Peritoneal dialysis system with cylinder and optional air pump

Abstract

In one example, the control unit (i) causes the second pneumatic valve and the source fluid valve to open and causes the linear actuator to move the piston head into the first cylinder chamber, thereby creating a negative pressure in the pneumatic pump chamber and drawing the source fluid into the fluid pump chamber; (ii) causes the first pneumatic valve and the destination fluid valve to open and causes the linear actuator to move the piston head into the first cylinder chamber and force the source fluid into the destination fluid valve; and the control unit controls the linear actuator using the pressure sensor readings to make the final pressure of (ii) at least substantially equal to the initial pressure of (ii), such that the volume of space corresponding to the movement of the piston head in the cylinder during (ii) is equal to the volume of source fluid delivered from the fluid pump chamber.

Description

[Technical Field]

[0001] background FIELD OF THE DISCLOSURE The present disclosure relates generally to medical fluid therapy and, more particularly, to dialysis fluid therapy. [Background technology]

[0002] A variety of causes can cause a person's renal system to fail. Renal failure produces several physiological disturbances: it is no longer possible to balance water and minerals or excrete the daily metabolic load. Toxic end products of metabolism, such as urea, creatinine, uric acid, and others, can accumulate in the patient's blood and tissues.

[0003] Declining kidney function, particularly kidney failure, is treated with dialysis, which removes waste products, toxins, and excess water from the body that normally would be removed by normally functioning kidneys. Dialysis treatment to replace kidney function is vital for many people because the treatment is lifesaving.

[0004] One type of kidney failure therapy is hemodialysis ("HD"), which generally uses diffusion to remove waste products from a patient's blood. A diffusion gradient occurs across a semipermeable dialyzer between the blood and an electrolyte solution called the dialysate or dialysis fluid, causing diffusion.

[0005] Hemofiltration ("HF") is an alternative renal replacement therapy that relies on the convective transport of toxins from the patient's blood. HF is achieved by adding replacement or substitution fluid to the extracorporeal circuit during treatment. The replacement fluid, and fluid accumulated by the patient during treatment, is ultrafiltered during the course of HF treatment, providing a convective transport mechanism that is particularly useful for removing middle and large molecules.

[0006] Hemodiafiltration ("HDF") is a treatment modality that combines convective and diffusive clearance. HDF uses dialysis fluid flowing through a dialyzer, similar to standard hemodialysis, to provide diffusive clearance. In addition, replacement solution is provided directly to the extracorporeal circuit to provide convective clearance.

[0007] Most HD, HF, and HDF treatments are performed in centers. Today, there is a trend toward home hemodialysis ("HHD"), in part because HHD can be performed daily, offering therapeutic benefits over in-center hemodialysis treatments, which are typically performed twice or three times per week. Studies have shown that more frequent treatments remove more toxins and waste products and result in less interdialytic fluid overload than patients receiving less frequent but potentially longer treatments. Patients receiving more frequent treatments do not experience as much downcycling (fluid and toxin fluctuations) as in-center patients who accumulate two or three days' worth of toxins before treatment. In certain areas, the nearest dialysis center may be many miles from a patient's home, causing door-to-door treatment times to consume a significant portion of a patient's day. Treatments at centers closer to the patient's home may also consume a significant portion of a patient's day. HHD can be performed at night or during the day when the patient is relaxing, working, or otherwise productive.

[0008] Another type of renal failure therapy is peritoneal dialysis ("PD"), in which a dialysis solution, also called dialysis fluid, is infused through a catheter into a patient's peritoneal cavity. The dialysis fluid contacts the peritoneal membrane within the patient's peritoneal cavity. Waste, toxins, and excess water enter the dialysis fluid from the patient's bloodstream through capillaries in the peritoneal membrane by diffusion and osmosis; i.e., an osmotic gradient is created across the membrane. Osmotic agents in the PD dialysis fluid create the osmotic gradient. Spent or spent dialysis fluid is pumped out of the patient, removing the waste, toxins, and excess water from the patient. This cycle may be repeated, for example, multiple times.

[0009] 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. In this, a patient manually connects an implanted catheter to a drain, allowing used or spent dialysis fluid to drain from the peritoneal cavity. The patient then switches the fluid connection, so that the patient catheter is in communication with a bag of fresh dialysis fluid, infusing fresh dialysis fluid into the patient through the catheter. The patient disconnects the catheter from the bag of fresh dialysis fluid, allowing the dialysis fluid to dwell in the peritoneal cavity, where waste, toxins, and excess water are transported. After the dwell period, the patient repeats the manual dialysis procedure, for example, four times a day. Manual peritoneal dialysis requires significant patient time and effort and leaves significant room for improvement.

[0010] Automated peritoneal dialysis ("PD") is similar to CAPD in that dialysis treatment includes drain, fill, and dwell cycles. However, automated PD machines perform these cycles automatically, typically while the patient sleeps. Automated PD machines relieve patients of the need to manually perform treatment cycles and transport supplies during the day. Automated PD machines are fluidly connected to an implanted catheter, a source or bag of fresh dialysis fluid, and a fluid drain. The automated PD machine pumps fresh dialysis fluid from the dialysis fluid source through the catheter and into the patient's peritoneal cavity. Automated PD machines also allow the dialysis fluid to dwell within the cavity, allowing for the transfer of waste, toxins, and excess water. The source may contain multiple liters of dialysis fluid, including several solution bags.

[0011] APD machines pump used or spent dialysate from the patient's peritoneal cavity through a catheter to a drain. Similar to the manual process, several drain, fill, and dwell cycles occur during dialysis. A "final fill" may occur at the end of an APD treatment. The final fill may remain in the patient's peritoneal cavity until the start of the next treatment, or it may be manually emptied at some point during the day.

[0012] In all of the above modes of using automated machines, the automated machines typically operate using disposable sets that are discarded after a single use. Depending on the complexity of the disposable set, the cost of using one set per day can be significant. Furthermore, daily disposables require storage space, which can be cumbersome for homes and businesses. Furthermore, changing daily disposables requires time and effort from the patient or caregiver to set up each day at home or in the clinic.

[0013] APD devices also need to be portable so that patients can take their devices on vacation or business trips, and they need to have pumping accuracy so that the APD device can accurately track how much ultrafiltrate ("UF") is removed from the patient over the course of treatment.

[0014] For each of the above reasons, it would be desirable to provide a relatively simple and compact dialysis machine, such as an APD machine, that is accurate and operates with a simple and cost-effective disposable set. Summary of the Invention [Means for solving the problem]

[0015] overview The present disclosure relates to a peritoneal dialysis ("PD") machine or cycler powered by an air cylinder and, optionally, an air pump. In a first main embodiment, only an air cylinder is provided. The air cylinder is between a first air pressure pump chamber and a second air pressure pump chamber. A piston is located within the air cylinder, and the piston includes a piston head that separates the air cylinder into the first and second cylinder chambers. A first air pressure line extends from the first cylinder chamber to the first air pressure pump chamber. A second air pressure line extends from the second cylinder chamber to the second air pressure pump chamber. A first pressure sensor is located to read the air pressure in the first air pressure line, the first air pressure pump chamber, and the first cylinder chamber. A second pressure sensor is located to read the air pressure in the second air pressure line, the second air pressure pump chamber, and the second cylinder chamber.

[0016] A first vent line and associated first vent valve are optionally disposed in fluid communication with the first cylinder chamber. A second vent line and associated second vent valve are optionally disposed in fluid communication with the second cylinder chamber. The piston further includes a piston shaft coupled outside the air cylinder to a linear actuator for translating the piston shaft and piston head within the cylinder.

[0017] All valves, motors of the linear actuators, PD fluid heaters, and other controllable electrical devices are under the control of a control unit that includes at least one processor, at least one memory, and a video controller for controlling the user interface. The control unit is further configured to receive signals from all sensors, such as air pressure sensors, fluid pressure sensors (if provided), motor encoders (for the linear actuators, if provided), and any temperature sensors associated with the heaters. The control unit is programmed to execute all pumping sequences discussed herein.

[0018] In one embodiment, the PD machine or cycler operates in conjunction with a disposable set. Among other things, the disposable set includes first and second fluid pump chambers that operate in conjunction with the first and second pneumatic pump chambers, respectively. When the piston head is moved to generate negative air pressure in the first or second cylinder chamber, a corresponding negative pressure is generated in the respective first or second pneumatic pump chamber. The negative pressure generated in the first or second pneumatic pump chamber then draws the flexible membrane of the corresponding first or second fluid pump chamber into the first or second pneumatic pump chamber, thereby filling the fluid pump chamber with new or used PD fluid. When the piston head is moved to generate positive air pressure in the first or second cylinder chamber, a corresponding positive pressure is generated in the respective first or second pneumatic pump chamber. The positive pressure generated in the first or second pneumatic pump chamber then pushes the flexible membrane of the corresponding first or second fluid pump chamber, causing the fluid pump chamber to close and expel new or used PD fluid.

[0019] The control unit of the first main embodiment causes the piston shaft to translate the piston head back and forth within the air cylinder, so that in one half-stroke (i), the first pump chamber fills with new or used PD fluid while the second fluid pump chamber expels new or used PD fluid. In the second half-stroke (ii), the second pump chamber fills with new or used PD fluid while the first fluid pump chamber expels new or used PD fluid. The control unit translates the piston head back and forth in the manner described above until a desired or predetermined volume of new or used PD fluid is delivered from the desired PD fluid source to the desired PD fluid destination. Fluid valves are provided and sequentially actuated by the control unit to access the desired fluid source and the desired fluid destination. The fluid valves may be magnetically actuated solenoid valves, electrically operated pinch valves, pneumatically actuated valves, or the like.

[0020] In the first main embodiment, and when patient pumping is performed where pressure control is important, the control unit monitors the outputs from the first and second pressure sensors while the piston head translates back and forth, and controls the rate of back and forth translation so as not to exceed a desirable and safe negative or positive fluid pumping pressure.

[0021] In the first main embodiment, the amount of new or used PD fluid delivered to the destination is determined by maintaining a constant pressure before and after the piston head movement, which counteracts the effects of the compressibility of the air in the cylinder. Because the pressure after the movement (P2) is equal to the pressure before the movement (P1), the volume of air in the cylinder remains constant. Therefore, the volume displaced by the piston head is equal to the volume of fluid delivered.

[0022] In the second main embodiment, only an air cylinder is provided as before, but now the air cylinder is dedicated to a single air / fluid pump chamber pair. Two air / fluid pump chamber pairs may be provided, with each pair having its own dedicated air cylinder. The air cylinders are structured similarly to the first main embodiment, including a piston head and a piston shaft driven by a linear actuator. Optional vent lines and air vent valves may be pneumatically connected to the first and second cylinder chambers of each air cylinder.

[0023] In the second main embodiment, first and second pneumatic lines extend from the first and second cylinder chambers, respectively, to the same pneumatic pump chamber. First and second pneumatic valves under the control of a control unit are provided along the first and second pneumatic lines. One or more pressure sensors are provided along a common portion of the first and second pneumatic lines or along each of the first and second pneumatic lines. A fluid pump chamber, again provided as part of the disposable set, pumps fresh or used PD fluid from a desired PD fluid source to a desired destination, as determined by the sequence of one or more fluid valves.

[0024] The control unit of the second main embodiment causes the piston shaft to translate the piston head toward one of the first or second cylinder chambers, e.g., the first cylinder chamber, to generate positive pressure in the first cylinder chamber and negative pressure in the second cylinder chamber. The control unit also causes the source fluid valve and the second pneumatic valve to open, allowing negative pressure to reach the pneumatic pump chamber and drawing the flexible membrane into the pneumatic pump chamber, causing it to fill with new or used PD fluid.

[0025] The control unit then closes the source fluid valve and the second pneumatic valve and opens the first pneumatic valve, allowing the pressure sensor to read a positive pressure in the first cylinder chamber. The control unit also moves the piston into the first cylinder chamber, causing the positive pressure in the pneumatic pump chamber to read a desired pressure, e.g., 1.5 psig, for pumping new or used PD fluid to the desired destination. At the end of such movement, the piston head is in the initial piston head position.

[0026] The control unit then maintains the first pneumatic valve open and opens the destination fluid valve. The desired positive pressure built in the pneumatic pump chamber forces the flexible membrane of the fluid pump chamber to contract, pushing new or used PD fluid to the desired destination. When the positive pressure dissipates, the control unit moves the piston further into the first cylinder chamber, causing the pressure sensor to continue reading the desired pressure, e.g., 1.5 psig.

[0027] Eventually, the flexible membrane can no longer contract, causing the pressure sensor reading to spike, at which point the control unit stops the pump-out translation of the piston head and closes the destination fluid valve. The detection that the flexible membrane can no longer contract may alternatively or additionally be determined by the control unit detecting that the linear actuator and / or piston head are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping the pump-out translation, the first pneumatic valve remains open, allowing the positive pressure maintained at the desired pressure to equalize between the first cylinder chamber and the pneumatic pump chamber, which can be read by the pressure sensor. The piston head is now in the final piston head position. The volume difference of the known cross-sectional area of ​​the pneumatic cylinder between the final and initial piston head positions is the volume of new or used PD fluid that will be pumped to the desired destination when the pressure at the initial and final piston head positions is the same, e.g., 1.5 psig, the desired pump-to-patient pressure. That is, the volume of space corresponding to the movement of the piston head within the cylinder is a function of the distance moved by the piston head within the cylinder and the cross-sectional area of ​​the cylinder's inner diameter.

[0028] Next, with the second cylinder chamber still under negative pressure (not critical in the case of a pull from a non-patient source), the control unit causes the source fluid valve and second pneumatic valve to open, allowing negative pressure to reach the pneumatic pump chamber, causing the flexible membrane to be drawn into the pneumatic pump chamber, filling it with new or used PD fluid.

[0029] The control unit then closes the source fluid valve but leaves the second pneumatic valve open, leaving the pneumatic pump chamber and the second cylinder chamber exposed to the pressure sensor. The control unit then translates the piston into the second cylinder chamber until the pressure sensor reads 0 psig. The pressure in the first cylinder chamber should also be close to 0 psig.

[0030] The control unit then moves the piston into the second cylinder chamber with the source and destination fluid valves closed, the first pneumatic valve closed, and the second pneumatic valve open so that the pressure sensor can read the positive pressure in the second cylinder chamber, so that the positive pressure in the pneumatic pump chamber again reads the desired pressure, e.g., 1.5 psig, for pumping new or used PD fluid to the desired destination. At the end of such movement, the piston head is again in the initial piston head position.

[0031] The control unit then maintains the second pneumatic valve open and opens the destination fluid valve. The desired positive pressure built in the pneumatic pump chamber again forces the flexible membrane of the fluid pump chamber to contract, pushing new or used PD fluid to the desired destination. When the positive pressure dissipates, the control unit moves the piston further into the second cylinder chamber, causing the pressure sensor to continue reading the desired pressure, e.g., 1.5 psig.

[0032] Eventually, the flexible membrane can no longer contract, causing the pressure sensor reading to spike, at which point the control unit stops the pump-out translation of the piston head and closes the destination fluid valve. The detection that the flexible membrane can no longer contract may alternatively or additionally be determined by the control unit detecting that the linear actuator and / or piston head are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping the pump-out translation, the second pneumatic valve remains open, allowing the positive pressure maintained at the desired pressure to equalize between the first cylinder chamber and the pneumatic pump chamber, which can be read by the pressure sensor. The piston head is now in the final piston head position. The volume difference of the known cross-sectional area of ​​the pneumatic cylinder between the final piston head position and the initial piston head position is, again, the volume of new or used PD fluid that will be pumped to the desired destination when the pressure at the initial and final piston head positions is the same, e.g., 1.5 psig, the desired pump-to-patient pressure.

[0033] With the first cylinder chamber still under negative pressure (which is not critical when pulling from a non-patient source), the control unit opens the source fluid valve and the first pneumatic valve, allowing negative pressure to reach the pneumatic pump chamber, drawing the flexible membrane into the pneumatic pump chamber and filling it with new or used PD fluid. The above process is repeated until the desired amount of new or used PD fluid has been delivered to the desired destination. It should be understood that the above process may be used with any of the new or used PD fluid sources and any of the new or used PD fluid destinations described herein, and that both the aspiration and delivery pressures and the delivered PD fluid volume may be controlled and measured, respectively.

[0034] The third main embodiment introduces an air pump that operates in conjunction with an air cylinder. Air pumps generally can transition more quickly from pumping positive pressure to pumping negative pressure and vice versa. They also allow a smaller air pump to generate a wider range of pressures. These two advantages of air pumps are combined with the ability of air cylinders to meter known volumes of fluid under pressure control as described herein.

[0035] The pneumatic cylinder of the third embodiment is structured substantially similarly to the first and second main embodiments and includes a piston head and a piston shaft driven by a linear actuator. Optional vent lines and pneumatic vent valves may be pneumatically connected to the first and second cylinder chambers of each pneumatic cylinder. In the third main embodiment, only a first pneumatic line extends from the pneumatic cylinder to the pneumatic pump chamber. A first pneumatic valve under the control of the control unit is provided along the first pneumatic line. A second pneumatic line extends from the pneumatic pump and intersects with the first pneumatic line. A second pneumatic valve under the control of the control unit is provided along the second pneumatic line. A pressure sensor is provided along the common portion of the first and second pneumatic lines. One or more fluid pump chambers are again provided as part of the disposable set, where the fluid pump chambers pump fresh or used PD fluid from a desired PD fluid source to a desired destination as determined by the sequence of one or more fluid valves.

[0036] The control unit of the third main embodiment first opens the first and second pneumatic valves and the source fluid valve, causing the air pump to generate negative pressure in the pneumatic pump chamber and the cylinder chamber, drawing the flexible membrane of the fluid pump chamber into the pneumatic pump chamber and new or used PD fluid into the fluid pump chamber. In one embodiment, the control unit monitors the speed of the air pump during the PD fluid drawing phase. When the speed of the air pump begins to slow, the control unit determines that the flexible membrane is fully stretched and expanded, and therefore the fluid pump chamber is full of new or used PD fluid. Once the flexible membrane is fully stretched, the speed of the air pump slows down. The control unit provides closed-loop control to the air pump to maintain the desired pressure. The control loop through the control unit ensures that the pressure does not exceed a set threshold.

[0037] After the fluid pump chamber is completely filled with PD fluid, the control unit closes the source fluid valve. The control unit then opens the first and second pneumatic valves, causing the air pump to generate a desired positive pumping pressure (e.g., 1.5 psig) in the pneumatic pump chamber and cylinder chamber. Once the desired positive pumping pressure is reached, the control unit closes the second pneumatic valve, thereby isolating and shutting off the air pump. The piston head of the piston is now in its initial piston head position.

[0038] The control unit maintains the first pneumatic valve open and opens the destination fluid valve. The desired positive pressure built in the pneumatic pump chamber forces the flexible membrane of the fluid pump chamber to contract, pushing new or used PD fluid to the destination. When the positive pressure dissipates, the control unit moves the piston within the cylinder chamber, causing the pressure sensor to continue reading the desired pressure, e.g., 1.5 psig.

[0039] Eventually, the flexible membrane can no longer contract, causing the pressure sensor reading to spike, at which point the control unit stops the pump-out translation of the piston head and closes the destination fluid valve. The detection that the flexible membrane can no longer contract may alternatively or additionally be determined by the control unit detecting that the linear actuator and / or piston head are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping the pump-out translation, the first pneumatic valve remains open, allowing the positive pressure maintained at the desired pressure to equalize between the cylinder chamber and the pneumatic pump chamber, which can be read by the pressure sensor. The piston head is now in the final piston head position. The volume difference of the known cross-sectional area of ​​the pneumatic cylinder between the final and initial piston head positions is the volume of new PD fluid pumped to the destination when the pressure at the initial and final piston head positions is the same, e.g., 1.5 psig, the desired pump-to-patient pressure.

[0040] The control unit then opens the first and second pneumatic valves and the source fluid valve, moving the piston in the opposite direction within the cylinder to reposition the piston head for the next pump-out stroke. The piston movement creates negative pressure within the cylinder chamber and the pneumatic pump chamber, which can be assisted by an air pump to quickly achieve the desired PD fluid suction pressure. The flexible membrane of the fluid pump chamber is drawn into the pneumatic pump chamber, and new or used PD fluid is correspondingly drawn into the fluid pump chamber. The above process for the third main embodiment is repeated, with the control unit accumulating pump stroke volume until the desired or predetermined amount of new or used PD fluid is delivered to the destination.

[0041] The fourth main embodiment also uses an air pump operating in cooperation with an air cylinder. Here, a single air pump and air cylinder can drive two fluid pump chambers within the two pneumatic pump chambers. The air cylinders of the fourth main embodiment are structured similarly to the third main embodiment, including a piston head and a piston shaft driven by a linear actuator. Optional vent lines and air vent valves may be pneumatically connected to the first and second cylinder chambers of each air cylinder. In the fourth main embodiment, only the first air line extends from the air cylinder, but the first air line is split to include a second air line, where the first and second air lines extend to the first and second pneumatic pump chambers, respectively. First and second air valves, under the control of a control unit, are provided along the first and second air lines, respectively.

[0042] A third pneumatic line extends from the air pump and splits into a fourth pneumatic line. The third pneumatic line intersects with the first pneumatic line, and the fourth pneumatic line intersects with the second pneumatic line. A third pneumatic valve under the control of the control unit is provided along the third pneumatic line, and a fourth pneumatic valve under the control of the control unit is provided along the fourth pneumatic line. A first pressure sensor is provided adjacent to the first pneumatic pump chamber, and a second pressure sensor is provided adjacent to the second pneumatic pump chamber. The first and second fluid pump chambers are provided as part of the disposable set, wherein the first and second fluid pump chambers pump new or used PD fluid from a desired PD fluid source to a desired PD fluid destination as determined by the sequence of the plurality of fluid valves.

[0043] In the pumping sequence of the fourth main embodiment, the first and second fluid pump chambers are generally alternated, where one fluid pump chamber draws in new or used PD fluid while the other fluid pump chamber pushes out new or used PD fluid. Each fluid pump chamber has its own set of source and destination valves, but the first and second fluid pump chambers need not be perfectly synchronized.

[0044] The control unit of the fourth main embodiment first opens the third pneumatic valve and the source fluid valve for the first fluid pump chamber, causing the air pump to generate negative pressure in the first pneumatic pump chamber, drawing the flexible membrane of the first fluid pump chamber into the first pneumatic pump chamber and drawing new or used PD fluid into the first fluid pump chamber. The control unit may also monitor the speed of the air pump during the PD fluid draw phase. When the speed of the air pump begins to decrease beyond a set threshold, the control unit determines that the flexible membrane is fully stretched and expanded, thus filling the fluid pump chamber with new or used PD fluid. At that point, the control unit stops the air pump and closes the source fluid valve for the first fluid pump chamber. The control unit then maintains the third pneumatic valve open, causing the air pump to generate the desired positive pumping pressure in the first pneumatic pump chamber (e.g., 1.5 psig as read by the first pressure sensor). At this point, the piston head of the air cylinder piston is in the initial piston head position.

[0045] The control unit then closes the third pneumatic valve, opens the first pneumatic valve, and opens the first destination fluid valve. The desired positive pressure built up in the first pneumatic pump chamber forces the flexible membrane of the first fluid pump chamber to contract, pushing new or used PD fluid to the destination. When the positive pressure dissipates, the control unit moves the piston within the cylinder chamber, causing the first pressure sensor to continue reading the desired pressure, e.g., 1.5 psig. Simultaneously, the control unit opens the fourth pneumatic valve and the second source valve, causing the air pump to create negative pressure within the second pneumatic pump chamber, drawing the flexible membrane of the second fluid pump chamber into the second pneumatic pump chamber and drawing new or used PD fluid into the second fluid pump chamber.

[0046] Eventually, the first flexible membrane can no longer contract, causing the first pressure sensor reading to spike, at which point the control unit stops the pump-out translation of the piston head and closes the first destination fluid valve. The detection that the flexible membrane can no longer contract may alternatively or additionally be determined by the control unit detecting that the linear actuator and / or piston head are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping the pump-out translation, the first pneumatic valve remains open, allowing the positive pressure maintained at the desired pressure to equalize between the cylinder chamber and the first pneumatic pump chamber, which can be read by the first pressure sensor. The piston head is now at its final piston head position within the cylinder chamber. The volume difference of the known cross-sectional area of ​​the pneumatic cylinder between the final piston head position and the initial piston head position is the volume of new or used PD fluid that will be pumped to the destination when the pressure at the initial and final piston head positions is the same, e.g., 1.5 psig, the desired pump-to-patient pressure. For fluid draw in the second fluid pump chamber, the control unit may again monitor the speed of the air pump. If the speed of the air pump begins to decrease beyond a set threshold, the control unit determines that the flexible membrane of the second fluid pump chamber is fully stretched and expanded, and therefore the second fluid pump chamber is full of new or used PD fluid, at which point the control unit stops the air pump and closes the second source fluid valve for the second fluid pump chamber.

[0047] The control unit then retracts the piston to the initial position and repeats the above process, but now the first fluid pump chamber fills with new or used PD fluid and the second fluid pump chamber pushes the new or used PD fluid to the destination. The control unit continues to accumulate a known stroke volume and perform the alternating pumping sequence just described until the desired or predetermined amount of new or used PD fluid is delivered to the destination.

[0048] Like the fourth main embodiment, the fifth main embodiment also uses an air pump operating in cooperation with an air cylinder to drive two pneumatic pump chambers and corresponding fluid pump chambers. In the fourth main embodiment, the air cylinder is unidirectional in terms of fluid volume metering, as only one side of the piston head within the cylinder is exposed to the first and second pressure sensors. The piston must be reset accordingly after each fluid pump chamber retract / fluid pump chamber delivery sequence. In the fifth main embodiment, a fifth pneumatic line is added extending from the first pneumatic line to the opposite side of the air cylinder, thereby providing pneumatic access to the air cylinders on both sides of the piston head. A fifth pneumatic valve is provided with the fifth pneumatic line. A sixth pneumatic valve is added as a second valve along the first pneumatic line, allowing the air cylinder on that side of the piston head to be closed.

[0049] In a pumping sequence using the fifth main embodiment, the control unit can open the second and fifth pneumatic valves, open the second destination fluid valve, and move the piston head of the air cylinder in a first direction to deliver fresh or used PD fluid from the second fluid pump chamber to a desired destination. Simultaneously, the control unit can open the third pneumatic valve and the first source fluid valve, causing the air pump to apply negative pressure to the flexible membrane of the first fluid pump chamber to draw fresh or used PD fluid into the first fluid pump chamber.

[0050] Eventually, the second flexible membrane can no longer contract, causing the second pressure sensor reading to spike, at which point the control unit stops the pump-out translation of the piston head and closes the second destination fluid valve. The detection that the flexible membrane can no longer contract may alternatively or additionally be determined by the control unit detecting that the linear actuator and / or piston head are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping the pump-out translation, the second and fifth pneumatic valves remain open, allowing the positive pressure maintained at the desired pressure to equalize between the cylinder chamber and the second pneumatic pump chamber, which may be read by the second pressure sensor. The volume difference of the known cross-sectional area of ​​the pneumatic cylinder between the initial and final piston head positions is the volume of new or used PD fluid that will be pumped to the destination when the pressure at the initial and final piston head positions is the same, e.g., 1.5 psig, the desired pump-to-patient pressure. For fluid draw in the first fluid pump chamber, the control unit may again monitor the speed of the air pump. If the speed of the air pump begins to decrease beyond a set threshold, the control unit determines that the flexible membrane of the first fluid pump chamber is fully stretched and expanded, and therefore the first fluid pump chamber is full of new or used PD fluid, at which point the control unit stops the air pump and closes the first source fluid valve for the first fluid pump chamber.

[0051] The first and second fluid pump chambers then switch operation, such that the second fluid pump chamber draws in new or used PD fluid while the first fluid pump chamber delivers new or used PD fluid. Notably, there is no need to adjust the piston head to prepare the air cylinder for the switch. Here, the control unit opens the first and sixth pneumatic valves, opens the first destination fluid valve, and moves the piston head of the air cylinder in a second direction to deliver new or used PD fluid from the first fluid pump chamber to the desired destination. Simultaneously, the control unit opens the fourth pneumatic valve and the second source fluid valve, allowing the air pump to apply negative pressure to the flexible membrane of the second fluid pump chamber, drawing new or used PD fluid into the second fluid pump chamber.

[0052] Eventually, the first flexible membrane can no longer contract, causing the first pressure sensor reading to spike, at which point the control unit stops the pump-out translation of the piston head and closes the first destination fluid valve. The detection that the flexible membrane can no longer contract may alternatively or additionally be determined by the control unit detecting that the linear actuator and / or piston head are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping the pump-out translation, the first and sixth pneumatic valves remain open, allowing the positive pressure maintained at the desired pressure to equalize between the cylinder chamber and the first pneumatic pump chamber, which may be read by the first pressure sensor. The volume difference of the known cross-sectional area of ​​the pneumatic cylinder between the initial and final piston head positions is the volume of new or used PD fluid pumped to the destination when the pressure at the initial and final piston head positions is the same, e.g., 1.5 psig, the desired pump-to-patient pressure. For fluid draw in the second fluid pump chamber, the control unit may again monitor the speed of the air pump. If the speed of the air pump begins to decrease beyond a set threshold, the control unit determines that the flexible membrane of the second fluid pump chamber is fully stretched and expanded, and therefore the second fluid pump chamber is full of new or used PD fluid, at which point the control unit stops the air pump and closes the second source fluid valve for the second fluid pump chamber.

[0053] The control unit accumulates the known stroke volume and continues to perform the alternating pumping sequence just described until the desired or predetermined amount of new or used PD fluid is delivered to the destination. It should be understood that in any of the above main embodiments, for destinations of new or used PD fluid that do not contain a patient (e.g., a heater bag or drain), the delivery pressure may be higher, e.g., up to 8 psig. It is also contemplated that in any of the main embodiments, when either the air cylinder or air pump is removing used PD fluid from the patient, the control unit monitors the associated first or second pressure sensor to ensure that a patient drain negative pressure limit, e.g., −1.5 psig, is not met or exceeded.

[0054] It should be understood that the effects of air pressure sensor drift in the above embodiments are negated because the important aspect of the above air cylinder sequence is that the initial and final pressures associated with fresh or used PD fluid delivery are equal, not that the pressure be precise in absolute terms (except for the patient's pumping pressure limit). Also, because the system is pressure controlled, the linear actuator does not need to be highly accurate.

[0055] In a first aspect of the present disclosure, which may be combined with any other aspect or portion thereof in light of the disclosure set forth herein and without limiting the present disclosure in any way, a peritoneal dialysis system includes a pneumatic pump chamber, a cylinder, a piston including a piston head slidably sealed within the cylinder, the piston head separating a first cylinder chamber from a second cylinder chamber, a piston, a linear actuator in mechanical communication with the piston, a first pneumatic line extending between the first cylinder chamber and the pneumatic pump chamber, a second pneumatic line extending between the second cylinder chamber and the pneumatic pump chamber, a first pneumatic valve located along the first pneumatic line, a second pneumatic valve located along the second pneumatic line, a pressure sensor positioned and arranged to measure pressure in the pneumatic pump chamber, a fluid pump chamber operatively coupled to the pneumatic pump chamber, a source fluid valve, a destination fluid valve, and a control unit, a control unit configured to: (i) open the second pneumatic valve and the source fluid valve, and cause the linear actuator to move a piston head into the first cylinder chamber, thereby generating a negative air pressure in the second cylinder chamber and the pneumatic pump chamber to draw source fluid into the fluid pump chamber; and (ii) close the second pneumatic valve and the source fluid valve, and open the first pneumatic valve and the destination fluid valve, and cause the linear actuator to move the piston head further into the first cylinder chamber, thereby forcing source fluid into the destination fluid valve, wherein the control unit uses an output from the pressure sensor to control the linear actuator so that the final pressure in (ii) is at least substantially equal to the initial pressure in (ii), whereby a volume of space corresponding to the movement of the piston head within the cylinder during (ii) is equal to a volume of source fluid delivered from said fluid pump chamber during (ii). Includes.

[0056] In a second aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the source fluid valve is for a PD fluid supply container, a heating container, or a patient line.

[0057] In a third aspect of the present disclosure that may be combined with any other aspect or portion thereof, the destination fluid valve is for a heating vessel, a drain vessel, or a patient line.

[0058] In a fourth aspect of the present disclosure that may be combined with any other aspect or portion thereof, the volume of space corresponding to the movement of the piston head within the cylinder is a function of the distance moved by the piston head within the cylinder and the cross-sectional area of ​​the inner diameter of the cylinder.

[0059] In a fifth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the control unit is configured to determine a volume of source fluid delivered from the fluid pump chamber during (ii) with both the source fluid valve and the destination fluid valve closed.

[0060] In a sixth aspect of the present disclosure that may be combined with any other aspect or portion thereof, the control unit is further configured to: (iii) with the first pneumatic valve and the destination fluid valve closed, open the second pneumatic valve and the source fluid valve to allow negative air pressure in the second cylinder chamber generated during at least one of (i) or (ii) to reach the pneumatic pump chamber and draw the source fluid into the fluid pump chamber.

[0061] In a seventh aspect of the present disclosure that may be combined with any other aspect or portion thereof, the control unit is further configured to: (iv) generate at least substantially zero pressure in the first cylinder chamber and the second cylinder chamber by causing the linear actuator to move the piston head into the second cylinder chamber, when the first pneumatic valve, the source fluid valve, and the destination fluid valve are closed and the second pneumatic valve is closed.

[0062] In an eighth aspect of the present disclosure that may be combined with any other aspects or portions thereof, the control unit is further configured to (v) open the second pneumatic valve and the destination fluid valve and cause the linear actuator to move the piston head into the second cylinder chamber, thereby pushing the source fluid into the destination fluid valve, wherein the control unit controls the linear actuator using the output from the pressure sensor to make the final pressure of (v) at least substantially equal to the initial pressure of (v), such that the volume of space corresponding to the movement of the piston head in the cylinder during (v) is equal to the volume of source fluid delivered from the fluid pump chamber during (v).

[0063] In a ninth aspect of the present disclosure that may be combined with any other aspect or portion thereof, the control unit is further configured to, with the second pneumatic valve and the destination fluid valve closed, open the first pneumatic valve and the source fluid valve to allow the negative air pressure in the first cylinder chamber generated during (vi)(v) to reach the pneumatic pump chamber and draw the source fluid into the fluid pump chamber.

[0064] In a tenth aspect of the present disclosure that may be combined with any other aspect or a portion thereof, a peritoneal dialysis system includes a pneumatic pump chamber, a cylinder, a piston including a piston head slidably sealed within the cylinder, a linear actuator in mechanical communication with the piston, an air pump, a first air pressure line extending between the cylinder and the pneumatic pump chamber, a second air pressure line extending between the air pump and the pneumatic pump chamber, a first air pressure valve located along the first air pressure line, a second air pressure valve located along the second air pressure line, a pressure sensor positioned and arranged to measure pressure in the pneumatic pump chamber, a fluid pump chamber operatively coupled to the pneumatic pump chamber, a source fluid valve, a destination fluid valve, and a control unit that (i) causes the second air pressure valve and the source fluid valve to open, causing the air pump to generate a negative air pressure in the pneumatic pump chamber , drawing the source fluid into the fluid pump chamber; (ii) causing the air pump to create a desired positive pressure in the air pump chamber as measured by the pressure sensor with the source fluid valve closed and the second pneumatic valve open; and (iii) causing the second pneumatic valve to close and the first pneumatic valve and the destination fluid valve to open and cause the linear actuator to move a piston head within the cylinder to push the source fluid into the destination fluid valve, wherein the control unit uses output from the pressure sensor to control the linear actuator so that the final pressure in (iii) is at least substantially equal to the initial pressure in (iii), whereby a volume of space corresponding to the movement of the piston head within the cylinder during (iii) is equal to a volume of source fluid delivered from the fluid pump chamber during (iii).

[0065] In an eleventh aspect of the present disclosure that may be combined with any other aspect or portion thereof, the source fluid valve is for a PD fluid supply container, a heating container, or a patient line.

[0066] In a twelfth aspect of the present disclosure that may be combined with any other aspect or portion thereof, the destination fluid valve is for a heating vessel, a drain vessel, or a patient line.

[0067] In a thirteenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, the volume of space corresponding to the movement of the piston head within the cylinder is a function of the distance moved by the piston head within the cylinder and the cross-sectional area of ​​the inner diameter of the cylinder.

[0068] In a fourteenth aspect of the present disclosure that may be combined with any other aspect or a portion thereof, during (i), the first pneumatic valve is open.

[0069] In a fifteenth aspect of the present disclosure that may be combined with any other aspect or portion thereof, the control unit is further configured to: (iv) cause the linear actuator to move the piston head in the cylinder in an opposite direction to draw the source fluid into the fluid pump chamber when the first pneumatic valve and the source fluid valve are open.

[0070] In a sixteenth aspect of the present disclosure, which may be combined with any other aspect or portion thereof, during (iv), the first pneumatic valve is opened and the air pump is activated to assist in drawing the source fluid into the fluid pump chamber.

[0071] In a seventeenth aspect of the present disclosure that may be combined with any other aspect or a portion thereof, a peritoneal dialysis system includes a first pneumatic pump chamber, a second pneumatic pump chamber, a cylinder, a piston including a piston head slidably sealed within the cylinder, a linear actuator in mechanical communication with the piston, an air pump, a first pneumatic line extending between the cylinder and the first pneumatic pump chamber, a second pneumatic line extending between the cylinder and the second pneumatic pump chamber, a third pneumatic line extending between the air pump and the first pneumatic pump chamber, a fourth pneumatic line extending between the air pump and the second pneumatic pump chamber, a first pneumatic valve located along the first pneumatic line, a second pneumatic valve located along the second pneumatic line, a third pneumatic valve located along the first pneumatic line, a fourth pneumatic valve located along the fourth pneumatic line, and an arrangement positioned to measure pressure in the first pneumatic pump chamber. the first pneumatic pump chamber; a first pressure sensor positioned and arranged to measure pressure in the second pneumatic pump chamber; a first fluid pump chamber operatively coupled to the first pneumatic pump chamber; a first source fluid valve for the first pump chamber; a first destination fluid valve for the first pump chamber; a second fluid pump chamber operatively coupled to the first pneumatic pump chamber; a second source fluid valve for the second pump chamber; and a control unit configured to: use an air pump to generate negative and positive air pressures in the first and second pneumatic pump chambers; and actuate a linear actuator to move a piston head within the cylinder while equalizing initial and final positive air pressures to meter a determinable volume of source fluid through the first and second destination fluid valves.

[0072] In an eighteenth aspect of the present disclosure that may be combined with any other aspect or a portion thereof, the control unit (i) causes the air pump to generate a negative air pressure in the first air pressure pump chamber with the third air pressure valve and the first source fluid valve open to draw source fluid into the first fluid pump chamber; (ii) causing the third pneumatic valve to open and the first source fluid valve to close, causing the air pump to generate a desired positive air pressure in the first pneumatic pump chamber as measured by the first pressure sensor; and (iii) causing the linear actuator to move a piston head within a cylinder to force source fluid into the first destination fluid valve, with the first pneumatic valve and the first destination fluid valve open, wherein the control unit uses the output from the first pressure sensor to control the linear actuator so that the final pressure in (iii) is at least substantially equal to the initial pressure in (iii), whereby a volume of space corresponding to the movement of the piston head within the cylinder during (iii) is equal to the volume of source fluid delivered from the first fluid pump chamber during (iii); and causing the air pump to generate a negative air pressure in the second pneumatic pump chamber to draw source fluid into the second fluid pump chamber, with the fourth pneumatic valve and the second source fluid valve open.

[0073] In a nineteenth aspect of the present disclosure that may be combined with any other aspect or a portion thereof, the control unit is further configured, with the piston head moved to the retracted position, to: (iv) cause the air pump to generate a desired positive air pressure in the second air pressure pump chamber as measured by the first pressure sensor with the fourth air pressure valve open and the second source fluid valve closed; and (v) cause the linear actuator to move the piston head within the cylinder to push the source fluid into the second destination fluid valve with the second air pressure valve and the second destination fluid valve open. , wherein the control unit uses the output from the second pressure sensor to control the linear actuator so that the final pressure of (v) is at least substantially equal to the initial pressure of (v), so that the volume of space corresponding to the movement of the piston head within the cylinder during (v) is equal to the volume of source fluid delivered from the second fluid pump chamber during (v), and with the third pneumatic valve and the first source fluid valve open, the air pump generates negative air pressure in the first pneumatic pump chamber to draw the source fluid into the first fluid pump chamber.

[0074] In a twentieth aspect of the present disclosure that may be combined with any other aspect or portion thereof, a peritoneal dialysis system includes a first pneumatic pump chamber, a second pneumatic pump chamber, a cylinder, a piston including a piston head slidably sealed within the cylinder, the piston head separating the first cylinder chamber from the second cylinder chamber, the piston, a linear actuator in mechanical communication with the piston, an air pump, a first pneumatic line extending between the second cylinder chamber and the first pneumatic pump chamber, and a second pneumatic pump chamber. a second pneumatic line extending between the second cylinder chamber and the second pneumatic pump chamber; a third pneumatic line extending between the air pump and the first pneumatic pump chamber; a fourth pneumatic line extending between the air pump and the second pneumatic pump chamber; a fifth pneumatic line extending between the first cylinder chamber and the first pneumatic line; a first pneumatic valve located along the first pneumatic line; a second pneumatic valve located along the second pneumatic line; a third pneumatic valve located along the third pneumatic line; and a fourth pneumatic valve. a fourth pneumatic valve located along the pneumatic line; a fifth pneumatic valve located along the fifth pneumatic line; a sixth pneumatic valve located adjacent to the second cylinder chamber; a first pressure sensor positioned and arranged to measure pressure in the first pneumatic pump chamber; a second pressure sensor positioned and arranged to measure pressure in the second pneumatic pump chamber; a first fluid pump chamber operatively coupled to the first pneumatic pump chamber; a first source fluid valve for the first pump chamber; a first destination fluid valve for the first pneumatic pump chamber, a second fluid pump chamber operatively coupled to the first pneumatic pump chamber, a second source fluid valve for the second pump chamber, and a second destination fluid valve for the second pump chamber; and a control unit, using an air pump to generate negative and positive air pressures in the first pneumatic pump chamber and the second pneumatic pump chamber, while equalizing the initial and final positive air pressures to meter a determinable volume of source fluid through the first destination fluid valve and the second destination fluid valve.and a control unit configured to actuate the linear actuator to move the piston head within the first cylinder chamber and the second cylinder chamber.

[0075] In a twenty-first aspect of the present disclosure that may be combined with any other aspects or portions thereof, the control unit is configured to: (i) with the third pneumatic valve and the first source fluid valve open, cause the air pump to generate negative air pressure in the first pneumatic pump chamber to draw source fluid into the first fluid pump chamber; and with the second pneumatic valve, the fifth pneumatic valve, and the second destination fluid valve open, cause the linear actuator to move a piston head toward the first cylinder chamber to push the source fluid into the second destination fluid valve, wherein the control unit controls the linear actuator using output from the second pressure sensor so that the final pressure of (i) is at least substantially equal to the initial pressure of (i), whereby the volume of space corresponding to the movement of the piston head toward the first cylinder chamber during (i) is equal to the volume of source fluid delivered from the second fluid pump chamber during (i).

[0076] In a twenty-second aspect of the present disclosure that may be combined with any other aspects or portions thereof, the control unit is further configured to: (ii) with the fourth pneumatic valve and the second source fluid valve open, cause the air pump to generate negative air pressure in the second pneumatic pump chamber to draw the source fluid into the second fluid pump chamber; and with the first pneumatic valve, the sixth pneumatic valve, and the first destination fluid valve open, cause the linear actuator to move the piston head toward the second cylinder chamber to push the source fluid into the first destination fluid valve, wherein the control unit controls the linear actuator using the output from the first pressure sensor so that the final pressure of (ii) is at least substantially equal to the initial pressure of (ii), whereby the volume of the space corresponding to the movement of the piston head toward the second cylinder chamber during (ii) is equal to the volume of source fluid delivered from the second fluid pump chamber during (ii).

[0077] In a twenty-third aspect which may be combined with any other aspect or portion thereof, any of the features, functions, and alternatives described in connection with any one or more of Figures 1-28 may be combined with any of the features, functions, and alternatives described in connection with any other of Figures 1-28.

[0078] Thus, an advantage of the present disclosure is to provide a relatively volumetrically accurate automated peritoneal dialysis ("PD") machine.

[0079] Another advantage of the present disclosure is that it provides a PD machine that achieves relatively precise pressure control.

[0080] A further advantage of the present disclosure is that it provides a relatively quiet PD machine.

[0081] Yet another advantage of the present disclosure is that it provides an accurate PD machine independent of pressure sensor drift due to time, temperature, humidity, etc.

[0082] Yet another advantage of the present disclosure is to provide a PD machine that removes the dependency of spatial accuracy on absolute pressure sensing.

[0083] Yet another advantage of the present disclosure is that it provides a PD system that uses both low-cost, simple machinery and low-cost, simple disposable items.

[0084] Additional features and advantages are described in and will be apparent from the following detailed description and drawings. The features and advantages described herein are not all-inclusive, and in particular, many additional features and advantages will be apparent to those skilled in the art upon consideration of the drawings and description. Moreover, it is not necessary for any particular embodiment to possess all of the advantages enumerated herein, and it is expressly contemplated that each advantageous embodiment may be separately claimed. Furthermore, it should be noted that the language used herein has been selected primarily for readability and instructional purposes, and not to limit the scope of the inventive subject matter. [Brief explanation of the drawings]

[0085] [Figure 1] FIG. 1 is a schematic elevation view of one embodiment of a peritoneal dialysis ("PD") system of the present disclosure.

[0086] [Figure 2] 2 and 3 are schematic diagrams of a first main embodiment of the disclosed PD system that uses an air cylinder. [Figure 3] 2 and 3 are schematic diagrams of a first main embodiment of the disclosed PD system that uses an air cylinder.

[0087] [Figure 4] 4-13 are schematic diagrams of a second main embodiment of the PD system of the present disclosure that uses an air cylinder. [Figure 5] 4-13 are schematic diagrams of a second main embodiment of the PD system of the present disclosure that uses an air cylinder. [Figure 6]4-13 are schematic diagrams of a second main embodiment of the PD system of the present disclosure that uses an air cylinder. [Figure 7] 4-13 are schematic diagrams of a second main embodiment of the PD system of the present disclosure that uses an air cylinder. [Figure 8] 4-13 are schematic diagrams of a second main embodiment of the PD system of the present disclosure that uses an air cylinder. [Figure 9] 4-13 are schematic diagrams of a second main embodiment of the PD system of the present disclosure that uses an air cylinder. [Figure 10] 4-13 are schematic diagrams of a second main embodiment of the PD system of the present disclosure that uses an air cylinder. [Figure 11] 4-13 are schematic diagrams of a second main embodiment of the PD system of the present disclosure that uses an air cylinder. [Figure 12] 4-13 are schematic diagrams of a second main embodiment of the PD system of the present disclosure that uses an air cylinder. [Figure 13] 4-13 are schematic diagrams of a second main embodiment of the PD system of the present disclosure that uses an air cylinder.

[0088] [Figure 14] 14-20 are schematic diagrams of a third main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 15] 14-20 are schematic diagrams of a third main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 16] 14-20 are schematic diagrams of a third main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 17] 14-20 are schematic diagrams of a third main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 18]14-20 are schematic diagrams of a third main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 19] 14-20 are schematic diagrams of a third main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 20] 14-20 are schematic diagrams of a third main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump.

[0089] [Figure 21] 21-24 are schematic diagrams of a fourth main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 22] 21-24 are schematic diagrams of a fourth main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 23] 21-24 are schematic diagrams of a fourth main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 24] 21-24 are schematic diagrams of a fourth main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump.

[0090] [Figure 25] 25-28 are schematic diagrams of a fifth main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 26] 25-28 are schematic diagrams of a fifth main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 27] 25-28 are schematic diagrams of a fifth main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. [Figure 28] 25-28 are schematic diagrams of a fifth main embodiment of the PD system of the present disclosure, which uses an air cylinder and air pump. DETAILED DESCRIPTION OF THE INVENTION

[0091] Detailed Description Referring now to the drawings, and particularly to FIG. 1 , an automated peritoneal dialysis (“PD”) system 10 includes a PD machine or cycler 20 operating in conjunction with a disposable set 110. The disposable set 110 includes or defines at least one fluid pump chamber 112 a, 112 b, which may comprise, for example, two flexible sheets welded together to form a spherically expandable circular chamber. Alternatively, the at least one fluid pump chamber 112 a, 112 b may comprise a single flexible sheet welded to a rigid, hemispherical pump shell. All welds described herein may be by heat sealing, ultrasonic sealing, or solvent bonding.

[0092] The disposable set 110 also includes or defines a plurality of new and used PD fluid lines, such as a heater line 114a, a drain line 114b, PD fluid supply lines 114c, 114d, 114e, a patient line 114f, and a fluid pump chamber line 114g. The new and used PD fluid lines may be formed by tubing, by welding paths between two flexible sheets, or by molding paths into a rigid cassette.

[0093] The disposable set 110 further includes multiple PD fluid containers, such as a heating container 116a, a drain container 116b, and PD fluid supply containers 116c, 116d, and 116e. In the illustrated embodiment, the heating container 116a is located on a heating tray atop the housing 22 of the PD machine or cycler 20. A batch heater 24, such as an electrical resistance heater, under the control of the control unit 100 is provided on top of the PD machine or cycler 20. In an alternative embodiment, the first of the supply containers 116c, 116d, and 116e is placed on the heating tray and then, once empty, is used as the heating container for the remainder of the treatment. In a further alternative embodiment, the heater 24 may instead be an in-line heater operating, for example, on the patient line 114f, thereby eliminating the heating container 116a. In either case, the control unit 100 is programmed to cause the heater 24 to heat the new PD fluid to the patient temperature, for example, 37°C.

[0094] Any desired number and size of PD fluid supply containers 116c, 116d, and 116e may be provided and may hold PD fluids with the same or different dextrose or glucose levels. One of the PD fluid supply containers 116c, 116d, and 116e may be the final fill container and may contain a different PD formulation, such as icodextrin. Additionally, drain line 114b may instead lead to a house drain, such as a toilet or bathtub, in which case drain container 116b is not necessary. Any of containers 116a-116a may be formed as a flexible container or bag.

[0095] The disposable set 110 in the illustrated embodiment further includes multiple fluid valve seats, such as a heater valve seat 118a, a drain valve seat 118b, PD fluid supply valve seats 118c, 118d, and 118e, a patient valve seat 118f, and a fluid pump chamber valve seat 118g. The fluid valve seats 118a-118g may be tubing positions formed by welding two flexible sheets together or by molding within a rigid cassette. The fluid valve seats 118a-118g are operated by valve actuators (not visible in FIG. 1), which may be magnetically actuated solenoid pinch valve actuators, motorized pinch valves, or pneumatically actuated valve actuators.

[0096] In system 10, as described in more detail below, supply vessels 116c, 116d, and 116e are new fluid sources ("FS"), but can be new PD fluid destinations when used as heating vessels. Drain vessel 116b is a spent PD fluid destination ("FD"). Heating vessel 116a is a new PD fluid source ("FS") and a new PD fluid destination ("FD"). Patient line 114f (patient) is a spent PD fluid source ("FS") and a new PD fluid destination ("FD").

[0097] In system 10, as described in detail below, PD fluid supply valve seats 118c, 118d, and 118e are source fluid valves (“SV”), but can be destination fluid valves (“DV”) when used as heater valves. Drain valve seat 118b is a destination fluid valve (“DV”). Heater valve seat 118a and patient valve seats are source fluid valves (“SV”) and destination fluid valves (“DV”). Fluid pump chamber valve seat 118g allows fluid pump chambers 112a, 112b to alternately draw in or pump new or used PD fluid, depending on the current pumping sequence, so that flow to the desired destination is relatively continuous.

[0098] Any rigid components of the disposable set 110 may be made of plastic, such as polyvinyl chloride ("PVC"), polyethylene ("PE"), polyurethane ("PU"), or polycarbonate ("PC"). Any flexible components of the disposable set 110, such as the membranes or diaphragms, tubing, and containers discussed herein, may be made of a medically safe material, such as one or more plastics, for example, PVC, PE, PU, ​​or other suitable non-PVC polymers. The rigid pump housing 22, the air cylinders and associated components discussed herein, and the pneumatic lines discussed herein are reusable in one embodiment and may be made of plastic, such as polyvinyl chloride ("PVC"), polyethylene ("PE"), or polyurethane ("PU"), or metal, such as stainless steel or aluminum, and combinations thereof.

[0099] First Main Embodiment In a first primary embodiment of the system 10, as shown in FIGS. 2 and 3, an air cylinder 30 is provided. The air cylinder 30 resides between first and second pneumatic pump chambers 70a, 70b, which operate in conjunction with fluid pump chambers 112a, 112b, respectively, of the disposable set 110. A piston 32 is located within the air cylinder 30 and includes a piston shaft 34 and a piston head 36 that separates the air cylinder 30 into a first cylinder chamber 30a and a second cylinder chamber 30b. The piston shaft 34 and piston head 36 in the illustrated embodiment are driven by a linear actuator 40. The linear actuator 40 may include a motor, such as a stepper motor, driving a rotary-translation device, such as a lead or ball screw. Alternatively, the linear actuator 40 may be pneumatically driven. In either case, the piston shaft 34 is coupled outside the air cylinder 30 to the linear actuator 40 for translating the piston shaft and piston head 36 within the cylinder.

[0100] A first pneumatic line 42a extends from the first cylinder chamber 30a to the first pneumatic pump chamber 70a. A second pneumatic line 42b extends from the second cylinder chamber 30b to the second pneumatic pump chamber 70b. A first pressure sensor 44a is positioned to read the air pressure in the first pneumatic line 42a, the first pneumatic pump chamber 70a, and the first cylinder chamber 30a. A second pressure sensor 44b is positioned to read the air pressure in the second pneumatic line 42b, the second pneumatic pump chamber 70b, and the second cylinder chamber 30b.

[0101] An optional first vent line 46a and associated first vent valve 48a are disposed in fluid communication with the first cylinder chamber 30a. An optional second vent line 46b and associated second vent valve 48b are disposed in fluid communication with the second cylinder chamber 30b.

[0102] All fluid valve actuators (which drive fluid valve seats 118a-118g), motors or other drivers for linear actuator 40, PD fluid heater 24, and other controllable electrical devices are under the control of control unit 100, which includes at least one processor 102, at least one memory 104, and a video controller 106 for controlling a user interface 108 (which may be coupled to cycler 20 as shown or may be a wireless user interface). The control unit is further configured to receive signals from all sensors, such as all air pressure sensors (e.g., 44a, 44b), fluid pressure sensors (if provided), motor encoders (or other positioning mechanisms for linear actuator 40), and any temperature sensors associated with heater 24. Control unit 100 may also include a transceiver (not shown) and a wired or wireless connection to a network, e.g., the Internet, for transmitting treatment data to and receiving prescription orders from a physician or clinician's server that interfaces with a physician or clinician's computer. The user interface 108 may include a display screen operated by one or more electromechanical buttons, such as a touch screen and / or membrane switches, and may include one or more speakers for outputting alerts, warnings, and / or voice guidance commands.

[0103] To achieve the desired new or used PD fluid pumping sequence described herein, the control unit 100 may feed the difference between the commanded pressure and the pressure measured by an associated pressure sensor, e.g., pressure sensors 44a, 44b, to a control algorithm, e.g., a proportional-integral-derivative (“PID”) algorithm, which attempts to reduce the difference between the commanded pressure and the measured pressure to zero, resulting in an output to an electronic motor driver in one example of the linear actuator 40. The control algorithm analysis is performed at some periodic frequency in each of the main embodiments of the system 10 described herein. The control unit 100 is programmed to execute all of the pumping sequences discussed herein, including the sequence of the first main embodiment discussed next.

[0104] As shown in FIGS. 2 and 3, the PD machine or cycler 20 operates a disposable set 110. Among other items, the disposable set 110 includes first and second fluid pump chambers 112a, 112b that operate in conjunction with first and second pneumatic pump chambers 70a, 70b, respectively. When the piston head 36 is moved to create negative air pressure in the first or second cylinder chamber 30a, 30b, a corresponding negative pressure is created in the respective first or second pneumatic pump chamber 70a, 70b. The negative pressure created in the first or second pneumatic pump chamber 70a, 70b then draws the flexible membrane of the corresponding first or second fluid pump chamber 112a, 112b into the first or second pneumatic pump chamber 70a, 70b, thereby filling the fluid pump chamber with new or used PD fluid. When the piston head 36 is moved to create positive air pressure in the first or second cylinder chamber 30a, 30b, a corresponding positive pressure is created in the respective first or second pneumatic pump chamber 70a, 70b. The positive pressure created in the first or second pneumatic pump chamber 70a, 70b then pushes against the flexible membrane of the corresponding first or second fluid pump chamber 112a, 112b, causing the fluid pump chamber 112a, 112b to close and dispense new or used PD fluid.

[0105] The control unit 100 of the first main embodiment causes the piston shaft 34 to translate the piston head 36 back and forth within the air cylinder 30, such that in one half-stroke (i), the first pump chamber 112a fills with fresh or used PD fluid and the second fluid pump chamber 112b expels fresh or used PD fluid. In the second half-stroke (ii), the second pump chamber 112b fills with fresh or used PD fluid and the first fluid pump chamber 112a expels fresh or used PD fluid. The control unit 100 translates the piston head 36 back and forth in the manner described above until a desired or predetermined volume of fresh or used PD fluid is delivered from the desired PD fluid source to the desired PD fluid destination. Fluid valves are provided and sequentially actuated by the control unit 100 to access the desired fluid source and the desired fluid destination. The fluid valves may again be magnetically actuated solenoid valves, electrically operated pinch valves, pneumatically actuated valves, or the like.

[0106] In the first primary embodiment, when patient pumping is occurring where pressure control is important, the control unit 100 monitors the outputs from the first and second pressure sensors 44a, 44b while the piston head 36 is translated back and forth. The control unit 100 controls the rate of back and forth translation so as not to exceed a desirable and safe negative or positive fluid pumping pressure (e.g., −1.5 psig, 1.5 to 3.0 psig).

[0107] In the first main embodiment, the amount of new or used PD fluid delivered to the destination is determined by maintaining a constant pressure before and after movement of the piston head 36, which counteracts the effects of the compressibility of the air in the cylinder 30. Because the pressure after movement (P2) is equal to the pressure before movement (P1), the volume of air in the cylinder 30 remains constant. Therefore, the volume displaced by the piston head 36 is equal to the volume of fluid delivered.

[0108] Second Main Embodiment 4-13 illustrate a second main embodiment of the system 10, in which only air cylinders 30 are provided as described above, but the air cylinders are dedicated to a single air pump chamber 70a, 70b / fluid pump chamber pair 112a, 112b. Two air pump chamber / fluid pump chamber pairs may be provided (pair 70a, 112a shown as an example), with each pair having its own dedicated air cylinder 30. The air cylinder 30 is structured similarly to the first main embodiment, including a piston 32 having a piston head 36 and a piston shaft 34 driven by a linear actuator 40. Optional vent lines 46a, 46b and pneumatic vent valves 48a, 48b may be in pneumatic communication with the first and second cylinder chambers 30a, 30b of each air cylinder 30.

[0109] In the second main embodiment, first and second pneumatic lines 56a, 56b extend from the first and second cylinder chambers 30a, 30b, respectively, to the same pneumatic pump chamber 70a. First and second pneumatic valves 58a, 58b, under the control of a control unit 100, are provided along the first and second pneumatic lines 56a, 56b. One or more pressure sensors 44a are provided along a common portion of the first and second pneumatic lines 56a, 56b or along each of the first and second pneumatic lines. Fluid pump chambers 112a, 112b are again provided as part of the disposable set 110, where the fluid pump chamber 112a pumps fresh or used PD fluid from a desired PD fluid source FS to a desired destination FD, as determined by the sequence of a fluid source valve SV and a fluid destination valve DV.

[0110] 4 shows that the control unit 100 of the second main embodiment causes the piston shaft 34 to translate the piston head 36 toward the first cylinder chamber 30a, creating positive pressure in the first cylinder chamber 30a and negative pressure in the second cylinder chamber 30b. The control unit 100 also causes the source fluid valve SV and the second pneumatic valve 58b to open, allowing negative pressure to reach the pneumatic pump chamber 70a, drawing the flexible membrane of the fluid pump chamber 112a into the pneumatic pump chamber 70a and filling it with new or used PD fluid.

[0111] 5 shows that the control unit 100 closes the source fluid valve SV and the second pneumatic valve 58b and opens the first pneumatic valve 58a, allowing the pressure sensor 44a to read a positive pressure in the first cylinder chamber 30a. The control unit 100 also moves the piston 32 into the first cylinder chamber 30a, causing the positive pressure in the pneumatic pump chamber 70a to read a desired pressure, e.g., 1.5 psig, for pumping new or used PD fluid to the desired destination FD. At the end of such movement, the piston head 36 is in the initial piston head position.

[0112] 6 shows that the control unit 100 maintains the first pneumatic valve 58a open and opens the destination fluid valve DV. The desired positive pressure built in the pneumatic pump chamber 70a forces the flexible membrane of the fluid pump chamber 112a to contract, pushing new or used PD fluid to the desired destination FD. When the positive pressure dissipates, the control unit 100 moves the piston 32 further into the first cylinder chamber 30a, causing the pressure sensor 44a to continue to read the desired pressure, e.g., 1.5 psig.

[0113] FIG. 7 shows that eventually, the flexible membrane can no longer contract, causing the pressure sensor 44a reading to spike, at which point the control unit 100 stops the pump-out translation of the piston head 36 and closes the destination fluid valve DV. The detection that the flexible membrane can no longer contract may alternatively or additionally be determined by the control unit 100 detecting that the linear actuator 40 and / or piston head 36 are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping the pump-out translation, the first pneumatic valve 58a remains open, allowing the positive pressure maintained at the desired pressure to equalize between the first cylinder chamber 30a and the pneumatic pump chamber 70a, which can be read by the pressure sensor 44a. The piston head 36 is now in its final piston head position. The volume difference of a known cross-sectional area of ​​the air cylinder 30 between the final piston head position and the initial piston head position is the volume of new or used PD fluid that will be pumped to the desired destination FD as determined by the control unit 100, with the pressure at the initial and final piston head positions being the same, e.g., 1.5 psig, which is the desired pump-to-patient pressure. That is, the volume of space corresponding to the movement of the piston head 36 within the cylinder 30 is a function of the distance moved by the piston head within the cylinder and the cross-sectional area of ​​the cylinder's inner diameter (which is essentially the same as the circular area of ​​the piston head 36).

[0114] FIG. 8 shows that with the second cylinder chamber 30b still under negative pressure (which is not critical when pulling from a non-patient source), the control unit 100 causes the source fluid valve SV and the second pneumatic valve 58b to open, allowing the negative pressure to reach the pneumatic pump chamber 70a, drawing the flexible membrane of the fluid pump chamber 112a into the pneumatic pump chamber 70a and filling it with new or used PD fluid.

[0115] 9 shows that the control unit 100 then closes the source fluid valve SV but leaves the second pneumatic valve 58b open, thereby leaving the pneumatic pump chamber 70a and the second cylinder chamber 30b exposed to the pressure sensor 44a. The control unit 100 translates the piston 32 into the second cylinder chamber 30b until the pressure sensor 44a reads 0 psig. The pressure in the first cylinder chamber 30a should also be close to 0 psig.

[0116] 10 shows that the control unit 100 then moves the piston 32 into the second cylinder chamber 30b with the source fluid valve SV and destination fluid valve DV closed, the first pneumatic valve 58a closed, and the second pneumatic valve 58b open so that the pressure sensor 44a reads the positive pressure in the second cylinder chamber 30b, so that the positive pressure in the pneumatic pump chamber 70a again reads the desired pressure, e.g., 1.5 psig, for pumping fresh or used PD fluid to the desired destination FD. At the end of such movement, the piston head 36 is again in the initial piston head position.

[0117] 11 shows that the control unit 100 then maintains the second pneumatic valve 58b open and opens the destination fluid valve DV. The desired positive pressure built in the pneumatic pump chamber 70a again forces the flexible membrane of the fluid pump chamber 112a to contract, pushing new or used PD fluid to the desired destination FD. When the positive pressure dissipates, the control unit 100 moves the piston 32 further into the second cylinder chamber 30b, causing the pressure sensor 44a to continue to read the desired pressure, e.g., 1.5 psig.

[0118] FIG. 12 shows that eventually, the flexible membrane is no longer able to contract, causing the pressure sensor 44a reading to spike, at which point the control unit 100 stops the pump-out translation of the piston head 36 and closes the destination fluid valve DV. The detection that the flexible membrane is no longer able to contract may alternatively or additionally be determined by the control unit 100 detecting that the linear actuator 40 and / or piston head 36 are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping the pump-out translation, the second pneumatic valve 58b remains open, allowing the positive pressure maintained at the desired pressure to equalize between the first cylinder chamber 30a and the pneumatic pump chamber 70a, which may be read by the pressure sensor 44a. The piston head 36 is now in its final piston head position. The volume difference of the known cross-sectional area of ​​the air cylinder 30 between the final piston head position and the initial piston head position is again the volume of new or used PD fluid that will be pumped to the desired destination as calculated by the control unit 100, with the pressure at the initial and final piston head positions being the same, e.g., 1.5 psig, which is the desired pump-to-patient pressure.

[0119] FIG. 13 shows that with first cylinder chamber 30a still under negative pressure (which is not critical when pulling from a non-patient source), control unit 100 causes source fluid valve SV and first pneumatic valve 58a to open, allowing negative pressure to reach pneumatic pump chamber 70a, drawing the flexible membrane of fluid pump chamber 112a into pneumatic pump chamber 70a and filling it with fresh or used PD fluid. The above process is repeated until the desired amount of fresh or used PD fluid is delivered to the desired destination FD. It should be understood that the above process may be used with any fresh or used PD fluid source FS described herein and any fresh or used PD fluid destination FD described herein, and both the aspiration and delivery pressures and the delivered PD fluid volume may be controlled and measured, respectively.

[0120] Third Main Embodiment 14-20 illustrate a third primary embodiment of the system 10, incorporating an air pump 80 operating in concert with the air cylinder 30. Air pumps generally can transition more quickly from pumping positive pressure to pumping negative pressure and vice versa. They also allow a smaller air pump to generate a wider range of pressures. These two advantages of the air pump 80 are combined with the ability of the air cylinder 30 to meter a known volume of fluid under pressure control as described herein.

[0121] The pneumatic cylinders 30 of the third embodiment are structured substantially similarly to the first and second main embodiments and include a piston head 36 and a piston shaft 34 driven by a linear actuator 40. Optional vent lines 46a, 46b and pneumatic vent valves 48a, 48b may be pneumatically connected to the first and second cylinder chambers 30a, 30b of each provided pneumatic cylinder 30, respectively. In the third main embodiment, only a first pneumatic line 56a extends from the pneumatic cylinder 30 to the pneumatic pump chamber 70a. A first pneumatic valve 58b, under the control of the control unit 100, is provided along the first pneumatic line 56a. A second pneumatic line 56c extends from the air pump 80 and intersects with the first pneumatic line 56a. A second pneumatic valve 58v, under the control of the control unit 100, is provided along the second pneumatic line 58c. The pressure sensor 44a is provided along the common portion of the first and second pneumatic lines 56a, 56c. One or more fluid pump chambers 112a, 112b (chamber 112a shown here by way of example) are again provided as part of the disposable set 10, wherein the fluid pump chamber 112a pumps fresh or used PD fluid from a desired PD fluid source FS to a desired destination FD, as determined by the sequencing of one or more fluid valves SV, DV.

[0122] FIG. 14 shows that the control unit 100 of the third main embodiment first opens the first and second pneumatic valves 58a, 58c and the source fluid valve SV, causing the air pump 80 to generate negative pressure in the pneumatic pump chamber 70a and the cylinder chamber 30a, drawing the flexible membrane of the fluid pump chamber 112a into the pneumatic pump chamber 70a and drawing new or used PD fluid into the fluid pump chamber 112a. In one embodiment, the control unit 100 during the PD fluid drawing phase monitors the speed of the air pump 80. When the speed of the air pump 80 begins to decrease beyond a set threshold, the control unit 100 determines that the flexible membrane is fully stretched and expanded, and therefore the fluid pump chamber 112a is full of new or used PD fluid. The speed of the air pump 80 directly correlates to the flow rate of PD fluid (e.g., how quickly PD fluid is loaded into the pump chamber 112a). Thus, control unit 100 may be programmed to monitor the speed of air pump 80 to determine if the membrane is fully extended (e.g., to stop the air pump after a threshold change in speed is detected). Control unit 100 also provides closed-loop control to air pump 80 so that a desired pressure is maintained. The control loop through control unit 100 may be a proportional-integral-derivative ("PID") control loop that ensures that the pressure does not exceed a set threshold that could be harmful to the membrane.

[0123] FIG. 15 shows that after the fluid pump chamber 112a is completely filled with PD fluid, the control unit 100 closes the source fluid valve SV and the first pneumatic valve 58a. FIG. 16 shows that the control unit 100 opens the first and second pneumatic valves 58a and 58c, causing the air pump 80 to generate a desired positive pumping pressure (e.g., 1.5 psig) in the pneumatic pump chamber 70a and the cylinder chamber 30a. FIG. 17 shows that once the desired positive pumping pressure is reached, the control unit 100 closes the second pneumatic valve 58c, thereby isolating and blocking the air pump 80. The piston head 36 of the piston 32 is now in an initial piston head position.

[0124] 18 shows that the control unit 100 then maintains the first pneumatic valve 58a open and opens the destination fluid valve DV. The desired positive pressure built in the pneumatic pump chamber 70a forces the flexible membrane of the fluid pump chamber 112a to contract, pushing new or used PD fluid to the desired destination FD. When the positive pressure dissipates, the control unit 100 moves the piston 32 within the cylinder chamber 30a, causing the pressure sensor 44a to continue to read the desired pressure, e.g., 1.5 psig.

[0125] FIG. 19 shows that eventually, the flexible membrane of fluid pump chamber 112a can no longer contract, causing the pressure sensor 44a reading to spike, at which point control unit 100 stops the pump-out translation of piston head 36 and closes destination fluid valve DV. The detection that the flexible membrane can no longer contract may alternatively or additionally be determined by control unit 100 detecting that linear actuator 40 and / or piston head 36 are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping pump-out translation, first pneumatic valve 58a remains open, allowing the positive pressure maintained at the desired pressure to equalize between cylinder chamber 30a and pneumatic pump chamber 70a, which may be read by pressure sensor 44a. Piston head 36 is now in its final piston head position. The volume difference of the known cross-sectional area of ​​the air cylinder 30 between the final piston head position and the initial piston head position is the volume of new PD fluid that will be pumped to the desired fluid destination FD as calculated by the control unit 100, provided that the pressure at the initial and final piston head positions is the same, e.g., 1.5 psig, which is the desired pump-to-patient pressure.

[0126] FIG. 20 shows that the control unit 100 controls the first and second pneumatic valves 58a, 58c to open the source fluid valve SV, moving the piston 32 in the opposite direction within the cylinder 30 to reposition the piston head 36 for the next pump-out stroke. Movement of the piston 32 creates negative pressure within the cylinder chamber 30a and the pneumatic pump chamber 70a, which can be assisted by the air pump 80 to quickly achieve the desired PD fluid draw-in pressure. The flexible membrane of the fluid pump chamber 112a is drawn into the pneumatic pump chamber 70a, and new or used PD fluid is correspondingly drawn into the fluid pump chamber. The above process for the third main embodiment is repeated, with the control unit 100 accumulating pump stroke volume until the desired or predetermined amount of new or used PD fluid is delivered to the desired fluid destination FD.

[0127] Fourth Main Embodiment 21-24 illustrate a fourth main embodiment of the system 10, also utilizing an air pump 80 operating in cooperation with an air cylinder 30. Here, a single air pump 80 and air cylinder can drive two fluid pump chambers 112a, 112b within each of two air pump chambers 70a, 70b. The air cylinders 30 of the fourth main embodiment are structured similarly to the third main embodiment and include a piston head 36 and a piston shaft 34 driven by a linear actuator 40. Optional vent lines and air vent valves (not shown) may be in pneumatic communication with the first and second cylinder chambers of each air cylinder. In the fourth main embodiment, only the first pneumatic line 56a extends from the air cylinder 30, but the first pneumatic line 56 is split to also include a second pneumatic line 56b, where the first and second pneumatic lines 56a, 56b extend to first and second pneumatic pump chambers 112a, 112b, respectively. First and second pneumatic valves 58a, 58b, under the control of the control unit 100, are provided along the first and second pneumatic lines 56a, 56b, respectively.

[0128] A third pneumatic line 56c extends from the air pump 80 and splits into a fourth pneumatic line 56d. The third pneumatic line 56c intersects with the first pneumatic line 56a, and the fourth pneumatic line 56d intersects with the second pneumatic line 56b. A third pneumatic valve 58c under the control of the control unit 100 is provided along the third pneumatic line 56c, and a fourth pneumatic valve 58d under the control of the control unit 100 is provided along the fourth pneumatic line 56d. A first pressure sensor 44a is provided adjacent to the pneumatic pump chamber 70a, and a second pressure sensor 44b is provided adjacent to the pneumatic pump chamber 70b. First and second fluid pump chambers 112a, 112b are provided as part of the disposable set 100, wherein the first and second fluid pump chambers pump fresh or used PD fluid from a desired PD fluid source FS to a desired PD fluid destination as determined by the sequencing of a plurality of fluid valves SV, DV.

[0129] In the pumping sequence of the fourth main embodiment, the first and second fluid pump chambers 112a, 112b are generally alternated, where one fluid pump chamber 112a or 112b draws in new or used PD fluid while the other fluid pump chamber 112b or 112a pushes new or used PD fluid out. Each fluid pump chamber 112a, 112b has its own set of source and destination valves SV, DV, although the first and second fluid pump chambers 112a, 112b need not be perfectly synchronized.

[0130] 21 shows that the control unit 100 of the fourth main embodiment initially opens the third pneumatic valve 58c and the source fluid valve SV for the first fluid pump chamber 112a, causing the air pump 80 to create negative pressure in the first pneumatic pump chamber 70a, drawing the flexible membrane of the first fluid pump chamber 112a into the first pneumatic pump chamber 70a and drawing new or used PD fluid into the first fluid pump chamber. The control unit 100 during the PD fluid draw phase may again monitor the speed of the air pump 80. When the speed of the air pump 80 begins to decrease beyond a threshold, the control unit 100 determines that the flexible membrane is fully stretched and expanded, and thus the fluid pump chamber 112a is full of new or used PD fluid, at which point the control unit 100 stops the air pump 80 and closes the source fluid valve SV for the first fluid pump chamber 112a.

[0131] 22 shows that the control unit 100 then maintains the third pneumatic valve 58c open, causing the air pump 80 to generate the desired positive pumping pressure (e.g., 1.5 psig as read by the first pressure sensor 44a) in the first pneumatic pump chamber 70a. At this point, the piston head 36 of the piston 32 of the air cylinder 30 is in the initial piston head position.

[0132] 23 shows that the control unit 100 then causes the third pneumatic valve 58c to close, the first pneumatic valve 58a to open, and the first destination fluid valve DV to open. The desired positive pressure built in the first pneumatic pump chamber 70a forces the flexible membrane of the first fluid pump chamber 112a to contract, pushing new or used PD fluid to the desired fluid destination FD. When the positive pressure dissipates, the control unit 100 causes the piston 36 to move further within the cylinder chamber 30a, causing the first pressure sensor 44a to continue to read the desired pressure, e.g., 1.5 psig. At or near the same time, the control unit 100 causes the fourth pneumatic valve 58d to open, the second source valve SV to open, and the air pump 80 to create a negative pressure in the second pneumatic pump chamber 70b, drawing the flexible membrane of the second fluid pump chamber 112b into the second pneumatic pump chamber 70b and drawing new or used PD fluid into the second fluid pump chamber.

[0133] FIG. 24 shows that eventually, the first flexible membrane of first fluid pump chamber 112a cannot contract any further, causing the reading of first pressure sensor 44a to spike, at which point control unit 100 stops the pump-out translation of piston head 36 and closes first destination fluid valve DV. The detection that the flexible membrane cannot contract any further may alternatively or additionally be determined by control unit 100 detecting that linear actuator 40 and / or piston head 36 are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping pump-out translation, first pneumatic valve 58a remains open, allowing the positive pressure maintained at the desired pressure to equalize between cylinder chamber 30a and first pneumatic pump chamber 70a, which may be read by first pressure sensor 44a. Piston head 36 is now in its final piston head position within cylinder chamber 30a. The volume difference of the known cross-sectional area of ​​the air cylinder 30 between the final piston head position and the initial piston head position is the volume of new or used PD fluid that will be pumped to the desired fluid destination FD as calculated by the control unit 100, provided that the pressure at the initial and final piston head positions is the same, e.g., 1.5 psig, which is the desired pump-to-patient pressure. For fluid draw in the second fluid pump chamber 112b, the control unit 100 may again monitor the speed of the air pump 80. When the speed of the air pump 80 begins to decrease beyond a set threshold, the control unit 100 determines that the flexible membrane of the second fluid pump chamber 112b is fully stretched and expanded, and therefore the second fluid pump chamber is full of new or used PD fluid, at which point the control unit stops the air pump 80 and closes the second source fluid valve SV for the second fluid pump chamber 112b.

[0134] The control unit 100 then retracts the piston 32 to the initial position and repeats the above process, but now the first fluid pump chamber 112a fills with new or used PD fluid and the second fluid pump chamber 112b pushes the new or used PD fluid to the fluid destination FD. The control unit 100 continues to accumulate a known stroke volume and perform the alternating pumping sequence just described until the desired or predetermined amount of new or used PD fluid has been delivered to the destination FD.

[0135] Fifth Main Embodiment 25-28 illustrate a fifth main embodiment of the system 10, which, like the fourth main embodiment, uses an air pump 80 operating in cooperation with the air cylinder 30 to drive two pneumatic pump chambers 70a, 70b and corresponding fluid pump chambers 112a, 112b. In the fourth main embodiment, the air cylinder 30 is unidirectional with respect to fluid volume metering because only one side of the piston head 36 (chamber 30a) within the cylinder is exposed to the first and second pressure sensors 44a, 44b. The piston 32 must be reset accordingly in the fourth embodiment after each fluid pump chamber retract / fluid pump chamber deliver sequence. In the fifth main embodiment, a fifth pneumatic line 56e is added, extending from the first pneumatic line 56a to the opposite side of the air cylinder 30, thereby providing pneumatic access to the air cylinder on both sides of the piston head 36. A fifth pneumatic valve 58e is provided to operate with the fifth pneumatic line 56e. A sixth pneumatic valve 58f is added as a second valve along the first pneumatic line 56a to allow closing of the air cylinder 30 at chamber 30b.

[0136] 25 illustrates that in a pumping sequence using the fifth main embodiment of system 10, control unit 100 causes second and fifth pneumatic valves 58b, 58f to open, second destination fluid valve DV to open, and piston head 36 of air cylinder 30 to move in a first direction to deliver fresh or used PD fluid from second fluid pump chamber 112b to a desired destination FD. Simultaneously, control unit 100 causes third pneumatic valve 58c and first source fluid valve SV to open, thereby allowing air pump 80 to apply negative pressure to the flexible membrane of first fluid pump chamber 112a to draw fresh or used PD fluid into the first fluid pump chamber.

[0137] 26 shows that eventually, the second flexible membrane of second fluid pump chamber 112b is unable to contract further, causing the reading of second pressure sensor 44b to spike, at which point control unit 100 stops the pump-out translation of piston head 36 and closes second destination fluid valve DV. The detection that the flexible membrane is unable to contract further may alternatively or additionally be determined by control unit 100 detecting that linear actuator 40 and / or piston head 36 are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping pump-out translation, second and fifth pneumatic valves 58b, 58e remain open, allowing the positive pressure maintained at the desired pressure to equalize between cylinder chamber 30a and second pneumatic pump chamber 70b, which may be read by second pressure sensor 44b. The volume difference of the known cross-sectional area of ​​the air cylinder 30 between the initial and final piston head positions is the volume of new or used PD fluid that will be pumped to the desired destination DV as calculated by the control unit 100, with the pressure at the initial and final piston head positions being the same, e.g., 1.5 psig, which is the desired pump-to-patient pressure. For fluid draw in the first fluid pump chamber 112a, the control unit 100 may again monitor the speed of the air pump 80. When the speed of the air pump 80 begins to decrease beyond a set threshold, the control unit 100 determines that the flexible membrane of the first fluid pump chamber 122a is fully stretched and expanded, and therefore the first fluid pump chamber is full of new or used PD fluid, at which point the control unit 100 stops the air pump 80 and closes the first source fluid valve SV for the first fluid pump chamber 112a.

[0138] 27 shows that the first and second fluid pump chambers 112a, 112b then switch operation, such that the second fluid pump chamber 112b draws in fresh or used PD fluid, while the first fluid pump chamber 112a delivers fresh or used PD fluid. Notably, there is no need to adjust the piston head 36 to prepare the air cylinder 30 for the switch. The control unit 100 now causes the first and sixth pneumatic valves 58a, 58f to open, which opens the first destination fluid valve DV, moving the piston head 36 of the air cylinder 30 in the second direction to deliver fresh or used PD fluid from the first fluid pump chamber 112a to the desired fluid destination FD. At the same time, the control unit 100 causes the fourth pneumatic valve 58d and the second source fluid valve SV to open, thereby allowing the air pump 80 to apply negative pressure to the flexible membrane of the second fluid pump chamber 112b to draw new or used PD fluid into the second fluid pump chamber.

[0139] 28 shows that eventually, the first flexible membrane of the first fluid pump chamber 112a is unable to contract further, causing the reading of the first pressure sensor 44a to spike, at which point the control unit 100 stops the pump-out translation of the piston head 36 and closes the first destination fluid valve DV. The detection that the flexible membrane is unable to contract further may alternatively or additionally be determined by the control unit 100 detecting that the linear actuator 40 and / or piston head 36 are not moving while the desired pressure, e.g., 1.5 psig, is maintained. In either case, after stopping the pump-out translation, the first and sixth pneumatic valves 58a, 58f remain open, allowing the positive pressure maintained at the desired pressure to equalize between the second cylinder chamber 30b and the first pneumatic pump chamber 70a, which may be read by the first pressure sensor 44a. The volume difference of the known cross-sectional area of ​​the air cylinder 30 between the initial and final piston head positions is the volume of new or used PD fluid that will be pumped to the desired destination FD as calculated by the control unit 100, provided that the pressure at the initial and final piston head positions is the same, e.g., 1.5 psig, which is the desired pump-to-patient pressure. For fluid draw in the second fluid pump chamber 112b, the control unit 100 may again monitor the speed of the air pump 80. When the speed of the air pump 80 begins to decrease beyond a set threshold, the control unit 100 determines that the flexible membrane of the second fluid pump chamber 112b is fully stretched and expanded, and therefore the second fluid pump chamber is full of new or used PD fluid, at which point the control unit 100 stops the air pump 80 and closes the second source fluid valve SV for the second fluid pump chamber 112b.

[0140] The control unit 100 accumulates a known stroke volume and continues to perform the alternating pumping sequence just described until a desired or predetermined amount of new or used PD fluid is delivered to the destination FD. It should be understood that in any of the first through fifth main embodiments described above, for destinations of new or used PD fluid that do not contain a patient (e.g., heater container 116a or drain container 116b), the delivery pressure may be higher, e.g., up to 8 psig. In any of the first through fifth main embodiments, when either the air cylinder 30 or the air pump 80 is removing used PD fluid from the patient, the control unit 100 may monitor the associated first or second pressure sensor 44a, 44b to ensure that a patient drain negative pressure limit, e.g., −1.5 psig, is not met or exceeded.

[0141] It should be understood that the effects of drift in the air pressure sensors 44a, 44b in the above embodiment are negated because the important aspect of the above sequence involving the air cylinder 30 is that the initial and final pressures associated with fresh or used PD fluid delivery be equal, not that the pressure be precise in absolute terms (except for the patient's pumping pressure limit). Also, because the system 10 is pressure controlled, the linear actuator 40 does not need to be highly accurate.

[0142] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.

Claims

1. 1. A peritoneal dialysis system comprising: a pneumatic pump chamber; A cylinder; a piston including a piston head slidably sealed within the cylinder, the piston head separating a first cylinder chamber from a second cylinder chamber; a linear actuator in mechanical communication with the piston; a first pneumatic line extending between the first cylinder chamber and the pneumatic pump chamber; a second pneumatic line extending between the second cylinder chamber and the pneumatic pump chamber; a first pneumatic valve located along the first pneumatic line; a second pneumatic valve located along the second pneumatic line; a pressure sensor positioned and arranged to measure pressure within the pneumatic pump chamber; a fluid pump chamber operatively coupled to the pneumatic pump chamber; a source fluid valve; a destination fluid valve; a control unit, the control unit configured to (i) open the second pneumatic valve and the source fluid valve and cause the linear actuator to move the piston head into the first cylinder chamber, thereby creating negative air pressure in the second cylinder chamber and the pneumatic pump chamber to draw source fluid into the fluid pump chamber; (ii) closing the second pneumatic valve and the source fluid valve, opening the first pneumatic valve and the destination fluid valve, and causing the linear actuator to move the piston head further into the first cylinder chamber, thereby forcing source fluid into the destination fluid valve; the control unit uses the output from the pressure sensor to control the linear actuator such that the final pressure in (ii) is at least substantially equal to the initial pressure in (ii), such that the volume of space corresponding to the movement of the piston head within the cylinder during (ii) is equal to the volume of the source fluid delivered from the fluid pump chamber during (ii); and A peritoneal dialysis system comprising:

2. 10. The peritoneal dialysis system of claim 1, wherein the source fluid valve is for a PD fluid supply container, a heating container, or a patient line.

3. 10. The peritoneal dialysis system of claim 1, wherein the destination fluid valve is for a heating vessel, a drain vessel, or a patient line.

4. 2. The peritoneal dialysis system of claim 1, wherein the volume of the space corresponding to the movement of the piston head within the cylinder is a function of the distance moved by the piston head within the cylinder and the cross-sectional area of ​​the inner diameter of the cylinder.

5. 2. The peritoneal dialysis system of claim 1, wherein the control unit is configured to determine the volume of the source fluid delivered from the fluid pump chamber during (ii) with both the source fluid valve and the destination fluid valve closed.

6. 2. The peritoneal dialysis system of claim 1, wherein the control unit is further configured to: (iii) with the first pneumatic valve and the destination fluid valve closed, open the second pneumatic valve and the source fluid valve to allow the negative air pressure in the second cylinder chamber generated during at least one of (i) or (ii) to reach the pneumatic pump chamber and draw source fluid into the fluid pump chamber.

7. 7. The peritoneal dialysis system of claim 6, wherein the control unit is further configured to: (iv) generate at least substantially zero pressure in the first cylinder chamber and the second cylinder chamber by causing the linear actuator to move the piston head into the second cylinder chamber, with the first pneumatic valve, the source fluid valve, and the destination fluid valve closed and the second pneumatic valve closed.

8. 8. The peritoneal dialysis system of claim 7, wherein the control unit is further configured to (v) open the second pneumatic valve and the destination fluid valve and cause the linear actuator to move the piston head into the second cylinder chamber, thereby forcing source fluid into the destination fluid valve, and wherein the control unit controls the linear actuator using the output from the pressure sensor so that a final pressure in (v) is at least substantially equal to an initial pressure in (v), whereby a volume of space corresponding to the movement of the piston head within the cylinder during (v) is equal to a volume of the source fluid delivered from a fluid pump chamber during (v).

9. 9. The peritoneal dialysis system of claim 8, wherein the control unit is further configured to: (vi) with the second pneumatic valve and the destination fluid valve closed, open the first pneumatic valve and the source fluid valve to allow the negative air pressure in the first cylinder chamber generated during (v) to reach the pneumatic pump chamber and draw source fluid into the fluid pump chamber.

10. 1. A peritoneal dialysis system comprising: a pneumatic pump chamber; A cylinder; a piston including a piston head slidably sealed within said cylinder; a linear actuator in mechanical communication with the piston; An air pump and a first pneumatic line extending between the cylinder and the pneumatic pump chamber; a second pneumatic line extending between the air pump and the pneumatic pump chamber; a first pneumatic valve located along the first pneumatic line; a second pneumatic valve located along the second pneumatic line; a pressure sensor positioned and arranged to measure pressure within the pneumatic pump chamber; a fluid pump chamber operatively coupled to the pneumatic pump chamber; a source fluid valve; a destination fluid valve; a control unit, the control unit (i) causing the second pneumatic valve and the source fluid valve to open and causing the air pump to generate a negative air pressure in the pneumatic pump chamber to draw a source fluid into the fluid pump chamber; (ii) causing the source fluid valve to close and, with the second pneumatic valve open, causing the air pump to generate a desired positive air pressure in the pneumatic pump chamber as measured by the pressure sensor; and (iii) causing the second pneumatic valve to close and the first pneumatic valve and the destination fluid valve to open and cause the linear actuator to operate. and causing a linear actuator to move the piston head within the cylinder, thereby forcing source fluid into the destination fluid valve, the control unit using an output from the pressure sensor to control the linear actuator such that a final pressure in (iii) is at least substantially equal to an initial pressure in (iii), whereby a volume of space corresponding to the movement of the piston head within the cylinder during (iii) is equal to a volume of the source fluid delivered from a fluid pump chamber during (iii). A peritoneal dialysis system comprising:

11. 11. The peritoneal dialysis system of claim 10, wherein the source fluid valve is for a PD fluid supply container, a heating container, or a patient line.

12. 11. The peritoneal dialysis system of claim 10, wherein the destination fluid valve is for a heating vessel, a drain vessel, or a patient line.

13. 11. The peritoneal dialysis system of claim 10, wherein the volume of the space corresponding to the movement of the piston head within the cylinder is a function of the distance moved by the piston head within the cylinder and the cross-sectional area of ​​the inner diameter of the cylinder.

14. 11. The peritoneal dialysis system of claim 10, wherein during (i), the first pneumatic valve is open.

15. 11. The peritoneal dialysis system of claim 10, wherein the control unit is further configured, with the first pneumatic valve and the source fluid valve open, to (iv) cause the linear actuator to move the piston head in an opposite direction within the cylinder to draw source fluid into the fluid pump chamber.

16. 16. The peritoneal dialysis system of claim 15, wherein during (iv), the first air pressure valve is open and the air pump is activated to assist in drawing source fluid into the fluid pump chamber.

17. 1. A peritoneal dialysis system comprising: a first pneumatic pump chamber; a second pneumatic pump chamber; A cylinder; a piston including a piston head slidably sealed within said cylinder; a linear actuator in mechanical communication with the piston; An air pump and a first pneumatic line extending between the cylinder and the first pneumatic pump chamber; a second pneumatic line extending between the cylinder and the second pneumatic pump chamber; a third pneumatic line extending between the air pump and the first pneumatic pump chamber; a fourth pneumatic line extending between the air pump and the second pneumatic pump chamber; a first pneumatic valve located along the first pneumatic line; a second pneumatic valve located along the second pneumatic line; a third pneumatic valve located along the third first pneumatic line; a fourth pneumatic valve located along the fourth pneumatic line; a first pressure sensor positioned and arranged to measure pressure within the first pneumatic pump chamber; a second pressure sensor positioned and arranged to measure pressure within the second pneumatic pump chamber; a first fluid pump chamber operatively coupled to the first pneumatic pump chamber; a first source fluid valve for the first pump chamber; a first destination fluid valve for the first pump chamber; a second fluid pump chamber operatively coupled to the first pneumatic pump chamber; a second source fluid valve for the second pump chamber; and a second destination fluid valve for the second pump chamber; a control unit configured to use the air pump to generate negative and positive air pressures in the first and second air pressure pump chambers, and to operate the linear actuator to move the piston head within the cylinder while equalizing initial and final positive air pressures to meter a determinable volume of source fluid through the first and second destination fluid valves; A peritoneal dialysis system comprising:

18. The control unit (i) with the third pneumatic valve and the first source fluid valve open, causing the air pump to create a negative air pressure in the first pneumatic pump chamber to draw source fluid into the first fluid pump chamber; (ii) with the third pneumatic valve open and the first source fluid valve closed, causing the air pump to generate a desired positive air pressure in the first pneumatic pump chamber as measured by the first pressure sensor; (iii) with the first pneumatic valve and the first destination fluid valve open, causing the linear actuator to move the piston head within the cylinder to force source fluid into the first destination fluid valve; configured to:

18. The peritoneal dialysis system of claim 17, wherein the control unit uses the output from the first pressure sensor to control the linear actuator so that a final pressure in (iii) is at least substantially equal to an initial pressure in (iii), such that a volume of space corresponding to the movement of the piston head within the cylinder during (iii) is equal to a volume of the source fluid delivered from the first fluid pump chamber during (iii), and wherein with the fourth pneumatic valve and the second source fluid valve open, the air pump generates a negative air pressure in the second pneumatic pump chamber to draw source fluid into the second fluid pump chamber.

19. The control unit, when the piston head is moved to the retracted position, (iv) with the fourth pneumatic valve open and the second source fluid valve closed, causing the air pump to generate a desired positive air pressure in the second pneumatic pump chamber as measured by the first pressure sensor; (v) with the second pneumatic valve and the second destination fluid valve open, causing the linear actuator to move the piston head within the cylinder to force source fluid into the second destination fluid valve; further configured to:

19. The peritoneal dialysis system of claim 18, wherein the control unit uses the output from the second pressure sensor to control the linear actuator so that a final pressure of (v) is at least substantially equal to an initial pressure of (v), such that a volume of space corresponding to the movement of the piston head within the cylinder during (v) is equal to a volume of the source fluid delivered from the second fluid pump chamber during (v), and wherein, with the third pneumatic valve and the first source fluid valve open, the air pump generates a negative air pressure in the first pneumatic pump chamber to draw source fluid into the first fluid pump chamber.

20. 1. A peritoneal dialysis system comprising: a first pneumatic pump chamber; a second pneumatic pump chamber; A cylinder; a piston including a piston head slidably sealed within the cylinder, the piston head separating a first cylinder chamber from a second cylinder chamber; a linear actuator in mechanical communication with the piston; An air pump and a first pneumatic line extending between the second cylinder chamber and the first pneumatic pump chamber; a second pneumatic line extending between the second cylinder chamber and the second pneumatic pump chamber; a third pneumatic line extending between the air pump and the first pneumatic pump chamber; a fourth pneumatic line extending between the air pump and the second pneumatic pump chamber; a fifth pneumatic line extending between the first cylinder chamber and the first pneumatic line; a first pneumatic valve located along the first pneumatic line; a second pneumatic valve located along the second pneumatic line; a third pneumatic valve located along the third first pneumatic line; a fourth pneumatic valve located along the fourth pneumatic line; a fifth pneumatic valve located along the fifth pneumatic line; a sixth pneumatic valve located adjacent to the second cylinder chamber; a first pressure sensor positioned and arranged to measure pressure within the first pneumatic pump chamber; a second pressure sensor positioned and arranged to measure pressure within the second pneumatic pump chamber; a first fluid pump chamber operatively coupled to the first pneumatic pump chamber; a first source fluid valve for the first pump chamber; a first destination fluid valve for the first pump chamber; a second fluid pump chamber operatively coupled to the first pneumatic pump chamber; a second source fluid valve for the second pump chamber; and a second destination fluid valve for the second pump chamber; A control unit, the control unit comprising: using the air pump to generate negative and positive air pressures in the first and second air pressure pump chambers; operating the linear actuator to move the piston head within the first cylinder chamber and the second cylinder chamber while equalizing initial and final positive air pressures to meter a determinable volume of source fluid through the first destination fluid valve and the second destination fluid valve; a control unit configured to A peritoneal dialysis system comprising:

21. The control unit (i) with the third pneumatic valve and the first source fluid valve open, causing the air pump to create a negative air pressure in the first pneumatic pump chamber to draw source fluid into the first fluid pump chamber; causing the linear actuator to move the piston head toward the first cylinder chamber, thereby forcing source fluid into the second destination fluid valve, while the second pneumatic valve, the fifth pneumatic valve, and the second destination fluid valve are open; configured to:

21. The peritoneal dialysis system of claim 20, wherein the control unit uses the output from the second pressure sensor to control the linear actuator so that the final pressure of (i) is at least substantially equal to the initial pressure of (i), such that a volume of space corresponding to the movement of the piston head toward the first cylinder chamber during (i) is equal to a volume of the source fluid delivered from the second fluid pump chamber during (i).

22. The control unit (ii) with the fourth pneumatic valve and the second source fluid valve open, causing the air pump to generate a negative air pressure in the second pneumatic pump chamber to draw source fluid into the second fluid pump chamber; causing the linear actuator to move the piston head toward the second cylinder chamber, thereby forcing source fluid into the first destination fluid valve, while the first pneumatic valve, the sixth pneumatic valve, and the first destination fluid valve are open; further configured to:

22. The peritoneal dialysis system of claim 21, wherein the control unit uses the output from the first pressure sensor to control the linear actuator so that the final pressure in (ii) is at least substantially equal to the initial pressure in (ii), such that a volume of space corresponding to the movement of the piston head toward the second cylinder chamber during (ii) is equal to a volume of the source fluid delivered from the second fluid pump chamber during (ii).

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