Patent Description:
Most HD, HF, and HDF treatments occur in centers. A trend towards home hemodialysis ("HHD") exists today in part because HHD can be performed daily, offering therapeutic benefits over in-center hemodialysis treatments, which occur typically bi- or triweekly. Studies have shown that more frequent treatments remove more toxins and waste products and render less interdialytic fluid overload than a patient receiving less frequent but perhaps longer treatments. A patient receiving more frequent treatments does not experience as much of a down cycle (swings in fluids and toxins) as does an in-center patient, who has built-up two or three days' worth of toxins prior to a treatment. In certain areas, the closest dialysis center can be many miles from the patient's home, causing door-to-door treatment time to consume a large portion of the day. Treatments in centers close to the patient's home may also consume a large portion of the patient's day. HHD can take place overnight or during the day while the patient relaxes, works or is otherwise productive.

Another type of kidney failure therapy is peritoneal dialysis ("PD"), which infuses a dialysis solution, also called dialysis fluid, into a patient's peritoneal chamber via a catheter. The dialysis fluid is in contact with the peritoneal membrane in the patient's peritoneal chamber. Waste, toxins and excess water pass from the patient's bloodstream, through the capillaries in the peritoneal membrane, and into the dialysis fluid due to diffusion and osmosis, i.e., an osmotic gradient occurs across the membrane. An osmotic agent in the PD dialysis fluid provides the osmotic gradient. Used or spent dialysis fluid is drained from the patient, removing waste, toxins and excess water from the patient. This cycle is repeated, e.g., multiple times.

There are various types of peritoneal dialysis therapies, including continuous ambulatory peritoneal dialysis ("CAPD"), automated peritoneal dialysis ("APD"), tidal flow dialysis and continuous flow peritoneal dialysis ("CFPD"). CAPD is a manual dialysis treatment. Here, the patient manually connects an implanted catheter to a drain to allow used or spent dialysis fluid to drain from the peritoneal chamber. The patient then switches fluid communication so that the patient catheter communicates with a bag of fresh dialysis fluid to infuse the fresh dialysis fluid through the catheter and into the patient. The patient disconnects the catheter from the fresh dialysis fluid bag and allows the dialysis fluid to dwell within the peritoneal chamber, wherein the transfer of waste, toxins and excess water takes place. After a dwell period, the patient repeats the manual dialysis procedure, for example, four times per day. Manual peritoneal dialysis requires a significant amount of time and effort from the patient, leaving ample room for improvement.

Automated peritoneal dialysis ("APD") is similar to CAPD in that the dialysis treatment includes drain, fill and dwell cycles. APD machines, however, perform the cycles automatically, typically while the patient sleeps. APD machines free patients from having to manually perform the treatment cycles and from having to transport supplies during the day. APD machines connect fluidly to an implanted catheter, to a source or bag of fresh dialysis fluid and to a fluid drain. APD machines pump fresh dialysis fluid from a dialysis fluid source, through the catheter and into the patient's peritoneal chamber. APD machines also allow for the dialysis fluid to dwell within the chamber and for the transfer of waste, toxins and excess water to take place. The source may include multiple liters of dialysis fluid including several solution bags.

APD machines pump used or spent dialysate from the peritoneal chamber, though the catheter, and to the drain. As with the manual process, several drain, fill and dwell cycles occur during dialysis. A "last fill" may occur at the end of the APD treatment. The last fill fluid may remain in the peritoneal chamber of the patient until the start of the next treatment, or may be manually emptied at some point during the day.

In any of the above modalities using an automated machine, the automated machine operates typically with a disposable set, which is discarded after a single use. Depending upon the complexity of the disposable set, the cost of using one set per day may become significant. Also, daily disposables require space for storage, which can become a nuisance for home owners and businesses. Moreover, daily disposable replacement requires daily setup time and effort by the patient or caregiver at home or at a clinic.

There is also a need for APD devices to be portable so that a patient may bring his or her device on vacation or for work travel.

For each of the above reasons, it is desirable to provide a relatively simple, compact APD machine, which operates a simple and cost effective disposable set.

<CIT> discloses an automatic apparatus for peritoneal dialysis, wherein the automatic control of the circulating mechanisms of the dialysis solution is obtained on the basis of measures of volume of a dilatable body or element of the dialysis circuit. The control means simultaneously provide the damping of the pulsations of the pump in the dialysis circuit and the compensation of disturbing overpressures such as those which for instance are generated by fits of coughing of the patient.

<CIT> discloses an automatic peritoneal dialyzer that while preventing any catheter clogging and restricting the remainder of trapped fluid in the abdominal cavity, can carry out patient drainage processing relatively rapidly; and a method of drainage control therefor.

<CIT> discloses fluid volume measurement systems for a pneumatically actuated diaphragm pump in general, and a peritoneal dialysis cycler using a pump cassette in particular. Pump fluid volume measurements are based on pressure measurements in a pump control chamber and a reference chamber in a two-chamber model, with different sections of the apparatus being modelled using a combination of adiabatic, isothermal and polytropic processes. Real time or instantaneous fluid flow measurements in a pump chamber of a diaphragm pump are also disclosed, in this case using a one-chamber ideal gas model and using a high speed processor to obtain and process pump control chamber pressures during fluid flow into or out of the pump chamber.

<CIT> discloses a pumping system for producing a volume flow of dialysis solution in a dialysis machine, the pumping system comprising at least one piston pump, the piston of which co-operates with a working fluid which in turn exerts a force on a conveyor means, in particular a membrane. Adjustment means are provided, by which the conveying volume of the piston pump per piston stroke can be reduced. The adjustment means comprise a mechanical piston stop, which can be varied in position, for reducing the piston stroke and/or means for reducing the amount of the working medium and/or means for reducing the volume of the conveying chamber which co-operates with the conveying means and contains the dialysis solution to be conveyed.

The present disclosure relates to an automated peritoneal dialysis ("APD") system, which uses a bellows pump. In general, the APD system employs an APD machine or cycler that operates a disposable set. In one embodiment, the disposable set includes at least one bellows, which is expanded to perform a draw or fill stroke and is compressed to perform an expel or pump-out stroke. The bellows connects to a common input/output line that feeds fluid into the bellows and accepts fluid from the bellows. The common input/output line feeds or splits into multiple, e.g., five, separate lines, each interfacing with a valve, such as an electrically actuated solenoid valve, a motorized pinch valve, or a pneumatically actuated valve. The separate lines include a fresh dialysis fluid line that extends to a fresh dialysis fluid supply or bag, a last fill fluid line that extends to a last dialysis fluid supply or bag, a patient line that carries fresh, heated dialysis to a patient and used dialysis fluid from the patient, a drain line that extends to a drain container, e.g., bag, or to a house drain such as a toilet or bathtub, and a heater line that carries fresh dialysis fluid to a heater disposable, such as a container or bag having serpentine heating pathway.

The bellows in an embodiment has an accordion or concertina shape and may be made of a disposable plastic, such as polyvinyl chloride ("PVC"), polyethylene ("PE"), polyurethane ("PU"), polypropylene ("PP"), polycarbonate or other generally soft plastic material. One possible bellows driving structure includes a motor that rotates a shaft to which a gear is connected, in which the gear forms the pinion of a rack and pinion type of linear actuator. The rotational motion of the motor shaft is converted into translational motion by the rack and pinion. The translational motion of the rack and pinion causes expansion and compression of the bellows depending on the direction of motor rotation. A slide potentiometer may be provided to monitor the positon and movement of the bellows. Alternatively, the motor is fitted with a motor encoder, which detects the rotational position of the motor shaft, which can be converted into a distance moved by the rack and pinion and thus the bellows by knowing how much the rack moves per rotation, or partial rotation, of the motor shaft and pinion gear.

Other forms of linear actuation may be used, such as a motor and lead or ball screw, a linear motor or a pneumatic cylinder. Each linear actuator is able to expand and compress the bellows.

Volumetric accuracy for the APD system is determined in one embodiment by knowing the internal volume of the bellows and by detecting how much the bellows has been moved. Volumetric accuracy also assumes the bellows to be completely full of fluid and thus fully primed with air. If needed, the bellows may be fitted with one or more hydrophobic membrane to help "squeeze" the air out of the bellows during operation. A priming sequence for the bellows APD system is described below.

It is contemplated to include a set of two bellows that are operated in an alternating manner to provide a more continuous flow and to increase flowrate. In an embodiment, the linear actuator, e.g., motor operably coupled to a rack and pinion, is connected to the bellows at a location at which the two bellows are connected together, so that the linear actuator in (i) a first stroke moves in a first direction to expand a first bellows to draw fluid in and compress the second bellows to pump fluid out and (ii) a second stroke moves in a second direction to expand the second bellows to draw fluid in and compress first bellows to pump fluid out. The result is a more continuous flow and an increased flowrate using the same linear actuator as for the single bellows embodiment. The trade-off is (i) the additional disposable cost of the second bellows and a second set of lines to each of the sources and destinations and (ii) the additional cost and complexity of a second set of valves and their control of the second set of lines.

As mentioned above, it is important to prime the bellows APD system for volumetric accuracy and to prevent the delivery of air to the patient. It is contemplated to allow the bellows to be tipped during priming either in a motorized way or manually, so that air migrates towards the inlet/outlet of the bellows for removal to the drain line. Alternatively or additionally, the bellows may be fitted with one or more hydrophobic membrane that aids air in escaping the bellows during priming.

Further alternatively or additionally, in one priming sequence under control of the control unit of the present APD system, the single or dual bellows pump is caused to first prime the supply line. If the volume of a single stroke of the bellows pump is less than that of the supply line, then it is contemplated to open the supply line valve on the draw stroke of the bellows pump, and then to close that valve and open the drain valve to push air in the subsequent pump-out stroke of the bellows to drain. The above sequence is repeated until the supply line is fully primed, which may be detected by a sensor located at the common input/output line, or determined empirically to require a certain amount of pump strokes.

The priming operation of the supply line is then repeated for all supply lines and the last bag line. With the supply and last bag lines primed, fresh dialysis fluid is then used to prime the patient line up to a patient connector, which may be set at a certain height or the patient connector may be placed next to a sensor that determines when the patient line is fully primed. The heater line is then primed at least up to its interaction with a heater valve. The drain line may or may not be primed, e.g., may be primed up to a drain line valve.

The single or dual bellows APD system of the present disclosure contemplates different solutions for ensuring that the motorized bellows does not create too much positive or negative fluid pumping pressure when delivering fresh dialysis to or removing used dialysis fluid from the patient. Generally, it is desirable to limit patient pumping pressure for peritoneal dialysis to -<NUM> psig for effluent removal and from +<NUM> psig to <NUM> psig for fresh dialysis fluid delivery to the patient. Pumping from other sources or to other destinations may be performed at higher pressures.

A first pressure control solution is to select a motor that is incapable of supplying (or is controlled not to supply) a positive or negative overpressure. The pressure that fluid is delivered to and removed from the patient is a function of the force exerted by the linear actuator and the geometry of the bellows and tubing. The maximum positive and negative patient pumping pressures are known (listed above) as is the geometry of the bellows and tubing. From these values, the maximum allowable force due to the linear actuator is able to be calculated. Discussed herein is the determination of a relationship between output force of the linear actuator, e.g., the rack and pinion configuration and the motor torque outputted by the motor. Thus after calculating the maximum allowable force due to the linear actuator, the maximum allowable motor torque may be calculated. A single speed motor having a set torque at or below the maximum is then selected. Or, a variable speed motor is selected and a low speed limit is set for patient pumping (motor torque has an inverse relationship with motor speed). A control unit of the APD system of the present disclosure either causes the single speed motor to be powered or maintains the low speed limit for the variable speed motor for patient pumping (limit may not apply for pumping to or from other destinations or sources).

A second pressure control solution contemplated for the bellows APD system of the present disclosure is to place a force sensor (load cell or strain gauge) in contact with the bellows. Here, instead of calculating a maximum allowable motor torque for patient pumping, the actual force due to the linear actuator is measured. The measurement may be used as feedback to the control unit of APD system, which causes the speed of the motor to be varied to ensure that the resulting force due to the linear actuator is at or below the maximum allowable force. The maximum allowable force due to the linear actuator is calculated again knowing the maximum allowable positive and negative patient pumping pressures and the geometry of the bellows and tubing. To reduce noise leading to error, such as force to torque conversion, current to torque conversion and current sensing error, it is contemplated to locate the force sensor close the item to be sensed, namely, the bellows. Doing so reduces or eliminates these errors.

A third pressure control solution contemplated for the bellows APD system of the present disclosure is to add a pressure sensing module or pod that measures fluid pressure directly and obviates the need to know the bellows and tubing geometry and the need to determine maximum allowable forces. The pod may have a membrane that separates a fluid pumping side of the pod from an air transducer sensing side of the pod. The flexibility of the membrane allows the pressure on either side of the membrane to equilibrate, such that the pressure of any of the different fluids discussed herein equals the sensed air pressure. A pressure transducer is provided and measures the pressure of air or other transmission fluid, which equals that of the PD or patient fluid. The pressure signal is used as feedback to the control unit to vary the speed of the bellows motor to make sure that the resulting positive or negative fluid pressure does not exceed an allowable limit.

In an alternative embodiment, the pressure "pod" is made to be very small, e.g., to be a dome that covers a pressure sensing area or diaphragm located along a tube. The dome and diaphragm may be welded to the tube, e.g., via ultrasonic welding, heat sealing or solvent bonding, so that the dome and diaphragm cover a pressure sensing hole in the tube. The dome communicates pneumatically with a pressure transducer in the same manner described herein for the pressure pod embodiments.

It is contemplated to provide a diaphragm positioning apparatus and method that may be used with any of the pressure sensing embodiments of the bellows APD system of the present disclosure, including the direct tube pressure sensing embodiment. The positioning apparatus includes the pod or dome and its associated diaphragm, the pressure transducer and an additional vent valve. During a time in which the cycler is not pumping fluid, the diaphragm is pressurized with a liquid so as to be located at a starting position. The cycler then attempts to pump over a full range of positive and negative pressures to see if the starting position of the diaphragm allows for a pressure to be sensed over the full desired pressure range. If so, then that initial diaphragm starting position is noted and used going forward. If not, and the diaphragm during the test instead reaches a positive or negative elastic limit and no longer senses properly in that positive or negative direction, the cycler opens the vent and starts over. Upon the start over, the cycler places the diaphragm at a new starting position that attempts to correct against the direction in which the prior positive or negative failure occurred. If an elastic limit is reached again, the vent valve is reopened and the above process is repeated until a suitable starting location for the diaphragm is found.

For any of the pressure sensing versions of the bellows APD system of the present disclosure, it is contemplated to provide a calibration routine that determines the actual volumetric output of the bellows. Doing so allows for the manufacturing tolerances of the bellows to be relaxed, lowering disposable cost. For the calibration routine, the pneumatic transmission line extending from the pressure pod to the pressure transducer (and to the vent valve if provided for the pressure diaphragm starting location procedure) also extends to a known volume cylinder. A piston is located within the cylinder and is driven by a linear actuator, such as a rotating nut motor that turns a ball or lead screw. The linear actuator in one embodiment provides a piston rod for driving a piston head that is moveably sealed within the cylinder. A position sensing device, such as an encoder or potentiometer, is provided to accurately detect a position of the piston head within the cylinder.

In the calibration routine, the bellows is moved a known distance to displace fluid into the pressure pod. All downstream fluid valves are closed so pressure builds from an initial pressure to an increased pressure. Next, the piston is retracted within the cylinder so that the pneumatic pressure as measured by the pressure transducer is lowered from the increased pressure to the initial pressure. Because the initial and final pressures are equal, the volume as defined by the inner diameter cross-sectional area of the cylinder multiplied by the distance that the piston head is moved to reach the initial pressure equals the volume of fluid delivered from the bellows to the pressure pod. The control unit records the actual volume of dialysis fluid delivered over the first moved distance of the bellows.

With the bellows maintained at the first moved distance, at least a portion of the fluid in the pressure pod is removed to drain via the piston and cylinder. The above-described procedure is then repeated, moving the bellows from the first moved distance to a second moved distance. The control unit records the actual volume of dialysis fluid delivered by the bellows over the second moved distance. The first and second moved distances may be the same or different. When the bellows is finally moved a full stroke, the control unit adds all the incremental volumes to determine a total actual stroke volume for the bellows. The control unit thereafter has a map for the particular bellows that provides actual stroke volumes for partial and full strokes. It is contemplated to perform the calibration routine at the beginning of each treatment, so that a custom volume delivery profile can be developed for each bellows disposable set, allowing for wider tolerances in the production of the bellows.

In a further alternative bellows APD system of the present disclosure, pressure is still controlled directly but the pressure pods or domes are eliminated, which simplifies the disposable and lowers its cost. Here, an incompressible fluid column is located between the linear actuator and the bellows. The incompressible fluid column is located within a chamber and contacts a slidingly sealed piston, e.g., o-ring sealed to the chamber. The piston is coupled mechanically to the bellows. The linear actuator translates the chamber so that the incompressible fluid (e.g., water or oil) is compressed between the chamber and the piston. The incompressible fluid is in fluid communication with a liquid or fluid pressure transducer, which outputs to a control unit. The control unit uses the sensed pressure as feedback to control the actual pressure to meet a commanded pressure.

In an embodiment, the inner diameter of the incompressible fluid chamber (the outer diameter of the incompressible fluid column) is made to be the same as the effective pumping diameter of the bellows. In this way, the pressure applied by the linear actuator to the incompressible fluid is the same as the pressure applied by the bellows to the fresh or used PD fluid. Thus controlling the pressure of the incompressible fluid also controls the pressure of the dialysis fluid. In an alternative implementation, two or more incompressible fluid columns are provided, each sensed by a liquid or fluid pressure sensor, for redundancy and accuracy.

According to a first aspect of the present invention, there is provided a peritoneal dialysis system comprising: a bellows; a common inlet/outlet fluid receptacle in fluid communication with the bellows; a plurality of fluid lines in fluid communication with the common inlet/outlet receptacle; a linear actuator positioned and arranged to expand and compress the bellows; a plurality of valves positioned and arranged to allow or occlude flow through the plurality of fluid lines to or from the bellows; and a control unit configured to control the linear actuator and the plurality of valves.

In a first embodiment of the peritoneal dialysis system of the first aspect of the present invention, the peritoneal dialysis system includes at least one means for limiting the pressure of fluid pulled into or pushed out of the bellows.

In a second embodiment of the peritoneal dialysis system of the first aspect of the present invention, which may also be combined with the first embodiment, the plurality of fluid lines includes at least one of a fresh dialysis fluid line, a heater line, a patient line or a drain line.

In a third embodiment of the peritoneal dialysis system of the first aspect of the present invention, which may be combined with the second embodiment, the peritoneal dialysis system includes at least one of a fresh dialysis fluid container in fluid communication with the at least one fresh dialysis fluid line, a heating container in fluid communication with the heater line, or a drain container in fluid communication with the drain line.

In a fourth embodiment of the peritoneal dialysis system of the first aspect of the present invention, which may also be combined with any one of the first to third embodiments, the common inlet/outlet fluid receptacle includes a common inlet/outlet fluid line or a pressure pod.

In a fifth embodiment of the peritoneal dialysis system of the first aspect of the present invention, which may also be combined with any one of the first to fourth embodiments, the linear actuator includes a motor in operable communication with a rack and pinion, the rack positioned and arranged to expand and compress the bellows.

In a sixth embodiment of the peritoneal dialysis system of the first aspect of the present invention, which may also be combined with any one of the first to fifth embodiments, the peritoneal dialysis system includes a positional feedback device outputting to the control unit to enable the control unit to determine a current position of the bellows.

In a seventh embodiment of the peritoneal dialysis system of the first aspect of the present invention, the positional feedback device of the sixth embodiment includes a potentiometer or a motor encoder.

In an eighth embodiment of the peritoneal dialysis system of the first aspect of the present invention, which may be combined with the sixth or seventh embodiment, the control unit is configured to use the current position of the bellows to determine at least one of (i) a volume of fluid moved into or out of the bellows or (ii) a flowrate of fluid moved into or out of the bellows.

In a ninth embodiment of the peritoneal dialysis system of the first aspect of the present invention, which may also be combined with any one of the first to eighth embodiments, the control unit is configured to perform a priming sequence in which fluid is pulled through a first one of the fluid lines when the bellows is expanded and air is pushed out a second one of the fluid lines when the bellows is compressed.

In a tenth embodiment of the peritoneal dialysis system of the first aspect of the present invention, which may also be combined with any one of the first to ninth embodiments, the bellows is a first bellows, and the system includes a second bellows positioned and arranged such that the first bellows is expanded while the second bellows is compressed and the first bellows is compressed while the second bellows is expanded.

In an eleventh embodiment of the peritoneal dialysis system of the first aspect of the present invention, which may be combined with the tenth embodiment, the linear actuator is positioned and arranged to expand and compress the first and second bellows.

In a twelfth embodiment of the peritoneal dialysis system of the first aspect of the present invention, which may be combined with the tenth or eleventh embodiment, the common inlet/outlet receptacle is a first common inlet/outlet receptacle and the system includes a second common inlet/outlet receptacle in fluid communication with the second bellows.

According to a second aspect of the present invention, there is provided a peritoneal dialysis system comprising: a bellows; a plurality of fluid lines in fluid communication with the bellows; a plurality of valves positioned and arranged to allow or occlude flow through the plurality of fluid lines to or from the bellows; a linear actuator positioned and arranged to expand and compress the bellows, the linear actuator including a motor; and a control unit configured to control the motor of the linear actuator and the plurality of valves, wherein (i) the motor is selected so as to be incapable of causing fluid moved by the linear actuator to exceed a pressure limit or (ii) the control unit is configured to control the motor to ensure that fluid moved by the linear actuator is within the pressure limit.

In a first embodiment of the peritoneal dialysis system of the second aspect of the present invention, control of the linear actuator is based on a mathematical relationship involving the linear actuator and the motor.

According to a third aspect of the present invention, there is provided a peritoneal dialysis system comprising: a bellows; a linear actuator positioned and arranged to expand and compress the bellows; a force sensor in operable communication with the bellows and the linear actuator; and a control unit configured to control the linear actuator based on an output from the force sensor to ensure that fluid moved by the bellows is within a pressure limit.

In a first embodiment of the peritoneal dialysis system of the third aspect of the present invention, control of the linear actuator is based on a maximum allowable force determined knowing the pressure limit and at least one geometrical dimension associated with the bellows.

In a second embodiment of the peritoneal dialysis system of the third aspect of the present invention, which may also be combined with the first embodiment, the force sensor is located at a contact point between the bellows and the linear actuator.

According to a fourth aspect of the present invention, there is provided a peritoneal dialysis system comprising: a bellows; a linear actuator positioned and arranged to expand and compress the bellows; a pressure sensor in fluid communication with the bellows; and a control unit configured to control the linear actuator based on an output from the pressure sensor to ensure that fluid moved by the bellows is within a pressure limit.

In a first embodiment of the peritoneal dialysis system of the fourth aspect of the present invention, the pressure sensor includes a diaphragm separating a first side of the pressure sensor in fluid communication with the bellows from a second side in operable communication with a pressure transducer.

In a second embodiment of the peritoneal dialysis system of the fourth aspect of the present invention, which may be combined with the first embodiment, the control unit is further configured to (i) cause the diaphragm to be moved to a starting position, (ii) actuate the linear actuator to cause the bellows to pump over a full range of positive and negative pressures and determine if the diaphragm flexes over the full range, (iii) if the diaphragm flexes over the full range, use the starting position for the diaphragm for treatment, and (iv) if the diaphragm does not flex over the full range, repeat (i) to (iv) moving the diaphragm to a different starting position.

In a third embodiment of the peritoneal dialysis system of the fourth aspect of the present invention, which may be combined with the first or second embodiment, the diaphragm is part of a tube in fluid communication with the bellows.

According to a fifth aspect of the present invention, there is provided a peritoneal dialysis system comprising: a bellows; a piston in mechanical communication with the bellows; a chamber, the piston in moveably sealed communication with the chamber, the chamber and the piston holding an incompressible fluid; a pressure sensor in operable communication with the incompressible fluid; and a linear actuator positioned and arranged to move the chamber and the bellows; and a control unit configured to use feedback from the pressure sensor to attempt to control the linear actuator so that a pressure of a fluid delivered or removed by the bellows meets a commanded pressure.

In a first embodiment of the peritoneal dialysis system of the fifth aspect of the present invention, the chamber holds a plurality of incompressible fluid columns in fluid communication with at least one pressure sensor.

It is accordingly an advantage of the present disclosure to provide a relatively volumetrically accurate automated peritoneal dialysis ("APD") cycler.

It is another advantage of the present disclosure to provide an APD cycler that achieves relatively precise pressure control.

It is a further advantage of the present disclosure to provide a relatively quiet APD cycler.

It is yet a further advantage of the present disclosure to provide a relatively simple and low cost APD cycler.

It is yet another advantage of the present disclosure to provide a relatively simple disposable set.

Referring now to the drawings and in particular to <FIG>, an automated peritoneal dialysis ("APD") system <NUM> includes and APD machine or cycler <NUM> that operates with a disposable set <NUM> having a bellows <NUM>. APD machine or cycler <NUM> includes a housing <NUM> that houses or includes a linear actuator <NUM>. One possible linear actuator <NUM> for driving bellows <NUM> includes a motor <NUM> that rotates its shaft to which a gear <NUM> is connected. Gear <NUM> forms the pinion that operates with a rack <NUM> of a rack and pinion having mating gear teeth <NUM>. Motor <NUM> may be a stepper motor, brushed DC motor or brushless DC motor, for example. Certain types of motors <NUM>, e.g., brushed DC motors, may be provided with a gearbox to lower its output speed.

In the illustrated embodiment, the rotational motion of the motor shaft is converted into translational motion by the rack <NUM> and pinion <NUM>. Rack <NUM> is in direct or indirect mechanical communication with a moving end 102a of bellows <NUM>, in the illustrated embodiment via a driver arm <NUM>. End 102b of bellows <NUM> is fixed in <FIG>. The translational motion of rack <NUM> and pinion <NUM> therefore causes expansion and compression of bellows <NUM> depending on the direction of rotation of the motor shaft of motor <NUM>. In the illustrated embodiment, bellows <NUM> is fully expanded. To compress bellows <NUM>, motor <NUM> causes pinion <NUM> to spin clockwise, which in turn causes rack <NUM> to move to the left and bellows <NUM> to compress accordingly. To expand bellows <NUM>, motor <NUM> causes pinion <NUM> to spin counterclockwise, which in turn causes rack <NUM> to move to the right and bellows <NUM> to expand accordingly.

Other forms of linear actuation for system <NUM> may be used, such as (i) a motor coupled to a lead screw, ball screw, or high helix lead screw, (ii) a linear motor or (iii) a pneumatic cylinder. Each linear actuator <NUM> directly or indirectly contacts bellows <NUM> for its expansion and compression.

In the illustrated embodiment, linear actuator <NUM> operates with a slide potentiometer <NUM>, which monitors the position and movement of bellows <NUM>. Alternative positional feedback devices are contemplated, e.g., motor <NUM> may be fitted with a motor encoder (not illustrated), which detects the rotational position of the motor shaft, which can be converted into a distance moved by rack <NUM> and pinion <NUM>, and thus the distance moved by bellows <NUM>, by knowing how much rack <NUM> moves per rotation, or partial rotation, of the shaft of motor <NUM> and pinion <NUM>.

Volumetric accuracy for the APD system is determined in one embodiment by knowing the internal volume of bellows <NUM> and by detecting how much the bellows has been moved via one of the positional feedback devices described above. Volumetric accuracy also assumes the bellows to be completely full of fluid and thus fully primed. If needed, bellows <NUM> may be fitted with one or more hydrophobic membrane <NUM> to help "squeeze" the air out of the bellows during operation. Priming techniques for bellows APD system <NUM> are described below.

As discussed, disposable set <NUM> includes at least one bellows <NUM>, which is expanded to perform a draw or fill stroke and is compressed to perform an expel or pump-out stroke. As illustrated in <FIG>, bellows <NUM> connects to or is in fluid communication with a common input/output line <NUM> that feeds fluid into bellows <NUM> and accepts fluid from bellows <NUM>. Common input/output line <NUM> feeds or splits into multiple, e.g., five, separate lines, each interfacing with a valve, such as an electrically actuated solenoid valve or a pneumatically actuated valve. In the illustrated embodiment, the separate lines include a fresh dialysis fluid line <NUM> that extends to a fresh dialysis fluid supply or bag <NUM>, a last fill fluid line <NUM> that extends to a last dialysis fluid supply or bag <NUM>, a patient line <NUM> that carries fresh, heated dialysis fluid to a patient and used dialysis fluid from the patient via a patient connector <NUM> connected to the patient's transfer set (not illustrated), a drain line <NUM> that extends to a drain container <NUM>, e.g., bag, or to a house drain such as a toilet or bathtub, and a heater line <NUM> that carries fresh dialysis fluid to a heater disposable <NUM>, such as a container or bag having serpentine heating pathway <NUM>.

In the illustrated embodiment, heater disposable <NUM> is heated by a heater <NUM> provided by APD machine or cycler <NUM>. Heater <NUM> may be a batch or inline heater. For example, heater <NUM> may be a resistive plate heater, wherein heater disposable <NUM> is correspondingly either a batch or inline disposable. APD machine or cycler <NUM> further provides a valve 44a operable to selectively open and close fresh dialysis fluid line <NUM>, a valve 44b operable to selectively open and close last fill fluid line <NUM>, a valve 44c operable to selectively open and close patient line <NUM>, a valve 44d operable to selectively open and close drain line <NUM>, and a valve 44e operable to selectively open and close heater line <NUM>. Valves 44a to 44e may be electrically actuated solenoid valves that are energized open and spring closed to be fail safe. Valves 44a to 44e may alternatively be pneumatically actuated.

Bellows <NUM> in the illustrated embodiment has in an embodiment has an accordion or concertina shape and may be made of a disposable plastic, such as polyvinyl chloride ("PVC"), polyethylene ("PE"), polyurethane ("PU") or polycarbonate. In an embodiment, the remainder of disposable set <NUM>, including each of the lines and containers listed above, may be made of PVC or a medically approved non-PVC material.

In the illustrated embodiment of <FIG>, APD machine or cycler <NUM> of system <NUM> includes a control unit <NUM>. Control unit <NUM> is alternatively provided as a wireless user interface, such as a tablet or smartphone. In any case, as illustrated in <FIG>, control unit <NUM> may include one or more processor <NUM>, one or more memory <NUM>, and a video controller <NUM> interfacing with a user interface <NUM>, which may include a display screen operating with a touchscreen and/or one or more electromechanical button, such as a membrane switch. User interface <NUM> may also include one or more speaker for outputting alarms, alerts and/or voice guidance commands. Control unit <NUM> may also include a transceiver and a wired or wireless connection to a network, e.g., the internet, for sending treatment data to and receiving prescription instructions from a doctor's or clinician's server interfacing with a doctor's or clinician's computer.

Each of motor <NUM>, potentiometer <NUM> (or encoder), heater <NUM> and valves 44a to 44e are under control of and/or output to control unit <NUM>. Control unit <NUM> executes a treatment program or prescription prescribed by a doctor or clinician to perform the bellows and valve sequences described herein.

Referring now to <FIG>, in an alternative embodiment for system <NUM>, it is contemplated to provide a set of two bellows <NUM> and <NUM> that are operated in an alternating manner to provide a more continuous flow and to increase flowrate. In an embodiment, driver arm <NUM> of linear actuator <NUM>, e.g., motor <NUM> operably coupled to a rack <NUM> and pinion <NUM> meshing via gear teeth <NUM>, is connected to both bellows <NUM> and <NUM> at a location so as to connect the two bellows together. In the illustrated embodiment, driver arm <NUM> is connected between moving ends 102a and 202a of bellows <NUM> and <NUM>. In this manner, linear actuator <NUM> in (i) a first stroke moves in a first direction to expand a first bellows <NUM> or <NUM> to draw-in fluid and to compress the second bellows <NUM> or <NUM> to pump-out fluid and (ii) a second stroke moves in a second, opposing direction to expand the second bellows <NUM> or <NUM> to draw-in fluid and compress first bellows <NUM> or <NUM> to pump-out fluid. The result is a more continuous flow and an increased flowrate using basically the same linear actuator <NUM> as for the single bellows embodiment of system <NUM> of <FIG>. Bellows <NUM> and <NUM> may each have a hydrophobic membrane <NUM> for priming as described herein and illustrated in <FIG>.

Potentiometer <NUM> is provided again in <FIG>. It stands to reason that bellows <NUM> and <NUM> move the same distance because both bellows are driven by the same rack <NUM>. A single potentiometer <NUM> accordingly outputs both pump-in and pump-out distances to control unit <NUM>. In an alternative embodiment, motor <NUM> is fitted with an encoder (not illustrated), such as an incremental or absolute encoder, which outputs to control unit <NUM> for use in determining volume of fluid pumped in and out, knowing the geometry of each bellows <NUM> and <NUM>.

<FIG> illustrates that alternative disposable set <NUM> is in essence doubled versus disposable set <NUM>. Besides the lines interfacing with bellows <NUM>, including fresh dialysis fluid line <NUM> extending to fresh dialysis fluid supply or bag <NUM>, last fill fluid line <NUM> extending to last dialysis fluid supply or bag <NUM>, patient line <NUM> extending to patient connector <NUM>, drain line <NUM> extending to drain container <NUM>, and heater line <NUM> extending to heater disposable <NUM>, disposable set <NUM> also provides lines for bellows, including dialysis fluid line <NUM> extending also to fresh dialysis fluid supply or bag <NUM>, last fill fluid line <NUM> extending also to last dialysis fluid supply or bag <NUM>, patient line <NUM> extending also to patient connector <NUM>, drain line <NUM> extending also to drain container <NUM>, and heater line <NUM> extending also to heater disposable <NUM>. Additional lines <NUM>, <NUM>, <NUM>, <NUM> and <NUM> operate with valves 144a to 144e, respectively, under control of control unit <NUM>.

Disposable set <NUM> allows complete and independent control between bellows <NUM> and <NUM>. Bellows <NUM> can pull fluid in from any source, while bellows <NUM> can pump out to any destination, and vice versa. It even possible to pull fluid from and push fluid to the same source/destination, e.g., for priming. The trade-off of system <NUM> of <FIG> is (i) the additional disposable cost of second bellows <NUM> and second set of lines <NUM>, <NUM>, <NUM>, <NUM> and <NUM> to each of the sources and destinations and (ii) the additional cost and complexity of a second set of valves 144a to 144e and their respective control of the second set of lines <NUM>, <NUM>, <NUM>, <NUM> and <NUM>.

Single or dual bellows APD system <NUM> of the present disclosure contemplates different solutions for ensuring that motorized bellows <NUM>, <NUM> does not create too much positive or negative fluid pumping pressure when delivering fresh dialysis to or removing used dialysis fluid from the patient via patient line <NUM>, <NUM> and patient connector <NUM>. Generally, it is desirable to limit patient pumping pressure for peritoneal dialysis to -<NUM> psig for effluent removal and from +<NUM> psig to +<NUM> psig for fresh dialysis fluid delivery.

A first pressure control solution is to select motor <NUM> such that it is incapable of supplying (or is controlled not to supply) a positive or negative overpressure. The pressure that fluid is delivered to and removed from the patient is a function of the force exerted by linear actuator <NUM> and the area geometry of bellows <NUM>, <NUM> and tubing <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. The maximum positive and negative patient pumping pressures are known (listed above) as is the geometry of the bellows and tubing. From these values, the maximum allowable force due to linear actuator <NUM> is able to be calculated. Knowing that force allows a maximum torque for motor <NUM> to be calculated so that a motor incapable of supplying a higher torque may be selected.

<FIG> illustrates a relationship between output force of linear actuator <NUM>, e.g., including rack <NUM> and pinion <NUM>, and the torque outputted by motor <NUM>. A different relationship is used for different linear actuators, e.g., the lead screw, ball screw, etc., arrangements listed above. In the illustrated equation, F2T is the force outputted by the rack <NUM> and pinion <NUM>. F2T is set to be the maximum allowable force determined from the known maximum allowable pressure and the known geometry of bellows <NUM>, <NUM> and tubing <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. Diameter d is the nominal diameter of pinion <NUM>, which is also known. Thus the maximum allowable torque T2b outputted by motor <NUM> may be calculated. A single speed motor <NUM> having a maximum torque at or below the maximum is then selected. Or, a variable speed motor is selected for motor <NUM> and a low speed limit is set for patient pumping (motor torque has an inverse relationship with motor speed). Control unit <NUM> of APD system <NUM> of the present disclosure either causes a single speed motor <NUM> to be powered or maintains the low speed limit for variable speed motor <NUM> for patient pumping. Higher motor torques may be used for pumping from sources other than the patient, e.g., from supply container <NUM>, last dialysis fluid supply or bag <NUM>, or heater disposable <NUM>. Higher motor torques may be used for pumping to sources other than the patient, e.g., to drain container <NUM> or heater disposable <NUM>.

A second pressure control solution contemplated for bellows APD system <NUM> of the present disclosure is to place a force sensor <NUM> (load cell or strain gauge) in contact with bellows <NUM>, <NUM>, e.g., between driver arm <NUM> and bellows <NUM>, <NUM> as illustrated in <FIG> and <FIG>. In this manner, force sensors <NUM> are located so as to sense the force applied by driver arm <NUM> of linear actuator <NUM> on the bellows. But instead of calculating a maximum allowable motor torque for patient pumping, the actual force due to the linear actuator <NUM> is measured. The measurement may be used as feedback to control unit <NUM>, which causes the speed of motor <NUM> to be varied to ensure that the resulting force due to linear actuator <NUM> is below the maximum allowable force. The maximum allowable force due to the linear actuator is calculated again knowing the maximum allowable positive and negative patient pumping pressures and the geometry of the bellows <NUM>, common input/output line <NUM>, <NUM> and/or patient line <NUM>, <NUM>. To reduce noise leading to error, such as force to torque conversion, current to torque conversion and current sensing error, it is contemplated to locate the force sensors <NUM> close the item to be sensed, namely, bellows <NUM>. Doing so reduces or eliminates these errors.

<FIG> and <FIG> illustrate a third pressure control solution contemplated for bellows APD system <NUM> of the present disclosure, which is to add a pressure sensing module or pod <NUM> that measures fluid pressure directly and obviates the need to know the geometry of bellows <NUM>, <NUM> and tubing <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, and the need to determine maximum allowable forces. Pressure pod <NUM> in the illustrated embodiment incudes a membrane <NUM> that separates a fluid pumping side <NUM> of the pod from an air transducer sensing side <NUM> of the pod. The flexibility of membrane <NUM> allows pressure on either side of the membrane to equilibrate, such that the pressure of any of the different fluids discussed herein equals the sensed transmission fluid or air pressure. <FIG> illustrates that a pressure transducer <NUM> may be provided on transducer sensing side <NUM> of pressure pod <NUM>. Alternatively, transducer <NUM> may be located at the end of a transmission fluid or air tube (not illustrated).

Transducer <NUM> outputting to control unit <NUM> measures the pressure of transmission fluid or air, which equals that of the PD fluid, patient fluid, heated fluid, effluent or other fluid. <FIG> illustrates that processing <NUM> and memory <NUM> of control unit <NUM> uses the pressure signal as feedback to vary the speed of the electronic driver (may be a separate card of control unit <NUM>) for bellows motor <NUM> to make sure that the resulting positive or negative fluid pressure does not exceed an allowable limit. The pressure limits may be different for different fluid sources and destinations. In <FIG>, control unit <NUM> sets a pressure to be achieved (not just avoiding a pressure limit), which is compared against a pressure signal measured by transducer <NUM>, which may be provided at cycler <NUM>. The difference may be fed into a control algorithm, e.g., a proportional, integral, differential ("PID") algorithm, which attempts to reduce the difference between the commanded pressure and the measured pressure to zero, and results in an output to the electronic motor driver. The above analysis is performed on some periodic frequency. It should be appreciated that in system <NUM> of <FIG>, each bellows <NUM> and <NUM> may cooperate with a pressure sensor or pod <NUM> outputting to control unit <NUM> as described herein.

<FIG> illustrates an alternative pressure sensing embodiment for system <NUM>, in which a pressure measurement cylinder <NUM> is provided and fixed to a wall of housing <NUM>. A piston <NUM> is fitted in a sealed manner, e.g., via an o-ring seal, within pressure measurement cylinder <NUM>. A pressure transducer <NUM> is located so as to be in fluid communication with cylinder <NUM> above piston <NUM>. Pressure transducer <NUM> outputs to control unit <NUM> and is provided by cycler <NUM> in one embodiment. A piston rod <NUM> extends from a head of piston <NUM> to the outside of pressure measurement cylinder <NUM>. Piston rod <NUM> is placed in mechanical communication with moving end 102a of bellows <NUM> (and 202a of bellows <NUM> if provided). Bellows <NUM> via piston <NUM> exerts a force on the air within pressure measurement cylinder <NUM>. When equilibrium is reached, the force of compressed air is equal to the force exerted by bellows <NUM>. The force is deduced from the reading of pressure transducer <NUM> via the equation Pf = Pp x Ap / Ab, where Pp is the pressure of the piston, Ap is the cross-section area of pressure measurement cylinder <NUM> and Ab is the nominal cross-section area of pressure measurement of bellows <NUM>. Hence, the fluid pressure Pf is calculated using the measurement of pressure transducer <NUM>.

As mentioned above, it is important to prime the bellows APD system <NUM> for volumetric accuracy and to prevent the delivery of air to the patient. In one priming sequence under control of control unit <NUM> of the present APD system, the single bellows <NUM> or dual bellows <NUM>, <NUM> pump is caused to first prime the supply line <NUM>, <NUM>. If the volume of a single stroke of the bellows pump is less than the volume of supply line <NUM>, <NUM>, then it is contemplated to open supply line valve 44a, 144a on the draw stroke of the bellows pump, and then to close that valve 44a, 144a and open drain valve 44d, 144d to push air via the subsequent pump-out stroke of the bellows <NUM>, <NUM> to drain. The above sequence is repeated until the supply line is fully primed, which may be detected by a sensor (not illustrated) located at the common input/output line, or determined empirically to require a certain amount of pump strokes.

The priming operation of supply line <NUM>, <NUM> is then repeated for all supply lines and last bag line <NUM>, <NUM>. With the supply and last bag lines primed, fresh dialysis fluid is then used to prime patient line <NUM>, <NUM> up to patient connector <NUM>, which may be set at a certain elevation/height. Patient connector <NUM> is alternatively placed next to a sensor that determines when the patient line is fully primed. Heater line <NUM>, <NUM> is then primed at least up to its interaction with heater valve 44e, 144e. Drain line <NUM>, <NUM> may or may not be primed, e.g., may be primed up to drain line valve 44d, 144d.

Alternatively or additionally to the above sequence, fixed ends 102b, 202b may be elevated during priming to help direct air into common input/output lines <NUM>, <NUM>, which aids in sending the air to drain container <NUM> or to a house drain. Further alternatively or additionally, hydrophobic membranes <NUM> may be fitted to bellows <NUM>, <NUM> to aid the priming of same.

<FIG> illustrates another alternative pressure sensing embodiment for system <NUM>, in which a pressure measurement is taken directly along a fluid line, for example along common line <NUM>, <NUM> or patient line <NUM>, <NUM>. In the illustrated embodiment, a dome <NUM> is welded to or formed above a pressure sensing area or diaphragm <NUM> of common line <NUM>, <NUM> or patient line <NUM>, <NUM>. Common line <NUM>, <NUM> or patient line <NUM>, <NUM> may include an increased diameter section (not illustrated), if needed, onto which dome <NUM> and pressure sensing diaphragm <NUM> are located. Pressure sensing area or diaphragm <NUM> may have the same curvature and be of the same thickness as the rest of common line <NUM>, <NUM> or patient line <NUM>, <NUM>. Alternatively, pressure sensing area <NUM> is either one or both of flattened and/or thinner that the rest of common line <NUM>, <NUM> or patient line <NUM>, <NUM>. For example, pressure sensing diaphragm <NUM> could be a thin circular membrane that is welded into a hole formed in common line <NUM>, <NUM> or patient line <NUM>, <NUM>, after which pressure dome <NUM> is welded to the fluid line above the pressure sensing diaphragm <NUM>. The welding may be via any of ultrasonic welding, heat sealing or solvent bonding.

A pressure transmission line <NUM> extends to a pressure transducer <NUM>, which communicates with control unit <NUM> and may be provided at cycler <NUM>. The output of pressure transducer <NUM> may be used in the manner discussed in connection with <FIG>. Pressure transmission line <NUM> also extends to a vent valve 44v, which is under control of control unit <NUM>. Vent valve 44v is used in one embodiment to help ensure that pressure sensing diaphragm <NUM> is located in a proper "zero" pressure position in <FIG>, such that it will flex over an entire range of pressures without reaching a positive +ve pressure elastic limit or a negative -ve pressure elastic limit.

<FIG> illustrates via the plot line to the left (long/short dash) that if pressure sensing diaphragm <NUM> is initially too close to the positive pressure +ve limit at zero pressure, then the diaphragm will reach its positive elastic limit +ve (flat lining) prior to the upper, positive target pressure (e.g., +<NUM> psig) level being reached. <FIG> also illustrates via the plot line to the right (constant dash) that if pressure sensing diaphragm <NUM> is initially too close to the negative pressure -ve limit at zero pressure, then the diaphragm will reach its negative elastic limit -ve (flat lining) prior to the lower, negative target pressure (e.g., -<NUM>. 5psig) level being reached.

<FIG> illustrates via the plot line in the middle (solid line) a situation in which pressure sensing diaphragm <NUM> is initially located in a suitable position at zero pressure, such that it flexes and outputs a pressure change over an entire range for both the positive and negative target pressure limits. Referring additionally to <FIG>, it is contemplated that at a desirable time, e.g., prior to treatment and/or during a patient dwell, to close line valves 44a to 44e and vent valve 44v and place common line <NUM>, <NUM> or patient line <NUM>, <NUM> under a known positive or negative pressure to move pressure sensing diaphragm <NUM> outwardly or inwardly, respectively, a small distance. Next, control unit <NUM> opens vent valve 44v so that pressure sensor <NUM> reads zero pressure. Control unit <NUM> then closes vent valve 44v and attempts to reach both positive and negative target pressures. If control unit <NUM> sees that either the positive or negative target pressure cannot be met (diaphragm <NUM> meets an elastic limit), then control unit <NUM> repeats the above procedure correcting the zero pressure position of pressure sensing diaphragm <NUM> in the proper direction. For example, if the positive pressure target cannot be met, then control unit <NUM> causes pressure sensing diaphragm <NUM> (i) to move less outwardly, (ii) to not move at all, or (iii) to move inwardly in the next attempt to reach both positive and negative target pressures. If on the other hand the negative pressure target cannot be met, then control unit <NUM> causes pressure sensing diaphragm <NUM> (i) to move less inwardly, (ii) to not move at all, or (iii) to move outwardly in the next attempt to reach both positive and negative target pressures.

The test is repeated, each time adjusting the diaphragm position based on the previous result until a suitable starting position for diaphragm <NUM> is detected. Control unit <NUM> remembers the pressure associated with such position and applies such pressure on the next patient fill or patient drain before opening vent valve 44v to zero out the pressure in preparation for the fill or drain.

To summarize the above methodology for system <NUM>, in a first step, line valves 44a to 44e and vent valve 44v are closed and common line <NUM>, <NUM> or patient line <NUM>, <NUM> are placed under a known positive or negative starting pressure to move pressure sensing diaphragm <NUM> outwardly or inwardly. In a second step, vent valve 44v is opened so that the pressure in dome <NUM> falls to zero. In a third step, the vent valve 44v is closed and control unit <NUM> operates bellows pump <NUM>, <NUM> to attempt to perform a pressure sweep to reach both positive and negative target pressures. If both pressure limits can be reached or met, then in a fourth step, control unit <NUM> stores the pressure from first step so as to be associated with the successful position and causes such pressure to be applied on the next patient fill or patient drain before opening vent valve 44v to zero out the pressure in preparation for the fill or drain. If either pressure limit cannot be reached or met, then in a fifth step, control unit <NUM> modifies the pressure in a direction (more or less positive or more or less negative) that attempts to correct the limit that could not be reached or met and returns to the first step, but now using the modified pressure. The above steps are repeated until a suitable pressure and position for diaphragm <NUM> is determined.

System <NUM> is also configured to determine if diaphragm <NUM> has moved from its starting position, e.g., using a recalibration sequence. For example, during a patient dwell phase, system <NUM> applies the starting pressure that caused diaphragm <NUM> to move over the entire pressure range, so that the diaphragm moves to the designated position. Vent valve 44v is then opened to zero the pressure. System <NUM> then attempts to meet both pressure limits using the diaphragm and applying a pressure sweep. If both limits are met then the starting pressure is maintained. If not, then the procedure described above is repeated until a new starting pressure for diaphragm <NUM> is determined and used for the next fill or drain.

It should be appreciated that the dome <NUM> of <FIG> and its associated functionality in connection with <FIG> may be used for any type of fluid delivery system using any type of pump, such as a bellows, peristaltic, membrane or syringe pump to pump any desired fluid, such as peritoneal or hemodialysis dialysis fluid, blood, replacement fluid, heparin, citrate, an intravenous drug, saline, lactated ringers, and/or a nutritional fluid. It is contemplated to use such structure and functionality for any type of therapy, treatment or modality, including but not limited to, plasmapherisis, hemodialysis ("HD"), hemofiltration ("HF") hemodiafiltration ("HDF"), continuous renal replacement therapy ("CRRT"), peritoneal dialysis ("PD"), intravenous drug delivery, and nutritional fluid delivery.

<FIG> are perspective views of one configuration for bellows system <NUM> having an integrated pressure sensor of the present disclosure. Here system <NUM> includes a manifold <NUM>, which may be a rigid plastic molded manifold made of any of the materials discussed herein. Manifold <NUM> forms a common line or port <NUM>, <NUM> that seals to outlet end 102b of bellows <NUM>, <NUM>. Manifold also <NUM> forms ports for fresh dialysis fluid lines <NUM>, <NUM>, last fill fluid lines <NUM>, <NUM>, patient lines <NUM>, <NUM>, drain lines <NUM>, <NUM> and heater lines <NUM>, <NUM>. Manifold <NUM> includes a common fluid chamber <NUM> that interfaces with a fluid side of flexible, pressure transmitting diaphragm <NUM>. Manifold <NUM> and diaphragm <NUM> are disposable in one embodiment.

Common fluid chamber <NUM> seals to an air chamber <NUM>, trapping pressure transmitting diaphragm <NUM> between chambers <NUM> and <NUM>. Air chamber <NUM> in the illustrated embodiment connects in a sealed manner, e.g., via compression or luer connection, to air transmission line <NUM>, which extends to a vent valve 44v under control of control unit <NUM> and to a pressure transducer <NUM> outputting to control unit <NUM>. Air chamber <NUM>, air transmission line <NUM>, vent valve 44v and pressure transducer <NUM> are each reusable components provided as part of cycler <NUM> in one embodiment. The diaphragm <NUM> positioning routine described in connection with <FIG> may also be performed with the chamber <NUM> and diaphragm <NUM> configuration of system <NUM> illustrated in <FIG>.

Referring now to <FIG>, structure and methodology are added to system <NUM> to allow the system to self-calibrate how much fresh or used dialysis fluid is actually moved over a partial or full stroke of bellows <NUM>, <NUM>. The self-calibration allows for variance between different bellows <NUM>, <NUM> of different systems. The self-calibration also allows the manufacturing tolerances for the bellows to be less stringent. For example, suppose bellows <NUM>, <NUM> is sized to deliver <NUM> milliliters ("ml") per stroke. Without the calibration routine of <FIG>, bellows <NUM>, <NUM> may have to be manufactured so as to have an actual stroke volume of <NUM> to <NUM>/stroke for example. Providing the calibration routine of <FIG>, on the other hand, may allow bellows <NUM>, <NUM> of system <NUM> to have a considerably wider stroke volume, e.g., <NUM> to <NUM>/stroke.

<FIG> use the same numbering provided in connection with <FIG>. It should be appreciated however that the structure and methodology (e.g., implemented via control unit <NUM>) associated with the calibration routine of <FIG> may be used with any of the alternative embodiments for system <NUM> discussed herein. Additionally, air transmission line <NUM> is illustrated as extending to an air cylinder <NUM>. A piston head <NUM> is provided in a sealed, e.g., via an o-ring seal, and moveable manner within air cylinder <NUM>. A piston rod <NUM> extends from piston head <NUM> to a linear actuator <NUM> under control of control unit <NUM>. Linear actuator <NUM> in one embodiment includes a rotating nut motor <NUM>, wherein piston rod <NUM> includes a lead screw or ball screw that threads directly into rotating nut motor <NUM>. Linear actuator <NUM> is alternatively of a rack and pinion arrangement or includes a stepper motor coupled to a lead screw or ball screw. Linear actuator <NUM> additionally includes a potentiometer or encoder as discussed herein that outputs to control unit <NUM> for determining precisely how far piston head <NUM> moves within cylinder <NUM>.

In <FIG>, the first step of the calibration routine is to record a known initial pressure Pinitial, which can be a zero pressure or a slightly positive pressure. <FIG> illustrates that in a second step, control unit <NUM> causes bellows <NUM>, <NUM> to be advanced a first distance (to D1), pushing fluid into fluid chamber <NUM> and increasing the pressure as measured at pressure transducer <NUM> to a higher pressure Phigher. Linear actuator <NUM> then retracts piston rod <NUM> and piston head <NUM> until the measured pressure returns from Phigher to Pinitial. The potentiometer or encoder measures that distance that piston rod <NUM> and piston head <NUM> have been retracted, wherein control unit <NUM> knowing the cross-sectional area of cylinder <NUM> calculates the volume associated with the retracted distance. Because the starting and ending pressures are equal at Pinitial, the volume of fluid displaced by bellows <NUM>, <NUM> over the first distance (to D1) is equal to the known volume of air through which piston head <NUM> traveled. Control unit <NUM> records this first volume displaced and assigns it to the first distance (to D1) moved by the bellows.

In <FIG>, control unit <NUM> in a third step maintains bellows <NUM>, <NUM> at the first distance position (D1) and opens drain valve 44d, 144d to allow linear actuator <NUM> to push at least some of the fluid within fluid chamber <NUM> to drain <NUM>. In <FIG>, the action taken by control unit <NUM> in connection with <FIG> is repeated in a fourth step, but here causing bellows <NUM>, <NUM> to be advanced a second distance (which may be the same or different than the first distance) to D2, pushing fluid into fluid chamber <NUM> and increasing the pressure as measured at pressure transducer <NUM> from an initial pressure Pinitial to a higher pressure Phigher. Linear actuator <NUM> then retracts piston rod <NUM> and piston head <NUM> until the measured pressure returns from Phigher to Pinitial. The potentiometer or encoder measures the distance that piston rod <NUM> and piston head <NUM> have been retracted, wherein control unit <NUM> knowing the cross-sectional area of cylinder <NUM> calculates the volume associated with the retracted distance. Because the starting and ending pressures are equal at Pinitial, the volume of fluid displaced by bellows <NUM>, <NUM> over the second distance (to D2) is equal to the known volume of air through which piston head <NUM> traveled. Control unit <NUM> records this second volume displaced and assigns it to the second distance (to D2) moved by bellows <NUM>, <NUM>.

<FIG> illustrates that control unit <NUM> repeats the above procedure until a complete stroke has been mapped, noting the volume of fluid displaced over each segment D1, D2. Dn of bellows <NUM>, <NUM> travel. Control unit <NUM> sums the different volumes of fluids displaced so that it is known precisely for the particular bellows how much fluid is pumped over a first, second, third, etc., portion of a stroke, and over the entire total stroke. The above-described calibration procedure is accurate for pumping either fresh or used dialysis fluid and may be performed before treatment begins and if needed during each patient dwell until disposable set <NUM> is discarded at the end of treatment. To this end, it should be noted that the calibration routine of <FIG> adds no additional disposable components to the version of system <NUM> described in connection with <FIG>.

It should also be appreciated that the calibration procedure described in connection with <FIG> may be used with any type of pump, such as a bellows, peristaltic, membrane or syringe pump to pump any desired fluid, such as peritoneal or hemodialysis dialysis fluid, blood, replacement fluid, heparin, citrate, an intravenous drug, saline, lactated ringers, and/or a nutritional fluid. It is contemplated to use the structure and functionality of <FIG> for any type of therapy, treatment or modality, including but not limited to, plasmapherisis, hemodialysis ("HD"), hemofiltration ("HF") hemodiafiltration ("HDF"), continuous renal replacement therapy ("CRRT"), peritoneal dialysis ("PD"), intravenous drug delivery, and nutritional fluid delivery.

<FIG> and <FIG> illustrate that in another version of system <NUM>, the direct pressure of the linear actuator can be still be measured, but that the pressure pod of previous examples may be eliminated, simplifying disposable set <NUM> and reducing disposable cost. In <FIG>, an incompressible fluid chamber 134a is provided into which a piston 136a is movably and in a sealed manner, e.g., via an o-ring seal, located. Chamber 134a and piston 136a capture an incompressible fluid <NUM>, such as water or oil. Chamber 134a includes a fluid sensing line <NUM> that leads to a liquid or fluid pressure sensor <NUM>, which outputs to control unit <NUM>.

Any of linear actuators <NUM>, <NUM> under control of control unit <NUM>, including any of the structure and alternatives described herein, e.g., stepper motor and lead or ball screw, rack and pinion, or rotating nut motor, may be provided and operate with any kind of motion detection equipment, such as a potentiometer or encoder, outputting to control unit <NUM>. Linear actuator <NUM>, <NUM> is positioned as illustrated to advance or retract chamber 134a and thus may be coupled directly or indirectly to the chamber. Piston 136a is likewise coupled directly or indirectly to moving end 102a of bellows <NUM>. Piston 136a, sealed inside chamber 134a via an o-ring, does not dislodge from chamber 134a when the chamber is retracted due to the fact that fluid <NUM> is incompressible. With an incompressible fluid, any pressure, positive or negative, may be generated without any significant change in volume. Without change in volume, piston 136a does not move.

In an embodiment, the inner diameter of chamber 134a is the same as the effective pumping diameter within bellows <NUM>, <NUM> such that the pressure that linear actuator <NUM>, <NUM> applies to incompressible fluid <NUM> is the same pressure that bellows <NUM>, <NUM> applies to fresh or used dialysis fluid. This phenomenon is true for the positive pumping of fresh dialysis fluid to the patient and the removal used dialysis fluid from the patient under negative pressure. It is accordingly contemplated for control unit <NUM> to use the output of liquid or fluid pressure sensor <NUM> in a feedback loop, similar to the feedback loop of <FIG>, to control the actual pressure of incompressible fluid <NUM> and dialysis fluid so as to match that of a commanded pressure stored in control unit <NUM>.

System <NUM> of <FIG> operates in the same manner as system <NUM> of <FIG>. In <FIG>, an alternative incompressible fluid chamber 134b and an alternative set of pistons 136b are provided to hold two columns of incompressible fluid <NUM>. Pistons 136b are moveable in a sealed manner, e.g., via o-ring seals, inside fluid chamber 134b. Each column of incompressible fluid <NUM> communicates via an incompressible fluid sensing line <NUM> with a fluid pressure sensor <NUM>, which outputs to control unit <NUM>. Pressure sensors <NUM> provide redundant readings, which are checked against each other to ensure accurate feedback to control unit <NUM>. In an embodiment, if the pressure readouts do not match, then an alarm or alert is provided via user interface <NUM> and treatment is paused or terminated.

As with system <NUM> of <FIG>, in system <NUM> of <FIG> the inner diameter of chamber 134b for both fluid columns is the same as the effective pumping diameter within bellows <NUM>, <NUM>, so that the pressure that linear actuator <NUM>, <NUM> applies to incompressible fluid <NUM> in both columns is the same pressure that bellows <NUM>, <NUM> applies to fresh or used dialysis fluid. Control unit <NUM> uses the output of fluid pressure sensors <NUM> (e.g., averaged or otherwise combined, or only a single pressure signal is used as feedback wherein the other pressure signal is only for checking) in a feedback loop, similar to the feedback loop of <FIG>, to control the actual pressure of incompressible fluid <NUM> and dialysis fluid, so as to match that of a commanded pressure stored in the control unit.

<FIG> illustrates one embodiment of a method <NUM> carried out by any version of control unit <NUM> discussed herein for detection of (i) a failure of any of valves 44a to 44e, 44v, 144a to 144e, and (ii) for air detection. <FIG> is applicable to any bellows APD cycler and associated system discussed herein. At block <NUM>, method <NUM> begins. At block <NUM>, the valve to be interrogated is opened. At block <NUM>, bellows <NUM>, <NUM> is loaded with fluid. At block <NUM>, all valves are closed. At block <NUM>, compression of bellows <NUM>, <NUM> occurs under a controlled force via control unit <NUM>. At diamond <NUM>, it is determined via potentiometer <NUM> (or encoder) if bellows <NUM>, <NUM> moves beyond a threshold set in control unit <NUM>. If not, as determined at block <NUM>, then no air is present and the relevant valve may be opened to continue pumping. If so, as determined at block <NUM>, then an air/valve failure is detected and the position of bellows <NUM>, <NUM> is monitored further. At diamond <NUM>, it is determined via potentiometer <NUM> (or encoder) if bellows <NUM>, <NUM> moves back. If so, as determined at block <NUM>, then control unit <NUM> determines air to be present. If not, as determined at block <NUM>, then control unit <NUM> determines the relevant valve to have failed. A suitable response is taken by control unit <NUM> (e.g., halt treatment) and an error message/alarm may be provided by user interface <NUM>. At block <NUM>, method <NUM> ends.

Claim 1:
A peritoneal dialysis system (<NUM>) comprising:
a bellows (<NUM>);
a common inlet/outlet fluid receptacle (<NUM>, <NUM>) in fluid communication with the bellows;
a plurality of fluid lines (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) in fluid communication with the common inlet/outlet receptacle;
a linear actuator (<NUM>, <NUM>, <NUM>, <NUM>) positioned and arranged to expand and compress the bellows;
a plurality of valves (44a, 44b, 44c, 44d, 44e) positioned and arranged to allow or occlude flow through the plurality of fluid lines to or from the bellows; and
a control unit (<NUM>) configured to control the linear actuator (<NUM>, <NUM>, <NUM>, <NUM>) and the plurality of valves (44a, 44b, 44c, 44d, 44e).