Abstract:
A dialysis fluid cassette that includes a base and a flexible membrane attached to the base. The flexible membrane and the base cooperate to at least partially define a venting chamber and a fluid channel fluidly connected to the venting chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of and claims priority to U.S. application Ser. No. 13/237,149, filed on Sep. 20, 2011, which is a continuation application of and claims priority to U.S. application Ser. No. 12/627,043, filed on Nov. 30, 2009, which is now U.S. Pat. No. 8,142,653, which is a continuation application of and claims priority to U.S. application Ser. No. 10/516,528, filed on Dec. 2, 2004, which is now U.S. Pat. No. 7,648,627, which is a nationalization of PCT/EP03/05377, filed on May 22, 2003 and published in German, which claims priority under 35 U.S.C. §119(a) to DE 102 24 750.1, filed on Jun. 4, 2002. 
    
    
     TECHNICAL FIELD 
     The invention relates to an apparatus for the treatment of a medical fluid comprising a fluid treatment machine and a cassette insertable therein substantially consisting of a rigid base body of the cassette with fitted chambers and passages and a foil covering them. 
     BACKGROUND 
     Cassettes are used in medical engineering, in particular to convey dialysis fluid, blood and the like. 
     A cassette can include a base body with fitted chambers and passages which is closed by a flexible foil to cover the passages and chambers. The cassette can be inserted into a special receiving chamber, e.g., in a dialysis machine. This chamber can, for example, be opened via a pivotable door. The cassette can be inserted into the chamber, with the flexible foil lying opposite a corresponding mating piece at the machine so that the cassette can be operated with the aid of actuators and sensors on the machine side. 
     Conventional extracorporeal blood circuits or blood tubing systems are usually present in a differential construction. This means that a functional division onto different components is present. Such components (e.g., bubble traps, flow chambers or injection positions) are connected to one another by tubes and are as a rule connected individually to the respective dialysis machine. The design of such blood tubing systems is very complex in manufacture and handling, with the corresponding effort naturally being extremely time consuming with more complex systems such as an online hemodiafiltration. 
     On the other hand, conventional extracorporeal blood circuits which are installed in this differential construction have the advantage that they can be designed substantially more flexibly for the respective treatment depending on the demand. Previously known apparatuses for the use of cassettes typically were only usable for a very specific application. 
     SUMMARY 
     Certain aspects of the invention relate to a generic apparatus comprising a fluid treatment machine and a cassette insertable therein such that a large flexibility for different applications is made possible while maintaining the fast and simple exchangeability. 
     In some aspects of the invention, actuators and sensors are arranged in a generic apparatus for the treatment of a medical fluid for the operation of the apparatus with an inserted cassette such that cassettes are insertable in different integration shapes. 
     Due to the clearly defined arrangement of corresponding sensors and actuators, cassettes of different complexity can be inserted into the fluid treatment machine in accordance with the desired application. It is therefore not necessary to provide different apparatus for different applications. 
     A cassette for a standard hemodialysis can thus be insertable here, for example. The corresponding pump chambers, measuring sensors and further actuators, such as valves, etc., are provided at pre-determined locations in the fluid treatment machine. Additional pumps, actuators, valves, etc. are provided in the fluid treatment machine which do not have to be actuated when the cassette is used for standard hemodialysis. They are, for example, only in use when a cassette is used for online hemodiafiltration or online hemofiltration. Further passages, pump chambers, etc. are provided at corresponding positions in the corresponding cassettes which are associated with these actuators, pumps or valves. Furthermore, a cassette for an acute dialysis treatment can be inserted in which in turn the pumps, actuators and valves provided on the side of the fluid treatment machine are associated with corresponding pumping chambers, passages, etc. The associated control electronics can be selected depending on the inserted cassette for the control of the pumps, actuators, sensors, etc. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       Details and advantages of the invention will be explained in more detail by way of example in the following with reference to the Figures. There are shown: 
         FIG. 1 : a schematic plan view of a cassette for standard hemodialysis; 
         FIG. 2 : a schematic plan view of a cassette in accordance with the invention according to a further embodiment of the invention for use in online hemodiafiltration or online hemofiltration; 
         FIG. 3 : a plan view of a cassette in accordance with a further embodiment of the present invention which can be used for acute treatment; 
         FIG. 4 : a schematic plan view of a further aspect of the invention which substantially corresponds to that in accordance with  FIG. 1 , but has an integrated dialyzer; 
         FIG. 5 : a further aspect of the invention which substantially corresponds to that in accordance with  FIG. 2 , but has an integrated dialyzer; 
         FIG. 6 : a further embodiment of the invention which substantially corresponds to that in accordance with  FIG. 3 , but has an integrated dialyzer; 
         FIG. 7 : a three-dimensional representation of a fluid treatment machine as an embodiment of the apparatus in accordance with the invention without an inserted cassette; 
         FIG. 8 : a representation corresponding to  FIG. 7 , but with an inserted cassette; 
         FIG. 9 : a representation in accordance with  FIG. 7 , but with a different embodiment variant of a cassette differing from the cassette shown in  FIG. 8 ; 
         FIG. 10 : a detail of a venting unit in the apparatus in accordance with the invention; 
         FIG. 11 : a detailed view of a contour of a measuring chamber in a cassette in accordance with one of the aforesaid embodiment variants; 
         FIG. 12 : a partially sectional representation of a pump chamber of the cassette in accordance with the present invention; 
         FIG. 13 : a partially sectional representation through a passage of the cassette in accordance with an embodiment variant of the invention; 
         FIG. 14 : a cross-sectional view of a valve; 
         FIG. 15 : a diagrammatic view of the valve of  FIG. 14  in use in a disposable cartridge; 
         FIG. 16 : a perspective view of a fluid guide body having an open main passage and a secondary passage opening therein in accordance with an embodiment of the invention in a sectional representation; 
         FIG. 17 : a perspective view of a base body of the cassette of  FIG. 1  in a partial section, wherein a covering film is pressed onto the fluid guide body by a valve actuator and closes the secondary passage; 
         FIG. 18 : a perspective view similar to  FIG. 17 , wherein the secondary passage is represented in its open position; and 
         FIG. 19 : a schematic, 3D representation of a section of an elastic matt according to an embodiment of the present invention; 
         FIG. 20 : a section along the section line A-A′ in  FIG. 19 ; 
         FIG. 21 : a section along the section line B-B′ in  FIG. 19 ; 
         FIG. 22 : a section along the section line C-C′ in  FIG. 19 . 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a cassette  10  in accordance with an embodiment of the present invention is shown which can be used for standard hemodialysis. In  FIG. 1 , the surface of the cassette  10  is divided into a hatched region B (two partial areas) and a non-hatched region A. Both the surface of the cassette  10  and the surface of an associated machine block  108  (shown in  FIG. 7 ) are divided into the covering surface regions A and B. Components of actuators or sensors to be coupled, which are common to all cassettes as basic variants (e.g., all the cassettes for standard hemodialysis) are accommodated in the surface region A (not hatched in  FIG. 1 ), and the surface region B denotes a region in which actuators or sensors to be used optionally are provided in the machine block  108  (shown in  FIG. 7 ). As discussed below,  FIG. 2  illustrates a cassette that includes operable components in a region corresponding to a surface region B. 
     The cassette consists of a base body  12  of a cassette which consists of polypropylene in the embodiment shown here. A cover foil  14  (shown in  FIGS. 10 ,  12 ,  13 ,  17 , and  18 ) consisting, for example, of a polyolefin elastomer mixture, is applied to the base body  12  of the cassette  10 . The passages and recesses, which will be looked at in more detail later, are covered by this cover foil  14 . An arterial injection septum  16  is provided in the arterial line  18  to the dialyzer and a venous injection septum  20  is provided in the venous line  22  to the dialyzer. The dialyzer itself and the corresponding tube connection are not shown in any more detail in the embodiment shown here. Reference number  24  designates the blood inlet from the patient and reference number  26  designates the blood outlet to the patient. The respective tubes, which likewise consist of a polyolefin elastomer mixture, are also not shown here for reasons of simplification. Passages  28  are recessed in the base body  12  of the cassette  10 . They are acted on by a row of valves  30 . 
     These valves  30  have a valve body with a pressure passage and a sealing cap which cooperates with the valve body such that it closes the end of the pressure passage on the valve body side with respect to the environment, with a pressure space being able to be built up between the pressure passage and the sealing cap so that the sealing cap has a deformable sealing region for entry into the fluid passage in order to close this as required. 
       FIG. 14  shows one of the valves  30  in a sectional view, which is rotation-symmetric about a vertical axis. The valve  30  includes a valve body  112  with a pressure channel  114 , which ends in a pressure chamber  116 . A sealing cap  118  with a deformable area  120 , which bounds the pressure chamber  116 , is placed over the valve body  112 . 
     The pressure channel  114  of the valve body  112  is elongated, so that it can be inserted, for example, through the body or a wall of a counterpart of the disposable cassette  10  on the device side (i.e., through the machine block  108 ) and can be screwed down with a lock nut  122 . A thread is provided on the outer wall of the portion of the valve body  112  that forms the pressure channel  114  to allow the lock nut  122  to secure the valve body  112  to the machine block  108 . The valve body  112  has sealing surfaces  124  for sealing the valve body  112  in the machine block  108 . The sealing cap  118  includes protruding bulges  126 , which surround the valve body  112  in such a way that they lie adjacent to the sealing surfaces  124  and are pressed when the valve  30  is assembled. 
     Still referring to  FIG. 14 , the upper area of the valve  30  is the area on the fluid passage side (i.e., the side nearest the cassette  10 ). A projection  130  of the sealing cap  118  lies on the end of the valve body  112 , on the fluid passage side. A shoulder  128  of the sealing cap  118  is provided to ensure that that the sealing cap  118  fits into its associated fluid passage in the cassette  10 . 
     The valve  30  is shown diagramatically in use in  FIG. 15 . The base body  12  of the disposable cassette  10  in which liquid passages  28  are formed is shown in diagrammatic representation. The corresponding counterpart of the disposable cartridge body on the device side (i.e., the machine block  108 ) is shown pressed against the cassette  10 . 
     The valve  30  is inserted into a suitably shaped housing (e.g., recess)  138  of the machine block  108  and screwed down with the lock nut  122 . The shoulder  128  lies adjacent to the edges of the liquid passage  28 . The movement of the deformable area  120  when an excess pressure or partial vacuum is applied or with venting of the pressure channel  114  is indicated by arrow  140 . Reference number  142  indicates the direction in which the pressure is applied in order to close the valve  30 . As shown in  FIG. 15 , the housing  138  in the machine block  108  is rotation-symmetric about the pressure channel  114  of the valve  30 , and the liquid passage  28  extends perpendicular to the plane of the figure. 
     A cut-out for accommodating the shoulder  128  can be provided either in the base body  12  of the cassette  10  or in the machine block  108 . It is also possible for the shoulder  128  to be accommodated in a suitable opening in a cover mat located between the cassette  10  and the machine block  108 . 
     For the sake of clarity,  FIG. 15  does not show the cover foil  14  of the cassette  10 , which closes off the fluid passage  28  against the surroundings. The cover foil  14  (shown in  FIGS. 10 ,  12 ,  13 ,  17 , and  18 ) can be fixed on the side of the base body  12  of the cassette  10  that is pressed against the machine block  108 . The cover foil  14  is sufficiently flexible so that it can follow the deformation of the deformable area  120  of the sealing cap  118  of the valve  130 . 
     For the operation of the valve  30  with the cassette  10 , the valve body  112  is inserted through the housing  138  of the machine block  108 , so that the pressure channel  114  extends through the machine block  108 . The lock nut  122  is tightened up so that the protruding bulges  126  create a seal between the valve body  112  and the machine block  108 . By simply screwing the lock nut  122  onto the valve body  112 , a tight and reliable connection of the valve  30  with the machine block  108  is thus provided. 
     The machine block  108  with the valve  30  is pressed against the cassette  10 , whereby the shoulders  128  of the sealing cap  118  fit tightly with the edges of the liquid passage  28 . By pressing the machine block  108  against the disposable cassette  10 , several valves  30  can be simultaneously fitted into their corresponding liquid passages  28  at the desired points. 
     The dialysis liquid, for example, flows through the fluid passage  28  when the valve  30  is in the opened state. If excess pressure is applied via the pressure channel  114  in the direction of the arrow  142 , the deformable area  120  of the sealing cap  118  is deformed into the liquid passage  28  until the valve  30  is finally closed. The loading on the sealing cap  118  is reduced by the projection  130  of the sealing cap  118 , without the movement of the deformable area  120  being significantly impaired. The cover foil  14  of the cassette  10  is deformed together with the sealing cap  118  into the liquid passage  28 . 
     If the fluid passage  28  is to be opened again, the pressure channel  114  is vented and the deformable area  120  of the sealing cap  118  is relaxed. By applying a partial vacuum to the pressure channel  114 , the deformable area  120  is placed against the convex curvature of the pressure chamber  116  and correspondingly increases the cross-section of the fluid passage  28 . By simply applying or removing a pressurization to the pressure channel  114 , therefore, the flow rate through the fluid passage  28  can be controlled. 
     When the disposable cartridge is removed, the valve  30  can be removed or replaced simply by loosening lock nut  122 , e.g., for maintenance or in the event of malfunction. 
     The sealing cap  118  is a simple low-cost shaped part, which on account of its closed design can easily be cleaned and thus satisfies the hygiene requirements in dialysis, but which can also easily be replaced when necessary. 
     When the disposable cassette  10  is again compressed between the machine block  108  and the base body  12 , the valve  30  fits into the fluid passage  28  very well by pressing the shoulder  128  with the edge of the fluid passage  28 . On account of the elastic stretching of the deformable area  120  of the sealing cap  118 , there is a very good tolerance compensation both in the depth of the fluid passage  28  as well as in respect of lateral misalignment, without a significant additional expenditure of force. The deformable area  120  guarantees that only small forces are required to block the fluid passage  28 . 
     Other details regarding the valves  30  and their operation with disposable cartridges, such as the cassette  10  described above, are discussed in DE 100 46 651, which is incorporated by reference herein. 
     Referring again to  FIG. 1 , an arterial measuring chamber  32  and a venous measuring chamber  34  are furthermore recessed in the base body  12  of the cassette  10 . The basic design of these measuring chambers is shown in  FIG. 11 . Referring to  FIG. 11 , the flow direction of the fluid, i.e., of the blood through the chambers  32 ,  34 , is indicated by the arrows. The measuring chambers  32  and  34  have a widened passage section to be able to receive the sensors  36 . The contour of the measuring chambers  32 ,  34  corresponds to a diffuser nozzle geometry such as is shown in  FIG. 11 . A diffuser  38 , which runs out in a nozzle  40 , is arranged in the region of the inflow region of the fluid. The widened cross-section in the diffuser  38  is relatively rapid in comparison to the narrowed cross-section in the nozzle  40 . The sensors  36 , which are made in the form of multi-functional sensors, are arranged in the region of the arterial or venous measuring chamber  32 ,  34 . 
     More specifically, each of the sensors  36  for measuring selected parameters of the medical fluid passing in the arterial and venous measuring chambers  32 ,  34  is disposed on a measurement plate that has a peripheral seal along its outer edge and that is in contact with the flexible membrane (i.e., the foil  14 ). The measurement plate has an inlet that leads to the foil  14  so that a vacuum can be established between the measurement plate and the foil  14 . 
     Several sensors can be mounted on the measurement plate, and since the flexible membrane (i.e., the foil  14 ) can be brought in close contact with the measurement plate, the medical fluids are separated from the sensors on the measurement plate only by the foil  14 . Because of the peripheral seal disposed on the measurement plate, the foil  14  can be brought in close contact with the underside of the measurement plate by applying a vacuum, so that very close contact can be established between the sensors and the medical fluid in the measurement chamber. The contact surface of at least one of the sensors is preferably flush with the underside of the measurement plate, so that it is possible to establish direct measurement contact between the respective sensor and the flexible membrane. 
     Because of advances in miniaturization and integration technology of sensors, it is possible to arrange multiple sensors on an area a few square centimeters in size. Each respective sensor is preferably mounted in a recess in the measurement plate, with the measurement surface of the sensor being in flush contact with the underside of the measurement plate. The sensors are preferably securely glued to the measurement plate. 
     For example, a pressure sensor and a temperature sensor may be used. Pressure sensors have become available formed on individual semiconductor chips due to advances in integration of Microsystems, so that the chips carrying the sensor are only a few square millimeters in size. Because the sensor surface can be brought in direct contact with the foil  14 , it is possible to measure both positive and negative pressures. As a result, the thermal energy balance and the venous pressure in a dialysis machine can be measured with the pressure sensor and the temperature sensor. 
     In some implementations, the seal of the measurement plate is made of a rubber ring which is inserted into a groove in the measurement plate and projects slightly above the edge of the measurement plate. As soon as a vacuum is established between the membrane (i.e., the foil  14 ) and the measurement plate, the foil  14  is pressed tightly against the underside of the measurement plate by the ambient air pressure, and the seal guarantees that no additional air can flow into the area between the measurement plate and the foil  14 . 
     The measurement plate can be made of a metal disk into which the respective sensors are inserted. In some implementations, the metal disk is kept at a constant temperature by, for example, Peltier elements. This design permits a more accurate temperature measurement of the medical fluid. 
     Before performing the individual measurements, a vacuum is first applied to the inlet so that the film (i.e., the foil  14 ) is placed in close contact with the sensors. Then, the sensors are activated by a control unit (not shown), so that the respective measurements can begin. 
     The above-described sensor arrangement is described in greater detail in DE 198 37 667, which is incorporated by reference herein. 
     Referring again to  FIG. 1 , an arterial port  42  and a heparin port  44  are provided at the cassette, which are each connected via corresponding passages to the passage carrying the arterial blood in each case via phantom valves  46 . The phantom valves  46  are used in the cassette  10  in accordance with the invention instead of conventional open T-branches. In these phantom valves, the passage wall is not interrupted from the aspect of the main blood flow. Reference number  48  designates a venous port which likewise opens into a blood-carrying passage  28 , here in the venous part of the blood-carrying passages, via a phantom valve  46 . 
     As  FIG. 16  shows, and as discussed above, the fluid guide body (i.e., the base body  12 ) of the cassette  10  has a main fluid passage  28 , which is integrally worked into the base body  12  and is closed by a covering film (i.e., the foil  14 ), which is not shown in  FIG. 16 . 
     The fluid guide body (i.e., the base body  12 ) further has a secondary passage  144  that leads away from the rear side of the base body  12 , which is remote from the open side of the main passage  28 , onto the opposite front side of the base body  12  and opens there into the main passage  28 . As  FIG. 17  shows, the secondary passage  144  passes through a base  146  of the main passage  28 . The secondary passage  144  extends into the main passage  28  in the form of a volcano-like funnel  148  whose height corresponds to the depth of the main passage  28  so that an orifice  150  of the secondary passage  144  is arranged vertically coincident with the rims of the main passage  28 . 
     The secondary passage  144  is positioned symmetrically in the center of the main passage  28  and extends perpendicularly to the longitudinal direction of the main passage  28 . The planar designed orifice  150  is in the plane which is set up by the rims of the main passage  28 . 
     As  FIG. 16  shows, the funnel  148  has a streamlined cross-section. In more precise terms, the outside of the wall of the secondary passage  144  in the main passage  28  is formed in streamlined manner, with the longitudinal axis of the streamlined shape corresponding to the longitudinal axis of the main passage  28 . Vortexes, turbulences and an increased flow resistance are thereby avoided at the secondary passage  144 . The medical fluid flowing through the main passage  28  can flow past the secondary passage  144  in laminar fashion. 
     As  FIG. 16  shows, the contours of the main passage  28  are also formed extending in streamlined fashion around the secondary passage  144 . The side walls of the main passage  28  opposite the funnel  148  bulge in streamlined fashion around the funnel  148  so that the fluid flow forking around the funnel  148  finds approximately the same flow cross-section and can flow past the funnel  148  without speed changes. 
     To be able to close the open side of the secondary passage  144  and simultaneously the orifice  150  of the secondary passage  144 , the covering film (i.e., the foil  14 ), which can be welded or connected in another way to the base body  12 , lies on the base body  12 . To seal the main passage  28 , the foil  14  can be welded to the base body  12  along the rims of the main passage  28 . The sealing can, however, also be effected by pressing the foil  14  along the rims of the main passage  28  by a valve plunger  152 . 
     The valve plunger  152  has a continuous, planar plunger surface  154  that is formed by an elastic (e.g., elastomer) machine membrane. Due to the vertically coincident arrangement of the orifice  150  with the rims of the main passage  28 , the secondary passage  144  can be closed without stretching of the foil  14 , if the foil  14  is pressed onto the base body  12 . The orifice  150  is formed for this purpose as a planar valve seat  156 , which is in the plane set up by the rims of the main passage  28  and forms the front end of the funnel  148 . 
       FIG. 17  shows the closed state of the secondary passage  144 . The plunger surface  154  is pressed onto the base body  12 . Additional pressure can be applied by an actuating part  158  in the region of the orifice  150  of the secondary passage  144  in order to achieve a reliable sealing of the secondary passage  144 . 
     To open the secondary passage  144 , the actuating part  158 , which is connected to the plunger surface  154  in the region of the secondary passage orifice  150 , is moved away from the base body  12 . The plunger surface  154  is thereby raised from the orifice  150  of the secondary passage  144  in the region thereof. As  FIG. 18  shows, the plunger surface  154  thereby deforms, which is allowed by the design of the same as an elastic membrane. 
     The foil  14  also lifts off the orifice  150  of the secondary passage  144  due to the raising of the plunger surface  154 . The pressure of the flow in the main passage  28  presses the foil  14  away from the orifice  150 . Optionally, this can also be supported actively by the interposition of a vacuum between the plunger surface  154  and the foil  14 , which is helpful in particular when a sample should be sucked from the fluid flow in the main passage  28  through the secondary passage  144 . 
     When the actuating part  158  lifts, the foil  14  stretches elastically. The deformation is here very low, however. It is in particular not plastic so that a formation of creases in the subsequent re-closing of the orifice  150  is prevented. As  FIG. 18  shows, the secondary passage  144  is in flow communication with the main passage  28  in the raised state of the foil  14 . 
     Other details regarding the phantom valves  46  are described in DE 100 53 441, which is incorporated by reference herein. 
     Referring again to  FIG. 1 , reference numbers  50  designate two pump chambers which serve to pump the blood. The design of the pump chambers  50  is shown in detail in  FIG. 12 . The pump chambers  50 , which are activated via membrane pumps provided at the machine side (i.e., in the machine block  108 ), have substantially tangential inlets and outlets for a uniform throughflow of the total chamber, as shown in  FIG. 1 . The shape of the pump chambers  50  is pre-determined by the correspondingly shaped base body  12  of the cassette  10  and can be approximately described as a spherical section. At the periphery, the base body  12  of the cassette  10  has a raised edge  52  around the pumping chambers  50  which serves as a stop bead. In addition, as shown in  FIG. 12 , the peripheral edge of the spherical section is set somewhat lower so that in the pressing-out phase, that is in the phase in which the cover foil  14  is moved toward the base body  12  of the cassette  10 , a flushing edge or flushing passage  54  is formed. The flushing edge or flushing passage  54  is advantageously made in that the spherical pump surface at the machine side (i.e., the spherical pump surface in the machine block  108 ), which is not shown in  FIG. 12 , has a smaller radius than the radius of the pump chamber  50  at the cassette side. The radius difference Δ r  is shown in  FIG. 12 . A wide flushing edge or flushing passage  54  is hereby formed. This flushing edge or flushing passage  54  is an annular space for the pumped blood in the extreme pressing-out position. This free annular space, on the one hand, avoids blood damage by being trapped between the foil surface and the injection molded surface (i.e., the base body  12 ) at the end of the pressing-out phase and, on the other hand, blood damage due to high flow speeds and shearing strains which would result at the start of the start-up phase if no free annular space were provided. 
     In the upper region of the cassette in the installed state, a venting chamber  56  is formed which is shown again in  FIG. 10  in a sectional representation. A venting membrane  58  is arranged in this venting chamber via which correspondingly collected air can be separated since it is made as a partially permeable membrane which preferably has hydrophobic or oleophobic properties. Expanded or sintered polytetrafluoroethylene can preferably be used as the venting membrane. A venting stub  60  is arranged above the venting membrane  58  and its cooperation with the fluid treatment machine (not shown in more detail here) will be described later. 
     Bubbles are trapped in the venting chamber  56  by a slowing down of the blood flow. As shown in  FIG. 10 , a rotation flow is generated for effective air separation with minimum area requirements on the cassette  10 . In this process, the generation of the final rotation flow is only created in the operating state of the cassette  10  in the fluid treatment machine  100 . The cover foil  14  of the cassette  10  is pulled into the fluid treatment machine  100  by a corresponding vacuum coupling system of which only one vacuum suction passage  102  is shown in  FIG. 10 . An almost circular cross-section of the venting chamber  56  is thereby formed. The rotation flow of the blood is supported in that the passage opening into the venting chamber  56  also runs—together with its cover foil  14 —slightly into the machine side so that an almost tangential inflow within the chamber is achieved. An effective suction can take place at the machine side at the venting stub  60 . A low filling volume results overall here in the venting chamber  56  as a result of the construction. 
     The basic design of the passages  28  can be explained with reference to  FIG. 13 . Generally, care is taken in the passage design of the passages  28  that a smooth foil surface and smooth passage surfaces are provided. Steps, dead spaces, turbulence and impact surfaces are avoided. Low changes in direction and speed are aimed for. Separations of flow are largely avoided. All passages  28  and also chambers  50  have an edge bead  52  which accompanies the passages and faces the cover foil  14 . On insertion of the cassette  10  into the fluid treatment machine  100 , the foil  14  is pressed onto the edge bead  52  such that all passages  28  are sealed against the environment. At the rear of the cassette, i.e., at the outer side of the passage wall, webs  62  are formed which accompany the passages and via which the rear pressing force is guided to the edge beads  52  in order thus to achieve a uniform linear distribution of force. 
     It can also be explained with reference to  FIG. 13  that the base body  12  of the cassette  10  is welded to the cover foil  14  at the outer edge  64 . 
     As shown in  FIG. 1 , the cassette  10  has a recessed centering fork  66  as a positioning aid which receives a centering pin on the machine side on insertion. Stop noses  68  are furthermore molded on which contact against corresponding machine surfaces on insertion. The cassette  10  is thereby guided in height and angle. When pressing the cassette  10  into the fluid treatment machine  100 , a latching with the fluid treatment machine takes place at a snap element not shown in more detail here such that the cassette  10  is fixed in an aligned manner. The cassette  10  has a molded handle  70  at the side disposed opposite the centering fork  66  for simplified handling. 
     The arterial injection septum  16  or the venous injection septum  20  are made in the embodiment shown here, in contrast to a conventional injection position, such that their base body is formed by the base body  12  of the cassette itself so that here only the elastic septum is fixed by a snap ring (not shown in detail here). The septum consists of an elastomer in the embodiment shown here. 
       FIG. 4  shows a modified embodiment of the cassette in accordance with  FIG. 1 . This cassette  10  shown in  FIG. 4  also serves standard hemodialysis and largely shows an identical design to the cassette  10  in accordance with  FIG. 1 . To this extent, a detailed description of the already described components of the cassette  10  is superfluous. However, instead of the handle  70  in the embodiment in accordance with  FIG. 1 , a dialyzer  72  is integrated in the side of the cassette  10 , with the lines  18  and  22  to the dialyzer opening directly into the dialyzer. The dialysate connections at the dialyzer, which can have a conventional design, are designated by  74  and  76 . 
     A cassette  10  is shown in  FIG. 2  which is designed as an online hemodiafiltration cassette. It becomes clear from the arrangement of the different elements that the base body  12  of the cassette  10  starts from that base body of a cassette such as has already been described in  FIG. 1  with reference to the embodiment for standard hemodialysis. All elements which are known from this configuration can be found in the same manner in the embodiment variant in accordance with  FIG. 2  for online hemodiafiltration. To this extent, they will not be additionally explained again. However, those parts will be explained which are necessary for the operation of the hemodiafiltration cassette. This includes the substituate connector  80  via which the substituate fluid is fed into the passages  28 . Substituate passage valves  82  are provided at the passages and the passages  28  can be closed at the appropriate positions via these valves  82 . The substituate fluid is guided into two parallel pump chambers  84 , which form substituate pump chambers, via the passages  28 . The substituate pump chambers  84  substantially correspond to the pump chambers for the blood  50  as they have previously already been described in detail. Starting from the passage  28 , the substituate fluid is guided through a substituate tunnel  86  which is disposed on the opposite side of the base body  12  of the cassette  10 . The substituate tunnel  26  is suitably closed at the rear side, e.g., by a welded foil. The substituate fluid  86  can be led into the passage  28  carrying the blood via a port for pre-dilution  88  or via a port for post-dilution  90 . The ports are again made as phantom valves of the type described above. 
     The substituate region substantially formed by the substituate pump chambers  84  is surrounded by a substituate weld rim  92  to which the cover foil  14  is sealingly welded so that this region of the cassette  10  processing substituate is separated from the blood-carrying region. 
     In  FIG. 5 , a modification of the embodiment variant in accordance with  FIG. 2  is shown. Here, too, in a similar manner to the embodiment variant in accordance with  FIG. 4 , a dialyzer  72  is integrated directly into the cassette  10 . 
     In  FIG. 3 , a cassette  10  for acute treatment is shown as a further integrated embodiment of the cassette. It is designed identically to the embodiment variant in accordance with  FIG. 1  in the region of the blood treatment part. With respect to the substituate part, it partly corresponds to the embodiment in accordance with  FIG. 2 , with here only one substituate pump chamber  84  being provided which is fed by the substituate fluid led in via the substituate connector  80  and the passage  28 . In a similar manner as to the embodiment variant in accordance with  FIG. 2 , substituate passage valves  82  are provided before and after the substituate pump chamber  84 . The further pump chamber, which is designated by  94  in the present embodiment variant for acute treatment, is connected to a filtrate outlet  96  via a passage  28  and opens into a filtrate connection  98  which is connected to the dialyzer not shown in any more detail here. 
     In  FIG. 6 , in turn, a modified embodiment variant of the cassette  10  in accordance with  FIG. 3  is shown. Here, a dialyzer  72  is in turn integrated instead of the handle, with here a connection  99  being provided between the dialyzer  72  and the passage  28  which carries the filtrate and which leads to the filtrate pump chamber  94 . 
     In  FIG. 7 , an embodiment of the fluid treatment machine  100  is shown without an inserted cassette  10 . This fluid treatment machine  100  is designed such that all aforesaid cassettes can be inserted, with a basic extracorporeal blood circuit, i.e. a standard dialysis using an external dialyzer, being carried out by a corresponding program selection, for example on insertion of the cassette in accordance with the embodiment variant in accordance with  FIG. 1 . When a cassette  10  in accordance with the embodiment of  FIG. 2  is used, online hemodiafiltration or an online hemofiltration variant is, for example realized by use of the components required for this purpose with, optionally, automatic connections (not shown) to the fluid circuit of the basic unit. Highly integrated variants with an integrated dialyzer and an automatic dialyzer connection are also possible such as are shown by way of the cassette in the embodiment variants in accordance with  FIGS. 4 and 5 . Acute dialysis treatment is possible when a cassette  10  is used in accordance with the embodiment of  FIG. 3 . 
     The fluid treatment machine  100  substantially consists of a frame  104  which surrounds and/or includes or receives the most important components. A door  106  is fitted to the frame  104 , on the one hand, and the machine block  108  is guided in the frame, on the other hand. All forces occurring between the door  106  and the interior of the unit are absorbed by means of the frame  104 , namely the door hinge, door latch, pressing actuator system and the rear wall. The frame  104  furthermore contains the door latch  110 . The cassette  10  is received between the door  106  and the machine block  108 , as shown in the  FIGS. 8 and 9 , and is sealed by pressing. Sensor system elements are included in the cassette region of the machine and they detect whether a cassette is correctly positioned in the fluid treatment machine. These, or further sensor system elements, can be designed such that they are suitable for recognizing the cassette type (e.g. with the aid of a barcode on the cassette). 
     The important elements for the control and monitoring of the extracorporeal blood circuit, such as pumps, valves, the sensor system, etc., are contained in the machine block  108 . This machine block  108  establishes the most important interface to the cassette  10 . The cassette surface is coupled to the unit here and the sealing of the cassette  10 , and thus the fixing of the flow paths, takes place by this. The machine block  108  is guided movably in the frame and fixes the cassette  10 , as already described above, until the door  106  is closed. 
     Hydraulic piston pumps are contained in the fluid treatment machine which are not shown in detail in  FIGS. 7 ,  8  and  9  here. They are, on the one hand, blood pumps or optional substituate feed pumps or ultrafiltrate pumps. They are hydraulically connected to the pump chambers (i.e., the blood pump chambers) C, D, and, in some cases, they are hydraulically connected to the optional filtrate pump chambers and/or the optional substituate pump chambers E, F. Furthermore, compressors for the generation of the required pneumatic pressure (overpressure or vacuum) not shown in more detail here are contained in the fluid treatment machine  100 . The fluid treatment machine  100  furthermore has—in a manner not shown in more detail—a pneumatic buffer container for the compensation of pressure fluctuations, a main electronics box, a heparin injection pump and a blood pressure monitor module. 
     A pressing actuator system on the rear wall of the frame  104 , likewise not shown in more detail, must be emphasized here. An inflatable air cushion is integrated here which can move the whole machine block  108 , which is movably supported in the frame  104 , and press it against the closed door  106 . 
     Furthermore, instead of individual air-carrying tubes, an air distributor plate is provided at the machine block  108  which contains main connections for the pneumatics and which guides compressed air and vacuum to the valves and actuators via passages integrated there without any substantial tubing, with them simultaneously terminating the machine block with respect to the interior of the fluid treatment machine  100 . 
     Optional modules can be provided in the fluid treatment machine  100  for the carrying out of the online hemodiafiltration. For instance, an online feed port for the automatic coupling of a cassette  10  to a dialysate circuit or an online flushing port for the return of flushing solution can be contained here. 
     The door  106  must be open for the insertion of the cassette  10 . The cassette  10  is inserted and, after positioning of the centering fork  66 , is fixed to the surface of the machine block by means of a snap hook. 
     The side of the machine block  108  facing the cassette  10  is lined with a soft elastomer mat  160  (shown in  FIG. 19 ), which seals the cassette  10  after pressing has taken place. 
     Referring to  FIG. 19 , during use, the elastic matt  160  is arranged between the fluid treatment machine (i.e., the machine block  108 ), of which no detail is shown here, and the cassette  10 . On the so-called machine side, namely on the surface which, when assembled, faces the fluid treatment machine  100 , matt channels  162  and connection channels  164  are formed. Furthermore, a recess  166  is arranged in the elastic matt  160 , into which in the assembled condition a machine-mounted valve, for example, engages and establishes a seal all around. It is easy to see that this machine-mounted valve interrupts the respective matt channel  162  which happens to join the recess  166 . In order to still make an air extraction possible, a connection channel  164  has been provided which connects the two interrupted branches of the matt channel  162  and connects them in turn with a further, parallel matt channel  162 . The structure shown here is, of course, only an example and can be changed in any way. While the channel structures are provided on the machine side of the elastic matt  160 , the disposable side, namely the side facing the cassette, is executed as a smooth, i.e., flat surface. 
     By referring to the sectional views of  FIGS. 20 to 22 , the structure of the individual channels can be explained in more detail. The section A-A′ as per  FIG. 19  is shown in  FIG. 20  where a matt channel  162  becomes visible which, with the elastic matt  160  used here having a thickness of 4 mm, has a depth of 3 mm and a width of 2 mm. In the remaining matt material below the channel  162 , which has a thickness of 1 mm, a slit  168  is placed which takes on a type of valve function. When a vacuum is applied, the two areas of the elastic matt  160  adjacent to the slit  168  will open and enable the extraction of air gas. In an idle state or when an equilibrium is obtained, the two adjacent areas return to their original position and close the opening. In order to enhance this return effect, areas between the slits  168  are provided in the matt channel  162 , which on the one hand do not have a slit and, on the other hand, are less deeply recessed in the area of matt channel  162 . Referring to  FIG. 21 , a corresponding area can be seen in section B-B′, which shows that, while the matt channel  162  in this area has the same width of 2 mm, it only has a depth of 1 mm. 
     Referring to  FIG. 22 , a connection channel  164  is shown in the sectional view of C-C′, where said channel is narrower and not as deep as the matt channel  162 , which can be seen clearly in this view. In this case, both the width of the connection channel  164  and the depth are one millimeter each. 
     With the elastic matt  160 , it is guaranteed that the interior space of the fluid treatment machine, in its idle state, is protected by the self-closing feature of slits  168 . At the same time, an even air extraction is achieved between the fluid treatment machine and the cassette across its entire surface because parallel extraction takes place via numerous slits  168 . Thus, a minor blockage may not cause any detrimental effects for other areas. 
     With a thin matt  160 , as it has been presented in the embodiment for example, the opening effect of the slits can be utilized by applying a vacuum. 
     Since the elastic matt  160  is exchangeable, it can be replaced easily after contamination or a fault. It is especially advantageous that no structured shapes are required for the fixed components on the machine. On the side of the elastic matt  160  facing the machine, open structures can be formed so that no sub-surface tunnels or other closed structures are required. On the other hand, the side of the elastic matt  160  facing the cassette is largely formed as a smooth, closed surface which can be cleaned easily for example. 
     Other details regarding the elastic matt  160  are described in DE 101 57 924.1, which is incorporated by reference herein. 
     Referring again to  FIG. 7 , after closing and locking the door  106 , pressing takes place by inflating the aforesaid air cushion. On opening and removing the cassette  10 , the pressing is cancelled again by letting out the air in the air cushion before opening the door  106 . 
     To achieve a sufficient pressing and to prevent a tilting of the machine block  108  by a non-uniform introduction of force, the air cushion has approximately the size of the machine block  108  or of the cassette  10 . 
     Since, however, further components, for example, control valves or the air distributor plate with the control valves, are now disposed between the air cushion and the machine block, the force transmission takes place by means of spacer bolts. 
     The traction between the door  106 , the frame  104  and the rear wall takes place by the door hinge, the latch  110  and connection bolts, not shown in any more detail here, between the frame and the rear wall. 
     As already mentioned, a constant pressing of the cassette  10  must take place for a proper operation. For this purpose, it is necessary for the door  106  to be locked during the treatment. This locking takes place via two latching bolts (not shown in any more detail here) at the upper right hand and lower right hand door region, with these moving into two corresponding bores inside the door  106  on actuation, which takes place automatically. The moving in and out takes place pneumatically. An erroneous opening of the door  106  on a failure of the pneumatics is precluded by the bolts moved into the door and by the lateral forces occurring by the pressure load of the door. To check whether the latching has taken place, Hall proximity sensors can be integrated which detect the movement of the bolts. In addition, this signal can be linked to information on the door position which can be picked up by a separate sensor. In addition, the latching bolt not shown in any more detail here can have a latch connection. This latch connection consists of a spring-loaded latch ball on the door side which latches into a corresponding arch of the latch bolt and can hold the door in the corresponding position. An introduction slope is provided for the simplified latching. To open the door from the latch position, the latch ball present here is drawn back by means of a mechanical system. 
     On the side of the fluid treatment machine  100 , the blood circuit substantially consists of at least one hydraulically controlled membrane pump having two independent pump chambers C and D which can be used as a highly precise flow pump or as a volumetric metering unit, a row of valves M, O and clamps N for the control of the flow path, a highly integrated sensor system G, H required for monitoring and control, an active air extractor, i.e., an air separation chamber I with a connected cassette venting A, of the blood circuit (air-free circuit) and a door  106  to fix the cassette  10 . 
     The fluid treatment machine  100  respectively comprises a pneumatic system for the overpressure and a pneumatic system for the underpressure. The underpressure serves, for example, to apply an underpressure between the foil  14  of the cassette  10  and the unit side to prevent a passage restriction on the plastic deformation of the foil, to raise the foil at feed positions and thus to be able to keep the access free, to avoid air compliance in the pump devices and to be able to ensure an air-free coupling between the sensor and the foil at specific sensor positions. The air suction requires openings in the unit side and a suction unit, i.e., a vacuum pump, connected to it, wherein the vacuum distribution should be ensured as uniformly and as reliably as possible over the whole surface. In the idling state, the openings should be at least largely closed to permit a good cleaning here. In operation, however, a problem-free air suction should be possible. This problem is solved by the elastomer mat of the type described above. 
     In the cassette  10 , no passage seals are contained except for the edge region and some safety weld connections. The sealing of all flow paths and passages must therefore take place by pressing. For this purpose, the cassette has sealing beads  52  on the passage rims which have already been described above and which are sealable on the pressing of the disposables between the machine block  108  and the door  106  by pressing into the elastic mat. 
     The air distributor plate not shown in any more detail here is located on the rear side of the machine block  108  and is connected to the, for example, two membrane pumps of the pneumatic system, namely the overpressure pump and the underpressure pump. The air distributor plate is sealed with respect to the rear side of the machine block by a sealing mat and permits the compressed air and vacuum feed via integrated passage structures so that every valve does not need its own tubing. A plurality of circuits are present on the air distributor plate, namely a vacuum circuit, a compressed air circuit which is directly connected to the compressor for the supply of components which always need compressed air, a compressed air circuit for the protection of sensitive components which may only be charged with compressed air under certain states, with it also being separable from the compressor by an on/off valve and an exhaust circuit. 
     By integration of a plurality of control valves on the air distributor plate, the electrical supply can also be collected via a small control board. Since a plurality of valves are only needed with specific options, a modular retrofitting capability must be ensured. 
     The sensor system and the pump connections are guided through the plate through apertures and cut-outs. 
     Sensors which are collected in integrated sensor modules in the present fluid treatment machine  100  are required for the monitoring and control of the extracorporeal blood circuit. Two respective modules work together as a pair. One module is accommodated in the door  106  and the counter-piece in the machine block  108 . Both the arterial branch should be monitored by the arterial measuring chamber G and the venous branch by the venous measuring chamber H. The integrated measurement sensor system is described in detail in the German patent applications DE 198 37 667 A and DE 101 43 137 of the same patent applicant. The sensors together have the following properties or provide the following possibilities: 
     measurement and monitoring of the blood volume; 
     measurement of the hematocrit; 
     measurement and monitoring of the thermal energy balance; 
     measurement and monitoring of the body temperature; 
     measurement of the conditions of the fistula (with circulation); 
     air detection; 
     fistula pressure measurement. 
     A multi-sensor module is usually fitted with an ultrasonic sensor for volume monitoring, measurement of the hematocrit and the air detection, with a temperature sensor for the automatic access analysis, body temperature monitoring and thermal energy balance, with a pressure sensor for the pressure monitoring and with an optical sensor for the automatic detection of blood. 
     The valves M and the pump valves O have a similar design to those valves described above. 
     In addition to the aforesaid valves which are shown in  FIG. 7 , so-called phantom valves, which are not drawn in any more detail in this  FIG. 7 , are additionally present. The design and function of the phantom valves are similar to the design and function of the phantom valves discussed above. 
     Reference letter N designates safety clamps which serve to achieve a safe state during an alarm in the extracorporeal blood circuit, with them interrupting the patient line and thus any blood flow from or to the patient. To avoid unwanted compliance effects, and since the system is designed for a flow reversal, this safety function must be ensured both on the arterial side and on the venous side so that two blocking clamps N are used which can be mechanically coupled. 
     The blocking clamps should be effective as close to the patient as possible in order to be able to minimize any interference and to satisfy high safety demands. For this reason, tube clamps are used which act directly on the patient tubes. 
     A possible embodiment, such as is provided here, consists of the clamping of the tubes against a clamping rail on the inner side of the door by means of a reclosable pneumatically opened clamping slide. Such a system is passively spring-closing, namely without pressure and without current and so is also advantageous in the case of a failure under safety aspects. 
     In  FIG. 8 , a fluid treatment machine  100  is shown corresponding to  FIG. 7  with an inserted cassette  10  corresponding to  FIG. 2 . In  FIG. 9 , in contrast, a fluid treatment machine  100  is shown with a cassette  10  corresponding to the embodiment variant in accordance with  FIG. 5 , with the dialyzer in the cassette here having an automatic dialysate connection K and L to the fluid treatment machine  100 . 
     The new apparatus shown here follows a strictly modular approach while achieving a high flexibility and deployment possibility also with respect to future deployment possibilities and options. The integrated blood module permits the carrying out of the whole spectrum of the blood treatment procedures, namely standard hemodialysis, online hemodiafiltration, online hemofiltration and also acute treatment. 
     It must be pointed out with respect to the acute treatment that the machines serving the acute treatment, i.e., the acute dialysis or acute filtration, have to have a simple design in order to be able to be transported corresponding easily and to be able to work without a complex supply structure (e.g. water connection). In this system, therefore, work is carried out practically without exception with bags with premanufactured solutions. Using the embodiments shown in  FIGS. 3 to 6 , acute hemofiltration can then be carried out easily in which the substituate is supplied from a bag and filtrate is removed from the filter into an empty bag with the pumps shown. Except for the connection of the bags, no further measure is necessary in this case. It would naturally nevertheless be possible to additionally make a dialysis possible with a corresponding effort. Furthermore, the substituate pump could alternatively be used as a dialysate supply pump if the connections inside the cassette were changed accordingly. Then dialysis fluid filled into bags could be supplied in balanced form to the filter via the membrane pump, while fluid is led out in a controlled manner via the filtrate pump. No further components would also be necessary for the fluid control in such a machine. 
     Each of these types of treatment can take place both in two-needle and in single-needle mode. Reference is made here to the German patent DE 100 42 324 C1 with respect to the description of the two-needle or single-needle mode. 
     Other embodiments are within the scope of the following claims.