Medical treatment system and methods using a plurality of fluid lines
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.
1. A system 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 also configured to measure a rate of flow of fluid from the fluid line to the pump;
wherein 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, and
wherein the controller is configured to control the pump to provide a positive pressure to the fluid line if the measured rate of fluid flow does not exceed the pre-determined value.
2. The system of claim 1 , wherein the controller is configured to provide the first negative pressure at a beginning of a first draining of the cavity during a series of fill and drain cycles.
3. The system of claim 1 , wherein a difference between the first and second negative pressures is within a range of 2 to 6 kilopascals.
4. The system of claim 2 , wherein a therapy session comprises the series of fill and drain cycles, and the controller is configured to initiate the therapy session if the measured rate of fluid flow exceeds the pre-determined value, and is configured to control the pump to provide the second negative pressure during subsequent drainings of the cavity during the therapy session.
5. The system of claim 4 , wherein the controller is configured to control the pump to provide a third negative pressure less than the first negative pressure, wherein the third negative pressure is applied during the first draining of the cavity, and the first negative pressure is applied during the subsequent drainings if the controller is programmed or commanded by a user to apply a pressure of lower magnitude than the second negative pressure during the subsequent drainings in the therapy session.
6. The system of claim 5 , wherein the controller is configured to receive a user input to adjust the magnitude of the first negative pressure.
7. The system of claim 4 , wherein the controller is configured to monitor the rate of fluid flow during one or more subsequent drainings during the therapy session, and to control the pump to reduce the magnitude of negative pressure applied by the pump if the measured flow rate fails to exceed the pre-determined value.
8. The system of claim 7 , wherein the negative pressure applied by the pump is reduced to the first negative pressure.
9. The system of claim 7 , wherein the controller is configured to initiate a notification to a user of the existence of a low flow condition if the measured flow rate remains at or below the pre-determined value for more than a pre-determined period of time.
10. The system of claim 9 , wherein the pre-determined period of time is at least 30 seconds.
11. The system of claim 1 , wherein the controller is configured to control the pump to provide the second negative pressure if the measured rate of fluid flow exceeds the pre-determined value for a pre-determined period of time.
12. The system of claim 11 , wherein the pre-determined period of time is at least 30 seconds.
13. The system of claim 1 , wherein the controller is configured to initiate a notification to a user if the measured rate of fluid flow does not exceed the pre-determined value.
14. The system of claim 1 , wherein the controller is configured to control the pump to provide the first negative pressure after the positive pressure, and to control the pump to provide the second negative pressure if the measured rate of fluid flow exceeds the pre-determined value.
15. The system of claim 1 , wherein the controller is configured to initiate a notification to a user if the measured rate of fluid flow does not exceed the pre-determined value during application of the positive pressure.
16. A system for adjusting negative pressure used to withdraw fluid from a cavity of a patient, the system comprising:
a pneumatically actuated diaphragm pump configured to provide positive or negative pressure to a fluid line connected to the cavity, the diaphragm pump having a pumping chamber connected to the fluid line and an actuation chamber having a valved connection to a source of positive or negative pneumatic pressure;
a controller configured to measure and control the positive or negative pressure provided by the pump via a pressure transducer in valved communication with the actuation chamber;
the controller also configured to compute a fluid flow rate through the fluid line by measuring pressures associated with the control chamber and computing the fluid flow rate from the measured pressures;
wherein the controller is arranged to control the pump by providing a first negative pressure to the fluid line, computing the fluid flow rate, 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 computed fluid flow rate exceeds a pre-determined value, and
wherein the controller is configured to control the pump to provide a positive pressure to the fluid line if the computed fluid flow rate does not exceed the pre-determined value.
17. The system of claim 16 , wherein the controller is configured to provide the first negative pressure at a beginning of a first draining of the cavity during a series of fill and drain cycles.
18. The system of claim 17 , wherein a therapy session comprises the series of fill and drain cycles, and the controller is configured to initiate the therapy session if the computed fluid flow rate exceeds the pre-determined value, and is configured to control the pump to provide the second negative pressure during subsequent drainings of the cavity during the therapy session.
19. The system of claim 17 , wherein a difference between the first and second negative pressures is within a range of 2 to 6 kilopascals.
20. The system of claim 17 , wherein the controller is configured to control the pump to provide a third negative pressure less than the first negative pressure, wherein the third negative pressure is applied during the first draining of the cavity, and the first negative pressure is applied during the subsequent drainings if the controller is programmed or commanded by a user to apply a pressure of lower magnitude than the second negative pressure during the subsequent drainings in the therapy session.
21. The system of claim 20 , wherein the controller is configured to receive a user input to adjust the magnitude of the first negative pressure.
22. The system of claim 18 , wherein the controller is configured to monitor the computed fluid flow rate during one or more subsequent drainings during the therapy session, and to control the pump to reduce the magnitude of negative pressure applied by the pump if the computed fluid flow rate fails to exceed the pre-determined value.
23. The system of claim 22 , wherein the negative pressure applied by the pump is reduced to the first negative pressure.
24. The system of claim 22 , wherein the controller is configured to initiate a notification to a user of the existence of a low flow condition if the computed fluid flow rate remains at or below the pre-determined value for more than a pre-determined period of time.
25. The system of claim 24 , wherein the pre-determined period of time is at least 30 seconds.
26. The system of claim 16 , wherein the controller is configured to control the pump to provide the second negative pressure if the computed fluid flow rate exceeds the pre-determined value for a pre-determined period of time.
27. The system of claim 26 , wherein the pre-determined period of time is at least 30 seconds.
28. The system of claim 16 , wherein the controller is configured to initiate a notification to a user if the computed fluid flow rate does not exceed the pre-determined value.
29. The system of claim 16 , wherein the controller is configured to control the pump to provide the first negative pressure after the positive pressure, and to control the pump to provide the second negative pressure if the computed fluid flow rate exceeds the pre-determined value.
30. The system of claim 16 , wherein the controller is configured to initiate a notification to a user if the computed fluid flow rate does not exceed the pre-determined value during application of the positive pressure.
31. A peritoneal dialysis system for adjusting negative pressure used to withdraw fluid from a peritoneal cavity of a patient, the system comprising:
a pneumatically actuated diaphragm pump configured to provide positive or negative pressure to a fluid line connected to the cavity, the diaphragm pump having a pumping chamber connected to the fluid line and an actuation chamber having a valved connection to a source of positive or negative pneumatic pressure;
a controller configured to measure and control the positive or negative pressure provided by the pump via a pressure transducer in valved communication with the actuation chamber;
the controller also configured to compute a fluid flow rate through the fluid line by measuring pressures associated with the control chamber and computing the fluid flow rate from the measured pressures;
wherein the controller is arranged to control the pump by providing a first negative pressure to the fluid line, computing the fluid flow rate, 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 computed fluid flow rate exceeds a pre-determined value, and
wherein the controller is configured to control the pump to provide a positive pressure to the fluid line if the computed fluid flow rate does not exceed the pre-determined value.