NL1017570C2 - Blood treatment device. - Google Patents

Description

BLOOD TREATMENT

When performing some medical operations, such as open heart surgery, it is necessary to temporarily take over the lung function by means of equipment. Oxygenators have been developed for this purpose. These devices are capable of taking carbon dioxide from the blood and adding oxygen to the blood.

The already existing oxygenators, however, have a number of disadvantages. The operating volume (priming volume) of the blood needed to work with an oxygenator is very large in the existing devices. In the case of humans, 10% of an adult's blood volume is required for the operating volume. Another drawback is that the ratio between the operating volume and the effective contact surface that can be used for the transfer of oxygen and carbon dioxide is small. To overcome the above-mentioned drawbacks, the present invention provides a blood treatment device comprising: a first plate provided with a number of first channels in a first direction for transporting blood therein; - a second plate near the first plate provided with a number of second channels which have a second direction for transporting gases therein; - a gas-permeable membrane arranged between the first and second channels.

An advantage of the present invention is a relatively large ratio between the operating volume and the contact surface. Furthermore, by keeping the plates and the channels very small, it is possible to achieve a very low operating volume. This makes it possible to connect even small mammals, such as rats or children, to the blood treatment. 5 V Λ 2 device without the need to add external blood.

A preferred embodiment of the present invention comprises a blood treatment device wherein the first plate comprises a first channel on one side and a second channel on the other side. This embodiment has the advantage that, among other things, material and space can be saved by applying the functions of two separate plates in a plate.

A further preferred embodiment of the present invention is characterized in that the angle between the first and the second direction is an angle in an interval of 30-90 °. A further embodiment provides third plates with third channels in a third direction for transporting cooling means therein. By transporting coolants it is possible to cool the blood during the treatment. By using a third direction, the blood and the air are not eligible with the coolants.

A further preferred embodiment of the present invention comprises the feature that the plates and the membranes are made from a biocompatible material. It is further preferred that the membranes are made of a microporous material for the passage of the gases, such as oxygen and carbon dioxide. An example of such a microporous material is polypropylene. Examples of biocompatible materials are stainless steel 316 (DIN 1.4401), stainless steel 316L (DIN 1.4404), AS TM F6795 or AS TM F1314-95, where the stainless steel codes are AlSI codes. The plates can be manufactured from these alloys.

A further embodiment of the present invention comprises one or more third plates comprising third channels in a third direction for cooling or heating the device. An important advantage of this is that the temperature of the blood can be varied during treatment. This cooling or heating can be effected by supplying a cooling or heating medium through the third channels. It is possible to add the third plates in the same ratio as first and second plates of the device or in a higher or lower ratio. For example, it may be sufficient to alternately add a third plate via ten first and second plates for cooling or heating purposes.

A further preferred embodiment of the present invention comprises a stack of the first plates, second plates and membranes for increasing the treatment capacity of the device. This treatment capacity is inter alia related to the size of the contact surface between the blood to be treated and the gas to be treated. On this contact surface, the blood is separated from the gas by the membrane. The contact surface is located at the intersections of the first channels and the second channels. The more contact surface is available for the passage of the gases, such as oxygen and carbon dioxide, the more gas can be exchanged. This contact surface can be increased by using more stacks of first and second plates with membranes between them or adding them to the device. Another possibility of increasing the contact surface is to increase the width of the plates, whereby more channels become possible per plate. In other words, by varying the number of plates and the size of the plates, the treatment capacity of the device can be varied.

Furthermore, the possibility is provided that the plates and membranes are contained in a housing. A further preferred embodiment thereof is that the housing holds the membranes and the plates pressed against each other. To this end, the tops and bottom of the housing can hold a stack of plates and membranes clamped in and the side walls of the housing can be clamped against the stack of plates and membranes. Such a method of constructing the device is a possibility of the * Ü t, J; 0 4 keep gas, blood and coolant flows separate, other than through the membranes.

In a further preferred embodiment of the present invention, the membranes are at least oxygen-permeable and carbon-permeable. The advantage of this is that the treatment can have at least an oxygen and carbon dioxide exchange effect.

Furthermore, a thickness of the plates of 100 to 200 μτη and a depth of the channels of 10 20 to 70 μτη and a width of the channels of 50 to 150 μτη are provided. These dimensions have the advantage that the Reynolds number, the pressure drop and the shear stress that influence the blood to be treated are within acceptable limits. Typical values for the Reynolds number are 0.21 to 0.37. For the pressure drop 4700 to 8200 Pa and for the shear stress 3.6 to 6.4 N / m2.

Since blood only damages with a shear stress above 15 N / m2 according to "red all Rheology", M Bessis et al, NY.

A further preferred embodiment of the present invention is characterized in that the first direction and the second direction or the third direction and the second direction are in the interval between 10 ° and 45 °. Furthermore, this embodiment can be characterized in that the largest first direction and the second direction or the third direction and the second direction are in the interval between 45 ° and 90 °. These characteristics have the special advantage that cooling can take place as well as use can be made of a minimum amount of blood volume. Another preferred embodiment of the present invention comprises a method for treating blood using a blood treatment device according to one or more of the embodiments described above. A further embodiment 35 provides for assembling a blood treatment device according to one or more of the claims 1 to 15 including steps for stacking plates and membranes. r): 5

Further advantages, features and details of the present invention will become apparent upon reading the following description of a preferred embodiment with reference to the accompanying figures, wherein: figure 1 is a perspective view of a composite embodiment of the present invention; figure 2 is an exploded perspective view of the embodiment of figure 1; figure 3 is a perspective view of an embodiment of the plates according to the present invention; figure 4 is a perspective view of another embodiment of the plates according to the present invention; figure 5 is a perspective view of a third embodiment of the plates according to the present invention; Figure 6 is a perspective view of a fourth embodiment of plates according to the present invention; figure 7 is a perspective view of a fifth embodiment of plates according to the present invention;

An embodiment of the present invention (Figures 1, 2) is a blood oxygenator with a very small so-called priming volume or working volume, the amount in the order of a few ml (milliliters) being around 3 ml for the embodiment described herein , lies. This volume can easily be increased with the aid of the present invention by using more modules according to the embodiment described here or by using larger modules.

A housing of the oxygenator 1 comprises a top plate 2 and a bottom plate 3 attached thereto with screw bolts la-1d. '6 edges are thicker than in a central part for the passage of blood and gas. The side walls 4 and 6 and 5 and 7 respectively are pressed towards each other by means of screw bolts 5a - 5d and 5 6a - 6d, respectively. The plates 4 and 6 are furthermore provided with an opening for blood tubes 8b and the plates 5 and 7 are provided with an opening for gas tubes 8g. These hoses are intended for the supply and removal of blood or gas. Inside the housing there are stacks of plates 11 and 12 with membranes 13. Between them channels are provided for transporting oxygen gases and in the plates 12 channels are provided for transporting blood. The membrane 13 separating the channels is permeable to gas-sen.

In this embodiment, the top and bottom plates are made of polypropylene that is advantageous and that is easy to machine. The two plates are preferably mutually as symmetrical as possible. The stacking of membranes and plates is fixed and clamped between the plates of the housing with the aid of the screw bolts in order to achieve a good seal.

In this embodiment, the side walls are made of polycarbonate. Polycarbonate is transparent, which means that any leaks can be easily located visually. Slotted holes (not shown) are provided in the side walls to make the housing applicable to various stacking heights of the membranes and plates.

Furthermore, a seal (not shown) is provided between the side walls and the edges of the plates. It is important that this sealing material is not too hard since a hard sealing material requires a greater pre-stressing force for a good seal. The prestressing force must, however, be minimal to limit deformation of stacking. to prevent. In this version (in a first prototype) there is twisted teflon tape combined with vaseline as 1 h:. .

7 seal applied. However, many types of seals could be used here.

As can be seen in Figure 3, the channels 14a are formed by the plate 11 and the channel partitions 14. The channels 15a are formed by the plates 12 and elevations 15 thereof. Blood flow B flows through channels 14a and gas flow G flows through channels 15a. Gas is then exchanged through membrane 13 between the gas flow and the blood flow. This involves an oxygen exchange from the gas stream to the blood stream and a carbon dioxide exchange from the blood stream to the gas stream. To this end, it goes without saying that the gas stream comprises at least oxygen and that the blood stream comprises at least carbon dioxide.

Since the channels are dimensioned very small and the membranes and plates are very thin, it is possible to provide a stack of many plates and membranes in the oxygenator. In the present embodiment, plates of 0.12 mm and membranes of 0.035 mm are used, the membranes consisting of microporous polypropylene. In the present embodiment, the channels have a width of 100 micrometers and a depth of 50 micrometers with the ribs having a width of 30 micrometers and a height of 50 micrometers. Here we start from the plates as shown in figure 2a. Therefore, two plates and 1 membrane are always required for a good functioning of a combination of these.

Another embodiment, that of Fig. 4, provides channels on both sides of the plates, namely crosswise to each other. In this embodiment, the membranes and plates can be stacked alternately for the oxygen and carbon dioxide exchange in the blood. An advantage of this embodiment is that stacking becomes simpler and that more space can be saved. A third embodiment (Figure 5) provides that the membrane is part of the plates or that the plates are made of the membrane material. In the first case, the rear wall 13d of the plates no '8 11b consists of the gas-permeable material. In the second case, the entire plate consists of the membrane material. The advantages of this embodiment are that gases can be exchanged along two sides of the channels, which on the one hand makes it possible to reduce the number of channels and on the other makes it possible to exchange more gases with the same amount of blood.

This embodiment has production technical and cost advantages in that the plates can be manufactured from, for example, polypropylene. The plates in this embodiment have both a channel / flow-through function and a membrane function. By means of a process such as hot-embossing, these plates 11 and 12 can be produced inexpensively and accurately.

A special embodiment (Figure 6) consists of hexagonal plates 31, 32 and 34 with a hexagonal membrane 33 instead of rectangular plates with two flow directions. In this embodiment, the channels 35a of plate 32 and 36a of plate 31 serve on similar In the same way as in previous embodiments for the passage of blood or gases, wherein the membrane 33 takes care of the exchange. A plate 34 with channels 37a is also provided by allowing an additional stream L which can be used for cooling and / or heating. Also in this embodiment, partitions 35, 36 and 37 are provided which together with the respective plates form the channels.

Because in the case of a rectangular embodiment of Figure 6 a higher blood volume per contact surface between the channels 36a and 34a is required, another rectangular embodiment (Fig. 7) with short blood channels 35a and longer gas channels 36a and coolant channels 37a is provided. . An advantage hereof is that there is an equally large contact surface between the blood and gas channels as in the embodiments of figure 2. Although more gas and coolant volume is required, this can be supplied in large quantities, while the quantity blood that is available in a human or animal body in 10173? 9. Certainly in the case of small animals or children, the amount of blood available is small.

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Claims (16)

A device comprising: 5. a first plate provided with a number of first channels in a first direction for transporting a fluid, such as blood; - a second plate near the first plate provided with a number of second channels in a second direction for transporting therein one or more gases or a mixture of gas-forming medium; and - a gas-permeable membrane arranged between the first and second channels. 2. Device as claimed in claim 1, wherein the first plate comprises first channels on one side and second channels comprises the other side. Device according to claim 2, wherein the angle between the first and the second direction is an angle in the 30-90 degree interval. Device as claimed in one or more of the foregoing claims, wherein third plates with third channels are provided in a third direction for transporting cooling means therein. 5. Device according to a. or more of the preceding claims, wherein the plates and the membranes are made from a biocompatible material. Device as claimed in one or more of the foregoing claims, wherein the membranes are made of a macroporous material. The device of claim 6 wherein the microporous material comprises polypropylene. Device as claimed in one or more of the foregoing claims, wherein the plates are made of stainless steel 316, RVS316L, ATSM F6795 or ASTM F1314-95. Device as claimed in one or more of the foregoing claims, further comprising: one or more third plates comprising third channels in a third direction for cooling the device. 1 Γ) * r ~ f ·. 10. Device as claimed in one or more of the foregoing claims, wherein the device comprises a stack of first plates, second plates and membranes for increasing the blood treatment capacity of the device. Device as claimed in one or more of the foregoing claims, wherein the plates and membranes are contained in a housing. 12. Device as claimed in one or more of the foregoing claims, wherein the housing holds the membranes and plates pressed against each other. Device according to one or more of the preceding claims, wherein the membranes are permeable to at least oxygen and carbon dioxide. Device according to one or more of the preceding claims, wherein plates have a thickness of 100 μτη a 2 00 μτη and the channels have a depth of 20 μτη a 70 μτη and a width of 50 μτη a 150 μτη. 15. Method for treating blood with the aid of a device according to one or more of the preceding claims. A method for assembling a device according to one or more of claims 1-15 comprising steps for stacking plates and membranes.