Abstract:
The invention concerns a system and a method of use of said system for performing fluid administration on a patient, the system comprising:  
     a liquid pump ( 1 ),  
     a liquid distribution system ( 2 ) connected to said pump ( 1 ) in such a way that liquid can flow from the liquid distribution system ( 2 ) to the pump ( 1 ) and vice versa,  
     liquid supply means ( 3 ) for supplying liquid to a patient ( 4 ) via said liquid distribution system ( 2 ) and said pump ( 1 ),  
     a patient conduit ( 5 ) adapted for connecting said liquid distribution system ( 2 ) to a patient ( 4 ),  
     the system being characterized by the fact that said liquid pump ( 1 ) is unidirectional and that said liquid distribution system ( 2 ) comprises switching means designed to alternatively connect the pump enter line ( 56 ) with the supply means ( 3 ) or with the patient conduit ( 5 ).

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to systems for performing peritoneal dialysis on a patient and more precisely to such systems which include a pump.  
       STATE OF THE ART  
       [0002]     Peritoneal dialysis systems as defined above are described in the following patent documents: EP 0 790 841 B1, EP 0 695 397 B1, EP 0 852 953 B1, EP 0 694 125 B1, EP 0 686 237 B1, EP 0 471 000 B1, EP 0 332 690 B1, EP 0 262 182 B1, EP 0 259 464 B1 and EP 1 195 171 A2.  
       SUMMARY OF THE INVENTION  
       [0003]     An objective of the present invention is to provide an improved peritoneal dialysis system and in particular an improved liquid distribution system.  
         [0004]     This objective and many others are achieved with the system as defined in claim  1  and  38 .  
         [0005]     Preferred embodiments of the invention are defined in dependent claims  2  to  37  and  40  to  46 .  
         [0006]     Several advantages result from the invention, in particular: 
        simpler, and therefore more efficient, liquid distribution system which may include only two distinct cavities,     possibility to use a peristaltic pump, in particular a rotatable peristaltic pump,     possibility to use an unidirectional pump which results in a higher precision and a longer life time,     possibility to fix the liquid distribution system and the pump together, alternatively with vibration attenuating means,     possibility to use a flexible membrane which covers the chambers and which include valve elements,     the membrane may be molded,     part of a pressure sensor can be incorporated in the membrane.        
 
         [0014]     Those and other advantages will be better understood in the detailed description of the invention exemplified here below, together with the following figures. 
     
    
     SHORT DESCRIPTION OF THE FIGURES  
       [0015]      FIG. 1  shows in a schematic way the principle of the invention  
         [0016]      FIG. 1A  shows the “fill” phase  
         [0017]      FIG. 1B  shows the “drain” phase  
         [0018]      FIG. 2  illustrates a first embodiment of the invention (liquid distribution system)  
         [0019]      FIG. 3  illustrates a second embodiment (disposable cartridge) including a warmer chamber  
         [0020]      FIG. 4  shows the embodiment of  FIG. 3  in a transparent view  
         [0021]      FIG. 5  shows the back side of the embodiment of  FIG. 3  (disposable cartridge)  
         [0022]      FIG. 6  illustrates the disposable cartridge of  FIG. 3  with the complete tubing set  
         [0023]      FIG. 7  shows an embodiment with the rotative parts (rollers) integrated on the cycler  
         [0024]      FIG. 8  shows the embodiment of  FIG. 7  without the rollers  
         [0025]      FIG. 9  the disposable cartridge in two parts allowing to absorb pump vibrations  
         [0026]      FIG. 10  shows a cycler without the cartridge insertion slot  
         [0027]      FIG. 11  illustrates a disposable cartridge opened showing the peritoneal pump  
         [0028]      FIG. 12  is an upper view of an elastic molded membrane  
         [0029]      FIG. 13  is a bottom view of the membrane of  FIG. 12   
         [0030]      FIG. 14  shows a membrane clipping system  
         [0031]      FIG. 15  shows the cycler of  FIG. 10  in an open state  
         [0032]      FIG. 16  shows a cartridge loader  
         [0033]      FIG. 17  shows the cycler of  FIG. 10 , the insertion slot opened with the cartridge  
         [0034]      FIG. 18  shows the cycler of  FIG. 10 , the insertion slot closed with the cartridge  
         [0035]      FIG. 19  shows a front view of a valve  
         [0036]      FIG. 20  shows a front view of a pressure sensor  
         [0037]      FIG. 21  shows a pump race  
         [0038]      FIG. 22  shows a valve actuator and a membrane clipping system  
         [0039]      FIG. 23  shows a warmer  
         [0040]      FIG. 24  shows a warmer casing  
         [0041]      FIG. 25  is a table showing drain profiles 
     
    
     NUMERICAL REFERENCES USED IN THE DRAWINGS  
       [0042]      1 . Pump  
         [0043]      2 . Liquid distribution system (cartridge)  
         [0044]      3 . Supply means (bag)  
         [0045]      4 . Patient  
         [0046]      5 . Patient line  
         [0047]      6 . Drain collector  
         [0048]      7 . First hub chamber  
         [0049]      8 . Second hub chamber  
         [0050]      9 . Liquid supply port with valve  
         [0051]      10 . Patient port with valve  
         [0052]      11 . Drain port with valve  
         [0053]      12 . Roller separator  
         [0054]      13 . Membrane  
         [0055]      14 . Membrane frame  
         [0056]      15 . Pressure sensor cavity (patient)  
         [0057]      16 . Patient port with valve (warmer chamber)  
         [0058]      17 . Warmer chamber  
         [0059]      18 . Patient port with valve (first hub chamber)  
         [0060]      19 . Warmer port  
         [0061]      20 . Roller element  
         [0062]      21 . Pump race  
         [0063]      22 . Roller  
         [0064]      23 . Tube connector for warming enter line  
         [0065]      24 . Liquid supply line  
         [0066]      25 . Drain line  
         [0067]      26 . Pump inlet  
         [0068]      27 . Pump outlet  
         [0069]      28 . Warmer pouch  
         [0070]      29 . Warmer enter line  
         [0071]      30 . Warmer exit line  
         [0072]      31 . Membrane pressure sensor area  
         [0073]      32 . Retaining element for pressure sensor  
         [0074]      33 . Clip cavity  
         [0075]      34 . Actuator  
         [0076]      35 . Clip plunger  
         [0077]      36 . Pressure sensor cavity (first hub chamber)  
         [0078]      37 . Pump flexible tube  
         [0079]      38 . Warmer port with valve  
         [0080]      39 . Membrane actuator clip  
         [0081]      40 . Membrane pressure volute  
         [0082]      41 . Cartridge loader  
         [0083]      42 . Pump motor+coder  
         [0084]      43 . Air sensor  
         [0085]      44 . Pressure sensor  
         [0086]      45 . Pump casing  
         [0087]      46 . Cartridge loader shaft  
         [0088]      47 . Cartridge loader frame  
         [0089]      48 . Cartridge loader linear cam  
         [0090]      49 . Cartridge loader motor  
         [0091]      50 . Cartridge insertion slot  
         [0092]      51 . Cycler  
         [0093]      52 . Cartridge motor shaft  
         [0094]      53 . Tube connector for supply line  
         [0095]      54 . Tube connector for drain line  
         [0096]      55 . Tube connector for warmer exit line  
         [0097]      56 . Pump enter line  
         [0098]      57 . Pump exit line  
         [0099]      58 . Sensor pressure housing  
         [0100]      59 . Sealing flange  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0101]     The peritoneal dialysis system according to the invention is shown in a schematic way in  FIG. 1 . It includes a pump  1 , a liquid distribution system  2  (also named cartridge) comprising a first hub chamber  7  and a second hub chamber  8 . The first chamber  7  includes a pump inlet  26  connected to the pump  1  via a pump enter line  56 , a liquid supply port  9  with valve connected to supply means, e.g. to bags  3 , via a liquid supply line  24  and a patient port  10  with valve connected to a patient  4  via a patient line  5 . The second chamber  8  includes a pump outlet  27  connected to the pump  1  via a pump exit line  57 , a drain port  11  with valve connected to a drain collector  6  via a drain line  25  and a patient port  18  with valve connected to a patient  4  via a patient line  5 .  
         [0102]      FIG. 1A  shows the “fill” phase where liquid is supplied to the patient  4  from and through the following elements: Bag  3 —Liquid supply line  24 —(open) liquid supply port  9 —First chamber  7 —Pump inlet  26 —Pump enter line  56 —Pump  1 —Pump exit line  57 —Pump outlet  27 —Second chamber  8 —(open) Patient port  18 —Patient line  5 —Patient  4 .  
         [0103]      FIG. 1B  shows the “drain” phase where liquid is drained from and through the following elements: Patient  4 —Patient line  5 —(open) Patient port  10 —First chamber  7 —Pump inlet  26 —Pump enter line  56 —Pump  1 —Pump exit line  57 —Pump outlet  27 —Second chamber  8 —(open) Drain port  11 —Drain line  25 —Drain collector  6 .  
         [0104]     The embodiment illustrated on  FIG. 2  shows an assembly constituted by a pumping element  1  and a cartridge  2 . Both elements are fixed together but may be separated.  FIG. 21  shows a better view of the fixation between both elements. Preferably, the pumping element  1  is fixed to the cartridge  2  by vibration attenuation means in order to minimize the vibration on cartridge  2  when the pump is operating.  
         [0105]     The upper face of the cartridge contains a first hub chamber  7 , a second distinct hub chamber  8  and a cavity  15  which forms part of a pressure sensor. The first chamber hub chamber  7  has three liquid supply ports  9 , one patient port  10 , one pump inlet  26  and a cavity  36  which forms part of a pressure sensor. The second hub chamber  8  has a patient port  18 , a drain port  11  and a pump outlet  27 .  
         [0106]     The pumping element  1  comprises a pump casing  45  which contains three rollers  22  maintained around the pump casing center by a roller separator  12 . The space between the roller-roller separator element and the pump casing defines a pump race  21  in which a flexible tube  37  is placed. The flexible tube being connected with the pump enter  56  and exit  57  lines. The rollers  22  may be motor driven by a shaft  52  (not shown on  FIG. 2 ) in such a way as to progressively compress the flexible tube  37  resulting thereby in a peristaltic movement along the flexible tube  37 .  
         [0107]     During the “fill” phase, liquid is supplied via one tube connector  53  and liquid supply port  9  to the first hub chamber  7 . It then enters the pump  1  through the pump inlet  26 , moves along the flexible tube  37 , enters the second hub chamber  8  through the pump outlet  27  and goes to the patient  4  via patient port  18  and patient line  5 .  
         [0108]     During the “drain” phase, liquid leaves the patient  4 , enters the first hub chamber  7  via patient port  10 . It then enters the pump  1 , moves along the flexible tube  37 , enters the second hub chamber  8  and goes to the drain collector  6  via drain port  11 , drain tube connector  54  and drain line  25 .  
         [0109]     It should be noted at this stage that each bag  3  may contain a specific liquid.  
         [0110]     The cartridge  2  of  FIG. 3  is identical to the cartridge of  FIG. 2  with the exception of an additional cavity, namely a warmer chamber  17 , which includes a warmer port  19  and a patient port  16 . The warmer port  19  is connected to a warmer  28  (not shown on  FIG. 3 ) via a warmer tube connector  55  and a warmer exit line  30 . The patient port  16  is connected to the patient line  5 . The second hub chamber  8  contains a warmer port  38  connected to a warmer  28  (not shown on  FIG. 3 ) via a warmer tube connector  23  and a warmer enter line  29 .  
         [0111]     During the “fill” phase, liquid is supplied via one tube connector  53  and liquid supply port  9  to the first hub chamber  7 . It then enters the pump  1 , moves along the flexible tube  37 , enters the second hub chamber  8 , moves into the warmer  28  via warmer port  38 , enters the warmer chamber  17  via warmer port  19  through the tube connector  55  and goes to the patient  4  via patient port  16  and patient line  5 .  
         [0112]     As it can be seen on the embodiments of  FIGS. 2 and 3 , the pump  1  is unidirectional, i.e. whatever the pumping phase is, liquid in the flexible tube  37  always moves in the same direction. This feature provides several advantages. In particular a higher precision in the liquid exchange due to the same flow speed for both the fill and drain phases and a longer life time.  
         [0113]     It is known that peristaltic pumps are usually accurate within ±5%. As such, peristaltic pumps cannot be used for peritoneal dialysis since the volume which is filled within the patient cavity requires to be drained in the same amount within ±2%, otherwise the peritoneal cavity could be overfilled (e.g. for 12 liters exchanged over the therapy, a 3% difference represents 360 ml which is as much as 18% of the 2 liters contained in the peritoneal cavity for each cycle) and/or the ultra-filtration could be altered. In order to improve on the accuracy of the exchanged volume without requiring the construction of highly accurate pumps which would warranty a ±2% accuracy, the invention provides a method whereby the conventional pump is used in a unidirectional way which insures the same accuracy for both the fill and the drain phase (usually within ±2%) and therefore an appropriate balance of fluid. The volume filled with such a pump may be inaccurate within ±5%, but since the same cassette with the same flow speed characteristics (namely the same flow direction) is used, the balance can be insured within ±2% as required for the therapy. If the cassette would be used in both directions, the difference in flow speed would be within ±5% due to the non parallel behavior of peristaltic pumps, in particular over time.  
         [0114]     It should be noted that with the present invention, the precision in the liquid exchange is maintained even if the pump flow rate changes after a certain time due to aging of the tubing since the fill and drain are operated within a time window which is small in comparison to the time in which the flow speed is altered by aging (e.g. a flow alteration of the pump of approximately 1% per 20 liters of fluid pumped, with exchanged volumes of approximately 2 liters per cycle). In addition, the use of the cassette in one direction enables a better control over the aging of the tubing and, therefore, a better prediction of the impact on the pumping accuracy.  
         [0115]      FIG. 4  is a transparent view of the cartridge which better shows how the different elements are connected. A cartridge bottom view is shown on  FIG. 5 . The tubing system in the lower face and the cavities of the upper face are all made within one single part, e.g. an injected part of plastic material.  
         [0116]      FIG. 6  shows an assembly including the cartridge  2  of  FIG. 3  fixed to a pumping element  1 , a patient line  5 , supply bags  3 , a warmer enter line  29 , a warmer outer line  30  and a warmer pouch  28  which is essentially made of a fluid circuit within a plastic bag (e.g. PVC) to be put into contact with a warming plate.  
         [0117]      FIG. 6 ″ shows a warming plate contained into a warming system where the warming pouch has a shape of a sock to be inserted onto the warming plate. The warming pouch is composed of a liquid channel which forces the liquid to be maintained within such warmer for a certain duration at a given flow rate.  
         [0118]      FIG. 7  shows a cartridge identical to the one of  FIG. 3  where the rollers are part of the cycler rather than of the cartridge. In this embodiment, the pumping element  1  which only contains the tube and tubing race and the cartridge  2  are forming a single element.  
         [0119]     The rollers, which are part of the cycler and therefore re-usable rather than disposable with the cardridge, have a conical shape so as to allow the rollers to be self inserted in the pump race. In this configuration the cartridge is more simple to manufacture and contains less parts. No other insertion mechanism is required, since the tube is automatically compressed on the race while the rollers are penetrating into the cartridge. As a separate matter, the use of conical rollers  22  results in a more constant speed of the liquid along the flexible tube  37 .  
         [0120]      FIG. 8  shows the assembly of  FIG. 7  without the rollers  22  and the roller element.  
         [0121]     Of course, other roller shapes may be used, e.g. spherical or cylindrical.  
         [0122]     The embodiment of  FIG. 9  only differs from the one of  FIG. 8  in that the pump casing  45  is made out of two parts with an interface between the pumping element  1  and the cartridge  2 . This configuration offers an improved assembly process of the pump and the possibility to add means to limit the propagation of the vibrations from the pump  1  to the cartridge  2 .  
         [0123]      FIG. 10  shows a cycler  51  without cartridge  2  and pumping element  1 . It contains a driving zone which includes a motor shaft  52  for the rollers  22  and several actuators  34 . The cycler  51  also includes an air sensor  43  situated close to the patient line  5  when the cartridge  2  is inserted. The air sensor may be made of a piezo emitter and a plezo receiver.  
         [0124]      FIG. 11  represents the embodiment of  FIG. 2  with a flexible membrane  13  covering the hub chambers  7 , 8  and the pressure sensor cavity  15 .  
         [0125]     The upper face of the membrane  13  (see  FIG. 12 ) contains several valve elements having a cylindrical cavity  39  and a pressure sensor area  31  with a ply  40  around its periphery. The valve elements  39  are designed to tightly close the ports when the membrane  13  moves downwardly.  
         [0126]     On its bottom face (see  FIG. 13 ) the membrane  13  contains a semi-circular flange  32  around the pressure sensor area and annular liquid tight joints.  
         [0127]     In addition the cartridge  2  includes liquid tight joints arranged in such a manner that they allow a liquid tight connection between the cartridge  2  and the membrane  13 .  
         [0128]     Advantageously the membrane is molded. Preferably the membrane  13  is made of silicone.  
         [0129]     The membrane  13  is press-fitted to the cartridge  2  along its periphery with a membrane frame  14  (see  FIG. 14 ).  
         [0130]      FIG. 15  shows the cycler of  FIG. 10  in an open state which includes a pump motor and a coder  42 . The rectangle  41  represents the cartridge loader.  
         [0131]      FIG. 16  shows a cartridge loader comprising cartridge loader shafts  46 , a cartridge loader frame  47 , a cartridge loader linear cam  48  and a cartridge loader motor  49 . On this figure, the two displacement parts  48 ′ and  48 ″ represent two different positions of the loader in an open and closed position only for explanation reasons.  
         [0132]     The cartridge loading mechanism allows a tight connection between the membrane and the valves and the cartridge. In order to insure proper positioning of the cartridge onto the valve actuators, as well as pressure sensor and air sensor onto the right place, the cartridge is maintained into the loading mechanism which progressively moves the cartridge in an axis which is perpendicular to its surface. By the same movement, the axis or the rollers can be inserted in the right position to ensure proper functioning of the pump. The same movement can also insure appropriate pressure on the surfaces which requires to be maintained together, such as for tightness control on the membrane and/or tubing of the pump.  
         [0133]      FIG. 17  shows the cycler  51  of  FIG. 10  containing a cartridge  2 . The cycler  51  has an insertion slot  50  in an open position.  
         [0134]      FIG. 18  shows the same cycler  51  but with an insertion slot in a closed position.  
         [0135]      FIG. 19  represents an actuator  34  with its plunger  35  clipped in its corresponding valve element  39  of the membrane. The actuator  34  may be a magnet or an electromagnetic element. The plunger  35  and the valve element  39  are designed to move together when the actuator is activated.  
         [0136]      FIG. 22   a  and  22   b  shows the plunger  35  and the valve element  39  in a separate position ( FIG. 22   a ) before insertion and in an activated position ( FIG. 22   b ) after insertion. One embodiment of the invention is to insure a proper insertion of the actuator head into the membrane clipping part by having the length of the part of the actuator head to be inserted into the clip of the membrane to be longer than the possible displacement of the actuator head, so as to ensure that the actuator head is always properly inserted into the clip of the membrane. As such, in the worst case where the actuator head would be fully retracted within the actuator during the clipping translation into the membrane, the actuator head would pass the clipping equilibrium position before the end of the translation, so that the remaining translation will ensure clipping of the actuator head into the membrane.  
         [0137]     The front view of  FIG. 20  illustrates a pressure sensor  44  which may be used with the independent pressure sensor cavity  15  of the cartridge  2  or with the pressure sensor cavity  36  of the first hub chamber  7 . The ply  40  makes the pressure sensor less sensitive to the elasticity of the membrane  13  in the sensor pressure area. In addition, the shape of the cavity  15  shall be made such that air can be eliminated easily when fluid is passing into the cavity (e.g. by having a round shaped bottom of the cavity within the direction of the flow).  
         [0138]     In the embodiments discussed previously, each port has a dedicated valve. This is not the case for the pump inlet and the pump outlet which are always kept open.  
         [0139]     The invention encompasses several other features not necessarily illustrated on the figures. For instance, the cycler or the cartridge-pumping element assembly may contain a window for detecting correct positioning of the flexible tube of the pump as shown in  FIG. 21  (circle).  
         [0140]     When the system functions, the pressure is preferably always maintained positive with respect to the drain. This is a safety measure which avoids said contaminated liquid to potentially infect the patient.  
         [0141]     Advantageously the liquid pressure entering and exiting the cartridge is sensed and, if necessary, the pump flow rate is corrected in accordance with the pressure difference. This pressure difference is better calculated at the initial priming phase of the system, where the pressure is directly related to the positioning of the liquid bags  3  and the patient position relative to the cycler.  
         [0142]     Alternatively or in addition, the pump flow rate may be regulated according to a predetermined deterioration of the tubing which is known from the characteristics of the tubing.  
         [0143]     The drain phase may be limited as to its duration in function of the drain speed, the drain speed having to be reduced when the patient peritoneal cavity pressure decreases, typically between 30 ml/min and 120 ml/min instead of a nominal 200 ml/min speed. This feature is particularly interesting because the dialysis efficiency is directly related to the time the liquid stays in the peritoneal cavity and the duration required to fully drain the peritoneal cavity may limit this time without a significant impact with regard to the peritoneal fluid characteristics. As such, one method of the invention would be to determine at which speed it is not worth continuing draining the patient entirely and rather fill the patient with fresh fluid, taking into consideration the remaining fluid volume in the peritoneal cavity which has not been expelled and expected ultra-filtration additional volume to avoid overfill. The cycles will therefore be all different, based on reaching a pre-determined drainage speed or a pre-determined decrease profile of the drainage speed, so that the efficient time of dialysis will be increased. An example of drainage speed on a patient is given in the  FIG. 25 , where, for each column which is divided in three parts, the upper part corresponding to a limit of drainage speed at which it is, for example, not worth continuing the drainage even if the next fill volume will not be a full fill. In comparison to actual method where a tidal at (e.g. 80%) is preset, the method under the invention is adapting each drainage to the actual drainage speed, trying to empty as much as possible without compromising on the efficacy of the peritoneal dialysis. Of course some limits can be set, where a minimum of drainage volume has to be reached before such a limitation takes place for each cycle.  
         [0144]     Another method under the present invention consists to fill always as much volume, within certain limits to be set for the patient, until a certain pressure in the peritoneal cavity is reached. As such, the peritoneal dialysis can be improved since the efficiency is related to the amount of fluid filled at every cycle. According to such method, the pump shall fill the patient until a certain pressure is reached (e.g. 10 cm water) and stop only once such pressure is reached or a certain maximum volume is reached. Accordingly, it is important to measure continuously the pressure during the dwell time to make sure that no over pressure is reached, such as due to the ultra-filtration. One possibility is also to always fill up to such a limited pressure and/or volume and drain at a certain interval thereafter a certain volume to compensate for expected ultra-filtration. Another possibility is to increase the ultra-filtration during the last cycle, by using e.g. low sodium concentrated solution.