Medical treatment system and methods using a plurality of fluid lines
A medical treatment system, such as peritoneal dialysis system, may include control and other features to enhance patient comfort and ease of use. For example, a peritoneal dialysis system may include a control system that can adjust the volume of fluid infused into the peritoneal cavity to prevent the intraperitoneal fluid volume from exceeding a pre-determined amount. The control system can adjust by adding one or more therapy cycles, allowing for fill volumes during each cycle to be reduced. The control system may continue to allow the fluid to drain from the peritoneal cavity as completely as possible before starting the next therapy cycle. The control system may also adjust the dwell time of fluid within the peritoneal cavity during therapy cycles in order to complete a therapy within a scheduled time period. The cycler may also be configured to have a heater control system that monitors both the temperature of a heating tray and the temperature of a bag of dialysis fluid in order to bring the temperature of the dialysis fluid rapidly to a specified temperature, with minimal temperature overshoot.
1. A method of configuring heating elements of an electrical heater for a peritoneal dialysis apparatus, the electrical heater comprising two heating elements, an end of each heating element connected to a common point, the method comprising:
configuring the heating elements initially in a series configuration;
connecting the electrical heater to line voltage;
measuring electrical current flow through the electrical heater;
determining from the measured current flow whether the line voltage is in a range of about 100-120 volts, or in a range of about 200-240 volts;
providing a user of the peritoneal dialysis apparatus with information about the determined line voltage; and
receiving a verification signal from the user before finally configuring the heating elements in either a series configuration or a parallel configuration based on the determined line voltage.
2. A heating system for a peritoneal dialysis apparatus comprising:
a heater bag containing dialysate solution and positioned on a heater pan;
a pumping apparatus configured to pump dialysate into and out of the heater bag;
an electrical heating element to heat the heater pan;
one or more heater pan temperature sensors to detect a temperature of the heater pan;
a dialysate temperature sensor mounted in the heater pan, thermally isolated from the heater pan, and configured to contact an outer surface of the heater bag to measure a dialysate temperature of dialysate in the heater bag; and
a controller programmed to perform an inner control loop process that modulates electrical power provided to the heating element to achieve a target heater pan temperature as measured by the one or more heater pan temperature sensors, and programmed to perform an outer control loop process that determines the target heater pan temperature based on a difference between a pre-determined target dialysate temperature and the dialysate temperature as measured by the dialysate temperature sensor.
3. A liquid heating system comprising:
a heater bag containing a liquid and positioned on a heater pan;
a pumping apparatus configured to pump liquid into and out of the heater bag;
an electrical heating element to heat the heater pan;
one or more heating pan temperature sensors to detect a temperature of the heater pan;
a liquid temperature sensor mounted in the heater pan, thermally isolated from the heater pan, and configured to contact an outer surface of the heater bag to detect a liquid temperature of liquid in the heater bag; and
a controller programmed to perform an inner control loop process that modulates electrical power provided to the heater element to achieve a target heater pan temperature as measured by the one or more heater pan temperature sensors, and programmed to perform an outer control loop process that determines the target heater pan temperature based on a difference between a pre-determined target liquid temperature and an equilibrium temperature, wherein
the equilibrium temperature is a weighted average of the liquid temperature and the heater pan temperature, the liquid temperature being weighted by a thermal capacitance, mass, or volume of liquid present in the heater bag, and the heater pan temperature being weighted by a thermal capacitance, mass, or volume of the heater pan.
4. A liquid heating system comprising:
a heater bag containing a liquid and positioned on a heater pan;
a pumping apparatus configured to pump liquid into and out of the heater bag;
an electrical heating element to heat the heater pan;
one or more heating pan temperature sensors to detect the temperature of the heater pan;
a liquid temperature sensor mounted in the heater pan, thermally isolated from the heater pan, and configured to contact an outer surface of the heater bag to detect a liquid temperature of liquid in the heater bag; and
a controller programmed to perform an inner control loop process that modulates electrical power provided to the heater element to achieve a target heater pan temperature as measured by the one or more heater pan temperature sensors, and programmed to perform an outer control loop process that determines the target heater pan temperature based on a difference between a pre-determined target liquid temperature and an equilibrium temperature, wherein
the equilibrium temperature is a weighted average of the liquid temperature and the target heater pan temperature, the liquid temperature being weighted by a thermal capacitance, mass, or volume of liquid present in the heater bag, and the target heater pan temperature being weighted by the thermal capacitance, mass, or volume of the heater pan.
5. The liquid heating system of claim 4 , wherein the inner control loop process includes an integrator element that generates a integral value with anti-windup logic to limit an integral value of a difference between the target heater pan temperature and the measured heater pan temperature.
6. The liquid heating system of claim 4 , wherein the inner control loop process includes a maximum heater power command, the outer control loop process includes a maximum target heater pan temperature, and the outer control loop process includes an integrator element that is applied if:
a rate of change of the liquid temperature is less than a pre-determined value;
the liquid temperature is within a pre-determined range of the target liquid temperature;
the amount of liquid in the heater bag is greater than a pre-determined value; or
neither an output value of the inner control loop process, nor an output value of the outer control loop process are at pre-determined maximum values.
7. The liquid heating system of claim 4 , wherein the controller is configured to set the electrical power to zero if the pan temperature exceeds a pre-determined value.