Patent Publication Number: US-2022211926-A1

Title: System and method for preparing peritoneal dialysis fluid at the time of use

Description:
PRIORITY CLAIM 
     This application claims priority to and the benefit as a continuation application of U.S. patent application Ser. No. 16/447,415, entitled “Dialysis System For Mixing Treatment Fluid At Time Of Use”, filed Jun. 20, 2019, which claims priority to and the benefit as a continuation application of U.S. patent application Ser. No. 14/044,597, entitled “Dialysis System Having Autoidentification Mechanism”, filed Oct. 2, 2013, now U.S. Pat. No. 10,335,532 issued Jul. 2, 2019, which claims priority to and the benefit as a continuation application of U.S. patent application Ser. No. 13/308,775, entitled “Dialysis Method Having Supply Container Autoconnection”, filed Dec. 1, 2011, now U.S. Pat. No. 8,597,230, issued Dec. 3, 2013, which claims priority to and the benefit as a continuation application of U.S. patent application Ser. No. 12/785,069, entitled “Dialysis Method Having Supply Container Autoconnection”, filed May 21, 2010, now U.S. Pat. No. 8,083,709, issued Dec. 27, 2011, which claims priority to and the benefit as a continuation application of U.S. patent application Ser. No. 11/773,750, entitled “Dialysis System Having Supply Container Autoconnection”, filed Jul. 5, 2007, now U.S. Pat. No. 7,736,328, issued Jun. 15, 2010, the entire contents of each of which are hereby incorporated by reference and relied upon. 
    
    
     BACKGROUND 
     The examples discussed below relate generally to medical fluid delivery. More particularly, the examples disclose systems, methods and apparatuses for automated peritoneal dialysis (“APD”). 
     Due to various causes, a person&#39;s renal system can fail. Renal failure produces several physiological derangements. The balance of water, minerals and the excretion of daily metabolic load is no longer possible and toxic end products of nitrogen metabolism (urea, creatinine, uric acid, and others) can accumulate in blood and tissue. 
     Kidney failure and reduced kidney function have been treated with dialysis. Dialysis removes waste, toxins and excess water from the body that normal functioning kidneys would otherwise remove. Dialysis treatment for replacement of kidney functions is critical to many people because the treatment is life saving. 
     One type of kidney failure therapy is peritoneal dialysis, which infuses a dialysis solution, also called dialysate, into a patient&#39;s peritoneal cavity via a catheter. The dialysate contacts the peritoneal membrane of the peritoneal cavity. Waste, toxins and excess water pass from the patient&#39;s bloodstream, through the peritoneal membrane and into the dialysate due to diffusion and osmosis, i.e., an osmotic gradient occurs across the membrane. The spent dialysate is drained from the patient, removing waste, toxins and excess water from the patient. This cycle is repeated. 
     There are various types of peritoneal dialysis therapies, including continuous ambulatory peritoneal dialysis (“CAPD”), automated peritoneal dialysis (“APD”), tidal flow dialysate and continuous flow peritoneal dialysis (“CFPD”). CAPD is a manual dialysis treatment. Here, the patient manually connects an implanted catheter to a drain, allowing spent dialysate fluid to drain from the peritoneal cavity. The patient then connects the catheter to a bag of fresh dialysate, infusing fresh dialysate through the catheter and into the patient. The patient disconnects the catheter from the fresh dialysate bag and allows the dialysate to dwell within the peritoneal cavity, wherein the transfer of waste, toxins and excess water takes place. After a dwell period, the patient repeats the manual dialysis procedure, for example, four times per day, each treatment lasting about an hour. Manual peritoneal dialysis requires a significant amount of time and effort from the patient, leaving ample room for improvement. 
     Automated peritoneal dialysis (“APD”) is similar to CAPD in that the dialysis treatment includes drain, fill, and dwell cycles. APD machines, however, perform the cycles automatically, typically while the patient sleeps. APD machines free patients from having to manually perform the treatment cycles and from having to transport supplies during the day. APD machines connect fluidly to an implanted catheter, to a source or bag of fresh dialysate and to a fluid drain. APD machines pump fresh dialysate from a dialysate source, through the catheter, into the patient&#39;s peritoneal cavity, and allow for the dialysate to dwell within the cavity and for the transfer of waste, toxins and excess water to take place. The source can be multiple sterile dialysate solution bags. 
     APD machines pump spent dialysate from the peritoneal cavity, though the catheter, to the drain. As with the manual process, several drain, fill and dwell cycles occur during dialysis. A “last fill” occurs at the end of APD, which remains in the peritoneal cavity of the patient until the next treatment. 
     Both CAPD and APD are batch type systems that send spent dialysis fluid to a drain. Tidal flow systems are modified batch systems. With tidal flow, instead of removing all of the fluid from the patient over a longer period of time, a portion of the fluid is removed and replaced after smaller increments of time. 
     Some continuous flow, or CFPD, systems clean or regenerate spent dialysate instead of discarding it. Others use a large volume of fresh dialysate. The systems pump fluid into and out of the patient, through a loop. In a regenerating system, dialysate flows into the peritoneal cavity through one catheter lumen and out another catheter lumen. The fluid exiting the patient passes through a reconstitution device that removes waste from the dialysate, e.g., via a urea removal column that employs urease to enzymatically convert urea into ammonia. The ammonia is then removed from the dialysate by adsorption prior to reintroducing the dialysate into the peritoneal cavity. Additional sensors are employed to monitor the removal of ammonia. Regenerating CFPD systems are typically more complicated than batch systems. 
     Peritoneal dialysis (“PD”) systems, home hemodialysis/hemofiltration, and intensive care unit procedures that use bagged peritoneal dialysate, hemodialysis dialysate, or hemofiltration substitution solution can use a dual chamber bag. For example, bicarbonate based solutions have been developed for certain ones of the above applications. Bicarbonate is unstable in the presence of magnesium and calcium and forms a precipitate after a period of time. The bicarbonate based solutions are accordingly provided in a dual chamber bag. Prior to use, a seal between the two chambers is broken and the two concentrate solutions are mixed and used before calcium or magnesium precipitate can form. Unfortunately, a single concentrate solution delivered to a patient due to the two concentrate solutions not mixing can create a physiologically unsafe condition for the patient. 
     The system below addresses various drawbacks with the above-mentioned medical fluid treatments. 
     SUMMARY 
     The present disclosure describes an improved automated peritoneal dialysis (“APD”) system, however, many of the teachings herein are applicable to other medical fluid treatments, especially other renal failure therapy treatments, such as hemodialysis (“HD”), hemofiltration (“HF”), hemodiafiltration (“HDF”) and continuous renal replacement therapy (“CRRT”). 
     The system offers improved treatment and ease of use features. The system is mobile in one embodiment so that the patient can, for example, start a therapy in the family room and move the system to a bedroom on the same floor. The system manages supply bags, which are carried with the device or instrument when the patient moves the instrument. The system also employs a bag management system, which tilts the supply bags so that gravity will cause fluid to flow from them, leaving air behind during the priming sequence and normal operation. The gravity induced air separation at the supply bags allows the system to pump at high flowrates because there is little concern that the air has not been removed properly while pumping the fluid. 
     The system provides a cart having a rotating bearing plate or “lazy Susan” that supports the instrument and allows it to be rotated for convenient operation, making at least the vast majority of system features readily accessible. This may allow the patient to correct most alarms without getting out of bed. The “lazy Susan” plate can optionally have detent positions every ninety degrees or so. 
     The system includes an improved priming procedure using a patient line having dual lumens. During the patient line prime, fluid flows down one lumen away from a disposable cassette and back up the other lumen towards the cassette forming a closed loop feedback that indicates when priming is complete. This feedback is operable even with patient line extensions. U.S. Patent Application No. 2004/0019312 A1, FIG. 2, owned by the eventual assignee of the present disclosure, shows a tip protector for a dual lumen patient line that is compatible with this priming technique. The dual lumen line also eliminates the volume of spent effluent fluid that is pushed back (recirculated) when the instrument cycles from drain to fill. Additionally, the dual lumen line accommodates the sensing of intraperitoneal pressure (“IPP”) to optimize patient fill and drain volumes as described in U.S. Pat. No. 6,497,676, owned by the eventual assignee of the present disclosure, the entire contents of which are incorporated expressly herein by reference. Further still, the dual lumen patient line allows the same disposable set to be used for large and small patients because the recirculation volume is near zero. 
     The system also provides an auto-connection mechanism that connects connectors from the supply bags to connectors of the cassette supply lines. In one embodiment, the system provides for up to four supply bags, which can be connected to a manifold of the auto-connection mechanism. Each solution bag can be the same or different. The auto-connection mechanism is advantageously able to use the same solution bag (e.g., made having existing spikes and spike septums with existing equipment and processes). Tip protectors which protect the supply and bag pigtail connectors are modified to be compatible with the auto-connection mechanism. 
     As discussed in detail below, the system of the present disclosure is readily adapted for a high-volume therapy. In one implementation, the system uses four-to-one manifolds, which allow any one or more of four supply bag inlets to the disposable cassette to be increased to up to four bags for treatment. The four-to-one manifolds work in conjunction with the auto-connection and auto-identification systems described herein. Up to four, four-to-one manifolds, each manifold being able to connect to up to four (e.g., same-solution) supply bags, can accommodate a therapy volume of, for example, up to ninety-six liters. 
     Each of the manifold lines in the four-to-one manifold is placed in the auto-connection mechanism for connection to the supply lines connected to the disposable cassette. The single supply line of the disposable cassette can now connect to up to four solution bags. An imaging system recognizes the four to one connector and the type of attachment made to the manifold (the one line) end of the four to one manifold. 
     The auto-connection system also includes an automatic clamping system, which allows the user to not have to clamp and unclamp solution lines during the connection process or when an alarm condition occurs. 
     An imaging system or solution identification system verifies the volume, expiration date, composition, and configuration (e.g., single bag solution, multiple chamber bag solution, or multiple bag solution that requires mixing) before the bags are connected. The solution identification system verifies that the composition and volume of the solutions are consistent with the therapy prescription before connection. The solution identification system also: (i) automatically draws solution in the correct sequence when the correct solution bags are loaded; (ii) informs the user if the incorrect solution bags are loaded; and (iii) alerts the user if a solution bag connector is deformed, potentially causing an improper connection. 
     The disposable set (cassette, bags and lines) of the system is relatively simple and easy to use and requires fewer product codes because all geographic regions can use the same disposable set for both pediatric patients and adult patients, and with therapy volumes up to ninety-six liters. The lines of the disposable set are connected to organizers (e.g., cassette supply lines connected to a first organizer and patient and drain lines connected to a second organizer), which prevent the lines from becoming tangled and facilitate loading the lines into the auto-connection system. 
     The disposable set allows for admixing as described in U.S. Pat. No. 5,925,011, owned by the eventual assignee of the present disclosure, the entire contents of which are incorporated expressly herein by reference, or for the delivery of single part solutions, or double part solutions contained in a single bag. If a peel seal or frangible seal needs to be broken before use, the system can verify that it has been broken before the solution is delivered to the patient. Capacitive sensors located on the bag management shelves are used to verify that the seal has been broken and that the same solution is present in both chambers (ends) of the solution bag. 
     In an alternative embodiment, the sensor is an inductive sensor, which can (i) detect whether a emitter chamber bag has been loaded properly onto one of the bag management shelves and (ii) detect whether a frangible seal between two chambers bags has been broken such that the concentrate solutions can mixed properly for delivery to the patient. The inductive sensing apparatus and method are not limited to renal applications and can be used to confirm placement, mixing, etc., for any medical fluid system using dual or multi-chamber bagged solutions. 
     The system further provides a non-invasive temperature measuring feature or technique. The heat sensing technique uses a non-invasive infrared temperature sensor and electromagnet. The electromagnet controls the orientation of the temperature sensor. The disposable cassette has sheeting with a black or opaque area. A first orientation of the infrared sensor is trained on the black or opaque area and consequently measures the temperature of the sheeting. The second orientation of the infrared sensor is trained on an area of the sheeting which is not black or opaque and can thus see through the sheeting into the fluid behind the sheeting. This second infrared sensor reading measures a combination of the temperature of the film and the fluid. Discussed herein are algorithms for calculating the temperature of the fluid from the two infrared temperature readings. 
     The HomeChoice® APD System marketed by the eventual assignee of the present disclosure, uses a method described in U.S. Pat. No. 4,826,482 (“The &#39;482 patent”), to determine the volume of fluid pumped to the patient or to the drain. That method in essence looks backwards after a pump stroke to see how much fluid has been pumped to the patient. While this system has been highly successful, there are various reasons to know the volume of fluid pumped during the pump stroke or in real time. The reasons are discussed in detail below but in general include: (i) being able to fill/drain a patient to a volume that is not equal to a whole number of pump strokes; (ii) being able to immediately know when a patient is drained to empty or virtually empty to reduce pain at the end of drain; (iv) providing accuracy needed for mixing solutions; and (v) helping to eliminate the need to have to provide an alternate source of fluid, so that a partially full pump chamber can be differentiated from a pump chamber containing air and fluid. 
     The real time system and method in one embodiment monitors the pressure decay in a pressurized tank in fluid communication with the pump chamber of the disposable cassette. The system knows the volume of air or gas (V gas ) in the pump chamber prior to opening the valve to the tank. Then, after the valve to the tank is opened the system takes pressure readings at desired intervals and performs a calculation after each reading. The initial pressure (P1) in the tank is known. If the pressure at any given point in time is taken as P1′ then a ratio can be expressed in an equation form as follows: 
       ((P1/P1′)−1),
 
     this ratio is multiplied by an addition of the gas volume V gas  to a known volume of the tank V tank  to form a real time volume of fluid pumped V fluid =((P1/P1′)−1) (V tank +V gas ). P1 is initially equal to P1′, thus making the initial real time volume of fluid pumped equal to zero. As P1′ becomes increasingly less than P1 over time, ((P1/P1′)−1) becomes increasingly larger over time as does Vfluid . 
     The real time volumes are useful for many purposes as described above. Described below is an algorithm for using the real time volumes to determine features such as: (i) if a full pump stroke has occurred; (ii) if a line occlusion has occurred; (iii) if a leak has occurred; and (iv) if multiple concentrates have been mixed properly, for example. 
     The cassette in one embodiment has sheeting welded to the molded plastic piece as described in U.S. Pat. Nos. 5,401,342, 5,540,808, 5,782,575 and 6,001,201. In an alternative embodiment, the molded plastic piece is enclosed within welded sheeting but not welded to the sheeting. The sheeting in one embodiment is welded to itself and to the tubing attached to the cassette, allowing the inside of the sheeting, including the molded plastic piece, to be isolated from the environment. This cassette assembly provides flexibility in material selection for the molded plastic, sheeting and tubing because the sheeting to molded plastic seal has been eliminated. The sheeting material therefore does not need to be compatible with the rigid cassette material from a welding or bonding standpoint. 
     A disposable cassette having three pumping chambers is also shown and described below. The three chamber cassette provides a number of advantages, such as allowing for continuous flow at both the inlet and outlet of the pump even when running a standard, e.g., batch, therapy. With two pump chambers, fluid measurement is performed in an attempt to make patient flow essentially continuous. For example, the fluid measurements can be made in one pump chamber, while the other pump chamber is halfway through its pump stroke and vice versa. Nevertheless, the fresh supply and drain flowrates are pulsatile because more fluid will be flowing at certain times than at others. The three pump cassette therefore allows for continuous flow to a patient even when two solutions are being mixed online. 
     The system also includes an improved cassette/manifold membrane assembly or system. The assembly or system includes an interface plate having pump actuation areas with actuation ports for allowing a positive or negative pressure to be applied within the pump actuation areas to the membrane gasket to correspondingly place a positive or negative pressure on a juxtaposed flexible sheeting of the disposable cassette. Likewise, the interface plate includes valve actuation areas with actuation ports for allowing a positive or negative pressure to be applied within the valve actuation areas to the membrane gasket to correspondingly place a positive or negative pressure on the juxtaposed flexible sheeting of the disposable cassette. In addition to the actuation ports, the cassette interface includes an evacuation port to evacuate air between the membrane gasket and cassette sheeting adjacent to each pump and each valve. 
     The gasket includes blind holes that seal around the sidewalls of the actuation ports of the valves or pump chambers. The blind holes include a sheath or thin portion that extends over the valve or pump actuation ports. Positive or negative pressure applied through actuation ports is therefore likewise applied to the sheath portion of the blind hole of the members. Positive or negative pressure applied to the sheath portion accordingly causes a flexing of the sheath portion and corresponding flexing of the cassette sheeting. 
     The membrane also provides a through-hole for each evacuation port of the interface plate. The through-holes seal around the sidewalls of the protruding evacuation ports and allow a negative pressure applied through the evacuation ports to suck the cassette sheeting against the sheath portions of the membrane gasket forming pump or valve areas. In this manner, for a given pump or valve area, the membrane gasket and cassette sheeting flex back and forth together. 
     If a hole develops in either the membrane gasket or the cassette sheeting, the vacuum level through the evacuation port at the leak decreases, indicating the leak. Thus the evacuation ports also serve as leak detectors that are placed in multiple places over the cassette, providing superior leak detection with the capability of indicating where on the cassette sheeting or membrane gasket the leak has occurred. This leak detection capability is present prior to the beginning of therapy as well as during therapy. 
     The system can also tell which of the membrane gasket and the cassette sheeting has incurred a leak. If fluid is not drawn between the membrane gasket and the sheeting, the leak is in the membrane gasket. If fluid is drawn in between the membrane gasket and the sheeting, the leak is in the cassette sheeting. This can be a valuable tool, for example, in diagnosing a machine that appears to be malfunctioning. 
     The cassette interface, in an embodiment, also integrates the pneumatic manifold with the cassette interface so that air that travels from the back side of the pumping chambers of the disposable cassette to the volumetric reference chambers (one for each pump chamber, used for volumetric accuracy calculation and air) of the pneumatic manifold does not have to travel far. The close spacing also tends to make the temperature of air in the passageways, the reference chambers and the pump chambers equal. This is useful for a pneumatic pumping technique that assumes a constant temperature between air in the volumetric reference chambers and the medical fluid or dialysate pumped though the disposable cassette. The dialysate is located on the other side of the cassette sheeting from air in communication with the pneumatic source and the volumetric reference chamber. The fluid temperature needs to be about that of the human body, e.g., about 37° C. The air in the reference chamber therefore should be about 37° C. 
     The system in one embodiment provides a heater at the cassette interface, which heats the interface plate, the volumetric reference chambers and the pneumatic passageways to a single temperature to stabilize the entire pneumatic circuit at a desired temperature. The heated interface plate also enables the reference chambers to be brought to temperature more quickly, especially on cold days. A quick warm-up also saves a substantial amount of time during the calibration of the system. The interface plate in one embodiment is made entirely of metal, which can be heated. Alternatively, a cassette interface portion of the manifold, to which pneumatic control valves controlling pressure to the fluid valves are attached, is plastic. The reference chambers are metal and are provided in a module with a heating element, such as a resistive heating element. The module is affixed to the plastic interface. The interface includes pump chamber walls having a metal or thermally conductive section. Heat is thereby transferred to the pump chamber interface wall, which heats air therein. 
     It is therefore an advantage of the present disclosure to provide an improved medical fluid system, such as for APD, HD, HF, HDF and CRRT. 
     It is another advantage of the present disclosure to provide a medical fluid system having a rotatable base, making device features readily accessible. 
     Moreover, it is an advantage of the present disclosure to provide a medical fluid system that is relatively mobile and that carries the supply bags as the system is moved. 
     It is a further advantage of the present disclosure to provide a medical fluid system that positions fluid supply bags so as to tend to trap air in the bags. 
     Another advantage of the present disclosure is to provide a non-invasive temperature sensing apparatus and method. 
     It is yet a further advantage of the present disclosure to provide a disposable cassette wherein at least one of: (i) the cassette includes three pumping chambers; and (ii) the molded plastic part of the cassette is provided inside a pouch made of flexible sheeting sealed together and to tubing attached to the molded plastic part. 
     It is still another advantage of the present disclosure to provide a method and apparatus for real time measurement of fluid volume pumped. 
     Further still, it is an advantage of the present disclosure to provide a fluid management system (“FMS”), which has improved temperature control for a fluid volume measuring system using the ideal gas law. 
     Yet another advantage of the present disclosure is to provide for improved leak detection in a pneumatically actuated pumping system. 
     Still further, it is an advantage of the present disclosure to provide an improved cassette/manifold membrane gasket. 
     Yet a further advantage of the present disclosure is to provide an auto-connection mechanism for solution lines and an auto-identification mechanism to ensure that a proper solution at a proper volume for a particular supply bag will be delivered to a patient. 
     Still a further advantage of the present disclosure is to provide an improved priming technique using a dual lumen patient line and an apparatus and method for automatically connecting the dual lumen patient line to a dual port transfer set. 
     Further still, an advantage of the present disclosure is to provide an apparatus and method for automatically detecting whether a solution bag has been loaded for therapy. 
     A related advantage is to use the above bag detection apparatus and method for automatically detecting whether a multi-chamber solution bag has been opened properly so that the solution inside is mixed properly for delivery to the patient. 
     A further related advantage is that the above bag detection apparatus and method is non-invasive, maintaining the sterility of the concentrates and preserving the bag and other solution disposables. 
     Additional features and advantages are described herein, and will be apparent from, the following Detailed Description and the figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  illustrates one embodiment of a dialysis system cart with a machine holding, rotatable bearing. 
         FIG. 2  illustrates the cart of  FIG. 1 , in which the dialysis machine has been rotated to have the solution bags facing a front of the cart. 
         FIG. 3  illustrates a system using the cart of  FIG. 1 , in which the dialysis machine has been rotated to have machine controls facing a front of the cart. 
         FIGS. 4 to 9  illustrate one embodiment for a supply bag loading procedure for a bag management system of a dialysis system of the present disclosure. 
         FIG. 10  is a perspective view of one embodiment of a disposable set of the system of the present disclosure. 
         FIG. 11  is a perspective view of one embodiment of a four-to one manifold useable with the disposable set of  FIG. 10 . 
         FIG. 12  is a perspective view of one embodiment of an instrument of the system of the present disclosure, which includes an auto-connection mechanism operable with the disposable set of  FIG. 10 . 
         FIGS. 13A to 13I  are perspective views illustrating one embodiment of a supply line auto-connection sequence using the auto-connection mechanism of  FIG. 12 . 
         FIG. 14  is a perspective view of one embodiment of an auto-identification mechanism operable with the auto-connection mechanism of  FIG. 12 . 
         FIGS. 15A to 15E  illustrate one embodiment of a patient line auto-connection sequence using the auto-connection mechanism of  FIG. 12 . 
         FIG. 16  is a perspective view of one embodiment for a disposable pumping cassette having a rigid portion held in a sealed pump sheeting pouch. 
         FIGS. 17A and 17B  are front and rear views, respectively, of one embodiment of a disposable pumping cassette having three pump chambers. 
         FIG. 17C  shows one possible valve arrangement for the three pump chamber cassette of  FIGS. 17A and 17B  for achieving the pumping regimes shown in connection with  FIGS. 18A to 18C . 
         FIGS. 18A to 18C  are schematic views showing pumping sequences using the three pump chamber cassette of  FIGS. 17A and 17B . 
         FIG. 19  is a perspective view of one embodiment of a pneumatic pumping system of the present disclosure, which includes a manifold cassette interface, a membrane gasket and a disposable cassette. 
         FIG. 20  is a perspective view of a manifold cassette interface and membrane gasket of the pneumatic pumping system of  FIG. 19 . 
         FIG. 21  is a perspective view of an interface plate of the cassette interface of the pneumatic pumping system of  FIG. 19 . 
         FIG. 22  is a perspective view of a membrane gasket of the pneumatic pumping system of  FIG. 19 . 
         FIG. 23  is a perspective view of the reverse side of the interface plate of  FIG. 21 , which is metallic and can include a heating strip for heating the reference chambers formed in the interface plate. 
         FIG. 24  is a perspective view of a reverse side of an alternative manifold, which includes a plastic interface and control valve connection portion and a heated reference chamber module connected to the plastic portion. 
         FIGS. 25A and 25B  are front and rear perspective views of the plastic interface and control valve connection portion of the assembly of  FIG. 24 . 
         FIGS. 26A and 26B  are front and rear perspective views of the heated reference chamber module of the assembly of  FIG. 24 . 
         FIG. 27  is a schematic view of an embodiment of a pneumatic system for operating a real time method for determining volume of fluid moved. 
         FIGS. 28A to 28F  illustrate one embodiment of a real time method for determining volume of fluid moved. 
         FIG. 29  is a chart of real time fluid volumes calculated via the method of  FIGS. 28A to 28F . 
         FIG. 30  is a schematic flow chart illustrating an example of pneumatically actuated pumps undergoing a fill with fresh fluid phase, using the real time method discussed in connection with  FIGS. 28A to 28F , and wherein the dialysis system employs inline mixing of dextrose and bicarbonate concentrates. 
         FIG. 31  is a schematic flow chart illustrating an example of the pneumatically actuated pumps undergoing a fill with effluent (draining fluid from the patient) phase, using the real time method discussed in connection with  FIGS. 28A to 28F . 
         FIG. 32  is a schematic view of one embodiment for a non-invasive temperature sensing system and method having a temperature sensor in a first position. 
         FIG. 33  is a schematic view of one embodiment for a non-invasive temperature sensing system and method having a temperature sensor in a second position. 
         FIG. 34  is a graph comparing the results of the temperature sensing system of  FIGS. 32 and 33  versus those of an invasive temperature sensor. 
         FIG. 35  is a schematic illustration of one embodiment of an inductive solution container loading system in a “not mixed” sensing state. 
         FIG. 36  is a schematic illustration of the system embodiment of  FIG. 35  in a “mixed” sensing state. 
         FIGS. 37A to 37D  are schematic views of one embodiment of an inductive sensing system employing multiple emitters and receiving the system capable of orientation detector supply container loading. 
     
    
    
     DETAILED DESCRIPTION 
     Mobile Cart System 
     Referring now to the drawings and in particular to  FIGS. 1 to 3 , a dialysis system, such as an automated peritoneal dialysis (“APD”) system  10  is illustrated. It should be appreciated that system  10  can be used with other types of renal failure therapy systems, such as any of those maintained above. 
       FIGS. 1 to 3  illustrate that system  10  includes a mobile cart  12 , which allows the system to be moved readily, e.g., from a family room to a bedroom and vice versa. Cart  12  includes a lazy Susan-type bearing  14 , which provides ample access to the controls  22  and bag management system  30  of an instrument  20  at all times. Bag management system  30  organizes the loading of supply bags at the beginning of therapy as shown in detail herein. Lazy Susan bearing  14  in one embodiment is equipped with detents that prevent the system from rotating during operation. A cut-out or hole in the center of lazy Susan bearing  14  allows a power cord to pass through to shelves  16  of cart  12 . Lazy Susan bearing  14  can also have a total rotation limit, e.g., 360 degrees or so, to prevent damage to the power cord due to over-rotation. 
     As shown specifically in  FIG. 2 , instrument  20  can, for example, be rotated to face the patient to provide ready access to the bag management shelves of bag management system  30 . As shown specifically in  FIG. 3 , instrument  20  can then be rotated to provide optimum access to the controls  22 , display  24 , auto-connection mechanism  26  and cassette loading mechanism  28  during the set-up procedure. Also, instrument  20  can be rotated so that the display  24  and controls  22  face the patient&#39;s bed when the patient is asleep. Here, if an alarm sounds, the patient can potentially access controls  22 , drain line, supply bags lines, etc., without getting out of bed. 
     Mobile cart  12  includes shelves or drawers  16 , which hold the ancillary supplies needed for dialysis therapy. To move system  10 , the patient needs to unplug a power cord. Mobile cart  12  accommodates the drain bag, e.g., on lower shelf  16 . The self-contained drain cart allows cart  12  to be moved without having to first load the drain bag. If a drain line is run to a house drain instead of a bag, the drain line likely has to be removed from the drain and placed onto cart  12  when system  10  is moved. A handle  18  facilitates moving system  10  and in one embodiment can be rotated upwardly for movement of cart  12  and downwardly and out of the way when not needed. 
     Bag Management System 
     Referring now to  FIGS. 4 to 9 , an embodiment for bag management system  30  of dialysis system  10  is illustrated. As illustrated, bag management system  30  is connected to or made integral with instrument or cycler  20 . Bag management system  30  as illustrated is configured for four, e.g., six liter supply bags  40   a  to  40   d  (referred to herein collectively as supply bags  40  or generally, individually as supply bag  40 ). System  30  is configured alternatively to hold more or less six liter bags  40 .  FIGS. 4 to 9  also show that cycler  20  includes a hinged display  24 , which can operate with separate controls  22  and/or a touch screen overlay. 
       FIG. 4  shows bag management system  30  with each of shelves  32 ,  34 ,  36  and  38  rotated down and no supply bags  40  loaded.  FIG. 5  shows bag management system  30  with lower shelf  32  folded down and shelves  34 ,  36  and  38  rotated upwardly and out of the way to provide access to bottom shelf  32 . In an embodiment, the shelves are configured in a cascading or telescoping manner such that third shelf  36  can fold or rotate into upper shelf  38 , second shelf  34  can fold or rotate into third shelf  36  and lower shelf  32  can fold or rotate into second shelf  34 . The hinges of the shelves can have releasably interlocking apparatuses (e.g., mating tabs and detents) that hold the shelves releasably in place when folded or rotated upwardly. Alternatively or additionally, the shelves can releasably lock one to another, e.g., third shelf  36  locking to upper shelf  38 , second shelf  34  locking to third shelf  36 , and so on. For example, interlocking tabs and detents  42  and  44 , respectively, are provided at the sides or gussets of the shelves so that the locking mechanisms  42  and  44  do not interfere with the bags  40  when loaded. 
       FIG. 6  shows bag management system  30  with lower shelf  32  folded down, a first supply bag  40   a  loaded onto lower shelf  32 , and shelves  34 ,  36  and  38  hinged upwardly and out of the way.  FIG. 7  shows bag management system  30  with lower shelf  32  and second shelf  34  folded down, first supply bag  40   a  loaded onto lower shelf  32 , a second supply bag  40   b  loaded onto second shelf  34 , and shelves  36  and  38  hinged upwardly and out of the way. 
       FIG. 8  shows bag management system  30  with lower shelf  32 , second shelf  34  and third shelf  36  folded down, first supply bag  40   a  loaded onto lower shelf  32 , second supply bag  40   b  loaded onto second shelf  34 , a third supply bag  40   c  loaded onto third shelf  36 , and shelve  38  hinged upwardly and out of the way.  FIG. 9  shows bag management system  30  with lower shelf  32 , second shelf  34 , third shelf  36  and top shelf  38  all folded down, first supply bag  40   a  loaded onto lower shelf  32 , second supply bag  40   b  loaded onto second shelf  34 , third supply bag  40   c  loaded onto third shelf  36 , and fourth supply bag  40   d  loaded onto top shelf  38 . 
     Each tray in the bag management system  30  folds up providing easy access to the shelf below. When used with cart  12  above, system  30  minimizes the height to which patients have to lift the solution bags. The shelf holds solution bags  40  elevationally above a heater, which can be located at the bottom of instrument  12  for example, and orients the bag so that the bag outlet port resides below the rest of the bag. The configuration causes dialysis fluid to flow from the bags until empty, leaving any air trapped in the empty bags. This shelf configuration, bag placement and orientation can enhance the volumetric pumping speed and accuracy of the fluid delivery pumps when fluid is pumped directly from the supply bags, e.g., through an inline heater, and into the patient since air does not flow downhill, e.g., from a bag  40  into a pumping chamber of cassette  28 . 
     One or more or all of shelves  32  to  38  can employ a sensor operable with a sensing system stored in memory. The sensor and associated system perform multiple functions. One function is to determine if a dual chamber or multiple chamber bag has been opened to allow two or more concentrates to mix to form a dialysis fluid that can be pumped to the patient. Sensing a properly opened bag can be a prerequisite for the pumps and/or valves or occludes to operate. The sensors can also detect which shelves  32  to  38  have bags and which do not and thus whether enough fluid has or can be connected. One suitable sensor and associated system is found in copending patent application Ser. No. 11/773,501, filed Jul. 5, 2007, entitled, “Apparatus and Method For Verifying A Seal Between Multiple Chambers”, assigned for the eventual assignee of the present disclosure, the entire contents of which are hereby incorporated by reference and relied upon. An alternative inductive sensing apparatus and method is discussed below beginning at  FIG. 35 . 
     Disposable Set 
     Referring now to  FIGS. 10 and 11 , an embodiment of a disposable set  50  for system  10  is illustrated.  FIG. 10  illustrates that disposable set  50  includes disposable cassette  28  and supply bags  40  as discussed above. Bags  40  in an embodiment each include a solution line or pigtail  46   a  to  46   d  (referred to herein collectively as pigtails  46  or generally, individually as pigtail  46 ), which connect to a first set of supply lines  48   a . Solution lines or pigtails  46  in one embodiment terminate in female connectors  56  protected by tip protector  66   a . Connectors  56  in one embodiment are female connectors protected by a pierceable cover. Disposable set  50  can include a second set of supply lines  48   b  for a high-volume therapy as discussed below. First and second supply line sets,  48   a  and  48   b  respectively, each include multiple lines ending in a connector  58  protected by a tip protector  66   b . Connectors  58  can be male spike connectors that spike through the protective covers of female connectors  56  of bag lines  46 . 
     Disposable set  50  also includes a patient line  52  and drain line  54 . Patient line  52  can be a dual lumen line in which one line terminates in a pierceably sealed female connector  56  protected by a tip protector  66   a  and the other line terminates in a spike connector  58  protected by a tip protector  66   b  (see  FIGS. 15A to 15D ). Drain line terminates in one embodiment with a spike receptacle less a septum, so that a supply bag cannot be connected to the drain line. 
     Pigtails  46  in one embodiment terminate in female connectors  56  protected by tip protector  66   a . Connectors  56 /tip protectors  66   a  are held together in a single organizer in one embodiment. Patient line  52  can be a single lumen patient line (batch dialysis) or a dual lumen patient line (for batch or continuous dialysis) as desired. The first set of supply lines  48   a , patient line  52  and drain line  54  are each connected to cassette  28 . 
       FIG. 10  further illustrates one embodiment for a high volume disposable set (e.g., eight bags), which is provided by teeing a second set of supply lines  48   b  off of the first set of supply lines  48   a  (connected to cassette  28 ) and providing an organizer for holding four spike connectors  58  on the end of each supply line  48   a  or  48   b . The spikes and organizers can be integrated into a single molded spike bundle that contains the spikes and features for gripping and holding the bundle during set up and operation. Each spike connector  58  of each supply line can connect fluidly and sealingly with a female connector  56  at the end of each supply bag pigtail  46 . As mentioned, each spike connector  58  is protected by its own tip protector  66   b . Line clamps  62  are provided on the first set of supply lines  48   a . The clamps can be used to occlude the first set of supply lines  48   a  before an auto-connection mechanism (discussed below) disconnects connectors  58  of the first set of supply lines  48   a  from connectors  56  at the end of pigtails  46 . The auto-connection mechanism can then connect the second set of supply lines  48   b  to a second set of supply bags  40  (not illustrated). 
       FIG. 11  illustrates a second embodiment for producing a high-volume disposable set  50 . Here, the first set of supply tubes  48   a  is converted to a high volume set via four-to-one manifold  60 . Four-to-one manifold  60  in one embodiment has at one end the same organizer holding four lines  48   c  terminating in spike connectors  58 /tip protectors  66   b  as that described above for the supply lines  48   a  and  48   b . Manifold  60  can therefore itself be connected to up to four supply bags  40 . A connector  56 /tip protector  66   a  of a single input line  64  from four-to-one manifold  60  is then inserted into the auto-connection mechanism (described below) in lieu of the connector  56 /tip protector  66   a  at the end of pigtail  46  of a single supply bag  40 . An auto-identification system described below automatically tracks the number of bags connected to each four-to-one manifold  60  and the volume of the solution that has been connected. Disposable set  50  using manifold  60  can operate with up to sixteen, e.g., six liter, bags of solution. 
     Auto-Connection 
     Referring now to  FIG. 12 , instrument  20  in an embodiment includes pinch clamps or pinch valves  68   a  to  68   d  (referred to collectively herein as valves  68  or individually as valve  68 ), one valve  68  for each pigtail  46   a  to  46   d  of supply bags  40   a  to  40   d , respectively (or manifold line  64  of four-to-one manifold  60 ). Valves  68   a  to  68   d  are positioned to hold and occlude pigtails  46   a  to  46   d , respectively, when (i) connectors  56  at the end of the pigtails  46  are attached to a stationary connector holder  70  and (ii) the tip protectors  66   a  protecting each connector  56  are attached initially to a tip protector removal carriage  72  of the auto-connection mechanism. Tip protector removal carriage  72  is also configured to remove spike connector  58  tip protectors  66   b  as shown below. Valves  68  are opened, e.g., sequentially, to allow fluid to be withdrawn sequentially from supply bags  40 . Valves  68  in an embodiment are closed automatically if there is a need to reload cassette  28  after supply bags  40  have been connected. Stationary holder  70  holds supply bag pigtail connectors  56  stationary during the auto-connection process. 
       FIG. 12  also illustrates a moveable connection carriage  74 , which holds the organized spike connectors  58 /tip protectors  66   b  at the end of supply lines  48   a  connected to cassette  28 . The individual holders of stationary holder  70  and moveable carriages  72  and  74  are aligned in the Z-direction as shown by the coordinate system in  FIG. 12 . 
     Moveable carriage  72  moves in the +X and −X directions to remove tip protectors  66   a  from connectors  56  and tip protectors  66   b  from spike connectors  58 . Moveable carriage  72  also moves in the +Y and −Y directions to pull the removed tip protectors  66   a  and  66   b  out of the way for line connection and possibly to reload the tip protectors. Moveable carriage  72  in an embodiment uses an XY gantry system, which includes a pair of lead screws each driven by a motor, such as a stepper motor. For example, moveable carriage  72  can be threaded and receive a ball screw supported on two ends by bearings and driven by a stepper motor to move carriage  72  back and forth in a precise manner in the +X and −X directions. That X-direction assembly can in turn be threaded, e.g., at a bearing support, and receive a ball screw supported on two ends by bearings and driven by a stepper motor to move the X-direction assembly (including carriage  72 ) back and forth in a precise manner in the +Y and −Y directions. 
     Moveable carriage  74  moves in the +X and −X directions to push spike connectors  58  of cassette supply lines  48   a  into sealed communication with pierceably sealed female connectors  56  of bag pigtails  46 . Here, moveable carriage  74  can be threaded and receive a ball screw supported on two ends by bearings and driven by a stepper motor to move carriage  74  back and forth in a precise manner in the +X and −X directions. 
     System  10  is computer controlled and can for example include master processing and memory operating with delegate controllers including delegate processing and memory. Master processor and memory can also operate with a safety controller having safety processing and memory. In one embodiment, master processing and memory operates with a delegate motion controller having processing and memory (e.g., programmable or via an application specific integrated circuit (“ASIC”)), which outputs to the stepper motors and receives inputs, e.g., positional inputs from position sensors. 
     Referring now to  FIGS. 13A to 13J , an auto-connection sequence for the sealed mating of connectors  56  of pigtails  46  of supply bags  40  to the spike connectors  58  of the supply lines of set  48   a  (alternatively supply line set  48   b  and  48   c  as discussed above) of cassette  28  is illustrated. In  FIG. 13A , an organizer holding four spike connectors  58 /tip protectors  66   b  of cassette supply line set  48   a  connected to cassette  28  are loaded into the group holder of moveable carriage  74 . Alternately, an integrated four-spike bundle with connectors  58 /tip protectors  66   b  is loaded into the group holder of moveable carriage  74 . In this step, cassette  28  is also loaded into instrument  20  (see  FIGS. 2 and 3 ). 
     In  FIG. 13B , connectors  56 /tip protectors  66   a  located at the end of four supply bag pigtails  46  are loaded into individual holders of stationary holder  70  and moveable carriage  72 . In particular, connectors  56  are loaded into individual holders of stationary holder  70  and tip protectors  66   a  are loaded moveable carriage  72 . Thus in  FIG. 13B , tip protectors  66   a  and  66   b  are set to be removed automatically from connectors  56 . 
     After spike connectors  58 /tip protectors  66   b  and connectors  56 /tip protectors  66   a  have been loaded into the auto-connection mechanism, a cover or door is closed (not illustrated), isolating holder  70 , carriages  72  and  74 , spike connectors  58 /tip protectors  66   b  and female connectors  56 /tip protectors  66   a  from the environment. System  10  then injects filtered high-efficiency-particulate-air (“HEPA”) or ultra-low-penetration-air (“ULPA”) into the sealed compartment to reduce the bioburden in the region prior to tip protector removal from connectors  56  and  58 . Pneumatic control of HEPA or ULPA air can be located on the motion controller mentioned above or on a separate pneumatic controller operating with the master controller. 
     The imaging system determines which supply bags have been loaded (quantity, size, solution type, expiration date, lot code, etc.) and alerts the user if a problem arises with any of the above identifiers. For example, the solution volume may be insufficient to perform the selected therapy. Alternatively, a connector may be distorted or damaged so that it will not connect properly. 
     In  FIG. 13C , moveable carriage  72  moves in the −X direction (according to coordinate system of  FIG. 12 ) to remove pre-loaded tip protectors  66   a  from supply bag connectors  56 . 
     In  FIG. 13D , moveable carriage  72  moves further in the −X direction (according to coordinate system of  FIG. 12 ) to lock tip protectors  66   b  to protecting spike connectors  58 . 
     In  FIG. 13E , moveable carriage  72  moves in the +X direction (according to coordinate system of  FIG. 12 ) to remove tip protectors  66   b  from spike connectors  58 . 
     In  FIG. 13F , moveable carriage  72  moves in the +Y direction (according to coordinate system of  FIG. 12 ) to move out of the way of supply bag connectors  56  and spike connectors  58 . 
     In  FIG. 13G , moveable carriage  74  moves in the +X direction (according to coordinate system of  FIG. 12 ) towards stationary holder  70  to push spike connectors  58  into pierceably-sealed supply bag connectors  56  and to fluidly connect supply bag  40  to cassette  28 . After the connections of spike connectors  58  to supply bag connectors  56  have been made, an imaging system described below verifies that the connections have been made properly and that no leaks are present. 
       FIG. 13H (a) shows one removal embodiment in which a connected supply of set lines  48   a  and solution lines or pigtails  46  and associated empty supply bags  40  and cassette  28  are removed from carriage  74  and holder  70 , respectively, together. In  FIG. 13I , moveable carriage  72  is then moved in the −Y direction ( FIG. 12 ) to allow the consumed tip protectors  66   a  and  66   b  to be retrieved. 
       FIG. 13H (b) shows another removal embodiment in which moveable carriage  74  moves in the −X direction to pull connectors  56  and  58  apart, after which moveable carriage  72  moves in the −Y direction (according to coordinate system of  FIG. 12 ) and then back and forth in the +and −X directions to reattach tip protectors  66   a  and  66   b  to connectors  56  and  58 , respectively, allowing supply lines of set  48   a , pigtails  46  and associated supply bags  40  and cassette  28  to be removed from carriages  72  and  74  and holder  70 , respectively. This latter removal method is preferable if it is common that the supply bags will not be completely empty when the bags have to be removed. 
     Auto-Identification 
       FIG. 14  illustrates one embodiment for an auto-identification system. The system includes a color-capture device (“CCD”) camera  80 , which uses a charge-coupled device image sensor and an integrated circuit containing an array of linked, or coupled, light-sensitive capacitors. Other cameras that create a three-dimensional image of a connection area shown in  FIG. 14  may be used alternatively. The auto-identification system uses the image from camera  80  to determine characteristics of solution bags  40  and to verify that the correct, undamaged connectors  56  and  58  are loaded into the mechanism. 
     The auto-identification system accomplishes solution identification via a character recognition routine (located for example on the motion controller or a separate video controller operable with the central processing unit or master controller) that “reads” the codes printed on the pigtail connectors  56  connected to supply bags  40 . The “codes” provide (i) solution type, e.g., glucose or bicarbonate concentrate or premixed dialysate, (ii) bag volume, e.g., six liters, and (iii) number of bags per connector  56 , e.g., single bag or multiple bags via four-to-one manifold  60 . The image of each connector  56  is compared against stored images of the range of acceptable geometries for connector  56 . A deformed connector, or a connector that has been loaded incorrectly, or that does not match therapy prescription will fall outside of a range of acceptable geometries and cause system  10  to signal an alarm and cause other appropriate action, e.g., closing clamps  68  or not allowing them to be opened until the alarm is cleared. The imaging system also verifies that the “connected” joints fall within an acceptable range of geometries for a good joint connection. If a joint leaks and droplets form, the imaging system sees the droplets and causes an alarm. 
     Priming 
     In an embodiment, a dual lumen patient line  52  ( FIG. 10 ) is used. One lumen is connected to a patient-drain port through a pumping chamber of disposable cassette  28 . The other lumen is connected to a patient-fill port through a different pumping chamber of the disposable cassette  28 . During priming of the patient line, the two lumens of the patient line are connected together. Cycler  20  causes one of the diaphragm pumps of cassette  28  to pump or push fresh fluid out the patient-fill port on the disposable cassette  28 , down one lumen of patient line  52 , until it reaches the end of the patient line. The fresh fluid is then pumped back up the other lumen of patient line  52 , into cassette  28  through the patient-drain port and into another diaphragm pump of cassette  28 , which removes air that the fluid pushes through the patient line  52 . When fluid fills the second pump chamber, the patient line is fully primed. 
     Patient Connection/Disconnection 
     Primed dual lumen patient line (with fill lumen  52   a  and drain lumen  52   b  connected) and transfer set  82  (with fill line  84  and drain line  86  connected) are loaded into a patient line auto-connection device  90 , as illustrated in  FIGS. 15A to 15E . Device  90  can be separate from or integrated into instrument  20 . Instrument  20  or cart  12  in an embodiment provides an area and apparatus for storing device  90 . Device  90  can be powered or configured for manual or manual/automatic operation. Device  90  includes a stationary portion  92  and a portion  94 , which is rotatable and translatable with respect to stationary portion  92 . 
     As seen in  FIG. 15E , device  90  includes a cover  91  and base  93  which mate (e.g., hingedly or separately) to enclose connectors  56  (with pierceable membrane) and  58  (spike) of lumens  52   a  and  52   b  and lines  84  and  86  when loaded into portions  92  and  94 . Cover  91  and base  93  can be plastic or metal as desired.  FIG. 15E  also illustrates that device  90  includes one or more motor  95  having an output shaft  97  connected operably to portion  94  to move (e.g., to rotate and/or translate) portion  94  relative to portion  92 , which is generally stationary. For example, output shaft  97  of motor  95  can drive a ball screw that in turn is connected threadingly to portion  94 , which enables motor  95  to translate portion  94 . In the illustrated embodiment, output shaft  97  of motor  95  is coupled to portion  94  in a manner such that motor  95  can rotate portion  94 . A lever  99  is connected to the subassembly of motor  95  and moveable portion  94 , such that the patient or caregiver can translate portion  94  back and forth with respect to stationary portion  92  via lever  99 . Device  90  is alternatively fully automatic (e.g., AC or battery powered) or fully manual. 
     Device  90  also includes an apparatus for maintaining an aseptic environment when lumens  52   a  and  52   b  and lines  84  and  86  are pulled apart. For example, device  90  can employ an ultraviolet (“UV”) light or radiator described in U.S. Pat. Nos. 4,412,834 and 4,503,333, owned by the eventual assignee of the present application, the entire contents of which are incorporated herein by reference. Device  90  can also introduce HEPA or ULPA filtered air into the volume around the connector prior to connection. 
     Referring additionally to  FIGS. 15A to 15D , once the dual lumen patient line  52  and transfer set  82  are loaded into device  90 , the patient line shown here as having fill lumen  52   a  (terminating in a female connector  56  as described above) and drain lumen  52   b  (terminating in a spike connector  58  as described above) are split apart and connected to the patient&#39;s transfer set  82 . Transfer set  82  includes a fill line  84  (terminating in a spike connector  58 ) and a drain line  86  (terminating in a female connector  56 ). 
     In  FIG. 15A , fill lumen  52   a  is connected via the prime sequence to drain lumen  52   b . Fill line  84  and drain line  86  or transfer set  82  are also connected. Mated connectors  56  and  58  of each pair are loaded into device  90 , such that return lumen  52   b  and fill line  84  (both having spike connectors  58 ) are loaded into stationary portion  92  of device  90  and fill lumen  52   a  and drain line  86  (both having female connectors  56 ) are loaded into rotatable portion  94  of device  90 . In one embodiment portions  92  and  94  are structured such that portion  92  can only accept spike connectors  58  and portion  94  can only accept female connectors  56 . Cover  91  of device  90  is closed and the aseptic apparatus is initiated or energized. 
     In  FIG. 15B , portion  94  via, e.g., electrically actuated stepper motor  95  coupled to a ball screw (not illustrated), or solenoid (not illustrated), pulls lumens  52   a  and  52   b  and lines  84  and  86  apart, respectively. Portion  90  includes a carriage holding connectors  56  of lumen  52   a  and line  86 , which are pulled apart from spike connectors  58 . Translatable portion  94  and motor  95  can be housed completely within device  90  and sealed from the outside environment. 
     In the illustrated embodiment, the translator is operated manually via lever  99  that the patient grabs and translates to translate portion  94  carrying connectors  56  of lumen  52   a  and line  86  towards/away from spike connectors  58 . In the illustrated embodiment, a thinner shaft of lever  99  is sealed to device  90 , such that the handle portion of lever  99  remains outside device  90  and is configured for the patient to grasp and move comfortably. The shaft of lever  99  is connected to motor  95 , which in turn is coupled to portion  94  holding connectors  56  of lumen  52   a  and line  86 . 
     In  FIG. 15B , the aseptic apparatus of device  90  continues to be energized to prevent the tips of connectors  56  and  58  from becoming contaminated. 
     In  FIG. 15C , motor  95  rotates rotatable portion  94  holding female connectors  56  one-hundred-eighty degrees relative to stationary portion  92 , such that return lumen  52   b  of dual lumen patient line  52  is aligned with drain line  86  of transfer set  82 . Also in this configuration, fill lumen  52   a  of dual lumen patient line  52  is aligned with fill line  84  of transfer set  82 . The aseptic apparatus of device  90  continues to be energized to prevent the tips of connectors  56  and  58  from becoming contaminated. 
     In  FIG. 15D , translatable portion  94  (electric or manual) pushes fill lumen  52   a  of dual lumen patient line  52  towards fill line  84  of transfer set  82 , connecting spike connector  58  to female connector  56 . Simultaneously, return lumen  52   b  of dual lumen patient line  52  is connected sealingly and operably with drain line  86  of transfer set  82 . System  10  can now perform an initial patient drain to remove the prior procedure&#39;s spent last-bag fill and ready the patient for a first fill of the present therapy. 
     It should be appreciated that the sequence of  FIGS. 15A to 15D  works no matter which side  96  or  98  of device  90  connected lumens  52   a  and  52   b  and connected lines  84  and  86  are loaded in  FIG. 15A . 
     In a patient disconnection sequence, connected inflow lines  52   a  and  84  are loaded into one side  96  or  98  of device  90 . Connected outflow lines  52   b  and  86  are loaded into the other side of device  90 . In a next step, device  90  (manually or automatically) disconnects cassette inflow line  52   a  from transfer set inflow line  84  and cassette outflow line  52   b  from transfer set outflow line  86 . 
     Next, rotatable portion  94  holding female connectors  56  is rotated one-hundred-eighty degrees relative to stationary portion  92 , such that now return lumen  52   b  of dual lumen patient line  52  is aligned with fill lumen  52   a  of dual lumen patient line  52 , and drain line  86  of transfer set  82  is now aligned with fill line  84  of transfer set  82 . 
     In a next step, device  90  (manually or automatically) connects cassette inflow line  52   a  to cassette outflow line  52   b  and transfer set inflow line  84  to transfer set outflow line  86 . Device  90  provides an aseptic environment for the above four steps. The patient can then remove the connected dual lumen line  52  and transfer set  82  from device  90  and is free from the dialysis instrument. 
     It should be appreciated that device  90  is not limited to the dual lumen patient line  52 /transfer set  82  connection/disconnection application just described or even to APD. For example, a single patient line  84  having a spike connector  58  protected by a female cap  56  could be loaded instead into side  98  of device  90 , while a supply bag pigtail  46  having a female pierceable connector  56  and a cap is loaded into side  96  of device  90 . The female cap  56  is next removed from male-ended patient line  84 , while a cap is removed from female-ended supply pigtail  46  simultaneously from its cap (by pulling rotatable portion  94  away from portion  92 ). Next, rotatable portion  94  is rotated with respect to portion  92 . Afterwards, female portion  94  is slid towards portion  92 , mating spike connector  58  of patient line  84  with female connector  56  of supply bag pigtail  46 , thus connecting a supply bag  40  to the patient, for example for CAPD. A similar connection could be made connecting the patient to pumping cassette  28 . 
     Patient Drain and Fill 
     During patient drain, system  10  removes effluent from the patient through return lumen  52   b  of dual lumen patient line  52 . When drain is completed and system  10  advances to a fill cycle, system  10  delivers fresh fluid to the patient through fill lumen  52   a  of dual lumen patient line  52 . Here, the only effluent that is “recirculated” back to the patient is the small volume of effluent in fill line  84  of transfer set  82  and the patient&#39;s catheter. Even this volume need not be recirculated to the patient if a dual lumen catheter and transfer set is used. Further, if a dual lumen catheter and dual lumen transfer set is used with system  10 , system  10  can perform a multiple pass continuous flow peritoneal dialysis (“CFPD”) therapy. The multiple pass CFPD therapy can employ a single fill, with a long recirculating flow dwell, or the CFPD therapy can be tidal in nature and recirculate flow during at least one of the dwell periods. 
     Cassette Improvements 
     Referring now to  FIG. 16 , cassette  100  illustrates one embodiment of a cassette and method of making same, in which a rigid plastic portion  110  of the cassette is encapsulated within cassette sheeting  102 . However, sheeting  102  is not welded to the sides of the rigid portion  110 , sheeting  102  is instead welded to itself. Plastic portion  110  in one embodiment is rigid and made of acrylonitrile butadiene styrene (“ABS”), acrylic, polyolefin, polycarbonate, polyethylene or polypropylene. Sheeting  102  in one embodiment is flexible, e.g., for flexing to pump liquid, and opening and closing valve chambers. Sheeting  102  can be made of polyvinyl chloride (“PVC”), polyethylene, kraton or polyolefin. Also, two or more plies of the different or same materials can be used, wherein the grains of the plies can flow perpendicular to each other to increase strength and minimize the potential for slits, holes and tears. For example, the outside layer opposite the cassette can have good abrasion, puncture and tear resistant properties and a middle layer having good strength properties. 
     Sheeting  102  is folded to produce a first side  104   a , a second side  104   b , a folded top  106  and edges  108   a  to  108   c  as illustrated. Folded sheet  102  is slid over rigid portion  110  as shown in  FIG. 16 . Next, side edges  108   a  of sides  104   a  and  104   b  are welded together and around supply lines  48 , patient lines  52  or drain line  54 . Alternatively, edges  108   a  of sides  104   a  and  104   b  are welded together and around ports extending from rigid portion  110  (not seen in  FIG. 16 ), to which supply lines  48 , patient lines  52  or drain line  54  are fitted sealingly. Bottom edges  108   b  of sides  104   a  and  104   b  are welded together. Side edges  108   c  of sides  104   a  and  104   b  are welded together. Flexible sheeting  102  in this manner forms a sealed pouch around rigid portion  110 . Sides  104   a  and  104   b  are alternatively separate sheets welded together along four sides. 
     Rigid portion  110  includes or forms pump chambers  112 . As described below, an alternative cassette includes three pump chambers. Rigid portion  110  in the illustrated embodiment also includes a plurality of valve chambers  114 . Pump chambers  112  and valve chambers  114  each include ridges  116  defining the respective pump or valve chamber, which extend outwardly from a base wall  118  of rigid portion  110 . The opposite side of rigid portion includes ridges  116  extending in the other direction from base wall  118  and defining flow paths (not seen) that communicate with the pump chambers  112  and valve cambers  114 . 
     In operation, side  104   a  of sheeting  102  needs to be sealed to ridges  116  of the pump and valve chambers for the pneumatic movement and control of fluid. A dialysis instrument operating with pouch cassette  100 , which has sheeting  102  sealed to itself around rigid portion  110  (and to the tubes as discussed above) but not directly to raised ridges  116 , applies a positive pressure across the surface  104   a  relative to rigid portion  110 . The positive pressure seals surface  104   a  to the raised ridges  116  temporarily during operation so that pumps  112  and valves  114  can function properly. Positive pressure is also provided on reverse surface  104   b  of sheeting  102  to compress surface  104   b  to raised ridges  116  of the flow paths (not seen). The positive pressure can be provided pneumatically, e.g., via an inflatable bladder, and/or mechanically, e.g., via spring biasing, solenoid actuation and/or the closing of a door behind which cassette  100  is loaded. 
       FIG. 16  also shows that base wall  118  can include instrument loading and locating holes  120 , which enable a locating guide  122  to be snapped in place after sheeting  102  has been welded to itself and to tubing  48 ,  52  and  54 . In an embodiment, sheeting  102  is welded via a heat seal process, which uses a die. That same die can also punch aligning holes  124  through sheeting  102  to facilitate the installation of the loading/locating guide  122 . 
     Cassette  100  includes integrated valve ports  114 . System  10  of  FIGS. 1 to 3  and instrument  20  of  FIG. 12  show pinch valves  68  external to the cassette, which occlude associated tubing. Pinch valves  68  allow system  10  to access each of the supply lines independently but also to eliminate the need for the manual clamps that are typically present on cassette supply lines  48 . Machine  20 , not the user, occludes supply lines  48  when it is necessary to do so, for example when bag connections are made and opened to perform the therapy. Supply lines  48  also need to be occluded after many alarm/failure conditions or if the power fails. 
     The pinch valves  68  also aid in the drawing of fluid from the solution lines  46 . For example, the pinch valve  68  to only the top shelf  38  can be opened, allowing bag  40   d  to drain partially, e.g., more than 50%, before opening valve  68  to supply bag  40   c  on the second-to-top shelf  36  allowing bag  40   c  to drain partially, e.g., more than 50%, before opening valve  68  to supply bag  40   b  on the third-to-top shelf  34 , allowing bag  40   b  to drain partially, e.g., more than 50%, before opening valve  68  to supply bag  40   a  on bottom shelf  32 . Fluid will flow via gravity into the pumps and air will tend to float to the back of each bag  40 . Using this sequence, all of supply bags  40  can be emptied without sucking any air into the solution lines  46 . If all supply lines  48  are opened at once, lower bags  40   a  and  40   b  will become bloated due to the weight of fluid from the upper supply bags  40   c  and  40   d.    
     It should be appreciated that flexible pouch cassette  100  can include valve chambers  114  or not include valve chambers  114  if the above described pinch valves  68  are used instead. Further, it should be appreciated that the apparatuses and methods disclosed in connection with system  10  and instrument  20  are not limited to use with pinch valves  68  and instead can be used with valve chambers  114  discussed above. Further alternatively, system  10  can operate with a combination of valve chambers  114  and pinch valves  68 , e.g., using cassette-based valve chambers  114  during treatment and pinch valves  68  during setup and alarm conditions. 
     Referring now to  FIGS. 17A, 17B , cassette  130  illustrates one embodiment of a three pump chamber disposable pumping and valving cassette.  FIGS. 18A to 18C  illustrate three methods for operating the three pump chambers to achieve desired outputs. 
     Cassette  130  in the illustrated embodiment includes many of the same structures or types of structures as cassette  100 , such as rigid portion  110  having a base wall  118  with ridges  116  extending from the base wall  118  to form pump chambers  112   a  to  112   c  (referred to herein collectively as chambers  112  or generally, individually as chamber  112 ). Ridges  116  also define valve chambers  114  as described above. Alternatively, cassette  130  with three valve chambers  112  operates with pinch valves  68  and does not use or provide valve chambers  114 . 
       FIG. 17B  illustrates the back side of cassette  130 . Here, ridges  116  extending from base wall  118  define a flow path  132 . Flow path  132  includes manifold sections  134   a  and  134   b  and baffled sections  136   a  to  136   f  extending between manifold sections  134   a  and  134   b . Manifold sections  134   a  and  134   b  and baffled sections  136   a  to  136   f  of flow path  132  enable cross-talk between pump chambers  112 , so that the flow patterns discussed below in connection with  FIGS. 18A to 18C  can be achieved as shown in more detail below in connection with  FIG. 17C . 
     Cassette  130  includes flexible sheeting  104   a  and  104   b  as discussed above. Sheeting  104   a  and  104   b  can be separate sheets welded or bonded to the sides of rigid portion  110  and ridges  116  of pump chambers  112  and valve chambers  114 . Alternatively, sheeting  104   a  and  104   b  is provided via a single sheet  102  shown above, which includes a folded edge  106  and welded or bonded edges  108   a  to  108   c  as shown and described in connection with  FIG. 16 . 
       FIG. 17C  illustrates one possible valve arrangement for the three pump cassette  130  of  FIGS. 17A and 17B .  FIG. 17C  illustrates the ports extending out the bottom of cassette  130 , which is one preferable arrangement for air handling because any air in cassette  130  will tend to rise to the top of the cassette, leaving only fluid to exit the cassette from the bottom. Boxes marked “A” are areas of cassette  130  that interact with air sensors located within instrument  20 . Boxes marked “T” are areas of cassette  130  that interact with temperature sensors located within instrument  20 . The Box marked “C” is an area of cassette  130  that interacts with a conductivity sensor located within instrument  20 . 
     As illustrated, cassette  130  includes six supply ports, a dedicated to-patient port, a to/from-patient port, a drain port, and an additional port for mixing, further supplying, or sending or receiving fluid from a batch heater. Cassette  130  includes three pump chambers  112   a  to  112   c  described above. Valves  114  in  FIGS. 17A and 17B  are differentiated via valves V 1  to V 28 . The following valve states are merely examples showing different flow regimes achievable via cassette  130 . 
     Filling the patient with a premixed solution can for example occur by allowing fresh mixed solution into cassette  130  via valve V 16 , flowing through the heater via valve V 1  into pump chamber  112   c . At the same time, pump chamber  112   b  pushes the same fluid to patient via open valves V 10 , V 15 , V 27  and the to/from patient port valve. In this regime, to-patient port and valve are not needed. At the same time, pump chamber  112   c  can be performing a volume measuring determination as discussed below. In an alternative embodiment, dedicated to-patient port and valve are used as a second outlet to the patient. 
     Draining effluent from the patient can for example occur by allowing effluent into cassette  130  via to/from patient valve and port, flowing through valves V 26  and V 12  into pump chamber  112   a . At the same time, pump chamber  112   b  pushes the effluent to drain via open valves V 4  and the drain valve. In this regime, dedicated to-patient port and valve are not needed. At the same time, pump chamber  112   a  can be performing a volume measuring determination as discussed below. In an alternative embodiment, temperature sensor access valve V 15  can be opened simultaneously to allow temperature of the effluent entering chamber  112   a  to be sensed. 
     In a concentrate mixing regime, chamber  112   c  can be filling from concentrate supply  1  through valves V 17  and V 7 . Chamber  112   b  can be filling from concentrate supply  2  through valves V 20  and V 9 . Chamber  112   a , here acting as an accumulator as described below in  FIG. 18C , outputs mixed concentrates via valves V 5  and V 16  to a mixer, for example. In an alternative embodiment, a separate mixer is not used, the length of the patient line is sufficient to mix the concentrates, and chamber  112   a  outputs alternatively through valves V 5 , V 28 , V 27  and the to/from patient valve collectively to the patient. 
     In a second stroke as described below in  FIG. 18C , chambers  112   c  and  112   b  empty half of their respective concentrates through valves V 1  and V 3 , respectively and V 5  collectively into chamber  112   a . At the same time, chambers  112   c  and  112   b  empty the other half of their respective concentrates through valves V 1  and V 3 , respectively and valve V 16  collectively to a mixer. In an alternative embodiment, a separate mixer is not used, the length of the patient line is sufficient to mix the concentrates, and chambers  112   c  and  112   b  empty the other half of their respective concentrates alternatively through valves V 1  and V 3 , respectively and valves V 28 , V 27  and the to/from patient valve collectively to the patient. 
     In a multi-pass flow regime, chamber  112   c  fills with fresh, e.g., premixed, solution from supply  1  through valves V 17  and V 7 . At the same time, chamber  112   b  empties fresh solution to the patient via valves V 3 , V 28  and the to-patient valve to the patient. At the same time, chamber  112   a  fills with effluent from the patient via the to/from patient valve, and valves V 26  and V 12 . Here, the fluid can be recirculating because there is no net fluid loss or ultrafiltration (“UF”) taking place. 
     In a UF to drain mode multi-pass flow example, chamber  112   c  empties fresh solution to the patient via valves V 1 , V 28  and the to-patient valve to the patient. At the same time chamber  112   b  fills with effluent from the patient through the to/from patient valve, and valves V 26  and V 10 . At the same time, chamber  112   a  empties effluent to drain via valve V 6  and the drain valve. In an alternative UF t-e bag to bag multi-pass mode, chamber  112   a  alternatively empties effluent to an empty supply bag, e.g., supply  3  via valves V 11 , V 24  and V 25 . 
     In a second state of the UF bag to bag multi-pass mode, chamber  112   c  fills with fresh, e.g., premixed, solution from supply  1  through valves V 17  and V 7 . At the same time, chamber  112   b  empties fresh solution to the patient via valves V 3 , V 28  and the to-patient valve to the patient. At the same time, chamber  112   a  fills with effluent from the patient via the to/from patient valve, and valves V 26  and V 12 . 
     A test can be run to see if a dual or multi-chamber bag has been opened properly. Here one of pump chambers empties fluid to drain, flowing the fluid past conductivity sensor (“C”), which checks to see if the conductivity measured is indicative of a properly mixed solution, in which case therapy can proceed, and an improperly mixed case in which an alarm is generated. 
       FIG. 18A  illustrates one pumping sequence for pump chambers  112  in which a chamber fill stroke (cross-hatched segments) is slightly shorter in duration than a chamber empty stroke (diagonal segments), which are separated by relatively short fluid measurement periods (dotted segments). A fluid measurement (amount of fluid pumped) method is discussed in detail below. Also discussed below is a way to eliminate the fluid measurement periods (dotted segments) occurring after the chamber empty strokes (diagonal segments). 
     In one embodiment, a pneumatic actuator applies negative and positive pressure to sheet  104   a  to pump fluid into or out of one of pump chambers  112 . A pump controller, e.g., microprocessor and computer program memory, controls pneumatic actuators to apply positive, negative or no pressure to the appropriate chamber  112  at the appropriate time. The processor cycles through a program which at any given time tells the processor which state each pump actuator should be in. The processor controls each actuator based upon that cycle. 
     Three pump cassette  130  provides continuous flow to the patient during fill, while also drawing fluid continuously from the supply bag through an inline heater for example. As seen in  FIG. 18A , at any given time at least one pump chamber  112   a  to  112   c  is delivering fluid to the patient or to an accumulator (one purpose for an accumulator is described below in connection with  FIG. 18C ). At any given time at least one pump chamber  112   a  to  112   c  is filling the patient with heated dialysate. 
     As seen in  FIG. 18A , at time t 1 , pump chamber  112   a  is at rest for a measurement calculation from a previous emptying stroke, pump chamber  112   b  is emptying fluid to the patient, and pump chamber  112   c  is filling with fluid. At time t 2 , pump chamber  112   a  is filling with fluid, pump chamber  112   b  is still emptying fluid to the patient, and pump chamber  112   c  is at rest for a measurement calculation from a previous filling stroke. At time t 3 , and pump chamber  112   a  is still filling, pump chamber  112   b  is starting a fill stroke, pump chamber  112   c  is emptying. At time t 4 , pump chamber  112   a  is emptying, pump chamber  112   b  is filling, and pump chamber  112   c  is starting a rest period for measurement calculation. At time t 5 , pump chamber  112   a  is still emptying, pump chamber  112   b  is beginning to empty, and pump chamber  112   c  is filling. At time t 6 , pump chamber  112   a  is filling, pump chamber  112   b  is emptying, and pump chamber  112   c  is filling. At time t 7 , pump chamber  112   a  is still filling, pump chamber  112   b  is starting a rest period for measurement calculation, and pump chamber  112   c  is emptying. At time t 8 , pump chamber  112   a  is starting an emptying stroke, pump chamber  112   b  is filling, and pump chamber  112   c  is emptying. At time t 9 , pump chamber  112   a  is emptying, pump chamber  112   b  is filling, and pump chamber  112   c  is starting a fill stroke. 
     While the above sequence is described in connection with fresh fluid either filling the pump chambers  112   a  to  112   c  or emptying chambers  112  to the patient, the same sequence can be employed in connection with spent fluid either filling the pump chambers  112   a  to  112   c  or emptying chambers  112  to drain. In either case, filling and emptying pump chambers  112  is continuous when the operation of the three chambers  112  is superimposed. 
       FIG. 18B  shows a similar sequence to that of  FIG. 18A . Here, however, the overlap of the filling strokes and emptying strokes is the same.  FIG. 18B  illustrates that the relative durations of the filling and emptying strokes can be modified to suit a particular pump chamber and actuation configuration.  FIGS. 18A and 18B  also show that each time an emptying stroke is about to start, another emptying stroke already in progress is going to stay in progress long enough such that the start of the empty stroke can be delayed for a short period of time, e.g., to discharge a small amount of air from the chamber about to start without disrupting the continuity of the fluid emptying. For example, at time T in  FIG. 18B , pump chamber  112   a  is supposed to start emptying either fresh fluid to the patient or spent fluid to drain. The start of the pump-out stroke could be delayed for a short period of time to discharge air for example, without disrupting the continuous flow because pump chamber  112   c  still has some of its emptying stroke remaining. 
       FIG. 18C  illustrates a sequence in which fluid is being mixed, e.g., from two sources to make a stable dialysate for the patient. This can be done for either PD or HD, either inline or from bags or containers. Here, pump chambers  112   a  and  112   b  are synchronized. Pump chambers  112   a  and  112   b  receive fresh fluid that has already been mixed in one embodiment. Alternatively, pump chamber  112   a  pumps one fluid, while pump chamber  112   b  pumps a second fluid, each to a same line in which the two fluids are mixed properly. Pump chamber  112   c  is an accumulator that receives mixed fluid from pump chambers  112   a  and  112   b . Pump chamber  112   c  outputs to the patient. 
     The system operating the sequence of  FIG. 18C  is valved or the flow paths of the system are structured such that half of the mixed fluid leaving pump chambers  112   a  and  112   b  during the emptying stroke flows to the patient, while the other half flows to fill pump chamber or accumulator  112   c . When pump chambers  112   a  and  112   b  are filling, accumulator or pump chamber  112   c  sends its mixed fluid volume to the patient. Since all fluid flowing to and from accumulator  112   c  has been accounted for in the measurement periods of pump chambers  112   a  and  112   b , separate measurement periods for pump accumulator  112   c  are not needed. Here, flow to the patient is continuous. Filling from the concentrate sources is intermittent. A similar routine could be used to remove effluent from the patient. Accumulator  112   c  is always attempting to fill with effluent from the patient with this routine. When pumps  112   a  or  112   b  fill, the pumps pull some fluid from accumulator  112   c  as well as from the patient. A routine such as one of  FIG. 18A  or  FIG. 18B  can also be used instead to pull effluent so that flow from the patient is continuous and smoother. 
     Cassette Interface Improvements 
     Referring now to  FIGS. 19 to 22 , pneumatic system  150  illustrates one embodiment of a disposable cassette pumping interface of the present disclosure. System  150  includes a disposable cassette  140 . Disposable cassette  140  is similar to cassettes  100  and  130  described above and includes many of the same components, which are numbered the same. Cassette  140  includes a rigid housing or portion  110 . Flexible sheets  104   a  and  104   b  (not seen in  FIG. 19 ) are welded or bonded to rigid portion  110 . Alternatively, sheets  104   a  and  104   b  are formed from the single folded sheet  102  discussed above in connection with cassette  100 . Cassette  140  is shown from the reverse side as that shown in  FIG. 16  for cassette  100 . Here, pump chambers  112   a  and  112   b  bulge outwardly, showing the reverse side of pump chambers  112  as shown in  FIG. 16 . Cassette  140  can alternatively include the third pump chamber  112   c  discussed above in connection with cassette  130 . 
     Cassette  140  includes a base wall  118  as described above. Ridges  116  extend outwardly from base wall  118  to form a plurality of flow paths  132 . The valve chambers  114  and surfaces of pump chambers  112  interacting with the cassette sheeting are provided on the opposite side of cassette  140  than the side that is shown in  FIG. 19 . Cassette  140  further includes a plurality of valve ports  126 , which communicate fluidly with flow paths  132  and connect sealingly to tubes, such as supply tubes  48 , patient line  52  and drain line  54  shown above for example in connection with  FIG. 16 . 
     Pneumatic system  150  includes a membrane gasket  145 , which is shown in detail in connection with  FIGS. 20 and 22 . Membrane gasket  145  press-fits and seals in a plurality of places to a cassette manifold  180 , which is shown in detail in connection with  FIGS. 20 and 21 . In particular, cassette manifold  180  includes a interface plate  185 , to which membrane gasket  145  is attached and sealed. 
     Referring now to  FIGS. 20 and 22 , membrane gasket  145  is described in detail. Membrane gasket  145  is made of a suitable compressible and watertight material, such as silicone rubber, ethylene propylene diene monomer (“EPDM”) rubber, viton or other elastomers having a good fatigue life. In one embodiment, membrane gasket  145  is made of compression molded silicone rubber. Membrane gasket  145  includes a side  146 , which interfaces with, and indeed moves with, sheet  104   a  of cassette  140 . Membrane gasket  145  includes an opposite side  154 , which interfaces with and seals in various places to interface plate  185 . 
     Cassette side  146  of membrane gasket  145  includes raised pump ridges  148   a  and  148   b , which in an embodiment mate with and press seal against raised ridges  116  shown for example in  FIGS. 16 and 17A  as forming the shape of pump chambers  112 . A pneumatic bladder, e.g., contained in the door of instrument  20 , can be inflated when the door is closed to press a gasketed plate (not shown) against cassette  140  which, in turn, compresses sheeting  104   a  of cassette  140  against raised ridges  148   a  and  148   b , such that ridges  148   a  and  148   b  form an O-ring-like seal around raised ridges  116  of pump chambers  112  of disposable cassette  140 . This seal is described in U.S. Patent Application No. 2004/019313 A1, entitled, “Systems, Methods and Apparatus for Pumping Cassette Based Therapies”, and U.S. Pat. No. 6,261,065, entitled, “Systems and Methods for Control of Pumps Employing Electrical Field Sensing”, both of which are incorporated herein by reference and are assigned to the eventual assignee of the present disclosure. 
     Cassette facing surface  146  of membrane gasket  145  further includes raised ridges  152  forming an enclosed path which, in the same manner, seals around raised ridges  116  of valve chambers  114  of disposable cassette  140 .  FIG. 16  shows ten valve chambers  114 , which are generally aligned with and have the same shape as the ten enclosed ridges  152  of cassette surface  146  of membrane gasket  145 . Again, in an embodiment, enclosed ridges  152  mate with and press seal against ridges  116  of valve chambers  114  of the disposable cassette  140 . 
       FIG. 22  illustrates the opposite surface  154  of membrane gasket  145 , which faces and interacts with interface plate  185  of cassette manifold  180 . A raised rim  156  runs along the outside of surface  154 , so that the gasket holds its shape. An inner plateau  158  also extends out from surface  154 . The removal of material between plateau  158  and raised rim  156  allows the two structures to move independently when the instrument door is closed and cassette  140  is pressed between the instrument door and membrane gasket  145 , which is retained by interface plate  185 . Raised rim  156  optionally seals about a raised edge  202  of interface plate  185 , helping membrane gasket  145  to seal to the interface plate and prevent water or particle ingress. 
     Plateau  158  defines a pair of blind pump wells  160   a  and  160   b . Blind pump wells do not extend all of the way through the thickness of membrane gasket  145 . Instead, pump wells  160   a  and  160   b  each include sidewalls  162 , which extend most of the way through the thickness of membrane gasket  145  but leave a thin wall  168 . As described in detail below, thin walls  168  move with sheeting  104  of cassette  140  residing within pump chambers  112   a  and  112   b  of the cassette. 
     In a similar manner, plateau  158  defines a plurality of blind valve wells  164 . Blind valve wells  164  likewise do not extend all of the way through plateau  158  of membrane gasket  145 . Instead, blind valve wells include sidewalls  166  that extend most of the way through plateau  158  but terminate at blind wall  168 . Blind wall  168  of blind valve wells  164  in turn operate with sheeting cassette  104   a  at valve chambers  114 . 
     Membrane gasket  145  defines ports or apertures  170  that extend all of the way through plateau  158  of membrane gasket  145 . Accordingly, apertures  170  are seen on both plateau  148  of  FIG. 22  and surface  146  of  FIG. 20 . As further seen in  FIG. 20 , raised pump ridges  148   a  and  148   b  and raised valve ridges  152  on surface  146  of membrane gasket  145  enclose or encompass pneumatic ports  170 . As discussed in detail below, pneumatic ports  170  enable a negative pressure asserted through membrane gasket  145  to pull surface  168  of blind pump wells  160   a  and  160   b  and surface  168  of valve wells  164  together with sheeting  104   a  of cassette  140 . The configuration makes wall  168  and sheeting  104   a  operate as a single membrane for each of the individual pump chambers  112  and valve chambers  114  of the disposable cassette. 
     Membrane gasket  145  also includes dead spaces  172  which do not extend all of the way through plateau  158 . Accordingly, dead spaces  172  are only seen on the bulk surfaces  154  of  FIG. 22 . Dead spaces  172  remove material from the membrane gasket where it is not needed and, accordingly, enable membrane gasket  145  to be made more cost effectively. 
       FIGS. 20 and 21  illustrate interface plate  185 . Interface plate  185  can be made of metal, such as aluminum, or plastic. Various configurations for interface plate  185  and cassette interface  180  are discussed below in connection with  FIGS. 23 to 30 . Interface plate  185  includes a sidewall  186 , top wall  188  and an enclosed edge  202  extending from top wall  188 . As discussed above, edge  202  fits frictionally within rim  156  of membrane gasket  145  to help maintain a sealed environment between the two structures. 
     Pump chamber wells  190   a  and  190   b  are defined in or provided by membrane plate  185 . Pump wells  190   a  and  190   b  cooperate with pump chambers  112   a  and  112   b  respectively of disposable cassette  140 . In particular, pump wells  190   a  and  190   b  include pneumatic actuation ports  198 . When negative air pressure is supplied through ports  198 , the negative pressure pulls the combination of blind wall  168  and sheeting  104   a  associated with the pump chamber towards the wall of well  190   a  or  190   b . This expands the volume between sheet  104   a  and pump chamber  112  of rigid portion  110  of cassette  140  causing a negative pressure to be formed within the cassette, which in turn causes a volume of fluid (fresh or spent) to be pulled into the pump chamber  112 . Likewise, when positive pressure is applied through aperture  198 , the positive pressure pushes the combination of blind wall  168  and cassette sheeting  104   a  at the pump well  190 /pump chamber  112  interface, pushing wall  168  and sheeting  104   a  into or towards pump chamber  112  of rigid portion  110 , which in turn dispels or pushes fluid from the respective pump chamber  112  to the patient or drain. 
     Pump wells  190   a  and  190   b  each include a wall  192 . Wall  192  fits sealingly and snugly within wall  162  of a respective blind well  160   a  or  160   b  of membrane gasket  145 . The sealed interface between walls  192  of interface plate  185  and walls  162  of pump wells  160   a  and  160   b  further enhances the sealed and separated operation of the various pumps and valves within system  150 . 
     Interface plate  185  also includes a plurality of raised valve seats  194 . In particular, a valve seat  194  is provided for each blind valve well  164  of membrane gasket  145 . Each valve seat  194  and blind valve well  164  corresponds to one of the valve chambers  114  of disposable cassette  140 . Valve seats  194  include raised sidewalls  196  that extend outwardly from top surface  188  of interface plate  185 . Valve wells  164  of membrane gasket  145  fit snugly around valve seats  194 , so that walls  166  of valve walls  164  seal against walls  196  of valve seats  194 . 
     Valve actuation ports  198  are defined at least substantially at the center of seats  194 . In an embodiment, the top surfaces of valve seats  194  slope downwardly towards the actuation ports  198 . This enables mating blind surface  168  and cassette sheeting  104   a  to be pulled away from valve chambers  114  of cassette  140  to open a respective valve to allow fluid to flow therethrough. 
     As seen in  FIG. 16 , each valve chamber  114  includes a relatively centrally located protruding volcano-type port. When cassette  140  is used with system  150  the volcano ports each become aligned with one of the actuation ports  198 . When positive pressure is applied through one of the actuation ports  198 , the positive pressure pushes the cooperating blind wall  168  and cassette sheeting  104   a  at the respective valve seat  194  and valve chamber  114  of cassette  140 , to cover or close the volcano port, closing the respective valve chamber  114 . 
     As seen best in  FIG. 21 , interface plate  185  includes a plurality of gasket seal ports  200 . A gasket seal port  200  is provided for each pump well  190   a  and  190   b  and for each valve seat  194 . It should be appreciated from viewing  FIGS. 21 and 22  that seal ports  200  mate with apertures  170  of membrane gasket  145 . Seal ports  200  can extend part way or all of the way through apertures  170 . In an embodiment, apertures  170  press-fit around ports  200  to create a sealed fit between ports and the walls defining apertures  170 . 
     Sealing membrane gasket  145  on the vertical surfaces  196  of the protruding valve seats  194 , walls  192  of pump wells  190   a  and  190   b  and vacuum ports  200  provide multiple seals for the pump areas and valve areas of the cassette interface. That is, besides the membrane gasket side seals, additional compression seals exist between interface plate  185  and membrane gasket  145  as well as between gasket  145  and cassette sheeting  104   a.    
     In one embodiment the face of the membrane gasket  145  in the thin flexing sections facing the sheeting  104   a  above the pump and valve chamber of cassette  140  is textured. The surface of that same side of membrane gasket  145  at the thicker sections that compress and seal against the cassette ribs of the pump chambers, valve chambers and flow path separators of cassette  140  are not textured and have a fine, smooth surface finish for creating a good seal between the cassette sheeting  104   a  and the gasket ridges  148   a ,  148   b  and  152 . 
     The texturing of the thin sections of membrane gasket  145  provides flow channels for the air from the vacuum ports to migrate across the face of each of the valve and pump chambers of cassette  140 . The texturing also tends to prevent membrane gasket  145  and cassette sheeting  104   a  from sticking together when it is time to remove the cassette from the system. It is also contemplated to introduce a small positive pressure through ports  200  at the end of the therapy to eject the cassette  140  from the interface plate  185 . Alternately, positive pressure can be applied through valve actuation ports  198  (used to close the cassette valve chambers  114  of cassette  140  when it is time to remove the cassette. This action bulges membrane gasket  145  above pump chambers  112  and valve chambers  114  and push cassette  140  away from interface plate  185 . 
     In operation, negative pressure is applied through ports  200  and apertures  170  to pull cassette sheet  104   a  tight against blind wall  168  of membrane gasket  156  for a given pump chamber or valve chamber. This negative pressure is applied throughout the treatment, regardless of whether a positive pressure or a negative pressure is being applied via the actuation ports  198  of pump wells  190   a  and  190   b  and valve seats  194 . 
     As discussed above, the operation of applying positive and negative pressure to cassette  140  is computer-controlled. The processor controlling such actuation is also capable of receiving and processing inputs, such as pressure sensor inputs. For example, a pressure sensor can be fitted and applied to sense the pressure within a manifold linking each of valve seal ports  200 . 
     Using the pressure sensor, the processor in combination with a computer program can perform an integrity test having precision not previously available. Given the above described apparatus, if a hole develops in either membrane gasket  145  or cassette sheeting  104   a , the vacuum level in the manifold sensed by the sensor begins to degrade. The sensor output to the processor or logic implementor is indicative of the negative pressure degradation. The processor and computer program detect the decreasing signal and output that a leak is present. The output can prompt any of: (i) shutting down therapy, (ii) sounding an alarm, (iii) showing a visual message, and/or (iv) audibly describing that a leak is present to the patient or caregiver. 
     The processor also accepts one or more signal from one or more moisture sensor, such as a conductivity sensor. The one or more sensor is placed in the instrument below cassette  140 , e.g., in a channeled well beneath cassette  140 . The output of the conductivity sensor is combined logically with the output of the pressure sensor. 
     The logically combined signals from the pressure and conductivity sensors result in the following diagnostic ability. If a leak is detected, e.g., negative pressure degradation is detected, but no moisture is detected, the leak is logically determined to be from membrane gasket  145 . That is, cassette  140  is not leaking fluid into the conductivity sensor. If the leak is detected and fluid is detected, the leak is logically determined to be from cassette  140 . 
     To the extent that it is feasible to use multiple pressure sensors with individual pump walls  190   a  and  190   b  and valve seats  194  or to multiplex one or more pressure sensors, the diagnostic ability of system  150  can be expended to be able to pinpoint not only which component is leaking, but which area of which component is leaking. For example, the tubing running to ports  200  could be split between pump tubing and valve tubing. A first pressure sensor could multiplex between the tubing leading to the different pumps to pinpoint a leak in either the first or second pump. The conductivity sensor then tells the system if it is a cassette pump leak or a gasket pump leak. A second pressure sensor could multiplex to look for leaks in the different valves. Valve one to valve five for example might all check-out to be holding pressure, while valve six shows a leak, meaning the portion of the cassette sheeting or gasket in operation with valve six is leaking. The conductivity sensor tells the system if it is the cassette sheeting or the gasket at the valve six position that is experiencing a leak. 
     Another advantage of the cassette interface of the present disclosure is illustrated via  FIGS. 23, 24, 25A and 25B, 26A and 26B . System  10  in one embodiment uses a Boyle&#39;s Law based fluid measurement method taught in U.S. Pat. No. 4,826,482 (“the &#39;482 patent”), the entire contents of which are hereby incorporated by reference and relied upon. That method operates on the premise that the air being injected into (or evacuated from) pump actuation port  198  is at the same temperature as the fluid flowing through cassette  140 , and at the same temperature of the air within reference chambers  210   a  and  210   b , which is heated to body temperature or about 37° C. If a temperature difference exists between the dialysate and operating air temperatures, volumetric accuracy is compromised. 
     It is difficult to quickly and accurately measure the temperature of air when the components mounting the temperature sensor are not at the same temperature as the air that is being measured. Also at the present time, a minimum two-hour warm-up time is required before performing a volumetric calibration on the HomeChoice® Pro APD System, which requires that interface plate  185 , reference chambers  210   a  and  210   b , pump chambers  112  in pumping cassette  110  and the fluid being pumped all be warmed to about 37° C. 
       FIGS. 19 and 20  illustrate that pneumatic solenoid valves  202  are mounted directly to plate  182 .  FIG. 23  illustrates that volumetric reference chambers  210   a  and  210   b , which hold a known volume of air, are located on the reverse side  204  of interface plate  185  in one embodiment. The purposes and operation of volumetric reference chambers  210   a  and  210   b  is discussed in the &#39;482 patent and in detail below in connection with  FIGS. 27, 28A to 28F and 29 , which disclose an improvement over the &#39;482 patent method. It is enough now to understand that chambers  210   a  and  210   b  are used to calculate a volume of fluid pumped through the cassette. The advantage here is that valves  202  and volumetric reference chambers  210   a  and  210   b  are placed in close proximity to each other and to the pneumatic pathways to membrane gasket  145 . 
     For reference, side  204  of interface plate  185  in  FIG. 23  shows actuation ports  198  and gasket seal ports  200  as described above in connection with  FIGS. 20 and 21 . In the illustrated embodiment, reference chambers  210   a  and  210   b  are blind wells formed in interface plate  185  with precision to have a fixed and known volume. In an embodiment, a controlled volume (weighed amount) of a highly thermally conductive material such as cooper mesh is placed in volumetric reference chambers  210   a  and  210   b , which tends to counter a cooling effect created when high pressure air flows back from the pump chambers into the low pressure reference chambers  210   a  and  210   b . Air within pressure reference chamber  210   a  and  210   b  quickly equilibrates to the temperature of the copper mesh and the walls of the reference chambers. 
     In  FIG. 23 , interface plate  185  is formed from a thermally conductive material, such as metal, e.g., aluminum, copper, steel or stainless steel. In the present system, the thermally conductive interface plate  185  is heated, e.g., by inductively producing a current that flows within interface plate  185 , causing the plate to heat due to its bulk resistance. Alternatively a resistive heater is conductively coupled to plate  185 , e.g., via heating strip  208 . 
     Although not illustrated, a temperature sensing device, such as a thermistor or thermocouple is attached to the manifold, e.g., near reference chambers  210   a  and  210   b . The temperature sensor sends a signal back to the processor or logic implementor, which controls a power supply supplying power to the resistive heater or the current providing device, such that the temperature of interface plate  185  is maintained steady at a desired temperature. In one embodiment, interface plate  185  is heated to about 36° or 37° C. 
     Referring now to  FIGS. 24, 25A, 25B, 26A and 26B , system  210  illustrates an alternative heated cassette interface embodiment that connects to a remotely located valve manifold, such as that used in the HomeChoice® Pro APD System. System  210  includes alternative interface plate  215  and a separate heated reference chamber module  220 .  FIG. 24  illustrates module  220  attached to alternative interface plate  215 .  FIGS. 25A and 25B  illustrate alternative interface plate  215  from the front and back, respectively.  FIGS. 26A and 26B  illustrate the reference chamber module  220  from the front and back, respectively. 
     Alternative interface plate  215  in one embodiment is made of plastic, such as injection molded ABS, Delrin®, Noryl®, polycarbonate or any other suitable plastic. A front surface  212  of plate  215  provides the cassette interface, which is shaped largely the same as the cassette interface of interface plate  185 . Interface plate  215  includes a plurality of valve seats  214 , each including a raised plateau  216 . Plateaus  216  each form a downwardly angled or conical inset  218 , which defines an actuation port  222 . In the illustrated embodiment, gasket seal ports  200  are not illustrated. It should be appreciated however that gasket seal ports  200  could be added and that the membrane gasket  145  shown above can be employed with alternative interface plate  215 . 
     Alternative interface plate  215  includes alternative pump wells  230   a  and  230   b , which each include a plurality of actuation ports  232  and a conductive metal, e.g., aluminum or cooper, interface  234 . Interfaces  234  are shown in the rear view of plate  215  in  FIG. 25B  as extending through an aperture  236  in the back of pump wells  230   a  and  230   b . The conductive interfaces  234  contact the heated reference chambers of heated reference chamber module  220 , such that heat from the heated reference chambers in turn heats conductive interfaces  234 . Heated conductive interfaces  234  in turn heat air present between pump wells  230   a  and  230   b  and the mated membrane gasket. 
       FIGS. 24 and 25B  show pneumatic fittings  238 , which in one embodiment are connected to a remotely located valve manifold and to the molded plastic interface plate  215 . Because fittings  238  direct positive and negative air flowing to the valve seats  214  ( FIG. 25A ) or  194  ( FIG. 21 ) and to the valve wells  164  of membrane gasket  145 , the temperature of this air is not relevant to volumetric pumping accuracy. That is, only the air flowing to the pump chambers  112  of cassette  140  needs to be heated. Accordingly, module  220  can be made in a relatively small package, which fits onto interface  215 . 
       FIGS. 26A and 26B  illustrate heated volumetric reference chamber module  220 . As seen in  FIG. 26A , volumetric reference chambers  240   a  and  240   b  are fitted into a casing  242  having a sidewall  244 , a mounting plate  246  and a cover  248 . Sidewall  244 , mounting plate  246  and cover  248  can be made of metal or a thermally conductive plastic. Volumetric reference chambers  240   a  and  240   b  can be formed integrally as part of mounting plate  246  or be separate items attached to the mounting plate. Heating wires  250  run to a cartridge style heating element, such as those made by Watlow Electric Manufacturing Company (St. Louis, Mo.), Chromalox Corporation (Pittsburgh, Pa.) or Tempco Electric Heater Corporation (Wood Dale, Ill.) and fit into an, e.g., round, mounting aperture. Heating wires  250  can also run to resistive heating elements that can for example coil around or otherwise contact volumetric reference chambers  240   a  and  240   b  so as to heat the volumetric reference chambers conductively, convectively or via radiant energy. Again, a temperature sensor is incorporated into heated module  220 , so as to provide feedback to a heating controller, which maintains the volumetric reference chambers at a steady and desired temperature, such as 36° or 37° C., or alternatively at an equilibrium or average operating temperature that the corresponding disposable cassette reaches when pumping dialysis fluid. 
     Volumetric reference chambers  240   a  and  240   b  each include a conductive interface  252 , which mate with conductive interfaces  234  of pump wells  230   a  and  230   b  shown in  FIGS. 25A and 25B . Conductive interfaces  252  are made of a thermally conducting material, such as copper or aluminum. Thus, it should be appreciated that heat from the heating elements is transferred to the reference chambers, which are also conductive aluminum or copper in one embodiment. Heat conducts to conductive interface  252 , to conductive interfaces  234  and to the activation air, which is pumped back and forth from reference chambers  240   a  and  240   b  via valves or fittings  254 , through actuation ports  232  of pump wells  230   a  and  230   b  of interface plate  215  to the membrane and gasket. 
     Although not shown, a suitable insulating material, can be dispersed around conductive reference chambers  240   a  and  240   b  and housing  242  of module  220 . The insulating material can be insulating wool or fiberglass, for example. The insulative material can also be applied to the tubing running from fittings  254  to the remotely located valve manifold and back to the pump ports  232  over the relatively short tubing pathway to further minimize heat loss to the atmosphere. The close proximity of the pneumatic components also lends the configuration to being heated, which enables the components to be kept at a desired, stable temperature. These features reduce temperature related errors in measuring volume of fluid pumped using both the method of the &#39;482 patent and the improved method discussed below. The remotely located valve manifold can also be heated to further improve volumetric accuracy. The embodiments shown in  FIGS. 24 to 26  are more complex than the embodiments of  FIGS. 19 to 23 ; however, the latter embodiments move the valves away from the cassette interface and allow the valves to be incased within a sound enclosure. 
     Real Time Volume Measurement 
     Referring now to  FIG. 27 , system  250  illustrates one embodiment for a pneumatic control of dialysis system  10  described herein. The top of system  250  represents the components described above in connection with  FIGS. 19 to 24, 25A, 25B, 26A and 26B . LP, LS, LH, LF, LD, RP, RS, RH, RF, RD represent the valve wells of the membrane gasket and the valve chambers of the disposable cassette. Although ten valves are described here and in  FIGS. 19 to 24, 25A, 25B, 26A and 26B , more or less valves may be provided based on many factors, such as supply bag capability, whether or not admixing is supported and whether inline or batch heating is used. 
     The valving and pneumatic lines for gasket seal ports  200  are not shown in  FIG. 27 . As described above, ports  200  can be pressurized together such that one or a couple of valves in combination with a manifold running to each of ports  200  can control all the gasket seal ports  200 . 
     Left and right pump chambers represent the pump wells of the manifold and pump chambers  112  of the disposable cassette. VSL and VSR are the volumetric reference chambers discussed above. As illustrated, pressure transducer X-VSL monitors the pressure in reference chamber VSL. Pressure transducer X-VSR monitors the pressure in reference chamber VSR. 
     Valves C 0  to C 4  and D 1  to D 5  are three way valves  238  shown in  FIGS. 24 and 25B . Valves A 0  and B 4  are pump control valves  254  shown in  FIG. 26A . The remainder of valves A, C and D are located elsewhere in instrument  20 . 
     System  250  also includes a plurality of positive and negative pressure tanks, NEG T (negative pressure, communicates with chambers VSL and VSR), POS T (positive pressure, communicates with chambers VSL and VSR), NEG P-L (negative pressure, communicates with left pump chamber), NEG P-R (negative pressure, communicates with right pump chamber), POS P-L (positive pressure, communicates with left pump chamber), and POS P-R (positive pressure, communicates with right pump chamber). Separate pressure transducers X-NEG T, X-POS T, X-NEG P-L, X-NEG P-R, X-POS P-L, X-POS P-R monitor the pressure in the respective pressure tanks. 
     The separate pressure and vacuum reservoirs NEG P-L, NEG P-R, POS P-L and POS P-R allow a pressure (vacuum) decay to be measured as fluid is pushed from (pulled into) pumping chambers  112  as described in detail below. 
     For reference, a piston bellows, which can be located in the door of instrument  20 , pushes the cassette against the interface plate and an occluder bellows which can unclamp all lines (fail closed) are shown. Both bellows and the occluder are actuated pneumatically in one embodiment. 
     System  250  also includes a processor or logic implementer operating with computer memory having program code configured to perform the below described real time method. System  250  can be operated with the heated manifolds discussed above, making the assumption of constant temperature a more correct assumption. 
     Referring now to  FIGS. 28A to 28F , an improved method for measuring the volume of fluid pumped via pneumatic actuation is illustrated.  FIGS. 28A to 28D  illustrate by example how the volume of fluid moved is calculated after its has been moved. Valves shown blackened are closed, while non-shaded valves are open. The actions shown in  FIGS. 28A and 28B  occur during the relatively short rest measurement periods just prior to a pump-out stroke shown above in connection with  FIGS. 18A to 18C . The actions shown in  FIGS. 28C and 28D  occur during the short rest measurement periods just after the pump-out strokes of  FIGS. 18A to 18C . 
     The chamber is full of fluid in  FIGS. 28A and 28B . In  FIG. 28A , the valve (or valves) between chamber POS T and the pump chamber (e.g., left pump chamber) is (are) open. The valve (or valves) between the pump chamber (e.g., the left pump chamber) and the associated volumetric reference chamber (e.g., VSL) is (are) closed. This allows the pump chamber to become pressurized to the pressure of POS T, e.g., 7 psig. A vent valve (e.g., A 1  in  FIG. 27 ) is opened such that the pressure in the volumetric reference chamber (e.g., VSL) is zero. Volumetric reference chamber (e.g., VSL) has a known volume of 16.5 milliliters in the illustrated embodiment. 
     In  FIG. 28B , the valve states switch such that the valve (or valves) between chamber POS T and the pump chamber (e.g., left pump chamber) is (are) closed. The valve (or valves) between the pump chamber (e.g., the left pump chamber) and the associated volumetric reference chamber (e.g., VSL) is (are) opened. Vent valve (e.g., A 1 ) is closed. This allows the pump chamber to pressurize the volumetric reference chamber (e.g., VSL) to 2.4 psig, causing the pump pressure to drop from 7 psig to 2.4 psig. 
     The processor is configured to calculate the volume of air or gas V gas  behind the fluid pump chamber when full as follows: 
         V   gas,full =( P   ref,final   −P   ref,initial )/( P   press1,initial   −P   press1,final )* V   ref , wherein 
     P ref,final  is a final pressure in the volumetric reference chamber (e.g., VSL) after the fluid pump is allowed to pressurize the volumetric reference chamber (e.g., VSL), 2.4 psig in the example; 
     P ref,initial  is the initial pressure in the reference chamber before the fluid pump is allowed to pressurize the volumetric reference chamber (e.g., VSL), zero psig in the example; 
     P pump,initial  is an initial pressure in the pressure chamber before the fluid pump is allowed to pressurize the volumetric reference chamber (e.g., VSL), here 7 psig. P press1,final  is a final pressure in the pressure chamber after the medical fluid pump is allowed to pressurize the volumetric reference chamber (e.g., VSL), here 2.4 psig; and 
     V ref  is the volume of the reference chamber, here 16.5 milliliters. 
     Thus V gas,full =(2.4−0)/(7−2.4)*16.5 milliliters=8.6 milliliters. 
     Next, the valve chambers  114  of the disposable cassette are changed such that positive pressure from one of the pump stroke tanks POS P-L and POS P-R (illustrated in  FIGS. 28E and 28F ) pushes fluid from the pump chamber to the patient or drain. The pump-out stroke is performed in combination with the real time fluid volume measurement shown below in connection with  FIGS. 28E and 28F . This is described below with the real time pressure decay method. 
     Next, as shown in  FIG. 28C  the chamber has already been emptied. The valve (or valves) between chamber X-POS T and the pump chamber (e.g., left pump chamber) is (are) open. The valve (or valves) between chamber X-POS T and the associated volumetric reference chamber (e.g., VSL) is (are) closed. This allows the pump chamber to become pressurized to the pressure of X-POS T, e.g., 7 psig. A vent valve (e.g., A 1  in  FIG. 27 ) is opened such that the pressure in the volumetric reference chamber (e.g., VSL) is zero. Volumetric reference chamber (e.g., VSL) has the known volume of 16.5 milliliters. 
     In  FIG. 28D , the valve states switch such that valve (or valves) between chamber X-POS T and the pump chamber (e.g., left pump chamber) is (are) closed. The valve (or valves) between the pump chamber and the associated volumetric reference chamber (e.g., VSL) is (are) opened. Vent valve (e.g., A 1 ) is closed. This allows the pump chamber to pressurize the volumetric reference chamber (e.g., VSL) to 4.2 psig, causing the pump pressure to drop from 7 psig to 4.2 psig. 
     The processor is configured to perform the same calculation as shown above, this time to calculate the volume of air or gas V gas behind the fluid pump chamber when empty:    
         V   gas,empty =(4.2−0)/(7−4.2)*16.5 milliliters=24.75 milliliters.
 
     The volume of fluid pumped between the measurement periods of  FIGS. 28B and 28C  is then: fluid moved V fluid =empty chamber air volume V gas,empty −full chamber air volume V gas,full , which is 24.75 milliliters−8.6 milliliters=16.15 milliliters. 
     Referring now to  FIGS. 28E and 28F , the apparatus for performing a real time calculation of fluid pumped is illustrated. Here, pressure decay in the pressure tank driving the pump chamber during the pump-out stroke (POS P-L and POS P-R) is monitored in real time. The processor calculates the volume pumped in real time according to the equation: V fluid,t =(P POS P,initial /P POS P,t −1) (V POS P +V gas,full ), wherein 
     P POS P,initial  is an initial pressure of the pressure tank POS P-L and POS P-R prior to the pump-out stroke; 
     P POS P,t  is a pressure of the second pressure chamber at a time t during the pump-out stroke; 
     V POS P  is a known volume of the second pressure chamber; and 
     V gas,full  is the calculated volume of gas in the pump chamber when full made above in connection with  FIGS. 28A and 28B . 
     The steps of  FIGS. 28E and 28F  are made between the before and after calculations above, that is, between the steps of  FIGS. 28B and 28C . In  FIG. 28E , at the beginning of the pump-out stroke, the valve (or valves) between chamber POS T and the pump chamber (e.g., left pump chamber) is (are) closed. The valve (or valves) between chamber POS T and the associated volumetric reference chamber (e.g., VSL) is (are) closed. Vent valve (e.g., A 1  in  FIG. 27 ) is also closed. The volume of air in the pump chamber V gas,full  is known to be 8.6 milliliters as discussed above in connection with  FIG. 28B . The volume of fixed volume tank POS P-L or POS P-R is known, e.g., 500 milliliters. The initial pressure P POS P,initial  is known, e.g., 1.5 psig. 
     The valve (or valves) between chamber POS P-L or POS P-R is (are) opened beginning the pump-out stroke. At this moment the pressure begins to decay. The processor is configured to sample the pressure readings (P POS P,t) from pressure transducer X-POS P-L or X-POS P-R, for example every twenty milliseconds. The processor also calculates the real time amount of fluid pumped using the above equation and the measurement of P POS P,t .  FIG. 28F  shows an end of the pump-out stroke and a corresponding end of the pressure decay. 
       FIG. 29  shows a chart of what the decay (P POS P,t), and resulting fluid volume (milliliters) calculated according to the above equation, could look like over the pump-out stroke. For ease of illustration, only a few data points are shown. The pressure begins at the time that the pump-out stroke begins. Here, P POS P,t =P POS P,initial , such that the ratio of same is one, causing the first term in the equation and the resulting fluid volume pumped to be zero. 
     At the second pump stroke time in  FIG. 29 , P POS P,t  has dropped to 16.1 psi (absolute), making the first term in the equation above equal to 0.0062, which when multiplied by the combined volume of tank POS P-L or POS P-R (500 milliliters) and the initial volume of air in the pump chamber (8.6 milliliters) yields an absolute volume pumped of (0.0062)*508.6=3.16 milliliters. 
     At the third pump stroke time in  FIG. 29 , P POS P,t  has dropped to 16.00 psia, making the first term in the equation above equal to 0.0125, which when multiplied by the combined volume of tank POS P-L or POS P-R (500 milliliters) and the initial volume of air in the pump chamber (8.6 milliliters) yields an absolute volume pumped of (0.0125)*508.6=6.35 milliliters. 
     At the fourth pump stroke time in  FIG. 29 , P POS P,t  has dropped to 15.90 psia, making the first term in the equation above equal to 0.0189, which when multiplied by the combined volume of tank POS P-L or POS P-R (500 milliliters) and the initial volume of air in the pump chamber (8.6 milliliters) yields an absolute volume pumped of (0.0189)*508.6=9.59 milliliters. 
     At the fifth pump stroke time in  FIG. 29 , P POS P,t  has dropped to 15.80 psia, making the first term in the equation above equal to 0.0253, which when multiplied by the combined volume of tank POS P-L or POS P-R (500 milliliters) and the initial volume of air in the pump chamber (8.6 milliliters) yields an absolute volume pumped of (0.0253)*508.6=12.87 milliliters. 
     At the sixth and final pump stroke time in  FIG. 29 , which is also illustrated in  FIG. 28F , P POS P,t  has dropped to 15.70 psia (1.0 psig), making the first term in the equation above equal to 0.0318, which when multiplied by the combined volume of tank POS P-L or POS P-R (500 milliliters) and the initial volume of air in the pump chamber (8.6 milliliters) yields an absolute volume pumped of (0.0318)*508.6=16.19 milliliters. 
     The final absolute fluid volume moved or pumped via the real time algorithm, 16.19 milliliters, is virtually the same as the volume of fluid calculated via the before and after algorithm of  FIGS. 28A to 28D , 16.15 milliliters (0.25% difference). The real time method however enables mid-pump stroke volumes to be known. As described above and shown below, there are many uses for the intermediate volumes including but not limited to determining: (i) if a full pump stroke has occurred; (ii) if a line occlusion has occurred; (iii) if a leak has occurred; and (iv) if multiple concentrates have been mixed properly, for example. 
     As discussed above, the real time fluid volume calculation can be used in combination with the before and after fluid volume calculation. It should be appreciated however that the real time fluid volume calculation does not have to be used in combination with the before and after fluid volume calculation. That is, after the determination of V gas,full  in  FIG. 28B , the system can perform the real time calculation shown in  FIGS. 28E, 28F and 29 , without thereafter doing the post stroke reference chamber pressurization and calculation. It is therefore expressly contemplated to not use the post stroke reference chamber pressurization and calculation, which would negate the need for the post stroke fluid measurement periods shown for example in connection with  FIGS. 18A and 18B  for both fill and empty strokes. The post stroke fluid measurement period can be eliminated for systems that have any number of pump chambers, e.g., one, two or three pump chambers. 
       FIGS. 28A to 28F and 29  show a pump-out stroke and associated fluid volume measurement. It should be appreciated that the above methodology also applies to a pump-in or fill stroke. Here, the same pump chamber (left or right) and reference chamber (VSL or VSR) are used. The main difference is that negative pressure is used to flex the cassette sheeting, pulling fluid from a supply or a patient into the pump chamber. Thus viewing  FIG. 27 , negative pressure tank NEG P-L or NEG P-R replaces the positive pressure tanks Pos P-L or Pos P-R in  FIGS. 28E and 28F . Negative pressure would be used for example in the fresh fluid and drain fluid filling phases shown below in connection with  FIGS. 30 and 31  discussed next. The POS T tank remains as shown in  FIGS. 28E and 28F  as it is used for fluid measurement after the fact ( 28 A through  28 D) and not in the real time fluid measurement. 
     Referring now to  FIG. 30 , the real time method above is used in connection with a filling method  300  for the filling of both pump chambers (left and right) in a dialysis system that employs an inline mixing of dextrose and bicarbonate concentrates to form a biocompatible dialysate for the patient, which is advantageous physiologically for the patient. For ease of illustration, it is assumed that left pump chamber, reference chamber VSL and negative pumping tank NEG P-L control the dextrose pumping. Right pump chamber, reference chamber VSR and negative pumping tank NEG P-R control the bicarbonate pumping. POS T is used for both pump chambers. 
     In step  302   a  and  302   b , system  250  of  FIG. 27  fills left pump chamber with dextrose and right pump chamber with bicarbonate. Here, it is assumed that the volume of air or gas in the pump chamber prior to the fill has been determined per the method of  FIGS. 28A and 28B . 
     In step  304   a  and  304   b , the real time calculation of dextrose and bicarbonate using the method described above in connection with  FIGS. 28A to 28F  is made. One purpose for doing the real time calculation is to determine flowrate. That is, the processor can be further configured to calculate the difference between the instant volume and a previously calculated volume to determine a real time flowrate so long as the time between measurements is known. For example in  FIG. 29 , the volume deltas are: 3.16 milliliters, 3.19 milliliters, 3.24 milliliters, 3.28 milliliters and 3.32 milliliters. Assuming the time between pressure readings or sample time to be the same between each sample, the above deltas show the flowrate of fluid during the pump out stroke to be gradually increasing (instantaneous rate=volume delta/sample time). This may be normal due to the configuration of the pneumatic pumping system or an anomaly of the particular pump stroke. 
     The real time flowrate information can be used for many purposes. One use is for control of the heater. Copending patent application entitled “Dialysis Fluid Heating Systems”, filed Jul. 5, 2007, patent application Ser. No. 11/773,903, discloses a dialysis fluid heating control algorithm that uses flowrate feedback to control power to the fluid heating element. The flowrate information determined in connection with the real time volume calculations of step  304   a  and  304   b  is one way to provide the flowrate feedback to the referenced heating control algorithm. 
     In step  306   a  and  306   b , the volume measurements of dextrose and bicarbonate using the before and after pump stroke method of  FIGS. 28A to 28D  is performed. In step  308   a  and  308   b , the final real time volume is compared to the final before and after volume. If the difference between the two is outside of a particular amount (e.g., 1 milliliter), method  300  assumes that air is present in the associated pump chamber. The real time fluid flow measurement is essentially measuring the movement of the pumping chamber sheeting. The after the fact volumetric calculation only equals the real time measurement when no air is present within the pump chamber. If real time and after the fact measurements differ, air can be assumed to be present. If air is present, method  300  attempts to remove the air, which may require a couple of attempts. Method  300  tracks the number of attempts via a counter and eventually causes an alarm if air continues to be present. 
     A first step of the air purge subroutine is to determine if a counter is greater than a maximum amount of air removal tries N that method  300  is willing to make before determining that an alarm should be posted as seen in connection with step  310   a  and  310   b . If counter is greater than N (test could alternatively be whether the counter is equal to N), and the allotted number of air removal procedures has been exceeded, method  300  resets the counter in step  312   a  and  312   b , and posts an alarm in step  314   a  and  314   b , e.g., an “air in the system alarm”, which can be at least one of an audio alarm, visual alarm, audiovisual alarm, signal sent to a nurse, operator, pager or control center. The user can clear the alarm and resume the therapy. The procedure beginning at step  302   a  and  302   b  is then repeated. The alarm may or may not reappear. 
     If counter is less than or equal to N (test could alternatively be whether the counter is less than N), and the allotted number of air removal procedures has not been exceeded, method  300  increases the count by one in step  316   a  and  316   b  and causes instrument  20  to perform an “air purge” procedure in step  318   a  and  318   b , which can for example involve opening the drain line valve and “burping” the air out of a port of the pump chamber and into the drain line. The procedure beginning at step  302   a  and  302   b  is then repeated. 
     Returning to the real time volume versus the before and after volume comparison of step  308   a  and  308   b , if the difference between the two is inside of a particular range (e.g., 0 to 1 milliliter), method  300  next determines whether the fill was a complete fill in step  320   a  and  320   b . For example, if the volume defined between the cassette pump chambers  112  and the pump wells of the interface plate when mated is 16.5 milliliters, method  300  can look to see whether the total volume delivered meets or exceed some amount close to the defined volume, e.g., fifteen milliliters. To perform this step, method  300  can look to the real time total volume, the before and after volume or both. 
     If not enough fluid has been drawn into the pump chamber, e.g., volume is less than fifteen milliliters and the number of attempts has been exceeded a maximum number of attempts (step  322   a  or  322   b ), method  300  checks if a line kink or other fluid flow obstruction is present and attempts to unkink the line or otherwise remove the occlusion. To do so again may take a couple of tries. Method  300  tracks the number of occlusion removal tries in steps  324   a  and  324   b . If no kink or occlusion is present, the fluid source can be determined to be empty. 
     A first step of the occlusion removal subroutine is to increment a count in step  324   a  and  324   b . A next step is to determine if the count is greater than a maximum amount of occlusion removal tries N that method  300  is willing to make before determining that an alarm should be posted. If counter is greater than N (test could alternatively be whether the counter is equal to N), and the allotted number of occlusion removal procedures has been exceeded, method  300  posts a continuous alarm that the operator needs to correct before therapy can continue. 
     If counter is less than or equal to N (test could alternatively be whether the counter is less than N), and the allotted number of occlusion removal procedures has not been exceeded, method  300  causes instrument  20  to perform an “occlusion removal” procedure in step  326   a  and  326   b , which can for example involve pushing fluid back to its source or bag in step  326   a  and  326   b  in an attempt to unkink the line or bag port. A pushback is a push of a pump chamber of fluid back towards the source solution bag that is not allowing the pump chamber to fill with fluid. The pushback will fail if fluid cannot flow back to the source indicating that the source line is kinked or occluded. A real time pressure decay, or lack thereof, can be used to monitor the pushback flow, or lack thereof. 
     If the pushback is not successful as determined in connection with step  328   a  and  328   b , system  300  determines that the source is occluded in step  330   a  and  330   b . If the pushback is successful as determined in connection with step  328   a  and  328   b , the source is determined to be empty in step  332   a  and  332   b . Once an occluded source or empty source is detected, system  300  can cause an audible or visual alarms to be posted. System  300  can cause the fill to resume automatically one or two times before posting a non-recoverable alarm that requires user intervention. The counter in step  322   a  and  322   b  keeps track of the number of times the pushback attempt is made. 
     In step  334   a  and  334   b , left and right pump chambers empty their respective concentrates into a line that connects to the patient, which is long enough for the concentrates to mix sufficiently before the dialysate is delivered to the patient. In steps  336   a  and  336   b , method  300  determines using the real time fluid volume method of  FIGS. 28A to 28F  whether the total dextrose volume delivered has reached the targeted dextrose pump stroke volume delivered and whether the total bicarbonate volume delivered has reached the targeted bicarbonate pump stroke volume delivered, respectively. 
     If the targeted dextrose volume delivered has not been met in step  336   a , fluid delivery continues and method  330  determines whether the “real time” (dextrose-bicarb) volume difference is greater than ½ milliliters in step  338   a . If not, left pump chamber continues its emptying of dextrose at step  334   a , causing the real time evaluation of step  336   a  to be made again. If real time (dextrose-bicarb) volume difference is greater than ½ milliliter in step  338   a , the left patient valve (LP in  FIG. 27 ) is closed momentarily to prevent the left pump chamber from proceeding too far ahead of the right pump stroke volume delivered in step  340   a . Once the volume delivered by the left and right pump chambers is within ½ milliliter, the left pump chamber will resume its emptying of dextrose in step  334   a , causing the real time evaluation of step  336   a  to be made again. Delivery of fluid from the left pump will stop when the left pump chamber has emptied, such that the target pump stroke volume has been delivered. 
     If the target bicarbonate volume delivered has not been met in step  336   b , method  330  determines whether a real time (bicarbonate-dextrose) volume difference is greater than ½ milliliter in step  338   b . If not, right pump chamber continues to empty bicarbonate again in step  334   b , causing the real time evaluation of step  336   b  to be made again. If real time (bicarbonate-dextrose) volume difference is greater than ½ milliliter in step  338   b , the right patient valve (RP in  FIG. 27 ) is closed momentarily to prevent the right pump chamber from proceeding too far ahead of the left pump stroke volume in step  340   b . Once the volume delivered by the left and right pump chambers is within ½ milliliter, right pump chamber resumes its emptying of bicarbonate in step  334   b , causing the real time evaluation of step  336   b  to be made again. Delivery of fluid from the right pump will stop when the right pump chamber has emptied, such that the target pump stroke volume has been delivered. 
     Once the dextrose and bicarbonate target pump empty volumes are met in steps  336   a  and  336   b , respectively, the processor measures the total volumes delivered using the before and after sequence of  FIGS. 28A to 28D  for dextrose and bicarbonate in steps  342   a  and  342   b , respectively. In step  344 , the processor determines whether a cumulative measured dextrose-bicarbonate volume is less than a threshold difference, e.g., one milliliter. The processor also determines whether a cumulative measured bicarbonate-dextrose volume is less than a threshold, e.g., one milliliter. In essence, the processor is determining whether the cumulative delivered volumes of dextrose and bicarbonate are within 1 milliliter. 
     If the cumulative delivered volumes when compared are outside of the threshold range, the processor adjusts the volume for the next pump stroke by calculating a correction factor in step  346 . For example, if the normal target pump stroke volume is 15 milliliters, the system  300  will actually deliver a volume of 15 minus the correction factor for the dextrose. If the cumulative dextrose delivered volume exceeds the cumulative delivered bicarbonate volume by 1.2 milliliters, the correction factor is 1.2 milliliters and the next target stroke volume for dextrose is 15−1.2 milliliters=13.8 milliliters. 
     The correction factor is similar when bicarbonate delivered is greater than dextrose delivered by 1 milliliter or more. The correction factor is zero when the cumulative dextrose delivered is less than cumulative bicarbonate delivered. 
     After step  346 , or if the cumulative pump empty volumes when compared are inside of the threshold range, the processor determines whether the sum of the cumulative dextrose and bicarbonate pump empty volumes is within a range (e.g., one milliliter) of a prescribed or programmed total dextrose and bicarbonate fill volume in step  348 . If the measured total is within range of the prescribed total, fill phase is complete in step  350 . 
     If the measured total is outside the range of the prescribed total, the processor determines whether the cumulative measured volume is less than the prescribed pump empty volume by more than the next scheduled set of pump strokes, e.g., 30 milliliters, in step  352 . If it is, another set of pump strokes is delivered and step  352  is reached again. Steps  354  and  356  calculate the targeted fill volume for the next set of pump strokes. Step  356  calculates each targeted volume at 15 milliliters less the correction factors calculated in step  346 . Step  354  calculates the fill volume to be ½ of the remaining volume (programmed fill—cumulative measured dextrose and bicarbonate). If the remaining volume is 20 milliliters, and the correction factor for dextrose is 1.2 milliliters, the next stroke target volumes for the last set of pump strokes are calculated to be, for example: 
     (20 milliliters+1.2 milliliters)/2−1.2=9.4 milliliters for dextrose 
     (20 milliliters+1.2 milliliters)/2−0=10.6 milliliters for bicarbonate 
     The target set of pump stroke volumes adds up to 20 milliliters while correcting the cumulative volume of dextrose so that the cumulative dextrose volume equals the cumulative volume of bicarbonate. 
     Referring now to  FIG. 31 , the real time method above is illustrated in connection with a draining method  400  for the filling of one of the pump chambers (left or right) with effluent fluid from the patient. For ease of illustration, left pump chamber, reference chamber VSL and negative pumping tank NEG P-L are used in this example. Right pump chamber, reference chamber VSR and negative pumping tank NEG P-R would be performing the same method simultaneously, but asynchronously so that the right pump chamber is filling with effluent when left pump system is emptying and vice versa. 
     Draining method  400  determines if the drain is flowing properly and if air is present. In step  402 , left pump chamber is filled with effluent. In step  404 , the processor determines the real time effluent volume and flow for the fill in the manner described above. In step  406 , if flowrate is greater than a normal flow minimum rate threshold, e.g., 50 milliliters/minute, method  400  determines whether the real time volume calculation of effluent fill exceeds a minimum pump stroke volume threshold, e.g., 12 milliliters, in step  408 . If not, left pump chamber continues to fill with effluent in step  402 , forming a loop that cycles until the real time volume calculation of effluent fill exceeds the threshold in step  408 . 
     When the real time volume calculation of effluent fill exceeds the threshold in step  408 , the measurement of the effluent fill volume using the before and after pump stroke method of  FIGS. 28A to 28D  is performed in step  410 . If the real time fluid volume moved is greater than the before and after stroke method of  FIGS. 28A to 28D , air may have been drawn into the pump chamber when the chamber filled with fluid. The before and after pump stroke method of  28 A to  28 D will not be able to distinguish a pump chamber that contains 13 milliliters of fluid and  2  milliliters of air from a pump chamber that contains only 13 milliliters of fluid because the air will compress regardless of which side of the flexible sheeting it resides on, resulting in the same volume calculation. However, the flexible sheeting will move more when it accepts 13 milliliters of fluid and 2 milliliters of air than it would if it had only accepted 13 milliliters. The HomeChoice® System marketed by eventual assignee of the present disclosure attempts to complete the fill of the pump chamber using an alternate source if the pump chamber fill volume is more than 3 milliliters short of the full volume. If the HomeChoice® System cannot fill the pump chamber completely, air is assumed to be present. The contents of the pump chamber are then pumped to drain to eliminate the air. The HomeChoice® System remedy accordingly wastes time and fluid. The pump air detection and discharge regime occurring after step  410  is discussed below as step  438  eliminates. 
     Returning to step  406 , if flowrate calculated via the real time calculation is less than the normal flow minimum rate threshold, e.g., 50 milliliters/minute, method  400  determines if the real time flowrate is greater than an intermediate or low flowrate threshold, e.g., 30 milliliters/minute, in step  412 . If the real time flowrate is greater than the intermediate threshold, method  400  determines if a time T 1  at which the flowrate is between the intermediate and high-end thresholds (e.g., between 30 and 50 milliliters/minute) is less than a preset time, e.g., 5:00 minutes in step  414 . If the flowrate has remained between the intermediate and high-end thresholds for longer than the preset time, method  400  assumes that the patient line may be partially occluded and will attempt to clear the line pushing fresh dialysate toward the patient. If the pushback is unsuccessful an alarm will be posted (step  476 ). If the pushback is successful (determined via the volume using the before and after pump stroke method of  FIGS. 28A to 28D  in step  416 ) the method either advances to fill (step  300 ) or posts a low drain volume alarm (step  482 ). This routine is discussed in detail below. 
     If the flowrate has remained between the intermediate and high-end thresholds for less than the preset time, method  400  determines whether the real time volume calculation of effluent fill exceeds a threshold, e.g., 12 milliliters, in step  418 . If not, timer T 1  beginning at zero seconds is initiated in step  420  and left pump chamber continues to fill with effluent in step  402 , forming a loop that cycles until (i) T 1  reaches the preset time (e.g., five minutes) in step  414  or (ii) the real time volume calculation of effluent fill exceeds the threshold (e.g., 12 milliliters) in step  418 . 
     When the real time volume calculation of effluent fill exceeds the threshold in step  418 , the measurement of the effluent fill volume using the before and after pump stroke method of  FIGS. 28A to 28D  is performed in step  410 . The pump air detection and discharge regime occurring after step  410  is discussed below at step  438 . 
     Returning to step  412 , if flowrate calculated via the real time calculation is less than the intermediate threshold, e.g., 30 milliliters/minute, method  400  determines if the real time flowrate is greater than a low end no-flow flowrate threshold, e.g., 12 milliliters/minute, in step  422 . If the real time flowrate is greater than the low end threshold, method  400  determines if a time T 2 , at which the flowrate is between the low end and intermediate thresholds (e.g., between 12 and 30 milliliters/minute), is less than a second preset time, e.g., 3:00 minutes in step  424 . In the illustrated embodiment T 2  is less than T 1 , meaning method  400  does not wait as long at the lower flowrate before running the occlusion routine at step  416  because an occlusion is more likely at the lower flowrate. 
     If the flowrate has remained between the low end and intermediate thresholds for longer than the second preset time, method  400  assumes that the patient line may be partially occluded and attempts to clear the line by pushing fresh dialysate towards the patient. If the pushback is unsuccessful an alarm is posted at step  476 . If the pushback is successful (determined by measuring the pump fill volume using the before and after pump stroke method of  FIGS. 28A to 28D  in step  416 ), the pump advances to fill (step  300 ) or posts a low drain volume alarm (step  482 ). This routine is discussed in detail below. 
     If the flowrate has remained between the low end and intermediate thresholds for less than the second preset time T 2 , method  400  determines whether the real time volume calculation of effluent fill exceeds a threshold, e.g., 12 milliliters, in step  426 . If not, timer T 2  beginning at zero seconds is initiated in step  428  and left pump chamber continues to fill with effluent in step  402 , forming a loop that cycles until (i) T 2  reaches the preset time (e.g., three minutes) in step  424  or (ii) the real time volume calculation of effluent fill exceeds the threshold (e.g., 12 milliliters) in step  426 . 
     When the real time volume calculation of effluent fill exceeds the threshold in step  426 , the measurement of the effluent fill volume using the before and after pump stroke method of  FIGS. 28A to 28D  is performed in step  410 . The pump air detection and discharge regime occurring after step  410  is discussed below at step  438 . 
     Returning to step  422 , if flowrate calculated via the real time calculation is less than the low end no-flow threshold, e.g., 12 milliliters/minute, method  400  initiates a third timer T 3  if the timer has not yet been initiated in step  430 . If the real time flowrate is less than the low end threshold, method  400  determines if a time T 3  at which the flowrate is less than the low end threshold is less than a third preset time, e.g., 1:00 minute in step  432 . In the illustrated embodiment T 3  is less than T 2 , meaning method  400  does not wait as long at the low end flowrate before running the occlusion routine at step  416  because an occlusion or an empty patient is more likely at the lower flowrate. 
     If the flowrate has remained under the low end threshold for less than the second preset time T 3 , method  400  determines whether the real time volume calculation of effluent fill exceeds a threshold, e.g., 12 milliliters, in step  434 . If not, and timer T 3  is not equal to zero seconds, method  400  causes left pump chamber to reduce suction pressure in step  436  (e.g., by changing NEG P-L from −1.5 psig to −1.2 psig as indicated in the pneumatic system  250  of  FIG. 27 ). 
     At step  436  the patient is likely close to being empty or fully drained. To reduce discomfort in pulling the remaining effluent out of the patient, method  400  lowers the suction pressure in step  436 . Left pump chamber continues to fill with effluent in step  402 , forming a loop that cycles until (i) T 3  reaches the preset time (e.g., one minute) in step  432  or (ii) the real time volume calculation of effluent fill exceeds the threshold (e.g., 12 milliliters) in step  434 . 
     When the real time volume calculation of effluent fill exceeds the threshold in any of steps  408 ,  418 ,  426  or  434 , the measurement of the effluent fill volume using the before and after pump stroke method of  FIGS. 28A to 28D  is performed in step  410  and a pump air detection check is performed. Here, method  400  calculates the difference between the real time calculation of effluent removed from the patient via the method of  FIGS. 28A to 28F  and the volume calculated using the before and after pump stroke method of  FIGS. 28A to 28D . If the volume difference is less than a threshold difference (e.g., 1 milliliter) in step  438 , the system assumes that little or no air is present and that normal pumping can continue because any air that may be present will not pass through the pump. 
     If the difference determined in step  438  is greater than the threshold, method  400  initiates a fourth timer T 4  in step  440  if the timer has not yet been initiated. If the difference has remained out of range for greater than a fourth preset time (e.g., three minutes) as determined in step  442 , method  400  posts an air alarm in the system alarm in step  444 . If (i) the difference has not remained out of range for greater than the fourth preset time as determined in step  442  or (ii) the difference between the real time and before/after volumes is less than the threshold, method  400  causes left pump chamber to empty the effluent to drain in step  446 . However, if T 4  is greater than three minutes, the system assumes that the pump chamber has been ingesting air from the patient for three minutes and posts an alarm at step  444 . 
     Step  448  creates a loop in which left pump chamber continues to empty to drain as long as the drain flow is greater than a threshold value, e.g., 80 milliliters/minute. When drain flow falls below the threshold, method  400  determines if the real time volume calculation of effluent sent to drain exceeds a threshold volume, e.g., 12 milliliters, in step  450 . If not, method  400  determines if drain flow has fallen below a low end threshold, e.g., 12 milliliters/minute, in step  452 . 
     If drain flow has not fallen below the low end threshold in step  452 , a longer timer T 5  is initiated if not initiated already in step  454 . A loop is created as long as real time volume is less than the threshold, e.g., 12 milliliters, and drain flow remains above the low end threshold, e.g., 12 milliliters/minute and below the upper threshold, e.g., 80 milliliters/minute until timer T 5  reaches a fifth (longer) preset time (e.g., three minutes) in step  456 , at which time method  400  sends an alarm (audio, visual or audiovisual) to check the drain line for an occlusion in step  458 . 
     If drain flow has fallen below the low end threshold in step  452 , a shorter timer T 6  is initiated if not initiated already in step  460 . Another loop is created as long as real time volume is less than the threshold, e.g., 12 milliliters, and drain flow remains below the low end threshold, e.g., 12 milliliters/minute, until timer T 6  reaches a sixth (shorter) preset time (e.g., thirty seconds) in step  462 , at which time method  400  sends the alarm to check the drain line for an occlusion in step  458 . 
     When drain flow falls below the threshold in step  448  and the real time volume calculation of effluent sent to drain exceeds a threshold volume, e.g., 12 milliliters, in step  450 , method  400  calculates the total effluent volume sent to drain via the before and after method of  FIGS. 28A to 28D  as seen in step  464 , after which left pump chamber begins another fill of effluent at step  402 . 
     When any of the timers T 1 , T 2  or T 3  times out in steps  414 ,  424  or  432 , respectively, it is possible that the patient line has an occlusion, which could for example be due to fibrin blockage or a partially kinked line. At step  416 , method  400  calculates the total effluent pulled from the patient during the current pump stroke using the before and after method of  FIGS. 28A to 28D . In step  466 , left pump chamber empties the effluent to drain. In step  468 , the total effluent volume sent to drain via the before and after method of  FIGS. 28A to 28D  is calculated, after which left pump chamber pulls a bolus of fresh fluid from a supply bag in step  470 . 
     Left pump chamber pushes the fresh bolus to the patient via the patient line to verify that fill can be performed and to remove any fibrin blockage or to un-kink the patient line if it is partially occluded due to a kink in step  472 . If the pushback procedure is not successful, e.g., fluid cannot reach the patient or real time flowrate is below a threshold, as determined in step  474 , method  400  in step  476  posts a patient line occluded alarm via any of the ways discussed above. If the procedure is successful, e.g., fluid reaches the patient and/or real time flowrate is above a threshold, as determined in step  474 , method  400  assumes that the patient is empty at step  478 . 
     After the patient is determined to be empty in step  478 , a total volume of effluent pulled from the patient is calculated and compared to a minimum drain volume in step  480 . If total effluent volume is less than a minimum volume, a low drain alarm is posted in step  482  via any of the techniques described above. If total effluent volume reaches or exceeds the minimum volume, system  10  employing method  400  advances to the fill phase  300  described above in connection with  FIG. 30 . The minimum volume can be a percentage of the programmed fill volume when draining to empty. When draining to a target volume, for example with a tidal therapy, the minimum volume is the target volume. Method  400  also monitors the cumulative volume of effluent drained after step  410 . This cumulative volume is reported as the volume drained when a tidal drain ends while under a normal flow condition. Otherwise, the cumulative drain volume from step  480  is reported as the volume drained. 
     Temperature Sensor 
     Referring now to  FIGS. 32 and 33 , system  500  illustrates one possible fluid temperature measuring apparatus and method for system  10 . Temperature measuring system  500  is advantageous because it is non-invasive. System  500  measures the temperature of fluid flowing through a portion of disposable set  50 . For example, system  500  could measure the temperature of fluid flowing through disposable cassette  28 ,  100 ,  130 ,  140 , e.g., upstream, downstream or directly at a fluid heating pathway of a cassette used with inline heating. Or, the fluid could be sensed while flowing through one of the fluid lines, such as directly upstream and/or downstream of the fluid heater. Further alternatively, the fluid could be sensed while residing within a bag or container, such as a warmer bag used with batch heating. 
     In the illustrated embodiment, system  500  includes a housing  502 , which is part of instrument  20  of system  10 . For example, housing  502  can be integrated into interface plate  185  described above in connection with  FIGS. 19 to 21 . When cassette  28 ,  100 ,  130 ,  140  is loaded into instrument  20 , a portion of the cassette is pressed against housing  502 . Housing  502  can be plastic or metal and should be at least substantially opaque, e.g., to infrared wavelengths. With the cassette  28 ,  100 ,  130 ,  140  compressed against housing  502  and the door of instrument or machine  20  closed on the other side of cassette  28 ,  100 ,  130 ,  140 , little ambient light reaches the portion of cassette  28 ,  100 ,  130 ,  140  interfacing with system  500 . 
     Sheeting  102  of cassette  28 ,  100 ,  130 ,  140  includes a portion  504  transparent, e.g., to infrared wavelengths, and a non-transparent or opaque portion  506 . Portions  504  and  506  are placed adjacent to housing  502 . Opaque portion  506  is formed for example via an inking (e.g., ink-jetting), printing or painting (e.g., spray painting) process. Alternatively, opaque portion  506  is formed via an opaque patch adhered to the disposable item. The size of opaque portion  506  can range from about ¼ inch by ¼ inch (6.4 mm by 6.4 mm) to about one inch by one inch (2.54 cm by 2.54 cm) or the same size in diameter if circular. Transparent portion  504  can be the clear sheeting  102  and can have an infrared target area at least as large as that of opaque portion  506 . The size of the target area depends upon the infrared sensor selected and the distance that the sensor is mounted away from the target area. For example, a MIKRON M50 infrared sensor suitable for this application has a ½ inch (1.27 mm) target diameter when pressed against the target. The target diameter increases to 1¼ inch (3.18 cm) when the sensor is moved to six inches (15.25 cm) from the target. 
     Temperature measuring system  500  includes an arm  508 , which holds a temperature sensor  510 . Arm  508  is able to pivot back and forth at a pivot point  512 , so that temperature sensor  510  is pointed selectively at either transparent portion  504  or opaque portion  506 . Temperature sensor  510  in one embodiment is an infrared temperature sensor. Suitable infrared temperature sensors  510  are provided by PerkinElmer (Walthen, Mass.), Dexter Research (Dexter, Mich.), Electro Optical Components (Santa Rosa, Calif.). 
     In the illustrated embodiment, housing  502  includes electromagnets  514 . When energized, the electromagnets will push and/or pull on a metal portion of magnetized pivot arm  516 . Reversing the polarity will cause the polarity orientation to change. Arm  508  includes a magnetic, e.g., steel, portion  516 , which is pulled towards one of the electromagnets  514  when that electromagnet is energized. Electromagnets control the orientation of the infrared temperature sensor so that infrared temperature sensor  510  can be pointed selectively (i) at opaque portion  506  to take a first temperature reading, temp wall, of the sheeting  102  only as seen in  FIG. 32  or (ii) at clear portion  504  to take a second temperature reading, temp wall and fluid , which is a combination (A*temp wall +B*temp fluid ) of the sheeting  102  and the fluid within the sheeting  102  as seen in  FIG. 33 . A and B are constants dependent upon the film or tube thickness and composition and are determined experimentally. 
     Because temp wall  is measured and known, the fluid temperature temp fluid  can be calculated using measured temp wall  and measured temp wall and fluid  according to the equation: 
       temp fluid =[measured temp wall and fluid −(A)*(measured temp wall )]
 
     B 
     A processor and memory on a temperature controller or at a central processing unit store constants A and B and perform the above calculation. Temperature sensing system  500  should provide near real time, non-invasive monitoring of the fluid temperature. 
     Sensor  510  is flipped back and forth and the different temperature measurements are taken for example, every second. Alternatively, two independent infrared temperature sensors are used, one for infrared energy transmissive portion  504  and the other for infrared energy non-transmissive portion  506 . Further, alternatively, a dual or quadruple infrared sensor package is used, such as a Perkinselmer® TPS 2534 dual element thermopile or TPS-4339 Quad Element thermopile. The quad element system provides redundant temperature measurement. Multiple sensors remove calibration complexity. 
     A motor or solenoid could be used instead of electromagnets. Further alternatively, arm  508  could be pushed by a spring to one pivot position and pneumatically retracted to the second pivot position. 
     Referring now to  FIG. 34 , data illustrating the accuracy of fluid sensing system  500  is shown. System  500  in  FIG. 34  appears to provide temperature readings non-invasively that approach the accuracy and response time of an invasive temperature sensor. The correlation between the readings from a resistance temperature detector (“RTD”) sensor immersed in the fluid to the calculated readings from infrared sensing system  500  is good especially considering that the fluid temperature rose from just over 20° C. to over 50° C. during a ten minute time span in which the temperature readings were taken. In the example, constant A was set to 0.877985 and constant B was set to 0.109635. The curve fit line was found to be T CALC =1.047*T RTD −0.0303. 
     Multi-Chamber Bag Open Sensor 
     Referring now to  FIGS. 35 and 36 , inductive sensing system  530  illustrates one embodiment for detecting: (i) whether a single chamber supply bag  40  (referring generally to supply bags  40   a  to  40   d  discussed above) or a multi-chamber supply bag  540  is residing on a particular one of shelves  32 ,  34 ,  36  and  38 ; and (ii) if the supply bag is a multi-chamber supply bag  540 , whether an associated frangible seal  542  has been broken allowing two or more concentrates  544   a  and  544   b  from separate chambers  546   a  and  546   b , respectively, to mix. 
     Multi-chamber supply bag inductive sensing system  530  measures current, which for a fully opened container is indicative of either electrical conductivity or electrical impedance. The measured current indicates whether frangible seal  542  between chambers  546   a  and  546   b  of multi-chamber bag  540  has been broken so that previously separated solutions can mix prior to delivery to a patient. 
     The different concentrates  544   a  and  544   b  within separate chambers  546   a  and  546   b  of multi-chamber bag  540  have different concentrations of ions. The different ionic nature of different concentrates  544   a  and  544   b  provides an opportunity to correlate a measured current in a mixed solution to a conductivity or impedance of the solution. System  530  can thereby compare the determined conductivity or impedance with an expected conductivity or impedance to confirm whether the concentrates have been mixed properly. System  530  is non-invasive, which is advantageous when dealing with sterile medical fluids, such as dialysis fluids. It should be appreciated that system  530  can also operate with non-sterile or non-injectable fluids. 
     System  530  includes a first coil  532  and a second coil  534 , which are located in different positions within the limits of the tray or shelf (e.g., one of shelves  32  to  38 ) onto which multi-chamber bag or container  540  is placed for treatment. For example, coils  532  and  534  are installed on top of or underneath the tray or shelf (e.g., one of shelves  32  to  38 ) or are laminated within the tray or shelf. If installed on top of the tray, coils  532  and  534  can be covered with a protective coating or layer. Coils  532  and  534  can for example be formed from single stranded wire or multi-stranded wire, such as litzwire. In the illustrated embodiment, coils  532  and  534  are pancake or flat coils. 
     One of coils  532  and  534  performs a transmitter function while the other of the coils performs a receiver function. The coils can be dedicated to one of the functions, e.g., coil  532  transmits and coil  534  receives as shown in  FIGS. 36 and 37 . Alternatively, coils  532  and  534  alternate between the transmitter and receiver functions. 
     A signal (voltage or current) generator  536  excites transmitter coil  532  with a signal that varies with time, such as sine wave, square wave, sawtooth wave or other time variable wave. Generator  536  can be for example (i) a logic level oscillator, (ii) a combination of oscillator and filter or (iii) a waveform generator circuit. One suitable voltage range includes four to twenty volts. Transmitter coil  532  induces small currents in the dialysate, while receiver coil  534  senses those currents. The intensity of the currents that receiver coil  534  senses depends on the type of solution and the degree of electrical coupling between bags and coils  532  and  534 . For example, if the shape of the supply bag or container is such that its footprint does not project on top of a receiver coil, the receiver coil will not sense any current. If the shape of the supply bag or container is such that its footprint does not project on top of a transmitter coil, the transmitter coil will induce no current or relatively little current into the solution. 
       FIG. 35  shows that unopened seal  542  causes container  540  to couple less effectively with the flat areas of chambers  546   a  and  546   b  that lie flat on the tray or shelf. Accordingly, a sensor or measuring device  538  will measure less current from receiver coil  534 . This level of current in  FIG. 35  is shown to reside in a “not mixed” range. Current measuring device  538  in one embodiment is a multimeter or an ammeter. 
       FIG. 36  shows that opened seal  542  couples equally effectively with the flat areas of chambers  546   a  and  546   b , since the entire bag or container now lies flat on the tray or shelf. Accordingly, sensor or measuring device  538  measures more current from receiver coil  534 . This level of current in  FIG. 36  is shown to reside in a “mixed” range. 
       FIGS. 37A to 37D  illustrate an inductive system  560  that can determine whether bag  540  is positioned and oriented correctly on tray or shelf  32 ,  34 ,  36  or  38 . Bag  540  shown from the top in  FIGS. 37A to 37D  shows frangible seal  542  separating chambers  546   a  and  546   b . System  560  includes four coils  532   a ,  532   b ,  534   a  and  534   b . Each coil can be used for either transmission or reception. The arrows represent some of the possible couplings between the coils. 
       FIG. 37A  illustrates a proper loading of bag  540 , in which a port or pigtail  548  of bag  540  is aligned with and rests in aperture  35  of tray or shelf  32 ,  34 ,  36  or  38 . Here, seal  542  separates coils  532   a  and  532   b  from coils  534   a  and  534   b , respectively. Seal  542  does not separate coil  532   a  from coil  534   a  or coil  534   a  from coil  534   b . The proper loading position or orientation of  FIG. 37A  therefore results in a signature inductive coupling pattern of (i) coil  532   a  to coil  532   b —high coupling, (ii) coil  534   a  to coil  534   b —high coupling, (iii) coil  532   a  to coil  534   a —low coupling, and (iv) coil  532   b  to coil  534   b —low coupling. 
     The improperly loaded bag  540  of  FIG. 37B  on the other hand results in a different inductive coupling pattern of (i) high coupling, (ii) high coupling, (iii) high coupling, and (iv) high coupling because all four coupling coils are located on one side of frangible seal  542 . The improperly loaded bag  540  of  FIG. 37C  results in still a different inductive coupling pattern of (i) low coupling, (ii) low coupling, (iii) high coupling, and (iv) high coupling due the position of seal  542  relative to the coils illustrated in  FIG. 37C . The improperly loaded bag  540  of  FIG. 37D  results in the same inductive coupling pattern of  FIG. 37C , namely, (i) low coupling, (ii) low coupling, (iii) high coupling, and (iv) high coupling due the position of seal  542  relative to the coils illustrated in  FIG. 37D . 
     A system controller takes the four measurements before seal  542  is broken and categorizes the coupling signature into either a bag properly loaded state or an improperly loaded state. The electronics of system  10  in one embodiment include a multiplexer that sequences through each of transmitter/receiver pairs (i) to (iv) upon receiving a signal from a load cell detecting that a bag has been loaded or upon receiving an input from the user that a bag or bags have been loaded. A single signal source  536  can be multiplexed to a desired coil functioning as the transmitter for the particular pair being sensed, e.g., coil  532   a  for pair (i), coil  534   a  for pair (ii), coil  532   a  for pair (iii), and coil  534   a  for pair (iv) shown above. The multiplexer also sequences through a plurality of electrical switch states to electrically connect the appropriate coils of each pair (i) to (iv) to source  536  and sensor  538  at the appropriate time. 
     It is also possible, after determining that bag  540  has been loaded properly, that the controller can verify from the inductive coupling signature that the composition of concentrate solutions  544   a  and  544   b  in compartments  546   a  and  546   b  is correct according to an expected conductivity for each solution. Tested pairs (iii) and (iv) for the correct bag position of  FIG. 37A  reveal the conductivity for concentrates  544   a  and  544   b  of compartments  546   a  and  546   b , respectively. If a conductivity is out of an expected range an error can be generated. The controller can also verify the integrity of seal  542 . Before allowing treatment to begin, system  560  also verifies that seal  542  has been opened allowing concentrates  544   a  and  544   b  to mix. Once the solution is mixed, the conductivity of the mixed dialysate can also be checked. 
     Correct bag positioning is useful for systems that use gravity for any of the treatment operations. Verification of each of the individual solutions allows determining if concentrations are adequate for the intended treatment. Verification of the integrity of the seal allows instrument  12  to ascertain that the solutions have not been mixed before treatment has begun. Premature mixture of the solutions considerably shortens the shelf life of the product. Such measurement ensures that no degradation of the solution has occurred. 
     The above-mentioned controller can operate directly or indirectly with a central processing unit, which in turn operates with a video controller and graphical user interface (“GUI”). If all of the above checks are verified, system  10  causes GUI to display a “bag loading ok” or similar message and allows therapy to continue. If one of the bags  540  is loaded incorrectly, system  10  causes GUI to display a “check bag loading” or similar message and perhaps even identifies the bag, e.g., “check loading of second bag from top”. If the bags  540  are loaded correctly but system  560  detects an abnormal conductivity, system  10  causes GUI to display a “check solution of bags loaded” or similar message and perhaps even identifies the bag, e.g., “check solution in second bag from top”. If bag loading and concentration are verified but the user tries to begin therapy without opening one or all of bags  54 , system  10  causes the GUI to display a “open bag seal prior to treatment” or similar message and perhaps even identifies the bag, e.g., “open seal of top bag prior to treatment”. 
       FIGS. 4 to 9  illustrate a bag management system  30 , which holds multiple supply bags at an angle for fluid flow and air handling purposes. It should be appreciated that inductive sensing systems  530  and  560  can operate at the bag angle of system  30 , alternatively with bags  540  loaded at least substantially horizontally or further alternatively with bags  540  loaded at least substantially vertically. In slanted system  30 , the coils can be laminated to an upper or lower surface of each tray or be embedded in the tray. With a vertical manager, the coils can be connected to one or more vertical bar that runs vertically up one of the bags and presses respective coils against each bag. Signals to the coils are supplied through vertical support bars. The bag management systems can supply additional information such as weight information via a load cell. 
     It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.