Method and system for closed-loop control of an artificial pancreas

Abstract

Methods and systems for controlling an insulin pump in response to glucose measurements are responsive to a base insulin delivery profile and a temporary insulin delivery profile. These can be used, e.g., to control blood glucose level of a subject using a continuous glucose monitor and an insulin infusion pump. During a selected time range, an insulin amount for the pump to supply is determined using the temporary insulin delivery profile. Outside that time range, the insulin amount is determined using the base insulin delivery profile. The temporary insulin delivery profile can specify an exact amount to be supplied (a “hard” profile), a nominal amount to be supplied if doing so does not drive glucose out of a desired zone (“soft”), or a soft profile with a minimum amount of insulin to be delivered (“semi-soft”).

1 . A method to control an insulin infusion pump responsive to a controller that receives data from a glucose sensor, the method comprising:
 measuring a glucose level of a physiological fluid from a user with the glucose sensor; and   via the controller, automatically:
 receiving, from the glucose sensor, respective glucose level measurements for each time interval of a series of discrete time intervals; 
 receiving a temporary insulin delivery profile extending over a selected time range of the time intervals; 
 providing a signal indicating receipt of the temporary insulin delivery profile; 
 determining a candidate insulin delivery amount for a selected one of the time intervals based on a model predictive controller that:
 predicts an excursion of the glucose level from a selected target glucose range using at least some of the glucose measurements; 
 computes an estimated insulin delivery amount; and 
 adjusts the estimated insulin delivery amount to provide the candidate insulin delivery amount, the adjustment performed in accordance with the predicted excursion a base insulin delivery profile when the selected time interval is outside of the selected range, and in accordance with the predicted excursion and with the temporary insulin delivery profile when the selected time interval is within the selected range; 
 determining an approved insulin delivery amount from the candidate insulin delivery amount; and 
 
 commanding the infusion pump to deliver the approved insulin delivery amount. 
   
     
     
         2 .- 21 . (canceled) 
     
     
         22 . The method of  claim 1 , wherein receiving the temporary insulin delivery profile comprises receiving a profile modifier and applying the profile modifier to the base insulin delivery profile to produce the temporary insulin delivery profile. 
     
     
         23 . The method of  claim 1 , wherein the adjustment comprises adjusting the estimated delivery amount in accordance with the predicted excursion and the temporary insulin delivery profile and constraining the calculated insulin delivery amount to be at least a difference between the temporary insulin delivery profile and the base insulin delivery profile in the selected time interval when the selected time interval is within the selected range. 
     
     
         24 . The method of  claim 1 , wherein determining the approved insulin delivery amount comprises providing the candidate insulin delivery amount as the approved insulin delivery amount. 
     
     
         25 . The method of  claim 1 , wherein determining the approved insulin delivery amount comprises reducing the candidate delivery amount to provide the approved insulin delivery amount according to a safety model. 
     
     
         26 . The method of  claim 1 , wherein the temporary insulin delivery amount defines a first subrange and a second subrange of the selected time range and specifies a higher rate of insulin delivery in the first subrange and a lower rate of insulin delivery in the second subrange. 
     
     
         27 . The method of  claim 1 , further comprising receiving an activation signal and, in response to the activation signal, retrieving the stored base insulin delivery profile and retrieving or determining the insulin delivery amount. 
     
     
         28 . A method to control an insulin infusion pump responsive to a controller that receives data from a glucose sensor, the method comprising:
 measuring a glucose level of a physiological fluid from a user with the glucose sensor; and   via the controller, automatically:
 receiving, from the glucose sensor, respective glucose level measurements for each time interval of a series of discrete time intervals; 
 receiving a temporary insulin delivery profile extending over a selected time range of the time intervals; 
 calculating a candidate insulin delivery amount for a selected one of the time intervals based on a model predictive controller that:
 when the selected time interval is outside the selected range, predicts an excursion of the glucose level from a selected target glucose range using at least some of the glucose measurements; 
 computes an estimated insulin delivery amount; and 
 adjusts the estimated insulin delivery amount to provide the candidate insulin delivery amount, the adjustment performed in accordance with the predicted excursion and a base insulin delivery profile; and 
 when the selected time interval is in the selected range, retrieves the candidate insulin delivery amount for the selected time interval from the temporary insulin delivery profile; 
 
   determining an approved insulin delivery amount based on the candidate insulin delivery amount; and   commanding the infusion pump to deliver the approved insulin delivery amount.   
     
     
         29 . The method of  claim 28 , wherein determining the approved insulin delivery amount comprises using a safety model to determine whether a hypoglycemic excursion is predicted and, if so, reducing the candidate delivery amount to provide the approved insulin delivery amount.