Abstract:
The present invention relates to a device and method for conveying fluids into the treatment unit of a medical treatment apparatus. The device and method according to the present invention are based on the fact that the fluid with which the treatment unit is supplied, circulates in a fluid circuit including the treatment unit. To balance fresh and used fluid fed to the treatment unit or conveyed from the treatment unit, a balancing unit with a balancing chamber is used, which can be incorporated into the fluid circuit including the treatment unit. It is thus possible to supply the fluid circuit continuously with fresh fluid or to carry away used fluid continuously from the fluid circuit. The supply and discharge of fresh and used fluid can take place at a different flow rate from the flow rate at which the fluid circulates in the fluid circuit via the treatment unit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a 371 national phase application of PCT/EP2011/002915 filed Jun. 14, 2011, which claims priority from German Patent Application No. 10 2010 023 635.7, filed Jun. 14, 2010. 
     FIELD OF INVENTION 
     The present invention relates to a device and a method for conveying fluids into the treatment unit of a medical treatment apparatus, in particular into the dialyzer of a dialysis apparatus. Moreover, the present invention relates to an extracorporeal blood treatment apparatus, in particular a dialysis apparatus, which comprises a device for conveying fluids into the treatment unit, in particular the dialyzer, of the blood treatment apparatus, in particular dialysis apparatus. 
     BACKGROUND OF INVENTION 
     Various kinds of treatment apparatuses are known that comprise a treatment unit to be supplied with a fluid. The known treatment apparatuses include, for example, blood treatment apparatuses. During the blood treatment, the patient&#39;s blood flows in an extracorporeal blood circuit through the blood treatment unit. In the case of apparatuses for hemodialysis, hemofiltration and hemodiafiltration, the blood treatment unit is a dialyzer or filter, which is divided by a semi-permeable membrane into a blood chamber and a dialyzing fluid chamber. During the dialysis treatment, the blood flows in an extracorporeal blood circuit through the blood chamber, whilst the dialyzing fluid flows in a dialyzing fluid circuit through the dialyzing fluid chamber of the dialyzer. 
     On account of the large exchange quantities, there is a need with the known methods and apparatuses for blood treatment for an exact balancing of the fluid removed from the patient and the fluid fed to the patient during the overall treatment time. Gravimetric and volumetric balancing devices belong to the prior art. 
     A hemodiafiltration apparatus with volumetric balancing is known for example from DE 26 34 238 A1. The balancing device of the known hemodiafiltration apparatus comprises a volume-rigid hollow body, which is divided by a mobile partition wall into two chambers. Each chamber comprises an inlet and an outlet, on which supply lines and discharge lines for fresh and, respectively, used dialyzing fluid are disposed, a shut-off element being incorporated in each line. Moreover, provision is made for pumps for conveying the fresh and used dialyzing fluid as well as a control unit, which permits a mutual filling of the two chambers. 
     In order to be able to ensure a continuous flow of dialyzing fluid through the dialyzing fluid chamber of the dialyzer, two balancing chamber are connected in parallel in practice, said balancing chambers supplying the dialyzer alternately with fresh dialyzing fluid. A balancing unit with two balancing chambers is known for example from DE 28 38 414. 
     During a dialysis treatment, the dialyzing fluid flow typically amounts to 500 ml/min, but can amount to up to 1000 ml/min depending on the given treatment situation. In the case of a dialysis period of 4 hours, this means a dialyzing fluid requirement which typically amounts to between 120 L, but depending on the given treatment situation can also be over 200 L. 
     On account of the large fluid requirement in dialysis, the preparation of the dialysate from concentrates and pure water (RO water) in the machine has become established, in order to avoid the storage of fairly large quantities of solutions. The RO water is made available centrally in the clinic and distributed via lines to the dialysis machines in the dialysis stations. 
     In the treatment of an acute renal insufficiency, such as can occur for example after accidents, which calls for intensive-care support for the patient, a RO water connection is generally not present. The dialyzing fluid is then made available to the machine by means of containers, for example canisters or bags. 
     In order to keep the handling costs down, an attempt is made, especially in the case of intensive-care support for acute renal insufficiency, to reduce the requirement for dialyzing fluid. This is achieved by the fact that the dialyzing fluid is recirculated via the dialyzer for a certain length of time. The dialysate requirement can thus be reduced to values which lie below 100 ml/min. 
     A blood treatment apparatus with a recirculation circuit is known for example from U.S. Pat. No. 5,685,988. The recirculation of dialyzing fluid should however only be used for the determination of blood treatment parameters. 
     The problem underlying the present invention is to provide a device for conveying fluids into the treatment unit of a medical treatment apparatus, in particular into the dialyzer of a dialysis apparatus, with which device the requirement for dialyzing fluid can be reduced. A further problem of the present invention is to provide a method for conveying fluids into the blood treatment unit of a medical treatment apparatus, said method permitting a reduction in the requirement for dialyzing fluid. The problem of the present invention is also to provide an extracorporeal blood treatment apparatus with such a device for conveying fluids. 
     The device according to the present invention and the method according to the present invention are based on the fact that the fluid with which the treatment unit is supplied circulates in a fluid circuit which includes the treatment unit. In order to balance fresh and used fluid which is fed to the treatment unit or carried away from the treatment unit, use is made of a balancing unit which in principle can comprise one or two balancing chambers. 
     The device according to the present invention and the method according to the present invention are characterised in that the balancing chamber of the balancing unit, or the two balancing chambers of the balancing unit, can be incorporated into the fluid circuit including the treatment unit. It is thus possible to supply fresh fluid continuously to the fluid circuit and to discharge used fluid continuously from the fluid circuit. The supply and discharge of fresh and used fluid can take place at a flow rate different from the flow rate at which the fluid circulates via the treatment unit in the fluid circuit. Consequently, there becomes established in the fluid circuit a “fluid” which, depending on the ratio of the flow rates, lies in concentration between a “fresh fluid” and a “used fluid”. Independently of the supply and discharge of fresh or used fluid, fluid (ultrafiltrate) can also be removed from the fluid circuit including the blood treatment unit, in particular the dialyzer. 
     In a preferred embodiment of the present invention, the flow rate at which the fluid circulates via the treatment unit in the fluid circuit is greater than the flow rate at which fluid is fed to and discharged from the fluid circuit. 
     The device according to the present invention comprises a bypass, which connects the discharge line leading from the balancing chamber to the treatment unit to the supply line leading from the treatment unit to the balancing chamber. The bypass permits not only a continuous supply of fresh fluid into the fluid circuit including the treatment unit, but also the maintenance of a fluid flow through the blood treatment unit when the balancing chamber of the balancing unit is being filled with fresh fluid, thereby displacing used fluid. If a balancing chamber with two alternately operating balancing chambers is used, this advantage is admittedly not brought to bear. A particularly preferred embodiment of the present invention thus provides a balancing unit with only one balancing chamber. In this particularly preferred embodiment, the bypass ensures that the fluid flow through the blood treatment unit is not interrupted during the switch-over of the balancing chambers. A simplified design of the balancing unit thus results. 
     The means for conveying fluid into or out of the balancing chamber and the means for interrupting the supply of fluid into the balancing chamber or the discharge of fluid out of the balancing chamber can be designed differently. The known occluding pumps, into which hose lines can be inserted, are preferably used for conveying fluid. For the interruption of the supply or discharge of fluid, use is preferably made of the known electromagnetically or pneumatically operated shut-off elements, which are disposed in the lines. A control unit controls the means for conveying fluid and the means for interrupting the supply or discharge of fluid. Since occluding pumps pinch off the hose line in the standstill state, the occluding pumps can also replace shut-off elements. 
     In a particularly preferred embodiment, the means for conveying fluid comprises a first pump, which is disposed in the supply line leading from the fluid source to the balancing chamber. Moreover, the conveying means comprises two further pumps, which are disposed in the discharge line leading from the balancing chamber to the blood treatment unit. Of these two pumps, one is disposed in the section of this discharge line which leads to the point at which one connection of the bypass is connected to the discharge line, whilst the other pump is disposed in the section of this discharge line which leads away from the connection point of the bypass. The flow rates of these two pumps in the discharge line determine the flow rate at which fresh fluid is fed to the fluid circuit and used fluid is carried away from the fluid circuit. 
     In a particularly preferred embodiment, the means for interrupting the supply and/or discharge of fluid comprise a first shut-off element, which is disposed in the first supply line leading from the fluid source to the balancing chamber, a second shut-off element, which is disposed in the second discharge line leading away from the balancing chamber and leading to the drain, a third shut-off element, which is disposed in the second discharge line leading away from the balancing chamber and leading to the blood treatment unit, and a fourth shut-off element, which is disposed in the second supply line leading from the treatment unit to the balancing chamber. All the shut-off elements are controlled by the control unit. 
     In the particularly preferred embodiment, the control unit is designed such that the first and second shut-off elements are opened and the third and fourth shut-off elements are closed in a first work step of a first work cycle of successive work cycles, the first and third pumps being in operation. In the first work step, the balancing chamber is filled with fresh fluid, used fluid thereby being displaced. During the filling procedure of the balancing chambers, the fluid flow through the treatment unit is not interrupted. The first work step is followed by a second work step, in which the first and second shut-off elements are closed and the third and fourth shut-off elements are opened, the second and third pumps being in operation. In the second work step, the fluid circulates in the fluid circuit including the blood treatment unit. Fresh fluid can also be, but does not have to be, fed to the fluid circuit or carried away from the fluid circuit. 
     A further preferred embodiment provides for the integration of a further shut-off element in the bypass. This shut-off element serves for the better filling and venting of the system before the treatment is carried out. On the other hand, the circulation in the fluid circuit can also be interrupted with the shut-off element in the bypass. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples of embodiments of the present invention are explained below in detail by reference to the drawings. 
       In the figures: 
         FIG. 1  shows a hemodialysis apparatus with a device for supplying the dialyzer of the dialysis apparatus with dialyzing fluid in a very simplified schematic representation, wherein the first work step of a work cycle is represented, 
         FIG. 2  shows the hemodialysis apparatus of  FIG. 2 , wherein the second work step of the work cycle is represented, 
         FIG. 3  shows a second example of embodiment of the hemodialysis apparatus with the device for supplying the dialyzer with dialyzing fluid in a very simplified schematic representation, 
         FIG. 4  shows an alternative embodiment of the hemodialysis apparatus of  FIG. 3 , 
         FIG. 5  shows a further example of embodiment of the dialysis apparatus in a very simplified schematic representation and 
         FIG. 6  shows an alternative embodiment of the dialysis apparatus of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is described below using the example of a blood treatment apparatus which comprises a dialyzer as a blood treatment unit.  FIG. 1  shows the main components of the hemodialysis apparatus in a very simplified schematic representation. The device for supplying the dialyzer with dialyzing fluid is a component part of the dialysis apparatus. 
     The dialysis apparatus comprises a dialyzer  1 , which is divided by a semi-permeable membrane (not represented) into a blood chamber (not represented) and a dialyzing fluid chamber. A blood supply line  2 , into which a blood pump  3  is incorporated, leads from the patient to an inlet  1 A of the blood chamber of dialyzer  1 , whilst a blood discharge line  4 , which leads to the patient, leads away from an outlet  1 B of the blood chamber of dialyzer  1 . During the blood treatment, the patient&#39;s blood flows in extracorporeal blood circuit I through the blood chamber of dialyzer  1 . 
     Dialyzer  1  is supplied with dialyzing fluid, which flows through the dialyzing fluid chamber of dialyzer  1 . The device for conveying the dialyzing fluid into dialyzer  1  is described below. 
     For the balancing of fresh dialyzing fluid against used dialyzing fluid, use is made of a balancing unit  5  which, in the present example of embodiment, comprises only one balancing chamber  6 . Balancing chamber  6  comprises a first inlet  6 A at the underside and a first outlet  6 B at the upper side as well as a second inlet  6 C at the underside and a second outlet  6 D at the upper side. 
     The dialyzing fluid is made available in a dialyzing fluid source  7 , which can be a canister or a bag. Leading away from dialyzing fluid source  7  is a first supply line  8 , which leads to first inlet  6 A of balancing chamber  6 . Leading away from first outlet  6 B of balancing chamber  6  is a first discharge line  9 , which leads to a drain  32 . Incorporated into first supply line  8  is a blood pump  10 , in particular an occluding pump, which conveys fresh dialyzing fluid from dialyzing fluid source  7  into balancing chamber  6 . 
     Leading away from second outlet  6 D of balancing chamber  6  is a second discharge line  11 , which leads to inlet  1 C of the dialyzing fluid chamber of dialyzer  1 . Leading away from outlet  1 D of the dialyzing fluid chamber of dialyzer  1  is a second supply line  12 , which leads to second inlet  6 C of balancing chamber  6 . 
     Supply lines and discharge lines  8 ,  9 ,  11 ,  12  are hose lines. Second discharge line  11  comprises, in the flow direction, a first section  11 A and a second section  11 B, whilst second supply line  12  comprises, in the flow direction, a first section  12 A and a second section  12 B. 
     Second discharge line  11  and second supply line  12  are connected via a bypass  13 . Bypass  13  is a line which is connected with one end to junction point  11 C between first section  11 A and second section  11 B of second discharge line  11  and with the other end to junction point  12 C between first section  12 A and second section  12 B of second supply line  12 . A fluid circuit II, which includes the dialyzing fluid chamber of dialyzer  1 , is created with bypass  13 . Fluid circuit II comprises bypass line  13 , second section  11 B of second discharge line  11 , the dialyzing fluid chamber of dialyzer  1  and first section  12 A of second supply line  12 . 
     A second pump  14  is incorporated into first section  11 A of second discharge line  11  and a third pump  15  is incorporated into second section  11 B of second discharge line  11 . Leading away from first section  12 A of second supply line  12  is an ultrafiltrate line  16 , into which a fourth pump  17  is incorporated, with which fluid (ultrafiltrate) can be withdrawn from fluid circuit II. The four pumps  10 ,  14 ,  15 ,  17  are connected via control lines  10 ′,  14 ′,  15 ′,  17 ′ to a control unit  18 . In the present example, control unit  18  is a component part of the central control unit of the dialysis apparatus. Central control unit  18  of the dialysis apparatus is also connected to blood pump  3  via a control line  3 ′. 
     A first shut-off element  19  is incorporated into first supply line  8  between first pump  10  and balancing chamber  6 , whilst a second shut-off element  20  is incorporated into first discharge line  9 . A third shut-off element  21  is incorporated into second discharge line  11  between balancing chamber  6  and second pump  14 , whilst a third shut-off element  22  is incorporated into second supply line  12  between junction point  12 C and balancing chamber  6 . Shut-off elements  19 ,  20 ,  21 ,  22  are electromagnetically operated hose clamps, which are connected via control lines  19 ′,  20 ′,  21 ′,  22 ′ to central control unit  18 . 
     Central control unit  18  controls pumps  10 ,  14 ,  15  as follows. The dialysis apparatus is operated in successive cycles, which each comprise two work steps.  FIG. 2  shows the first work step and  FIG. 2  the second work step of a work cycle. 
     The first work step comprises the filling of balancing chamber  6 , while dialyzing fluid is flowing through dialyzer  1 . Central control unit  18  opens first and second shut-off elements  19 ,  20  and closes third and fourth shut-off elements  21 ,  22 . Control unit  18  thereby puts first pump  10  and third pump  15  into operation. Second pump  14  is at a standstill. Since second occluding pump  14  is at a standstill, third shut-off element  21  can also be open. 
     First pump  10  conveys fresh dialyzing fluid out of dialyzing fluid source  7  into balancing chamber  6 , which has been filled with used dialyzing fluid in the second work step of the preceding work cycle. While balancing chamber  6  is being filled with fresh dialyzing fluid, the used dialyzing fluid is displaced via a first discharge line  9  into drain  32 . First pump  10  runs until such time as used dialyzing fluid has been completely replaced by fresh dialyzing fluid in balancing chamber  6 . During the filling of balancing chamber  6  with fresh dialyzing fluid, the fluid flow through dialyzer  1  is not interrupted. Third pump  15  conveys the dialyzing fluid in fluid circuit II, which includes second section  11 B of second discharge line  11 , dialyzer  1 , first section  12 A of second supply line  12  and bypass line  13 . Balancing chamber  6  should be filled as quickly as possible with fresh dialyzing fluid, so that the dialyzing fluid circulates for only a short period in the fluid circuit ( FIG. 1A ). 
     The first work step ( FIG. 1 ) is followed by the second work step ( FIG. 2 ). Central control unit  18  closes first and second shut-off elements  19 ,  20  and opens third and fourth shut-off elements  21 ,  22  in the second work step. Furthermore, control unit  18  stops first pump  10  and puts second pump  14  into operation. Consequently, second and third pumps  14 ,  15  are running. Control unit  18  selects a smaller delivery rate for second pump  14  than for third pump  15 . Consequently, dialyzing fluid flows in fluid circuit II at a flow rate which corresponds to the difference between the flow rates of third and second pumps  15 ,  14 . This flow rate QD fast  can be relatively high. 
     While dialyzing fluid is circulating in fluid circuit II through dialyzer  1 , fresh dialyzing fluid is constantly fed to fluid circuit II and used dialyzing fluid removed from fluid circuit  12 . The fresh dialyzing fluid is fed to fluid circuit II at the delivery rate preselected by second pump  14  via first section  11 A of second discharge line  11 , which is connected to second outlet  6 D of balancing chamber  6 . Used dialyzing fluid is withdrawn from fluid circuit II via second section  12 B of second supply line  12 , which is connected to second inlet  6 C of balancing chamber  6 . The dialysis apparatus also permits fluid (ultrafiltrate) to be withdrawn from fluid circuit II. Control unit  18  starts ultrafiltration pump  17  for the purpose of ultrafiltration. 
     Depending on the flow rates of second and third pumps  14 ,  15 , fresh dialyzing fluid can be supplied continuously in a relatively short or a relatively long time and the desired ratio between fresh and used dialyzing fluid in fluid circuit II can be adjusted. 
     The second work step ( FIG. 2 ) of the work cycle is then followed again by the first work step ( FIG. 1 ) of a subsequent cycle. 
       FIG. 3  shows a second example of embodiment of the dialysis apparatus, which differs from the embodiment described by reference to  FIGS. 1 and 2  solely in that a fifth shut-off element  23 , which is also operated by central control unit  18 , is incorporated into bypass line  13 . The parts corresponding to one another are therefore provided with the same reference numbers. Shut-off element  23  in bypass line  13  is in principle open during the operation of the dialysis apparatus. Shut-off element  23  can however also be closed in order to interrupt the circulation of the dialyzing fluid in fluid circuit II. 
     Shut-off element  23  in bypass line  13  is closed for the filling and venting of the fluid system, so that the fluid flow through the bypass line is interrupted. Furthermore, second shut-off element  20  is closed, so that fluid cannot pass into drain  32 . The fluid is fed via a first supply line  8  to balancing chamber  6  while pump  10  is running. When pumps  14  and  15  are running, the fluid can flow through second discharge line  11 , dialyzer  1  and second supply line  12 . For the purpose of venting, a venting valve  33  is provided at the upper side of balancing chamber  6 , which is represented only in outline in  FIG. 3 . 
       FIG. 4  shows an alternative embodiment of the dialysis apparatus of  FIG. 3 . The example of embodiment of  FIG. 4  differs from the embodiment of  FIG. 3  only by the routing of second discharge line  11  and second supply line  12  and the length of bypass line  13 . The parts corresponding to one another are again provided with the same reference numbers. In order to reduce the dead volume, in which air could accumulate when the fluid system is being filled, second discharge line and supply line  11 ,  12  are led directly to the connections of shut-off element  23 , so that the volume of bypass  13  can be reduced to a minimum. 
     The device according to the present invention for supplying the dialyzer with dialyzing fluid has the advantage that a balancing unit with two balancing chambers can be dispensed with. It is possible even with a balancing unit comprising only one balancing chamber to maintain a continuous flow of dialyzing fluid through the dialyzer during the balancing of fresh dialyzing fluid against used dialyzing fluid. 
     For the sake of completeness,  FIG. 5  shows a dialysis apparatus with two balancing chambers  6 A,  6 B which are connected in parallel and which operate alternately. The example of embodiment of  FIG. 5  differs from the embodiment of  FIG. 1  and  FIG. 2  in that second balancing chamber  6 B with respective supply lines and discharge lines  24 ,  25 ,  26 ,  27 , into which shut-off elements  28 ,  29 ,  30 ,  31  are respectively incorporated, is connected in parallel to first balancing chamber  6 A. Balancing unit  6  with two balancing chambers  6 A,  6 B is operated in a known manner, as is described for example in DE 28 38 414. 
       FIG. 6  shows a further example of embodiment, which differs from the embodiment of  FIG. 4  solely in that balancing chamber  6  is divided by a flexible partition wall  6 G into a first chamber half  6 E and a second chamber half  6 F. With this embodiment, first inlet  6 A and second outlet  6 D are connected to first chamber half  6 E, whilst second inlet  6 C and first outlet  6 B are connected to second chamber half  6 F. In this embodiment, the two chamber halves  6 E and  6 F of balancing chamber  6  are filled alternately with fresh and used dialyzing fluid. The parts corresponding to one another are again provided with the same reference numbers. With this embodiment, too, fluid circuit II permits the maintenance of the flow of dialyzing fluid through dialyzer  1  during the filling of balancing chamber  6  with fresh dialyzing fluid. When one of chamber halves  6 E or  6 F is being filled with fresh dialyzing fluid, the used dialyzing fluid is displaced from the respective other chamber half  6 F or  6 E.