PatentDe  


Dokumentenidentifikation EP0702593 19.02.1998
EP-Veröffentlichungsnummer 0702593
Titel VORRICHTUNG UND VERFAHREN ZUR TRENNUNG VON PLASMA AUS EINEM BLUTPRODUKT
Anmelder Pall Corp., East Hills, N.Y. 11548, US
Erfinder BALL, Peter Robert, Langrish, Hampshire GU32 1PH, GB;
HALL, Christopher Clement, Havant, Hampshire PO9 1AX, GB;
BOULTER, Eileen Margaret Ann, Northend, Portsmouth PO2 9EQ, GB
Vertreter Grießbach und Kollegen, 70182 Stuttgart
DE-Aktenzeichen 69407969
Vertragsstaaten DE, DK, FR, GB, IE, IT, NL, SE
Sprache des Dokument En
EP-Anmeldetag 10.06.1994
EP-Aktenzeichen 949171276
WO-Anmeldetag 10.06.1994
PCT-Aktenzeichen GB9401256
WO-Veröffentlichungsnummer 9429008
WO-Veröffentlichungsdatum 22.12.1994
EP-Offenlegungsdatum 27.03.1996
EP date of grant 14.01.1998
Veröffentlichungstag im Patentblatt 19.02.1998
IPC-Hauptklasse B01D 69/02

Beschreibung[en]

The invention relates to a device and method for separating blood cells from plasma or from another fluid in which cells are suspended.

An adult human contains about 5 litres of blood, of which red blood cells, also referred to as erythrocytes, account for about 45% of the volume, white cells about 1% and the balance being liquid blood plasma in which the cells are suspended. Blood also contains large numbers of platelets suspended in the plasma (their proportional volume is small). In view of the substantial therapeutic and monetary value of blood components, such as red blood cells, platelets and plasma, a variety of techniques have been developed to separate blood into its component fractions or to separate combinations of such components while ensuring maximum purity and recovery of each of the components.

Throughout this specification the term blood product will be used to refer to anticoagulated whole blood or suspensions of red blood cells (with or without other blood cell types) in a suitable fluid such as plasma or SAG-M (whose composition is detailed below).

In general, such separations have been achieved by centrifugation techniques. This requires, however, significant handling of the blood product, which can increase the risk of disease transmission. In addition, centrifuging also takes significant time.

An alternative to centrifugation for the separation of red blood cells, white blood cells and platelets from plasma or another fluid in which the cells are suspended is filtration. This can be achieved by flowing a blood product across a surface of a membrane whereupon plasma or another cell suspending fluid passes through the membrane under a pressure gradient generated across the membrane. This process is hereinafter referred to as cross-flow filtration. It has been found, however, that the filtration efficiency of such a membrane drops because the membrane pores become blocked with blood cells and cell fragment debris during filtration. Blocking cells and debris may not be effectively removed by cross-flow of the blood product across the surface of the membrane. As a result, the membranes previously used for such filtration have blocked before the haemocrit (the percentage of red blood cells in the suspending fluid) reaches a desired figure, for example 70% by volume.

In EP-A-464707, this problem is sought to be overcome by a shearing force induced at the membrane surface by forming the membrane as a cylinder and rotating it within a non-rotating outer cylinder whose walls are in close proximity to the rotating membrane. This process generates so-called "Taylor Vortices" which are intended to clear the membrane surface of clogging cells and debris and to provide increased trans-membrane pressure to increase plasma flow across the membrane.

A similar proposal for overcoming this problem is made by Beaudoin and Jaffrin in the article "Plasma Filtration in Couette Flow Membrane Devices" in the Journal "Artificial Organs" Volume 13 No.1 1989 pages 43-51.

EP-A-0111423 endeavours to induce vortices in the flow using dimples formed on the surface of the membrane.

These approaches suffer from certain technical limitations. The proposal of EP-A-0111423 requires very precise alignment of the "dimples". Failure to achieve this will degrade the effectiveness of the device. The approaches of Beaudoin and Jaffrin and EP-A2-464707 require accurate alignment of the rotating and non-rotating cylinders and additionally require an electric motor to rotate the rotating cylinder which increases the expense and complexity of the device.

In all these proposals for plasma separation by filtration, it is essential that there is no or no significant lysis of erythrocytes in the blood product, since this releases haemoglobin. Since this is a protein, it can pass freely across the membrane with the other non-cellular components of the blood. Free haemoglobin (i.e. haemoglobin not contained within the erythrocyte cell membrane) is potentially undesirable, especially where the plasma is required for therapeutic purposes. Additionally, erythrocyte lysis produces cell fragments which can block the membrane pores.

Such lysis can be avoided or mitigated by the use of membranes with very small pore sizes (≤0.1µm)i.e. considerably smaller than is required simply to prevent erythrocytes crossing the membrane. However, such membranes currently in use do not allow flow rates of plasma across the membrane that are sufficiently high to make separation of the plasma by filtration a viable option - particularly when compared to centrifuging.

EP-A1-0100285 discloses semi-permeable hollow fibres for the treatment of blood by haemodialysis and ultrafiltration. The fibres are less than 500µm in diameter and have smooth interior surfaces to prevent the hooking of shaped blood elements onto the interior fibre surfaces to prevent clogging.

According to a first aspect of the invention, there is provided a cross-flow device for treating a blood product comprising red blood cells suspended in a fluid to separate the fluid from the cells, the device including a manifold having an inlet for the blood product and an outlet for fluid depleted cells, a membrane extending across the manifold to one side of the blood product inlet and the depleted-cell outlet, the membrane having first and second spaced surfaces separated by a porous structure with the first surface facing into the manifold and contacted by blood product flowing between the blood product inlet and the depleted cell outlet, the membrane having a voids volume of at least 50% and the first surface having a smoothness of less than 0.5µm as measured by a Mitutoyo Surftest 401 tally surf machine as the average deviation in directions normal to said surface of the position of the stylus of said machine from a mean position of the stylus as the stylus is drawn across said surface, an outlet being provided for separated fluid, said outlet facing said second membrane surface.

According to a second aspect of the invention, there is provided a cross-flow device for treating a blood product comprising red blood cells suspended in a fluid whereby to separate the fluid from the cells, the device comprising a housing having an inlet for the blood product, an outlet for fluid depleted cells, an outlet for fluid and a membrane disposed in the housing, the membrane having first and second spaced surfaces separated by a porous structure with the first surface facing into the housing and contacted by blood product flowing between the blood product inlet and the depleted cell outlet, the fluid outlet facing said second membrane surface, the membrane having a pore size of less than 0.65 µm, and wherein the volume of fluid separated over 15 minutes is greater than 0.6 ml per unit area in cm2 of the said first surface when the device is used to treat a volume corresponding to 3.75 ml per unit area in cm2 of the said first surface of red blood cells suspended in an aqueous solution of 140 mmol/l sodium chloride, 1.5 mmol/l adenine, 50 mmol/l glucose and 30 mmol/&litre; mannitol at a haematocrit of 45%, and when the transmembrane pressure difference is 35 mbar, the first membrane surface having a smoothness of less than 0.5 µm as measured by a Mitutoyo Surftest 401 tally surf machine as the average deviation in directions normal to said surface of the position of the stylus of said machine from a mean position of the stylus as the stylus is drawn across said surface.

According to a third aspect of the invention, there is provided a method of treating a blood product comprising red blood cells suspended in a fluid whereby to separate the fluid from the cells comprising flowing the blood product across a first surface of a sheet of membrane material having spaced first and second surfaces separated by a porous structure, filtering the blood product through the porous structure of the sheet of membrane, the membrane having a voids volume of at least 50% and the first surface having a smoothness of less than 0.5µm as measured by a Mitutoyo Surftest 401 tally surf machine as the average deviation in directions normal to said surface of the position of the stylus of said machine from a mean position of the stylus as the stylus is drawn across said surface.

According to a fourth aspect of the invention, there is provided a method of treating a blood product comprising red blood cells suspended in a fluid whereby to separate the fluid from the cells comprising flowing the blood product across first surface of a sheet of membrane material having spaced first and second surfaces separated by a porous structure, the membrane having a pore size of less than 0.65µm and the first surface of the sheet of membrane material having a smoothness of less than 0.5µm as measured by a Mitutoyo Surftest 401 tally surf machine as the average deviation in directions normal to said surface of the position of the stylus of said machine from a mean position of the stylus as the stylus is drawn across said surface, and wherein the volume of fluid separated over 15 minutes is greater than 0.6 ml per unit area in cm2 of the said first surface when a volume of blood product corresponding to 3.75 ml per unit area in cm2 of the said first surface is being treated, and when the transmembrane pressure difference is 35 mbar.

The following is a more detailed description of some embodiments of the invention, by way of example, reference being made to the accompanying drawings in which:

  • Figure 1 is a cross-section of a device for separating plasma from blood,
  • Figure 2 shows two traces from a Mitutoyo Surftest 401 surftest machine, the upper trace being the surface trace from a smoother membrane and the lower trace the surface trace of a less smooth membrane,
  • Figure 3 is a graph plotting against time, firstly plasma flow rate (left hand y-axis) and secondly haematocrit (right hand y-axis) for an example of a blood product filtered through a membrane,
  • Figure 4 is a graph plotting the amount of haemoglobin in the plasma against time for the Example of Figure 3.

Referring to Figure 1, the device comprises a plasma outlet member 10, a manifold 11 and an insert 12.

The plasma outlet member 10 has a generally annular base 13 with a flat upper surface 14. A plasma outlet 15 leads from the centre of this surface 14 and connects with a passage 16 which terminates at an outer surface of the plasma outlet member 10.

The flat upper surface 14 is surrounded by an annular wall 17 which in turn leads to an annular L-shaped rebate 18 extending around the surface 14.

The manifold 11 has an annular body 19 which is co-axial with the axis of the surface 14 and the wall 17 and rebate 18 and is received in the L-shaped rebate 18 and includes an outer axially extending annular surface 20 carrying an annular seal 21 which seals against the axial surface of the L-shaped rebate 18.

The manifold 11 also includes a depending annular flange 22 having an annular outer wall 23 in contact with the annular wall 17 of the plasma outlet member 10.

The manifold 11 includes a blood inlet 24 and a blood outlet 25. The blood inlet 24 includes a passage 26 extending through the body 19 at an angle to the axis of the manifold 11 and leading to a passage 27 which extends through the flange 22 in a direction parallel to the axis of the manifold and which terminates at an outlet 28 adjacent the flat upper surface 14 of the plasma outlet member.

The blood outlet member 25 is formed with an inlet 29 adjacent the flat upper surface 14, a first passage 30 extending through the flange 22 and a second passage 31 extending through the body 19 at an angle relative to the axis of the manifold 11.

The manifold 11 carries the insert 12 which is generally cylindrical in shape and co-axial with the manifold axis with an outer cylindrical wall 32 carrying a seal 33 which contacts an inner annular wall of the manifold 11 to form a seal therebetween. The insert 12 also has a circular head 35 provided with ports 36a,36b. One port 36a extends through the head 35 and is coaxial with the common axis of the manifold 11. This central port 36a is also in alignment with the axis of the plasma outlet 15. The other ports, 36b, are arranged around the junction between the head 35 and the cylindrical wall 34 of the insert 12 and are at an angle to the common axis 37.

A lock nut 38 is in threaded engagement with the outer wall 34 of the insert 12 to allow the gap between the head 35 and the flat upper surface 14 to be adjusted.

An annular seal 39 extends around the outer periphery of the flat upper surface 14 and engages an outer edge of the flange 22 - but is separated from an inner edge of the flange 22 as seen in the drawing to provide a flow path therebetween.

In use, the device is disassembled by removing the manifold 11 and the insert 12 from the plasma outlet member 10. An annular disc of membrane material is then placed on the flat inner surface 14 with its axis coaxial with the axis of the plasma outlet 15 such that the membrane surface across which the blood product is to flow is positioned upwards. The diameter of the membrane 40 is such that its outer periphery contacts the inner periphery of the annular seal 39.

The manifold 11 and the insert 12 are then re-engaged with the plasma outlet member 10 and the position of the head 35 relative to the flat inner surface 14 is adjusted to a desired spacing by use of the lock nut 38.

After prewetting of the membrane with saline a blood product is then passed or circulated across the upper surface of the membrane 40; passing from the blood inlet 29 to the blood outlet 28. The pressure gradient across the membrane 40 maintains a flow of plasma or another fluid in which the cells are suspended through the membrane which then leaves via the plasma outlet 15 and the passage 16.

The blood flow can be provided by a peristaltic pump or a syringe pump or may also be provided by the use of air or mechanical pressure applied to a container of blood product.

A known device for testing ultrafiltration membranes is sold by Rhone Poulenc under the trade mark RAYFLOW PLEIADE as a cross flow filtration jig. A housing contains two membranes carried on respective opposite faces of a support. The product to be filtered is flowed across the surfaces of the membranes not contacting the support from respective inlets to respective outlets, and the filtrate is extracted from the support.

It has heretofor been thought that the only significant parameter for a membrane suitable for separating plasma from a blood product is the pore size which, as discussed above, has been required to be small enough to prevent erythrocytes passing through the membrane and to prevent haemolysis. However, as also discussed above, it has been found in previous membranes used for plasma separation and meeting this requirement, that the plasma flow rate is not sufficiently high to make such separation commercially viable.

The separation of plasma from a blood product at useful plasma flux rates and with the avoidance of lysis requires, it is herein postulated, a combination of the smoothness of the membrane surface contacted by the blood product and the structure of the membrane - the structure determining the rate at which a plasma passes through the membrane.

The pore size determines the sizes of particles that will be allowed to pass through the membrane. However, the flow rate of plasma through a membrane is also controlled by the structure of the membrane including internal structure of the pores. Accordingly, it has been found that membranes of different constructions but having the same pore size have differing flow rates.

Flow rate of plasma is important in crossflow plasma separation devices because it is naturally desirable to separate the plasma as rapidly as possible. In addition, a crossflow device is only likely to be commercially acceptable if the processing time for a blood product is no longer than that of a centrifugal separator (for example a haematocrit of 70% in 10-15 minutes).

One accepted measure of the "openness" of the internal structure of a membrane is the "voids volume" (porosity) of the membrane. This is the percentage of the membrane volume which is not occupied by the polymer substrate. The voids volume of membranes can vary from as little as 5% to in excess of 80%.

It has been found, however, that membranes which have high voids volumes (above 50%) and so have acceptable flow rates also have such a tendency to cause lysis when filtering plasma from a blood product, that the quantity of haemoglobin in the plasma is so great as to be unacceptable. It is believed that this is due to the fact that membranes with higher flow rates also have a more "open" surface structure which can provide sites where erythrocytes can be subject to lysis and the release of haemoglobin, and where cellular debris can collect and block the pores.

It is now believed that this problem can be mitigated by increasing the smoothness of the surface of the membrane in contact with the blood product. It is believed that this reduces the incidence of lysis and the collection of cell debris by removing sites on the membrane surface responsible for such effects.

The device described above with reference to Figure 1 and the RAYFLOW PLEIADE device referred to above were used to perform comparative tests on various different materials for the membrane. In broad terms, the tests were divided into two groups. In the first tests, using the RAYFLOW PLEIADE device, a membrane in accordance with the invention was tested against a commercially available membrane for filtration of blood products and a control membrane. The tests are for demonstrating that, although in both the membrane in accordance with the invention and the commercially available membrane, lysis of the blood product was kept at an acceptably low level, the time-averaged flow rate of plasma per unit area of the membrane was higher in the membrane in accordance with the invention than in the commercially available membrane.

In the second tests, using the device of Figure 1, a membrane in accordance with the invention was tested against membranes having similar pore sizes and flow rates but having a less smooth surface in contact with the blood product. The purpose of the test was to show that the membranes with less smooth surfaces produce unacceptable lysis.

In these tests, various measurements were used, as follows.

PLASMA FLUX RATE

The average rate of flux of plasma or of another suspending fluid such as SAG-M (PFR) across a membrane is referred to as the plasma flux rate (PFR) and was measured as the volume in millilitres of plasma or fluid (Vp) produced by the device over a set time period (t) in minutes per unit area (A) in cm2 of the membrane being tested. Thus PFR = Vp / (tA) ml / (min.cm2)

The rate is measured using a set volume (Vb) of blood product because as plasma is extracted from the blood product the flow characteristics change so that a time averaged plasma flow rate will be greater from a greater volume of blood product than from a lesser volume of blood product. Additionally it is necessary to define the surface area of the membrane across which the blood product passes as the extraction of plasma will occur faster with a larger surface area.

HAEMOLYSIS

The degree of haemolysis (H) is measured as the content of haemoglobin in the plasma or other cell suspending fluid produced by the device. This can be measured subjectively by a visual inspection of the plasma (which will become increasingly red as the volume of haemoglobin in the plasma increases) or can be measured by known methods in milligrammes of haemoglobin per millilitre of plasma or other fluid. In the former case, the degree of haemolysis can be expressed either as "-" (meaning no observed haemolysis) to "+++++" (meaning severe haemolysis), with values in between being expressed by from "+" to "++++".

BLOOD PRODUCT

The tests were conducted using a blood product which was either anticoagulated whole blood or blood cells suspended in SAG-M. SAG-M is an aqueous additive solution containing sodium chloride 140 mmol/l, adenine 1.5 mmol/l, glucose 50 mmol/l and mannitol 30 mmol/l. Blood cells (mostly red blood cells) were separated from anticoagulated whole blood by conventional centrifugation techniques and suspended in SAG-M to give a haematocrit value similar to that of whole blood (approximately 45%).

BLOOD VELOCITY

The tests were conducted with the whole blood or the cell suspension in SAG-M pumped through the device by a pump which produces a known flow rate (F) of whole blood or SAG-M through the device. F was measured in metres/second. The blood velocity is a significant parameter because increasing the blood velocity tends to prevent debris from attaching to the membrane surface and so increases PFR.

TRANSMEMBRANE PRESSURE

The transmembrane pressure (P) was maintained at a known level measured in mbar g, which is determined by the blood flow rate through the device and the restrictions on the outlet for the blood product and the plasma outlet.

SMOOTHNESS

The smoothness of a membrane surface was measured using a Mitutoyo Surftest 401 tally surf machine sold by Mitutoyo (UK) Company Limited. In such a machine a stylus is drawn across the surface of the membrane being measured and variations are measured in the position of the stylus in directions normal to the surface. The smoothness of the surface is quantified by an average deviation of the stylus position from a mean position in µm. When used in this specification, a measurement "smoothness" means a measurement made in this way.

The first group of tests using the RAYFLOW PLEIADE device will now be described. They are designed to demonstrate that a device in accordance with the invention has a superior plasma flux rate (PFR) as compared with another membrane previously used for plasma filtration, even though, in both cases, the degree of lysis was acceptable. A control membrane was also tested.

Example 1 - Invention

The membrane material used was a 0.2µm pore size nylon 66 membrane sold by Pall Corporation under the trade mark ULTIPOR N66 and cast on Mylar film as described in U.S. Patent No. 4340479. After casting two pieces of membrane were peeled off the Mylar and heat bonded together in face to face contact with the Mylar cast surface outwards.

The blood product was repeatedly passed through the RAYFLOW PLEIADE device over the course of the experiment - the suspension of cells emerging from the device being recirculated through the pump and back to the device. The other test conditions were as follows:

  • Vb = 450ml
  • t = 15 minutes
  • A = 120 cm2
  • Blood product = blood cells suspended in SAG-M
  • Blood velocity (F) = 0.33m/sec
  • Transmembrane pressure (P) = 35 mbar g

The resultant PFR is shown in Table 1 below.

Example 2 - Control Membrane

The membrane material used was a 0.2µm pore size nylon 66 membrane sold by Pall Corporation under the trade mark ULTIPOR N66 and not cast on a Mylar film. The remaining test conditions were as in Example 1.

The resultant PFR and haemolysis are shown in Table 1 below.

Example 3 - Prior Art - Known Plasma Separation Membrane

The membrane material used was a commercially available 0.2µm pore size polycarbonate membrane used for plasma separation. The remaining test conditions were as in Example 1.

The resultant PFR is shown in Table 1 below. EXAMPLE NO. PFR VOIDS VOLUME 1 0.119 > 70% 2 0.079 > 70% 3 0.036 < 50%

It will be seen that the membrane of Example 1 had a significantly greater PFR than the membranes of Examples 2 and 3. As noted above, the membrane of Example 1 was a membrane of nylon 66 cast on Mylar and sold by Pall Corporation under the trade mark ULTIPOR. This nylon 66 membrane is characterized by having a comparatively high internal voids volume (70% or greater) and a comparatively high density of surface pores with no substrate. The membrane of Example 3 has a lower voids volume and/or has a comparatively low density of surface pores or has a substrate. These factors tend to reduce significantly the PFR. The membranes produced acceptable levels of lysis with the exception of Example 2 which was used as a control.

It will also be appreciated that the PFR achieved by Example 1 requires only the transmembrane pressure created by blood flow between a stationary membrane and a stationary adjacent surface. The PFR does not rely on the use of increased blood velocities arising from relative motion between the membrane and the adjacent surface, as proposed, for example, in EP-A-464707.

The second group of tests using the device of Figure 1 will now be described. As mentioned above, they are designed to show that, without a comparatively smooth surface in contact with the blood product, lysis of erythrocytes occurs to an unacceptable extent, even though the flowrate through those membranes is acceptably high.

Example 4

The membrane and blood product flow were as described in Example 1. The remaining test conditions were as follows:-

  • Blood product: Anticoagulated Whole blood
  • t = 15 minutes
  • Vb = 150ml
  • A = 49cm2
  • Blood Velocity (F) = 0.9m/sec
  • Transmembrane Pressure (P) = 35mbar g

In addition the smoothness of the membrane was measured as described above. The haemolysis level and smoothness are as shown in Table 2.

Example 5

The membrane was a similar membrane to that of Example 4 but having a pore size of 0.45µm. The remaining conditions were as in Example 4. The haemolysis level and smoothness were as shown in Table 2.

Example 6

The membrane of this example was the same as the membrane of Example 2 above. The remaining test conditions were as in Example 4. The haemolysis level and smoothness were as shown in Table 2.

Example 7

The membrane of this example was the same as the membrane of Example 6 except having a pore size of 0.45µm. The remaining test conditions were as in Example 4. The haemolysis level and smoothness were as shown in Table 2.

Example 8

The membrane of this example was a hydrophilic polyvinyldifluoride membrane sold by Pall Corporation under the trade mark FLUORODYNE and having a pore size of 0.6µm. The remaining conditions were as in Example 4. The haemolysis level and smoothness were as shown in Table 2.

Example 9

The membrane was a nylon 66 membrane sold by Pall Corporation under the trade mark BIOINERT and having a pore size of 0.8µm. The remaining conditions were as in Example 4. The haemolysis level and smoothness were as shown in Table 2. EXAMPLE NO. HAEMOLYSIS SMOOTHNESS (µm) 4 - 0.2 - 0.22 5 +/- 0.2 - 0.22 6 +++ 1.0 - 1.9 7 ++++ 1.0 - 1.9 8 ++++ 0.95 - 1.45 9 +++++ 1.0 - 1.9

As seen from Table 2, the degree of haemolysis is much lower with the membranes of Examples 4 and 5 than with the membranes of Example 6 to 9. It is believed that this is due to the fact that the smoother surface of these membranes prevents lysis of erythrocytes and consequently reduces the release of haemoglobin. It will be recalled that the membrane of Example 6 is the "Control Membrane" of Example 2 and it will be seen from these Examples that, although such a membrane has a high PFR, its use causes an unaccepable lysis of erythrocytes. It will also be seen that increasing the pore size does not reduce the haemolysis but rather increases the haemolysis. It is believed that this is due to the fact that the increase in pore size provides sites where erythrocytes can enter the membrane and be damaged causing lysis and releasing haemoglobin. It has been found that, in general, membranes with pore sizes above 0.65µm cannot be used for separating plasma from a blood product because, above such a pore size, the pores are sufficiently large to permit such entry of erythrocytes. Smaller pore sizes prevent such entry.

Further tests have been conducted using the device described above with reference to Figure 1 in order specifically to confirm the effect of the smoother surface on the PFR and haemolysis.

Example 10

In this example, the membrane was a nylon 66 membrane sold by Pall Corporation under the trade mark ULTIPOR N66 and cast on Mylar in accordance with US Patent No. 4340479. The pore size was 0.45µm. The other test conditions were as in Example 4. Only one face of the membrane was cast in contact with the Mylar film; the other face was not so cast. From such a membrane, two samples were prepared. The first (SAMPLE 1) was formed by bonding two pieces of the membrane in face-to-face contact with the Mylar cast surfaces in contact. The second (SAMPLE 2) was formed by bonding two pieces of the membrane in face-to-face contact with the Mylar cast surfaces outwards. SAMPLE 1 and SAMPLE 2 were then used for separating plasma from blood product as described above with reference to Example 1 using the same conditions as in Example 1.

Figure 2 shows the traces from a Mitutoyo Surftest machine for the SAMPLE 1 and SAMPLE 2. The upper trace is of SAMPLE 2 and the lower trace is of SAMPLE 1. It will be seen that SAMPLE 2 is smoother than SAMPLE 1. The maximum measured deviation for the Mylar cast side was 0.27µm and for the non-Mylar cast side 0.47µm.

Four further samples (SAMPLES 3-6) were also prepared, SAMPLES 3 and 5 in the same way as SAMPLE 1 and SAMPLES 4 and 6 in the same way as SAMPLE 2. SAMPLES 1-6 were then tested using the device described above with reference to Figure 1 of the drawings.

Two different samples (No.1 and No.2) of anticoagulated whole blood were used. Blood sample No.1 was tested with a single sample of the membrane described above and blood sample No.2 was tested with two different samples of the membrane described.

The results are as shown in Table 3. BLOOD SAMPLE No. MEMBRANE SAMPLE No. PFR H (mg Haemoglobin/ml plasma 1 1 0.112 0.16 1 2 0.147 0.04 2 3 0.101 0.22 2 4 0.150 0.01 2 5 0.106 0.21 2 6 0.157 0.02

As shown in Table 3, all three membranes with the Mylar cast surfaces outwards had higher flow rates and lower haemolysis than the membrane with Mylar cast surfaces in contact. This tends to confirm the results set out above.

In addition, Example 10 demonstrates the contribution of smoothness to PFR. In this regard, it will be appreciated that PFR is a time averaged rate and that, as plasma is extracted from a blood product so raising the haemocrit, the instantaneous plasma flow rate drops (because there is less plasma to be extracted from the product).

This instantaneous flow rate is also affected by any blockage of the pores of the membrane. Such blockage will occur because of cell debris and other large particles being trapped in the membrane pores. It will be seen from Table 3 that, although, of course, SAMPLE 1 and SAMPLE 2 have the same water flow rate (i.e. the rate at which clean water will flow through the membrane regardless of the time of flow), the non-Mylar cast surfaces have a lower PFR than the Mylar cast surfaces.

It is believed that this is because decreasing the smoothness may provide sites where erythrocytes may lodge and subsequently lyse and where cell debris and other particles can lodge, so allowing particles to accumulate over a period of time and so causing gradual blockage of the membrane pores.

This tendency to blockage in membranes with less smooth surfaces can, if the smoothness is decreased even further (beyond 0.5µm), prevent their use for extracting plasma from a blood product on a practical scale. An acceptable level of plasma extraction is such that the haematocrit of the blood product is raised to 70% in as short a possible time. An acceptable time may be measured against the time taken to achieve similar plasma separation using a centrifruge.

To produce a haematocrit of 70% in a blood product (as typically required in the processing of blood products) a centrifuge might typically take a minimum 30 minutes and so the use of a membrane will be beneficial if such a haematocrit can be achieved in a similar or lesser time.

The smooth surface membranes (SAMPLES 2, 4 and 6) of Example 10 were able to achieve a haematocrit of 70% in less than 10 minutes.

Example 11

The following further test was conducted to confirm these conclusions. The device described above with reference to Figure 1 was used with the membrane of Example 1 to filter 150ml of fresh whole blood anticoagulated with CPDA under the conditions of blood velocity and transmembrane pressure of Example 1. The PFR, haematocrit of the blood and the haemolysis (in mg haemoglobin per 100 ml of plasma) were measured at 2 minute intervals for a period of 20 minutes. The test was repeated 10 times and for each parameter the mean and ±1 standard deviations were calculated for each time interval.

The results are shown in Figure 3 (which plots PFR and haematocrit against time) and Figure 4 (which plots the haemoglobin in the filtered plasma against time).

It will be seen from Figure 3, that, in the exemplified embodiment of the invention, the PFR is closely dependent on the haematocrit of the blood product. As the haematocrit rises (i.e. as the concentration of red cells rises) the plasma flux decreases proportionately. This indicates that the drop in PFR with time is mainly due to plasma extraction and red cell concentration and not to fouling of the membrane or other factors causing a deterioration in membrane performance.

Figure 4 shows that haemolysis does not begin to increase significantly until 12 minutes have elapsed. With reference to Figure 3, it will be seen that after 12 minutes a haematocrit of more than 70% has been reached and, as discussed above, a haematocrit of 70% is generally regarded as an acceptable level.

Although the haemoloysis increases significantly after 12 minutes, it is believed that this is due not to the membrane but to the fact that the shear forces to which the erythrocytes are subjected increase as the viscosity of the blood increases as plasma is removed and the haematocrit rises. In addition, after 12 minutes, the blood has been in contact with the surfaces of the device for a considerable time which also tends to increase lysis as does the action of the pump in pumping the red cells at high haematocrits.

It is considered that membrane materials embodying the invention and as described above are less likely to activate platelets.

While the membranes described above have been tested using exemplified cross-flow filtration devices, it will be appreciated that they may be used with any suitable device, which may not be a cross-flow device.


Anspruch[de]
  1. Querstromvorrichtung zur Behandlung eines Blutproduktes, welches rote Blutkörperchen suspendiert in einem Fluid enthält, um das Fluid von den Blutkörperchen abzutrennen, wobei die Vorrichtung eine Anordnung (11) mit einem Einlaß (24) für das Blutprodukt und einem Auslaß (25) für fluidarme Blutkörperchen umfaßt, wobei eine Membran (40) sich über die Anordnung (11) gegen eine Seite des Blutprodukteinlasses (24) und des Auslasses (25) für fluidarme Blutkörperchen erstreckt, wobei die Membran erste und zweite voneinander beabstandete Oberflächen aufweist, welche durch eine poröse Struktur getrennt sind, wobei die erste Oberfläche zum Inneren der Anordnung weist und mit Blutprodukt in Kontakt steht, welches zwischen dem Blutprodukteinlaß (24) und dem Auslaß (25) für fluidarme Blutkörperchen fließt, wobei die Membran (40) ein Hohlraumvolumen von mindestens 50% aufweist und die erste Oberfläche eine Glätte aufweist, welche 0,5 µm beträgt, gemessen mittels eines "Mitutoyo Surftest 401 tally surf"-Gerätes als eine mittlere Abweichung der Position eines Taststiftes des Gerätes in einer Richtung senkrecht zu dieser Oberfläche von einer mittleren Position des Taststiftes, wenn der Taststift über die Oberfläche gezogen wird, wobei ein Auslaß (15) für das abgetrennte Fluid vorgesehen ist, wobei dieser Auslaß (15) zur zweiten Membranoberfläche hinweist.
  2. Vorrichtung nach Anspruch 1, worin das Hohlraumvolumen mindestens 70% beträgt.
  3. Vorrichtung nach Anspruch 1 oder 2, worin die Membran (40) eine Porengröße von weniger als 0,65 µm aufweist.
  4. Vorrichtung nach einem der Ansprüche 1 bis 3, worin das Volumen an Fluid, das während 15 Minuten abgetrennt wird, größer ist als 0,6 ml pro Einheitsfläche in cm2 der ersten Oberfläche, wenn die Vorrichtung Verwendet wird, um ein Volumen entsprechend 3,75 ml pro Einheitsfläche in cm2 der ersten Oberfläche an roten Blutkörperchenzu behandeln, suspendiert in einer wäßrigen Lösung von 140 mmol/l Natriumchlorid, 1,5 mmol Adenin, 50 mmol/l Glukose und 30 mmol/l Mannit bei einem Haematokrit von 45% und einer Druckdifferenz über die Membran von 35 mbar.
  5. Querstromvorrichtung zur Behandlung eines Blutproduktes, welches rote Blutkörperchen in einem Fluid suspendiert umfaßt, wobei zum Abtrennen des Fluids von den Blutkörperchen die Vorrichtung ein Gehäuse (10, 11, 12) mit einem Einlaß (24) für das Blutprodukt, einen Auslaß (25) für fluidarme Blutkörperchen, einen Auslaß (15) für das Fluid und eine Membran (40) umfaßt, welche in dem Gehäuse angeordnet ist, wobei die Membran (40) erste und zweite voneinander beabstandete Oberflächen aufweist, welche durch eine poröse Struktur getrennt sind, wobei die erste Oberfläche zum Innern des Gehäuses (10, 11, 12) weist und in Kontakt steht mit einem Blutprodukt, welches zwischen dem Blutprodukteinlaß (24) und dem Auslaß (25) für fluidarme Blutkörperchen fließt, wobei der Fluidauslaß (15) der zweiten Membranoberfläche gegenüberliegt, wobei die Membran (40) eine Porengröße von weniger als 0,65 µm aufweist, und worin das Volumen an Fluid, das während 15 Minuten abgetrennt wird, größer als 0,6 ml pro Einheitsfläche in cm2 der ersten Oberfläche beträgt, wenn die Vorrichtung verwendet wird, um ein Volumen entsprechend 3,75 ml pro Einheitsfläche in cm2 der ersten Oberfläche an roten Blutkörperchen, suspendiert in einer wäßrigen Lösung von 140 mmol/l Natriumchlorid, 1,5 mmol/l Adenin, 50 mmol/l Glukose und 30 mmol/l Mannit bei einem Haematokrit von 45% und bei einer Druckdifferenz über die Membran von 35 mbar, wobei die erste Oberfläche eine Glattheit aufweist, bei der ein Wert von weniger als 0,5 µm mit einem "Mitutoyo Surftest 401 tally surf"-Gerät als mittlere Abweichung der Position des Taststiftes des Gerätes in einer Richtung senkrecht zu der Oberfläche von einer mittleren Position des Taststiftes gemessen wird, wenn der Taststift über die Oberfläche gezogen wird.
  6. Vorrichtung nach Anspruch 4 oder 5, worin das Volumen an Fluid, welches pro Einheitsfläche in cm2 der ersten Oberfläche in 15 Minuten abgetrennt wird, größer als 1,2 ml ist, bevorzugt größer als 1,5 ml und am meisten bevorzugt größer als 2,25 ml, wenn die Vorrichtung Verwendet wird, um ein Volumen entsprechend 3,75 ml pro Einheitsfläche in cm2 der ersten Oberfläche an roten Blutzellen zu behandeln, suspendiert in einer wäßrigen Lösung von 140 mmol/l Natriumchlorid, 1,5 mmol/l Adenin, 50 mmol/l Glukose und 30 mmol/l Mannit bei einem Haematokrit von 45%, und wenn der Druckunterschied über die Membran 35 mbar beträgt.
  7. Vorrichtung nach einem der Ansprüche 1 bis 6, worin die Porengröße kleiner als 0,5 µm beträgt.
  8. Vorrichtung nach einem der Ansprüche 1 bis 7, worin die Glattheit der ersten Membranoberfläche geringer als 0,3 µm ist.
  9. Vorrichtung nach einem der Ansprüche 1 bis 8, worin die Membran (40) ein hautloses, alkoholunlösliches hydrophiles Polyamidharz ist.
  10. Vorrichtung nach Anspruch 9, worin das Polyamid Nylon 66 ist, wobei die erste Membranoberfläche auf einem Mylar-Substrat gegossen wird.
  11. Vorrichtung nach einem der voranstehenden Ansprüche und umfassend ein Fluidauslaßteil (10) mit einer flachen oberen Oberfläche (14), auf welches die zweite Oberfläche der Membran (40) aufliegt, wobei der Fluidauslaß (15) durch die obere Oberfläche (14) führt, und Mittel (12) zum Bilden eines Durchgangs für das Blutprodukt von dem Einlaß (24) zu dem Auslaß (25) für fluidarme Blutkörperchen quer zur ersten Oberfläche der Membran (40).
  12. Vorrichtung nach Anspruch 11, worin eine Wandung (17) die Oberfläche (14) des Fluidauslaßteils (10) umrundet, wobei die Anordnung (11) einen ringförmigen Flansch (22) umfaßt, welcher in die Wandung (17) paßt und durch welchen der Blutprodukteinlaß (24) und der Auslaß (25) für fluidarme Blutkörperchen hindurchführen, um zur Membran (40) hin zu öffnen.
  13. Vorrichtung nach Anspruch 11 oder 12, worin der Durchlaß Mittel umfaßt, welche einen Einsatz (12) mit einer Oberfläche, welche von der ersten Oberfläche der Membran (40) beabstandet ist, aufweist, wobei der Einsatz (12) von der Anordnung (11) getragen wird.
  14. Vorrichtung nach Anspruch 13, worin die Beabstandung einstellbar ist.
  15. Vorrichtung nach Anspruch 12 oder 13, worin die Wandung (17) ringförmig ist, worin die Anordnung (11) ringförmig ist und die Einlaßoberfläche kreisförmig ist.
  16. Vorrichtung nach Anspruch 15, worin das Fluidauslaßteil (10)einen ringförmigen Falz (18) umfaßt, worin die Anordnung (11) einen ringförmigen Körper (19) umfaßt, welcher von dem Falz (18) aufgenommen wird, wobei der ringförmige Flansch(22) hiervon nach unten absteht.
  17. Vorrichtung nach Anspruch 16, worin die Anordnung (17) eine ringförmige mittige Bohrung aufweist, wobei der Einsatz (12) von der Bohrung aufgenommen wird.
  18. Vorrichtung nach Anspruch 17, worin eine Dichtung (21) zwischen dem Falz (18) und der Anordnung (11) vorgesehen ist, und eine Dichtung (33) zwischen der Bohrung und dem Einsatz (12) vorgesehen ist.
  19. Vorrichtung nach einem der Ansprüche 1 bis 17, worin die Membran aus zwei Lagen einer Nylon-66-Membran mit einer Porengröße von 0,45 µm zusammengesetzt ist, wobei jede Lage auf einem Mylar-Substrat gegossen und dann von dem Mylar-Substrat entfernt wurde, wobei die beiden Lagen miteinander in einer Stirn-Stirn-Anordnung verbunden sind, wobei die auf Mylar gegossenen Seiten nach außen liegen, um die erste und die zweite Oberfläche zu bilden.
  20. Verfahren zur Behandlung eines Blutproduktes, welches rote Blutkörperchen, suspendiert in einem Fluid umfaßt, um dabei Fluid von den Blutkörperchen abzutrennen, umfassend das Strömen des Blutproduktes über eine erste Oberfläche einer Lage eines Membranmaterials (40), welches eine erste und eine zweite Oberfläche aufweist, welche voneinander durch eine poröse Struktur getrennt sind, Filtern des Blutproduktes durch die poröse Struktur der Lage an Membranmaterial (40), wobei die Membran ein Hohlraumvolumen von mindestens 50% aufweist und wobei die erste Oberfläche eine Glattheit aufweist, welche als 0,5 µm gemessen wird mit einem "Mitutoyo Surftest 401 tally surf"-Gerät als die mittlere Abweichung in eine Richtung senkrecht zur Oberfläche der Position des Taststiftes dieses Gerätes von einer mittleren Position des Taststiftes, wenn der Taststift über die Oberfläche gezogen wird.
  21. Verfahren nach Anspruch 20, worin das Hohlraumvolumen mindestens 70% beträgt.
  22. Verfahren nach Anspruch 20 oder 21, worin die Membran (40) eine Porengröße kleiner als 0,65 µm aufweist.
  23. Verfahren nach einem der Ansprüche 20 bis 22, worin das Volumen an wahrend 15 Minuten abgetrenntem Fluid größer als 0,6 ml pro Einheitsfläche in cm2 der ersten Oberfläche beträgt, wenn ein Volumen an Blutprodukt entsprechend 3,75 ml pro Einheitsfläche in cm2 der ersten Oberfläche der ersten Oberfläche behandelt wird und wenn die Druckdifferenz über die Membran 35 mbar beträgt.
  24. Verfahren zur Behandlung eines Blutproduktes, welches rote Blutkörperchen, suspendiert in einem Fluid enthält, zum Abtrennen des Fluids von den Blutkörperchen, umfassend das Strömen des Blutproduktes über eine erste Oberfläche einer Lage eines Membranmaterials (40), welches beabstandete erste und zweite Oberflächen aufweist, welche von einer porösen Struktur voneinander getrennt sind, wobei die Membran (40) eine Porengröße von weniger als 0,65 µm aufweist und die erste Oberfläche der Lage an Membranmaterial (40) eine Glattheit aufweist, die geringer ist als 0,5 µm, gemessen mit einem "Mitutoyo Surftest 401 tally surf"-Gerät als die mittlere Abweichung der Position des Taststiftes des Gerätes in einer Richtung senkrecht zur Oberfläche von einer mittleren Position des Taststiftes, wenn der Taststift über die Oberfläche gezogen wird, und worin das Volumen an Fluid, welches während 15 Minuten abgetrennt wird, größer ist als 0,6 ml pro Einheitsfläche in cm2 der ersten Oberfläche, wenn ein Volumen an Blutprodukt entsprechend 3,75 ml pro pro Einheitsfläche in cm2 der ersten Oberfläche behandelt wird, und wenn die Druckdifferenz über die Membran 35 mbar beträgt.
  25. Verfahren nach Anspruch 23 oder 24, worin das Volumen an Fluid, welches pro Einheitsfläche in cm2 der ersten Oberfläche in 15 Minuten abgetrennt wird, größer als 1,2 ml, bevorzugt größer als 1,5 ml und am meisten bevorzugt größer als 2,25 ml beträgt, wenn ein Volumen an Blutprodukt entsprechend 3,75 ml pro Einheitsfläche in cm2 der ersten Oberfläche behandelt wird, und wenn der Druckunterschied über die Membran 35 mbar beträgt.
  26. Verfahren nach einem der Ansprüche 20 bis 25, worin die Porengröße kleiner als 0,5 µm ist.
  27. Verfahren nach einem der Ansprüche 20 bis 26, worin die Glattheit der ersten Oberfläche der Membran (40) geringer als 0,3 µm ist.
  28. Verfahren nach einem der Ansprüche 20 bis 27, worin die Membran (40) eine hautlose, alkoholunlösliche hydrophile Polyamidmembran ist.
  29. Verfahren nach Anspruch 28, worin das Polyamid Nylon-66 ist, wobei die Membranoberfläche auf ein Mylar-Substrat gegossen wird.
  30. Verfahren nach einem der Ansprüche 20 bis 29, worin das Blutprodukt rote Blutkörperchen sind, welche suspendiert sind in einer wäßrigen Lösung von 140 mmol/l Natriumchlorid, 1,5 mmol/l Adenin, 50 mmol/l Glukose und 30 mmol/l Mannit.
  31. Verfahren nach Anspruch 30, worin der Haematokrit der roten Blutkörperchen in dem Blutprodukt größer als 30% ist.
  32. Verfahren nach einem der Ansprüche 20 bis 29, worin das Blutprodukt ein antikoaguliertes frisches Vollblut ist.
  33. Verfahren nach einem der Ansprüche 20 bis 24 oder jedem hiervon abhängigen Anspruch und umfassend das Fließen des Blutprodukts über die Membran (40) bis ein Haematokrit Von 70% erreicht ist.
  34. Verfahren nach einem der Ansprüche 20 bis 33, worin die Membran (40) aus zwei Lagen einer Nylon-66-Membran mit einer Porengröße von 0,45 µm zusammengesetzt ist, wobei jede Lage auf einem Mylar-Substrat gegossen und dann von dem Mylar-Substrat entfernt wurde, wobei die beiden Lagen in einer Stirn-zu-Stirn-Kontaktanordnung miteinander verbunden sind, wobei die auf Mylar gegossenen Seiten nach außen weisen, um die erste und zweite Oberfläche zu bilden.
Anspruch[en]
  1. A cross-flow device for treating a blood product comprising red blood cells suspended in a fluid to separate the fluid from the cells, the device including a manifold (11) having an inlet (24) for the blood product and an outlet (25) for fluid depleted cells, a membrane (40) extending across the manifold (11) to one side of the blood product inlet (24) and the depleted-cell outlet (25), the membrane having first and second spaced surfaces separated by a porous structure with the first surface facing into the manifold and contacted by blood product flowing between the blood product inlet (24) and the depleted cell outlet (25), the membrane (40) having a voids volume of at least 50% and the first surface having a smoothness of less than 0.5µm as measured by a Mitutoyo Surftest 401 tally surf machine as the average deviation in directions normal to said surface of the position of the stylus of said machine from a mean position of the stylus as the stylus is drawn across said surface, an outlet (15) being provided for separated fluid, said outlet (15) facing said second membrane surface.
  2. A device according to claim 1 wherein the voids volume is at least 70%.
  3. A device according to claim 1 or claim 2 wherein the membrane (40) has a pore size of less than 0.65µm.
  4. A device according to any one of claims 1 to 3, wherein the volume of fluid separated over 15 minutes is greater than 0.6 ml per unit area in cm2 of the said first surface when the device is used to treat a volume corresponding to 3.75 ml per unit area in cm2 of the said first surface of red blood cells suspended in an aqueous solution of 140 mmol/l sodium chloride, 1.5 mmol adenine, 50 mmol/l glucose and 30 mmol/l mannitol at a haematocrit of 45%, and when the transmembrane pressure difference is 35 mbar.
  5. A cross-flow device for treating a blood product comprising red blood cells suspended in a fluid whereby to separate the fluid from the cells, the device comprising a housing (10,11,12) having an inlet (24) for the blood product, an outlet (25) for fluid depleted cells, an outlet (15) for fluid and a membrane (40) disposed in the housing, the membrane (40) having first and second spaced surfaces separated by a porous structure with the first surface facing into the housing (10,11,12) and contacted by blood product flowing between the blood product inlet (24) and the depleted cell outlet (25), the fluid outlet (15) facing said second membrane surface, the membrane (40) having a pore size of less than 0.65 µm, and wherein the volume of fluid separated over 15 minutes is greater than 0.6 ml per unit area in cm2 of the said first surface when the device is used to treat a volume corresponding to 3.75 ml per unit area in cm2 of the said first surface of red blood cells suspended in an aqueous solution of 140 mmol/l sodium chloride, 1.5 mmol/l adenine, 50 mmol/l glucose and 30 mmol/&litre; mannitol at a haematocrit of 45%, and when the transmembrane pressure difference is 35 mbar, the first membrane surface having a smoothness of less than 0.5 µm as measured by a Mitutoyo Surftest 401 tally surf machine as the average deviation in directions normal to said surface of the position of the stylus of said machine from a mean position of the stylus as the stylus is drawn across said surface.
  6. A device according to claim 4 or claim 5 wherein the volume of fluid separated per unit area in cm2 of the said first surface in 15 minutes is greater than 1.2 ml, preferably greater than 1.5 ml and more preferably greater than 2.25 ml when the device is used to treat a volume corresponding to 3.75 ml per unit area in cm2 of the said first surface of red blood cells suspended in an aqueous solution of 140 mmol/l sodium chloride, 1.5 mmol/l adenine, 50 mmol/l glucose and 30 mmol/l mannitol at a haematocrit of 45%, and when the transmembrane pressure difference is 35 mbar.
  7. A device according to any one of claims 1 to 6 wherein the pore size is less than 0.5µm.
  8. A device according to any one of claims 1 to 7 wherein the said smoothness of the said first membrane surface is less than 0.3µm.
  9. A device according to any one of claims 1 to 8 wherein the membrane (40) is a skinless alcohol-insoluble hydrophilic polyamide resin.
  10. A device according to claim 9 wherein the polyamide is nylon 66, said first membrane surface being cast on a Mylar substrate.
  11. A device according to any preceding claim and comprising a fluid outlet member (10) having a flat upper surface (14) on which the second surface of the membrane (40) rests, the fluid outlet (15) leading through said upper surface (14), and means (12) defining a passage for the blood product from said inlet (24) to the fluid depleted cell outlet (25) across the first surface of the membrane (40).
  12. A device according to claim 11 wherein a wall (17) surrounds said surface (14) of the fluid outlet member (10), the manifold (11) comprising an annular flange (22) which fits within said wall (17) and through which the blood product inlet (24) and the fluid depleted cell outlet (25) pass to open onto the membrane (40).
  13. A device according to claim 11 or claim 12 wherein the passage defining means comprises an insert (12) having a surface spaced from the first surface of the membrane (40), the insert (12) being carried by the manifold (11).
  14. A device according to claim 13 wherein said spacing is adjustable.
  15. A device according to claim 12 and claim 13 wherein the wall (17) is annular, the manifold (11) being annular and the insert surface being circular.
  16. A device according to claim 15 wherein the fluid outlet member (10) includes an annular rebate (18), the manifold (11) including an annular body (19) received in said rebate (18) with said annular flange (22) depending therefrom.
  17. A device according to claim 16 wherein the manifold (17) has an annular central bore, the insert (12) being received in said bore.
  18. A device according to claim 17 wherein a seal (21) is provided between the rebate (18) and the manifold (11) and a seal (33) is provided between the bore and the insert (12).
  19. A device according to any one of claims 1 to 17 wherein the membrane is composed of two sheets of 0.45µm pore size nylon 66 membrane, each sheet having been cast on a Mylar substrate and then removed from said Mylar substrate, the two sheets being bonded together in face-to-face contact with the Mylar cast sides outward to form said first and second surfaces.
  20. A method of treating a blood product comprising red blood cells suspended in a fluid whereby to separate the fluid from the cells comprising flowing the blood product across a first surface of a sheet of membrane material (40) having spaced first and second surfaces separated by a porous structure, filtering the blood product through the porous structure of the sheet of membrane material (40), the membrane having a voids volume of at least 50% and the first surface having a smoothness of less than 0.5µm as measured by a Mitutoyo Surftest 401 tally surf machine as the average deviation in directions normal to said surface of the position of the stylus of said machine from a mean position of the stylus as the stylus is drawn across said surface.
  21. A method according to claim 20 wherein the voids volume is at least 70%.
  22. A method according to claim 20 or claim 21 wherein the membrane (40) has a pore size of less than 0.65µm.
  23. A method according to any one of claims 20 to 22 wherein the volume of fluid separated over 15 minutes is greater than 0.6 ml per unit area in cm2 of the said first surface when a volume of blood product corresponding to 3.75 ml per unit area in cm2 of the said first surface is being treated, and when the transmembrane pressure difference is 35 mbar.
  24. A method of treating a blood product comprising red blood cells suspended in a fluid whereby to separate the fluid from the cells comprising flowing the blood product across a first surface of a sheet of membrane material (40) having spaced first and second surfaces separated by a porous structure, the membrane (40) having a pore size of less than 0.65µm and the first surface of the sheet of membrane material (40) having a smoothness of less than 0.5µm as measured by a Mitutoyo Surftest 401 tally surf machine as the average deviation in directions normal to said surface of the position of the stylus of said machine from a mean position of the stylus as the stylus is drawn across said surface, and wherein the volume of fluid separated over 15 minutes is greater than 0.6 ml per unit area in cm2 of the said first surface when a volume of blood product corresponding to 3.75 ml per unit area in cm2 of the said first surface is being treated, and when the transmembrane pressure difference is 35 mbar.
  25. A method according to claim 23 or claim 24 wherein the volume of fluid separated per unit area in cm2 of the said first surface in 15 minutes is greater than 1.2 ml preferably greater than 1.5 ml and more preferably greater than 2.25 ml when a volume of blood product corresponding to 3.75 ml per unit area in cm2 of the said first surface is being treated, and when the transmembrane pressure difference is 35 mbar.
  26. A method according to any one of claims 20 to 25 wherein the pore size is less than 0.5µm.
  27. A method according to any one of claims 20 to 26 wherein the said smoothness of the first membrane (40) surface is less than 0.3µm.
  28. A method according to any one of claims 20 to 27 wherein the membrane (40) is a skinless alcohol insoluble hydrophilic polyamide membrane.
  29. A method according to claim 28 wherein the polyamide is nylon 66, said membrane surface being cast on a Mylar substrate.
  30. A method according to any one of claims 20 to 29 wherein the blood product is red blood cells suspended in an aqueous solution of 140 mmol/l sodium chloride, 1.5 mmol/l adenine, 50 mmol/l glucose and 30 mmol/l mannitol.
  31. A method according to claim 30 wherein the haematocrit of the red blood cells in the blood product is greater than 30%.
  32. A method according to any one of claims 20 to 29 wherein the blood product is anticoagulated fresh whole blood.
  33. A method according to any one of claims 20 to 24 or any claim dependent thereon and comprising flowing said blood product across the membrane (40) until a haematocrit of 70% is reached.
  34. A method according to any one of claims 20 to 33 wherein the membrane (40) is composed of two sheets of 0.45µm pore size nylon 66 membrane, each sheet having been cast on a Mylar substrate and then removed from said Mylar substrate, the two sheets being bonded together in face-to-face contact with the Mylar cast sides outward to form said first and second surfaces.
Anspruch[fr]
  1. Dispositif à courant transversal pour traiter un produit sanguin contenant des globules rouges du sang suspendus dans un fluide, pour séparer le fluide d'avec les globules, le dispositif comportant un manifold (11) présentant une entrée (24) pour le produit sanguin et une sortie (25) pour des globules appauvris en fluide, une membrane (40) s'étendant à travers le manifold (11) jusqu'à un côté de l'entrée (24) du produit sanguin et jusqu'à la sortie (25) des globules appauvris, la membrane présentant une première et une seconde surfaces espacées l'une de l'autre, séparées par une structure poreuse, la première surface faisant face dans le manifold et étant en contact avec le produit sanguin qui s'écoute entre l'entrée (24) du produit sanguin et la sortie (25) des globules appauvris, la membrane (40) présentant un volume de vide d'au moins 50% et la première surface présentant un lissé inférieur à 0,5 µm, mesuré par une machine de pointage en surface Mitutoyo Surftest 401 comme écart moyen, selon les directions normales à ladite surface, entre la position du stylet de ladite machine et une position moyenne du stylet lorsque le stylet parcourt ladite surface, une sortie (15) étant prévue pour le fluide séparé, ladite sortie (15) faisant face à ladite seconde surface de la membrane.
  2. Dispositif selon la revendication 1, dans lequel le volume de vide est d'au moins 70%.
  3. Dispositif selon la revendication 1 ou la revendication 2, dans lequel la membrane (40) a une dimension de pore inférieure à 0,65 µm.
  4. Dispositif selon l'une quelconque des revendications 1 à 3, dans lequel le volume de fluide séparé en 15 minutes est supérieur à 0,6 ml par unité de surface en cm2 de ladite première surface lorsque le dispositif sert à traiter un volume, correspondant à 3,75 ml par unité de surface en cm2 de ladite première surface, de globules rouges du sang suspendus dans une solution aqueuse de 140 mmol/l de chlorure de sodium, 1,5 mmol d'adénine, 50 mmol/l de glucose et 30 mmol/l de mannitol pour un hématocrite de 45% et lorsque la différence de pression de part et d'autre de la membrane est 35 mbars.
  5. Dispositif à courant transversal pour traiter un produit sanguin contenant des globules rouges du sang suspendus dans un fluide de façon à séparer le fluide d'avec les globules, le dispositif comportant un boîtier (10,11,12) présentant une entrée (24) pour le produit sanguin, une sortie (25) pour des globules appauvris en fluide, une sortie (15) pour le fluide et une membrane (40) disposée dans le boîtier, la membrane (40) présentant une première et une seconde surfaces espacées l'une de l'autre, séparées par une structure poreuse, la première surface faisant face dans le boîtier (10,11,12) et étant en contact avec du produit sanguin qui s'écoule entre l'entrée (24) du produit sanguin et la sortie (25) des globules appauvris, la sortie (15) du fluide faisant face à ladite seconde surface de la membrane, la membrane (40) présentant une dimension de pore inférieure à 0,65 µm, et dans lequel le volume de fluide séparé en 15 minutes est supérieur à 0,6 ml par unité de surface en cm2 de ladite première surface lorsque le dispositif sert à traiter un volume, correspondant à 3,75 ml par unité de surface en cm2 de ladite première surface, de globules rouges du sang suspendus dans une solution aqueuse de 140 mmol/l de chlorure de sodium, 1,5 mmol d'adénine, 50 mmol/l de glucose et 30 mmol/l de mannitol pour un hématocrite de 45% et lorsque la différence de pression de part et d'autre de la membrane est 35 mbars, la première surface de la membrane présentant un lissé inférieur à 05 µm, mesuré par une machine de pointage en surface Mitutoyo Surftest 401 comme écart moyen, selon les directions normales à ladite surface, entre la position du stylet de ladite machine et une position moyenne du stylet lorsque le stylet parcourt ladite surface.
  6. Dispositif selon la revendication 4 ou la revendication 5, dans lequel le volume de fluide séparé par unité de surface en cm2 de ladite première surface en 15 minutes est supérieur à 1,2 ml, de préférence supérieur à 1,5 ml et de plus grande préférence supérieur à 2,25 ml lorsque le dispositif sert à traiter un volume, correspondant à 3,75 ml par unité de surface en cm2 de ladite première surface, de globules rouges du sang suspendus dans une solution aqueuse de 140 mmol/l de chlorure de sodium, 1,5 mmol d'adénine, 50 mmol/l de glucose et 30 mmol/l de mannitol pour un hématocrite de 45% et lorsque la différence de pression de part et d'autre de la membrane est 35 mbars.
  7. Dispositif selon l'une quelconque des revendications 1 à 6, dans lequel la dimension de pore est inférieure à 0,5 µm.
  8. Dispositif selon l'une quelconque des revendications 1 à 7, dans lequel ledit lissé de ladite première surface de la membrane est inférieur à 0,3 µm.
  9. Dispositif selon l'une quelconque des revendications 1 à 8, dans le cas de la membrane (40) est une résine polyamide hydrophile, insoluble dans l'alcool, sans peau.
  10. Dispositif selon la revendication 9, dans lequel le polyamide est du nylon 66, ladite première surface de la membrane étant coulée sur un substrat de Mylar.
  11. Dispositif selon l'une quelconque des revendications précédentes et comportant un élément (10) de sortie du fluide présentant une surface supérieure plate (14) sur laquelle repose la seconde surface de la membrane (40), la sortie (15) du fluide passant à travers ladite surface supérieure (14), ainsi que des moyens (12) définissant un passage pour le produit sanguin, depuis ladite entrée (24) jusqu'à la sortie (25) des globules appauvris en fluide, d'un côté à l'autre de la première surface de la membrane (40).
  12. Dispositif selon la revendication 11, dans lequel une paroi (17) entoure ladite surface (14) de l'élément (10) de sortie du fluide, le manifold (11) comportant une saillie annulaire (22) qui s'ajuste dans ladite paroi (17) et par laquelle passent l'entrée (24) du produit sanguin et la sortie (25) des globules appauvris en fluide pour s'ouvrir sur la membrane (40).
  13. Dispositif selon la revendication 11 ou la revendication 12, dans lequel les moyens définissant un passage comportent une garniture insérée (12) présentant une surface espacée de la première surface de la membrane (40), la garniture insérée (12) étant portée par le manifold (11).
  14. Dispositif selon la revendication 13, dans lequel ledit espacement est réglable.
  15. Dispositif selon la revendication 12 ou la revendication 13, dans lequel la paroi (17) est annulaire, le manifold (11) étant annulaire et la surface de la garniture insérée étant circulaire.
  16. Dispositif selon la revendication 15, dans lequel l'élément (10) de sortie du fluide inclut un collet annulaire (18), le manifold (11) incluant un corps annulaire (19) reçu dans ledit collet (18), ladite saillie annulaire (22) y pendant.
  17. Dispositif selon la revendication 16, dans lequel le manifold (17) a un alésage central annulaire, la garniture insérée (12) étant reçue dans ledit alésage.
  18. Dispositif selon la revendication 17, dans lequel une garniture d'étanchéité (21) est prévue entre le collet (18) et le manifold (11) et une garniture d'étanchéité (33) est prévue entre l'alésage et la garniture insérée (12).
  19. Dispositif selon l'une quelconque des revendication 1 à 17, dans lequel la membrane est composée de deux feuilles de membrane de nylon 66 de dimension de pore de 0,45 µm, chaque feuille ayant été coulée sur un substrat de Mylar puis détachée dudit substrat de Mylar, les deux feuilles étant liées ensemble en contact face à face, faces coulées sur le Mylar à l'extérieur, pour former ladite première et ladite seconde surfaces.
  20. Procédé de traitement d'un produit sanguin comportant des globules rouges du sang suspendus dans un fluide de façon à séparer le fluide d'avec les globules, consistant à faire s'écouler le produit sanguin à travers une première surface d'une feuille d'un matériau en membrane (40) présentant une première et une seconde surfaces, espacées l'une de l'autre, séparées par une structure poreuse, à filtrer le produit sanguin à travers la structure poreuse de la feuille du matériau en membrane, la membrane présentant un volume de vide d'au moins 50% et la première surface présentant un lissé inférieur à 0,5 µm, mesuré par une machine de pointage en surface Mitutoyo Surftest 401 comme écart moyen, selon les directions normales à ladite surface, entre la position du stylet de ladite machine et une position moyenne du stylet lorsque le stylet parcourt ladite surface.
  21. Procédé selon la revendication 20 dans lequel le volume de vide est d'au moins 70%.
  22. Procédé selon la revendication 20 ou la revendication 21 dans lequel la membrane (40) présente une dimension de pore inférieure à 0,65 µm.
  23. Procédé selon l'une quelconque des revendications 20 à 22, dans lequel le volume de fluide séparé en 15 minutes est supérieur à 0,6 ml par unité de surface en cm2 de ladite première surface lorsque l'on y traite un volume de produit sanguin correspondant à 3,75 ml par unité de surface en cm2 de ladite première surface et que la différence de pression de part et d'autre de la membrane est 35 mbars.
  24. Procédé de traitement d'un produit sanguin comportant des globules rouges du sang suspendus dans un fluide de façon à séparer le fluide d'avec les globules, consistant à faire s'écouler le produit sanguin à travers une première surface d'une feuille d'un matériau en membrane (40) présentant une première et une seconde surfaces, espacées l'une de l'autre, séparées par une structure poreuse, la membrane (40) présentant une dimension de pore inférieure à 0,65 µm et la première surface de la feuille de matériau en membrane (40) présentant un lissé inférieur à 0,5µm, mesuré par une machine de pointage en surface Mitutoyo Surftest 401 comme écart moyen, selon les directions normales à ladite surface, entre la position du stylet de ladite machine et une position moyenne du stylet lorsque le stylet parcourt ladite surface, et dans lequel le volume de fluide séparé en 15 minutes est supérieur à 0,6 ml par unité de surface en cm2 de ladite première surface lorsque l'on y traite un volume de produit sanguin correspondant à 3,75 ml par unité de surface en cm2 de ladite première surface et que la différence de pression de part et d'autre de la membrane est 35 mbars.
  25. Procédé selon la revendication 23 ou la revendication 24, dans lequel le volume de fluide séparé par unité de surface en cm2 de ladite première surface en 15 minutes est supérieur à 1,2 ml, de préférence supérieur à 1,5 ml et de plus grande préférence supérieur à 2,25 ml lorsque l'on traite un volume de produit sanguin correspondant à 3,75 ml par unité de surface en cm2 de ladite première surface et que la différence de pression de part et d'autre de la membrane est 35 mbars.
  26. Procédé selon l'une quelconque des revendications 20 à 25, dans lequel la dimension de pore est inférieure à 0,5 µm.
  27. Procédé selon l'une quelconque des revendications 20 à 26, dans lequel ledit lissé de la première surface de la membrane (40) est inférieur à 0,3 µm.
  28. Procédé selon l'une quelconque des revendications 20 à 27, dans lequel la membrane (40) est une membrane polyamide hydrophile insoluble dans l'alcool, sans peau.
  29. Procédé selon la revendication 28, dans lequel le polyamide est du nylon 66, ladite surface de membrane étant coulée sur un substrat de Mylar.
  30. Procédé selon l'une quelconque des revendications 20 à 29, dans lequel le produit sanguin est des globules rouges du sang suspendus dans une solution aqueuse de 140 mmol/l de chlorure de sodium, 1,5 mmol/l d'adénine, 50 mmol/l de glucose et 30 mmol/l de mannitol.
  31. Procédé selon la revendication 30, dans lequel l'hématocrite des globules rouges du sang d'un produit sanguin est supérieur à 30%.
  32. Procédé selon l'une quelconque des revendications 20 à 29, dans lequel le produit sanguin est un sang complet frais traité par un anticoagulant.
  33. Procédé selon l'une quelconque des revendications 20 à 24 ou l'une quelconque des revendications qui en dépendent et consistant à faire s'écouler ledit produit sanguin à travers la membrane (40) jusqu'à atteindre un hématocrite de 70%.
  34. Procédé selon l'une quelconque des revendications 20 à 33 dans lequel la membrane (40) est composée de deux feuilles de membrane de nylon 66 de dimension de pore de 0,45 µm, chaque feuille ayant été coulée sur un substrat de Mylar puis détachée dudit substrat de Mylar, les deux feuilles étant liées ensemble en contact face à face, faces coulées sur le Mylar à l'extérieur, pour former ladite première et ladite seconde surfaces.






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