Graphical user interface for automated dialysis system

Abstract

A method, system and apparatus for performing peritoneal dialysis are provided. To this end, in part, a dialysis system is provided. The dialysis system includes a display device and a web browser and web server embedded in the dialysis system. The browser and the server operate with the display device to display a number of dialysis therapy set-up procedure screens that require operator input, and to display a number of dialysis treatment screens that graphically illustrate the progress of at least one step in the dialysis therapy in at least substantially real time.

Claims

The invention claimed is:

1. A dialysis system comprising:

a display device; and

a web browser and web server embedded in the dialysis system, the browser and the server operating with the display device to:

display a plurality of dialysis therapy set-up procedure screens that require an operator input, and

display a plurality of dialysis treatment screens that graphically illustrate the progress of at least one step in the dialysis therapy in at least substantially real time.

2. The dialysis system of claim 1, which includes at least one input device that operates with the dialysis therapy set-up procedure screens.

3. The dialysis system of claim 2, wherein the input device is a simulated area of a touch screen.

4. The dialysis system of claim 1, wherein the input device is selected from the group consisting of: a pushbutton, a rotatable knob and a combination thereof.

5. The dialysis system of claim 1, wherein the set-up procedure screens display at least one image resembling equipment used in setting up the dialysis therapy.

6. The dialysis system of claim 1, wherein the set-up procedure screens display at least one animation depicting an action to be taken by the operator.

7. The dialysis system of claim 1, wherein the set-up procedure screens display at least one image depicting a hygienic precaution to be taken by the operator.

8. The dialysis system of claim 1, wherein at least one of the set-up procedure screens is displayed until the operator selects a prompt provided by the screen.

9. The dialysis system of claim 1, wherein the set-up procedure screens are colored for viewing in the presence of light.

10. The dialysis system of claim 1, wherein the dialysis treatment screens are colored for viewing in reduced light.

11. The dialysis system of claim 1, wherein at least one of the dialysis treatment screens includes therapy status information in a form selected from the group consisting of: numerical data, graphical data and a combination thereof.

12. The dialysis system of claim 1, wherein the display device and the embedded web browser further operate to display a plurality of dialysis therapy parameter adjustment screens.

13. The dialysis system of claim 12, wherein the dialysis therapy parameter adjustment screens include categories of parameters, wherein the operator selects a category and then a parameter from the selected category.

Description

BACKGROUND OF THE INVENTION

The present invention generally relates to dialysis systems. More specifically, the present invention relates to automated peritoneal dialysis systems. The present invention also relates to methods of performing automated peritoneal dialysis and devices for performing same.

Due to disease, insult or other causes, a person's renal system can fail. In renal failure of any cause, there are several physiological derangements. The balance of water, minerals and the excretion of daily metabolic load is no longer possible in renal failure. During renal failure, toxic end products of nitrogen metabolism (urea, creatinine, uric acid, and others) can accumulate in blood and tissues.

Kidney failure and reduced kidney function have been treated with dialysis. Dialysis removes waste, toxins and excess water from the body that would otherwise have been removed by normal functioning kidneys. Dialysis treatment for replacement of kidney functions is critical to many people because the treatment is life saving. One who has failed kidneys could not continue to live without replacing at least the filtration functions of the kidneys.

Hemodialysis and peritoneal dialysis are two types of dialysis therapies commonly used to treat loss of kidney function. Hemodialysis treatment utilizes the patient's blood to remove waste, toxins and excess water from the patient. The patient is connected to a hemodialysis machine and the patient's blood is pumped through the machine. Catheters are inserted into the patient's veins and arteries to connect the blood flow to and from the hemodialysis machine. As blood passes through a dialyzer in the hemodialysis machine, the dialyzer removes the waste, toxins and excess water from the patient's blood and returns the blood back to the patient. A large amount of dialysate, for example about 120 liters, is used to dialyze the blood during a single hemodialysis therapy. The spent dialysate is then discarded. Hemodialysis treatment lasts several hours and is generally performed in a treatment center about three or four times per week.

Peritoneal dialysis utilizes a dialysis solution or "dialysate", which is infused into a patient's peritoneal cavity through a catheter implanted in the cavity. The dialysate contacts the patient's peritoneal membrane in the peritoneal cavity. Waste, toxins and excess water pass from the patient's bloodstream through the peritoneal membrane and into the dialysate. The transfer of waste, toxins, and water from the bloodstream into the dialysate occurs due to diffusion and osmosis, i.e., an osmotic gradient occurs across the membrane. The spent dialysate drains from the patient's peritoneal cavity and removes the 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 and continuous flow peritoneal dialysis. CAPD is a manual dialysis treatment, in which the patient connects an implanted catheter to a drain and allows a spent dialysate fluid to drain from the peritoneal cavity. The patient then connects the catheter to a bag of fresh dialysate and manually infuses fresh dialysate through the catheter and into the patient's peritoneal cavity. The patient disconnects the catheter from the fresh dialysate bag and allows the dialysate to dwell within the cavity to transfer waste, toxins and excess water from the patient's bloodstream to the dialysate solution. After a dwell period, the patient repeats the manual dialysis procedure.

In CAPD the patient performs several drain, fill, and dwell cycles during the day, for example, about four times per day. Each treatment cycle typically takes about an hour. Manual peritoneal dialysis performed by the patient requires a significant amount of time and effort from the patient. This inconvenient procedure leaves ample room for improvement and therapy enhancements to improve patient quality of life.

Automated peritoneal dialysis ("APD") is similar to CAPD in that the dialysis treatment includes a drain, fill, and dwell cycle. APD machines, however, automatically perform three to four cycles of peritoneal dialysis treatment, typically overnight while the patient sleeps. The APD machines fluidly connect to an implanted catheter. The APD machines also fluidly connect to a source or bag of fresh dialysate and to a fluid drain.

The APD machines pump fresh dialysate from the dialysate source, through the catheter, into the patient's peritoneal cavity and allow the dialysate to dwell within the cavity so that the transfer of waste, toxins and excess water from the patient's bloodstream to the dialysate solution can take place. The APD machines then pump spent dialysate from the peritoneal cavity, though the catheter, to the drain. APD machines are typically computer controlled so that the dialysis treatment occurs automatically when the patient is connected to the dialysis machine, for example, when the patient sleeps. That is, the APD systems automatically and sequentially pump fluid into the peritoneal cavity, allow for a dwell, pump fluid out of the peritoneal cavity and repeat the procedure.

As with the manual process, several drain, fill, and dwell cycles will occur during APD. A "last fill" is typically used at the end of APD, which remains in the peritoneal cavity of the patient when the patient disconnects from the dialysis machine for the day. APD frees the patient from having to manually performing the drain, dwell, and fill steps.

However, continuing needs exist to provide improved APD systems. For example, needs exist to provide simplified APD systems that are easier for patients to use and operate. Further, needs exist to provide lower cost APD systems and APD systems which are less costly to operate. Particularly, needs exist to clinically, economically and ergonomically improve known APD systems.

APD systems need to be improved for home use. One common problem with current home systems is that they are susceptible to electrical shock due to "leakage current". Current that flows from or between conductors insulated from one another and from earth is called "leakage current". If any conductor is raised to a potential above earth potential, then some current is bound to flow from that conductor to earth. This is true even of conductors that are well insulated from earth, since there is no such thing as perfect insulation or infinite resistance. The amount of current that flows depends on: (i) the potential, (ii) the capacitate reactance between the conductor and earth and (iii) the resistance between the conductor and earth.

For medical equipment, several different leakage currents are defined according to the paths that the leakage currents take. An "earth leakage current" is the current which normally flows in the earth conductor of a protectively earthed piece of equipment. In medical equipment, impedance to earth from an enclosure is normally much lower through a protective earth conductor than it is through the patient. However, if the protective earth conductor becomes open circuited, the patient could be at risk of electrical shock.

"Patient leakage current" is the leakage current that flows through a patient connected to an applied part or parts. It can either flow from the applied parts via the patient to earth or from an external source of high potential via the patient and the applied parts to earth. Other types of leakage currents include "enclosure leakage current", and "patient auxiliary current".

Leakage currents are normally small, however, the amount of current required to produce adverse physiological effects in patients is also small. Accordingly, leakage currents must be limited as much as possible by the design of the equipment and be within safety limits.

SUMMARY OF THE INVENTION

Generally, the present invention provides improved dialysis systems and improved methods of performing dialysis. More particularly, the present invention provides systems and methods for performing automated peritoneal dialysis ("APD"). The systems and methods of the present invention automatically provide dialysis therapy by providing dialysis fluid to the patient and draining spent dialysis fluid from the patient.

Also, the systems and methods of the present invention can perform various dialysis therapies. One example of a dialysis therapy which can be performed according to the present invention includes an automatic dialysis fluid exchange of a patient fill, dwell and a patient drain. The dialysis system of the present invention can automatically perform dialysis therapy on a patient, for example, during nighttime while the patient sleeps.

To this end, in an embodiment a dialysis system is provided. The system includes a fluid supply line. A disposable unit is in fluid communication with the fluid supply line. The disposable unit has at least two flexible membranes that bond together at selected locations and to a rigid plastic piece or manifold. The membranes can be single or double layer. One preferred membrane material is described herein. The membranes seal to one another so as to define a fluid pump receptacle and a fluid heating pathway. The membranes and plastic manifold define a number of flexible valve chambers. The disposable unit also fluidly communicates with a patient line and a drain line.

The manifold and other areas of the disposable unit include reduced or tapered edges that provide an area to seal the membranes. The reduced thickness or tapered area requires less heat than the full thickness, which reduces the heat sinking disparity between the thickness of the manifold of the disposable unit and the thinner flexible membranes. The frame of the manifold is bowed or curved to provide rigidity. The frame is also asymmetrical and designed to be placed into the hardware unit in only one direction.

The hardware unit can be manually transported to a patient's home and opened so that the patient can place a disposable unit therein and closed so that the dialysis unit and the disposable unit cooperatively form a pump chamber that enables dialysis fluid to be pumped to and from the patient. The hardware unit has an enclosure that defines a pump shell, a valve actuator and a heater. The disposable unit is placed in and removed from the enclosure. The fluid pump receptacle of the disposable unit and the shell of the hardware unit form a pump chamber. The pump chamber operates with a pump actuator, which is also located inside the transportable hardware unit.

When packaged, a plurality of tubes extend from the disposable unit. The ends of the tubes have connectors that attach to a single body. The body defines or provides a plurality of tip protectors that hold the tubes in an order according to steps of the therapy. The body is configured to slide into the hardware unit of the system from one direction, so that a patient can readily pull the tubes and connectors from the tip protector organizer.

The tip protector used to house the patient fluid connector includes a hydrophobic filter that allows air but not fluid to escape. This vented tip protector enables the system to be primed without having to perform elevation balancing or controlled fluid metering. The system performs a prime by flowing fluid through the system and into the patient fluid line until the dialysate backs up against the filter, causing a fluid pressure increase, which is sensed by the system. The system then stops the pump.

The hardware unit also provides a controller. The controller includes a plurality of processors, a memory device for each processor and input/output capability. One of the processors coordinates operation of the pump actuator, the valve actuator and the heater with the various stages of dialysate flow, such as the fill, dwell and drain stages. The processor also controls or obtains feedback from a plurality of different types of sensors. The sensors include, among others, a capacitance fluid volume sensor, a dialysis fluid temperature sensor, a pressure sensor, a vacuum sensor, an air detection sensor and a mechanical positioning sensor.

In an embodiment, the system uses both preset motion control and adaptive pressure control to control the pressure of fluid within the pump receptacle. The system uses a preset pump motor acceleration to overcome system compliance (i.e., membrane and tubing expansion), which would not otherwise be readily overcome by known proportional, differential or integral control. After the system overcomes compliance, the system converts to an adaptive control using adaptive techniques for controlling pressure by precisely controlling the velocity of a pump motor shaft. The adaptive parameters are modified over time to fine tune the system. This method is especially important for the patient fill and drain cycles, wherein the patient can feel pressure fluctuations. The method also readily compensates for pressure variations due to bag height, bag fullness, etc.

The capacitance fluid volume sensor indicates a volume of fluid in the pump chamber, wherein the sensor generates a voltage signal that is indicative of the volume of fluid in the receptacle. The controller receives the voltage signal and converts the signal into an amount of fluid or an amount of air within the flexible fluid receptacle of the pump chamber.

The pump actuator can be mechanically or pneumatically operated. When mechanically driven, a pump motor drives a vacuum source, such as a piston-cylinder, which pulls a vacuum on the membranes of the fluid receptacle of the disposable unit. Here, a mechanical positioning sensor, such as an encoder, senses the angle of a pump motor shaft relative to a home position and sends a signal to the controller, wherein the controller can adjust the pump motor accordingly. The encoder also provides safety feedback to the controller, whereby the controller, once therapy starts, prevents the camshaft from rotating, to a position where the valves free fill the patient. When the pump actuator is pneumatically operated, the system in an embodiment uses a vacuum pump to pull apart the membranes of the fluid receptacle. Here, the system uses a vacuum sensor to sense the state of the vacuum pump and a mechanical sensing device, such as a linear encoder, to sense the state of a pump piston.

Thus, in an embodiment, the system maintains a negative pressure on one of the membranes of the fluid receptacle of the disposable unit to pull same away from the other membrane and draw dialysis fluid into the fluid receptacle. The negative pressure on the active membrane is then released, which pushes the membrane towards the other membrane and dispels the dialysis fluid from the pump receptacle. In another embodiment, a mechanical pump piston can be pneumatically attached to one of the membranes, wherein the system mechanically pulls the membrane away from the other membrane. In an embodiment, the membrane is coupled to the pump piston through negative pressure. The pump also includes a diaphragm that is pulled to a bottom side of the piston head, wherein the membrane is pulled to a top side of same. In a further embodiment, the system mechanically pushes one of the membranes while applying the negative pressure to same.

The system also performs other necessary tasks automatically. For example, the system automatically heats the dialysate to a desired temperature while pumping dialysate to the patient. The heater heats the fluid heating pathway defined by the flexible membranes of the disposable unit. In an embodiment, the heater includes an electrical heating plate. Alternatively, or in addition to the heating plate, the heater includes an infrared heating source. In an embodiment, the fluid heating pathway and the heater define an in-line heater that heats dialysate as it travels from the supply bag to the patient.

The system employs a method of heat control that uses a knowledge-based algorithm and a fuzzy logic based algorithm. The former uses laws of physics, empirical data and sensed inputted signals. The latter inputs a difference between desired and actual temperatures and uses fuzzy logic membership functions and fuzzy logic rules. Each algorithm operates at a different update frequency. Each algorithm outputs a duty cycle, wherein the system weights the fuzzy logic based duty cycle relative to the knowledge based duty cycle and produces an overall heater control duty cycle. This method enables accurate dialysate temperature control.

The system automatically purges air from the dialysate, for example, through the pump chamber. The system also senses a total volume of fluid pumped to the patient, records and logs same. Furthermore, the system knows the instantaneous flow rate and fluid pressure of fluid entering or leaving the patient's peritoneal cavity.

The disposable unit includes a valve manifold. The manifold defines a plurality of valve chambers. The hardware unit includes a valve actuator that selectively and sequentially presses against one or more of the valve chambers. In an embodiment, a mechanically operated valve actuator includes a single camshaft and a plurality of cams. The cams press against one of the membranes of the disposable unit to engage the other membrane and block or disallow fluid flow. As stated above, the system uses a sensing device, such as a rotary encoder, to sense the angle of the camshaft relative to a home position, so that the controller can rotate the camshaft to open or close one or more valves as desired. The single camshaft toggles back and forth between: supply and pump chamber fill positions; patient drain and system drain positions; and between pump chamber fill and patient fill positions. These positions are actuated by a unique rotational position on an overall cam profile (i.e., the superposition of each of the individual cams as seen from the end of the camshaft).

The disposable unit of the present invention is provided in a variety of different forms. In an embodiment, the portion of the disposable unit forming the heating path is formed by same membranes that seal to the rigid member or manifold that forms the valve chambers. The same membranes also form the pump receptacle. In another embodiment, the disposable unit includes a first set of membranes that form the pump receptacle and the valve manifold via the rigid member. Here, the disposable unit includes a second set of membranes, distinct from the first membranes, which form the fluid heating path. In an embodiment, medical grade tubing connects the first set of membranes to the second set. In particular, the tubing enables the fluid heating path to fluidly connect to the valve manifold.

The disposable unit in another embodiment includes a first flexible membrane and a second flexible membrane that house the pump receptacle, the fluid heating path and the rigid valve manifold. The disposable unit also includes a rigid frame that attaches to at least one of the first and second flexible membranes. The rigid frame enables a patient or operator to place the frame and the disposable unit into the enclosure of the hardware unit of the automated dialysis system. The rigid frame is sized to securely fit into a dedicated place in the enclosure. The rigid frame further holds the disposable unit stable while patient or operator connects tubes to same. For example, the valve manifold provides ports or other types of connectors for connecting to a supply line, a drain line and a patient line. In an embodiment, the rigid frame extends around or circumvents the membranes including the pump receptacle, fluid heating path and valve manifold. In an embodiment, the rigid frame is plastic. In an embodiment, the rigid frame is bowed along at least two sides to increase the rigidly of the disposable unit and to keep the disposable unit from deforming during the heat sealing portion of its manufacture.

In an embodiment, the rigid member or manifold of the disposable unit includes interfaces that allow the membranes to be more easily sealed to the manifold. The manifold edges are tapered to reduce the heat needed to form a cohesive bond between the membranes and the plastic valve manifold. The knife-like tapered edges also reduce or eliminate the gap between the top and bottom membranes, which minimizes the opportunity for leaks to occur in the disposable unit. The chamfered edges also reduce the likelihood that the heat sealing process will burn through the membranes.

The hardware unit described above includes a display device that provides dialysis system information. The display device also enables the patient or operator to enter information and commands into the controller. For example, the display device can include an associated touch screen that enables the patient or operator to initiate automatic flow of the dialysate through the disposable unit. The system begins to pneumatically and/or mechanically pump dialysate through the pump chamber, past the in-line heater and into the patient's peritoneal cavity. Thereafter, the system automatically runs the other cycles of dialysis therapy, for example, while the patient sleeps and/or at night. The automated system not only transfers dialysate from a supply container to the patient, the system allows the dialysate to dwell inside the patient for an amount of time and automatically operates to transfer the dialysate from the patient to a drain.

The system provides a graphical user interface ("GUI"). The GUI in an embodiment employs an embedded web browser and an embedded web server. The web browser and server operate on a main microprocessor for the system. The GUI also employs instrument access and control software, which operates on the main system processor and on one or more delegate processors. The instrument access and control software controls lower level devices, such as the heater and the pump. The GUI also provides intermediate software that allows the web browser to communicate with the instrument access and control software.

The GUI displays a number of therapy set-up screens and a number of dialysis treatment screens. The set-up screens generally walk the patient through the set-up portion of the therapy. The system waits for an operator input before proceeding to the next set-up screen. The set-up screens provide information to the patient in the form of real-life images of the equipment and through animations of the actions needed to connect the system to the patient.

The therapy treatment screens display the various cycles of the therapy to the patient in real-time or substantially in-real time. The therapy treatment screens display information such as cycle time in both a graphical and quantitative manner. The therapy treatment screens do not require input from a patient, who may be sleeping while these screens are displayed. When the therapy is complete, the system once again displays a number of disconnection screens which, like the set-up screens, wait for an input from the patient before performing an action.

The treatment screens are colored and lighted for night time viewing, and may be easily seen from a distance of about ten to fifteen feet, however, the screens are lighted so as not to wake a sleeping patient. In an embodiment, the background of the screens is black, while the graphics are ruby red. In contrast, the set-up screens are lighted and colored for daytime viewing.

With the above embodiments, one advantage of the present invention is to provide improved systems and methods for performing dialysis.

Another advantage of the present invention is to provide improved systems and methods for performing peritoneal dialysis.

A further advantage of the present invention is to provide an automated peritoneal dialysis system and method of operating same.

Still another advantage of the present invention is to provide an automated peritoneal dialysis system that provides dialysis therapy advantages.

Still a further advantage of the present invention is to provide an automated peritoneal dialysis system that has economic advantages.

Yet another advantage of the present invention is to provide an automated peritoneal dialysis system that has quality of life advantages.

A still further advantage of the present invention is to provide a disposable unit having bowed sides, which increase rigidity and decrease flexing of disposable unit.

Moreover, an advantage of the present invention is to provide a disposable unit having tapered interfaces that decrease the heat sinking of the semi-rigid manifold and provide a more robust seal.

Various features and advantages of the present invention can become apparent upon reading this disclosure including the appended claims with reference to the accompanying drawings. The advantages may be desired, but not necessarily required to practice the present invention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 schematically illustrates an embodiment of an automated dialysis system of the present invention having a mechanically actuated fluid pump.

FIG. 2 schematically illustrates another embodiment of an automated dialysis system of the present invention having a fluidly actuated fluid pump.

FIGS. 3A and 3B illustrate perspective views of the hardware unit and disposable unit of the present invention.

FIG. 4A is a plan view of one embodiment of the hardware and disposable units of the present invention.

FIG. 4B is a cross-sectional view taken along line 4B—4B in FIG. 4A, which shows one possible configuration of the system components within the hardware unit.

FIGS. 5 and 6 illustrate additional embodiments of the disposable unit of the present invention.

FIG. 7 is a perspective view of one embodiment of a valve manifold that includes a reduced thickness interface for sealing to membranes of a disposable dialysis unit.

FIG. 8 is a perspective view of one embodiment of a multiple tip protector organizer of the present invention.

FIG. 9 is an elevation sectional view of the multiple tip protector organizer illustrated in FIG. 8.

FIG. 10 is an elevation sectional view of one embodiment of a vented tip protector of the present invention showing the tip protector housing a patient fluid line connector.

FIG. 11 is an elevation sectional view of one embodiment of the patient fluid line connector that couples to the vented tip protector of the present invention.

FIG. 12 is an elevation sectional view of one embodiment of the vented tip protector of the present invention.

FIG. 13 is a sectional view of one embodiment of a single layer film structure for the disposable unit membranes of the present invention.

FIG. 14 is a sectional view of one embodiment of a multiple layer film structure for the disposable unit membranes of the present invention.

FIG. 15 is a perspective view of one embodiment of a valve actuator in combination with the fluid manifold of the present invention.

FIGS. 16A and 16B illustrate features of the camshaft and cam arrangement of the present invention.

FIGS. 17A and 17B illustrate an embodiment of a mechanically operated fluid pump and capacitance type fluid volume sensor of the present invention.

FIG. 18 illustrates an alternate embodiment of a fluidly operated fluid pump and capacitance sensor of the present invention.

FIG. 19 is a graphical illustration of one embodiment of the present invention for the control of the pressure inside a fluid pump through precise velocity control of a pump piston.

FIG. 20 is a schematic illustration of one embodiment of an algorithm of the present invention for performing proportional, integral and derivative type adaptive pressure control.

FIG. 21 is a graphical illustration of one embodiment of the present invention for the control of the pressure inside a fluid pump during repeated patient fill and pull from supply bag strokes.

FIG. 22 is a graphical illustration of one embodiment of the present invention for the control of the pressure inside a fluid pump during repeated patient drain and pump to drain strokes.

FIG. 23 is a schematic illustration of one embodiment of an algorithm of the present invention for adapting pressure error correction parameters over time to optimize pressure control efficiency.

FIG. 24 is a table illustrating one set of the correction parameters illustrated in connection with FIG. 23.

FIG. 25 is a schematic representation of one embodiment of a heater control method of the present invention.

FIG. 26 is a flow diagram of a knowledge based algorithm of the method discussed in connection with FIG. 25.

FIG. 27 is a flow diagram of a fuzzy logic based algorithm of the method discussed in connection with FIG. 25.

FIG. 28 is an electrical insulation diagram illustrating one embodiment for providing double electrical insulation in the medical fluid unit of the present invention.

FIG. 29 is a schematic representation of one embodiment of the web based graphical user interface of the present invention.

FIGS. 30A to 30M are screen shots from a display device employing the graphical user interface of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to dialysis systems and methods of performing dialysis. In particular, the present invention relates to a system and method for automatically providing peritoneal dialysis therapy to patients. The present invention provides automatic multiple exchanges of dialysis fluid to and from the patient's peritoneal cavity. The automatic exchanges of dialysate include drain, fill, and dwell periods, which usually occur while the patient sleeps. A typical therapy can include three to five exchanges of dialysis fluid. The present invention, in an embodiment, provides a single pass system, wherein the dialysate passes through the peritoneal cavity only once before being disposed. While the present invention performs peritoneal dialysis, it is also suitable for other types of dialysis and other medical fluid transfer operations.

I. The System Generally

Referring now to the drawings and in particular to FIG. 1, a typical therapy performed by the system 10 of the present invention begins by draining dialysis solution that is already in the patient's peritoneal cavity 12. The system 10 pumps fresh dialysate from one of a plurality of supply bags 14, through an in-line heater 16 to the patient or peritoneal cavity 12. After a dwell period in the peritoneal cavity 12, the spent dialysate in the cavity is pumped out of the patient or cavity 12 to a drain 18 or other disposal means. The system 10 then pumps fresh dialysate from the supply bags 14 to the patient or peritoneal cavity 12 and the procedure is repeated as defined in the therapy protocol. The system 10 in an embodiment pumps a last bag of dialysate (usually, a dialysate having a different formulation than the dialysate in the other supply bags) to the peritoneal cavity 12 for an extended dwell, such as a daytime dwell.

In an embodiment, the system 10 includes a mechanically operated diaphragm pump 20. The mechanically operated diaphragm pump 20 employs a pump motor 22 and a linear pump actuator 24. A vacuum may also be used with the mechanical actuator for the diaphragm pump 20, as described in further detail below. In another embodiment illustrated in FIG. 2, the pump is completely fluidly activated.

In FIG. 1 the system 10 also includes a valve actuator 26, which mechanically actuates valves V1 to V5. A controller 30 controls the valve actuator 26 to open valves V1 to V5 as necessary to achieve the desired direction of dialysate fluid flow. In an embodiment, the valve actuator 26 includes a valve motor 28 and a camshaft (illustrated below), which opens one or more of the valves V1 to V5 to achieve the desired dialysate flow.

The controller 30 includes a plurality of processors and a memory device for each processor. The processors include a main microprocessor and a number of delegate processors. The main microprocessor runs certain higher level tasks such as the graphical user interface ("GUI") described below. The delegate processors perform lower level tasks, such as moving valves, reading sensors, controlling heater duty cycle, etc. An additional processor is provided solely for the purpose of tracking safety parameters, such as heater plate and medical fluid temperature. For purposes of the present invention, except where otherwise specified, the term "processor 34" refers collectively to all of the processors and the term "memory device 32" refers collectively to all of the corresponding memory devices.

The controller 30 also includes an input/output ("I/O") module 36. The memory 32 stores a computer program that contains a step by step sequence for the system 10 and configures certain outputs to occur upon specified inputs. The processor 34 runs the program in memory 32. The I/O module 36 accepts signal lines from various sensors. The I/O module 36 also connects to power lines including input power lines (including if battery powered) and power lines outputted to the various electrical components.

The controller 30, in an embodiment, includes a video controller 38, which may be a video card. The controller 30 also includes a display device or video monitor 40 that displays medical treatment or dialysis information to a patient or operator. In an embodiment, the controller 30 further includes a touch screen 42 that interfaces with the video monitor 40 and electrically communicates with the I/O module 36. The touch screen 42 enables the patient or operator to input medical treatment or dialysis information into the controller 30.

The controller 30 controls the heater 16, the pump 20 and the valve actuator 26 in a number of different phases that make up a single medical or dialysis treatment. In a first pump fill phase, controller 30 activates the pump 20 to pump medical fluid or dialysate from one of the supply bags 14. In FIG. 1, the controller 30 commands a vacuum source 44, including an air pump motor 46, to pull a vacuum on both sides of the pump 20 through a first vacuum line 48 and a second vacuum line 50. The vacuum lines 48 and 50 pull respective vacuums through first and second pump chamber walls to suction one of a pair of opposing membranes inside the pump chamber against the interior of the pump chamber. The other membrane is held against a piston head in the pump 20. The other membrane alternatively temporarily or permanently mechanically attaches to the piston head, rendering the vacuum on the piston side of the pump 20 unnecessary.

With the membranes maintained against the interior of the pump chamber and the piston head, the controller 30 commands the linear actuator 24 to withdraw within the pump 20. The withdrawal causes the membranes inside the pump chamber to pull further apart. At this time, the controller 30 controls the valve actuator 26 so that only valve V1 is open. The pulling apart of the membranes causes a negative pressure to occur in fill line 52, wherein the negative pressure pulls medical fluid or dialysate from the supply bag 14, through the fill line 52, into a receptacle created by the opened membranes inside the pump chamber of pump 20.

In a patient fill phase, with the negative pressure still maintained by the vacuum source 44, through the pump chamber walls, on the interior membranes, the controller 30 causes the linear pump actuator 24 to move upwards within the pump 20. The upward movement of the actuator 24 and an attached piston head provides a positive mechanical pressure that closes the membrane receptacle and thereby pumps the medical fluid out of the pump 20. At this time, the controller 30 controls the valve actuator 26 so that only valves V2 and V3 are open. Consequently, all of the fluid exiting pump 20 is pumped through a heater line 54, past the in-line heater 16, through a catheter line 56, and into the patient, for example, the patient's peritoneal cavity 12. The catheter line 56 in an embodiment connects to a single lumen catheter, which is implanted into the patient 12. Although, in other embodiments, the system 10 can employ a multi-lumen catheter.

The heater 16 in an embodiment, includes one or more electrical heating plates, which heat the medical fluid to roughly body temperature. The controller 30 energizes and de-energizes the heater 16 as necessary to obtain the proper fluid temperature. The controller 30 can close valves V2 and V3, located on opposing sides of the heater 16 in the heater line 54, if the medical fluid is too hot or too cold. The improperly heated dialysate does not enter the peritoneal cavity 12.

The controller 20 repeats the pump fill phase and the heater fill phase until the patient's the peritoneal cavity 12, becomes full of fluid according to the therapy protocol. In an embodiment, the volume inside the pump is about thirty to fifty milliliters, and an adult patient typically uses about two liters of dialysis fluid. Accordingly, the pump fill phase and the heater fill phase can be repeated on the order of fifty times. In an embodiment, the pump actuator 24 maintains a fluid pressure at the pump 20 of about three pounds per square inch ("psi").

The system 10 provides a fluid volume sensor 60, which measures the actual volume of medical fluid that has been forced through the pump 20. By summing multiple individual pump volumes, the controller accurately knows how much medical fluid or dialysate has been delivered to the patient 12. The system 10 in an embodiment repeats the pump fill phase and the heater fill phase until the pump 20 has delivered a predetermined volume of medical fluid. The predetermined volume can be inputted into the controller 30 by a patient or operator via the touch screen 42.

In a dwell phase, the controller 30 lets the medical fluid or dialysate remain within the patient 12 for an amount of time, which can be controlled by the controller 30, the patient 12 or an operator. In an embodiment, the controller 30 determines the dwell time, but the patient 30 or operator can override the system 10 and command that the system 10 remove the medical fluid from the patient 12.

In a second pump fill phase, the medical fluid is removed from the patient 12. The controller 30 and the actuator 26 open valve V4, while shutting the remaining valves. With the vacuum source still maintaining a negative pressure on the membranes inside the pump 20, the linear actuator 24 withdraws the pump piston within the chamber of pump 20 and reopens the receptacle between the membranes. The negative pressure created by the opening receptacle pulls the medical fluid from the patient 12, through the catheter line 56 and into the membrane receptacle formed inside the pump 20.

In a drain phase, with the negative pressure still maintained by the vacuum source 44, through the pump chamber walls, on the interior membranes, the controller 30 causes the linear pump actuator 24 to move upwardly within the pump 20. The upward movement of the actuator 24 causes a positive mechanical pressure to close the membrane receptacle and thereby pump the medical fluid out of the pump 20. At this time, the controller 30 controls the valve actuator 26 so that only valve V5 is open. Consequently, all of the fluid exiting pump 20 is pumped through a drain line 58 and into the drain 18. Drain 18 can be a drain bag or a drain pipe inside a home, a hospital or elsewhere.

One embodiment of the fluid volume sensor 60 is described in more detail below in connection with the description of the diaphragm pump 20. Besides the fluid volume sensor 60, the system 10 includes various other desired types of sensors.

The system 10 includes temperature sensors 62, such as the sensors T1 to T4, which measure the temperature at relevant places within the system 10. In an embodiment, the sensors 62 are non-invasive, however, any other types of temperature sensors may be employed. As illustrated in FIG. 1, sensors T1 and T2 provide redundant post heater feedback of the fluid temperature to the controller 30. Sensor T3 provides a temperature of the medical fluid prior to heating. Sensor T4 provides the ambient temperature.

The system 10 also provides temperature sensors 62 that monitor the temperature of the heater 16. In an embodiment, the heater 16 is an in-line plate heater. The in-line plate heater 16 can have one or more heater plates, for example, two heater plates having a disposable unit placed between same. Separate temperature sensors PT1 and PT2 are provided to monitor the temperature of each of the plates of the plate heater. The system 10 can thereby control each plate heater individually.

The system 10 includes one or more air sensors 64, such as the sensor AS1, placed directly at the throat of the inlet and outlet of the pump 20. Another air sensor AS2 monitors air in the medical fluid after it leaves the heater 16 and just before the final shut off valve V3 leading to the catheter line 56. The controller 30 monitors the air content sensed by the air sensors 64 and thereby controls the system 10 to perform any necessary air purge. The system 10 can separate and discharge the air from the fluid or simply convey the air to the drain 18. The system 10 also includes an air vent solenoid 66, which is operated by the controller 30. The air vent solenoid 66 enables the system 10 to relieve the vacuum applied to one or both of the membranes in the pump 20.

The system 10 can accumulate air for various reasons. For example, the valves V1 to V5 and fluid lines, such as lines 52, 54, 56 and 58 may contain air prior to priming the system 10. The supply bags 14 may also introduce air into the pump 20. The patient 12 can also produce certain gasses, which become entrained in the dialysate and enter the pump 20. Further, if minor leaks exist in the fluid disposable or the connections to the supply bag 14, the catheter at the patient 12, or the drain bag, the pump 20 can draw air in through the leaks.

The system 10 provides various fluid pressure sensors 68. Fluid pressure sensors FP1 and FP2 provide a redundant pressure reading of the fluid in the fill line 52 leading to the pump 60. The fluid pressure sensors 68 provide a signal to the controller 30 that indicates the respective fluid pressure at that location. Based on the signals from the pressure sensors FP1 and FP2, the controller 30 operates the fluid pumps and valves to obtain and maintain a desired fluid pressure. As stated above, the system 10 maintains the pump pressure, for example, at about three psi.

The system 10 also provides various valve pressure sensors 70. Valve pressure sensors VP1 to VP5 detect the fluid pressure at the valves V1 to V5. The system 10 further provides one or more vacuum pressure sensors 72, for example, at the vacuum source 44, to ensure that a proper vacuum is maintained on the membrane receptacle within the pump 20.

In an embodiment, the fluid pressure, valve pressure and vacuum sensors 68, 70 and 72, respectively, are non-invasive sensors. That is, the sensors do not physically contact (and possibly contaminate) the medical fluid or dialysate. Of course, the system 10 can include other flow and pressure devices, such as flow rate sensors, pressure gauges, flowmeters, or pressure regulators in any suitable quantity and at any desired location.

The system 10 also includes various positioning sensors. In an embodiment, the positioning sensors include a linear encoder 74 that monitors the position of the linear pump actuator 24 and a rotary encoder 76 that monitors the angular position of the valve actuator 26 or camshaft. An encoder is one type of positioning feedback device that can be employed. Other types of positioning feedback systems include proximity sensors and magnetic pick-ups that sense a pulse, e.g., a gear tooth of a gear attached to the camshaft, and output the pulse to a counter or microprocessor.

The encoders 74 and 76 also typically provide a pulsed output, which is sent to the controller 30. The pulsed output tells the controller 30 how many steps or how far the linear pump actuator 24 or the valve actuator 26 is from a home position or home index 78. For example, the home position 78 can be the pump fully open or pump fully closed position for the linear encoder 74 and the zero degree position for the rotary encoder 76.

In an embodiment, the encoders 74 and 76 are absolute type encoders that know the location of the home position 78 even after a power loss. In another embodiment, the encoders 74 and 76 are incremental encoders and a battery back-up is provided to the controller so that the system 10 can maintain the location of the home position 78 even when no external power is applied. Further alternatively, system 10 can be programmed to automatically move the pump actuator 24 and the valve actuator 26 upon power up until a home position is sensed, wherein the system 10 can begin to run the main sequence.

Referring now to FIG. 2, an alternative system 100 is illustrated. The system 100 includes many of the same components having the same functionality (and the same reference numbers) as previously described. These components therefore do not need to be described again except to the extent that their functioning with the new components of system 100 differs. The primary difference between the system 100 and the system 10 is that the pump 120 of the system 100 is completely fluidly actuated and does not use the linear pump actuator 24 of the system 10.

In the pump fill phases, described above, the controller 30 activates the pump 120 to pump medical fluid or dialysate from one of the supply bags 14. To do so, the controller 30 commands vacuum source 44 (shown separately from motor 46 in FIG. 2), including a vacuum pump motor 46, to pull a vacuum on both sides of the pump 120, i.e., on both pump membranes, through vacuum lines 148 and 149. The vacuum pump motor 46 in this embodiment includes a rotary encoder 76 and a home position or home index 78. The rotary encoder 76 provides positional feedback of a member 150 within the vacuum source 44. The system 100 therefore knows if the vacuum source 44 can provide any additional suction or if the member 150 has bottomed out within the vacuum source 44.

To draw in medical fluid, the vacuum line 148 pulls a vacuum through first and second pump chamber walls to the pair of opposing membranes inside the pump chamber. The vacuum pulls the membranes against the interior of the pump chamber. At this time, the controller 30 controls the valve actuator 26 so that only valve V1 is open. The pulling apart of the membranes causes a negative pressure to occur in fill line 52, wherein the negative pressure pulls medical fluid or dialysate from the supply bag 14, through the fill line 52, into a receptacle created by the volume between the membranes inside the pump chamber of pump 120.

In an alternative embodiment, the pump 120 maintains a constant vacuum on one of the membranes, wherein the opposing membrane does the pumping work. To pump fluid out, the vacuum on one or membranes is released. The membranes, which have been stretched apart, spring back to a closed position. This operation is described in detail below.

The system 100 also includes a slightly different valve manifold than the system 10. The system 100 includes one less valve than the system 10, wherein the system 100 does not provide an extra valve (V3 in system 10) directly after the fluid heater 16. Obviously, those of skill in the art can find many ways to configure the valves and fluid flow lines of the systems 10 and 100. Consequently, the configuration of the valves and fluid flow lines of the systems 10 and 100 as illustrated merely represent practical examples, and the present invention is not limited to same.

II. Hardware Unit and Disposable Unit

Referring now to FIGS. 3A, 3B, 4A and 4B, both of the systems 10 and 100 include a hardware unit 110 and a disposable unit 160. The hardware unit 110 in an embodiment is portable and can be transported to and from a person's home. The hardware unit 110 includes a housing 112 that includes a base 114 and a lid 116. In an embodiment, the lid 116 is hinged to the base 114. Alternatively, the lid 116 is completely removable from the base. The lid 116 in either case opens to provide access to the interior of the housing 112, so as to allow the patient or operator to place and remove the disposable unit 160 into and from the hardware unit 110. The hardware unit 110 can be made of any protective, hard, resilient and/or flexible material, for example, plastic or metal sheet, and can have a decorative and/or finished surface.

Once the disposable unit 160 is placed inside the hardware unit 110, the operator closes the lid 116 and uses one or more locking or latching mechanism 118 (FIG. 3B) to safely house the disposable unit 160 within the hardware unit 110. FIG. 4A illustrates members 119 of the housing 112 to which the latching mechanism 118 of the lid 116 attaches. The hardware unit 110 displays the video monitor 40, which can have an associated touch screen 42 to input commands as described above. Alternatively, or in addition to the touch screen 42, the hardware unit 110 can provide one or more electromechanical switches or pushbuttons 43, 124, 125 and 127, analog controls 122 and/or lighted displays. The pushbuttons or switches 43, 124, 125 and 127 and knob 122 enable the patient or operator to input commands and information into the systems 10 and 100. The video monitor 40 provides medical treatment information 126 to the patient or operator.

FIG. 3B illustrates one set of dimensions for the hardware unit 110 of the present invention. The size and weight of the present invention are less than previous automated dialysis system. This feature belies the portability and ease of use of the system 10, 100 of the present invention. The size and weight enable the hardware unit 110 to be shipped economically by standard overnight courier services. In the event that the system 10, 100 of the present invention breaks down, a replacement unit can be economically shipped to the patient in time for the next therapy.

The hardware unit 110 in an embodiment is approximately 23 to 30 cm high and deep and in one preferred embodiment, as illustrated, about 25 cm high and deep. The hardware unit 110 in an embodiment is approximately 32 to 40 cm wide and in one preferred embodiment, as illustrated, about 34 cm wide. The internal volume of the unit 110 is therefore about 17,000 cm³ to about 36,000 cm³, and in one preferred embodiment, approximately 21,250 cm³ (1310 in³). Section view 4B aptly illustrates the many components maintained within this compact space and the efficient use of same. All these components and the hardware unit 110 have a total mass of about six to nine kilograms ("kg") and in one preferred embodiment about seven kilograms.

FIGS. 3A to 4B also illustrate that the architecture, configuration and layout of the hardware unit 110 provides an automated system that is also convenient to use. The components of the system 10,100 with which the patient must interact are placed on the top, front and sides of the unit 110. The flow control components are placed below the heater 116, which is placed below the disposable unit loading station. The monitor 40 and controls 43, 122, 124, 125 and 127 are placed in the front of the unit 110.

The hardware unit 110 contains the pump 20 or 120 and the linear pump actuator 24 if system 10 is employed. The hardware unit 110 also contains the valve actuator 26 including the valve motor 28, the in-line heater 16, the various sensors, the vacuum source 44 including the air pump motor 46 and the controller 30 as well as the other hardware described above. FIG. 4B illustrates that one of the pump chamber walls of the pump 20 or 120 is disposed in the lid 116 of the housing. In FIG. 4B, the heater 16 is disposed in the base 114 of the housing 112. Alternatively or additionally, the heater may be placed in the lid 116. The base 114 also contains the opposing pump chamber wall.

Referring now to FIGS. 3A, 4A, 4B, 5 and 6, various embodiments of the disposable unit 160 are illustrated. In each of the embodiments, the disposable unit 160 includes a pair of flexible membranes, including an upper flexible membrane 162 and a lower flexible membrane 164. The disposable unit 160 of FIG. 6 includes two pairs of flexible membranes, namely, membrane pair 166 and membrane pair 168. Each of the membrane pairs 166 and 168 also includes the upper flexible membrane 162 and the lower flexible membrane 164.

The flexible membranes 162 and 164 can be made of any suitable sterile and inert material, such as a sterile and inert plastic or rubber. For example, the membranes 162 and 164 can be buna-N, butyl, hypalon, kel-F, kynar, neoprene, nylon, polyethylene, polystyrene, polypropylene, polyvinyl chloride, silicone, vinyl, viton or any combination of these. One preferred material for the flexible membrane is described below in connection with FIGS. 13 and 14.

The membranes 162 and 164 are sealed together in various places to create fluid flow paths and receptacles between the membranes 162 and 164. The seals are heat seals, adhesive seals or a combination of both. FIGS. 3A, 4A, 5 and 6 illustrate that a generally circular seal 170 creates a substantially circular fluid pump receptacle 172 between the membranes 162 and 164. The pump receptacle 172 operates with the fluid pumps. Instead of the seal 170, one alternative embodiment is for the base 114 and lid 116 to press the membranes together to form the seal. FIGS. 4A and 5 illustrate that in an embodiment, the disposable unit 160 provides a secondary seal 174 to protect the systems 10 and 100 in case the primary seal 170 leaks or degrades during use.

FIGS. 3A, 4A and 4B illustrate that the fluid pump receptacle 172 fits between the clamshell shapes of the pumps 20 and 120 in the lid 116. The clamshell shapes defined by the base 114 and lid 116 of the hardware unit 110 together with the fluid pump receptacle 172 form the pump chamber of the pumps 20 and 120 of the present invention. The clamshell shapes in the base 114 and lid 116 include one or more ports with which to draw a vacuum on the membranes 162 and 164. In this manner, the membranes 162 and 164 are pulled towards and conform to the clamshell shapes in the base 114 and lid 116 and thereby create a negative pressure inside the receptacle 172 that pulls medical fluid from a supply bag 14 located outside the hardware unit 110, into the receptacle 172.

FIGS. 3A, 4A, 5 and 6 illustrate that a generally rectangular, spiral seal 178 creates a spiral heating path 180 between the membranes 162 and 164. The fluid heating path 180 runs from a valve manifold 190, through the spiral section, and back to the valve manifold 190. FIG. 4A illustrates that the fluid heating path 180 fits between the heating plates of the heater 16, which reside in the base 114 and lid 116 of the hardware unit 110. Providing a heat source on either side of the fluid heating path 180 enables the medical fluid to be quickly and efficiently heated. In alternative embodiments, however, the heater 16 can include only a single heater on one side of the fluid heating path 180 defined by the disposable unit 160 or multiple heaters on each side of the disposable unit 160.

The upper and lower membranes 162, 164 are attached to the disposable unit 160 utilizing heat sealing techniques as described herein. The membranes 162 and 164 is expandable so that when the disposable unit 160 is placed between a predefined gap between the upper and lower plates of the heater 16, the membranes 162 and 164 expand and contact the heater plates. This causes conductive heating to take place between the plates of the heater 16 and the membranes 162, 164 and between the membranes and the medical fluid. The predefined gap is slightly larger than the thickness of the disposable unit 160. Specifically, when dialysate moves through the fluid heating path 180 of the disposable unit 160, the membranes 162, 164 of the spiral wound fluid heating pathway 180 expand between the spiral seal 178 and touch the plates of the heater 16.

A. Separate Sets of Membranes

The disposable unit 160 of FIG. 6 is similar to the disposable units 160 of FIGS. 3A through 5. The in-line fluid heating path 180, however, is placed in a separate membrane pair 166 from the fluid pump receptacle 172 and the valve manifold 190, which are placed in a separate membrane pair 168. A pair of flexible tubes 182 and 184, which can be any suitable medical grade tubing, fluidly connect the valve manifold 190 to the fluid heating path 180. The tubes 182 and 184 can be connected to the membrane pairs 166, 168 by any desired means, such as, heat sealing, bonding, press-fitting or by any other permanent or removable fluid connection. When placed in the hardware unit 110, the heater 16 heats each side of the heater membrane pair 166, as in the other embodiments.

Separating the fluid heating path 180 from the fluid pump receptacle 172 and the valve manifold 190 enables the membranes of the respective pairs to be made of different materials. It is desirable that the membranes 162 and 164 of the heating pair 166 conduct or radiate heat efficiently. On the other hand, it is desirable that the membranes 162 and 164 of the fluid flow pair 166 withstand the forces of suction and mechanical actuation. It may therefore be desirable to use dissimilar materials for the membrane pair 166 and the membrane pair 168.

The membrane pair 166, defining the heater fluid flow path 180, additionally defines alignment holes 176 that align with pegs protruding from the base 114 or the lid 116 of the hardware unit 110. Each of the embodiments of the disposable unit 160 disclosed herein may be adapted to include alignment holes 176, which aid the patient or operator in properly placing the disposable unit 160 within the housing 112 of the hardware unit 110.

B. Rigid Frame and Bowed Sides

As shown in FIGS. 3A, 4A and 5, each of the embodiments of the disposable unit 160 disclosed herein may also be adapted to provide a rigid or semi-rigid member or frame 186, which in an embodiment, surrounds or substantially circumscribes the membranes 162 and 164 of the disposable unit 160. In an embodiment, the rigid member or frame 186 is made of a sterile, inert, rigid or semi-rigid plastic, for example, from one of or a combination of the plastics listed above for the membranes 162 and 164. The frame 186 aids the patient or operator in properly placing the disposable unit 160 within the housing 112 of the hardware unit 110.

In an embodiment, the housing 112 defines a pin or guide into which the frame 186 of the disposable unit 160 snugly fits. FIG. 5 illustrates that the frame 186 defines an aperture 161 that fits onto the pin or guide of the housing 112. The frame 186 can provide a plurality of apertures, such as the aperture 161, which fit onto a like number of pins or guides provided by the housing 112. FIG. 5 also illustrates that the frame 186 includes an asymmetrical member or chamfer 163. The chamfer 163 forms and angle, such as forty-five degrees, with respect to the other sides of the frame 186. The housing 112 defines or provides an area into which to place the disposable unit 160. The area has the asymmetrical shape of the frame 186 or otherwise provides guides that only allow the unit 160 to be placed in the housing 112 from a single direction. The chamfer 163 and the cooperating housing 112 ensure that when the patient places the disposable unit 160 in the housing 112, the bottom of the disposable unit 160 is placed in the housing 112 and the fluid inlets/outlets 196 face in the proper direction.

As discussed above, the disposable unit 160 includes a valve manifold 190. In an embodiment, the valve manifold 190 is made of a rigid or semi-rigid plastic, such as, from one of or a combination of the plastics listed above for the membranes 162 and 164. The valve manifold 190 is covered on either side by the upper and lower membranes 162 and 164 to thereby create a sealed and inert logic flow path for the systems 10 and 100.

In FIG. 5, the manifold 190 defines holes 192 and slots 194. The holes 192 define the location of the valves, for example, valves V1 to V5 of the system 10. The slots 194 define the fluid flow paths from the valves to the fluid pump receptacle 172, the fluid heating path 180 or to fluid inlets/outlets 196. The fluid inlets/outlets 196 individually lead to the supply bag 14, the catheter line 56, the patient 12 and the drain 18. The fluid inlets/outlets 196 may have various configurations and orientations, as contrasted by FIG. 3A. The drain 196 may also be adapted to connect to an external flexible tub via a method known to those of skill in the art.

In an embodiment, the rigid or semi-rigid frame 186 includes bowed sides 187 and 189, as illustrated in FIG. 5. The bowed sides 187 and 189 are formed with the frame 186 before the membranes 162 and 164 heat seal or adhesively seal to the frame 186 and manifold 190. The frame 186 and bowed sides 187 and 189 can be extruded plastic or plastic injection molded. The frame 186 can include as little as one bowed side, any number less than all, or have all sides be bowed.

In the illustrated embodiment, the sides 187 and 189 bow outward although they can alternatively bow inward. In a preferred embodiment, the sides are bowed in a direction of the plane of the frame 186 of the disposable unit 160. The bowed sides 187 and 189 increase the rigidity of the frame 186 and the disposable unit 160. The disposable unit is accordingly more easily placed in the housing 112 of the hardware unit 110. The bowed sides 187 and 189 reduce the amount of flexing or distortion of the frame 186 due to heat sealing or mechanically pressing membranes 162 and 164 onto the frame 186 and manifold 190.

C. Heat Seal Interface

Referring now to FIG. 7, an embodiment for heat sealing the membranes 162 and 164 to the manifold 190 is illustrated. In an embodiment, the manifold 190 is made of a rigid or semi-rigid plastic material as described above. Heat sealing the membranes 162 and 164 to the semi-rigid manifold 190, which in an embodiment is an injection molded component, requires different processing parameters than heat sealing the individual membranes 162 and 164 together, for example, at seal 170 of the fluid pump receptacle 172. In particular, heat sealing the membranes 162 and 164 to the manifold 190 can require more heat, more pressure and more heating time. The semi-rigid or rigid manifold 190 is appreciably thicker than the individual membranes 162 and 164. Consequently, relative to the thin membranes, the thicker manifold 190 acts as a heat sink. The bond between the thin membrane and thicker manifold 190 therefore requires more heat or energy than the heat seal bond between the thin membranes 162 and 164.

As illustrated in FIGS. 3A, 4A, 5 and 6, the disposable unit 160 requires both membrane to manifold and membrane to membrane seals. It is desirable to heat seal the entire disposable unit 160 in one step or process for obvious reasons. It should also be obvious that the heat sealing process should be performed so as avoid burning or melting one of the thin membranes 162 or 164.

FIG. 7 illustrates one embodiment for solving the heat sinking disparity between varying members. FIG. 7 illustrates a portion of the manifold 190, which is shown in its entirety in FIG. 5. In FIG. 5, the manifold 190 illustrates a port that connects to the fluid pump receptacle 172. This port is illustrated as port 205 in FIG. 7. FIG. 5 also illustrates two ports extending from the manifold 190 that fluidly connect to the fluid heating path 180. These ports are illustrated as ports 201 and 203 in FIG. 7. Both FIG. 5 and FIG. 7 illustrate that the injection molded manifold 190 defines a plurality of holes 192 and slots 194. The holes 192 operate with the valve actuator and the slots 194 form fluid pathways when enclosed by the membranes 162 and 164.

To reduce the amount of heat necessary to seal the membranes 162 and 164 to the manifold 190, the manifold 190 includes a side 193 having a lesser thickness than the remaining portion of the manifold 190. The thinner side 193 has less mass and therefore absorbs less localized heat than would a manifold of constant thickness. The side 193 also defines or includes a tapered portion 195. The tapered portion 195 provides flat surfaces on which to seal the membranes 162 and 164 and also positions the membranes 162 and 164 together so that in an embodiment a membrane to membrane seal may also be made in addition to the membrane to manifold 190 seal.

The tapered edges 195 form an interface for the membranes 162 and 164 to seal to the manifold 190, which occurs along continuous stretches of the sides 193 of the manifold 190 that require sealing or that would otherwise come into contact with the medical fluid. Therefore, as illustrated in FIG. 5, the side of the manifold 190 defining the input/output ports 196 does not need to be tapered as illustrated in FIG. 7. Also, as illustrated in FIG. 7, the tapered edges 195 of the thin sides 193 discontinue where the ports 201, 203, and 205 extend from the manifold 190.

The ports 201, 203 and 205 also form tapered edges 207. Tapered edges 207 form an interface for heat sealing the parts to the membranes 162 and 164. As described above, the tapered edges 207 of the ports 201, 203 and 205 also enable a membrane to membrane seal to take place directly next to the membrane to tapered edge 207 seal. The tapered edges 195 and 207 in a preferred embodiment gradually taper towards the knife-like edge. In other embodiments, the tapered edges 195 and 207 may take on different forms or shapes, such as a rounded edge, a blunter edge or may simply be further reduced in thickness from side 193 of the manifold 190. As illustrated, the ports 201, 203 and 205 in an embodiment form ovular openings. The tapered ovular openings provide a smoother transition angle than would a circular outer diameter. The ovular openings perform as well as round openings from a fluid flow standpoint as long as open area of the inner oval is not less than the open area of a suitable circular port.

The ports 201, 203 and 205 also form raised portions 209. The raised portions 209 form a bead of polymeric material along the tops of the ports 201, 203 and 205 and the tapered edges 207. The beads can be additionally or alternatively placed along the tapered edges 195 and or the sides 193. The raised portions or beads 209 provide an extra thin area of plastic that melts or deforms to provide a flux-like sealant that enables the membranes 162 and 164 to seal to the manifold 190. The beads create a concentrated strip of higher temperature plastic than the surrounding plastic of the manifold 190. The membranes 162 and 164 seal to the manifold 190 without having to heat a larger area of the manifold 190. The raised portions or beads 209 help to seal curved portions and corners created by the manifold 190.

D. One-Piece Tip Protector Organizer and Vented Tip Protector

Referring now to FIG. 8, one embodiment of a one-piece tip protector organizer 270 is illustrated. In the HOMECHOICE® peritoneal dialysis system provided by the assignee of the present invention, a disposable set is prepackaged and provided to the patient. The patient opens up the package, wherein each of the components is sterilized and maintained within the disposable set. The disposable set includes a disposable unit and a number of tubes emanating from the disposable unit. Like the present invention, the HOMECHOICE® disposable unit includes a drain line tube that connects to one or more fill bag tubes, and a tube that connects to a patient transfer set. Each of these tubes requires a separate tip protector. That is, after sterilizing the inside of the disposable unit and the tubes, for example, using ethylene oxide, the ends of the tubes would have to be capped off so that the sterilization of the inside of the system would be maintained. The HOMECHOICE® system provides a separate tip protector for each tube.

The one-piece tip protector organizer 270 of the present invention provides a single body 272 (which may actually be made of a plurality of pieces) that defines or provides a plurality of tip protectors 274, 276, 278 and 280. The vented tip protector 270 not only houses and protects the connectors at the ends of the tubes emanating from the disposable unit 160, the one-piece tip protector 270 also organizes and orders the tubes according to the steps of the dialysis therapy. In the illustrated embodiment, the tip protector 274 is a tip protector for a drain line connector 284 connected to a drain line 285 that leads to the appropriate port of the disposable unit 160. The tip protectors 276 and 278 are supply bag protectors that protect the connectors 286 and 288 that connect to the ends of the tubes 287 and 289 that run to a "Y" connection 287/289, wherein the leg of the "Y" connection 287/289 runs to the appropriate port of the disposable unit 160. The tip protector 280 is a patient fluid line protector. The tip protector 280 houses and protects a connector 290 that connects to patient tube 292, which runs to the appropriate port of the disposable unit 160.

Each of the tubes 285, the "Y" connection 287 and 289 and the patient fluid tube 292 in an embodiment are made of polyvinylchloride ("PVC") having an inner diameter of 4 mm and an outer diameter of 5 mm. As illustrated, the one-piece tip protector organizer 270 is adaptable to receive and protect various types of fluid connectors. The fluid connector 284 that runs via tube 285 to the drain line port of the disposable unit 160 is in an embodiment largely the same as the port that emanates from the supply bags 14. The ports that emanate from the supply bags 14 also include a membrane which is pierced by the sharp stem of the supply bag connectors 286 and 288. The drain line connector 284 does not include the membrane of the supply bag 14 as it is not needed. The tip protector 290 that connects to the end of the patient fluid tube 292 is discussed in detail below.

In one preferred embodiment, the system 10, 100 of the present invention provides two, six liter supply bags 14. The two, six liter bags provide an economic amount of peritoneal dialysis fluid, which is enough fluid to provide a number of fill, dwell and drain cycles during the evening while the patient sleeps. The one-piece organizer 270 therefore provides two tip protectors 276 and 278, which house and protect the supply connectors 286 and 288. In alternative embodiments, the one-piece organizer 270 can define or provide any number of supply bag tip protectors. Any number of supply bags can be additionally linked via "Y" or "T" type tubing links.

The one-piece organizer 270 can provide additional tip protectors such as a last bag protector, which protects a line that runs to a bag that holds enough peritoneal fluid, e.g., two liters, for a final fill for the patient during the daytime. In this case, an additional last bag tube, not illustrated, would connect to a connector, which would be a bag piercing connector, the same as or similar to the fill bag connectors 286 and 288.

The body 272 of the tip protector organize 270 is in an embodiment also made of PVC. The tip protectors 274, 276, 278 and 280 are injection molded or blow molded. Alternatively, the tip protectors can be separately applied to the body 272. As seen in FIG. 8, one or more of the tip protectors can include flutes, threads or other protrusions that aid in grasping and holding the respective tube connector. Further, while the organizer 270 is generally referred to herein as a "one-piece" organizer, the organizer 270 may itself be comprised of any number of pieces. "One-piece" refers to the feature that a single unit houses a multitude of tip protectors.

The one-piece organizer 270 also includes a rim 294 that extends outwardly from the main portion of the body 272, and which circumvents the main portion of the body 272. Referring now to FIG. 9, a cross section of the one-piece organizer 270 illustrates that the rim 294 tapers downwardly from the drain line tip protector 274 towards the patient fluid tip protector 280. That is, the rim 294 is higher or thicker at the drain line end than it is at the patient fluid line end. This enables the one-piece tip protector organizer 270 to be mounted to the hardware unit 110 in only one orientation.

FIG. 3A illustrates that the one-piece tip protector organizer 270 in an embodiment slides into the hardware unit 110 vertically. The hardware unit 110 includes or provides a pair of members 296 that extend outwardly from a side wall of the hardware unit 110. FIGS. 3B and 4A illustrate another embodiment, wherein the rim 294 of the organizer 270 slides vertically into a notch 297 defined or provided by the base 114 of the housing 112 of the hardware unit 110. The rim 294 of the organizer 270 slides between the members 296 and the side wall of the hardware unit 110. The members 296 extend further and further outwardly running towards the top of the hardware unit 110. The taper of the members 296 corresponds to the taper of the rim 294 of the organizer 270 so that the organizer 270 can only slide into the hardware unit 110 vertically from one direction.

FIG. 9 also illustrates that the tip protectors 274, 276, 278 and 280 can have various cross-sectional shapes. Each of the tip protectors includes a solid bottom and sides that seal around the respective connectors 284, 286, 288 and 290, so that the one-piece organizer 270 maintains the sterility of the system even after the patient removes the disposable set from a sealed sterilized container. The one-piece organizer 270 illustrated in FIGS. 8 and 9 mounts in a sturdy fashion to the side of the hardware unit 110. Via this solid connection, the patient is able to remove the tubes 285, 287, 289 and 292 using only one hand in many cases. The interface between the hardware unit 110 and the organizer 270 simplifies the procedure for the patient and provides a solid, sterile environment for the tubes and associated connectors until used.

FIG. 3A also illustrates another possible embodiment wherein an alternative one-piece organizer 298 is integral to or provided by the frame 186 of the disposable unit 160. Here, the tubes 196, indicated generally, are horizontally organized as opposed to the vertical arrangement of the tip protector 270 in the housing 112. The horizontal one-piece organizer 298 illustrates that the concept of protecting and organizing the tubes before use can be provided in a variety of places and orientations in the system 10.

In one embodiment, the tip protector and organizer 270 structures the tubes 285, 287, 289 and 292 in a downwardly vertical order, such that the first tube that the patient is supposed to pull when starting the dialysis therapy is provided on top, the next tubes that the patient is supposed to pull are provided in the middle and the final tube is provided lowest on the vertically oriented one-piece organizer 270. According to one preferred protocol, the patient first removes the drain connector 284 from the tip protector 274 and runs the drain line 285 to a toilet, drain bag or other drain. The patient then removes the supply connectors 286 and 288 and punctures the supply bags 14 (FIGS. 1 and 2). At this point, dialysate can be pumped to the disposable unit 160 and throughout the system 10. The controller 30 of the system 10, 100 begins a priming cycle, which is discussed in more detail below.

Once priming is complete, system 10, 100 prompts the patient to remove the primed patient line 292 and connect same to the transfer set implanted into the patient. The transfer set (not illustrated) includes a catheter positioned into the patient's peritoneal cavity and a tube running to the catheter. The tube also includes a connector that couples to the connector 290. At this point, system 10, 100 can begin to either drain spent peritoneal fluid from the patient 12 to the drain 18 or pull new fluid from one or both of the supply bags 14 and fill the patient's peritoneal cavity 12.

Referring now to FIGS. 10 to 12, one embodiment for the patient line tip protector 280 of the present invention is illustrated. The HOMECHOICE® system produced by the assignee of the present invention primes the patient fluid line by allowing the patient connector to be held vertically approximately at the same level as the supply bag. In this manner, when the HOMECHOICE® system primes the disposable unit, gravity feeds peritoneal fluid into the patient fluid line up to the end of the patient fluid connector. The patient fluid connector is open so that air can freely escape when the peritoneal fluid is fed by gravity through the patient line. HOMECHOICE® system enables the patient fluid line to be primed without counting pump strokes or having to meter out a known volume of dialysate, techniques which are complicated and prone to failure.

The system 10, 100 of the present invention provides a different apparatus and method of priming without having to calculate the amount of fluid that is needed to just reach but not surpass the patient connector of the patient fluid line. FIG. 10 shows a cross-section of the patient fluid connector 290 that has been inserted into the vented tip protector 280. FIG. 11 illustrates a cross section of the patient fluid connector 290 only. FIG. 12 illustrates a cross section of the tip protector 280 only. A hydrophobic membrane 300 is placed on the outer edge of the tip protector 280. The tip protector 280 defines a fluid lumen 302 that runs through the entire length of the tip protector 280. The hydrophobic membrane 300 covers the fluid lumen 302. The hydrophobic membrane 300 allows air to purge from inside the patient's fluid line but does not allow water or peritoneal fluid to flow through same.

It should be appreciated that the vented tip protector 280 including the hydrophobic membrane 300 is not limited to being placed in the one-piece tip protector organizer 270. FIG. 9 illustrates that the one-piece organizer 270 does include the patient tip protector 280 having the hydrophobic membrane 300 and the fluid lumen 302. The vented tip protector 280 in an alternative embodiment, however, can be provided as a separate or stand alone tip protector, similar to the one used on the HOMECHOICE® system provided by the assignee of the present invention.

Hydrophobic membranes, such as the hydrophobic membrane 300 employed herein, are commercially available. One suitable hydrophobic membrane is produced by Millipore, 80 Ashby Road, Bedford, Mass. 01730. FIG. 12 best illustrates that the hydrophobic membrane heat seals or sonically seals to the tip protector 280. The fluid lumen 302 in an embodiment is relatively small in diameter, such as approximately fifty to seventy thousandths of an inch (1.25 to 1.75 mm).

The vented tip protector 280 and the patient fluid connector 290 also cooperate so that when the system 10, 100 is completely primed, the tip protector 280 and connector 290 minimize the amount of fluid that spills when the patient removes the patient fluid connector 290 from the tip protector 280. The connector 290 includes or provides a male lure 304 that mates with a female lure 306 best seen in FIG. 10. The mating lures 304 and 306 prevent peritoneal fluid from filling the cavity of the tip protector 280, which must be wide enough to house the flange 308 of the patient fluid connector 290. FIG. 12 illustrates that the seal interface between the male lure 304 of the connector 290 and the female lure 306 of the vented tip protector 280 reduces the volume significantly from an interior volume 310 existing around the male lure 304 to the fifty to seventy thousandths diameter of the lumen 302.

To prime the system 10, 100 the patient removes the drain line 285 from the tip protector 274 and places it into a tub, toilet or drain bag 18. The patient removes the two or more supply bag connectors 286 and 288 and punctures seal membranes (not illustrated) of the supply bags 14. System 10, 100 may then automatically begin pump priming or may begin pump priming upon a patient input. In either case, system 10, 100 pumps fluid from one or both of the supply bags 14 through the connectors 286 and 288 and tubes 287 and 289, into the disposal disposable unit 160, out the patient fluid line 292 and into the patient fluid connector 290, which is still housed in the vented tip protector 280 of the one-piece organizer 270. The organizer 270 is vertically housed in the hardware unit 110 as seen in FIGS. 3A and 3B.

When the peritoneal fluid reaches the patient fluid connector 290, most all the air within the system 10 has been pushed through the hydrophobic membrane 300 attached at the end of the tip protector 280 housed in the one-piece tip protector 270. The nature of the hydrophobic membrane 300 is that it allows air to pass through but filters or does not allow water or peritoneal fluid to pass through same. Thus, when the fluid finally reaches the hydrophobic membrane 300, the lack of any additional space in which to flow fluid causes the pressure to increase within the system 10, 100. The system 10, 100 provides one or more pressure sensors, for example pressure sensors 68 (marked as FP1, FP2 and FPT in FIGS. 1 and 2).

One or more of the pressure sensors 68 sense the increase in pressure due to the peritoneal fluid backing up against the hydrophobic filter 300. The pressure sensor(s) sends a signal to the I/O module 36 of the controller 30. The controller 30 receives the signal and is programmed in memory 32 to shut down the diaphragm pump 20, 120. In this manner, the system 10 self-primes each of the fill lines 287 and 289, the disposal disposable unit 160 and the patient fluid line 292 automatically and without need for controlled volume calculations or gravity feeding.

System 10, 100 also includes one or more safety features that may be based upon a volume calculation. That is, under normal operations, the system 10, 100 does not control the priming using a volume calculation. However, in the case where for example the patient removes the patient fluid connector 290 from the vented tip protector 280 of the one-piece tip organizer 270 before the system 10, 100 senses a pressure increase and stops the pumps 10, 100, the system 10, 100 can employ and alarm calculation, wherein the system 10, 100 knows that it has pumped too much peritoneal fluid (e.g., a predetermined amount more than the internal volume of the system) and shuts down pump 20, 120 accordingly.

III. Membrane Material For the Disposable Unit

Referring now to FIGS. 13 and 14, upper and lower membranes 162, 164 can be fabricated from a monolayer film structure 312 (FIG. 13) or a multiple layer film structure 312 (FIG. 14). The upper and lower membranes 162, 164 can be fabricated from a monolayer film structure 312 (FIG. 13) or a multiple layer film structure 312 (FIG. 14). The film 312 is constructed from a non-PVC containing polymeric material and must satisfy numerous physical property requirements. The film 312 must have a low modulus of elasticity so that it can be deformed under low pressure to function as a pumping element. What is meant by low modulus is the film 312 has a modulus of elasticity when measured in accordance with ASTM D882, of less than about 10,000 psi, more preferably less than about 8,000 psi and even more preferably less than about 5,000 psi and finally, less than about 3,000 psi, or any range or combination of ranges defined by these numbers. The film 312 must have adequate thermal conductivity to allow for in-line heating. The film has a thermal conductivity of greater than 0.13 W/meters-° K when measured using a Hot Disk™ sold by Mathis Instruments Ltd. The film 312 must be capable of being heat sealed to cassette 160. The film 312 must be capable of being sterilized by exposure to gamma rays, by exposure to steam for a period of time (typically 1 hour), and exposure to ethylene oxide without significant degradation of the film or having an adverse effect on the dialysis solution. Finally, the film 312 must be capable of being extruded at high rates of speed of greater than 50 ft/min.

The monolayer structure 312 is formed from a blend of from about 90% to about 99% by weight of a first component containing a styrene and hydrocarbon copolymer and from about 10% to about 1% of a melt strength enhancing polymer and more preferably a high melt strength polypropylene.

The term "styrene" includes styrene and the various substituted styrenes including alkyl substituted styrene and halogen substituted styrene. The alkyl group can contain from 1 to about 6 carbon atoms. Specific examples of substituted styrenes include alpha-methylstyrene, beta-methylstyrene, vinyltoluene, 3-methylstyrene, 4-methylstyrene, 4-isopropylstyrene, 2,4-dimethylstyrene, o-chlorostyrene, p-chlorostyrene, o-bromostyrene, 2-chloro-4-methylstyrene, etc. Styrene is the most preferred.

The hydrocarbon portion of the styrene and hydrocarbon copolymer includes conjugated dienes. Conjugated dienes which may be utilized are those containing from 4 to about 10 carbon atoms and more specifically, from 4 to 6 carbon atoms. Examples include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, chloroprene, 1,3-pentadiene, 1,3-hexadiene, etc. Mixtures of these conjugated dienes also may be used such as mixtures of butadiene and isoprene. The preferred conjugated dienes are isoprene and 1,3-butadiene.

The styrene and hydrocarbon copolymers can be block copolymers including di-block, tri-block, multiblock, and star block. Specific examples of diblock copolymers include styrene-butadiene, styrene-isoprene, and selectively hydrogenated derivatives thereof. Examples of tri-block polymers include styrene-butadiene-styrene, styrene-isoprene-styrene, alpha-methylstyrene-butadiene-alpha-methylstyrene, and alpha-methylstyrene-isoprene-alpha-methylstyrene and selectively hydrogenated derivatives thereof.

The selective hydrogenation of the above block copolymers may be carried out by a variety of well known processes including hydrogenation in the presence of such catalysts as Raney nickel, noble metals such as platinum, palladium, etc., and soluble transition metal catalysts. Suitable hydrogenation processes which can be used are those wherein the diene-containing polymer or copolymer is dissolved in an inert hydrocarbon diluent such as cyclohexane and hydrogenated by reaction with hydrogen in the presence of a soluble hydrogenation catalyst. Such procedures are described in U.S. Pat. Nos. 3,113,986 and 4,226,952, the disclosures of which are incorporated herein by reference and made a part hereof.

Particularly useful hydrogenated block copolymers are the hydrogenated block copolymers of styrene-isoprene-styrene, such as a polystyrene-(ethylene/propylene)-polystyrene block polymer. When a polystyrene-polybutadiene-polystyrene block copolymer is hydrogenated, the resulting product resembles a regular copolymer block of ethylene and 1-butene (EB). This hydrogenated block copolymer is often referred to as SEBS. When the conjugated diene employed is isoprene, the resulting hydrogenated product resembles a regular copolymer block of ethylene and propylene (EP). This hydrogenated block copolymer is often referred to as SEPS. When the conjugated diene is a mixture of isoprene and butadiene the selectively hydrogenated product is referred to as SEEPS. Suitable SEBS, SEPS and SEEPS copolymers are sold by Shell Oil under the tradename KRATON, by Kurary under the tradename SEPTON® and HYBRAR®.

The block copolymers of the conjugated diene and the vinyl aromatic compound can be grafted with an alpha,beta-unsaturated monocarboxylic or dicarboxylic acid reagent. The carboxylic acid reagents include carboxylic acids per se and their functional derivatives such as anhydrides, imides, metal salts, esters, etc., which are capable of being grafted onto the selectively hydrogenated block copolymer. The grafted polymer will usually contain from about 0.1 to about 20%, and preferably from about 0.1 to about 10% by weight based on the total weight of the block copolymer and the carboxylic acid reagent of the grafted carboxylic acid. Specific examples of useful monobasic carboxylic acids include acrylic acid, methacrylic acid, cinnamic acid, crotonic acid, acrylic anhydride, sodium acrylate, calcium acrylate and magnesium acrylate, etc. Examples of dicarboxylic acids and useful derivatives thereof include maleic acid, maleic anhydride, fumaric acid, mesaconic acid, itaconic acid, citraconic acid, itaconic anhydride, citraconic anhydride, monomethyl maleate, monosodium maleate, etc.

The first component containing a styrene and hydrocarbon block copolymer can be modified by adding an oil, such as a mineral oil, paraffinic oil, polybutene oil or the like. The amount of oil added to the styrene and hydrocarbon block copolymer is from about 5% to about 40%. The first component can also contain a polypropylene up to about 20% by weight of the first component. One particularly suitable first component is an oil modified SEBS sold by the Shell Chemical Company under the product designation KRATON G2705.

The melt strength enhancing polymer preferably is a high melt strength polypropylene. Suitable high melt strength polypropylenes can be a homopolymer or a copolymer of polypropylene and can have free end long chain branching or not. In one preferred form of the invention, the high melt strength polypropylene will have a melt flow index within the range of 10 grams/10 min. to 800 grams/10 min., more preferably 10 grams/10 min. to 200 grams/10 min, or any range or combination of ranges therein. High melt strength polypropylenes are known to have free-end long chain branches of propylene units. Methods of preparing polypropylenes which exhibit a high melt strength characteristic have been described in U.S. Pat. Nos. 4,916,198; 5,047,485; and 5,605,936 which are incorporated herein by reference and made a part hereof. One such method includes irradiating a linear propylene polymer in an environment in which the active oxygen concentration is about 15% by volume with high energy ionization radiation at a dose of 1×10⁴ megarads per minute for a period of time sufficient for a substantial amount of chain scission of the linear propylene polymer to occur but insufficient to cause the material to become gelatinous. The irradiation results in chain scission. The subsequent recombination of chain fragments results in the formation of new chains, as well as joining chain fragments to chains to form branches. This further results in the desired free-end long chain branched, high molecular weight, non-linear, propylene polymer material. Radiation is maintained until a significant amount of long chain branches form. The material is then treated to deactivate substantially all the free radicals present in the irradiated material.

High melt strength polypropylenes can also be obtained as described in U.S. Pat. No. 5,416,169, which is incorporated in its entirety herein by reference and made a part hereof, when a specified organic peroxide (di-2-ethylhexyl peroxydicarbonate) is reacted with a polypropylene under specified conditions, followed by melt-kneading. Such polypropylenes are linear, crystalline polypropylenes having a branching coefficient of substantially 1, and, therefore, has no free ende long-chain branching and will have a intrinsic viscosity of from about 2.5 dl/g to 10 dl/g.

Suitable copolymers of propylene are obtained by polymerizing a propylene monomer with an α-olefin having from 2 to 20 carbons. In a more preferred form of the invention the propylene is copolymerized with ethylene in an amount by weight from about 1% to about 20%, more preferably from about 1% to about 10% and most preferably from 2% to about 5% by weight of the copolymer. The propylene and ethylene copolymers may be random or block copolymers. In a preferred form of the invention, the propylene copolymer is obtained using a single-site catalyst.

The components of the blend can be blended and extruded using standard techniques well known in the art. The film 312 will have a thickness of from about 3 mils to about 12 mils, more preferably from 5 mils to about 9 mils.

FIG. 14 shows a multiple layer film having a first layer 314 and a second layer 316. FIG. 14 shows the use of two layers but the present invention contemplates using more than two layers provided the above-mentioned material property requirements are met. The first layer 314 can be of the same polymer blend used to fabricate the monolayer structure and in a more preferred form of the invention will define a seal layer for joining the film the cassette 160. The second layer 316 can be made from non-PVC containing materials and preferably is selected from polyolefins, polybutadienes, polyesters, polyester ethers, polyester elastomers, polyamides and the like and blends of the same. A tie layer or tie layers (not shown) may be required to adhere additional layers to the first layer 314.

Suitable polyolefins include homopolymers and copolymers obtained by polymerizing alpha-olefins containing from 2 to 20 carbon atoms, and more preferably from 2 to 10 carbons. Therefore, suitable polyolefins include polymers and copolymers of propylene, ethylene, butene-1, pentene-1, 4-methyl-1-pentene, hexene-1, heptene-1, octene-1, nonene-1 and decene-1. Most preferably the polyolefin is a homopolymer or copolymer of propylene or a homopolymer or copolymer of polyethylene.

Suitable homopolymers of polypropylene can have a stereochemistry of amorphous, isotactic, syndiotactic, atactic, hemiisotactic or stereoblock. In one preferred form of the invention the homopolymer of polypropylene is obtained using a single site catalyst.

It is also possible to use a blend of polypropylene and α-olefin copolymers wherein the propylene copolymers can vary by the number of carbons in the α-olefin. For example, the present invention contemplates blends of propylene and α-olefin copolymers wherein one copolymer has a 2 carbon α-olefin and another copolymer has a 4 carbon α-olefin. It is also possible to use any combination of α-olefins from 2 to 20 carbons and more preferably from 2 to 8 carbons. Accordingly, the present invention contemplates blends of propylene and α-olefin copolymers wherein a first and second α-olefins have the following combination of carbon numbers: 2 and 6, 2 and 8, 4 and 6, 4 and 8. It is also contemplated using more than 2 polypropylene and α-olefin copolymers in the blend. Suitable polymers can be obtained using a catalloy procedure.

It may also be desirable to use a high melt strength polypropylene as defined above.

Suitable homopolymers of ethylene include those having a density of greater than 0.915 g/cc and includes low density polyethylene (LDPE), medium density polyethylene (MDPE) and high density polyethylene (HDPE).

Suitable copolymers of ethylene are obtained by polymerizing ethylene monomers with an α-olefin having from 3 to 20 carbons, more preferably 3-10 carbons and most preferably from 4 to 8 carbons. It is also desirable for the copolymers of ethylene to have a density as measured by ASTM D-792 of less than about 0.915 g/cc and more preferably less than about 0.910 g/cc and even more preferably less than about 0.900 g/cc. Such polymers are oftentimes referred to as VLDPE (very low density polyethylene) or ULDPE (ultra low density polyethylene). Preferably the ethylene α-olefin copolymers are produced using a single site catalyst and even more preferably a metallocene catalyst systems. Single site catalysts are believed to have a single, sterically and electronically equivalent catalyst position as opposed to the Ziegler-Natta type catalysts which are known to have a mixture of catalysts sites. Such single-site catalyzed ethylene α-olefins are sold by Dow under the trade name AFFINITY, DuPont Dow under the trademark ENGAGE® and by Exxon under the trade name EXACT. These copolymers shall sometimes be referred to herein as m-ULDPE.

Suitable copolymers of ethylene also include ethylene and lower alkyl acrylate copolymers, ethylene and lower alkyl substituted alkyl acrylate copolymers and ethylene vinyl acetate copolymers having a vinyl acetate content of from about 5% to about 40% by weight of the copolymer. The term "lower alkyl acrylates" refers to comonomers having the formula set forth in Diagram 1:

##STR1##

The R group refers to alkyls having from 1 to 17 carbons. Thus, the term "lower alkyl acrylates" includes but is not limited to methyl acrylate, ethyl acrylate, butyl acrylate and the like.

The term "alkyl substituted alkyl acrylates" refers to comonomers having the formula set forth in Diagram 2:

##STR2##

R₁ and R₂ are alkyls having 1-17 carbons and can have the same number of carbons or have a different number of carbons. Thus, the term "alkyl substituted alkyl acrylates" includes but is not limited to methyl methacrylate, ethyl methacrylate, methyl ethacrylate, ethyl ethacrylate, butyl methacrylate, butyl ethacrylate and the like.

Suitable polybutadienes include the 1,2- and 1,4-addition products of 1,3-butadiene (these shall collectively be referred to as polybutadienes). In a more preferred form of the invention the polymer is a 1,2-addition product of 1,3 butadiene (these shall be referred to as 1,2 polybutadienes). In an even more preferred form of the invention the polymer of interest is a syndiotactic 1,2-polybutadiene and even more preferably a low crystallinity, syndiotactic 1,2 polybutadiene. In a preferred form of the invention the low crystallinity, syndiotactic 1,2 polybutadiene will have a crystallinity less than 50%, more preferably less than about 45%, even more preferably less than about 40%, even more preferably the crystallinity will be from about 13% to about 40%, and most preferably from about 15% to about 30%. In a preferred form of the invention the low crystallinity, syndiotactic 1,2 polybutadiene will have a melting point temperature measured in accordance with ASTM D 3418 from about 70° C. to about 120° C. Suitable resins include those sold by JSR (Japan Synthetic Rubber) under the grade designations: JSR RB 810, JSR RB 820, and JSR RB 830.

Suitable polyesters include polycondensation products of di-or polycarboxylic acids and di or poly hydroxy alcohols or alkylene oxides. In a preferred form of the invention the polyester is a polyester ether. Suitable polyester ethers are obtained from reacting 1,4 cyclohexane dimethanol, 1,4 cyclohexane dicarboxylic acid and polytetramethylene glycol ether and shall be referred to generally as PCCE. Suitable PCCE's are sold by Eastman under the trade name ECDEL. Suitable polyesters further include polyester elastomers which are block copolymers of a hard crystalline segment of polybutylene terephthalate and a second segment of a soft (amorphous) polyether glycols. Such polyester elastomers are sold by Du Pont Chemical Company under the trade name HYTREL®.

Suitable polyamides include those that result from a ring-opening reaction of lactams having from 4-12 carbons. This group of polyamides therefore includes nylon 6, nylon 10 and nylon 12. Acceptable polyamides also include aliphatic polyamides resulting from the condensation reaction of di-amines having a carbon number within a range of 2-13, aliphatic polyamides resulting from a condensation reaction of di-acids having a carbon number within a range of 2-13, polyamides resulting from the condensation reaction of dimer fatty acids, and amide containing copolymers. Thus, suitable aliphatic polyamides include, for example, nylon 66, nylon 6,10 and dimer fatty acid polyamides.

In a preferred from of the invention, the cassette 160 is fabricated from a material that is adhesively compatible with the upper and lower membrane 162, 164. What is meant by adhesive compatibility is the membrane can be attached to the cassette using standard heat sealing techniques. One particularly suitable material is a polymer blend of a polyolefin and a styrene and hydrocarbon copolymer. More particularly, the polyolefin of the polymer blend is a polypropylene and even more preferably a polypropylene copolymer with ethylene with an ethylene content of from about 1% to about 6% by weight of the copolymer. The styrene and hydrocarbon copolymer is more preferably an SEBS tri-block copolymer as defined above. The polypropylene copolymer should constitute from about 70% to about 95% and more preferably from about 80% to about 90% of the blend, and the SEBS will constitute from about 5% to about 30% and more preferably from about 10% to about 20% SEBS. In a preferred form of the invention, the polypropylene used to fabricate the cassette will have a lower melting point temperature than the high melt strength polypropylene used to fabricate the membrane. In a preferred form of the invention the polypropylene of the cassette 160 will have a melting point temperature of from about 120° C.-140° C. and for the film from about 145° C.-160° C. The cassette 160 can be injection molded from these polymer blends.

The upper and lower membranes 162, 164 are attached to the cassette 160 utilizing heat sealing techniques. The film has a peel strength of greater than 5.0 lbf/inch when tested with a tensile instrument until film failure or bond failure. Also, when the film is attached to the cassette it can be deformed under a pressure of 5 psi. The film maintains its low modulus and deformability properties even after sterilization to continue to meet the pumping requirement. The film has an extended shelf life. The film retains its pumping abilities even after two years shelf storage.

IV. Valve Actuator

Referring now to FIG. 15, one embodiment of an interface between the valve actuator 26 and the valve manifold 190 is illustrated. The valve motor 28 (not illustrated) of the valve actuator 26 drives a camshaft 200 through a mechanical linkage determinable to those of skill in the art. In an embodiment, a single camshaft 200 attaches to a series of cams 202, for example, one of each of the valves in the system 10 or 100. The cams 202 are fixed to the camshaft 200 and rotate in a one to one relationship with same.

The cams 202 drive pistons 204, which engage in a friction reduced way with the cams, for example, via rollers 206. The cams 202 drive pistons 204 up and down (only two of five cams shown having associated pistons to show other features of the actuator 26). When a cam 202 drives its associated piston 204 upward, the piston 204 engages one of the membranes 162 or 164 (typically the lower membrane 164, which is not shown in FIG. 15 for clarity) and pushes the membrane up into the respective hole 192 defined by the rigid manifold 190. This action stops the flow of medical fluid or dialysate through the respective valve.

The pistons 204 are also spring-loaded inside a respective housing 208. When the camshaft 200 turns so that a lower cam profile appears below one of the pistons 204, the spring inside the housing 208 pushes the piston 204 so that the roller 206 maintains contact with the respective cam 202. The piston 204 consequently moves away from the respective hole 192 defined by the rigid manifold 190, wherein the membrane 162 or 164, which has been stretched upward by the piston 204, springs back to its normal shape. This action starts the flow of medical fluid or dialysate through the respective valve.

The motor 28 is of a type, for example a stepper or servo motor, that can rotate a fraction of a rotation and stop and dwell for any predetermined period of time. Thus, the motor 28 can hold a valve open or closed for as long as necessary. The cams 202 are shaped to provide a unique combination of bumps and valleys for every flow situation. In certain situations, such as with valves V2 and V3 of the system 10, the valves always open and close together, so that both valves use the same cam 202 oriented in the same way on camshaft 200.

Referring now to FIGS. 16A and 16B, the camshaft 200 and cams 202 are illustrated figuratively. FIG. 16A illustrates a composite cam profile 370, i.e., a combination of each of the cams 202a to 202f illustrated in FIG. 16B. FIG. 16B illustrates that the cams 202a to 202f mount to the camshaft 200 via hubs 384. The hubs 384 may employ set screens as is well known. camshaft 200 can also have indentations, etc. for aligning the hubs 384. In an alternative embodiment, one or more of the cams 202a to 202f may be integrally formed with the otherwise camshaft 200. In an embodiment, the camshaft 200 is a single molded piece, which prevents the cams 202a to 202f from rotating with respect to one another. The single molded camshaft 200 supports or attaches to a plurality of or to all of the cams 202a to 202f.

As illustrated above in FIG. 15, each of the cams 202a to 202f of FIG. 16B drives a single piston 204 and roller 206 to operate a single valve head 192 of the rigid manifold 190. The cams 202a to 202f open or occlude the valve heads 192 according to the shape of the respective cam. FIG. 16B illustrates that the camshaft 200 supports six cams 202c to 202f. FIG. 15 illustrates five cams 200. The cam provided in the embodiment of FIG. 16B may be to open a last bag, illustrated by the "last bag valve open" position 382. Either of the systems 10 or 100 may include a last bag. The last bag is a final dialysate fill of about two liters into the patient before the patient disconnects from the system and resumes normal daily activities.

The valve motor 28 and the valve actuator 26 (FIGS. 1 and 2) rotate the camshaft 200 to open or close the valve heads 192 to create a desired solution flow path. The arrangement of the cams 202a to 202f on the camshaft 200 is made such that, at any time during the therapy, there is no more than one fluid path open at any given time. Further, when the valve actuator 26 rotates the camshaft 200 from one flow path open position to the next, the series of cams 202a to 202f close all the valves for a moment of time. The closing of each of the valves prevents dialysate from back-flowing or moving in the wrong direction. Still further, the cams 202a to 202f are arranged such that only one valve head 192 of the valve manifold 190 of the disposable unit 160 may be open at any given time. Therefore, there is no open fluid path in the event of a system failure or inadvertent power down. This safety feature prevents dialysate from free-flowing into the patient 12 or overfilling the patient 12.

The lid 116 for the housing 112 of the hardware unit 110 may be freely opened by an operator or patient to load the disposable unit 160 into the hardware unit. When this occurs, the controller 30 automatically commands the camshaft to rotate so that an "all valves open" position 372, illustrated by the composite profile 370, resides beneath the rollers 206 and pistons 204. In the "all valves open" position 372, the camshaft 200 is rotated such that a depression exists under each of the pistons 204 and associated rollers 206. Accordingly, the pistons 204 sit in a relatively low position, i.e., out of the way, when the operator or patient loads the disposable unit 160 and valve manifold 190 into the hardware unit 110. This enables the patient or operator to place a disposable unit 160 into the unit 110 without encountering an obstruction or opposing force by one or more of the pistons 206.

After the patient or operator loads the disposable unit into the hardware unit 110 and closes the lid 116, the controller 30 automatically rotates the camshaft 200 so that an "all valves closed" position 386a resides beneath the pistons 204 and rollers 206. As illustrated, the "all valves closed" position 386a resides adjacent to the "all valves open" position 372. When the camshaft 200 is rotated to the "all valves closed position" 386a, no fluid can flow through the system 10, 100. As the camshaft 200 rotates from the "all valves open" position 372 to the first "all valves closed" position 386a, a mechanical interlock (not illustrated) is moved into the camshaft 200, which prevents the rotation of the camshaft 200 back to the "all valves open" position 372. This prevents uncontrolled flow of the dialysate, which could occur when each of the valve heads 192 is open, in the event that the operator tries to open the lid 116 during therapy.

In an alternative embodiment, an interlock can be provided through software. An encoder provides positional and velocity feedback to the controller 30. The controller 30 therefore knows the position of the cam shaft 200. Thus, the controller 30 is able to prevent the rotation of the camshaft 200 back to the "all valves open" position 372.

When the patient closes lid 116, a second mechanical interlock (not illustrated) locks the lid in place, so that the patient cannot open the lid 116 during therapy. The system 10, 100 senses when the patient has removed the patient fluid line 292 and connector 290 from the transfer set, implanted in the patient 12. Only then will the system 10, 100 allow the patient to open the lid 116. The mechanical interlocks prevent free-filling, overfilling and the patient from tampering with the system while it is running. The valve configuration provides a fail safe system that prevents fluid flow in the event a failure or power down.

In many instances, when the patient begins dialysis therapy, the patient is already full of dialysate. In the illustrated embodiment of FIG. 16A, therefore, the composite profile 370 provides the "all valve open" position 372 next to the "from patient value open" position 374. The "from patient valve open" position resides next to the "drain valve open" position 376. In this manner, upon therapy startup, camshaft 200 is readily positioned to be able to cooperate with the pump 20, 120 to drain spent dialysate from the patient. It should be appreciated that any of the cams 202a to 202f may be the cam that provides the "from patient valve open" position 374, the "drain valve open" position 376, etc.

Between the "from patient valve open" position 374 and the "drain valve open" position 376 resides a second "all valves closed" position 386b. Between each opening of a new valve and closing of a previously opened valve, each the valves is momentarily closed. The controller 30 causes the motor (e.g., a stepper, servo or DC motor) and activator 26 to toggle the camshaft 200 back and forth between the "from patent valve open" position 347, past the "all valves closed" position 386b, to the "drain valve open" position 376. In this manner, the pump 20, 120 is able to sequentially pull apart fluid from the patient 12 and dump it to drain 18.

When the system 10, 100 completes the initial patient drain cycle, the controller 30 causes the motor 28 activator 26 to rotate camshaft 200 past the "all valves closed" position 386 to the "supply valve open position" 378. To fill the patient full of fresh dialysate, the controller 30 causes the camshaft 200 to toggle back and forth between the "supply valve open" position 378 and the to patient valve open position 380, each time passing over the "all valves closed" position 386d. Again, for the drain and fill cycles, only one valve head 192 is open at any given period of time. The toggling always includes an "all valves closed" position between the dosing of one valve head 192 and the opening of another. The single pump sequentially pulls fluid into the disposable unit 160 and pushes fluid from same.

After the initial fill, camshaft 200 is positioned so that the camshaft 200 can once again toggle back and forth between the "from patient valve open" position 374, past the intermediate "all valves closed" position 386b, to the "drain valve open" position 376. When the patient is once again empty, the camshaft 200 is positioned so that the camshaft may be toggled back and forth between the "supply valve open" position 378 and the "to patient valve open" position 380. The system 10, 100 repeats this series of cycles as many times as necessary. Typically, the patient receives approximately 2 to 2.5 liters of dialysate in a single fill cycle. The two supply bags 14 each hold six liters of dialysate in an embodiment. This provides the system 10, 100 with four to six complete fill, dwell and drain cycles, which are provided, for example, through the night while the patient sleeps.

In many instances, the patient will receive a last bag fill at the end of the therapy, which the patient will carry for the day. To perform this procedure, the camshaft 200 toggles back and forth between the "from patient valve open" position 374 to the "drain valve open" position 376 to dump the preceding fill of peritoneal fluid to drain 18. Thereafter, the camshaft 200 is positioned to toggle back and forth between the "last bag valve open" position 382 and the "to patient valve open" position 380. In doing so, the camshaft 200 rotates past one of all valves closed positions, namely, the "all valves closed position" 386e.

To prime the system, the camshaft 200 may be positioned and toggled in a number of different ways. In one embodiment, the camshaft 200 toggles back and forth between the "supply valve open" position 378 and the "drain valve open" position 376, passing over the "all valves closed" position 386c. This toggling in cooperation with the pumping of pump 20 or 120 causes the dialysate to flow from the supply bags 14, through the disposable unit 160, to drain 18. In another embodiment, using the vented tip protector 280 illustrated in connection with the FIGS. 8 to 12, the camshaft 200 toggles back and forth between the "supply valve open" position 378 and the "to patient valve open" position 380. This causes dialysate to flow from the bags 14, through the disposable unit 160, and into the patient fluid line 292 to the end of the vented tip protector 280. When dialysate reaches the hydrophobic membrane 300 of the vented tip protection 28, the pressure in the system 10, 100 rises, wherein a signal is received by the controller 30, which causes the pump 20, 120 to stop pumping and the camshaft 200 to stop toggling.

V. Medical Fluid Pump

A. Pump Hardware and Operation

Referring now to FIGS. 17A and 17B, one embodiment of the pump 20 is illustrated. The lid 116 of the hardware unit 110 defines an upper chamber wall 216. Disposed within the housing 112 of the hardware unit 110 (FIGS. 3A to 4B) is a lower chamber wall 218. The chamber walls 216 and 218 define an internal chamber 210. The chamber 210 can have any desired shape, for instance the clamshell shape as illustrated in FIGS. 17A and 17B.

The lower chamber wall 218 defines or provides a sealed aperture 219 that allows a pump piston 212 to translate back and forth within the chamber 210. The piston 212 is attached to or integrally formed with a piston head 214. The piston head 214 in an embodiment has an outer shape that is similar to or the same as an internal shape of the upper chamber wall 216.

The pump piston 212 connects to or is integrally formed with the linear actuator 24. The linear actuator 24 in an embodiment is a device, such as a ball screw that converts the rotary motion of a motor 22 into the translational motion of the piston 212. In one preferred embodiment, the motor 22 is a linear stepper motor that outputs a translationally moving shaft. Here, the actuator 24 may simply couple the motor shaft to the piston 212. The linear or rotary stepper motor provides quiet linear motion and a very high positional resolution, accuracy and repeatability. Stepper motors are commercially available, for example, from Hayden Switch and Instrument Inc., Waterbury, Conn.

As described above, the flexible fluid receptacle 172 (seen in FIG. 17A but not in FIG. 17B) is defined by the expandable upper and lower membranes 162 and 164, respectively, of the disposable unit 160. In FIG. 17A, when the pump 20 is full of medical fluid, the pump chamber 210 and the membrane receptacle 172 have substantially the same shape. In FIG. 17B, when the pump 20 has displaced all or most all of the medical fluid, the pump chamber 210 maintains the same volume but the membranes 162 and 164 of the fluid receptacle 172 have collapsed to virtually a zero volume along the interior surface of the upper chamber wall 216.

Vacuum source 44 for the pump 20 is described above in connection with FIG. 1. The vacuum source 44 exerts a vacuum on the upper membrane 162, through the aperture or port 222. The aperture or port 222 extends through the upper chamber wall 216. The vacuum source 44 exerts a vacuum on the lower membrane 164, through an aperture 221 defined or provided by housing 223, and through the port or aperture 220. The port or aperture 220 extends through the piston 212, including the piston head 214. When a vacuum is applied, the lower membrane 164 seals against the piston head 214. The upper membrane 162 seals against the upper chamber wall 216.

The port 222 fluidly connects to channels (not illustrated) defined by the interior wall of the upper chamber wall 216. The channels extend radially outwardly from port 222 in various directions. The channels help to distribute the negative pressure applied through the port 222 to further enable the upper membrane 162 to substantially conform to the interior shape of the upper chamber wall 216. In a similar manner, the outer surface of the piston head 214 can include radially extending channels to further enable the lower membrane 164 to substantially conform, upon application of the vacuum, to the outer surface of the piston head 214.

The pump 20 also includes a diaphragm 232 tensioned between the upper and lower chamber walls 216 and 218, respectively. The diaphragm 232 defines, together with the upper chamber wall 218, a known, predictable and repeatable maximum volume of dialysate, which can be drawn from one or more of the supply bags 14 and transported to the patient 12. The diaphragm 232 also enables the volume of a partial stroke to be characterized, which also enables accurate and repeatable volume measurements.

The diaphragm 232 is disposed beneath the piston head 214 and around the piston 212. When the vacuum is applied to the port or aperture 220, the diaphragm 232, as well as the lower membrane 164, are pulled against the piston head 214. When the piston head 214 is actuated upwardly away from the lower chamber wall 218, with the vacuum applied through aperture 220, the membrane 164 and the diaphragm 232 remain drawn to the piston head 214. An inner portion of the membrane 164 conforms to the shape of the outer surface of the piston head 214. The remaining outer portion of the membrane 164 conforms to the shape of the exposed surface of the diaphragm 232.

The diaphragm 232 in an embodiment includes a flexible, molded cup-shaped elastomer and a fabric reinforcement, such as fabric reinforced ethylene propylene diene methylene ("EPDM"). The fabric can be integrally molded with the elastomer. The fabric prevents unwanted deformation of the diaphragm while under pressure. The diaphragm 232 can stretch when the piston 212 and head 214 move downwardly towards the lower chamber wall 218, pulling the diaphragm 232 along the crimped edges of the upper and lower chamber walls 216 and 218. The diaphragm 232 also moves and remains sealed to the piston head 214 when the piston 212 and head 214 move upwardly towards the upper chamber wall 216.

In operating the pump 20, negative pressure is constantly applied through the port 222 to hold the upper membrane 162 against the upper chamber wall 216. The manifold 190 of the disposable unit 160 (see FIGS. 3A and 5) define a fluid port opening 230 to the membrane receptacle 172. The fluid port opening 230 allows medical fluid or dialysate to enter and exit the membrane receptacle 172. The membrane receptacle 172 seats in place with the crimped edges of the upper and lower chamber walls 216 and 218. The seal 170 of the receptacle 172 may actually reside slightly inside the crimped edges of the upper and lower chamber walls 216 and 218 (see FIG. 4A).

During a pump fill stroke, with the upper membrane 162 vacuum-pressed against the upper chamber wall 216, and the lower membrane 164 and the diaphragm 232 vacuum-pressed against the piston head 214, the motor 22/actuator 24 cause the piston head 214 to move downwardly towards the lower chamber wall 218, increasing the volume within the flexible receptacle 172, and producing a negative pressure within same. The negative pressure pulls dialysate from the supply bags 14 or the patient 12 as dictated by the current valve arrangement. The opened receptacle 172 fills with fluid. This process occurs when the pump moves from the position of FIG. 17B to the position of FIG. 17A. FIG. 17A shows the pump 20 at the end of the stroke, with the receptacle 172 fully opened (i.e., full of fluid).

During a patient fill or drain stroke, again with the upper membrane 162 vacuum-pressed against the upper chamber wall 216, and the lower membrane 164 and the diaphragm 232 vacuum-pressed against the piston head 214, the motor 22/actuator 24 cause the piston head 214 to move upwardly towards the upper chamber wall 216, decreasing the volume within the flexible receptacle 172 and producing a positive pressure within same. The positive pressure pushes dialysate from the receptacle 172 to the patient 12 or the drain 18 as dictated by the current valve arrangement. The receptacle 172 closes as the lower membrane 164 moves upward towards the upper membrane 162. This process occurs when the pump moves from the position of FIG. 17A to the position of FIG. 17B. FIG. 17B shows the pump 20 at the end of the stroke, with the receptacle 172 empty or virtually empty.

In the event that air ("air" for purposes of this invention includes air as well as other gases which may be present, particularly those that have escaped from the patient's peritoneal cavity) enters the fluid receptacle 172, it must be purged to maintain accuracy. It should be appreciated that if air enters between the membranes 162 and 164, the presently preferred system 10, 100 does not have the ability to pull a vacuum between the membranes 162 and 164. The elasticity of the membranes 162 and 164, however, naturally tend to purge air therefrom. In an alternative embodiment the system 10,