DE2141602A1 - Lid for a dialysis machine or the like - Google Patents

Description

dr. W. Schalk dipl.-ing. P. Wirth dipl.-ing. G. Dan ν en berg DR. V. SCHMIED-KOWARZIK · DR. P. WEI NHOLD · DR. D. G UDEL

6 FRANKFURT AM MAIN

CR. ESCHENHEIMER STBASSE 39

18th August 1971
There is

Baxter Laboratories, Inc. Morton Grove, Illinois 60053, USA

Lid for a dialysis machine or the like.

The invention relates to devices, their operation is based on diffusion through a semipermeable membrane, especially dialysis machines and especially artificial ones Kidneys, and it concerns a special cover that is placed on the housing of the device around the dialysis chamber to close. It is advantageously provided that the cover attached to the housing in a sealing manner over a valve in the outflow for the dialysis medium enables the pressure within the chamber to be controlled.

The most diverse forms of dialysis machines are already known, as is the chemical phenomenon on which such Devices are based. With most devices, however, one has to contend with difficulties arising from the diffusion of V / ater during dialysis, which is usually not allowed. The present invention addresses this difficulty by controlling the pressure in the dialysis chamber and thus the pressure gradient across the membrane.

It should be pointed out briefly that in the field of medicine, dialysis is carried out in an extracorporeal system,

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and serves to extract various harmful organic and inorganic from a biological medium, for example blood Eliminate substances. For the present description of the invention, blood is assumed as the biological medium .

One known form of dialysis machine includes a blood flow chamber in the general shape of a greater length a hose, in particular a plastic hose, which is around a core can be wound around, as well as a dialysate chamber, within which the blood chamber is housed and through which a dialysis medium or a V / ash solution flows. By suitable support of the tube, which can consist of a semipermeable dialysis membrane over its entire length, for example Cuprophan (a cellophane-like I-Iembrari on Cellulose-based), the dialysis medium can flow over a maximum proportion of the membrane surface. The flow of blood and dialysis medium over each increment of the membrane on its opposite sides is preferably steady and continuous held, namely - also along the membrane surface, where the presence of a current is particularly important. The formation of a stationary liquid film on the membrane surface namely, would reduce the effectiveness of the solution diffusion.

As a result of the driving force (gradient of chemical concentration) between the on both sides of the semi-permeable Membrane moving media occurs passive physical diffusion of organic and inorganic substances on. In order to maintain the concentration gradient with continuous circulation of the dialysis medium within the circulation system, it is preferably carried out continuously a small volume of the dialysis medium is withdrawn and replaced with fresh medium. This is well known.

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Ultrafiltration occurs during solution diffusion. Ultrafiltration is a phenomenon that is not fully explained. Further, a full discussion of what is believed to be the scientific principle and rationale for the occurrence of water diffusion from blood plasma is beyond the scope of the present invention. However, it is believed that ultrafiltration is a consequence of or a function of the characteristics of many dialysis seger ate. Ultrafiltration depends, among other things, on the pressure gradient across the membrane, the area of the dialysis machine and the perfusion flow rate, the water permeability of the membrane and the boundary layer conditions. Of these, the most important Λ aspect is probably the pressure gradient across the membrane.

The mean pressure gradient across the membrane in a dialysis machine with a winding is of a complex nature. It is probably the result of the sum of a large number of pressures. Suppose the bloodstream behaves like a rigid one System, then the pressure drop has a linear function according to Poiseiulle's equation.

Δϋ _ 19 ii T

1, 'IP

whereju is the viscosity of the test solution in dyn-sec / cm, L and W length and width of the bloodstream in the dialysis machine in cm, II the thickness of the bloodstream in cm and Qg the flow rate of the ■ 'est solution in cm / sec. For a given set of stationary The pressure drop across the blood chamber in the dialysis machine can then be approximated as the difference between the conditions Pressure measurements at the inlet and outlet are recorded.

^P in ^P out

The mean pressure in the blood chamber would be the mean pressure

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- 4 between inlet and outlet.

TP = ^P in ^{+ P} oyit (3)

The mean pressure across the dialysate chamber would be the mean pressure between its inlet and outlet in the dialysis machine.

^P Din ⁺

2 (4)

The true pressure across the membrane can be calculated as the difference between equations (3) and (4): / P _1n + Pput \ _ / Pp ₁ + PP _O ^ l _in mmHg (5) V 2 J blood I 2 / dialysate

The osmotic pressure gradient of the blood, although very important, is transverse in this way of calculating pressure to the membrane not taken into account. It mean

TF = pressure across the membrane in mmHg

P. = inlet pressure of the bloodstream in mmHg

P ._ = outlet pressure of the bloodstream in mmHg

P _Di = inlet pressure of the dialysate in mmHg

Do = outlet pressure of the dialysate in mmHg

According to this hypothesis, the ultrafiltration can be changed by influencing the pressure across the membrane. In Practical attempts were made by increasing the resistance at the dialysate outlet by means of a valve actuation to reduce it the flow increases the hydrodynamic pressure in the dialysate chamber. Because the pressure in the blood chamber is greater than the pressure in the dialysate chamber is under atmospheric conditions, means an increase in the pressure in the dialysate chamber

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a reduction in the pressure gradient across the membrane.

The amount of water diffusion seems to be partly directly dependent on the pressure across the membrane. Although, as mentioned, the Phenomenon cannot be fully explained, it was found in experiments that there is a pressure value in the dialysate chamber,

.constant where for any / perfusion flow the volume of the Water diffusion becomes smaller and then balances out to a relatively constant volume. It seems, therefore, for some any perfusion flow rate an optimal pressure to give, above which there is no noticeable reduction in ultrafiltration.

It is believed that this is a result of the reduced effectiveness of the positive dialysate pressure upon further reduction of the pressure gradient across the membrane. In this regard, as the dialysate pressure is increased, there is a pressure increment transferred to the blood reservoir. It is therefore believed that the control of the ultrafiltration means under pressure dialysis carried out at high pressure in the dialysate chamber is self-limiting.

Significant loss of blood volume during dialysis is inadmissible. Because a large percentage of them are chronic Hemodialysis patients receive little or no blood transfusions during therapeutic treatment Maximum blood return from the dialysis machine is of paramount importance.

With the present invention, the pressure gradient across the membrane can be reduced in that the dialysate chamber is pressurized to thereby increase the volume of the diffusing from the plasma within the blood chamber into the dialysate chamber To diminish water. This result could be achieved without impairing the cleaning effect of the dialysis machine

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be achieved.

According to this particular aspect of the invention, it is provided to use a cover that is on the outer, the housing of a dialysis machine forming the dialysate chamber of the type that contains a coiled tube as a blood chamber, is attachable. It should be noted, however, that the principle disclosed with the invention also applies to dialysis machines other types that do not work with a winding can also be used to advantage. The lid is with sealing devices provided, which allow the build-up of an overpressure in the dialysate chamber. The lid has a passage on, through which the dialysis medium can escape from the chamber for reverse circulation or other forwarding, so-ie a valve device associated with this passage, via which the flow resistance can be changed in order to build up pressure in the dialysis chamber or to release it from it. An increase in pressure simultaneously reduces the pressure gradient across the membrane.

According to a preferred embodiment of the invention, the cover can be designed as an essentially one-piece unit be, while according to a modified embodiment of the lid a substantially flat plate and one with the Plate can have cooperating ring part, which serves as a bearing for the plate on the housing. The plate shows just like the cover described above, in connection with the outflow passage for the dialysis medium, a valve device on. The ring part contains a number of cutouts for the passage of one or more flexible hoses, which form part of the blood circulation system and are used to connect the blood chamber contained in the device.

Furthermore, according to one embodiment of the invention, a guide block is provided in the cover, which both the receptacle

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as well as the definition of a number of flexible tubes which the blood compartment or the blood chamber to the blood circulation system serves connect. Here, the guide block is opposite a corresponding section of the cover can be pivoted into and out of this and can be moved up and down along a longitudinal axis of the cover, when the hoses are picked up. The block contains a number of semicircular hats with complementary grooves cooperate in the lid to hold the hoses in place.

Further, the invention provides an apparatus Λ zum.Messen the pressure can be provided within the dialysate in accordance with expedient. For this purpose, a bore in the cover communicates with the chamber and carries a connecting piece for connecting a suitable pressure gauge.

Above, the more important features of the invention have been set out in a somewhat more general form in order to facilitate understanding of the following description of examples and to illustrate the technical progress that can be achieved. Further features of the invention are described in more detail below and are the subject of the claims. However, it will be apparent to those skilled in the art that the concept on which the disclosure according to the invention is based can also serve as a basis for the construction of other embodiments by means of which the objects of the invention can be achieved. The basic idea of the invention can therefore also be implemented in other types of embodiment.

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The invention is described below with reference to the drawings, for example explained in more detail, namely show:

Fig. 1 partially broken away and in section, a view of a dialysis machine having a winding with lid according to the invention;

Fig. 2 is a side view of the lid of Figs separately therefrom the upper part of the housing to which the lid is sealingly attached;

3 shows a plan view of the cover; 4 shows a view of the cover from below;

Fig. 5 is a vertical section along the line 5-5 of Fig. 3, which the outlet through the lid and shows therein a valve insert;

Fig. 6 is a perspective view of a part of the cover with the connector section for supporting one or multiple flow lines;

Fig. 7 is a partial section through the lid showing how the lid is attached to the housing;

8 and 9 are partial vertical sections through the connector portion of the lid, which arrangement and Clarify the support of the flow lines;

FIG. 10 shows a horizontal section along the line 10-10 of FIG. 5, which illustrates the actuation of the valve insert;

11 shows, in an exploded view, another embodiment of a lid according to the invention

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with the upper part of the housing to which it is attached;

FIG. 12 is a broken vertical section showing the position of the cover according to FIG. 11 on the housing;

13 shows a view of the cover of FIG. 11 from below, but without the intermediate ring;

14 is a vertical section along the line 14-14 of 13 'but with part of the intermediate ring and the housing; and

FIG. 15 is a view corresponding to FIG. 12, but with one of the clamping members for attaching the cover to the housing.

A dialysis machine having a winding, for which a cover according to the invention is suitable, is shown in FIG. 1. Although the construction of the dialysis machine and its mode of operation are not of importance for understanding the invention it seems important to explain the relationships in order to better understand the invention.

In the case of an extracorporeal device, as shown in FIG. 1, passive physical diffusion takes place in an undesirable manner of organic and inorganic substances through a semipermeable membrane as a result of a force (chemical concentration gradient) which, in the case of two flows, is opposite to two Sides of the semipermeable membrane results. To allow the diffusion of substances from the blood with acceptable effectiveness To achieve, it is useful to dialysis flow a to expose the maximum membrane area. At the same time, however, the membrane requires that consist of a large length of tubing can provide a support over its entire length. This is especially true of a winding-type dialysis machine such as that shown in FIG Fig. 1 is shown. Hence, as this is shown schematically

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is a substantial length of supported membrane tube 10 wound on a core 12, within an area which is delimited to the outside by a housing 14. The one used for this Support is not shown in detail because the way it is carried out is of no importance for the invention. It should be noted, however, that the support serves a dual purpose, namely to support the membrane and to maximize it Exposing the surface of the same to the dialysis flow.

Although this is not shown, it should be noted that the membrane to an extracorporeal flow of to be dialyzed The concentration gradient across the membrane results from the dialysis flow the opposite side of the membrane over its entire coiled length. For this purpose, the dialysis medium is in the Pumped area within which the wound membrane is located. One from a pump (not shown) The incoming line 16 (FIG. 1) is screwed onto an inlet socket 18 in the bottom wall 20 of the dialysis machine. With help a somewhat conically shaped distributor plate 22 and a perforated ring 24, for example, can be used Dialysis medium can be evenly distributed so that it is uniform over the entire surface of the membrane to the, later still explained, dialysis spout flows.

In order to maintain a constant circulation of the dialysis medium in a closed system, it is connected to the The outlet is received by a reservoir in the form of a container 26 which rests on a base plate 28. Any suitable System can be used for this and such systems are state of the art. However, there the efficiency dialysis gradually decreases during operation, because the diffusion gradient is continuously decreasing, it is advisable to use a Draw off a small portion of the dialysis medium and replace it with fresh medium in order to reduce the diffusion gradient maintain. For this purpose, the reservoir or the container 26 can be provided with an overflow, which the

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Determined level height or with a tap 30 within the container wall 26.

An outlet for the dialysis medium is provided in the lid, which is designated as a whole with 50 and is described in more detail below.

The lid is shown with a generally flat surface 52 and generally circular in shape. As particularly apparent from Fig. 2, extends from the circumference of the cover, an annular extension 54 downwards, the one Forms a support surface for the cover on the housing 14, which has an outwardly directed horizontal flange 56 (Figo 2) is provided. The lid 50 can be made of any material, for example for casting and subsequent Editing is suitable. The material of the lid should also allow a robust construction to allow a to give a stable and rigid device part. The design of the cover should also be such that the desired printing conditions can be maintained within the enclosed space. Generally, commonly used Metals, such as aluminum, or one of the known plastics, such as polypropylene, high density polyethylene, Lucite (trademark for a polymethyl methacrylate) and other uses Find. If the cover is to be transparent or translucent, plastic is the preferred material.

As can be seen in particular from FIGS. 7 and 9, the cover 50 rests with the base of the annular extension 54 on the Flange 56 of the housing. Another annular extension 58 is received in the upper opening of the housing 14 to to center the cover with respect to the housing. An O-ring on the underside of the annular extension 54 is used to airtight seal of the interior space in the housing, within which the membrane is located. Spread around the lid and rigidly or integrally connected to this, are one

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Number of clamping devices provided, each with a post 62, through whose axial bore 64 a threaded bolt extends, which ends in a foot part 68 and by a knurled nut 70 or the like. can be attracted. Preferably three or four such clamping devices are provided to secure the cover 50. Here the foot part reach under; 68 the flange 56 of the housing, and by operating the knurled nut 70, the O-ring 60 is fixed between the annular Extension 54 of the cover and the flange 56 of the housing clamped.

Some projections 72 (Figs. 1 and 4) are solid or integral provided on the underside of the cover 50. They are used in conjunction with the perforated one attached to the bottom of the housing 14 Ring 24 of the axial support of the wound membrane 10.

The body of the cover 50 has an approximately trapezoidal recess 74 (FIG. 6) on the circumference within a sector. The upper part of the recess is cut out deeper than the lower part, so that a shoulder 75 is formed. A guide block 76 is pivotable into the recess and is vertically displaceable between those shown in FIGS. 8 and 9 positions shown. The meaning of this possibility of movement is explained in more detail below. block 76 is dimensioned so that it is aligned on the one hand with the shoulder 75 and on the other hand the peripheral surface of the Cover supplemented, as can be seen from FIG.

Fig. 6 further shows two hinge parts 78 and 80, one of which on the guide block 76 and the other on the body of the Lid 50 are stored. The guide block is articulated by means of a pin 82 via the hinge parts. One Closing plate 84 with knurled screw 86 are used to fasten the guide block 76 in the working position.

By semicircular grooves 88 and 90 (Fig. 8) the one on top of the other aligned in shoulder 75 and in the guide block

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are provided, a number of circular openings 92 are formed. These openings accommodate hoses 94 that serve to connect the membrane within the housing to an extracorporeal bloodstream. By having a sentence or multiple sets of two openings 92 are provided, a single or double wrapped membrane can be attached to the Be connected to the system.

The movement of the guide block 76 between the positions shown in FIGS. 8 and 9 initially enables the partial Support of the hoses 94 in the semicircular grooves and 90 (Fig. 8), whereupon the guide block 76 is lowered (Fig. 9), in order to hold the hoses 94 firmly in the openings 92 (see also Figs. 3 and 4). Just by one Pivotal movement of the guide block 76, the tubes could not be detected. If they were in the grooves 88, so they would be crushed when closing the guide block.

An outlet 96 (FIGS. 3-5) is also formed in the body of the cover 50. This outlet or channel is used to deliver the Dialysis medium from the interior of the vessel 14 to the reservoir in the container 26. At the end of the outlet 96 there is one Baffle 98 which directs the flow into the reservoir.

The spout 96 includes a horizontal portion 100 in connection with a vertical portion 102. Within the In the vertical part there is a rotatable valve insert 104, by means of which the outflowing volume can be controlled.

The valve insert 104 has a substantially cylindrical Hollow shaft 106 with a lateral opening, the size of which corresponds approximately to the cross section of the horizontal section 100. The shaft 106 ends in a handle 110, by means of the valve insert 104 of which can be rotated to adjust the flow of the dialysis medium. A fork-shaped bracket 112

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(Fig. 3) engages in an annular groove 114 (Fig. 5) of the valve insert 104 to prevent it from axial movement while being freely rotatable to secure.

When the device is in operation, the cover 50 is as described above Manner, and the blood to be purified is passed through the wrapped membrane. At the same time will Dialysis medium introduced into the housing via the line 16 (FIG. 1), and because of the diffusion gradient across the Membrane cleans the blood by diffusing unwanted organic and inorganic substances. Usually the pressure within the bloodstream is higher than the pressure within the housing, creating a pressure gradient across the Membrane to ultrafiltration or diffusion of water to the area of the lower pressure takes place. Through suitable Actuation of the valve 104 can increase the pressure within the housing 14 and thus reduce the pressure gradient to reduce the release of water by diffusion from the plasma. The pressure in the housing 14 can increase a pressure gauge 116 (Fig. 2) can be read, the over a connector 118 is in communication with the interior of the housing 14, so that by means of the valve insert 104 and a desired pressure can be maintained during the reading.

In the slightly modified embodiment of the invention 11-15, the cover 200 consists of a plate 202 and a ring part 204. The ring part 204 corresponds approximately to the annular extension 54 of the cover 50 according to FIG. Likewise, the plate 202 essentially corresponds to the corresponding part of the cover 50.

The outlet for the dialysis medium consists of several passages 208-214 (FIG. 13), which are connected to the interior of the Housing 14 are in communication. Because the passages have different cross-sections, the flow volume can

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and thus the pressure inside the housing with some Accuracy can be controlled. A guide element 206 (FIG. 14) serves as a splash guard and for transferring the dialysis medium into the reservoir.

A control member, generally designated 216, is rotatably mounted on the guide element 206 and the cover plate 202. It has a shaft 218 which delimits an adjusting knob 220 at the top and a flat, curved knob at the lower end Control plate 222 carries. By properly adjusting the control plate 222 to cover one or more of the Openings 208-214 can control the volume flowing out of the housing 14.

The ring part 204 and the plate 202 are mounted on the housing 14, an O-ring 230 is on the ring part for sealing provided, which rests against the flange 56 of the housing 14, while a z \ ireiter O-ring 232 as a seal between the Ring part 204 and the plate 202 is used. As with the first run sb ei game is a projection 234 on the ring part 204 for Centering the cover 200 on the housing 14.-

A number of Klemmg3.ieder 236 are mutually spaced attached to the top plate 202. As FIG. 11 shows in particular, a clamping member designated as a whole by 236 is used rotatably mounted on a pin 238, for example by friction or in another suitable manner within a Opening 240 is held in the plate 202, such openings being approximately at a distance of 90 ° in the plate 202 are located. Since the clamping members are designed in the same way, only one is shown in the drawing. The clamping member has a fork-like part 242, the base 243 of which receives the pin 238 with the clamping member around the pin is pivotable. An arm 244 with a hook end 246 is pivotably mounted on the fork-like part 242. Through appropriate The pivoting movement engages behind the hook end 246

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Flange 56 on the housing 14, whereby the cover 200 is attached to this.

A bore 250 in the cover plate 202 ends in one Pipe socket 248 for connecting a pressure gauge corresponding to the pressure gauge 116 of the first embodiment.

Whereas in the first exemplary embodiment a guide block 76 was provided on the cover 50 in order to surround the flexible hoses 94 To detect, the ring part 204 of the second embodiment has a number of channels 252 (Fig. 12) for carrying out the Hoses on. The O-ring 232 works in conjunction with these channels hold the hoses firmly without squeezing them.

A cover designed according to the invention for a dialysis machine thus advantageously solves the problem of a reliable sealing with the possibility of controlling the pressure inside the housing at the same time. Such a lid can of course also be used advantageously for other devices where similar conditions or problems exist.

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Claims (19)

Patent claims: 1. A lid suitable for a dialysis machine, in particular a dialysis machine that has a dialysate chamber through which dialysis medium constantly circulates and is in contact within the chamber with the surface of a blood container serving to receive a blood flow, which is surrounded by a membrane as a semipermeable partition
is formed between the dialysis medium and the blood,
diffuse through which undesired organic and inorganic substances under the action of a concentration gradient from the blood, characterized in that the cover (50; 200) can be attached to the device to seal the dialysate chamber (14) from the environment and has an outlet (96; 208 - 214) for that out of the chamber
having incoming dialysis medium, wherein an adjusting device (104; 216) cooperating with the outlet for
the outflowing volume of the dialysis medium is provided, whereby the pressure in the chamber (14) and the pressure gradient across the membrane (10) can be changed. 2. Apparatus according to claim 1, characterized in that the outlet has a plurality of channels (100, 102; 208-214). 3 » Device according to claim 2, characterized in that the channels (208-214) have different cross-sections
to have. 4. Apparatus according to claim 1, characterized in that ■ a guide body (98; 206) for over the end of the outlet the dialysis medium is provided. - Claim 5 - 209811/1555 ■ ¹⁸ ~ 2U1602 5. Apparatus according to claim 4, characterized in that a through the guide plate (206) and the cover (200) rotatably mounted shaft (218) extends, and that the adjusting device (216) with a at the lower end of the Shaft provided plate (222) is formed, which is used to adjust the flow volume with the shaft is movable. 6. Apparatus according to claim 5, characterized in that the outlet has a plurality of channels (208-214), and that the plate (222) is movable to close one or more of these channels. 7. The device according to claim 2, characterized in that one of the channels of an axial, substantially cylindrical bore (102) through the cover (50) and another of one communicating with this Transverse bore (100) is formed. 8. Apparatus according to claim 7, characterized in that the adjusting device is a substantially cylindrical Has cup part (106) which is rotatably mounted in the first bore (102) = and an opening (108) inside the side wall, the size of which corresponds approximately to the cross section of the transverse bore (100). 9. Apparatus according to claim 8, characterized in that the cup part (106) outside of the lid (50) carries an actuating element (110) via which the position its opening (108), and thus the flow of the dialysis medium is adjustable. 10. Apparatus according to claim 8 or 9, characterized in that the cup element (106) has its axial position with free rotation within the bore (102) 209811/1555 ^: - is - 2H1602 securing device (112, 114) is assigned. 11. The device according to claim 1 or one of the subsequent claims, characterized in that passages (92; 252) provided for the unimpeded passage of at least one inlet and outlet hose (94) into the chamber (14) are, with the tubes located in the chamber blood container with an extracorporeal Flow system is connectable. 12. The apparatus according to claim 11, characterized in that the cover (200) has a plate-like part (202) and a Has ring part (204) and as passages a plurality of substantially radially arranged grooves (252) on the top of the ring part and, after the two parts (202, 204) have been joined together, adjacent to the plate-like part, and that an element (232) connecting them in a sealing manner is mounted on one (202) of the two parts. 13. The apparatus according to claim 11, characterized in that the cover (50) on the circumference with a substantially trapezoidal recess (74) is provided, the lower part of which has a shoulder (75), and that the passages to the chamber (14) are formed by means of a guide block (76) which has a plurality of essentially axially extending grooves (90) having circular passages cooperating with an equal number of grooves (88) in the shoulder (75) (92) form for the hoses (94). 14. The device according to claim 13, characterized in that the guide block (76) by means of a hinge device (78-82) on the cover (50) both from a lower normal position within the recess (74) into a raised one Movable position as well as in the raised position from the recess (74) for inserting the hoses (94) pivotable into the grooves (90) and then into the 2 0 9 8 11/15 5 5: 2U1602 Normal position can be returned, whereby the hoses (94) can be fixed in the circular openings (92). 15. Device according to one of the preceding claims, characterized in that the cover (50; 200) devices (66 - 70; 236) are assigned for attachment to the device. 16. The apparatus according to claim 15, characterized in that a seal (60; 230) for the connection between Lid and device is mounted on one of these two parts. 17. The device according to claim 16, characterized in that the seal (60; 230) is an O-ring. 18. Device according to one of the preceding claims, characterized in that a connecting part (118; 248) for a measuring device (Ii6), via which the pressure in the chamber (14) can be determined, is provided on the cover (50; 200) « 19. Dialysis machine with one of a winding core (12) and one This housing (14) which surrounds this at a distance is formed by a dialysate chamber, within which one serves as a blood compartment Hose membrane (10) wound on a support and attached to a circulating flow of a biological medium can be connected, a connecting part (18) for a supply line (16) of dialysis medium to the dialysis fluid chamber is provided, as well as a cover (50; 200) having an outlet (96; 208-214) for the dialysis medium and one with this cooperating adjustment device (104; 216) for adjusting the outflowing volume, whereby The pressure gradient across the membrane (10) and the diffusion rate via the pressure in the dialysate chamber (14) can be influenced, and that a fastening device 20981 1/1555 (66-70; 236) is provided for the cover (50; 200) on the chamber (14). Patent attorney: 209811/1555 XL. Blank page