Patent Publication Number: US-8540875-B2

Title: System for use in a dialysis apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a divisional of U.S. patent application Ser. No. 12/626,348 filed Nov. 25, 2009, now U.S. Pat. No. 8,409,445. 
    
    
     BACKGROUND OF THE INVENTION 
     Dialysis is performed as a treatment for patients suffering from renal insufficiency. Dialysis can be performed either in the peritoneum, or through extracorporeal dialysis or filtration of blood. These two dialysis methods have in common the fact that dialysis fluids or dialysates take up the degradation products of metabolism. These dialysates usually contain high levels of sodium chloride and other electrolytes, such as calcium chloride, or potassium chloride, a buffer substance, such as bicarbonate, or acetate and acid to establish a physiological pH, plus optionally, glucose or another osmotic agent. 
     Dialysates are either supplied as ready-to-use solutions or they are prepared on site from concentrates, including solid concentrates. Solids offer the advantage of a small package volume and a low weight. Although solids also have disadvantages—electrolyte salts, for example, are highly hygroscopic—there is a trend toward offering only solid components for preparation of dialysates. 
     In the above mentioned hemodialysis systems, a flexible bag or container filled with a powdered salt concentrate is used to generate a concentrated salt solution. Purified fluid is added to the top of the container and the concentrated solution is removed from the bottom of the container. When the concentrated solution is removed from the bottom of the bag it is generally delivered to the hemodialysis machine for use in the dialysate. It is important that the fluid level in the container with the salt concentrate is maintained above the level of the salt in the container, when the solution is being pumped out of the bottom of the container. Under normal operation, the fluid level above the powdered salt layer is maintained or increases as the salt concentrate is consumed. However, if the fluid level falls below the level of the salt concentrate, air or gases in the bag may be pumped through the salt concentrate and out of the bottom of the container into the dialysate. 
     During hemodialysis, using systems such as described in U.S. Pat. No. 5,385,564 and U.S. Pat. No. 5,616,305, incorporated by reference herein, dry bicarbonate or acid concentrate is mixed with dialysate via a container using one or more ports. Even when the container is filled there is always air remaining in the container. The system cannot remove all of the air from the container without evacuating the air from the container via a vacuum system to create negative pressure, before filling the container with fluid. 
     To deter air from being drawn into the hydraulics of the machine during operation, it is desirable to fill the container with a sufficient volume or fluid to maintain a fluid layer above the dry powder. In the systems known in the art, without removing air from the bag via a vacuum, some containers will not maintain the correct fluid layer, and thus, extra air passes into the hydraulics which requires excessive venting procedures. The new method and arrangement of the present invention solves the problem without the need to generate a vacuum to evacuate the gases from the concentrate. 
     BRIEF SUMMARY OF THE INVENTION 
     In an embodiment, the present invention provides a system and a method for filling a container containing a dry powdered salt concentrate with purified fluid for use with a dialysis apparatus. According to a disclosed method, the trapped air or gases generated during the filling of the container are forced out of the container without the creating a vacuum in the container prior to filling. 
     According to a disclosed method, fluid is rapidly pumped into a container having a dry powdered salt concentrate. When the interior of the container reaches a first pressure, contents of the container, including residual and generated gases as well as some fluid, are permitted to flush from the container, and out eventually out of the system. During this flushing step, adequate fluid is provided to maintain the first pressure within the container. At the conclusion of the flushing step, the pressure in the container is reduced to a second, lower operating pressure, and the system begins regular operation with delivery of solution to the dialyzer. According to various embodiments, the flushing step may proceed for a set time, or until such time a given level of air is no longer detected in the solution leaving the container for a given period of time. 
     In another embodiment, the present invention also provides a system for removing gases from a container having a powdered salt concentrate for use in a dialysis apparatus. The system further includes a fluid source, a pump which is in fluid communication with the fluid source, at least one hydraulic line having one end in fluid communication with the fluid supply and a second end in fluid communication with a drain. The system further includes a bypass valve that is disposed downstream from the first pump and upstream from the inlet of the container. The valve is capable of directing fluid flow into the hydraulic line or into the container. An outlet of the container is in fluid communication with the hydraulic line downstream from the bypass valve. A pressure sensor monitors the pressure of the fluid pressure in the container. 
     In an embodiment, a second valve is provided downstream the container to facilitate pressurization of the container. In another embodiment an air sensor is provided to detect gases in the solution flowing from the container. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a schematic diagram the general environment where the system is operating. A patient is shown attached to a dialysis apparatus. It is understood that the system of the present invention supplies dialysate solution to such an apparatus for use in hemodialysis. 
         FIG. 2  is a schematic diagram of an embodiment of a system for the production and discharge of a liquid hemodialysis concentrate for use in a dialysis apparatus. 
         FIG. 3  is a representative drawing of an embodiment of a container having a powdered salt concentrate that can be used in the method and system of the present invention. 
         FIG. 4  is a partially cross-sectioned view of an embodiment of a container having a powdered salt concentrate that can be use in the method and system of the present invention. 
         FIG. 5  is a schematic diagram of an embodiment of a system for the production and discharge of a liquid hemodialysis concentrate for use in a dialysis apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     For the purposes of this disclosure, the term “operating pressure” means the fluid or fluid pressure in the container having a powdered salt concentrate, during operation of the system, where the system is capable of supplying a concentrated salt solution to the dialysis apparatus. The term “flushing step” means operating the system to remove trapped gases from a container having a powdered salt concentrate, by pumping fluid through the container at a pressure that is greater than the operating pressure of the system, and directing the outflow out of the system to a drain, instead of to a dialysis apparatus. 
     Turning now to the drawings,  FIG. 1  displays the general context of a dialysis system  10 . The dialysis system  10  includes the dialyzer  11 , and a subsystem  12  for preparing a salt solution from a powdered salt concentrate for use in the dialyzer  11 . The salt solution is provided to the dialyzer  11  for administration to a patient  13 . The dialysis system  10  may additionally include various other optional subsystems and equipment. 
       FIG. 2  illustrates a representative hydraulic arrangement of the dialysis system  10 . By way of a general overview of the operation, the system  10  includes a main hydraulic line  20   a - d  that is fluidly coupled to a fluid source  22  at one end, and to the dialyzer  11  at the other end, with various optional assemblies disposed along the mainline  20 . It is noted that the mainline  20   a - d  may include a plurality of hydraulic lines. In the illustrated embodiment, optional assemblies are disposed along the mainline  20  in addition to the subsystem  12  for preparing a salt solution and may include a hydroblock  24  and one or more balancing chambers  26 ,  28 . A return line  30   a - f  from the dialyzer  11  provides return flow from the dialyzer  11  to a drain  34 . As with the mainline, the return line  30   a - f  may include a plurality of hydraulic lines. Subassemblies such as an air separation chamber  36  or a heat exchanger  38  may be provided along the return line  30 . It is noted that not all elements of the illustrated hydraulic arrangement are necessary to the structure and operation of the subsystem  12  for preparing a salt solution from a powdered salt concentrate, although a general explanation is provided herein in the interest of completeness. 
     Turning now to the specifics of the illustrated hydraulic arrangement, the fluid source  22  may include any appropriate type of fluid or fluids. For example, a reverse osmosis fluid (RO fluid) source may be provided. It will be appreciated that an alternate fluid may be provided as required by the system  10 . While the fluid referenced in this disclosure will be fluid, it is intended that the terms “fluid” and “fluid” will encompass other appropriate fluids for the purposes of the disclosed method and arrangement. 
     Fluid from the fluid source  22  flows through mainline  20   a  to the hydroblock  24 . In this embodiment, the heat exchanger  38 , a pressure regulator  40 , and a control valve  42  are provided along the mainline  20   a  between the fluid source  22  and the hydroblock  24 . While the valve  42  controls overall flow to the mainline  20   a , the pressure regulator  40  may control the pressure of the fluid as it passes through this section of the mainline  20   a . The heat exchanger  38  may heat the fluid somewhat with heat from the return spent fluid, as will be discussed below. 
     The illustrated hydroblock  24  is a multichambered unit, the fluid being heated by a heater  41  in chamber  24   b  and vented to a vent  42  in chamber  24   c  as the fluid flows through the various chambers  24   a - e  of the hydroblock  24 . The fluid temperature within the hydroblock  24  may be monitored and/or controlled by a control thermostat  44 . A deaeration pump  46  pumps fluid between the forth and fifth chambers  24   d ,  24   e  of the hydroblock  24  to return the fluid to the mainline  20   b.    
     Leaving the hydroblock  24 , the mainline  20   b  bifurcates at a branch point  50 . Valves  52 ,  54  control the flow of fluid to the continuing mainline  20   c  and a subsystem line  56 , respectively. If the valve  54  is closed and valve  52  open, the fluid continues through the valve  52  to the mainline  20   c . If the valve  54  is open and the valve  52  closed, fluid proceeds through valve  54  to the subsystem line  56 . As with all of the valves in this disclosure, the valves  52 ,  54  may be simple shut-off valves, or other multiposition valves. For example, valves  52 ,  54  may be replaced by a single valve that includes positions that arrest flow entirely, that direct flow to the subsystem line  56 , or that direct flow along the mainline  20   c.    
     Returning to  FIG. 2 , the subsystem line  56  connects flow from the mainline  20   b  to the subsystem  12  for preparing a salt solution, as will be explained in greater detail below. After leaving the subsystem  12 , the salt solution is returned to the mainline  20   c  at least one of junction  58  or  60 . The continuing mainline  20   c  directs flow to the balance chambers  26 ,  28 , flow through the balancing chambers  26 ,  28  being controlled by a plurality of valves  62 - 69 . Each of the balancing chambers  26 ,  28  includes two separate subchambers separated by a flexible membrane, the significance of which will be discussed below. Flow from the subsystem  12  flows into the respective balancing chambers  26 ,  28  through valves  62  and  64 , and out from the balancing chambers  26 ,  28  through valves  66 ,  68 . 
     Leaving the balancing chambers  26 ,  28 , the fluid from the subsystem  12  is directed through mainline  20   d . Flows to and from the dialyzer  11  are controlled by a pair of control valves  70 ,  72  disposed along the mainline  20   d  and the return line  30   a , respectively. Thus, fluid from the balancing chambers  26 ,  28  flowing through mainline  20   d  moves on to the dialyzer  11  when dialyzer inlet valve  70  is in the open configuration, and bypass valve  74  in the bypass line  30   b  is in the closed position. 
     Following usage in the dialyzer  11 , spent fluid passes the control valve  72  to return to the system  10  through return line  30   a  and  30   c  with the bypass valve  74  is in the closed position. To ensure accurate operation of the balancing chambers  26 ,  28 , as discussed below, spent fluid passes into the air separation chamber  36 . From the air separation chamber  36 , separated gases, and potentially fluid, are passed through return line  30   d  to the drain  34  by opening shutoff valves  76  and  80 . Return fluid, from which the gases have been separated in the air separation chamber  36 , may be pumped by flow pump  78  through return line  30   e  to one or both of the balance chambers  26 ,  28  through valves  63 ,  65 . Leaving the balance chambers  26 ,  28  through valves  67 ,  69 , respectively, the spent fluid is directed to a heat exchanger  38  and the drain  34  by way of return line  30   f , overall flow to the drain  34  being controlled by shutoff valve  80 . It will be appreciated that the heated spent fluid passing through the heat exchanger  38  may be used to heat the fluid flowing from the fluid source  22  to the hydroblock  24 . 
     Operation of the balance chambers  26 ,  28  is known in the art. Within the balance chambers  26 ,  28 , fresh fluid from the subsystem  12  passes along one side of the internal membranes, while spent fluid passes along the other side of the internal membranes. As will be appreciated by those of skill in the art, this pumping of spent fluid from line  30   e  along one side of the membrane with fresh fluid passing along the other side of the membrane results in a balanced provision of fluid from and to the dialyzer  11  during use. 
     Returning now to the structure and operation of the subsystem  12  for preparation of a salt solution, as explained in detail above, fluid flowing from the mainline  20   b  from the hydroblock  24  may be directed to the subsystem  12  by opening the control valve  54  and closing control valve  52  at adjacent junction  50  to provide flow to the subsystem line  56 . To prepare the salt solution, fluid from the subsystem line  56  enters a container  82 , which contains a powdered salt concentrate. The container  82  may be of any appropriate design, and may include a so-called bi-bag, which is a collapsible, replaceable bag that encloses the powdered salt concentrate. As utilized in this disclosure, the term “container”  82  will be used to designate any or all of a rigid container, semiflexible container, or a bi-bag. 
     An example of a container  82  in accordance with the disclosed method is shown in  FIG. 3 . In this view, a protective cover has been removed to reveal the components of the container  82 . The container  82  may be coupled to the subsystem  12  by any appropriate arrangement. In the illustrated embodiment, the container  82  is coupled to the subsystem  12  by a connector  88  having an inlet  90  and an outlet  92 . As illustrated, the container  82  contains a dry powdered salt concentrate for use in preparation of a salt solution of a dialysate mixture. 
       FIG. 4  shows a partially cross-sectioned view of a container  82  having a protective cover  94  in place. A connector  88  may be utilized to couple the container  82  to the system  10 . In order to allow the entry of fluid into acid the removal of the salt solution from the container  82 , an inlet  90  and an outlet  92  are provided. Although the inlet  90  and outlet  92  are shown in an upper portion of the container  82 , the inlet  90  and outlet  92  may be alternately disposed, so long at the requisite mixing is obtained as provided by the disclosed method. For example, the inlet may be disposed in a lower portion of the container  82  to allow the fluid to be injected upward into the container  82  to encourage agitation to facilitate mixing. 
     In order to allow the mixed salt solution to be withdrawn from a container  82  that is not completely full, the outlet  92  originates below the level of fluid in the container  82 . In the illustrated embodiment, a tube  96  having a lower opening  98  is fluidly coupled to the outlet  92  such that the opening  98  may be disposed in a lower portion of the container  82 , that is, below the fluid level. To inhibit the intake of powdered salt that is not yet dissolved, a filter  100  may be disposed at the opening  98 . The filter  100  may be made of any appropriate material, such as, for example, porous polyethylene. 
     The container  82  and the connector  88  may likewise be made of any appropriate material, and may be the same as or different from one another. By way of example only, either or both may be made of high density polyethylene or similar materials. The flexible container  82  may likewise be made of any suitable material, such as, by way of example only, a polyamide-polyethylene coextruded film. 
     The container  82  contains a dry form of one or more of any suitable salts used for preparation of dialysis solution. By way of example only, such suitable salts include sodium bicarbonate and sodium acetate. It will be understood by those of ordinary skill in the art that, when the powdered salt is sodium bicarbonate in particular, carbon dioxide will typically be generated from the initial contact between the fluid and the bicarbonate powder. Residual air is likewise often disposed within the container  82 . As explained above, in order to provide proper removal of the salt solution from the container  82 , it is necessary to maintain the opening  98  into the outlet  92  of the container  82  below the surface of the fluid contained therein. It will thus be appreciated that a reduction of gases disposed within the container  82  typically provides more space for the introduction of fluid. 
     In order to expel air from the subsystem  12 , an air separation chamber  102  may be provided downstream the container  82 . The air separation chamber  102 , which is fluidly connected to the container  82  by the subsystem line  56 , is designed to remove both air residually disposed within the container  82  and gases precipitating out of the bicarbonate solution when fluid is introduced to the powdered salt during operation of the subsystem  12 . 
     In the illustrated embodiment, an air sensor  114  is provided on the air separation chamber  102 . It will be appreciated that the air sensor  114  may be alternately disposed and may be of any appropriate design. For example, the air sensor  114  may be a two-pronged air detection probe located at the top of the air separation chamber  102  such that an electric current between the two prongs is detected when fluid fills the chamber  102  to at least the level of the prongs. Conversely, when there is air in the chamber  102 , the air between the two prongs acts as an insulator and electric current does not flow. 
     Flow through the air separation chamber  102  is controlled by a control valve  104 . If air is not detected in the air separation chamber  102 , the control valve  104  is closed, the solution proceeds through subsystem line  108 , advanced by a pump  110  to rejoin the mainline  20   c  at junction  58 . The solution is then passed on to the balance chambers  26 ,  28  and to the mainline  20   d  for delivery to the dialyzer  11 . 
     Conversely, if the air sensor  114  detects air in the air separation chamber  102 , the control valve  104  is opened, and air is vented from the air separation chamber  102  through a degassing line  106  before rejoining the mainline  20   c  at junction  60 . Upon rejoining the mainline  20   c , the gas is passed to the balance chambers  26 ,  28  and to mainline  20   d ; with dialyzer valves  70  and  72  closed, the gas travels through return lines  30   b  and  30   c , through air separation chamber  36 , as explained above, before being expelled to the drain  34  through line  30   d.    
     While it is known to withdraw air from the container  82  by way of a vacuum prior to introduction of fluid to the powdered salt, the disclosed method does not utilize such a vacuum to remove all of the gas from the container  82  before the introduction of fluid, as in the prior art. Rather, the disclosed method provides the desired layer of fluid over the powdered salt in the container by minimizing air in the container  82  after the introduction of fluid thereto. The disclosed method will be explained first with reference to the basic structure for performing the claimed method (see  FIG. 5 ), and second with regard to the more detailed commercial embodiment of the system discussed above (see  FIG. 2 ). Following these explanations, the operations of the respective systems by way of a controller are discussed. 
     Turning first to  FIG. 5 , there is illustrated a system  10   a  for providing dialysate to a dialyzer  11   a . For ease of understanding, the same reference numerals followed by the letter “a” are generally utilized to designate similar structures, with the exception of mainline  20 , for which no modifier is utilized. 
     A mainline  20  fluidly couples a fluid source  22   a , a subsystem  12   a  for the preparation of a salt solution, a drain  34   a , and the dialyzer  11   a . The subsystem  12   a  includes a container  82   a  which includes a powdered salt. A pump  46   a  pumps fluid passing through a heater and deaerator  24  from the fluid source  22   a  to container  82   a  or to mainline  20   c , depending upon which of valves  54   a ,  52   a  is open. When valve  54   a  is open and valve  52   a  is closed, fluid is directed to the container  82   a . Conversely, when valve  52   a  is open and valve  54   a  is closed, fluid from the pump  46   a  bypasses the subsystem  12   a  entirely. 
     According to the disclosed method, with valve  54   a  open, valve  104   a  closed, and pump  110   a  disabled, the pump  46   a  pumps fluid into the container  82   a  until the pressure within the container  82   a  reaches a specified, first pressure level. In the arrangement of  FIG. 5 , valve  54   a  periodically closes to allow a pressure sensor  112   a  to read the pressure within the line and container  82   a . When the detected pressure reaches the specified, first pressure level, a flushing step is initiated by opening the downstream valve  104   a . In the flushing step, the salt solution is then pushed from the container  82   a  while adequate additional fluid is introduced to the container  82   a  to maintain the specified pressure. This rapid flushing results in the expulsion of both the aqueous salt solution and gas. 
     During the flushing step, the valves  70   a ,  72   a  to and from the dialyzer  11   a  are closed to isolate the dialyzer  11   a  from the remainder of the system  10   a . With valve  104   a  open and valve  52   a  closed, the fluid and expelled gas are directed through open bypass valve  74   a  to the drain  34   a . During this flushing step, the pump  46   c  continues to provide fluid to the container  82   a  to maintain the pressure in the container  82   a  at the first pressure level. 
     The flushing step continues for either a preset period of time or until such time as gas is no longer detected in the expelled fluid, as by an air sensor  114   a , for example, for a given period of time. The required flush time depends upon the volume of powdered salt disposed within the container  82   a , greater amounts of solution requiring a more lengthy flush time period. 
     As discussed above, while the valves of the illustrated embodiment are simple two position shut off valves, alternate arrangements are envisioned. By way of example only valves  70   a  and  74   a  could be replaced with a three position valve that shuts off flow entirely, directs flow to the dialyzer, or directs flow to the drain  34   a.    
     When the flushing step is completed, the valve  74   a  is closed to direct flow to the dialyzer inlet valve  70   a  as the container  82   a  begins normal operation at a second, lower operating pressure. During normal operation, the container  82   a  is filled with fluid as necessary to maintain the lower operating pressure, as the resultant fluid is directed to the dialyzer  11   a.    
     The disclosed process of rapidly and immediately pushing fluid through the bag reduces the amount of gas that vents into the top of the container  82   a , and, instead, pushes the gas out of the bottom of the container  82   a  in the flushing step. The expelled gas includes both residual gases in the container and the powdered salt, as well as carbon dioxide generated when fluid first makes contact with the powdered salt. It will be appreciated that the resultant reduction in gas within the bag provides additional room for the layer of fluid over the powdered salt. 
     The differences between the first pressure, that is, the flush pressure, and the second pressure, that is, the normal operation pressure, may be as appropriate to obtain the desired results. In an embodiment, the pressure in the container  82   a  during the flushing step can be raised anywhere from two to five fold over the operating pressure of the system, depending on the type of container and system. In an embodiment, the container  82   a  is pressurized in range between about 0.5 to 5 times the operating pressure, preferably between about 1 to 4 times the operating pressure, more preferably between about 1.5 to 3 times the operating pressure. In another embodiment, the pressure in the container  82   a  is maintained at about 2 times the operating pressure during the flushing step. 
     By way of example only, the fluid and trapped gases may be flushed from the system for a period of time ranging from 5 seconds to 5 minutes, depending upon aspects of the arrangement, including, for example, the volume of the container  82   a  and the amount of powdered salt contained therein. In various embodiments, the flushing step can last anywhere from 10 seconds to 2 minutes, 30 seconds to 2 minutes, 20 to 60 seconds, or about 30 seconds. 
     It will be appreciated that the system  10   a  may include additional fluid lines and components, such as, by way of example only, one or more of the components illustrated in  FIG. 2  and explained in more detail above. Referring to  FIG. 2 , with valve  54  open and valve  52  closed at junction  50 , the pump  46  moves fluid from the fluid source  22  through mainline  20   b  and subsystem line  56  to the container  82 . With valve  104  closed and pump  110  disabled, pressure rises within the container  82  as fluid continues to be pumped into the container  82  by pump  46 . When the pressure within the container  82  reaches a preset first pressure level, as measured by the pressure sensor  112 , valve  104  is opened to initiate flushing of salt solution and gases from the container  82 . The salt solution and entrained gases are then pushed from the container  82  in the flushing step, while the pump  46  provides additional fluid adequate to maintain the specified pressure within the container  82 . 
     In the embodiment of  FIG. 2 , the flushed solution and gas enter the air separation chamber  102 . Upon opening valve  104 , the gas and flushed solution from the air separation chamber  102  flow through valve  104  and degassing line  106  to junction  60 , where it rejoins the mainline  20   c . The gas and flushed solution then proceed through one or both of valves  62 ,  64  into one or both of the balance chambers  26 ,  28 , and out of one or both of valves  66 ,  68  to mainline  20   d.    
     With the dialyzer  11  isolated from the system  10  by closed input and outlet valves  70 ,  72 , and with bypass line  30   b  and valve  74  open, the expelled fluids and gas pass through return line  30   c  to air separation chamber  36 . In air separation chamber  36 , while a portion of the fluid may be separated from the gases, the gases and potentially fluid are directed through open valve  76  to return line  30   d  and open valve  80  to the drain  34 . During this flushing step, or during the subsequent recovery step, pump  78  may pump the separated fluid within the air separation chamber  36  through return line  30   e  to one or both of the balance chambers  26 ,  28  through valves  63 ,  65 . From the balance chambers  26 ,  28 , the fluid moves through open valves  67 ,  69  to an optional heat exchanger  38 , on through open valve  80  to the drain  34 . 
     In an embodiment, the pressure in the container  82  can range between about 10 mmHg and 500 mmHg, preferably between about 50 mmHg and 300 mmHg, and more preferably between about 100 mmHg and 200 mmHg. By way of example only, the container  82  may be maintained at 150 mmHg, while the operating pressure of the arrangement is on the order of 90 mmHg. 
     In order to detect when air is no longer present in the fluid entering the air separation chamber  36 , the air separation chamber  36  may include an air sensor  116  similar to the air sensor  114  of the air separation chamber  102 . Although the air sensors  114 ,  116  are provided on the air separation chamber  102  and air separation chamber  36 , they may be alternately disposed or additional sensors may be provided. At the conclusion of a set time period, or when gas is no longer detected by either one or both of the air sensors  114 ,  116 , the flushing step may be discontinued, and the pressure within the container  82  reduced to a regular system operating pressure, as measured by the pressure sensor  112  or other appropriate sensor. 
     During this recovery step, pump  78  may be engaged to pump any fluids accumulated in the air separation chamber  36  to the drain. When switching over to regular operation, pump  110  may be engaged to pump salt solution to join mainline  20   c  at junction  58 , and the valve  104  may be closed until such time as air is again detected by the air sensor  114 . At this time, the bypass valve  74  is closed to direct flow to the dialyzer  11 , and the valves  70 ,  72  may be reopened as appropriate to direct flow to and from the dialyzer  11 . During regular operation of the system, the pump  46  is operated to maintain a desired system operating pressure; this second pressure in the container  82  is lower than the first pressure utilized in the flushing step of the process. 
     During regular operation, the air separation chamber  102  separates gas from fluid in the salt solution progressing to the dialyzer  11 , while the air separation chamber  36  separates gas from spent fluid returning from the dialyzer  11 . It will be appreciated that this elimination of the gases in the fluids flowing to and from the dialyzer  11  facilitates efficient and accurate operation of the balancing chambers  26 ,  28  during regular operation of the system  10 . 
     As with the process explained with regard to  FIG. 5 , the disclosed process of rapidly and immediately pushing fluid through the container  82  in the system  10  of  FIG. 2  reduces the amount of gas that vents into the top of the container  82 , and, instead, pushes the gas out of the outlet  92  of the container  82  in the flushing process. 
     The system  10  may include one or more controllers, which are capable of activating one or more of the pumps  46 ,  110 ,  78 , and/or one or more of the valves  42 ,  52 ,  54 ,  104 ,  62 - 70 ,  72 ,  74 ,  76 ,  80 , and/or receiving input from pressure sensors  112  and/or air sensors  114 ,  116 . For the purposes of this disclosure, we refer to only one controller, although it will be appreciated that multiple controllers may be provided. The controller may be of any appropriate design, such as, for example, a Microchip PIC18F6410, although an alternate arrangement may be provided. 
     Returning to  FIG. 5 , the controller  120   a  receives input from the pressure and air sensors  112   a  and  114   a , and directs the actuation/operation of the pumps  46   a ,  110   a  and valves  54   a ,  52   a ,  104   a ,  70   a ,  72   a ,  74   a . In operation, the controller  120  directs the closure of valves  52   a ,  70   a ,  72   a ,  104   a , the opening of valves  54   a ,  74   a , and the disengagement of pump  110   a . The controller  120   a  then directs the pump  46   a  to pump fluid from the fluid source  22   a  to the container  82   a . When the reading received from the pressure sensor  112   a  reaches a preset first pressure, the controller  120   a  directs the opening of the valve  104   a , at which time, fluid and gas from the container  82   a  is directed through the valves  104   a ,  74   a  to the drain  34   a . During this time, the controller  120   a  directs the continued operation of the pump  46   a  at a speed sufficient to maintain the preset first pressure at pressure sensor  112   a . If the pressure falls below the preset first pressure, the controller  120   a  maintain valve  54   a  in the open position to allow the pump  46   a  to continue filling the container  82 ; conversely, if the pressure is above the preset first pressure, the controller  120   a  directs valve  54   a  to remain closed until such time as the pressure as measured by the pressure sensor  112   a  again matches the preset first pressure. 
     When the controller  120   a  receives a reading of no air from the air sensor  114   a  for a set period, the controller  120   a  causes the system  10   a  to operate under regular operation. That is, the controller  120   a  directs valves  104   a ,  74   a  to close and valves  70   a ,  72   a  to open, and directs the engagement of pump  110   a  to cause the salt solution to flow to the dialyzer  11   a . During regular operation, the controller  120   a  maintains a desired second, operating pressure, as measured by the pressure sensor  112   a , the second, operating pressure being lower than the preset first pressure. As indicated above, the control of the pressure within the container  82  may be established by the opening and closing of valve  54   a . In alternate embodiments of the arrangements shown in both  FIGS. 2 and 5 , however, control of the pressure within the container  82  may be established by reductions and increases in the speed of the pump  46   a / 46 , in conjunction with or separate from the opening and closing of valve  54   a / 54  and/or valve  52   a / 52 . 
     Referring to the embodiment of  FIG. 2 , a similar arrangement may be provided for operation of a controller. In various embodiments, the controller may receive input from pressure and air sensors  112 ,  114 ,  116 , and may direct the operation of any or all of pumps  46 ,  110 ,  78  and any or all of valves  42 ,  52 ,  54 ,  104 ,  62 - 70 ,  72 ,  74 ,  76 ,  80 . 
     By way of example of one such manner of operation of the controller, in a first step, the pump  110  is disabled, valves  104 ,  52  are closed, and valve  54  is opened, and the dialyzer  11  is isolated by closing valves  70 ,  72  and opening the bypass valve  74 . In the balance chambers, valves  62  and  65 - 69  are opened. 
     The controller opens valve  54  to allow pump  46  to pump fluid into the container  82 . When the pressure sensor  112  indicates that the desired, first pressure has been reached, the controller causes valves  104 ,  76  and  80  to be opened to flush gas and fluid through the container outlet through the air separation chamber  102 , through degassing line  106  and mainline  20   c , and through the balance chamber  26  to mainline  20   d . The gas and fluid then proceeds through the bypass line  30   b  into the air separation chamber  36 . From the air separation chamber  36 , the gases proceed through return line  30   d , through valve  80  to the drain  34 . During this flushing step, the controller causes the opening and closing of the valve  54  in conjunction with the continued operation of the pump  46  to maintain the desired preset first pressure within the container  82  as measured by readings from the pressure sensor  112 . After a preset period of time, for example, thirty seconds, the pump  78  may be activated to pump any accumulated fluids from the air separation chamber  36  through return line  30   e  and balance chamber  28  to the drain  34 . 
     Once no air is detected at the air sensor  114  for a period of time, for example, two consecutive minutes, the controller causes valve  104  to close. Once the remainder of the fluid and gas pass through the bypass line  30   b , bypass valve  74  is returned to a closed position, and the remainder of the valves are returned or set to a regular operating positions. The pump  110  is then activated, and the controller causes the valve  54  to open and close, such that the continued operation of the pump  46  provides a second, lower operating pressure at pressure sensor  112 . 
     As explained above, the disclosed method may operate to reduce the residual gases and the gases precipitating from the solution without drawing a vacuum on the container  82 . In the initial step, pressure is built in the substantially isolated container  82  until a first preset pressure is obtained. The flushing step is then initiated to flush gases, fluid, and entrained gases from the container to a drain. Either after a preset time or when gas is no longer sensed in the fluid from the container  82 , the system is returned to a second, lower operating pressure, and the fluid from the container  82  is directed to the dialyzer  11 . In this way, the level of air in the container  82  is effectively reduced to yield additional space for fluid. Accordingly, this reduction of air allows for effective operation of the container  82  in providing a salt solution for dialysis. 
     All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.