereby be pressed by the springs 8 against the plate 3, so as to press out the cell content of the channel. Solely buffycoat will then remain in the blood container, enclosed in the space 51. According to one embodiment, the ends of the strip 4 facing towards the blood container 1a are beveled to facilitate formation of said channel. According to another embodiment, the channel 11 in said strip is intended to permit plasma to flow through a first outlet opening when using a blood container 1 a having two outlet openings, one for plasma fraction and one for erythrocyte fraction, in the upper limit of the container. According to the present invention, it is irrelevant which of the plates 2, 3 is movable and which is stationary. Both plates 2, 3 may even be movable towards each other. Similariy, the mandrel 5 and the strip 4 may be arranged on the first plate 3 instead of on the second plate 2. In this case, the groove 26 in the opposing plate and coacting with the mandrel 5 will be provided in the second plate.

Claims: Claims 1. A method of separating blood into blood components, comprising introducing blood into a blood container which has at least one blood compo¬ nent outlet opening at the upper limit of the container, and centrifuging the blood container in a relatively high centrifugal field to form an upper plasma fraction, an intermediate buffycoat fraction and an erythrocyte fraction, characterized by applying pressure to the blood container for removal of plasma fraction through the outlet opening and forming in the blood container during or after this pressure stage a connecting channel through which a second fraction is connected with the outlet opening or with a second outlet opening; and then applying a higher pressure for removal of the second fraction through the formed connecting channel. 2. A method according to Claim 1 , characterized by forming the connecting channel subsequent to having removed a desired quantity of plasma fraction. 3. A method according to Claim 1 or 2, in which the second fraction is the erythrocyte fraction, characterized by forming the connecting channel in a generally U-shape with the base of the connecting channel communicating with the outlet opening through which the erythrocyte fraction shall be removed and the legs of said channel connecting with the erythrocyte fraction. 4. A method according to one or more of Claims 1-3, characterized by applying the pressure for removal of the plasma fraction essentially on the upper part of the blood container. 5. Apparatus for removing blood components from a blood container (1a) which has at least one outlet opening (17) and which contains blood that has been stratified into blood components by centrifugation, said apparatus includ¬ ing a housing (16) which has mounted therein a first and a second pressure plate (3, 2) which are movable relative to one another, a suspension means (50) for positioning the blood container (1a) between the pressure plates (2, 3), and means (15) for causing the pressure plates (2, 3) to move relative to one another, characterized by a mandrel (5) in one of the pressure plates (2), said mandrel functioning to form a connecting channel (33) as the blood container (1a) is compressed for the removal of the plasma fraction contained therein, said connecting channel (33) connecting the blood container outlet opening (17) with the bottom fraction, and said connecting channel (33) being formed only when the plasma fraction has been removed. 6. Apparatus according to Claim 5, characterized in that the mandrel (5) has the form of a U-shaped bar which projects out from the pressure plate (2). 7. Apparatus according to Claim 6, characterized in that the pressure plate (2) with the mandrel (5) includes a U-shaped groove (9) which is arranged outside the bar (5) and a U-shaped strip (4) which can be inserted into the groove and which is carried by springs (8); and in that the springs (8) project out of the groove (9) and beyond the bar (5) in an unloaded state and in a state in which the springs are loaded with a first selected pressure. 8. Apparatus according to Claim 6, characterized in that the strip (4) is provided on that side thereof remote from the pressure plate (2) with a channel (11 ) which permits fluid to pass when no load is exerted on the strip (4) or when the strip is subjected to pressure which is lower than the first selected pressure. 9. Apparatus according to one or more of Claims 5-8, characterized in that one pressure plate (2) covers at least the whole of the blood container (1 a) and the opposing pressure plate (3) covers the upper part of said blood container (1a). 10. Apparatus according to one or more of Claims 5-9, characterized in that the means (15) for effecting relative movement of the pressure plates has the form of bellows whose pressure area is greater than the projected area of the blood container (1a). [received by the International Bureau on 22 July 1993 (22.07.93) ; original claim 1 amended ; other cl aims unchanged ( 1 page ) ] 1. A method of separating blood into blood components, comprising introducing blood into a blood container which has at least one blood compo¬ nent outlet opening at the upper limit of the container, and centrifuging the blood container in a relatively high centrifugal field to form an upper plasma fraction, an intermediate buffycoat fraction and an erythrocyte fraction, characterized by applying pressure to the blood container for removal of plasma fraction through the outlet opening and forming in the blood container during or after this pressure stage a connecting channel through which a second fraction is connected with the outlet opening or with a second outlet opening; and applying a higher pressure for removal of the second fraction through the formed connecting channel. 2. A method according to Claim 1 , characterized by forming the connecting channel subsequent to having removed a desired quantity of plasma fraction. 3. A method according to Claim 1 or 2, in which the second fraction is the erythrocyte fraction, characterized by forming the connecting channel in a generally U-shape with the base of the connecting channel communicating with the outlet opening through which the erythrocyte fraction shall be removed and the legs of said channel connecting with the erythrocyte fraction. 4. A method according to one or more of Claims 1-3, characterized by applying the pressure for removal of the plasma fraction essentially on the upper part of the blood container. 5. Apparatus for removing blood components from a blood container (1 a) which has at least one outlet opening (17) and which contains blood that has been stratified into blood components by centrifugation, said apparatus includ¬ ing a housing (16) which has mounted therein a first and a second pressure plate (3, 2) which are movable relative to one another, a suspension means (50) for positioning the blood container (1a) between the pressure plates (2, 3), and means (15) for causing the pressure plates (2, 3) to move relative to one another, characterized by a mandrel (5) in one of the pressure plates (2), said mandrel functioning to form a connecting channel (33) as the blood container (1a) is compressed for the removal of the plasma fraction contained therein, said connecting channel (33) connecting the blood container outlet opening (17) with the bottom fraction, and said connecting channel (33) being formed only when the plasma fraction has been removed. 6. Apparatus according to Claim 5, characterized in that the mandrel (5) has the form of a U-shaped bar which projects out from the pressure plate (2). 7. Apparatus according to Claim 6, characterized in that the pressure plate

Inventors: UNGER PETER, WESTBERG ERIC, UNGER, PETER, WESTBERG, ERIC
Applicants: OMEGA MEDICINTEKNIK AB
Application year: 1993
Main classification: A61M1
IPC codes: A61M1