Abstract:
A flow management system for extracorporeal blood treatment application helps to ensure proper balance of incoming and outgoing fluids by precise balancing of relatively small balance chambers. The invention employs combinations of features that help to ensure accuracy including underfilling of the waste flow side of a fixed volume chamber and mechanical connections to synchronize valves and pumps.

Description:
This is a continuation-in-part of U.S. application Ser. No. 09/451,238, filed Nov. 29, 1999, now abandoned, Ser. No. 09/513,773, filed Feb. 25, 2000, issued as U.S. Pat. No. 6,579,253, Ser. No. 09/513,911, filed Feb. 25, 2000, issued as U.S. Pat. No. 6,638,478, Ser. No. 09/513,771, filed Feb. 25, 2000, issued as U.S. Pat. No. 6,673,314, Ser. No. 09/513,446, filed Feb. 25, 2000, now abandoned, Ser. No. 09/513,902, filed Feb. 25, 2000, issued as U.S. Pat. No. 6,554,789, Ser. No. 09/512,927, filed Feb. 25, 2000, issued as U.S. Pat. No. 6,589,482, Ser. No. 09/512,929, filed Feb. 25, 2000, issued as U.S. Pat. No. 6,638,477, Ser. No. 09/513,910, filed Feb. 25, 2000, issued as U.S. Pat. No. 6,830,553, Ser. No. 09/513,564, filed Feb. 25, 2000, now abandoned, Ser. No. 09/513,915, filed Feb. 25, 2000, now issued as U.S. Pat. No. 6,595,943, and Ser. No. 09/894,236, filed Jun. 27, 2001, now U.S. Pat. No. 6,686,946, which is a divisional of Ser. No. 08/800,881, filed Feb. 14, 1997, now abandoned. Each of the above-identified applications is expressly incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to systems and methods for processing blood or other fluids that are conveyed to and from an animal body, e.g., for dialysis, filtration, pheresis, or other diagnostic or therapeutic purposes. The systems may include roller guides on pumps, alignment using pump tubing fitments, air detector tube pushers for loading, blood leak detector, temperature sensing, and pressure sensing. 
     BACKGROUND OF THE INVENTION 
     There are many types of blood processing and fluid exchange procedures, each providing different therapeutic effects and demanding different processing criteria. Typically, such procedures entail the removal of blood or another fluid from an individual and the return of blood or another fluid to the individual in a controlled fashion. Examples of such procedures include hemofiltration (HF), hemodialysis (HD), hemodialysis with hemofiltration (HDF), and peritoneal dialysis (PD). 
     In carrying out these procedures, specially designed fluid circuits, which can be complex and convoluted, are placed into a prescribed operative association with pumps, clamps, and sensors, which are typically mounted on a machine that is also specially designed to carry out the intended procedure. Numerous safety and control elements of the fluid circuit and the machine must be placed in operative association in order to carry out the procedure in the intended way. As a consequence, the process of loading a fluid circuit on the machine can be tedious and error-prone. 
     There is a need for simplicity and convenience when loading a fluid circuit in a prescribed way in association with safety and control elements on a blood and/or fluid processing machine. 
     Typically, when performing the blood processing and fluid exchange procedures of the type just described, a replacement or make-up fluid is returned back to the individual in some proportion to the amount of fluid that is removed from the individual. The type and make-up of fluids that these procedures handle vary according to the particular treatment modality being performed, e.g., among waste fluid and replacement fluid (in HF or HDF); or replacement fluid and dialysis solution (in HD or HDF); or fresh peritoneal dialysis solution and spent peritoneal dialysis solution (in PD. Controlled balancing of fluid amounts can be achieved by monitoring the weights of fluid removed and replacement or makeup fluid. However, weight sensing itself requires additional fluid circuit elements (e.g., weigh containers), additional hardware elements (e.g., weigh scales), as well as additional processing control and feedback features. These items add further complexity to the systems and their operation. 
     There is also a need for simplicity and convenience when undertaking a controlled balancing of fluids during a blood processing and/or fluid exchange procedure. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention provides systems and methods for processing blood and/or other fluids, which include a fluid interface between a fluid processing circuit and a fluid processing machine that makes possible a fast, convenient, one step process for loading the fluid processing circuit on the machine. 
     In one embodiment, the systems and methods consolidate all blood and fluid flow paths in a unitary, easily installed cartridge. The cartridge establishes a fixed orientation for fluid circuit elements and their operative interface with the hardware elements, such as pumps, sensors, and clamps, on the processing machine. The fixed orientation requires that all safety and control elements on the cartridge and machine are brought into operative association in a single, straightforward loading step. Due to the cartridge, the operator cannot place one part of the fluid circuit into an operating condition with one or more hardware elements on the machine without placing the entire fluid circuit into an operating condition with all the hardware elements on the machine. The consolidation of all blood and fluid flow paths in a single, easily installed cartridge also avoids the potential of contamination, by minimizing the number of connections and disconnections needed during a given treatment session. 
     Another aspect of the invention provides systems and methods for processing blood and/or other fluids that makes possible the performance of accurate, synchronized volumetric fluid balancing, without the need for weight sensing. 
     Other features and advantages of the inventions are set forth in the following specification and attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a system that includes a machine and fluid processing cartridge that, in use, is mounted on the machine for conducting various types of blood processing and/or fluid exchange procedures; 
         FIG. 2  is a front perspective view of an embodiment of a machine that can form a part of the system shown in  FIG. 1 ; 
         FIG. 3  is a plane view of the exterior surface of an embodiment of a fluid processing cartridge that can form part of the system shown in  FIG. 1 ; 
         FIGS. 4 to 6  are side elevation views showing the loading of the fluid processing cartridge shown in  FIG. 3  onto the machine shown in  FIG. 2 ; 
         FIG. 7  is a perspective exploded view of the fluid processing cartridge shown in  FIG. 3 ; 
         FIG. 8  is a plane view of the exterior surface of the fluid processing cartridge shown in  FIG. 3 , with the cover member removed to show the channels that guide the passage of flexible tubing that forms a part of the fluid circuit carried by the cartridge; 
         FIG. 9  is a plane view of the interior surface of the fluid processing cartridge shown in  FIG. 3 ; 
         FIGS. 10 and 11  are plane view of fluid management modules that form a part of the fluid circuit carried by the cartridge; 
         FIG. 12  is a schematic view of a fluid circuit for carrying out hemofiltration, which the cartridge shown in  FIG. 3  can be configured to form; 
         FIG. 13  is a perspective view of the inside of the door of the machine shown in  FIG. 2 ; 
         FIG. 14  is a largely schematic side section view of the overlaying fluid balancing compartments that are part of the fluid management modules shown in  FIGS. 10 and 11 , showing their orientation with valve elements carried by on the machine shown in  FIG. 2 ; 
         FIG. 15  is a front perspective view of an embodiment of a chassis panel that the machine shown in  FIG. 2  can incorporate; 
         FIG. 16  is a back perspective view of the chassis panel shown in  FIG. 15 , showing the mechanical linkage of motors, pumps, and valve elements carried by the chassis panel; 
         FIG. 17  is a side section view of one of the clamp elements shown in  FIGS. 15 and 16 ; 
         FIG. 18  is a diagrammatic view of a telemetry network that can form a part of the system shown in  FIG. 1 ; and 
         FIG. 19  is a plane view of a graphical user interface that the machine shown in  FIG. 2  can incorporate. 
     
    
    
     The invention may be embodied in several forms without departing from its spirit or essential characteristics. The scope of the invention is defined in the appended claims, rather than in the specific description preceding them. All embodiments that fall within the meaning and range of equivalency of the claims are therefore intended to be embraced by the claims. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     I. System Overview 
       FIG. 1  shows a system  10  that is well suited for handling fluids in support of various types of blood processing and/or fluid exchange procedures. The system  10  includes a durable hardware component or machine  16  (see  FIG. 2 ) and a removable fluid processing cartridge  18  (see  FIG. 3 ) that is intended to be installed in operative association with the machine  16  for use (see  FIGS. 4 to 6 ). 
     The system  10  is suitable for use in many diverse treatment modalities during which blood and/or fluid are conveyed to and from an animal body. In particular, the system  10  is well suited for treatment modalities during which one fluid is removed from the body and replaced with another fluid in a controlled fashion. Such modalities include, e.g., hemofiltration (HF), hemodialysis (HD), hemodialysis with hemofiltration (HDF), and peritoneal dialysis (PD). 
     For example, the system  10  can perform hemofiltration, e.g., to treat an individual whose renal function is impaired or lacking, according to different selected protocols. The system  10  can be adapted to perform hemofiltration at relatively high blood flow rates to enable relatively short session time intervals, as well as at lower blood flow rates and over longer session time intervals. The former protocol can be adopted to achieve hemofiltration three or more times a week. The latter protocol can be adapted to achieve an overnight treatment regime, which can be called “nightly hemofiltration.” Nightly hemofiltration can be conducted at intervals less or more frequent than three times a week. Alternatively, the system  10  can be adapted to perform hemofiltration on an acute basis, or on an intermittent chronic basis, at virtually any prescribed time interval and treatment pattern that achieves the maintenance of uremic toxin levels within a comfortable range. Thus, the system  10  can be adapted to perform multiple hemofiltration treatments per day at varying session times, morning, afternoon, or night, or a combination thereof. 
     The system  10  can also just as readily be adapted to perform hemodialysis (HD) or hemodialysis with hemofiltration (HDF). The fluid balancing functions that the system  10  can perform, as will be described in greater detail later, can also be readily adapted for use, either individually or in combination, in systems intended to perform prescribed peritoneal dialysis modalities. 
     The type and make-up of fluids that the system  10  can balance can and will vary according to the particular treatment modality being performed, e.g., among waste fluid and replacement fluid (in HF or HDF); or replacement fluid and dialysis solution (in HD or HDF); or fresh peritoneal dialysis solution and spent peritoneal dialysis solution (in PD). The terminology employed in this Specification in characterizing a particular type or make-up of fluid, or as ascribing a source, destination, or direction of fluid flow in the context of describing one treatment modality is not intended to be interpreted as being limited to that particular type or make up of fluid or that particular flow source, destination, or direction. Rather, a person of skill in the art will readily appreciate that the fluid type and make up and the flow particulars relating to volumetric fluid balancing can vary with different treatment modalities. 
     A. Fluid Processing Machine 
     The machine  16  (see  FIG. 2 ) is preferably lightweight and portable, presenting a compact footprint, suited for operation on a table top or other relatively small surface normally found, e.g., in a hospital room or in a home. The compact size of the machine  16  also makes it well suited for shipment to a remote service depot for maintenance and repair. 
     Desirably, the machine  16  includes an operator interface  44  (see  FIG. 2 ).  FIG. 19  shows a representative display  324  for the operator interface  44  for the machine. The display  324  comprises a graphical user interface (GUI), which, in the illustrated embodiment, is displayed by the interface  44  on the exterior of the door  28 , as depicted in  FIG. 2 . The GUI can be realized, e.g., as a membrane switch panel, using an icon-based touch button membrane. The GUI can also be realized as a “C” language program. 
     The GUI  324  presents to the operator a simplified information input and output platform, with graphical icons, push buttons, and display bars. The icons, push buttons, and display bars are preferably back-lighted in a purposeful sequence to intuitively lead the operator through set up, execution, and completion of a given treatment session. 
     B. The Fluid Processing Cartridge 
     The processing cartridge  18  (see  FIG. 3 ) provides the fluid interface for the machine  16 . The fluid interface between the cartridge  18  and machine  16  makes possible a fast and convenient one step process for loading the cartridge  18  for use on the machine  16  (see  FIGS. 4 to 6 ). 
     In one embodiment, the cartridge  18  establishes a fixed orientation for fluid circuit elements and their operative interface with the hardware elements, such as pumps, sensors, and clamps, on the machine  16 . The fixed orientation requires that all safety and control elements on the cartridge  18  and machine  16  are brought into operative association in a single, straightforward loading step. Due to the cartridge  18 , the operator cannot place one part of the fluid circuit into an operating condition with one or more hardware elements on the machine  16  without placing the entire fluid circuit into an operating condition with all the hardware elements, including safety systems, on the machine  16 . 
     Desirably, the cartridge  18  makes possible the elimination of air-blood interfaces, and/or positive pressure monitoring. In association with the machine  16 , the fluid cartridge  18  can also perform accurate, synchronized volumetric fluid balancing, without the need for weight sensing, as will be described in greater detail later. 
     The consolidation of all blood and fluid flow paths in a single, easily installed cartridge  18  avoids the potential of contamination, by minimizing the number of connections and disconnections needed during a given treatment session. By enabling a dwell or wait mode on the machine  16 , the cartridge  18  can remain mounted to the machine  16  after one treatment session for an extended dwell or break period and allow reconnection and continued use by the same person in a subsequent session for any reason, for example, or in a continuation of a session following x-rays or testing. 
     The cartridge  18  can therefore provide multiple intermittent treatment sessions during a prescribed time period, without exchange of the cartridge  18  after each treatment session. The time of use confines are typically prescribed by the attending physician or technical staff for the treatment center to avoid bio-contamination and can range, e.g., from 48 hours to 120 hours, and more typically 72 to 80 hours. The cartridge  18  can carry a bacteriostatic agent that can be returned to the patient (e.g., an anticoagulant, saline, ringers lactate, or alcohol) and/or be refrigerated during storage. 
     The single step loading function can be accomplished in various ways. In the illustrated embodiment (see  FIG. 2 ), the machine  16  includes a chassis panel  26  and a panel door  28 . The door  28  moves on a pair of rails  31  in a path toward and away from the chassis panel  26  (as shown by arrows in  FIG. 2 ). A slot  27  is formed between the chassis panel  26  and the door  28 . As  FIGS. 4 to 6  show, when the door  28  is positioned away from the panel  26 , the operator can, in a simple vertical (i.e., downward) motion (see  FIG. 4 ), move a fluid processing cartridge  18  into the slot  27  and, in a simple horizontal (i.e., sideway) motion (see  FIG. 5 ), fit the cartridge  18  onto the chassis panel  26 . When properly oriented, the fluid processing cartridge  18  may rest on the rails  31  to help position the cartridge  18 . As  FIG. 6  shows, movement of the door  28  toward the panel  26  engages and further supports the cartridge  18  for use on the panel  26 . This position of the door  28  will be called the closed position. 
     The machine  16  preferably includes a latching mechanism  30  and a sensor  32  (see  FIG. 2 ) to secure the door  28  and cartridge  18  against movement before enabling circulation of fluid through the cartridge  18 . 
     The cartridge  18  can be constructed in various ways.  FIG. 3  (in an assembled view) and FIG.  7 (in an exploded view) show an embodiment of a cartridge  18 , which can be used to in association with the machine  16  to perform a selected treatment modality. In this embodiment, the cartridge  18  includes a preformed support frame  400  manufactured, e.g., by thermoforming polystyrene or another comparable material. The support frame  400  presents an exterior surface  402  (shown in plane view  FIG. 8 ) and an oppositely facing interior surface  404  (shown in plane view in  FIG. 9 ). 
     When installed for use on the machine  16 , the exterior surface  402  is oriented toward the door  28 , and the interior surface  404  is oriented toward the chassis panel  26 . An icon  440  imprinted on the exterior surface  402  (see  FIG. 8 ) guides the operator in mounting the frame  400  on the chassis panel  26  in the proper front-to-back and up-and-down orientation. 
     As  FIG. 7  best shows, the interior surface  404  of the frame  400  carries a flexible fluid circuit  408 . In the illustrated embodiment, the flexible fluid circuit  408  comprises one or more individual fluid management modules. The modules can be dedicated to different processing functions. For example, one module can handle fluid being removed from the body, while another module can handle fluid being supplied to the body. These processing functions can be synchronized by various means of orienting the modules with each other, and with the common hardware elements on the machine  16 . 
     In the illustrated embodiment (see  FIG. 7 ), two modules  424  and  426  are provided, which are shown individually in FIGS.  10  and  11 , respectively. As  FIG. 7  shows, lengths of flexible tubing  418  communicate with modules  424  and  426  of the flexible fluid circuit  408 , to convey fluid to and from the modules  424  and  426 . Together, the flexible fluid circuit  408  and tubing  418  form a fluid processing circuit  420 . 
     The modules  424  and  426  themselves can be constructed in various ways, depending upon the particular processing functions that are intended to be performed. 
     In the illustrated embodiment (see  FIGS. 10 and 11 ), the modules  424  and  426  take the form of fluid circuit bags  434  and  436 . Each bag  434  and  436  is formed, e.g., by radio frequency welding together two sheets of medical plastic material (e.g., polyvinyl chloride). Each bag  434  and  436  includes an interior array of radio frequency seals forming fluid paths, chamber regions, sensor regions, and clamp regions. 
     In the illustrated embodiment, when secured to the interior surface  404  of the frame  400  (see  FIGS. 7 and 9 ), the bag  434  rests over the bag  436 , so that portions of the fluid circuits defined by the modules  424  and  426  overlay one another. As will be explained later, this makes possible synchronization of different processing functions using common hardware elements on the machine  16 . 
     II. Telemetry for the System 
     The system  10  can also include a telemetry network  22  (see  FIGS. 1 and 18 ). The telemetry network  22  provides the means to link the machine  16  in communication with other locations  254  via, e.g., cellular networks, digital networks, modem, Internet, or satellites. A given location  254  can, for example, receive data from the machine  16  at the treatment location or transmit data to a data transmission/receiving device  296  at the treatment location, or both. A main server  256  can monitor operation of the machine  16  or therapeutic parameters of the person undergoing the specified treatment. The main server  256  can also provide helpful information to the person undergoing the specified treatment. The telemetry network  22  can download processing or service commands to the data receiver/transmitter  296 . 
     1. Remote Information Management 
       FIG. 18  shows a representative telemetry network  22  in association with a machine  16  that carries out a specified treatment modality. The telemetry network  22  includes the data receiver/transmitter  296  coupled to the machine  16 . The data receiver/transmitter  296  can be electrically isolated from the machine  16 , if desired. The telemetry network  22  also includes a main data base server  256  coupled to the data receiver/transmitter  296  and an array of satellite servers  260  linked to the main data base server  256 . 
     The data generated by the machine  16  during operation is processed by the data receiver/transmitter  296 . The data is stored, organized, and formatted for transmission to the main data base server  256 . The data base server  256  further processes and dispenses the information to the satellite data base servers  260 , following pre-programmed rules, defined by job function or use of the information. Data processing to suit the particular needs of the telemetry network  22  can be developed and modified without changing the machine  16 . 
     The main data base server  256  can be located, e.g., at the company that creates or manages the system  10 . The satellite data base servers  260  can be located, for example, at the residence of a designated remote care giver for the person, or at a full time remote centralized monitoring facility staffed by medically trained personnel, or at a remote service provider for the machine  16 , or at a company that supplies the machine  16  or the processing cartridge  18 . 
     Linked to the telemetry network  22 , the machine  16  acts as a satellite. The machine  16  performs specified therapy tasks while monitoring basic safety functions and providing the person at the treatment location notice of safety alarm conditions for resolution. Otherwise, the machine  16  transmits procedure data to the telemetry network  22 . The telemetry network  22  relieves the machine  16  from major data processing tasks and related complexity. It is the main data base server  256 , remote from the machine  16 , that controls the processing and distribution of the data among the telemetry network  22 , including the flow of information and data to the person undergoing therapy. The person at the treatment location can access data from the machine  16  through the local data receiver/transmitter  296 , which can comprise a laptop computer, handheld PC device, web tablet, cell phone, or any unit capable of data processing. 
     The machine  16  can transmit data to the receiver/transmitter  296  in various ways, e.g., electrically, by phone lines, optical cable connection, infrared light, or radio frequency, using cordless phone/modem, cellular phone/modem, or cellular satellite phone/modem. The telemetry network  22  may comprise a local, stand-alone network, or be part of the Internet. 
     For example, when the machine  16  notifies the person at the treatment location of a safety alarm condition, the safety alarm and its underlying data can also be sent to the main server  256  on the telemetry network  22  via the receiver/transmitter  296 . When an alarm condition is received by the main server  256 , the main server  256  can locate and download to the receiving device  296  the portion of the operator&#39;s manual for the machine that pertains to the alarm condition. Based upon this information, and exercising judgment, the operator/user can intervene with operation of the machine  16 . In this way, the main server  256  can provide an automatic, context-sensitive help function to the treatment location. The telemetry network  22  obviates the need to provide on-board context-sensitive help programs for each machine  16 . The telemetry network  22  centralizes this help function at a single location, i.e., a main server  256  coupled to all machines  16 . 
     The telemetry network  22  can relay to an inventory server  262  supply and usage information of components used for the treatment modality. The server  262  can maintain treatment site-specific inventories of such items, such as cartridges  18 , ancillary processing materials, etc. The company or companies that supply the machine  16 , the processing cartridge  18 , or the ancillary processing material to the treatment location  12  can all be readily linked through the telemetry network  22  to the inventory server  262 . The inventory server  262  thereby centralizes inventory control and planning for the entire system  10 , based upon information received in real time from each machine  16 . 
     The telemetry network  22  can relay to a service server  264  hardware status information for each machine  16 . The service server  264  can process the information according to preprogrammed rules, to generate diagnostic reports, service requests or maintenance schedules. The company or companies of the system  10  that supply or service the machine  16  can all be readily linked through the telemetry network  22  to the service server  264 . The service server  264  thereby centralizes service, diagnostic, and maintenance functions for the entire system  10 . Service-related information can also be sent to the treatment location  12  via the receiving device  296 . 
     The telemetry network  22  can also relay to a treatment monitoring server  266 , treatment-specific information pertaining to the therapy provided by each machine  16 . Remote monitoring facilities  268 , staffed by medically trained personnel, can be readily linked through the telemetry network  22  to the treatment monitoring server  266 , which centralizes treatment monitoring functions for all treatment locations served by the system  10 . 
     The telemetry network  22  can also provide through the device  296  an access portal for the person undergoing treatment to the myriad services and information contained on the Internet, e.g., over the web radio and TV, video, telephone, games, financial management, tax services, grocery ordering, prescriptions purchases, etc. The main server  256  can compile diagnostic, therapeutic, and/or medical information to create a profile for each person served by the system  10  to develop customized content for that person. The main server  256  thus provide customized ancillary services such as on line training, billing, coaching, mentoring, uplinks to doctors, links to patient communities, and otherwise provide a virtual community whereby persons using the system  10  can contact and communicate via the telemetry network  22 . 
     The telemetry network  22  thus provides the unique ability to remotely monitor equipment status, via the internet, then provide information to the user, also via the internet, at the location of the equipment. This information can include, e.g., what page of the operator&#39;s manual would be the most helpful for their current operational situation, actual data about the equipment&#39;s performance (e.g., could it use service, or is it set up based on the caretaker&#39;s recommendations), data about the current session, i.e., buttons pressed, alarms, internal machine parameters, commands, measurements. 
     The remote site can monitor the equipment for the same reasons that the user might. It can also retrieve information about the machine  16  when it is turned off because the telemetry device is self-powered. It retains all information about the machine over a period of time (much like a flight recorder for an airplane). 
     2. On-Site Programming 
     The main server  256  on the telemetry network  22  can also store and download to each machine  16  (via the device  296 ) the system control logic and programs necessary to perform a desired treatment modality. Programming to alter a treatment protocol to suit the particular needs of a single person at a treatments site can be developed and modified without a service call to change the machine  16  at any treatment location, as is the current practice. System wide modifications and revisions to control logic and programs that condition a machine  16  to perform a given treatment protocol can be developed and implemented without the need to retrofit each machine  16  at all treatment locations by a service call. This approach separates the imparting of control functions that are tailored to particular procedures, which can be downloaded to the machine  16  at time of use, from imparting safety functions that are generic to all procedures, which can be integrated in the machine  16 . 
     Alternatively, the control logic and programs necessary to perform a desired treatment protocol procedure can be carried in a machine readable format on the cartridge  18 . Scanners on the machine  16  automatically transfer the control logic and programs to the machine  16  in the act of loading the cartridge  18  on the machine  16 . Bar code can be used for this purpose. Touch contact or radio frequency silicon memory devices can also be used. The machine  16  can also include local memory, e.g., flash memory, to download and retain the code. 
     For example, as  FIG. 2  shows, the machine  16  can include one or more code readers  270  on the chassis panel  26 . The frame  400  carries, e.g., on a label or labels, a machine readable (e.g., digital) code  272  (see  FIG. 3 ) that contains the control logic and programs necessary to perform a desired treatment protocol using the cartridge  18 . Loading the cartridge  18  on the machine  16  orients the code  272  to be scanned by the reader(s)  270 . Scanning the code  272  downloads the control logic and programs to memory. The machine  16  is thereby programmed on site. 
     The code  272  can also include the control logic and programs necessary to monitor use of the cartridge  18 . For example, the code  272  can provide unique identification for each cartridge  18 . The machine  16  registers the unique identification at the time it scans the code  272 . The machine  16  transmits this cartridge  18  identification information to the main server  256  of the telemetry network  22 . The telemetry network  22  is able to uniquely track cartridge  18  use by the identification code throughout the system  10 . 
     Furthermore, the main server  256  can include preprogrammed rules that prohibit multiple use of a cartridge  18 , or that limit extended uses to a prescribed period of time. An attempted extended use of the same cartridge  18  on any machine  16 , or an attempted use beyond the prescribed time period, will be detected by the machine  16  or the main server  256 . In this arrangement, the machine  16  is disabled until an unused cartridge  18  is loaded on the machine  16 . 
     Prior to undertaking set up pressure testing and priming of the cartridge  18 , the machine  16  can also be conditioned to sense, e.g., by ultrasonic means, the presence of fluid in the cartridge. The presence of fluid indicates a reprocessed cartridge. In this arrangement, the machine  16  is disabled until a dry, unused cartridge  18  is loaded on the machine  16 . 
     Service cartridges can also be provided for the machine  16 . A service cartridge carries a code that, when scanned by the reader or readers on the chassis panel  26  and downloaded to memory, programs the machine  16  to conduct a prescribed service and diagnostic protocol using the service cartridge  18 . 
     III. Representative Systems for Conducting Hemofiltration 
     The particular configuration of the machine  16  and the fluid processing circuit  420 , which the tubing  418  and flexible fluid circuit  408  form, can vary according to the processing objectives of the system  10 . As before stated, the system  10  is well suited for treatment modalities during which one fluid is removed from the body and replaced with another fluid in a controlled fashion, e.g., hemofiltration (HF), hemodialysis (HD), hemodialysis with hemofiltration (HDF), and peritoneal dialysis (PD). 
     For the purpose of illustration,  FIG. 12  schematically shows a fluid circuit FC(HF) for carrying out hemofiltration. The fluid circuit FC(HF) supports the removal of blood from an individual and the separation of waste fluid from the blood using a hemofilter  34 . The fluid circuit FC(HF) also supports the return of treated blood and replacement fluid to the individual. The fluid circuit FC(HF) also supports an ultrafiltration function. 
     The flexible fluid circuit  420  carried by the frame  400  and the machine  16  can be readily configured to form this circuit FC(HF) and thereby conduct hemofiltration. A person of skill in the art will readily appreciate how the fluid circuit  420  and machine  16  can be configured to perform other treatment modalities, as well. 
     In the illustrated implementation, the first module  424  is configured to handle waste fluid, and the second module  426  is configured to handle replacement fluid. 
     As  FIG. 10  shows, the waste fluid management module  424  includes fluid waste balancing chambers  212 R/ 214 R and associated waste fluid clamp regions  220  and  222 . The location of these elements in the fluid circuit FC(HF)are also shown schematically in  FIG. 12 . 
     As  FIG. 11  shows, the replacement fluid management module  426  includes corresponding replacement fluid balancing chambers  212 F/ 214 F and associated replacement fluid clamp regions  224  and  226 . The location of these elements in the fluid circuit FC(HF)are also shown schematically in  FIG. 12 . 
     When the modules  424  and  426  are mounted against the interior surface  404  of the frame  400  (see  FIG. 9 ), the chambers  212 R/ 214 R and  212 F/ 214 F and the clamp regions  222 / 220  and  224 / 226  communicate in the same plane. When the frame  400  is mounted for use on the machine  16 , the overlaying chambers  212 R/ 214 R and  212 F/ 214 F and clamp regions  222 / 220  and  224 / 226  operatively engage common machine elements on the machine  16  to carry out volumetric fluid balancing of replacement fluid in proportion to waste removal, without use of weight sensors. When the frame  400  is mounted for use on the machine  16 , the modules  424  and  426 , in association with hardware elements on the machine  16 , also accomplish ultrafiltration. 
     In the illustrated embodiment (see  FIGS. 7 and 8 ), an exterior surface  406  of the frame  400  is slightly recessed or concave. When the frame  400  is mounted on the machine  16 , this recessed frame surface  406  nests within a correspondingly raised surface  407  on the door  28  (see  FIG. 13 ). When so nested, convex or domed frame regions  412 , which project above the surface  406  of the frame  400  (see  FIGS. 7 and 8 ) fit within mating concave indentations  206 ′ and  208 ′ on the door  28 . 
     The fluid balancing chambers  212 R/ 214 R and  212 F/ 214 F rest in an overlying relationship within these domed regions  412  on the opposite interior surface  404  of the frame  400  (see  FIG. 8 ). When the frame  400  is mounted on the machine  16 , and the door  28  closed, the interior surface  404  faces the chassis panel  28 , and the fluid balancing chambers  212 R/ 214 R and  212 F/ 214 F rest within concave indentations  206  and  208  formed on the chassis panel  26  (see  FIG. 2 ). When the frame  400  is mounted on the machine  16 , and the door  28  closed, the flexible chambers  212 R/ 214 R and  212 F/ 214 F are thereby enclosed between the indentations  206 / 208  on the chassis panel  26  and the convex regions  412  of the frame  400  (which themselves nest within the concave indentations  206 ′/ 208 ′ on the door  28 ). Expansion of the flexible chambers  212 R/ 214 R and  212 F/ 214 F as a result of fluid introduction is thereby restrained to a known maximum volume, generally approximately between 10 and 50 cc, preferably approximately between 20 and 40 cc, more preferably approximately 25 cc, defined between the chassis chambers  206 / 208  and the convex frame regions  412 . 
     As  FIG. 8  shows, cut-outs  410  in the surface  406  expose the overlaying flexible clamp regions  222 / 220  and  224 / 226  to contact with the four clamping pads  450  mounted on the door  28  (see  FIG. 13 ) and hardware clamping elements  244 ,  246 ,  248 , and  250  on the chassis panel  26  (see  FIG. 2 ). In operation, the clamping elements  244 ,  246 ,  248 , and  250  are caused to project from the chassis panel  26  to press the overlying clamp regions  222 / 220  and  224 / 226  against the clamping pads  450  on the door  28 . Synchronized valve functions are thereby made possible, as will be described later. 
     Referring back to  FIG. 8 , another cut-out  413  in the surface  406  exposes a portion of the fluid circuit  408  for blood leak sensing functions, as will also be described later. 
     Surrounding the surface  406  are recessed channel regions  414   a  to  414   j,  which are formed in the exterior surface  402 . These recessed channel regions  414   a  to  414   j  (identified in  FIG. 8 ) accommodate the passage of the lengths of flexible tubing  418  that communicate with the flexible fluid circuit  408 , to form the fluid processing circuit  420 . The recessed regions  414   a  to  414   j  form channels that guide and restrain the tubing  418  within the frame  400 . Multiple cut-outs  442   a  to  442   i  are formed along the recessed regions  414   a  to  414   j,  to expose intervals of the tubing  418  for engagement with clamps or sensors on the machine  16 , as will be described. 
     As  FIGS. 7  show, a cover member  416  made, e.g., from rigid or semi-rigid paper or plastic, is desirably secured to the exterior surface  402  of the frame  400  to overlay and close the recessed channel regions  414 , in which the tubing  418  is carried ( FIG. 3  shows the exterior surface  402  with the cover member  416  installed). 
     As  FIG. 8  shows, portions of tubing  418  extend beyond the support frame  400  for connection with the patient and other external items making up the fluid processing circuit  420 , as will be described later. Cartridge  18  may extend beyond the edge of machine  16 . 
     Portions of the tubing  418  also communicate with peristaltic pump tubes  94 ,  145 ,  155 , and  201  located in the surface  406  (see  FIG. 8 ). Cut-outs  446   a  to  446   c  are formed in the region  406  beneath the pump tubes  94 ,  145 ,  155 , and  201 , to expose the pump tubes  94 ,  145 ,  155 , and  201  for engagement with the corresponding peristaltic pump rollers  92 ,  144 , and  152  on the chassis panel  26  (see  FIG. 2 ) and the corresponding pump races  362  on the door  28  (see  FIG. 13 ). 
     Further regarding the configuration of the fluid processing circuit  420  (see  FIG. 8 ), as adapted to conform to the hemofiltration circuit FC(HF) shown in  FIG. 12 , the flexible tubing  72  forms the arterial blood supply path, with an appropriate distal connector to couple to an arterial blood access site. The tubing  72  is guided by a recessed channel  414   a  into the frame  400 . Cut-outs  442   a  and  442   b  expose the tubing  72  for engagement with an arterial blood line air sensor  98  and arterial blood line clamp  96 . 
     The tubing  72  is coupled with the pump tube  94 , which spans the cut-out  446   a  in the frame  400 , for engagement with the blood pump  92  on the chassis panel  26  (see  FIG. 2 ). 
     Tubing  78  extends from the pump tube region  94  in a recessed channel  414   b  in the frame  400 . The tubing  78  extends beyond the frame  400  and includes the connector  82  to couple the arterial blood path to the inlet of a hemofilter  34  (see  FIG. 12 ). 
     The placement of the cut-out  442   a  (and associated air sensor  98  on the machine  16 ) upstream of the hemofilter  34  allows air bubbles to be detected prior to entering the hemofilter  34 . This location is desirable, because, in the hemofilter  34 , air bubbles break up into tiny micro-bubbles, which are not as easily detected as bubbles upstream of the hemofilter  34 . Placement of the air sensor  98  upstream of the hemofilter  34  also serves the additional purpose of detecting air when the blood pump  92  is operated in reverse, to rinse back blood to the patient. The air sensor  98  also detects if the arterial blood line is clamped or otherwise occluded, to thereby allow terminate operation of the arterial blood pump  92  when this condition occurs. Air sensor  98  can also sense a clamped or occluded arterial line while the pump turns. The resulting negative pressure degasses the blood which is sensed by the air sensor, and an alarm is sounded. If air by chance enters the arterial blood line, e.g., by a faulty connection or an air leak, the air sensor  98  will detect this condition and terminate operation of the arterial blood pump before the air enters the hemofilter. 
     As  FIG. 8  shows, the tubing  84  extends beyond the frame  400  and includes a distal connector  86  to couple to the blood outlet of the hemofilter  34  (see  FIG. 12 ). The tubing  84  is led across the frame  400  through a recessed channel  414   c.  Cut-away regions  442   c  and  442   d  on the frame  400  expose the tubing  84  for engagement with the venous blood line air sensor  108  and venous S blood line clamp  112  (see  FIG. 12 ). The tubing  84  then extends beyond the frame  400 , and carries an appropriate distal connector to couple to venous blood access site. 
     As  FIG. 8  shows, the flexible tubing  118  extends beyond the frame  400  and carries a distal connector  120  to couple to the waste outlet of the hemofilter  34  (see  FIG. 12 ). The tubing  118  thereby serves to convey waste fluid for fluid balancing and discharge. The flexible tubing  118  enters a recessed channel  414   d  in the frame  400  and joins a connector C 8 . The connector C 8  couples the tubing  118  to the waste fluid management module  424 , and through the module  424  to ultrafiltration pump tube  145  (through connector C 1 ) and the waste pump tube  155  (through connector C 7 ). The pump tube  145  spans a cut-out  446   b  in the frame  400  to connector C 2 , for engagement with the ultrafiltration pump  144  on the chassis panel  26  (see  FIG. 2 ). The pump tube  155  spans a cut away region  446 c in the frame  400  to connector C 3 , for engagement with the waste fluid header region  154  of the dual header waste and replacement pump  152  on the chassis panel  26  (see  FIG. 2 ). 
     Connectors C 2  and C 3  are fluidically coupled via the waste fluid management module  424  (see  FIG. 10 ) to connectors C 10  and C 4 . As  FIG. 8  shows, the flexible tubing  122  is coupled by the connector C 4  to an outlet of the waste management module  424 . The tubing  122  is guided through a recessed channel  414   e  in the support frame  400 . Cut-away region  442   e  on the frame  400  expose the tubing  122  for engagement with the waste line clamp  166 . The tubing  122  then extends beyond the frame  400 , with an appropriate distal connector  124  to couple to a waste bag or an external drain. It is through this tubing  122  that waste fluid is discharged after fluid balancing. An in-line air break  170  (see  FIG. 12 ) can be provided in communication with the tubing  122  downstream of the waste clamp  166 , to prevent back flow of contaminants from the waste bag or drain. 
     Referring to  FIG. 8 , the flexible tubing  172  serves to convey replacement fluid. The tubing  172  extends outside the frame  400  and includes a distal connector  174  that enables connection to multiple containers of replacement fluid  176  (see  FIG. 12 ). The tubing  172  is guided by a recessed channel  414   f  within the frame  400 . Cut-away regions  442   f  and  442   g  on the frame  400  expose the tubing  172  for engagement with an in line air sensor  182  and replacement fluid clamp  188  (see  FIG. 12 ). 
     Flexible tubing  430  is guided through a recessed channel  414   g  in the support frame  400  between two t-connectors, one in the arterial blood tubing  72  and the other in the replacement tubing  172 . The tubing  430  serves as the priming or bolus branch path  192 , as will be described. A cut-away region  442   h  on the frame  400  exposes the tubing  430  for engagement with the priming clamp  194  on the machine  16  (see  FIG. 12 ). 
     The replacement fluid tubing  172  is further guided by the recessed channel  414   h  in the frame  400  to the replacement fluid pump tube  201  (previously described), which is also coupled via a connector C 5  to the replacement fluid management module  426  of the flexible fluid circuit  408 . As  FIG. 11  also shows, connector C 5  is also fluidically coupled via the replacement fluid management module  426  to the connectors C 6  and C 9 . The pump tube  201  spans the cut away region  446   d  in the frame  400 , for engagement with the replacement fluid header region  200  of the dual header waste and replacement pump  152  on the chassis panel  26  (see  FIG. 2 ). 
     Flexible tubing  432  is coupled by a connector C 6  to the replacement fluid module  426 . The flexible tubing  432  is guided through a recessed channel  414   i  in the support frame to a t-connector, which joins the replacement tubing  172  in the region immediately downstream of the connection with the replacement fluid pump tube  201 . The tubing  432  serves as the relief path  240  that prevents overfilling of the fluid balancing compartments, as will be described. 
     Flexible tubing  428  is coupled by a connector C 9  to the replacement fluid management module  426 . The tubing  428  is guided through a recessed channel  414   j  in the support frame  400  in a small loop outside the frame  400  and is coupled by a t-connector to the venous blood return tubing  84 . It is through this path that replacement fluid is added to the venous blood being returned to the patient. 
     The bags  434  and  436  are secured in overlaying alignment to the interior surface  404  of the frame  400  by the connectors C 1  to C 10 , previously described. 
       FIG. 10  shows the waste management fluid circuit contained in the bag  434 , as it would appear if viewed from interior surface  404  of the support frame  400  (as  FIG. 9  also shows). The bag  434  is shown in association with the ultrafiltration pump tube  145  and waste fluid pump tube  155  that are also carried on the region  406  of the support frame  400 . 
     The fluid circuit in the bag  434  includes the waste path  138  that leads to the waste side compartments  212 R and  214 R (for fluid balancing) by way of the waste pump  155  and the waste path  136  by way of the ultrafiltration pump  145  that bypasses the waste side compartments  212 R and  214 R (for ultrafiltration). The flow paths in the waste fluid circuit in the bag  434  also include the exposed waste inlet clamp regions  220 , to engage the valve assemblies  246  and  248  to control inflow of waste fluid into the waste compartments  212 R and  214 R, and the exposed waste outlet clamp regions  222 , to engage the valve assemblies  244  and  250  to control outflow of waste fluid from the waste compartments  212 R and  214 R. The fluid circuit also includes the pressure sensor region  160 , to engage the pressure sensor  156  (see  FIG. 15 ) downstream of the waste and replacement fluid pump  152 . 
       FIG. 11  shows the replacement fluid management circuit contained in the bag  436 , as it would appear if viewed from the interior surface  404  of the support frame  400  (as  FIG. 8  also shows). The bag  436  is shown in association with the replacement fluid pump tube  201  that is also carried in the region  406  of the support frame  400 . The replacement fluid pump tube  201  is located alongside the waste fluid pump tube  155 , on region  200  for concurrent engagement with the dual header waste and replacement pump  152  on the chassis panel  26  (see  FIG. 2 ). 
     The fluid circuit in the bag  436  includes the replacement fluid paths which lead to and from the replacement side compartments  212 F and  214 F. The fluid circuit also includes the inlet clamp regions  224 , to engage the valve assemblies  244  and  250  on the machine  16  to control inflow of replacement fluid into the replacement side compartments  212 F and  214 F; and the outlet clamp regions  226 , to engage the valve assemblies  246  and  248  on the machine  16  to control outflow of replacement fluid from the replacement side compartments  212 F and  214 F. The fluid circuit includes a sensor region  204 , to engage the pressure sensor  202  (see  FIG. 15 ) downstream of the waste and replacement pump  152 . 
     When the bags  434  and  436  are mounted in overlaying relationship on the interior frame surface  404  (as  FIG. 9  shows), the replacement side compartments  212 F and  214 F and the waste side compartments  212 R and  214 R together rest in the convex recesses  412  in the region  406  of the exterior frame surface  402 . The inlet clamp regions of the waste compartments  212 R and  214 R formed on the waste panel  234  overlay the outlet clamp regions of the replacement compartments  212 F and  214 F formed on the replacement panel  232 , and vice versa. 
     The entry and exit paths serving the waste and replacement compartments formed in the bags  434  and  436  (shown in  FIG. 9 ) are all located at the top of the chambers  212 R,  214 R,  212 F, and  214 F. Priming is achieved, as the paths are top-oriented. Furthermore, due to the overlaying relationship of bags  434  and  436 , the clamping regions  220 ,  222 ,  224 , and  226  are arranged to overlay one another. The overlaying arrangement of the clamping regions  220 ,  222 ,  224 , and  226  serving the waste and replacement compartments simplifies the number and operation of the inlet and outlet valve assemblies  216  and  218  on the machine  16 . Since the inlet clamp regions  224  for the replacement compartments  212 F and  214 F overlay the outlet clamp regions  222  for the waste compartments  212 R and  214 R, and vice versa, only four clamping elements  244 ,  246 ,  248 ,  250  need be employed to simultaneously open and close the overlaying eight clamp regions. 
     1. Achieving Synchronized Volumetric Fluid Balancing 
     In use, as  FIG. 14  shows, the first clamping element  244  is movable into simultaneous clamping engagement with the inlet clamp region  224  of the replacement compartment  212 F (in the replacement fluid module bag  436 ) and the outlet clamp region  222  of the waste compartment  212 R (in the waste fluid module bag  434 ), closing both. Likewise, the fourth clamping element  250  is movable into simultaneous clamping engagement with the inlet clamp region  224  of the replacement compartment  214 F (in the replacement fluid module bag  436 ) and the outlet clamp region  222  of the waste compartment  214 R (in the waste fluid module bag  434 ). 
     The second clamping element  246  is movable into simultaneous clamping engagement with the outlet clamp region  226  of the replacement compartment  212 F and the inlet clamp region  220  of the waste compartment  212 R, closing both. Likewise, the third clamping element  248  is movable into simultaneous clamping engagement with the outlet clamp region  226  of the replacement compartment  214 F and the inlet clamp region  220  of the waste compartment  214 R, closing both. 
     The machine  16  toggles operation of the first and third clamping elements  244 ,  248  in tandem, while toggling operation the second and fourth clamping elements  246 ,  250  in tandem. When the first and third clamping elements  244 ,  248  are operated to close their respective clamp regions, replacement fluid enters the replacement compartment  214 F to displace waste fluid from the underlying waste compartment  214 R, while waste fluid enters the waste compartment  212 R to displace replacement fluid from the overlaying replacement compartment  212 F. When the second and fourth clamping elements  246 ,  250  are operated to close their respective clamp regions, replacement fluid enters the replacement compartment  212 F to displace waste fluid from the underlying waste compartment  212 R, while waste fluid enters the waste compartment  214 R to displace replacement fluid from the overlaying replacement compartment  214 F. 
       FIGS. 15 and 16  show a mechanically linked pump and valve system  300  that can be arranged on the chassis panel  26  of the machine  16  and used in association with the flexible fluid circuit  408 . 
     The system  300  includes three electric motors  302 ,  304 , and  306 . The first motor  302  is mechanically linked by a drive belt  308  to a dual header waste and replacement pump  152 . The second motor  304  is mechanically linked by a drive belt  310  to a blood pump  92 . The third motor  306  is mechanically linked by a drive belt  312  to a ultrafiltration pump  144 . 
     A drive belt  314  also mechanically links the first motor to the first, second, third, and fourth clamping elements  244 ,  246 ,  248 , and  250 , via a cam actuator mechanism  316 . The cam actuator mechanism  316  includes, for each clamping element  244 ,  246 ,  248 , and  250  a pinch valve  318  mechanically coupled to a cam  320 . The cams  320  rotate about a drive shaft  322 , which is coupled to the drive belt  314 . 
     Rotation of the cams  320  advances or withdraws the pinch valves  318 , according to the surface contour machined on the periphery of the cam  320 . When advanced, the pinch valve  318  closes the overlying clamp regions of the fluid circuit module bags  424  and  426  that lay in its path. When withdrawn, the pinch valve  318  opens the overlying clamp regions. 
     The cams  320  are arranged along the drive shaft  322  to achieve a predetermined sequence of pinch valve operation. During the sequence, the rotating cams  320  first simultaneously close all the clamping elements  244 ,  246 ,  248 , and  250  for a predetermined short time period, and then open clamping elements  244  and  248 , while closing clamping elements  246  and  250  for a predetermined time period. The rotating cams  320  then return all the clamping elements  244 ,  246 ,  248 , and  250  to a simultaneously closed condition for a short predetermined time period, and then open clamping elements  246  and  250 , while closing clamping elements  244  and  248  for a predetermined time period. 
     The sequence is repeated and achieves the balanced cycling of replacement fluid and waste fluid through the module bags  424  and  426 , as previously described. A chamber cycle occurs in the time interval that the valve elements  244 ,  246 ,  248 , and  250  change from a simultaneously closed condition and return to the simultaneously closed condition. 
     In a preferred embodiment (see  FIG. 17 ), each clamping element  244 ,  246 ,  248 , and  250  comprises a valve pin  500  movable within a valve slot  506  in the chassis panel  26 . A rotating bearing surface  502  at one end of the valve pin  500  rides on the cam surface  504  of the corresponding rotating cam  320 . As the cam  320  rotates, the cam surface  504  presents regions of increasing or decreasing radius, causing the pin  500  to reciprocate within the valve slot  506  toward and away from the door  28 , which, during use of the fluid circuit  408 , faces the chassis panel  26  in the closed position. 
     A pinch valve  318  is carried at the opposite end of the valve pin  500 . The pinch valve  318  includes a pinch valve chamber  508 , in which the valve pin  500  rests. A spring  510  in the pinch valve chamber  508  couples the pinch valve  318  to the valve pin  500 . The spring  510  applies a fixed valve force against the pinch valve  318 , in the absence of physical contact between the end of the valve pin  500  and the pinch valve  318 . The spring  510  thereby mediates against over- and under-valving effects as a result of small changes in tolerance between the pin  500  and pinch valve  318 , fluid circuit module bag  424  and  426  thickness, and the closed gap between door  28  and chassis  26 . 
     When mounted for use on the chassis panel  26 , with the door  28  closed, the fluid circuit  408  is sandwiched between the panel  26  and the door  28 . Each pinch valve  318  is aligned with a valve plate  512  carried by the door  28 . The valve plate  512  is made from a hard plastic or metallic material. The valve plate  512  rests against a disk  514  on the door  28 , which can be made of rubber or another elastomeric material. The disk  514 , which can also be a spring, allows the valve plate  512  to move or “float” when the pinch valve applies a valve force. The valve plate  512  thereby accounts for any lack of perpendicularity between the pinch valve  318  and the valve plate  512 . 
     Movement of the pinch valve  318  toward the door  28  (as the cam surface  504  presents regions of increasing radius) pinches the intermediate, aligned clamp region in the fluid circuit  56  (comprised of modules  424  and  426  overlying one another) between the pinch valve  318  and the valve plate  512 , thereby closing the valve region. Likewise, movement of the pinch valve  318  toward the door  28  (as the cam surface  504  presents regions of decreasing radius) separates the pinch valve  318  from the valve plate  514 , thereby opening the intermediate valve region. The cam actuator mechanism  316  mechanically links the clamping elements  244 ,  246 ,  248 , and  250  ratiometrically with the first motor  302 . As the motor  302  increases or decreases the speed of the dual header waste and replacement pump  152 , the operation of the clamping elements  244 ,  246 ,  248  and  250  increases or decreases a proportional amount. 
     In a preferred embodiment, the ratio is set so that the flow rate per unit time through the waste pump header region  154  (i.e., through waste path  434 ) approximately equals three-fourths of the volume of the waste compartment  212 R/ 214 R, while maintaining the cycle rate of 10 cycles per minute for a waste fluid flow rate of approximately 200 ml/min. For example, if the chamber volume is 25 cc, the cycle occurs after 18 to 21 cc of waste fluid enters the compartment. In other embodiments, the cycle rate is 9–11 cycles per minute for a waste fluid flow rate of approximately 180–220 ml/min, or the cycle rate is 8–12 cycles per minute for a waste fluid flow rate of approximately 160–240 ml/min. 
     In the illustrated embodiment, the waste pump header  155  is made smaller in diameter than the replacement fluid header  201 . Thus, during operation of the dual header pump  152 , which is made up of pump regions  154  and  200 , the flow rate through the replacement fluid header region  200 / 201  (through replacement fluid path  426 ) will always be larger than the flow rate through the waste pump header region  154 / 155  (through waste path  424 ). Due to the higher flow rate through the replacement fluid path  426 , a pressure relief path  438  (see  FIG. 11) and 432  (see  FIGS. 12 and 8 ) with pressure relief bypass valve  242  (see  FIG. 15 ) is provided, to prevent overfilling. In the illustrated embodiment, the valve  242  is a mechanically spring biased pressure regulator, and serves the pressure regulation and bypass function of the machine  16 . 
     In this arrangement, the in-line compartment that receives waste fluid will fill to approximately three-fourths of its volume during each cycle, displacing an equal amount of replacement fluid from its companion compartment. At the same time, the other in-line compartment that receives replacement fluid will fill completely. If the compartment completely fills with replacement fluid before the end of the cycle, the pressure relief bypass valve  242  (see  FIG. 15 ) will open to circulate replacement fluid through the relief path  240 , made up of  438 , C 6 , and  432  (see  FIG. 12 ), to prevent overfilling. During the next cycle, waste fluid in the compartment will be completely displaced by the complete fill of replacement fluid in its companion compartment. 
     The provision of a higher flow rate in the replacement fluid path also facilitates initial priming (as will be described later). only several chamber cycles are required to completely prime the in-line containers  212  and  214  with replacement fluid before fluid balancing operations begin. 
     The pump and valve system  300  used in association with the fluid circuit  408  achieves accurate fluid balancing, e.g., during hemofiltration, hemodialysis, hemodialysis with hemofiltration, and peritoneal dialysis. 
     B. Fluid Flow Path Dimensions 
     In one embodiment, key functional regions within the flexible fluid circuits are formed to possess dimensions that lay within critical ranges, to thereby achieve desired fluid flow conditions, pressure sensing conditions, fluid balancing functions, and valve functions. For example, each fluid balancing chamber  212  F/R and  214  F/R is formed to have a height (measured between the bottom of the chamber and the clamp regions) of between about 3.25 inches and about 5.0 inches, with a nominal height of about 3.6 inches. In this embodiment, each fluid balancing chamber  212  F/R and  214  F/R is formed to have a width (measured between the sides of the chamber and determined by the width of pinch clamp  318 ) of between about 1.0 inch and about 2.75 inches, with a nominal width of about 1.2 inches. These dimensions help optimize volumetric fluid balance functions. 
     Further, in another embodiment, each clamp region  220 / 222  and  224 / 226  is formed to have a channel width of between about 0.10 inch and 0.40 inch. Bead suppression measures are employed in the clamp regions  220 / 222  and  224 / 226  to keep the material adjacent the welded seams, which form the clamp regions, from exceeding more than twice the thickness of the material walls. These steps assure reliable functioning of the overlaying clamp regions in association with the external clamps. 
     Also, in another embodiment, the ultrafiltration fluid path  136  is formed to have a channel width of greater than about 0.140 inch but less than about 0.60 inch. This optimizes the flow of waste fluid. 
     In a preferred embodiment, the regions where pressure is sensed in the fluid circuit is formed to have in an interior diameter that is greater than 0.40 inch, to optimize pressure sensing without an air-blood interface using external sensors. 
     Also in a preferred embodiment, the passage  438  in the replacement fluid management module  426  that leads to the bypass tubing  432  (see  FIG. 11 ) is formed with a channel width of between about 0.050 inch and 0.60 inch. The width is matched with pinch portion of regulator  242 . This establishes the proper balanced flow conditions to prevent chamber overfilling. The foregoing dimensions and ranges are set forth solely for the purpose of illustrating typical device dimensions. The actual dimensions of a device constructed according to the principles of the present invention may obviously vary outside of the listed ranges without departing from those basic principles. 
     C. Representative Hemofiltration Modalities 
     During hemofiltration, blood is drawn from the person at a prescribed flow rate (BFR). Waste fluid is removed from the blood flow through filter  34  and volumetrically balanced with replacement fluid, which is returned in the venous blood flow at a prescribed rate (RFR). A prescribed net ultrafiltration volume of waste fluid is also removed at a prescribed flow rate (UFR) with fluid balancing, to control net weight loss. Operation of the machine  16  in a hemofiltration mode terminates when either (i) the replacement fluid sensor indicates the absence of replacement fluid flow by sensing the presence of air (i.e., no more replacement fluid) and the net ultrafiltration goal has been achieved; or (ii) the time prescribed for the session has elapsed. 
     Hemofiltration can also be performed without an ultrafiltration function (which can be called balanced hemofiltration). This mode can be used for persons that experience no weight gains between treatment sessions. This mode can also be used at the end of a hemofiltration session, when the net ultrafiltration goal was achieved before exhausting the supply of replacement fluid. 
     During another hemofiltration modality (called only net ultrafiltration), only a net ultrafiltration volume of waste is removed from the person. No fluid is replaced. This mode can be used when it is desired only to remove fluid. This mode can also be used at the end of a hemofiltration session, when the net ultrafiltration goal has not been achieved but the supply of replacement fluid has been exhausted. 
     In another hemofiltration modality (called replacement fluid bolus), there are no fluid balancing and ultrafiltration functions. Blood is circulated in an extracorporeal path and a bolus of replacement fluid is added. In the illustrated embodiment, the ultrafiltration pump  144  is run in reverse at a speed equal to the waste and replacement pump  152 . This recirculates waste fluid through the waste compartments  212 R and  214 R, to add replacement fluid from the replacement compartments  212 F and  214 F to the patient. The waste fluid that is recirculated limits waste fluid removal through the hemofilter  34 , yielding replacement fluid addition without additional waste fluid removal. The net volume of added replacement fluid conveyed to the patient equals the volume of waste fluid recirculated. This mode can be used to return fluid to a person in a bolus volume, e.g., during a hypotensive episode or during rinse back at the end of a given hemofiltration session. 
     1. Controlling the Blood Flow Rate 
     High blood flow rates (e.g., in some embodiments at least 200 ml/min or more, in other embodiments at least 300 ml/min or more, in other embodiments at least 400 ml/min or more, in other embodiments at least 500 ml/min or more, and in other embodiments at least 600 ml/min or more) are conducive to rapid, efficient frequent hemofiltration. The high blood flow rates not only reduce the processing time, but also significantly increases the transport rate of uremic toxins across the hemofiltration membrane. In this way, the system  10  removes high concentrations of uremic toxins, without requiring the removal of high fluid volumes, with the attendant loss of electrolytes. 
     The blood flow rate (BFR) can be prescribed by an attending physician and input by the operator at the beginning of a treatment session. Alternatively, the machine  16  can automatically control to achieve an optimal BFR and minimize procedure time, based upon a desired filtration fraction value (FF), ultrafiltration flow rate (UFR), and replacement fluid flow rate (RFR), as follows: BFR=(RFR+UFR)/FF. 
     where: 
     FF is the desired percentage of fluid to be removed from the blood stream through the hemofilter  34 . 
     A desired FF (typically 20% to 35%) for post dilution HF can be either preset or prescribed by the attending physician. A desired FF takes into account the desired therapeutic objectives of toxin removal, as well as the performance characteristics of the hemofilter  34 . A nominal FF can be determined based upon empirical and observed information drawn from a population of individuals undergoing hemofiltration. A maximum value of approximately 30% is believed to be appropriate for most individuals and hemofilters  34 , to achieve a desired therapeutic result without clogging of the hemofilter  34 . 
     In the illustrated embodiment, an arterial line sensor is incorporated into the extracorporeal circuit. The sensor  98  is an ultrasonic air leak detector, which also can provide the added capacity to sense flow rate. 
     In the illustrated embodiment, the machine  16  senses waste fluid pressure to control the blood flow rate to optimize the removal of fluid across the hemofilter  34 . As arterial blood flows through the hemofilter  34  (controlled by the blood pump  92 ), a certain volume of waste fluid will cross the membrane into the waste line  118 . The volume of waste fluid entering the waste line  118  depends upon the magnitude of the transmembrane pressure, or the pressure differential between the blood on the inside of filter fibers and the waste fluid on the outside of the fibers. As waste fluid is pumped away, the transmembrane pressure increases pushing waste fluid across membrane to replace removed waste. The transmembrane pressure is sensed by the sensor  132 . The waste fluid pressure is adjusted by controlling the waste fluid removal rate through the fluid balancing compartments (i.e., through control of the waste and replacement pump  152 ) and through the UF pump  144 . 
     The machine  16  monitors the waste fluid pressure at sensor  132 . By keeping the pressure sensed by the sensor  132  slightly above zero (approximately 30 to 100 mmHg), the machine  16  achieves the maximum removal of fluid from the blood at the operative blood flow rate. Waste pressure values significantly higher than zero will limit removal of fluid from the blood and keep a higher percentage of waste fluid in the blood (i.e., result in a lower filtration fraction). However, this may be desirable for persons who tend to clot easier. The machine  16  can also include a waste pressure alarm to indicate when the sensed waste fluid pressure does not meet set criteria. 
     By sensing waste fluid pressure by sensor  132 , the machine  16  also indirectly monitors arterial blood pressure and flow. At a constant blood pump speed, changes in arterial blood flow caused, e.g., by access clotting or increased arterial blood pressure, makes less waste fluid available in the waste line  118 . At a given speed for pump  152 , change in arterial blood flow will lower the sensed waste pressure at sensor  132  to a negative value, as fluid is now drawn across the membrane. The machine  16  adjusts for the change in arterial blood flow by correcting the waste fluid removal rate through the pump  152  and  144 , to bring the waste pressure back to slightly above zero, or to another set value. 
     In this arrangement, a pressure sensor in the arterial blood line is not required. If the arterial pressure increases at a fixed blood pump speed, the blood flow must drop, which will result in a sensed related drop in the waste fluid pressure by the sensor  132 . Adjusting the pump  152  and  144  to achieve a pressure slightly above zero corrects the reduced arterial blood flow. In this arrangement, since the waste fluid pressure is maintained at a slightly positive value, it is not possible to develop a reverse transmembrane pressure, which conveys waste fluid back to the person&#39;s blood. The maximum transmembrane pressure is the maximum venous pressure, since waste fluid pressure is held slightly positive. 
     In an alternative arrangement, arterial blood pressure can be measured by a sensor located upstream of the blood pump. The rate of the blood pump is set to maintain sensed arterial blood pressure at a predetermined control point. This controls the blood pump speed to a maximum rate. The control point can be determined, e.g., on a day-to-day basis, to take into account the blood access function of the person undergoing treatment. Use of an arterial pressure control point minimizes the treatment time, or, alternatively, if treatment time is fixed, the removal of waste fluid can maximized. 
     In this arrangement, safety alarms can be included should the sensed arterial pressure become more negative than the control point, along with a function to shut down the blood pump should an alarm occur. 
     In an alternative arrangement, a flow rate sensor can be placed in the arterial blood line to sense an actual blood flow rate. The sensed blood flow rate is compared to a commanded blood flow rate, and the blood pump is controlled to a commanded difference between the two flow rates. In this way, a maximum blood flow rate can be achieved. Alternatively, as arterial blood pressure can be expressed as a function of flow rate, arterial blood pressure can be derived from the sensed flow rate. The rate of the blood pump is set to maintain the derived arterial blood pressure at a predetermined control point. This controls the blood pump speed to a maximum rate. As stated above, use of an arterial pressure control point minimizes the treatment time, or, alternatively, if treatment time is fixed, the removal of waste fluid can be maximized by controlling waste fluid pressure, as described above. 
     2. Controlling the Replacement Fluid Flow Rate 
     RFR can be prescribed by an attending physician and inputted by the operator at the beginning of a treatment session. 
     Alternatively, the machine  16  can automatically control RFR to minimize procedure time based upon the desired filtration fraction value (FF), BFR, and UFR, as follows: RFR=(BFR*FF)−UFR. 
     In the illustrated embodiment, waste is conveyed to the waste side compartments  212 R and  214 R, and replacement fluid is conveyed to the replacement side compartments  212 F and  214 F, by operation of the dual header waste and replacement fluid pump  152 . Alternatively, separate waste and replacement fluid pumps can be provided. 
     The speed of the waste and replacement pump  152  is controlled to achieve the desired RFR. The machine  16  cycles the inlet and outlet valve assemblies  244 ,  246 ,  248 , and  250 , as described. The machine  16  cycles between the valve states according to the speed of the waste and fluid pump  152  to avoid overfilling the compartments  212 ,  214  receiving fluid. Various synchronization techniques can be used. 
     In a preferred embodiment, the waste fluid is pumped at RFR, and the replacement fluid is pumped at a higher rate, but is subject to pressure relief through the pressure relief path  240  upon filling the corresponding replacement side compartment  212 F and  214 F. 
     In another arrangement, the timing of the transition between valve cycles is determined by active sensing of pressure within the compartments  212 ,  214  receiving liquid. As the two matching walls of chambers  212 R/ 212 F and  214 R/ 214 F reach the end of their travels, pressure will increase, signaling an end of cycle to switch valve states. 
     In yet another arrangement, the location of the two matching walls of chambers  212 R/ 212 F and  214 R/ 214 F as they reach the end of their travels are actively sensed by end of cycle sensors on the machine  16 . The sensors can comprise, e.g., optical sensors, capacitance sensors, magnetic Hall effect sensors, or by radio frequency (e.g., microwave) sensors. The termination of movement of the walls indicates the complete filling of a compartment and the concomitant emptying of the other compartment, marking the end of a cycle. The sensors trigger an end of cycle signal to switch valve states. 
     The machine  16  counts the valve cycles. Since a known volume of replacement fluid is expelled from a replacement side compartment during each valve cycle, the machine  16  can derive the total replacement volume from the number of valve cycles. The replacement fluid volume is also known by the number of replacement fluid bags of known volume that are emptied during a given session. 
     Hemofiltration can be conducted without fluid replacement, i.e., only net ultrafiltration, by setting RFR to zero. 
     3. Controlling the Ultrafiltration Flow Rate 
     UFR can be prescribed by an attending physician and inputted by the operator at the beginning of a treatment session. 
     The speed of the ultrafiltration pump is monitored and varied to maintain UFR. 
     Frequent hemofiltration can be conducted without an ultrafiltration function, i.e., balanced hemofiltration, by setting UFR to zero. 
     4. Active Filtration Rate Control 
     In an alternative embodiment, the machine  16  also actively controls the filtration rate along with the blood flow rate, to achieve a desired magnitude of uremic toxin removal through the hemofilter  34 . 
     In this embodiment, the machine  16  includes a flow restrictor which is positioned to engage a region of the venous blood return path  84  in the circuit  18 . The restrictor comprises, e.g., a stepper-driven pressure clamp, which variably pinches a region of the venous blood return path upon command to alter the outlet flow rate of blood. This, in turn, increases or decreases the transmembrane pressure across the filter membrane. 
     For a given blood flow rate, waste transport across the filter membrane will increase with increasing transmembrane pressure, and vice versa. However, at some point, an increase in transmembrane pressure, aimed at maximizing waste transport across the filter membrane, will drive cellular blood components against the filter membrane. Contact with cellular blood components can also clog the filter membrane pores, which decreases waste transport through the membrane. 
     Filtration rate control can also rely upon an upstream sensor mounted on the machine  16 . The sensor is positioned for association with a region of the arterial blood supply path between the blood pump  92  and the inlet of the hemofilter  34 . The sensor senses the hematocrit of the blood prior to its passage through the filter membrane (which will be called the pre-treatment hematocrit). In the arrangement, a downstream sensor is also mounted on the machine  16 . The sensor is positioned for association with a region of the venous blood return path downstream of the outlet of the hemofilter  34 . The sensor senses the hematocrit of the blood after its passage through the hemofilter  34  (which will be called the post-treatment hematocrit). 
     The difference between pre-treatment and post-treatment hematocrit is a function of the degree of waste fluid removal by the hemofilter  34 . That is, for a given blood flow rate, the more waste fluid that is removed by the hemofilter  34 , the greater the difference will be between the pre-treatment and post-treatment hematocrits, and vice versa. The machine  16  can therefore derive an actual blood fluid reduction ratio based upon the difference detected by sensors between the pre-treatment and post-treatment hematocrits. The machine  16  periodically compares the derived fluid reduction value, based upon hematocrit sensing by the sensors, with the desired FF. The machine  16  issues a command to the flow restrictor to bring the difference to zero. 
     Waste fluid removal optimization can also be achieved by maintaining a maximum specified transmembrane pressure in the hemofilter by manipulating blood flow rate, and/or venous blood pressure, and/or waste fluid pressure. This optimization technique can be undertaken once at the outset of a given procedure, or at several intervals during the course of a procedure. In this arrangement, arterial blood pressure sensing (or derivation thereof based upon flow rate sensing) is implemented to achieve a maximum blood flow rate. A fixed or variable flow restrictor is placed in the venous blood return path to maintain a set maximum transmembrane pressure (e.g., 600 mmHg) while the maximum arterial blood flow rate is maintained. Pressure is sensed in the venous blood return path to assure that venous pressure does not exceed a set maximum amount (e.g., 250 mmHg), which is set for safety reasons. Waste fluid pressure is kept slightly above 50 mmHg. Together, control of transmembrane pressure at the maximum blood flow rate and control of waste fluid pressure at a maximum blood flow rate, maximize the waste fluid removal rate. 
     5. Set Up Pressure Testing/Priming 
     Upon mounting the disposable fluid circuit  18  on the machine  16 , the pumps can be operated in forward and reverse modes and the valves operated accordingly to establish predetermined pressure conditions within the circuit. The sensors monitor build up of pressure within the circuit, as well as decrease in pressure over time. In this way, the machine can verify the function and integrity of pumps, the pressure sensors, the valves, and the flow paths overall. 
     The machine  16  can also verify the accuracy of the ultrafiltration pump using the fluid balancing containers. 
     Priming can be accomplished at the outset of each hemofiltration session to flush air and any residual fluid from the disposable fluid circuit. Fluid paths from the blood lines to the waste bag are flushed with replacement fluid. Replacement fluid is also circulated through the fluid balancing containers into the waste bag and the venous return path. The higher flow rate in the replacement fluid path and timing of the fluid balancing valve elements assure that the replacement fluid compartments completely fill and the waste fluid compartments completely empty during each cycle for priming. 
     6. Rinse Back 
     As previously described, waste fluid pressure is controlled and monitored to assure its value is always positive. Likewise, pressure between the blood pump and the hemofilter must also be positive, so that air does not enter this region of the circuit. Forward operation of the blood pump to convey arterial blood into the hemofilter establishes this positive pressure condition. 
     In this arrangement, no air sensing is required in the blood line, and a pressure sensor between the blood pump and the hemofilter is required. 
     7. Using the GUI 
     When configured to guide an operator to perform hemofiltration, or another treatment modality, the GUI  324  (see  FIG. 19 ) can, e.g., include an array of icon-based touch button controls  326 ,  328 ,  330 , and  332 . For example, the controls can include an icon-based treatment start/select touch button  326 , an icon-based treatment stop touch button  328 , an icon-based audio alarm mute touch button  330 , and an icon-based add fluid touch button  332 . 
     An array of three numeric entry and display fields can appear between the icon-based touch buttons. The fields can comprise information display bars  334 ,  336 , and  338 , each with associated touch keys  340  to incrementally change the displayed information. 
     The associated touch keys  340  can be provided to point up (to increase the displayed value) or down (to decrease the displayed value), to intuitively indicate their function. The display bars  334 ,  336 , and  338  and touch keys  340  can be shaded in different colors. 
     An array of status indicator bars can appear across the top of the screen. The left bar  342 , when lighted, displays a safe color (e.g., green) to indicate a safe operation condition. The middle bar  344 , when lighted, displays a cautionary color (e.g., yellow) to indicate a caution or warning condition and may, if desired, display a numeric or letter identifying the condition. The right bar  346 , when lighted, displays an alarm color (e.g., red) to indicate a safety alarm condition and may, if desired, display a numeric or letter identifying the condition. 
     The display can also a processing status touch button  348 . For example, the button  348 , when touched, can change for a period of time (e.g., 5 seconds) the values displayed in the information display bars  334 ,  336 , and  338  , to show the corresponding current real time values, e.g., for a hemofiltration modality, the replacement fluid volumes exchanged (in the top display bar  334 ), the ultrafiltrate volume (in the middle display bar  336 ), and the blood volume processed (in the bottom display bar  338 ). The status button  348 , when touched, can also show the elapsed procedure time in the left status indicator bar  342 . 
     The display can also include a cartridge status icon  350 . The icon  350 , when lighted, can indicate that the cartridge  18  can be installed or removed from the machine  16 . 
     In a preferred arrangement, the GUI  324  can employ a touch button input verification function, which monitors the information provided by the touch button controls. The input verification function inputs the information provided by a given touch button control both to the system control processor and to the system safety processor. The two processors communicate using an appropriate handshake protocol when the information received by the system control processor matches the information received by the system safety processor. The handshake allows information input to proceed for execution. The lack of a handshake between the system control processor and system safety processor indicates a possible information input error. In this instance, the GUI generates an error signal which requires a re-entry of the information input and a subsequent handshake before information input can proceed for execution. 
     As  FIG. 19  shows, the interface can also include an infrared port  360  to support the telemetry function, as already described. 
     The GUI  324 , though straightforward and simplified, enables the operator to set these various processing parameters for a given hemofiltration session in different ways. 
     For example, in one input mode for hemofiltration, the GUI  324  can prompt the operator by back-lighting the replacement fluid display bar  334 , the ultrafiltration display bar  336 , and the blood flow rate display bar  338 . The operator follows the lights and enters the desired processing values using the associated touch up/down buttons  340 . The GUI back-lights the start/select touch button  326 , prompting the operator to begin the treatment. In this mode, the machine  16  controls the pumps to achieve the desired replacement fluid, ultrafiltration, and blood flow rates set by the operator. The machine terminates the procedure when all the replacement fluid is used and the net ultrafiltration goal is achieved. 
     In another input mode for hemofiltration, the operator can specify individual processing objectives, and the machine  16  will automatically set and maintain appropriate pump values to achieve these objectives. This mode can be activated, e.g., by pressing the start/select touch button  326  while powering on the machine  16 . The GUI  324  changes the function of the display bars  334  and  336 , so that the operator can select and change processing parameters. In the illustrated embodiment, the processing parameters are assigned identification numbers, which can be scrolled through and selected for display in the top bar  334  using the touch up/down keys  340 . The current value for the selected parameter is displayed in the middle display bar  336 , which the operator can change using the touch up/down keys  340 . 
     In this way, the operator can, e.g., specify a desired filtration factor value (FF) along with a desired ultrafiltration flow rate (UFR) and replacement fluid flow rate (RFR). The machine will automatically control the blood pump rate (BFR), based upon the relationship BFR=(RFR+UFR)/FF, as already described. 
     Alternatively, the operator can specify a desired filtration factor value (FF) along with a desired ultrafiltration flow rate (UFR) and blood flow rate (BFR). The machine will automatically control the replacement fluid pump rate (RFR), based upon the relationship RFR=(BFR*FF)−UFR, as already described. 
     Alternatively, the operator can specify only an ultrafiltration volume. In this arrangement, the machine  16  senses waste fluid pressure to automatically control the blood flow rate to optimize the removal of fluid across the hemofilter  34 , as previously described. Alternatively, the machine can automatically control the blood flow rate to optimize removal of fluid based a set control arterial blood pressure, as also already described. Still alternatively, the machine can automatically optimize the ultrafiltration flow rate and blood flow rate to achieve the desired net ultrafiltration volume. 
     In another mode, the operator can specify both replacement fluid volume and ultrafiltration volume to remove. In this arrangement, the machine performs a countdown of the sum of the two fluid volumes to minimize the duration of the treatment. 
     While particular devices and methods have been described, once this description is known, it will be apparent to those of ordinary skill in the art that other embodiments and alternative steps are also possible without departing from the spirit and scope of the invention. Moreover, it will be apparent that certain features of each embodiment can be used in combination with devices illustrated in other embodiments. Accordingly, the above description should be construed as illustrative, and not in a limiting sense, the scope of the invention being defined by the following claims.