Source: https://patents.google.com/patent/US10201647B2/en
Timestamp: 2019-04-23 10:29:58+00:00

Document:
2016-04-14 Assigned to DEKA PRODUCTS LIMITED PARTNERSHIP reassignment DEKA PRODUCTS LIMITED PARTNERSHIP ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DOHERTY, DAVID B., SCARPACI, JACOB W., COLL, ANDREW S., DALE, JAMES D., GIROUARD, PAUL G., RUSHLOW, JOSEPH P., SPENCER, GEOFFREY P., BRYANT, ROBERT J., JR., BEAVERS, DAVID A., KAROL, DANIEL S., KERWIN, JOHN M., YOO, Jinsun, BOLTON, EDGAR J., SINGER, DANIEL B., NORRIS, MICHAEL G.
2016-04-14 Assigned to DEKA PRODUCTS LIMITED PARTNERSHIP reassignment DEKA PRODUCTS LIMITED PARTNERSHIP ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HIBBARD, DAVID J.
2016-04-14 Assigned to DEKA PRODUCTS LIMITED PARTNERSHIP reassignment DEKA PRODUCTS LIMITED PARTNERSHIP ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MCGILL, DAVID W.
2016-04-14 Assigned to DEKA PRODUCTS LIMITED PARTNERSHIP reassignment DEKA PRODUCTS LIMITED PARTNERSHIP ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HELMORE, SIMON C.
Improvements in fluid volume measurement systems are disclosed for a pneumatically actuated diaphragm pump in general, and a peritoneal dialysis cycler using a pump cassette in particular. Pump fluid volume measurements are based on pressure measurements in a pump control chamber and a reference chamber in a two-chamber model, with different sections of the apparatus being modeled using a combination of adiabatic, isothermal and polytropic processes. Real time or instantaneous fluid flow measurements in a pump chamber of a diaphragm pump are also disclosed, in this case using a one-chamber ideal gas model and using a high speed processor to obtain and process pump control chamber pressures during fluid flow into or out of the pump chamber. Improved heater control circuitry is also disclosed, to provide added or redundant safety measures, or to reduce current leakage from a heater element during pulse width modulation control of the heater. Improvements are also disclosed in the application of negative pressure during a drain phase in peritoneal dialysis therapy, and to control the amount of intraperitoneal fluid accumulation during a therapy. Improvements in efficiency are also disclosed in the movement of fluid into and out of a two-pump cassette and heater bag of a peritoneal dialysis cycler, and in the synchronization of the operation of two or more pumps in a peritoneal dialysis cycler or other fluid handling devices using a multi-pump arrangement.
This application is a continuation in part of U.S. application Ser. No. 13/667,696, filed Nov. 2, 2012, now U.S. Pat. No. 9,078,971, issued Jul. 14, 2015, which is a continuation in part of U.S. application Ser. No. 13/178,191, filed Jul. 7, 2011, now U.S. Pat. No. 8,708,950, issued Apr. 29, 2014, which claims the benefit of U.S. Provisional Application No. 61/362,259, filed Jul. 7, 2010.
U.S. application Ser. No. 13/667,696 is also a continuation in part of U.S. application Ser. No. 12/864,357, filed Jul. 23, 2010 and entered the national stage on Dec. 13, 2010, now U.S. Pat. No. 9,248,225, issued Feb. 2, 2016, which is a national stage of PCT application PCT/US2009/000440, filed Jan. 23, 2009, which claims the benefit of U.S. Provisional Application No. 61/011,967, filed Jan. 23, 2008 and U.S. Provisional Application No. 61/058,469, filed Jun. 3, 2008.
U.S. application Ser. No. 13/667,696 is also a continuation in part of U.S. application Ser. No. 12/864,378, filed Jul. 23, 2010 and entered the national stage on Dec. 9, 2010, now U.S. Pat. No. 9,358,332, issued Jun. 7, 2016, which is a national stage of PCT application PCT/US2009/000436, filed Jan. 23, 2009, which claims the benefit of U.S. Provisional Application No. 61/011,967, filed Jan. 23, 2008 and U.S. Provisional Application No. 61/058,469, filed Jun. 3, 2008.
U.S. application Ser. No. 13/667,696 is also a continuation in part of U.S. application Ser. No. 12/864,391, filed Jul. 23, 2010 and entered the national stage on Dec. 3, 2010, now U.S. Pat. No. 8,197,439, issued Jun. 12, 2012, which is a national stage of PCT application PCT/US2009/000439, filed Jan. 23, 2009, which claims the benefit of U.S. Provisional Application No. 61/011,967, filed Jan. 23, 2008 and U.S. Provisional Application No. 61/058,469, filed Jun. 3, 2008.
U.S. application Ser. No. 13/667,696 is also a continuation in part of U.S. application Ser. No. 12/864,287, filed Jul. 23, 2010 and entered the national stage on Dec. 17, 2010, now U.S. Pat. No. 9,022,969, issued May 5, 2015, which is a national stage of PCT application PCT/US2009/000437, filed Jan. 23, 2009, which claims the benefit of U.S. Provisional Application No. 61/011,967, filed Jan. 23, 2008 and U.S. Provisional Application No. 61/058,469, filed Jun. 3, 2008.
U.S. application Ser. No. 13/667,696 is also a continuation in part of U.S. application Ser. No. 12/864,293, filed Jul. 23, 2010 and entered the national stage on Dec. 9, 2010, now U.S. Pat. No. 9,028,440, issued May 12, 2015, which is a national stage of PCT application PCT/US2009/000433, filed Jan. 23, 2009, which claims the benefit of U.S. Provisional Application No. 61/011,967, filed Jan. 23, 2008 and U.S. Provisional Application No. 61/058,469, filed Jun. 3, 2008.
U.S. application Ser. No. 13/667,696 is also a continuation in part of U.S. application Ser. No. 12/864,322, filed Jul. 23, 2010 and entered the national stage on Dec. 20, 2010, now U.S. Pat. No. 8,840,581, issued Sep. 23, 2014, which is a national stage of PCT application PCT/US2009/000441, filed Jan. 23, 2009, which claims the benefit of U.S. Provisional Application No. 61/011,967, filed Jan. 23, 2008 and U.S. Provisional Application No. 61/058,469, filed Jun. 3, 2008.
U.S. application Ser. No. 13/667,696 also claims the benefit of U.S. Provisional Application No. 61/555,926, filed Nov. 4, 2011.
U.S. Provisional Application No. 62/159,737 filed May 11, 2015.
The above applications are hereby incorporated by reference in their entirety.
Peritoneal Dialysis (PD) involves the periodic infusion of sterile aqueous solution (called peritoneal dialysis solution, or dialysate) into the peritoneal cavity of a patient. Diffusion and osmosis exchanges take place between the solution and the bloodstream across the natural body membranes. These exchanges transfer waste products to the dialysate that the kidneys normally excrete. The waste products typically consist of solutes like sodium and chloride ions, and other compounds normally excreted through the kidneys like urea, creatinine, and water. The diffusion of water across the peritoneal membrane during dialysis is called ultrafiltration.
Conventional peritoneal dialysis solutions include dextrose in concentrations sufficient to generate the necessary osmotic pressure to remove water from the patient through ultrafiltration.
Continuous Ambulatory Peritoneal Dialysis (CAPD) is a popular form of PD. A patient performs CAPD manually about four times a day. During a drain/fill procedure for CAPD, the patient initially drains spent peritoneal dialysis solution from his/her peritoneal cavity, and then infuses fresh peritoneal dialysis solution into his/her peritoneal cavity. This drain and fill procedure usually takes about 1 hour.
Automated Peritoneal Dialysis (APD) is another popular form of PD. APD uses a machine, called a cycler, to automatically infuse, dwell, and drain peritoneal dialysis solution to and from the patient's peritoneal cavity. APD is particularly attractive to a PD patient, because it can be performed at night while the patient is asleep. This frees the patient from the day-to-day demands of CAPD during his/her waking and working hours.
The APD sequence typically lasts for several hours. It often begins with an initial drain phase to empty the peritoneal cavity of spent dialysate. The APD sequence then proceeds through a succession of fill, dwell, and drain phases that follow one after the other. Each fill/dwell/drain sequence is called a cycle.
During the fill phase, the cycler transfers a predetermined volume of fresh, warmed dialysate into the peritoneal cavity of the patient. The dialysate remains (or “dwells”) within the peritoneal cavity for a period of time. This is called the dwell phase. During the drain phase, the cycler removes the spent dialysate from the peritoneal cavity.
The number of fill/dwell/drain cycles that are required during a given APD session depends upon the total volume of dialysate prescribed for the patient's APD regimen, and is either entered as part of the treatment prescription or calculated by the cycler.
APD can be and is practiced in different ways.
Continuous Cycling Peritoneal Dialysis (CCPD) is one commonly used APD modality. During each fill/dwell/drain phase of CCPD, the cycler infuses a prescribed volume of dialysate. After a prescribed dwell period, the cycler completely drains this liquid volume from the patient, leaving the peritoneal cavity empty, or “dry.” Typically, CCPD employs 4-8 fill/dwell/drain cycles to achieve a prescribed therapy volume.
After the last prescribed fill/dwell/drain cycle in CCPD, the cycler infuses a final fill volume. The final fill volume dwells in the patient for an extended period of time. It is drained either at the onset of the next CCPD session in the evening, or during a mid-day exchange. The final fill volume can contain a different concentration of dextrose than the fill volume of the successive CCPD fill/dwell/drain fill cycles the cycler provides.
Intermittent Peritoneal Dialysis (IPD) is another APD modality. IPD is typically used in acute situations, when a patient suddenly enters dialysis therapy. IPD can also be used when a patient requires PD, but cannot undertake the responsibilities of CAPD or otherwise do it at home.
Like CCPD, IPD involves a series of fill/dwell/drain cycles. Unlike CCPD, IPD does not include a final fill phase. In IPD, the patient's peritoneal cavity is left free of dialysate (or “dry”) in between APD therapy sessions.
Tidal Peritoneal Dialysis (TPD) is another APD modality. Like CCPD, TPD includes a series of fill/dwell/drain cycles. Unlike CCPD, TPD does not completely drain dialysate from the peritoneal cavity during each drain phase. Instead, TPD establishes a base volume during the first fill phase and drains only a portion of this volume during the first drain phase. Subsequent fill/dwell/drain cycles infuse and then drain a replacement volume on top of the base volume. The last drain phase removes all dialysate from the peritoneal cavity.
There is a variation of TPD that includes cycles during which the patient is completely drained and infused with a new full base volume of dialysis.
TPD can include a final fill cycle, like CCPD, Alternatively, TPD can avoid the final fill cycle, like IPD.
APD offers flexibility and quality of life enhancements to a person requiring dialysis. APD can free the patient from the fatigue and inconvenience that the day to day practice of CAPD represents to some individuals. APD can give back to the patient his or her waking and working hours free of the need to conduct dialysis exchanges.
Still, the complexity and size of past machines and associated disposables for various APD modalities have dampened widespread patient acceptance of APD as an alternative to manual peritoneal dialysis methods.
In one aspect, a system is disclosed for measuring an amount of liquid in a pumping chamber of a pneumatically actuated diaphragm pump. The system comprises a fluid inlet and fluid outlet valve connected to the pumping chamber; a diaphragm separating a pneumatically actuated control chamber from the pumping chamber, the control chamber fluidly connected to a reference chamber of known volume via a conduit that includes a reference chamber valve; the control chamber fluidly connected via one or more actuation valves to a source of positive or negative pneumatic pressure; and a controller configured to control the fluid inlet and outlet valves, the reference chamber valve, and the one or more actuation valves, and to receive pressure data from a first pressure sensor connected to the actuation chamber and a second pressure sensor connected to the reference chamber. The controller is configured to isolate the pumping chamber by closing the fluid inlet and outlet valves, charge the control chamber with a first pneumatic pressure; vent the reference chamber or fix a pneumatic pressure in the reference chamber that is different from the control chamber pneumatic pressure; measure a first control chamber pressure and a first reference chamber pressure, connect the control chamber to the reference chamber by opening the reference chamber valve, measure a third equalized pneumatic pressure in the control and reference chambers, and compute a control chamber volume based on an ideal gas model that assumes an adiabatic pressure equalization process in the reference chamber and a polytropic pressure equalization process in the control chamber.
The model optionally can further assume an isothermal process in the conduit as a gas moves from the control chamber to the reference chamber during the equalization process. The model applied to the control chamber can also use a polytropic coefficient in the ideal gas model, wherein the controller is programmed to vary the polytropic coefficient as a pre-defined function of the control chamber volume. The controller can also be programmed to compute a polytropic coefficient based on an estimated volume of the control chamber using a model that assumes an adiabatic pressure equalization process in the control chamber.
In another aspect, a system is disclosed for measuring an amount of liquid in a pumping chamber of a pneumatically actuated diaphragm pump. The system comprises a fluid inlet and fluid outlet valve connected to the pumping chamber; a diaphragm separating a pneumatically actuated control chamber from the pumping chamber, the control chamber fluidly connected to a reference chamber of known volume via a conduit that includes a reference chamber valve; the control chamber fluidly connected via one or more actuation valves to a source of positive or negative pneumatic pressure; and a controller configured to control the fluid inlet and outlet valves, the reference chamber valve, and the one or more actuation valves, and to receive pressure data from a first pressure sensor connected to the actuation chamber and a second pressure sensor connected to the reference chamber.
The controller is configured to isolate the pumping chamber by closing the fluid inlet and outlet valves, charge the control chamber with a first pneumatic pressure; vent the reference chamber or fix a pneumatic pressure in the reference chamber that is different from the control chamber pneumatic pressure; measure a first control chamber pressure and a first reference chamber pressure, connect the control chamber to the reference chamber by opening the reference chamber valve and equalizing pressures between the control chamber and the reference chamber, measure a third equalized pneumatic pressure in the control and reference chambers. The controller is configured to compute a control chamber volume based on an ideal gas model that assumes the presence of three closed mass systems of a gas comprising: a first mass system that occupies the control chamber at the end of pressure equalization; a second mass system that occupies the reference chamber before pressure equalization; and a third mass system that occupies the conduit, a part of the control chamber and a part of the reference chamber after equalization of pressure begins between the control and reference chambers.
The model can optionally assume an expansion of the first mass system after pressure equalization begins, the expansion being modeled as a polytropic process. The model can also assume a compression of the second mass system after pressure equalization begins, the compression being modeled as an adiabatic process. The third mass system can be modeled to be subdivided into component volumes, a first component volume occupying part of the control chamber and being modeled polytropically, a second component volume occupying part of the reference chamber and being modeled adiabatically, and a third component volume occupying the conduit and being modeled isothermally.
The controller is configured to isolate the pumping chamber by closing the fluid inlet and outlet valves, charge the control chamber with a first pneumatic pressure; vent the reference chamber or fix a pneumatic pressure in the reference chamber that is different from the control chamber pneumatic pressure; measure a first control chamber pressure and a first reference chamber pressure, connect the control chamber to the reference chamber by opening the reference chamber valve and equalizing pressures between the control chamber and the reference chamber, measure a third equalized pneumatic pressure in the control and reference chambers. The controller is configured to compute the control chamber volume based on an ideal gas model that assumes the presence of three closed mass systems of a gas comprising: a first mass system that occupies the control chamber before pressure equalization; a second mass system that occupies the reference chamber at the end of pressure equalization; and a third mass system that occupies the conduit, a part of the control chamber and a part of the reference chamber after equalization of pressure begins between the control and reference chambers.
The model can optionally assume a compression of the first mass system after pressure equalization begins, the compression being modeled as a polytropic process. The model can also assume an expansion of the second mass system after pressure equalization begins, the expansion being modeled as an adiabatic process. The third mass system can be modeled to be subdivided into component volumes, a first component volume occupying part of the control chamber being modeled polytropically, a second component volume occupying part of the reference chamber being modeled adiabatically, and a third component volume occupying the conduit being modeled isothermally.
The controller is configured to isolate the pumping chamber by closing the fluid inlet and outlet valves, charge the control chamber with a first pneumatic pressure; vent the reference chamber or fix a pneumatic pressure in the reference chamber that is different from the control chamber pneumatic pressure; measure a first control chamber pressure and a first reference chamber pressure, connect the control chamber to the reference chamber by opening the reference chamber valve and equalizing pressures between the control chamber and the reference chamber, measure a third equalized pneumatic pressure in the control and reference chambers. The controller is configured to compute a control chamber volume based on an ideal gas model under a polytropic process, and is configured to select a polytropic coefficient for the model using a pre-determined function in which the value of the polytropic coefficient depends on and varies with the control chamber volume.
The pre-determined function can be determined by fixing the control chamber volume at a known volume, and calculating a polytropic coefficient corresponding to the known volumes of the control and reference chambers, and the measured first, second and third pressures before and after equalization of pressures. The calculation is repeated a plurality of times, each time corresponding to fixing the control chamber volume at a different known volume. The function can correspond to a stored look-up table from which the controller selects a polytropic coefficient corresponding to the volume of the control chamber being computed. Or the function can correspond to an equation that has been fitted to a plurality of calculated polytropic coefficients corresponding to a series of known control chamber volumes.
In another aspect, A method for the measuring a volume comprises: providing a chamber defined by one or more rigid impermeable boundaries and one movable impermeable boundary, wherein the volume of the chamber varies; fixing the movable boundary; charging the chamber with a gas to a pre-charge pressure value above ambient pressure and allowing the gas to come to thermal equilibrium with the boundaries of the chamber; recording the pressure in the chamber as the first pressure; releasing the movable boundary and allowing the gas in the chamber to displace the movable boundary, which displaces a volume of fluid equivalent to the volume swept by the movable boundary; allowing the gas in the chamber to again come to thermal equilibrium with the boundaries of the chamber; recording the volume of displaced fluid; recording the pressure in the chamber as the second pressure; and determining the volume of the chamber before displacement based on the first pressure, the second pressure, the volume of displaced fluid, and an ideal gas model of the chamber gas between the recording of the first pressure and the recording of the second pressure.
The ideal gas model can assume an isothermal process between the recording of the first pressure and the recording of the second pressure. The method can further comprise determining the volume of the chamber after displacement based on the first pressure, the second pressure, the volume of displaced fluid and an ideal gas model of the chamber gas between the recording of the first pressure and the recording of the second pressure.
In another aspect, a method is disclosed for calibrating a known volume-measurement-procedure comprising: providing a liquid pump apparatus having a pump chamber separated from a pump control chamber by a movable membrane, and a reference chamber that is fluidly connectable to the pump control chamber, wherein the pump chamber is selectively connected to a liquid volume measurement device; filling the liquid side of the pump chamber so it occupies most of the pump control chamber; making a first provisional measurement of the pump control chamber volume using a known volume measurement procedure; charging the pump control chamber with a gas to a pre-charge pressure value and allowing the gas to come to thermal equilibrium with the boundaries of the pump control chamber; firstly recording the pressure in the pump control chamber as the first pressure; connecting the pump to the volume measurement device, so that the charge pressure displaces the membrane, which displaces liquid; allowing the gas in the pump control chamber to come to thermal equilibrium with boundaries of the pump control chamber; recording the volume of displaced fluid measured by the volume measurement device; secondly recording the pressure in the pump control chamber as the second pressure; determining the volume of the pump control chamber before displacement based on the first pressure, the second pressure, the volume of displaced fluid and an ideal gas model of the gas in the control chamber between the recording of the first pressure and the recording of the second pressure; and calculating a first calibration coefficient based on the volume of the pump control chamber and the first provisional volume measurement.
The method can further comprise: repeating the steps of making, charging, firstly recording the pressure, connecting, allowing, recording the volume, secondly recording the pressure, and determining until substantially all the liquid in pump chamber has been expelled; storing the calibration coefficient and the provisional volume measurements as a related pairs; and fitting a calibration equation to the stored values of calibration coefficient as a function of the related provisional volume measurements. The accuracy of the determined volumes of the pump control chamber can be improved by averaging 1) a given determined volume, 2) the preceding determined volume plus the preceding displaced water volume, and 3) the following determined volume minus the following displaced water volume. The accuracy of the first determined volume of the pump control chamber can also be improved by averaging 1) the first determined volume, and 2) the following determined volume minus the following displaced water volume. The accuracy of the last determined volume of the pump control chamber can also be improved by averaging 1) the last determined volume, and 2) the preceding determined volume plus the preceding displaced water volume.
Determining the volume of the pump control chamber can be based on the ideal gas model assumes a polytropic process with an expansion coefficient near 1. The method can further: execute a plurality of pumping strokes with the liquid pump apparatus, wherein the known volume-measurement-procedure occurs after each fill and deliver stroke and the volume of liquid displaced by the liquid pump apparatus is recorded for each stroke; correcting the volumetric results of the known volume-measurement-procedure with the calibration equation; calculating a volume measurement error based on the corrected volumetric results and the recorded volume of displaced liquid; re-determining the volumes of the pump control chamber before displacement based an ideal gas model, where the polytropic coefficient is adjusted based on the volume measurement error; re-calculating the calibration coefficients; re-correcting the volumetric results of the known volume-measurement-procedure with the re-calculated calibration equation; and re-calculating the volume measurement error based on the re-corrected volumetric results and the recorded volume of displaced liquid.
In another aspect, a system is disclosed for measuring an amount of liquid in a pumping chamber of a pneumatically actuated diaphragm pump comprising: a fluid inlet and fluid outlet valve connected to the pumping chamber; a diaphragm separating a pneumatically actuated control chamber from the pumping chamber, the control chamber fluidly connected to a reference chamber of known volume via a conduit that includes a reference chamber valve; the control chamber fluidly connected via one or more actuation valves to a source of positive or negative pneumatic pressure; a controller configured to control the fluid inlet and outlet valves, the reference chamber valve, and the one or more actuation valves, and to receive pressure data from a first pressure sensor connected to the actuation chamber and a second pressure sensor connected to the reference chamber; wherein the controller is configured to isolate the pumping chamber by closing the fluid inlet and outlet valves, charge the control chamber with a first pneumatic pressure; vent the reference chamber or fix a pneumatic pressure in the reference chamber that is different from the control chamber pneumatic pressure; measure a first control chamber pressure and a first reference chamber pressure, connect the control chamber to the reference chamber by opening the reference chamber valve and equalizing pressures between the control chamber and the reference chamber, measure a third equalized pneumatic pressure in the control and reference chambers, and compute a control chamber volume based on an ideal gas model under a polytropic process, wherein the controller is configured to select a polytropic coefficient for the model using a pre-determined function in which the value of the polytropic coefficient depends on and varies with an estimate of the control chamber volume that is calculated from the first control chamber pressure, the first reference chamber pressure and the third equalized pressure based on an ideal gas model.
The pre-determined function optionally can be determined by fixing the control chamber volume at a known volume, and calculating the estimate of the control chamber volume and a polytropic coefficient corresponding to the known volumes of the control and reference chambers, and the measured first, second and third pressures before and after equalization of pressures; wherein said calculation is repeated a plurality of times, each said time corresponding to fixing the control chamber volume at a different known volume. The function can correspond to a stored look-up table from which the controller selects a polytropic coefficient corresponding to the estimate of control chamber volume being computed. The function can also correspond to an equation that has been fitted to a plurality of calculated polytropic coefficients corresponding to a series of estimated control chamber volumes.
In another aspect, a system is disclosed for measuring an amount of liquid in a pumping chamber of a pneumatically actuated diaphragm pump comprising: a fluid inlet and fluid outlet valve connected to the pumping chamber; a diaphragm separating a pneumatically actuated control chamber from the pumping chamber, the control chamber fluidly connected to a reference chamber of known volume via a conduit that includes a reference chamber valve; the control chamber fluidly connected via one or more actuation valves to a source of positive or negative pneumatic pressure; a controller configured to control the fluid inlet and outlet valves, the reference chamber valve, and the one or more actuation valves, and to receive pressure data from a first pressure sensor connected to the actuation chamber and a second pressure sensor connected to the reference chamber; wherein the controller is configured to isolate the pumping chamber by closing the fluid inlet and outlet valves, charge the control chamber with a first pneumatic pressure; vent the reference chamber or fix a pneumatic pressure in the reference chamber that is different from the control chamber pneumatic pressure; measure a first control chamber pressure and a first reference chamber pressure, connect the control chamber to the reference chamber by opening the reference chamber valve and equalizing pressures between the control chamber and the reference chamber, measure a third equalized pneumatic pressure in the control and reference chambers, and compute a control chamber volume based on an ideal gas model under a polytropic process, wherein the controller is configured to select a polytropic coefficient for the model using a pre-determined function in which the value of the polytropic coefficient depends on and varies with the control chamber volume.
The pre-determined function optionally can be determined by fixing the control chamber volume at a known volume, and calculating a polytropic coefficient corresponding to the known volumes of the control and reference chambers, and the measured first, second and third pressures before and after equalization of pressures; wherein said calculation is repeated a plurality of times, each said time corresponding to fixing the control chamber volume at a different known volume. The function can correspond to a stored look-up table from which the controller selects a polytropic coefficient corresponding to the volume of the control chamber being computed. The function can also correspond to an equation that has been fitted to a plurality of calculated polytropic coefficients corresponding to a series of known control chamber volumes.
In another aspect, a method is disclosed for calibrating a known volume measurement procedure of claim 2a, wherein the accuracy of the determined volumes of the pump control chamber are improved by averaging 1) a given determined volume, 2) the preceding determined volume plus the preceding displaced water volume, and 3) the following determined volume minus the following displaced water volume.
In another aspect, a system is disclosed for calculating a change in fluid volume in a pumping chamber of a pneumatically actuated diaphragm pump using a gas having a heat capacity ratio of n. The system comprises a control chamber separated from the pumping chamber by a flexible diaphragm; a fluid inlet or outlet of the pumping chamber; a valve connecting the control chamber to a pressurized source of the gas; a pressure sensor fluidly connected to the control chamber; and a controller that receives pressure data from the pressure sensor, that controls the valve, and that is configured to regulate pressure in the control chamber by opening or closing the valve. The controller is configured to compute a change in volume of the control chamber as fluid enters or leaves the pumping chamber by monitoring a pressure change in the control chamber when the valve is closed. This computation assigns a first chamber volume to a first measured pressure, and calculates a second chamber volume based on a second later measured pressure using an equation in which a ratio of the second measured pressure to the first measured pressure is assumed to be equal to a ratio of the first chamber volume to the second chamber volume, raised to a power between 1 and n.
The assigned first chamber volume can be derived from an initial condition in which the control chamber is pressurized with air, the pumping chamber and control chamber are isolated, a measurement of control chamber pressure is taken, the control chamber is connected to a reference chamber having a known volume and measured pressure, and the controller derives an initial volume of the control chamber using a model based on an ideal gas equation. The controller can calculate a third chamber volume as fluid continues to enter or leave the pumping chamber by assigning the second chamber volume to the second measured pressure and calculating a third chamber volume based on a third measured pressure using an equation in which a ratio of the third measured pressure to the second measured pressure is assumed to be equal to a ratio of the second chamber volume to the third chamber volume, raised to a power between 1 and n. The controller can calculate a fluid flow into or out of the pumping chamber based on a difference between the first, second and third chamber volumes. The controller can repeat the calculations periodically during a time period in which fluid continues to enter or leave the pumping chamber, and can suspend the calculations during a time period in which the valve is opened to connect the control chamber with the pressurized source of the gas. The pressurized source of the gas can be a positively pressurized source or a negatively pressurized source. The gas can be air. The value of n can be approximately 1.4. The value of n can be adjusted by the controller by comparing a cumulative calculated volume of fluid moved into or out of the pumping chamber during a pump stroke to a volume change in the pumping chamber calculated from an initial volume determination at a beginning of the pump stroke and a final volume determination at an end of the pump stroke.
In another aspect, a method is disclosed for determining an amount of fluid delivered by a diaphragm pump having a pumping chamber separated from a pneumatically actuated control chamber by a diaphragm, and having pneumatically actuated inlet and outlet valves. The method is implemented by a controller that closes the outlet valve, opens the inlet valve, and connects the control chamber to a negative pressure source to apply negative pneumatic pressure to the diaphragm pump to draw fluid into the pumping chamber. The controller closes the inlet valve, connects the control chamber to the positive pressure source, isolates the control chamber, measures a first control chamber pressure, measures a first reference chamber pressure in a reference chamber having a known volume, connects the control chamber to the reference chamber, and calculates a first volume of the control chamber. It then opens the outlet valve, and connects the control chamber to a positive pressure source to apply a positive pneumatic pressure to the diaphragm pump to expel fluid from the pumping chamber. It then closes the outlet valve; vents the control chamber to reduce pressure in the control chamber toward atmospheric pressure; connects the control chamber to the positive pressure source, isolates the control chamber, measures a second control chamber pressure, measures a second reference chamber pressure, connects the control chamber to the reference chamber, and calculates a second volume of the control chamber; and then determines the amount of fluid delivered by the diaphragm pump based on the first and second volumes of the control chamber.
In another aspect, a method is disclosed for determining an amount of fluid delivered by a pumping cassette comprising a first and a second diaphragm pump each said diaphragm pump having a pumping chamber separated from a pneumatically actuated control chamber by a diaphragm, and each having pneumatically actuated inlet and outlet valves, the method comprising having a controller perform for each of diaphragm pumps the steps of: closing the outlet valve, opening the inlet valve, and connecting the control chamber to a negative pressure source to apply negative pneumatic pressure to the diaphragm pump to draw fluid into the pumping chamber; closing the inlet valve, connecting the control chamber to the positive pressure source, isolating the control chamber, measuring a first control chamber pressure, measuring a first reference chamber pressure in a reference chamber having a known volume, connecting the control chamber to the reference chamber, and calculating a first volume of the control chamber; opening the outlet valve, and connecting the control chamber to a positive pressure source to apply a positive pneumatic pressure to the diaphragm pump to expel fluid from the pumping chamber; closing the outlet valve; venting the control chamber to reduce pressure in the control chamber toward atmospheric pressure; connecting the control chamber to the positive pressure source, isolating the control chamber, measuring a second control chamber pressure, measuring a second reference chamber pressure, connecting the control chamber to the reference chamber, and calculating a second volume of the control chamber; and determining the amount of fluid delivered by the diaphragm pump based on the first and second volumes of the control chamber. Expelling fluid from the pumping chamber of the second diaphragm pump is performed after the control chamber of the first diaphragm pump is vented, and expelling fluid from the pumping chamber of the first diaphragm pump is performed after the control chamber of the second diaphragm pump is vented.
In another aspect, a system is disclosed for measuring a volume of liquid in a pumping chamber of a peritoneal dialysis pump cassette comprising: a base unit in which the pump cassette can be installed, the base unit including a control block having a control chamber depression configured to mate with the pumping chamber of the pumping cassette, and to move a flexible diaphragm between the pumping chamber and the control chamber under positive or negative pneumatic pressure. The control chamber depression is in communication via one or more pump actuation valves in the base unit with a source of positive or negative pressure, and in communication via a vent valve in the base unit with a vent connected to atmospheric pressure. A controller is configured to control the one or more pump actuation valves to operate the pumping cassette to fill the pumping chamber with liquid and to deliver liquid from the pumping chamber. The controller is configured to control one or more pneumatically actuated membrane inlet and outlet valves in the pump cassette via one or more inlet and outlet actuation valves in the base unit connected to the source of positive or negative pneumatic pressure. The controller is also configured to measure pneumatic pressure in the control chamber via a pressure sensor, and to calculate a volume of liquid in the pumping chamber, the calculation involving pneumatically pressurizing the control chamber before taking a pressure measurement. The controller is also configured to connect the control chamber with the vent after commanding a liquid delivery stroke of the pump cassette and before pneumatically pressurizing the control chamber to perform a pumping chamber liquid volume calculation.
In another aspect, a system is disclosed for adjusting negative pressure used to withdraw fluid from a cavity of a patient, the system comprising: a pump configured to provide negative pressure to a fluid line connected to the cavity; a controller configured to measure and control the negative pressure provided by the pump. The controller is also configured to measure a rate of flow of fluid from the fluid line to the pump. The controller is arranged to control the pump by providing a first negative pressure to the fluid line, measuring the rate of fluid flow, and control the pump by providing a second negative pressure to the fluid line that is greater in magnitude than the first negative pressure if the measured rate of fluid flow exceeds a pre-determined value.
A system is also disclosed for adjusting negative pressure used to withdraw fluid from a cavity of a patient. The system comprises: a pump configured to provide negative or positive pressure to a fluid line connected to the cavity; a controller configured to measure and control the pressure provided by the pump. The controller is also configured to measure a rate of flow of fluid from the fluid line to the pump, so that the controller is arranged to control the pump by providing negative pressure to the fluid line, measuring the rate of fluid flow, and control the pump by providing a positive pressure to the fluid line if the measured rate of fluid flow is less than a pre-determined value, and wherein the controller is arranged to re-apply negative pressure to the fluid line if a measured fluid flow upon application of the positive pressure is greater than a pre-determined amount.
A system is also disclosed for adjusting negative pressure used to withdraw fluid from a cavity of a patient, the system comprising: a pump configured to provide negative pressure to a fluid line connected to the cavity; a controller configured to measure and control the pressure provided by the pump. The controller is also configured to measure a flow rate of fluid from the fluid line to the pump. The controller is then arranged to control the pump by providing negative pressure in an amount that varies continuously as a function of the measured flow rate of the fluid, such that the variation in negative pressure applied by the pump is limited to within a pre-determined range of negative pressures.
A system is also disclosed for adjusting negative pressure used to withdraw fluid from a cavity of a patient, the system comprising: a pump configured to provide negative pressure to a fluid line connected to the cavity; a controller configured to measure and control the pressure provided by the pump; the controller also being configured to measure a flow rate of fluid from the fluid line to the pump. A user interface is configured to provide a user a measure of the negative pressure applied by the pump, and configured to receive input from the user to adjust the amount of negative pressure applied by the pump, such that the controller is arranged to receive via the user interface a command from the user to adjust the negative pressure applied by the pump, and to effectuate the adjustment.
A system is also disclosed for adjusting negative pressure used to withdraw fluid from a cavity of a patient, the system comprising: a pump configured to provide negative pressure to a fluid line connected to the cavity; a controller configured to measure and control the pressure provided by the pump; the controller also configured to measure a flow rate of fluid from the fluid line to the pump, and to compute a pumping duration based on the measured flow rate. A user interface is configured to provide a user a measure of the negative pressure applied by the pump, and configured to receive input from the user to adjust the amount of negative pressure applied by the pump, such that the controller is arranged to receive via the user interface a command from the user to adjust the negative pressure applied by the pump, to compute a change in the pumping duration resulting from the adjustment, to display information about the change in pumping duration on the user interface, and to receive from the user a command to proceed or not proceed with the adjustment.
In another aspect, a system is disclosed for performing automated peritoneal dialysis comprising; a cycler comprising a fluid pump and controller, the controller configured to measure and control an amount of fluid pumped to a peritoneal cavity and to track a remaining volume of the fluid in a solution bag. The controller is configured to: control a dialysis therapy by administering a pre-determined number of therapy cycles, each therapy cycle comprising a fill phase, dwell phase and drain phase; and maintain a pre-determined minimum volume of intra-peritoneal fluid during the dwell phase. It is also configured to cancel a final therapy cycle if a calculated final volume of fluid remaining in the solution bag for the final therapy cycle is less than a volume required to maintain the minimum intra-peritoneal fluid volume for the final therapy cycle dwell phase; divide the remaining final volume of fluid in the solution bag among a remaining number of therapy cycle fill volumes; and divide a duration of the final therapy cycle dwell phase among a remaining number of therapy cycle dwell phases. The controller is also configured to further adjust the fill volumes of the remaining number of therapy cycles, or the duration of the dwell phases of the remaining number of therapy cycles to prevent an accumulation of intra-peritoneal fluid during the remaining therapy cycles from exceeding a pre-determined maximum intra-peritoneal volume of fluid.
In another aspect, a system in an automated peritoneal dialysis apparatus is disclosed for replenishing a heater bag with fluid during a dialysis therapy comprising a fluid fill phase, a fluid dwell phase, and a fluid drain phase. The system comprises a controller configured to: track a remaining volume of fluid remaining in the heater bag; compute a replenish volume of fluid to be infused into the heater bag comprising subtracting the remaining volume from a fill volume of fluid to be infused into a patient in a subsequent fill phase of the dialysis therapy; compute a replenish volume transfer time required to transfer the replenish volume from a fluid source to the heater bag; compute a replenish volume heating time required to heat the replenish volume to within a pre-determined range of a pre-determined temperature set point; and compute a remaining dwell time required to complete the fluid dwell phase. The controller is also configured to control a fluid heater of the peritoneal dialysis apparatus to heat the replenish fluid as it enters the heater bag, and to control a fluid pump of the peritoneal dialysis apparatus to initiate pumping of the replenish volume to the heater bag when the remaining dwell time is equal to or greater than the greater of the replenish volume transfer time or the replenish volume heating time.
In another aspect, a system for replenishing a fluid heater bag of a medical fluid delivery apparatus is disclosed, the system comprising: a processor configured to receive temperature data associated with a fluid in the heater bag, to control a heater to heat the fluid in the heater bag, to control a fluid pump to pump the fluid in a replenish operation into the heater bag from a fluid source, to pump the fluid in a fill phase out of the heater bag to a patient, to control a dwell phase during which the fluid remains in the patient, and to pump the fluid in a drain phase out of the patient to a destination. The controller is further configured to determine a replenish volume to be transferred to the heater bag during the replenish operation, the replenish volume determination made by subtracting the volume of fluid in the bag at the beginning of the replenish operation from a volume of fluid to be pumped to the patient in the next fill phase; compute a replenish volume transfer time required to transfer the replenish volume from the fluid source to the heater bag; compute a replenish volume heating time required to heat the fluid to within a pre-determined range of a pre-determined temperature set point; compute a drain time required to complete the drain phase; and control the fluid pump to initiate pumping of the fluid in the replenish operation at a remaining dwell time during the dwell phase that is approximately equal to the greater of (1) the drain time plus the replenish volume heating time or (2) the drain time plus the replenish volume transfer time.
In another aspect, a solution expiration timing system is disclosed for an automated dialysis apparatus connected to a first fluid reservoir and a fluid heating reservoir. The system comprises a controller configured to begin a first solution expiration timer when a fluid is pumped from the first fluid reservoir to the fluid heating reservoir; begin a second solution expiration timer when the fluid in the fluid heating reservoir achieves a pre-determined temperature; wherein the controller is configured to declare a first expiration time when a first pre-determined time interval has elapsed, and to declare a second expiration time when a second pre-determined time interval has elapsed; and wherein the controller stops fluid transfer from the first fluid reservoir to the fluid heating reservoir at the first expiration time, and stops fluid transfer from the fluid heating reservoir to a user at the second expiration time.
In another aspect, a solution expiration timing system is disclosed for an automated dialysis apparatus connected to a first fluid reservoir containing a first fluid and a second fluid reservoir containing a second fluid. The system comprises a controller configured to: begin a first solution expiration timer when the first fluid is pumped from the first fluid reservoir to a fluid heating reservoir; begin a second solution expiration timer when the second fluid is pumped from the second fluid reservoir to the fluid heating reservoir; wherein the controller is configured to declare a first expiration time when a first pre-determined time interval has elapsed, and to declare a second expiration time when a second pre-determined time interval has elapsed; and wherein the controller stops fluid transfer from the first fluid reservoir to the fluid heating reservoir at the first expiration time, and stops fluid transfer from the second fluid reservoir to the fluid heating reservoir at the second expiration time.
In another aspect, a system is disclosed for detecting that a fluid line is primed with liquid. The system comprises a fluid pump having a pumping chamber configured to pump a liquid from a proximal portion to a distal portion of the fluid line at a pre-determined pressure; a sensor configured to measure the flow of liquid in the fluid line or to measure pressure in the pumping chamber to determine the flow of liquid in the fluid line; and a controller configured to receive data from the sensor and to compare the flow of liquid or a change in the flow of liquid in the fluid line with a pre-determined value. The distal portion of the fluid line comprises a flow restrictor that measurably reduces the flow of liquid in the fluid line when air in the distal portion of the fluid line is replaced by the liquid being pumped by the pump; and the controller declares the fluid line to be primed when the reduction in measured liquid flow reaches the predetermined value.
In another aspect, an automated peritoneal dialysis cycler is equipped with an autoconnect apparatus for spiking solution lines for dialysis therapy. A cap detection system is disclosed for detecting the presence of a solution line or spike cap on a cap stripper, the cap detection system comprising: a position sensor for the cap stripper configured to detect a position of the cap stripper relative to a plane in which a plurality of cassette spikes or a plurality of solution lines reside when placed in the cycler; a controller configured to command movement of the cap stripper toward or away from the plane, or laterally in a direction parallel with the plane, and to receive information from the position sensor to compare the position of the cap stripper relative to a first or second pre-determined fully deployed position of the cap stripper toward the plane. The controller is configured to: command the cap stripper to move toward the plane when one or more solution lines are installed in the cycler, and to issue an alert if a cap on the cap stripper prevents a final position of the cap stripper from reaching the first pre-determined fully deployed position; or command the cap stripper to move laterally a pre-determined distance and then toward the plane when no solution lines are installed in the cycler, and to issue an alert if a cap on the cap stripper prevents a final position of the cap stripper from reaching the second pre-determined fully deployed position.
In another aspect, an identification system is disclosed for a fluid line connected to a fluid container for medical use. The system comprises an image sensor configured to read an image generated by fluorescent light, the image comprising a pattern of coded information characterizing the fluid in the container; a fluid line mount configured to hold the fluid line in a fixed position within a field of view of the image sensor; an identification tag attached to a portion of the fluid line on or near the mount; the identification tag having an identifying marking arranged to emit fluorescent light in the pattern of the image in response to absorption of light having a non-visible wavelength; an emitter configured to emit light in the non-visible wavelength onto the identification tag; and a controller configured to receive an electronic signal from the image sensor and to decode the information in the image pattern emitted by the identifying marking of the identification tag.
In another aspect, a brace is disclosed for a distal portion of a fluid line, the fluid line configured to receive a hollow spike in a fluid handling apparatus, the brace comprising: a rigid clamping member configured to encircle the distal portion of the fluid line after being mounted on the distal portion of the fluid line, having one or more features on an inside surface of the clamping member configured to cooperate with one or more complementary features on an outside surface of the distal portion of the fluid line. The brace is arranged to be mountable on the distal portion of the fluid line to constrain it from bending out of alignment with a longitudinal axis of the hollow spike before or after an initiation of a spiking of the distal portion of the fluid line.
In another aspect, an electronic circuit is disclosed for reducing touch or leakage current from a heating element of an automated peritoneal dialysis apparatus. The circuit comprises: a first relay connecting a first pole of an AC mains source to a first end of the heating element; a second relay connecting a second pole of the AC mains source to a second end of the heating element; and a controller configured to control current delivery to the heating element by transmitting an on signal to both the first and second relays or an off signal to both the first and second relays, the on signal causing AC mains current to flow through the heating element, and the off signal preventing AC mains current from flowing through the heating element. The heating element is isolated from AC mains voltage when the controller transmits an off signal.
In another aspect, an electronic circuit is disclosed for delivering electric power to an automated peritoneal dialysis apparatus from a power source having a first voltage or a higher second voltage, the electronic circuit comprising: a heater comprising a first heater element connected to a second heater element by a heater select relay, the heater select relay configured to connect the first heater element either in series or in parallel with the second heater element; a current sense element configured to measure a current flow through the heater; a controller configured to set a default configuration of the heater select relay on powering up so that the first heater element is in series with the second heater element; wherein the controller is programmed to receive information on current flow from the current sense element, and is programmed to command the heater select relay to set the first heater element in parallel with the second heater element if a measured current is less than a pre-determined target current for the heater.
In another aspect, a control system is disclosed for a heater of an automated peritoneal dialysis apparatus comprising: a resistive heating element; a solid state relay connecting an electrical power source to the heating element; a first processor configured to generate and send a pulse width modulated signal to a gating circuit; a second processor configured to generate and send a safety signal to the gating circuit; wherein the gating circuit is configured to reproduce or transmit the pulse width modulated signal to operate the solid state relay if the safety signal is in a first mode, and is configured to prevent the operation of the solid state relay if the safety signal is in a second mode.
The gating circuit optionally can operate the solid state relay through optical transmission. The optical transmission can be performed using a light emitting diode of an opto-isolator. The solid state relay can comprise a triac or a pair of silicon controlled rectifiers. The solid state relay can connects a first pole of an AC mains voltage source to the heating element, and a second solid state relay connects a second pole of the AC mains voltage source to the heating element, such that the pulse width modulated signal reproduced or transmitted by the gating circuit operates both the solid state relay and the second solid state relay. The solid state relay can also connect a first pole of an AC mains voltage source to the heating element, and a second solid state relay connects a second pole of the AC mains voltage source to the heating element, such that a second gating circuit is configured to receive the pulse width modulated signal from the first processor and the safety signal from the second processor, and such that the second gating circuit is configured to reproduce or transmit the pulse width modulated signal to operate the second solid state relay if the safety signal is in the first mode, and is configured to prevent the operation of the second solid state relay if the safety signal is in the second mode.
In another aspect, a housing is disclosed for an automated peritoneal dialysis apparatus comprising: a dual pressure reservoir integrally formed in the housing, the dual pressure reservoir having a first section separated from a second section by a dividing wall; the first section configured for positive air pressurization by a pump via a first port; the second section configured for negative air pressurization by the pump via a second port; and a cover plate for enclosing the first and second sections, said cover plate forming a seal against a perimeter wall of the first section, a perimeter wall of the second section, and the dividing wall between the first and second sections.
A housing is also disclosed for an automated peritoneal dialysis apparatus that comprises: a dual pressure reservoir integrally formed in the housing, the dual pressure reservoir having a first section separated from a second section by a dividing wall; the first section configured for positive air pressurization by a pump via a first port, and comprising a first perimeter wall joining with the dividing wall and a first set of one or more stiffening members extending from a portion of the first perimeter wall to the dividing wall; the second section configured for negative air pressurization by the pump via a second port, and comprising a second perimeter wall joining with the dividing wall and a second set of one or more stiffening members extending from a portion of the second perimeter wall to the dividing wall; and a cover plate for enclosing the first and second sections, said cover plate forming a seal against the first and second perimeter walls and the dividing wall between the first and second sections.
A housing is also for an automated peritoneal dialysis apparatus comprising: a dual pressure reservoir integrally formed in the housing, the dual pressure reservoir having a first section separated from a second section by a dividing wall; the first section configured for positive air pressurization by a pump via a first port, and comprising a first perimeter wall joining with the dividing wall; the second section configured for negative air pressurization by the pump via a second port, and comprising a second perimeter wall joining with the dividing; and a cover plate for enclosing the first and second sections, said cover plate forming a seal against the first and second perimeter walls and the dividing wall between the first and second sections; such that a plurality of stiffening members are attached to an inside surface of the cover plate, so that when the cover plate is attached to the dual pressure reservoir, a first set of said stiffening members extends in the first section from a portion of the first perimeter wall to the dividing wall, and a second set of said stiffening members extends in the second section from a portion of the second perimeter wall to the dividing wall.
A housing is also disclosed for a dual pressure air reservoir comprising: a first reservoir surrounding a second reservoir, the first and second reservoirs separated by a dividing wall, and the first reservoir having an outer perimeter wall; the first reservoir configured for negative air pressurization by a pump via a first port; the second reservoir configured for positive air pressurization by the pump via a second port; a cover plate for enclosing the first and second reservoirs, said cover plate forming a seal against the outer perimeter wall of the first reservoir and the dividing wall between the first and second reservoirs; such that a surface area of the cover plate defined by outer perimeter wall and the dividing wall is greater than a surface area of the cover plate defined by an area within the dividing wall; and such that a depth of the second reservoir is greater than a depth of the first reservoir so that a volume of the first reservoir is approximately equal to a volume of the second reservoir.
FIG. 109B is a plot of the polytropic expansion constant for +FMS verses control chamber volume.
FIG. 110B is a plot of the polytropic expansion constant for −FMS verses control chamber volume.
FIG. 217 shows a flowchart outlining steps which may be used to program and collected an automated effluent sample using a cycler.
Although aspects of the invention are described in relation to a peritoneal dialysis system, certain aspects of the invention can be used in other medical applications, including infusion systems such as intravenous infusion systems or extracorporeal blood flow systems, and irrigation and/or fluid exchange systems for the stomach, intestinal tract, urinary bladder, pleural space or other body or organ cavity. Thus, aspects of the invention are not limited to use in peritoneal dialysis in particular, or dialysis in general.
FIG. 1 shows an automated peritoneal dialysis (APD) system 10 that may incorporate one or more aspects of the invention. As shown in FIG. 1, for example, the system 10 in this illustrative embodiment includes a dialysate delivery set 12 (which, in certain embodiments, can be a disposable set), a cycler 14 that interacts with the delivery set 12 to pump liquid provided by a solution container 20 (e.g., a bag), and a control system 16 (e.g., including a programmed computer or other data processor, computer memory, an interface to provide information to and receive input from a user or other device, one or more sensors, actuators, relays, pneumatic pumps, tanks, a power supply, and/or other suitable components—only a few buttons for receiving user control input are shown in FIG. 1, but further details regarding the control system components are provided below) that governs the process to perform an APD procedure. In this illustrative embodiment, the cycler 14 and the control system 16 are associated with a common housing 82, but may be associated with two or more housings and/or may be separate from each other. The cycler 14 may have a compact footprint, suited for operation upon a table top or other relatively small surface normally found in the home. The cycler 14 may be lightweight and portable, e.g., carried by hand via handles at opposite sides of the housing 82.
The set 12 in this embodiment is intended to be a single use, disposable item, but instead may have one or more reusable components, or may be reusable in its entirety. The user associates the set 12 with the cycler 14 before beginning each APD therapy session, e.g., by mounting a cassette 24 within a front door 141 of the cycler 14, which interacts with the cassette 24 to pump and control fluid flow in the various lines of the set 12. For example, dialysate may be pumped both to and from the patient to effect APD. Post therapy, the user may remove all or part of the components of the set 12 from the cycler 14.
As is known in the art, prior to use, the user may connect a patient line 34 of the set 12 to his/her indwelling peritoneal catheter (not shown) at a connection 36. In one embodiment, the cycler 14 may be configured to operate with one or more different types of cassettes 24, such as those having differently sized patient lines 34. For example, the cycler 14 may be arranged to operate with a first type of cassette with a patient line 34 sized for use with an adult patient, and a second type of cassette with a patient line 34 sized for an infant or pediatric use. The pediatric patient line 34 may be shorter and have a smaller inner diameter than the adult line so as to minimize the volume of the line, allowing for more controlled delivery of dialysate and helping to avoid returning a relatively large volume of used dialysate to the pediatric patient when the set 12 is used for consecutive drain and fill cycles. A heater bag 22, which is connected to the cassette 24 by a line 26, may be placed on a heater container receiving portion (in this case, a tray) 142 of the cycler 14. The cycler 14 may pump fresh dialysate (via the cassette 24) into the heater bag 22 so that the dialysate may be heated by the heater tray 142, e.g., by electric resistance heating elements associated with the tray 142 to a temperature of about 37 degrees C. Heated dialysate may be provided from the heater hag 22 to the patient via the cassette 24 and the patient line 34. In an alternative embodiment, the dialysate can be heated on its way to the patient as it enters, or after it exits, the cassette 24 by passing the dialysate through tubing in contact with the heater tray 142, or through an in-line fluid heater (which may be provided in the cassette 24). Used dialysate may be pumped from the patient via the patient line 34 to the cassette 24 and into a drain line 28, which may include one or more clamps to control flow through one or more branches of the drain line 28. In this illustrative embodiment, the drain line 28 may include a connector 39 for connecting the drain line 28 to a dedicated drain receptacle, and an effluent sample port 282 for taking a sample of used dialysate for testing or other analysis. The user may also mount the lines 30 of one or more containers 20 within the door 141. The lines 30 may also be connected to a continuous or real-time dialysate preparation system. (The lines 26, 28, 30, 34 may include a flexible tubing and/or suitable connectors and other components (such as pinch valves, etc.) as desired.) The containers 20 may contain sterile peritoneal dialysis solution for infusion, or other materials (e.g., materials used by the cycler 14 to formulate dialysate by mixing with water, or admixing different types of dialysate solutions). The lines 30 may be connected to spikes 160 of the cassette 24, which are shown in FIG. 1 covered by removable caps. In one aspect of the invention described in more detail below, the cycler 14 may automatically remove caps from one or more spikes 160 of the cassette 24 and connect lines 30 of solution containers 20 to respective spikes 160. This feature may help reduce the possibility of infection or contamination by reducing the chance of contact of non-sterile items with the spikes 160.
In another aspect, a dialysate delivery set 12 a may not have cassette spikes 160. Instead, one or more solution lines 30 may be permanently affixed to the inlet ports of cassette 24, as shown in FIG. 1A. In this case, each solution line 30 may have a (capped) spike connector 35 for manual connection to a solution container or dialysate hag 20.
With various connections made, the control system 16 may pace the cycler 14 through a series of fill, dwell, and/or drain cycles typical of an APD procedure. For example, during a fill phase, the cycler 14 may pump dialysate (by way of the cassette 24) from one or more containers 20 (or other source of dialysate supply) into the heater bag 22 for heating. Thereafter, the cycler 14 may infuse heated dialysate from the heater bag 22 through the cassette 24 and into the patient's peritoneal cavity via the patient line 34. Following a dwell phase, the cycler 14 may institute a drain phase, during which the cycler 14 pumps used dialysate from the patient via the line 34 (again by way of the cassette 24), and discharges spent dialysis solution into a nearby drain (not shown) via the drain line 28.
The cycler 14 does not necessarily require the solution containers 20 and/or the heater bag 22 to be positioned at a prescribed head height above the cycler 14, e.g., because the cycler 14 is not necessarily a gravity flow system. Instead, the cycler 14 may emulate gravity flow, or otherwise suitably control flow of dialysate solution, even with the source solution containers 20 above, below or at a same height as the cycler 14, with the patient above or below the cycler, etc. For example, the cycler 14 can emulate a fixed head height during a given procedure, or the cycler 14 can change the effective head height to either increase or decrease pressure applied to the dialysate during a procedure. The cycler 14 may also adjust the rate of flow of dialysate. In one aspect of the invention, the cycler 14 may adjust the pressure and/or flow rate of dialysate when provided to the patient or drawn from the patient so as to reduce the patient's sensation of the fill or drain operation. Such adjustment may occur during a single fill and/or drain cycle, or may be adjusted across different fill and/or drain cycles. In one embodiment, the cycler 14 may taper the pressure used to draw used dialysate from the patient near the end of a drain operation. Because the cycler 14 may establish an artificial head height, it may have the flexibility to interact with and adapt to the particular physiology or changes in the relative elevation of the patient.
In one aspect of the invention, a cassette 24 may include patient and drain lines that are separately occludable with respect to solution supply lines. That is, safety critical flow to and from patient line may be controlled, e.g., by pinching the lines to stop flow, without the need to occlude flow through one or more solution supply lines. This feature may allow for a simplified occluder device since occlusion may be performed with respect to only two lines as opposed to occluding other lines that have little or no effect on patient safety. For example, in a circumstance where a patient or drain connection becomes disconnected, the patient and drain lines may be occluded. However, the solution supply and/or heater bag lines may remain open for flow, allowing the cycler 14 to prepare for a next dialysis cycle; e.g., separate occlusion of patient and drain lines may help ensure patient safety while permitting the cycler 14 to continue to pump dialysate from one or more containers 20 to the heater bag 22 or to other solution containers 20.
In another aspect of the invention, the cassette may have patient, drain and heater bag lines at one side or portion of the cassette and one or more solution supply lines at another side or portion of the cassette, e.g., an opposite side of the cassette. Such an arrangement may allow for separate occlusion of patient, drain or heater hag lines with respect to solution lines as discussed above. Physically separating the lines attached to the cassette by type or function allows for more efficient control of interaction with lines of a certain type or function. For example, such an arrangement may allow for a simplified occluder design because less force is required to occlude one, two or three of these lines than all lines leading to or away from the cassette. Alternately, this arrangement may allow for more effective automated connection of solution supply lines to the cassette, as discussed in more detail below. That is, with solution supply lines and their respective connections located apart from patient, drain and/or heater bag lines, an automated de-capping and connection device may remove caps from spikes on the cassette as well as caps on solution supply lines, and connect the lines to respective spikes without interference by the patient, drain or heater bag lines.
FIG. 2 shows an illustrative embodiment of a cassette 24 that incorporates aspects of the invention described above. In this embodiment, the cassette 24 has a generally planar body and the heater bag line 26, the drain line 28 and the patient line 34 are connected at respective ports on the left end of the cassette body, while the right end of the cassette body may include five spikes 160 to which solution supply lines 30 may be connected. In the arrangement shown in FIG. 2, each of the spikes 160 is covered by a spike cap 63, which may be removed, exposing the respective spike and allowing connection to a respective line 30. As described above, the lines 30 may be attached to one or more solution containers or other sources of material, e.g., for use in dialysis and/or the formulation of dialysate, or connected to one or more collection bags for sampling purposes or for peritoneal equilibration testing (PET test).
FIGS. 3 and 4 show exploded views (perspective and top views, respectively) of the cassette 24 in this illustrative embodiment. The cassette 24 is formed as a relatively thin and flat member having a generally planar shape, e.g., may include components that are molded, extruded or otherwise formed from a suitable plastic. In this embodiment, the cassette 24 includes a base member 18 that functions as a frame or structural member for the cassette 24 as well as forming, at least in part, various flow channels, ports, valve portions, etc. The base member 18 may be molded or otherwise formed from a suitable plastic or other material, such as a polymethyl methacrylate (PMMA) acrylic, or a cyclic olefin copolymer/ultra low density polyethylene (COC/ULDPE), and may be relatively rigid. In an embodiment, the ratio of COC to ULDPE can be approximately 85%/115%. FIG. 3 also shows the ports for the heater bag (port 150), drain (port 152) and the patient (port 154) that are formed in the base member 18. Each of these ports may be arranged in any suitable way, such as, for example, a central tube 156 extending from an outer ring or skirt 158, or a central tube alone. Flexible tubing for each of the heater bag, drain and patient lines 26, 28, 34 may be connected to the central tube 156 and engaged by the outer ring 158, if present.
Both sides of the base member 18 may be covered, at least in part, by a membrane 15 and 16, e.g., a flexible polymer film made from, for example, polyvinyl chloride (PVC), that is cast, extruded or otherwise formed. Alternatively, the sheet may be formed as a laminate of two or more layers of poly-cyclohexylene dimethylene cyclohexanedicarboxylate (PCCE) and/or ULDPE, held together, for example, by a coextrudable adhesive (CXA). In some embodiments, the membrane thickness may be in the range of approximately 0.002 to 0.020 inches thick. In a preferred embodiment, the thickness of a PVC-based membrane may be in the range of approximately 0.012 to 0.016 inches thick, and more preferably approximately 0.014 inches thick. In another preferred embodiment, such as, for example, for laminate sheets, the thickness of the laminate may be in the range of approximately 0.006 to 0.010 inches thick, and more preferably approximately 0.008 inches thick.
Both membranes 15 and 16 may function not only to close or otherwise form a part of flowpaths of the cassette 24, but also may be moved or otherwise manipulated to open/close valve ports and/or to function as part of a pump diaphragm, septum or wall that moves fluid in the cassette 24. For example, the membranes 15 and 16 may be positioned on the base member 18 and sealed (e.g., by heat, adhesive, ultrasonic welding or other means) to a rim around the periphery of the base member 18 to prevent fluid from leaking from the cassette 24. The membrane 15 may also be bonded to other, inner walls of the base member 18, e.g., those that form various channels, or may be pressed into sealing contact with the walls and other features of the base member 18 when the cassette 24 suitably mounted in the cycler 14. Thus, both of the membranes 15 and 16 may be sealed to a peripheral rim of the base member 18, e.g., to help prevent leaking of fluid from the cassette 24 upon its removal from the cycler 14 after use, yet be arranged to lie, unattached, over other portions of the base member 18. Once placed in the cycler 14, the cassette 24 may be squeezed between opposed gaskets or other members so that the membranes 15 and 16 are pressed into sealing contact with the base member 18 at regions inside of the periphery, thereby suitably sealing channels, valve ports, etc., from each other.
Other arrangements for the membranes 15 and 16 are possible. For example, the membrane 16 may be formed by a rigid sheet of material that is bonded or otherwise made integral with the body 18. Thus, the membrane 16 need not necessarily be, or include, a flexible member. Similarly, the membrane 15 need not be flexible over its entire surface, but instead may include one or more flexible portions to permit pump and/or valve operation, and one or more rigid portions, e.g., to close flowpaths of the cassette 24. It is also possible that the cassette 24 may not include the membrane 16 or the membrane 15, e.g., where the cycler 14 includes a suitable member to seal pathways of the cassette, control valve and pump function, etc.
In accordance with another aspect of the invention, the membrane 15 may include a pump chamber portion 151 (“pump membrane”) that is formed to have a shape that closely conforms to the shape of a corresponding pump chamber 181 depression in the base 18. For example, the membrane 15 may be generally formed as a flat member with thermoformed (or otherwise formed) dome-like shapes 151 that conform to the pump chamber depressions of the base member 18. The dome-like shape of the pre-formed pump chamber portions 151 may be constructed, for example, by heating and forming the membrane over a vacuum form mold of the type shown in FIG. 5. As shown in FIG. 5, the vacuum may be applied through a collection of holes along the wall of the mold. Alternatively, the wall of the mold can be constructed of a porous gas-permeable material, which may result in a more uniformly smooth surface of the molded membrane. In one example, the molded membrane sheet 15 is trimmed while attached to the vacuum form mold. The vacuum form mold then presses the trimmed membrane sheet 15 against the cassette body 18 and bonds them together. In one embodiment the membrane sheets 15,16 are heat-welded to the cassette body 18. In this way, the membrane 15 may move relative to the pump chambers 181 to effect pumping action without requiring stretching of the membrane 15 (or at least minimal stretching of the membrane 15), both when the membrane 15 is moved maximally into the pump chambers 181 and (potentially) into contact with spacer elements 50 (e.g., as shown in solid line in FIG. 4 while pumping fluid out of the pump chamber 181), and when the membrane 15 is maximally withdrawn from the pump chamber 181 (e.g., as shown in dashed line in FIG. 4 when drawing fluid into the pump chamber 181). Avoiding stretching of the membrane 15 may help prevent pressure surges or other changes in fluid delivery pressure due to sheet stretch and/or help simplify control of the pump when seeking to minimize pressure variation during pump operation. Other benefits may be found, including reduced likelihood of membrane 15 failure (e.g., due to tears in the membrane 15 resulting from stresses place on the membrane 15 during stretching), and/or improved accuracy in pump delivery volume measurement, as described in more detail below. In one embodiment, the pump chamber portions 151 may be formed to have a size (e.g., a define a volume) that is about 85-110% of the pump chamber 181, e.g., if the pump chamber portions 151 define a volume that is about 100% of the pump chamber volume, the pump chamber portion 151 may lie in the pump chamber 181 and in contact with the spacers 50 while at rest and without being stressed.
Providing greater control of the pressure used to generate a fill and delivery stroke of liquid into and out of a pump chamber may have several advantages. For example, it may be desirable to apply the minimum negative pressure possible when the pump chamber draws fluid from the patient's peritoneal cavity during a drain cycle. A patient may experience discomfort during the drain cycle of a treatment in part because of the negative pressure being applied by the pumps during a fill stroke. The added control that a pre-formed membrane can provide to the negative pressure being applied during a fill stroke may help to reduce the patient's discomfort.
A number of other benefits may be realized by using pump membranes pre-formed to the contour of the cassette pump chamber. For example, the flow rate of liquid through the pump chamber can be made more uniform, because a constant pressure or vacuum can be applied throughout the pump stroke, which in turn may simplify the process of regulating the heating of the liquid. Moreover, temperature changes in the cassette pump may have a smaller effect on the dynamics of displacing the membrane, as well as the accuracy of measuring pressures within the pump chambers. In addition, pressure spikes within the fluid lines can be minimized. Also, correlating the pressures measured by pressure transducers on the control (e.g. pneumatic) side of the membrane with the actual pressure of the liquid on the pump chamber side of the membrane may be simpler. This in turn may permit more accurate head height measurements of the patient and fluid source bags prior to therapy, improve the sensitivity of detecting air in the pump chamber, and improve the accuracy of volumetric measurements. Furthermore, eliminating the need to stretch the membrane may allow for the construction and use of pump chambers having greater volumes.
In this embodiment, the cassette 24 includes a pair of pump chambers 181 that are formed in the base member 18, although one pump chamber or more than two pump chambers are possible. In accordance with an aspect of the invention, the inner wall of pump chambers 181 includes spacer elements 50 that are spaced from each other and extend from the inner wall of pump chamber 18 to help prevent portions of the membrane 15 from contacting the inner wall of pump chamber 181. (As shown on the right-side pump chamber 181 in FIG. 4, the inner wall is defined by side portions 181 a and a bottom portion 181 b. The spacers 50 extend upwardly from the bottom portion 181 b in this embodiment, but could extend from the side portions 181 a or be formed in other ways.) By preventing contact of the membrane 15 with the pump chamber inner wall, the spacer elements 50 may provide a dead space (or trap volume) which may help trap air or other gas in the pump chamber 181 and inhibit the gas from being pumped out of the pump chamber 181 in some circumstances. In other cases, the spacers 50 may help the gas move to an outlet of the pump chamber 181 so that the gas may be removed from the pump chamber 181, e.g., during priming. Also, the spacers 50 may help prevent the membrane 15 from sticking to the pump chamber inner wall and/or allow flow to continue through the pump chamber 181, even if the membrane 15 is pressed into contact with the spacer elements 50. In addition, the spacers 50 help to prevent premature closure of the outlet port of the pump chamber (openings 187 and/or 191) if the sheet happens to contact the pump chamber inner wall in a non-uniform manner. Further details regarding the arrangement and/or function of spacers 50 are provided in U.S. Pat. Nos. 6,302,653 and 6,382,923, both of which are incorporated herein by reference.

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