Closed loop system for controlling insulin infusion
A closed loop infusion system controls the rate that fluid is infused into the body of a user. The closed loop infusion system includes a sensor system, a controller, and a delivery system. The sensor system includes a sensor for monitoring a condition of the user. The sensor produces a sensor signal, which is representative of the condition of the user. The sensor signal is used to generate a controller input. The controller uses the controller input to generate commands to operate the delivery system. The delivery system infuses a liquid into the user at a rate dictated by the commands from the controller. Preferably, the sensor system monitors the glucose concentration in the body of the user, and the liquid infused by the delivery system into the body of the user includes insulin.
1. A system for calculating the amount of liquid to be infused into a body of a user, the system comprising:
means for obtaining a blood glucose concentration of the user;
means for generating a controller input based on the blood glucose concentration; and
means for generating infusion calculations by a proportional plus, integral plus, derivative (PID) controller from the controller input using at least one preset controller gain;
wherein the at least one preset controller gain includes at least one tuning parameter that further modifies the commands generated by the PID controller to create an insulin concentration profile that more closely resembles the insulin concentration profile that would be generated by the release of insulin by beta cells in an individual with a healthy normally functioning pancreas; and
wherein the at least one tuning parameter is a lead/lag compensator.
2. The system according to claim 1 , wherein the blood glucose concentration is obtained through an IV catheter connected to the body of the user.
3. The system, according to claim 2 , wherein a vascular sensor is inserted through the IV catheter to be in contact with the blood and obtain the blood glucose concentration of the user.
4. The system according to claim 2 , wherein an automatic blood withdrawal system is used to obtain the blood glucose concentration of the user.
5. The system according to claim 1 , wherein the blood glucose concentration is obtained through a subcutaneous sensor in contact with interstitial fluid.
6. The system according to claim 1 , wherein the blood glucose concentration is obtained by using a blood glucose meter.
7. The system according to claim 1 , further comprising means for infusing liquid based on the infusion calculations from the PID controller, wherein the liquid is infused through an IV catheter connected to the body of the user.
8. The system according to claim 1 , wherein the at least one preset controller gain is selected by a method that includes the step of measuring an insulin response of at least one individual with a healthy normally functioning pancreas and calculating the at least one controller gain that causes the commands to generally match the insulin response of the at least one individual.
9. The system according to claim 1 , wherein an additional tuning parameter is an integrator leak.
10. The system according to claim 1 , wherein an additional tuning parameter is an integrator clip.
11. The system according to claim 1 , wherein an additional tuning parameter is a feedback of predicted plasma insulin.