An implantable subcutaneous glucose sensor array in ketosis-prone rats: closed loop glycemic control.
A closed loop system of diabetes control would minimize hyperglycemia and hypoglycemia. We therefore implanted and tested a subcutaneous amperometric glucose sensor array in alloxan-diabetic rats. Each array employed four sensing units, the outputs of which were processed in real time to yield a unified signal. We utilized a gain-scheduled insulin control algorithm which rapidly reduced insulin delivery as glucose concentration declined. Such a system was generally effective in controlling glycemia and the degree of lag between blood glucose and the sensor signal was usually 3-8 min. After prolonged implantation, this lag was sometimes longer, which led to impairment of sensor accuracy. Using a prospective two-point calibration method, sensor accuracy and closed loop control were good. A revised algorithm yielded better glycemic control than the initial algorithm did. Future research needs to further improve calibration methods and reduce foreign body fibrosis in order to avoid a time-related increase in lag duration.
Ward
W Kenneth
WK
Legacy Clinical Research and Technology Center, Portland, OR 97232, USA. kward@legacyglucosesensor.org
Wood
Michael D
MD
Casey
Heather M
HM
Quinn
Matthew J
MJ
Federiuk
Isaac F
IF
D000465:Algorithms; D000496:Alloxan; D000818:Animals; D001786:Blood Glucose / Q000032:analysis*; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy*; D016883:Diabetic Ketoacidosis / Q000175:diagnosis / Q000188:drug therapy*; D015918:Infusion Pumps, Implantable; D007332:Insulin Infusion Systems; D023421:Models, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley
D001786:Blood Glucose; D000496:Alloxan