Medical treatment system and methods using a plurality of fluid lines

Abstract

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.

1 . (canceled) 
     
     
         2 . An electronic circuit for to safely power a heating element of an automated peritoneal dialysis apparatus comprising:
 a heater comprising a first element and a second element;   a first relay connecting a first pole of an AC mains source to a first end of the first element;   a second relay connecting a second pole of the AC mains source to a second end of the second element;   a controller configured to control current delivery to the heater by transmitting an on signal to the first and second relays or an off signal to the first and second relays, the on signal causing AC mains current to flow through the heater, and the off signal preventing AC mains current from flowing through the heater and isolating the heater from the AC mains voltage; and   a safety relay configured to disconnect one of the first and second poles of the AC mains source from the heater wherein the safety relay is powered by a Vsafe voltage supply, the Vsafe voltage supply is configured to be controlled by one or more processors, wherein any of the one or more processors are configured to open the Vsafe voltage supply when an error is detected, whereby the heater is powered off.   
     
     
         3 . The electronic circuit of  claim 2 , wherein the controller operates on a first processor and a second controller operating on a second processor is configured to open the safety relay and disconnect the heater from the AC mains source. 
     
     
         4 . The electronic circuit of  claim 3 , wherein the safety relay is normally open and the second controller monitors the operation of the automated peritoneal dialysis apparatus and removes a signal holding the safety relay closed if a fault occurs in the automated peritoneal dialysis apparatus. 
     
     
         5 . The electronic circuit of  claim 3 , wherein the first relay and second relay are powered by the Vsafe voltage supply, the Vsafe voltage supply being configured to be controlled by one or more processors, wherein any of the one or more processors may open the Vsafe voltage supply when an error is detected, whereby the heater is powered off. 
     
     
         6 . The electronic circuit of  claim 2 , further comprising a heater select relay with two states:
 state one connects the first element in series with the second element; and   state two connects the first element in parallel with the second element.   
     
     
         7 . The electronic circuit of  claim 6 , wherein the heater select relay in the first state connects a second end of the first element to a first end of the second element and the second state connects the second end of the first element to the second pole of the AC mains source and connects the first end of the second element to the first pole of the AC mains source. 
     
     
         8 . The electronic circuit of  claim 6 , further comprising a current sensor on a line connecting one of the first or second poles of the AC mains source to the heater, wherein the controller receives a signal from the current sensor and switches the state of the voltage select relay based on the signal from the current sensor. 
     
     
         9 . The electronic circuit of  claim 6 , further comprising a current sensor on a line connecting one of the first or second poles of the AC mains source to the heater, wherein the heater select relay is initially in state one, wherein the controller receives a signal from the current sensor and switches the heater select relay to state two when a current detected by the current sensor is less than a predetermined value. 
     
     
         10 . The electronic circuit of  claim 6 , further comprising a current sensor on a line connecting one of the first or second poles of the AC mains source to the heater, wherein before a therapy is started, the heater select relay is in state one, and the controller transmits a predetermined duty cycle to the first relay and second relay and receives a signal from the current sensor, the controller switches the heater select relay to state two if the signal is less than a predetermined value, and the controller does not change the heater select relay for a remainder of the therapy if the signal is greater than the predetermined value. 
     
     
         11 . The electronic circuit of  claim 2 , further comprising a heater pan with a temperature sensor, wherein the controller receives a temperature signal from the temperature sensor and varies the duty cycle of the first relay and second relay to achieve a pre-determined desired temperature signal. 
     
     
         12 . The electronic circuit of  claim 6 , wherein the heater select relay is an electro-magnetic relay and the first relay and second relay are solid state relays. 
     
     
         13 . An electronic circuit 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.   
     
     
         14 . The electronic circuit of  claim 13 , wherein the controller operates on a first processor and further comprising a safety relay configured to disconnect the heater from the power source upon the loss of a signal from a second controller on a second processor. 
     
     
         15 . The electronic circuit of  claim 14 , wherein the safety relay is normally open and the second processor monitors the operation of the automated peritoneal dialysis apparatus and removes a signal holding the safety relay closed if a fault occurs in the automated peritoneal dialysis apparatus. 
     
     
         16 . The electronic circuit of  claim 14 , wherein the safety relay is powered by a Vsafe voltage supply, the Vsafe voltage supply is configured to be controlled by one or more processors, wherein any of the one or more processors may open the Vsafe voltage supply when an error is detected, whereby the heater is powered off. 
     
     
         17 . The electronic circuit of  claim 14 , further comprising at least one PWM element to limit power supplied to the heater, wherein the at least one PWM element is powered by a Vsafe voltage supply, the Vsafe voltage supply is configured to be controlled by one or more processors, wherein any of the one or more processors may open the Vsafe voltage supply when an error is detected, whereby the heater is powered off 
     
     
         18 . A control system 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.   
     
     
         19 . The control system of  claim 18 , wherein the gating circuit operates the solid state relay through optical transmission. 
     
     
         20 . The control system of  claim 19 , wherein the optical transmission is performed using a light emitting diode of an opto-isolator. 
     
     
         21 . The control system of  claim 18 , wherein the solid state relay comprises a triac or a pair of silicon control rectifiers. 
     
     
         22 . The control system of  claim 18 , wherein the solid state relay 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, and wherein the pulse width modulated signal reproduced or transmitted by the gating circuit operates both the solid state relay and the second solid state relay. 
     
     
         23 . The control system of  claim 18 , wherein the solid state relay 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, wherein 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 wherein 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.