Abstract:
A method that includes conveying overheated dialysate through a cassette in a manner to reduce the temperature of the overheated dialysate, and a dialysis system including a control unit configured to cause overheated dialysate to be conveyed through a cassette in a manner to reduce the temperature of the overheated dialysate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/464,264, filed May 4, 2013, which is a divisional of U.S. patent application Ser. No. 12/542,971, filed Aug. 18, 2009, which claims priority under 35 U.S.C. §119(a) to German Patent Application No. 10 2008 038 097.0, filed Aug. 18, 2008, the entire contents of which are hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to dialysis cassettes and related systems and methods. 
       BACKGROUND 
       [0003]    Cassettes for conveying dialysis liquids, such as dialysate, are known. Some known cassettes include connection elements for the connection of solution bags and lines leading to a patient and to a dialysis machine. The cassettes can have at least one pump chamber with an inflow and an outflow port as well as passages for conducting the supplied and conveyed liquid. The passages can be closed by the application of a compressive force acting on the walls of the passages. A heating device can be used for heating the dialysis liquid in the cassette to a desired temperature. 
         [0004]    Such cassettes are used, for example, in the area of peritoneal dialysis. During peritoneal dialysis, the peritoneum is filled and emptied with the help of a dialysis machine called a “cycler.” The flow of the dialysis liquid, i.e., dialysate, is controlled by a cassette system. During peritoneal dialysis, the dialysate is heated to the desired temperature in the cassette and is subsequently infused into the peritoneum. If an unexpected stoppage of the cycler occurs and the liquid supply to the patient is interrupted, the dialysate is no longer circulated in the cassette. As a result, the dialysate may be heated above the desired temperature due to the inertia of the heating apparatus. The overheated dialysate typically cannot be used for infusion into the patient when the cycler is restarted. Thus, the dialysate is typically discarded and replaced with new dialysate before the peritoneal dialysis treatment resumes. 
       SUMMARY 
       [0005]    In one aspect of the invention, a cassette is provided for conveying liquids, in particular dialysis liquids. The cassette includes connection elements for the connection of solution bags and lines leading to a patient and/or to a dialysis machine. The cassette further includes at least one pump chamber with an inflow port and an outflow port. In addition, the cassette forms lines or passages for conducting the supplied and conveyed liquids through the cassette. The cassette also includes valves for closing the lines. A heating device is provided for heating the liquid present in the passages to a desired temperature (e.g., a preset desired temperature). A control unit is also provided and is configured to conduct (e.g., circulate) liquid heated above the desired temperature until the desired temperature has been reached again. 
         [0006]    Reducing the temperature of the liquid allows the liquid to be used again. Excess heat from the overheated liquid can be transferred to the cassette surrounding it by circulating the overheated liquid within the cassette. 
         [0007]    In some implementations, at least one temperature sensor is provided for the measurement of the temperature of the liquid in the cassette. In certain implementations, the temperature sensor is positioned within the cassette. In some implementations, the temperature sensor is located on a dialysis machine and cooperates with the cassette when the cassette is positioned in a cassette compartment of the dialysis machine. 
         [0008]    In some implementations, two pump chambers are provided between which the liquid can be displaced until the liquid reaches (e.g., cools to) the desired temperature. 
         [0009]    In some implementations, the heating device and a heating region of the cassette act as a continuous-flow heater. In such implementations, the heating device and the heating region of the cassette are configured so that liquid is heated as it flows through the heating region of the cassette. 
         [0010]    In another aspect of the invention, a method includes displacing a liquid between the two pump chambers of the cassette until the liquid reaches (e.g., cools to) a desired temperature. 
         [0011]    In some implementations, when the desired temperature of the liquid is exceeded, the passage to which the line draining the liquid is connected is closed. At the same time, the heating power of the heating device is reduced. The liquid is pumped through one of the pump chambers from a heating region of the cassette into the other pump chamber. 
         [0012]    In the event that a high proportion of cool liquid is already present in the pump chamber into which the overheated liquid is conducted, the resulting mixture of liquid (i.e., the mixture of the overheated liquid and the cool liquid) is conveyed in reverse operation through a heating region of the cassette into the other pump chamber in order to simultaneously cool the heating region of the cassette in this process. 
         [0013]    If, in contrast, due to the admixture of the overheated liquid in the pump chamber, a liquid overheated at its mixed temperature should result, the mixed liquid is conveyed in forward operation through the heating region of the cassette into the other pump chamber to distribute the excess heat in the cassette. 
         [0014]    An additional aspect of the invention relates to a dialysis machine, such as a peritoneal dialysis machine, having a device for the reception of one of the previously described cassettes as well as a pump unit for actuating the pump chambers of the cassette. The dialysis machine includes a heating device configured to heat liquid flowing through a heating region of the cassette and a control unit configured to conduct (e.g., circulate) liquid heated above a desired temperature until the desired temperature has been reached again. 
         [0015]    By using certain dialysis cassettes, systems, and methods described herein, a dialysis liquid that may have been overheated can advantageously be returned to a desired temperature without having to discard the liquid. As a result, the total amount of dialysis liquid used during the treatment can be reduced because it is generally unnecessary to discard the overheated dialysis liquid and replace it with new dialysis liquid. In addition, the amount of time required for the treatment can be reduced since it is generally unnecessary to drain the overheated dialysis liquid and then replace it with new dialysis liquid. 
         [0016]    Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  is a plan view of a dialysis cassette. 
           [0018]      FIG. 2  is a front view of a dialysis system including a dialysis machine and the dialysis cassette of  FIG. 1 . 
           [0019]      FIG. 3  is a front view of the dialysis machine of  FIG. 2  with a door of the dialysis machine open to expose a cassette compartment of the dialysis machine. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  shows a disposable cassette  10  that can be retained in a correspondingly designed cassette compartment or mount of a dialysis machine (e.g., a peritoneal dialysis machine)  100  (shown in  FIG. 2 ). Referring to  FIGS. 1 and 2 , the reference numerals  2 ,  4 ,  6  characterize connection elements for the connection of solution bags, of lines leading to the patient and to the dialysis machine, and of drainage lines. Two fixedly attached hoses or lines  104  and  106  are arranged at the connectors  4  and  6 , with one of the hoses representing the patient hose and the other representing the drainage hose. The connection elements  2  allow the operator to connect the solution bags or other medication containers to the cassette  10 . 
         [0021]    Referring again to  FIG. 1 , the cassette  10  includes a base body  12  that is made of plastic and can be manufactured using injection molding technology or deep-drawing technology. Cut-outs as well as passages extend in the base body  12 . The base body  12  partly forms the walls of two pump chambers  20 ,  22  arranged next to one another as well as liquid passageways  30 ,  40 ,  50 ,  60  extending within the cassette  10 . Liquid passageways  80  and  90  are likewise partly formed by the base body  12  between the pump chambers  20  and  22 . 
         [0022]    The liquid passageway  50  is serpentine shaped and is provided within a heating region  52  of the cassette  10 . One end of the passageway  50  is connected to the passageway  30 , and the other end of the passageway  50  is connected to the passageway  40 . The cassette  10 , as discussed above, is configured to be retained in a cassette compartment of the dialysis machine  100 . Referring briefly to  FIG. 3 , the dialysis machine  100  includes a heating device  108 . When the cassette  10  is positioned within the cassette compartment of the dialysis machine  100 , as shown in  FIG. 2 , the heating device  108  is positioned adjacent the heating region  52  of the cassette  10  through which the passageway  50  extends. As a result of this arrangement, the dialysis liquid (e.g., dialysate) flowing through the passageway  50  is heated when the cassette  10  is positioned within the cassette compartment of the dialysis machine  100  and the heating device  108  is activated. 
         [0023]    As shown in  FIG. 3 , in addition to the heating device  108 , the dialysis machine  100  includes two pumps  110 ,  112  and multiple valve tappets T 1 , T 2 , T 3 , T 4 , T 5 , T 6 , T 7 , T 8 , T 9 , T 10 , T 11 , T 12 , T 13 , T 14 , T 15 , and T 16 . The pumps  110 ,  112  cooperate with the pump chambers  20 ,  22  to pump liquid through the various passages of the cassette  10 . The valve tappets T 1 , T 2 , T 3 , T 4 , T 5 , T 6 , T 7 , T 8 , T 9 , T 10 , T 11 , T 12 , T 13 , T 14 , T 15 , and T 16  cooperate with corresponding valves V 1 , V 2 , V 3 , V 4 , V 5 , V 6 , V 7 , V 8 , V 9 , V 10 , V 11 , V 12 , V 13 , V 14 , V 15  and V 16  of the cassette  10  to direct the conveyed liquid through the cassette  10  in a desired manner. The valve tappets T 1 , T 2 , T 3 , T 4 , T 5 , T 6 , T 7 , T 8 , T 9 , T 10 , T 11 , T 12 , T 13 , T 14 , T 15 , and T 16  can be pneumatically, hydraulically and/or mechanically controlled. 
         [0024]    Other details regarding the cassette and its function substantially correspond to those details and functions described in EP 0 956 876 B1, which is incorporated by reference herein. 
         [0025]    During normal function of the cassette  10  and the dialysis machine  100 , liquid (e.g., dialysate) is conveyed from the pump chamber  22  through the heating region  52  of the cassette  10  in the direction of the patient line that carries the liquid to the patient and that is connected to the connector  4 . The liquid thus flows from the pump chamber  22  via the passageway  80  after the opening of the valve V 4  through the passageway  50  adjacent the heater  108  of the dialysis machine  100  and via the opened valve V 5  as well as the opened valve V 6 . As the liquid flows through the passageway  50  adjacent the heater  108 , heat emitted from the heater  108  increases the temperature of the liquid. Thus, the heater  108  and the heating region  52  of the cassette  10  together act as a continuous-flow heating mechanism. At the same time that liquid is forced out of the pump chamber  22  and through the passageway  50 , the pump chamber  20  is supplied with fresh liquid. The fresh liquid can, for example, be supplied to the pump chamber  20  via the opened valves V 11  and V 1 , while the valves V 7 , V 3  and V 2  as well as V 9  are simultaneously closed. 
         [0026]    If problems arise in the patient line (e.g., if the patient line  104  connected to the connector  4  becomes occluded), the liquid present in the passageway  50  can be overheated due to an overshooting of the heating regulator. The overheated liquid can typically not be infused into the peritoneum due to its elevated temperature. 
         [0027]    When overheating of the liquid in the passageway  50  occurs, the valve V 6  is closed and the heating power in the heater  108  of the dialysis machine  100  is reduced via a control unit that is arranged in the dialysis machine  100 . At the same time, the valve V 11  is closed to prevent any additional fresh solution from being delivered to the pump chamber  20 . After turning off the heater  108  and closing valves V 6  and V 11 , the overheated solution is pumped via the pump chamber  22  through the passageway  50  adjacent the continuous-flow heater and into the pump chamber  20 . To do this, the valve V 4 , the valve V 5 , the valve V 7 , and the valve V 1  are opened. The pump stroke of the pump chamber  22  is ended when the pump chamber  20  is filled or the pump chamber  22  is emptied. 
         [0028]    Two possibilities now generally result for the cooling of the liquid in dependence on the ratio of the liquid contained in the pump chamber  20  to the warm liquid conveyed into the pump chamber  20 . 
         [0029]    If a high proportion of cool liquid (i.e., liquid that has not passed through the passageway  50  adjacent the heater  108 ) is present in the pump chamber  20 , the resulting mixed liquid, which is comparatively cooler than the overheated liquid due to the mixing of the liquids, is conveyed via the passageway  50  adjacent the heater  108  into the pump chamber  22  in reverse operation. In particular, the liquid is pumped back into the pump chamber  22  via the opened valve V 1 , the opened valve V 7 , the opened valve V 5 , and the opened valve V 4 . The partially overheated heating region  52  of the cassette  10  is also cooled by the comparatively cooler liquid. 
         [0030]    If, after delivering the overheated liquid to the pump chamber  20 , a high proportion of overheated liquid is present in the pump chamber  20 , the mixture of liquid (i.e., the mixture of the overheated liquid and any cool liquid that was present in the pump chamber  20  when the overheated liquid was delivered to the pump chamber  20 ) is conveyed in forward operation via the passageway  50  adjacent the heater  108  into the pump chamber  22 . Starting from the pump chamber  20 , the liquid is conducted into the pump chamber  22  via the opened valve V 2 , the opened valve V 5 , the opened valve V 7 , and the opened valve V 3 . In this variant, the excess heat of the overheated liquid is distributed in the cassette so that the temperature of the overheated liquid can be lowered to the desired temperature. 
         [0031]    While the heater  108  has been described as being part of the dialysis machine  100  and positioned adjacent to the passageway  50  of the cassette  10  when the cassette  10  is positioned in the cassette compartment of the dialysis machine  100 , in certain implementations, the cassette itself includes a heater or part of a heater. The heating region of the cassette can, for example, be equipped with a heating coil. In such cases, the heating coil can be connected to a power supply of the dialysis machine when the cassette is inserted into the cassette compartment in order to provide the coil with power that generates heat. 
         [0032]    While the control unit has been described as being part of the dialysis machine  100 , the control unit can alternatively be located at any of various other locations outside of the cassette  10 . 
         [0033]    Other embodiments are within the scope of the claims.