EP0038323A1

EP0038323A1 - A device for the separation of a liquid, especially whole blood.

Info

Publication number: EP0038323A1
Application number: EP79900655A
Authority: EP
Inventors: Lars-Ake Lennart Larsson; Claes-Ake Gullberg; Kaj Ove Stenberg; Nils Erik Gunnar Boberg
Original assignee: Gambro Lundia AB
Current assignee: Gambro Lundia AB
Priority date: 1979-06-06
Filing date: 1980-12-15
Publication date: 1981-10-28
Also published as: WO1980002653A1; ATE9766T1; EP0038323B1; DE2967251D1; JPS56500600A

Abstract

Device for the centrifugal separation of a liquid, especially whole blood, into fractions having different densities. Said device comprises a rotatable separation unit (5) comprising a separation chamber (5'), and a transferring element (2) in fluid communication with said chamber The transferring of said liquid and said separated fractions between a source for said liquid and said separation chamber is realized without use of rotating couplings in that one end (3) of said transferring element is held fixedly, while the other end (4) thereof, i.e. the end which is next to said separation chamber, is rotatably connected to said chamber. As well said separation unit as said transferring element thereby will perform a rotation, when said separation chamber is rotating around an axis through said one end of said transferring element. Said transferring element (2) is thereby prevented from twisting or winding. More precisely, said transferring element (2) and said separation unit (5) will rotate one revolution (secondary rotation) per revolution made by the separation unit (5) when rotating (primary rotation) around said axis through said fixedly held end (3). By suitable choice of ratio between radius (r) of said separation chamber and radius (R) of said primary rotation, i.e. the distance between said separation chamber and the axis through said fixedly held end, said secondary rotation may be used to separate said liquid already before said liquid enters into said separation chamber (5').

Description

TITLE

A DEVICE FOR THE SEPARATION OF A LIQUID, ESPECIALLY WHOLE BLOOD

TECHNICAL FIELD

This invention relates in general to a device for the separation of a liquid into fractions having different densities. Especially, this invention relates to a device for the separation of whole blood into for example red cells and plasma.

Conveniently, the present device is of the kind that is connectable to a patient to permit the whole blood to be continuously withdrawn from said patient, to be conducted through said device and then to be reinfused into said patient. During the passage through said device said whole blood is separated into for example red cells and plasma. For example said red cells are reinfused into a patient, while said plasma is separately collected.

To the above end the present device comprises a rotatable separation unit comprising a separation chamber, and a transferring element being in fluid communication with said chamber.

BACKGROUND ART To facilitate the understanding of the present invention it may be convenient to first illustrate the nature and character of whole blood. This should however not constitute a limitation of the present invention, but should rather be taken as a convenient instrument to understand the present invention when used in one of its more especial fields of use.

Whole blood is a tissue consisting of cells suspended in plasma. Said cells constitute about 45% by volume, while the remaining 55% constitutes plasma. Said suspended blood cells comprise inter alia red cells, white cells and thrombocytes. By means of the present device it is possible not only to separate cells from plasma, but also to separate said several cells from each other into separate cell fractions (so-called cytapheresis) if desired. Said separate fractions of said whole blood may be used independently for different purposes. For example said white cells are of particular concern for blood research, immunolcgical studies and for clinic use in transplantations of organs. Further more, said white cells may be used for support therapy by cancer patients, the white cells of which in one or another respect have been destroyed through different anti cancer drugs.

The red cells as well as the plasma are of particular concern for transfusion purposes.

Known devices for the separation of whole blood into different components have under favorable conditions provided a sufficient separation, but have, on the other hand, had drawbacks sometimes entailing fatal consequences for said whole blood and said separated components. The main reason has been the rotating coupling which normally is used to connect the transferring element to the rotating separation unit. Through the heat of fraction which is created in rotating couplings in the contact surface between a stationary and a rotating element, said whole blood has been exposed to heavy temperature increases during its passage into the separation chamber. This is also true for the separated blood fractions when said fractions have passed the rotating coupling during the flowing out of said separation unit. Even though said problem to some extent has been solved by cooling said rotating coupling with a cooling fluid, it still remains as being not completely solved. Another drawback by said known devices, which use rotating couplings, is that blood cells may be damaged due to shear-stresses at the contact between surfaces moving relatively to each other.

The object of the present invention is therefore to provide a device of the above-mentioned kind, i.e. a device which similar to said known devices for the separation of whole blood into fractions having different densities, uses a rotating separation unit comprising a separation chamber and a transferring element in fluid communication with said chamber. The present device, on the contrary, does not use rotating couplings to connect the separation unit to the transferring element.

DISCLOSURE OF INVENTION

The present device comprises a rotatable separation unit comprising a separation chamber, and a transferring element in fluid communication with said chamber. Said device is characterized in that one end of said transferring element is fixedly held, while the other end of said transferring element is rotatable together with said separation unit in a circular path around an axis through said one end. Due to the fact that said one end of said transferring element is held fixedly, i.e. is kept stationary, while said other end is rotatable together with said separation unit around an axis through said one end, the person skilled in the art realizes that said transferring element (as well as said separation unit) will rotate around said axis (primary rotation), and also around its own longitudinal axis (secondary rotation). Said primary and said secondary rotation thereby are so synchronized that any tending of said transferring element to be exposed to torsion or to be wound is counteracted. As regards said transferring element this fact apparently means that said transferring element will make one revolution around its own longitudinal axis per revolution around said axis through said one end of said transferring element. Preferably, said transferring element and said separation unit are firmly held together. Consequently, also said separation unit will perform a synchronized secondary rotation with said transferring element.

Said firm connection between said transferring element and said separation unit is achieved preferably by means of a tubular casing comprising a closed and an open end. Said casing thereby enclose at least one inlet tube for the liquid, to be separated, and at least one outlet tube for the respective fraction of said liquid. As well said inlet as said outlet tubes are terminating at short distance from the closed end of said casing while forming a separation chamber between the respective ends of said tubes and said closed end of said casing.

Preferably, said outlet tube for the heavy fraction is terminating next to said closed end of said casing, while the outlet tubes for successively lighter fractions are terminating at successively longer distance from said closed end. The inlet tube thereby is terminating at a longer distance from said closed end than the outlet tube for said heaviest fraction, but at a shorter distance from said closed end than the outlet tube for the lightest fraction. In the separation of whole blood into for example red cells and plasma the inlet tube for said whole blood conveniently is terminating into an area between the corresponding ends of the tubes for said red cells and said plasma, respectively. To ascertain a well balanced primary rotation the inlet tube for said liquid and the outlet tube for the respective fraction are preferably provided in a mirror symmetric relation with respect to the central longitudinal axis of said casing. This means that outlet tubes for one and the same fraction are located diametrically opposite to each other within said casing. Preferably, the inlet tube is located centrally.

According to another preferred. embodiment of the present invention said tubular casing encloses two concentric tubes. The inlet for the liquid, to be separated, is constituted by the annular space between the innermost tube and the intermediate tube. The outlet for the heaviest fraction is in the same way formed by the annular space between said intermediate tube and said casing, while the outlet for the lightest fraction is formed by the cavity within said innermost tube.

By analogy with the first embodiment said innermost tube is terminating at a longer distance from the closed of said casing compared to said intermediate tube.

The number of concentric tubes to be used depends in each separate case on the number of desired fractions. This preferred embodiment in general is very similar to said first embodiment and need therefore not be described in more detail Yet it is to be noted that suitable spacers may be provided between the tubes to keep said tubes in place. For example protruding heels, frame works and similar constructions may be provided on the outer surfaces of the inner tubes to prevent said tubes from contacting each other and thereby clogging said annular spaces or channels.

Alternatively, said firm communication between said transferring element and said separation unit is realized by means of a tubular body comprising a closed and an open end. Said tubular body comprises at least one inlet channel (longitudinal void) for the liquid, to be separated, and at least one outlet channel (longitudinal void) for the respective fraction of said liquid. Said channels are terminating at a distance from said closed end of said tubular body while forming a separation chamber between the respective ends of said channels and said closed end of said tubular body. Again, this alternative embodiment is very similar to said first embodiment and therefore need not be described more in detail. Still another embodiment of the present invention comprises a separation unit in the form of a separate hollow body in firm communication with said transferring element. Said hollow body is preferably molded and comprises cavities in communication with tubes or channels in said transferring element. As well said molded separation unit as said transferring element are conveniently encapsulated within a tubular housing comprising a closed and an open end. The principal difference between this embodiment and the embodiments described hereabove is that the separation chamber in this case is formed by cavities in an individual molded hollow body, while the corresponding chambers in the preceding embodiments are formed by the space between said transferring element and said closed end of said enclosing casing. Neither this embodiment should need to be discussed more in detail. Although not necessary, said separation unit conveniently is carried in a rotatable support casing which is adapted to be rotated together with said separation unit around said axis through said fixedly held end of said transferring element. Thereby is a smooth and vibration free primary rotation ascertained. As an extra matter of safety against vibrations and possible unbalances during said primary rotation said support casing is preferably driven by means of separate driving means which in turn are adapted to be driven synchronically to the secondary rotation of said transferring element. Said driving means are preferably coupled to the motor that provides for the primary rotation of said transferring element.

Preferably, said transferring element is provided in curved path and supported in this position by means of suitable supporting means. As well said support casing as said separation unit may be manufactured from transparent material making it possible to visually (for example by means of a stroboscope) watch the separation of whole blood within said separation chamber. Finally, said transferring element may comprise flowing channels for a cooling liquid, for example salt solution, which is adapted to withdraw heat that may be generated through shearing in said transferring element due to bending of tubes in said secondary rotation. The present invention will be described in more detail with reference to the accompanying drawings, wherein

Fig. 1 is a schematic view of the present device together with suitable accessories,

Figs. 2-4 are cross-sections of preferred transferring elements according to the present invention, Fig. 5 is a schematic illustration, partly in section, of a preferred transferring element in firm communication with a separation unit,

Figs. 6-8 are cross-sections of the transferring element and the separation unit of Fig. 5 along lines VI-VI, VII-VII and VIII-VIII in Fig. 5,

Fig. 9 is a schematic illustration, partly in section, of a second preferred transferring element in communication with an individual separation unit, taken along lines IX-IX in Figs. 10-15,

Figs. 10-15 are cross-sections of the separation unit and the transferring element of Fig. 9, taken along lines X-X, XI-XI ... XV-XV,

Fig. 16 is a schematic view, partly in section, of a further transferring element according to the present invention, taken along lines XVI-XVI in Figs. 17-19, and wherein Figs. 17-19 are cross-sections of the transferring element of Fig. 16, taken along lines XVII-XVII, XVIII-XVIII and XIX-XIX in Fig. 16. As is shown in Fig. 1, the present device, generally designated 1, comprises a transferring element 2 which at its one end 3 is held fixedly and at its other end 4 is connected to a separation unit 5 comprising a separation chamber 5'. Said separation unit 5 is preferably carried in a support casing 6 which is rotatable around its own longitudinal axis by means of a bearing 7, 8.

Between its two ends 3 and 4 said transferring element 2 is provided in a curved path and kept in this position by means of a stand 9 and suitable support bearings 10, 11 being attached to said stand and permitting said transferring element 2 to rotate freely around its own longitudinal axis. Said stand 9 is carried on a stationary support plate 12 and is rotatable around an axis through said fixedly held end 3 of said transferring element. Said axis is designated I-I in Fig. 1. The rotation around said axis I-I is provided by means of a not shown drive motor via a drive shaft 9c which is carried in a bearing 9a in a supporting means 9b.

To the right part (not shown) of said stand 9 in Fig a counter-weight may be provided to balance said transferring element 2 and said separation unit 5, when said stand 9 is rotating. Thereby, vibrations due to asymmetric weight distribution are avoided.

Said separation unit 5 as well as said support casing 6 are preferably transparent. Thereby it is possible to visually (for example by means of a stroboscope) watch the separation and, if necessary, to control the rotation speed, so that the best possible separation is achieved. Alternat- ively, said separation may be controlled by controlling the introducing and/or withdrawing of liquid in said differen inlet and outlet tubes. For example, if whole blood is to be separated into plasma. and red cells and the volume of plasma within said separation chamber apparently is too big, then said volume may be reduced by either increasing the withdrawing of plasma or by reducing the withdrawing red cells. Polyvinylchloride (PVC) is a suitable transparent material.

A further way of controlling said separation comprises the choice of a suitable rotation radius R from said axis I-I. Depending on the liquid, to be separated, it may be convenient to use a larger or smaller ratio between radius r of said separation chamber 5' and radius R of the primary rotation of said separation chamber 5', i.e. the distance between said axis I-I and said separation unit 5. In the separation of whole blood into red cells and plasma, said ratio conveniently is between 30:1 and 15:1. In this way the influence of the secondary rotation of said separation unit on said separation may be more or less used and thereby the separation be initiated already prior to entering into said separation chamber 5'. To avoid unbalances due to vibrations of said support casing 6, said casing may be driven separately by means of schematically shown drive means, generally designated 13, which are synchrcnically driven by the not shown drive motor for said stand 9 .

In Figs . 2-4 suitable cross-sections are shown, which may be used for said transferring element 2.

In Fig. 2 said transferring element consists of a tubular body 2a having perforating holes or channels 14a, 14a', 15a, 15', 16a, 16a' and 17a. As is shown in Fig. 2 said channels are preferably mirror symmetrically provided to the central longitudinal axis of said tubular body 2a. In the separation of whole blood said channels 14a, 14a' constitute inlet channels for said whole blood, while said channels 15a, 15a' and 16a, 16a' constitute outlet channels for the red blood cells and the plasma , respectively . The central channel 17a may either form a third inlet channel for said whole blood, or a separate flowing channel for cooling liquid, if necessary.

In Fig. 3 said transferring element consists of a tubular housing 2b enclosing six individual tubes 14b, 14b', 15b, 15b', 16b, 16b'. Said tubes are mirror symmetrically provided around the central longitudinal axis of said casing and attached to each other to maintain the shown position.

Said tubes form in pairs inlet and outlet tubes for the whole blood and the separated fractions, respectively. For example, said tubes 14b, 14b' are inlet tubes for said whole blood, while the tubes 15b, 15b' and 16b, 16b' are outlet tubes for red blood cells and plasma, respectively.

The space 17b between said tubes and said casing 2b forms flowing channels for a cooling liquid, for example isotonic 0.9% NaCl solution.

In Fig. 4 said transferring element consists of an outer tubular casing 2c enclosing concentric tubes 16c, 18c. Said casing 2c and said tubes 16c and 18c thereby form annular spaces or channels 14c, 15c. Said annular space 15c between said casing 2c and the intermediate tube 18c forms preferably outlet channel for the heaviest fraction (red blood cells), while the annular space 14c between said intermediate tube 18c and the innermost tube 16c forms preferably inlet tube for said whole blood. The cavity in the innermost tube 16c consequently forms outlet channel for said plasma. As mentioned before the number of concentric tubes, to be used, may vary from case to case and is depending on the number of fractions that is desired.

To maintain the concentric arrangement of said casing 2c and said tubes 16c and 18c, said intermediate tube 18c may be provided with protruding heels 19c abutting the inner surface of said casing 2c and the outer surface of the inner most tube 16c, respectively. Thereby is avoided that said tubes will contact each other and clog the annular spaces 14c and 15c, when said transferring element is rotating around said axis I-I. As well said tubular body 2a as said casings 2b and 2c are manufactured from a flexible material. A preferred example of such material is silicon rubber which is also sufficiently firm to withstand shearing due to the primary rotation of said transferring element. The transferring element and the separation unit shown in Figs. 5-8 correspond generally to the transferring element shown in Figs. 1 and 4. The same reference numbers as those in Figs. 1 and 4 have therefore been used, except for the addition of the letter "d" instead of the letter "c". In Fig. 5 said separation unit is designated 5d, said separation chamber is designated 5d' and said transferring element (including said tubular casing) is designated 2d. Reference is also made to the above description in connection with Fig. 4. The transferring element and the separation unit of Figs. 9-15 differ from the construction shown in Fig. 5 primarily in that said separation unit 5e is formed as a separate molding unit. Said transferring element 2e has in general the same cross-section as that of Fig. 3. For similar parts, the same reference numbers have therefore been used, except for the addition of the letter "e". The channels in said separation unit 5e have therefore been designated in the same way as the corresponding tubes in the transferring element 2e, except for the addition of double prim and triple prim.

The transferring element 2f (including the separation unit 5f) of Fig. 16 is the simplest possible realization of said transferring element having the cross-section shown in Fig. 3. The same reference numbers as those in Fig. 3 have therefore been used, except for the addition of the letter "f". Thus, the transferring element comprises only three tubes, designated 14f, 15f, 16f. The inlet tube for the liquid, to be separated, is designated 14f , while the outlet tubes for the red cells and the plasma are designated 15f and 16f, respectively.

In connection with Fig. 5 the operation of the present device will be described when used in the separation of whole blood. Said whole blood, to be separated into red blood cells and plasma, is introduced through the annular space 14d between the innermost tube 16d and the intermediate tube 18d. Due to the secondary rotation of said transferring element, shown by the arrow to the left of Fig. 5, said whole blood will be exposed to preseparation prior to entering into said separation chamber 5d' in such a manner that said plasma tends to concentrate towards the longitudinal axis of said transferring element 2d, while the heavier red blood cells correspondingly tend to concentrate away from said longitudinal axis within said space 14d. The so partly separated whole blood enters into said separation chamber 5d', where the proper separation occurs. Due to the centrifugal forces the heavier red blood cells will be concentrated peripherially outwardly (to the left of Fig. 5), while the lighter plasma will be concentrated towards the centre and will enter into the cavity in said outlet tube 16d. The flowing conditions for said whole blood, said red cells and said plasma are shown by arrows in Fig. 5. Due to the fact that whole blood is continuously introduced into said space 14d the separated red blood cells and the plasma correspondingly are continuously withdrawn through the annular space 15d and the cavity in sa'id outlet tube 16d, respectively. Since neither the way in which said whole blood is introduced into said transferring element 2d and said separation unit 5d or the way in which the separated fractions are withdrawn from said unit constitute any essential part of the present invention, no further description thereof is therefore needed. Briefly, the arrangement 20 of Fig. 1 corresponds in general to the construction of Figs. 9-15. The same reference numbers for similar parts have therefore been used, yet without the addition of any letter.

Even if the present invention has been described with particular reference to the separation of whole blood, it is to be understood that the present invention is as well applicable to other liquids, containing fractions of different densities, which are to be separated into said fractions.

INDUSTRIAL APPLICABILITY

As is realized from the above description, the present device is especially, though not exclusively, useful in the separation of whole blood into for example red blood cells and plasma. Said whole blood is thereby continuously introduced into said device from an outer source, for example patient, and is separated under the influence of centrifugal forces in a rotatable separation unit. The separated fractions, red blood cells and plasma, are withdrawn from said separation chamber within said separation unit through individual tubes and are reinfused into said patient or are collected selectively. Due to the fact that one end of said transferring element is held fixedly, while the other end thereof (i.e. the end which is in fluid communication with said separation chamber) is rotatably connected to said chamber, rotating couplings are thereby avoided, which due to heat of friction may expose said blood and the separated fractions to excessive and detrimental temperature increases and/or detrimental shear stresses.

Claims

1. A device for the separation of a liquid, especially whole blood, into fractions having different densities, said device comprises a rotatable separation unit (5) comprising a separation chamber (5'), and a transferring element (2) in fluid communication with said chamber, characterized in that one end (3) of said transferring element (2) is held fixedly, while the other end (4) thereof is rotatable together with said separation unit (5) in a circular path around an axis (I-I) through said one end (3).

2. A device in accordance with claim 1, characterized in that said transferring element (2) and said separation unit (5) are firmly connected to each other. 3. A device in accordance with claim 1 or 2, characterized in that said transferring element (2) and said separation unit (5) are connected to each other by means of a tubular casing (2b; 2f) having a closed and an open end and enclosing at least one inlet tube (14b, 14b'; 14f) for the liquid, to be separated, and at least one outlet tube (15b, 15b', 16b, 16b'; 15f, 16f) for the respective fraction of said liquid, wherein said tubes are terminating at a distance from said closed end of said casing while forming a separation chamber (5f') between the respective ends of said tubes and said closed end of said casing (for example Figs.

3 and 16-19).

4. A device in accordance with claim 3, characterized in that said outlet tube (15b, 15b' , 15f) for the heaviest fraction is terminating next to said closed end of said casing (2b; 2f) and in that the outlet tubes (16b, 16b'; 16f) for successively lighter fractions are terminating at successively longer distances from said closed end, wherein the inlet tube (14b, 14b'; 14f) is terminating at a longer distance from said closed end than said outlet tube (15b, 15b'; 15f) for said heaviest fraction, but at a shorter distance from said closed end than said outlet tube (16b, 16b'; 16f) for said heaviest fraction.

5. A device in accordance with claim 3 or claim 4, characterized in that said inlet tube (14b, 14b') for said liquid and/or said outlet tubes (15b, 15b', 16b, 16b') for the respective fraction are mirror symmetrically provided to the central longitudinal axis of said casing (2b) (for example Fig. 3).

6. A device in accordance with any one of claims 3-5 characterized in that the space (17b) between said tubes (14b, 14b', 15b, 15b', 16b, 16b') within said casing (2b) forms flow channels for cooling liquid, for example salt solution.

1. A device in accordance with claim 3, characterized in that said tubular casing (2c; 2d) encloses two concentric tubes (16c, 18c; 16d, 18d), wherein the inlet for the liquid is constituted by said annular space (14c; 14d) between the innermost tube (16c; 16d) and the intermediate tube (13c; 18d), wherein said outlet for the heaviest fraction preferably is constituted by said annular space (15c; 15d) between said intermediate tube (18c; 18d) and said casing (2c; 2d), and wherein said outlet for the lightest fraction preferably is constituted by the cavity in the innermost tube (16c; 16d) (for example Figs. 4 and 5) .

8. A device in accordance with claim 7, characterized in that the innermost tube (16c; 16d) is terminating at a longer distance from said closed end of said casing (2c; than said intermediate tube (18c; 18d).

9. A device in accordance with claim 2, characterized in that said transferring element (2) and said separation unit (5) are connected to each other by means of a tubular body (2a) comprising a closed and an open end and comprising at least one inlet channel (14a, 14a') for the liquid, to be separated, and at least one outlet channel (15a, 15a', 16a, 16a') for the respective fraction of said liquid, wherein said channels are terminating at different distances from said closed end of said tubular body (2a) while form a separation chamber between the respective ends of said channels and said closed end of said tubular body (for example Fig. 2).

10. A device in accordance with claim 9, characterized in that said outlet channel (15a, 15a') for said heaviest fraction is terminating next to said closed end of said tubular body (2a) and in that said outlet channels (16a, 16a') for successively lighter fractions are terminating at successively longer distances from said closed end, wherein said inlet channel (14a, 14a') is terminating at a longer distance from said closed end than said outlet channel (15a, 15a') for said heaviest fraction, but at a shorter distance from said closed end than said outlet channel (16a, 16a') for said lightest fraction.

11. A device in accordance with claim 9 or 10, characterized in that said inlet channel (14a, 14a') for said liquid and said outlet channels (15a, 15a', 16a, 16a') for the respective fractions are mirror symmetrically provided to the central longitudinal axis of said tubular body (2a).

12. A device in accordance with any of claims 7-11, characterized in that said tubular body (2a) comprises one or more flow channels (17a) for a cooling liquid, for example salt solution.

13. A device in accordance with claim 2, characterized in that said separation unit (5e) is formed as an individual hollow body in firm connection to said transferring element (2e) (for example Fig. 9).

14. A device in accordance with any one of claims 1-13, characterized in that said separation unit (5) is carried in a rotatable support casing (6) .

15. A device in accordance with claim 14, characterized in that said support casing (6) is adapted to be driven by means of separate driving means (13) which in turn are adapted to be synchronically driven in relation to the secondary rotation of said transferring element (2).

16. A device in accordance with claim 15, characterized in that said transferring element (2) is provided in a curved path and carried in this position by means of suitable support means (10, 11).

17. A device in accordance with claim 16, characterized in that as well said support casing (6) as said separation unit (5) are manufactured from transparent material.