Pilot Study of Closed-Loop Glucose Control in People With Type 1 Diabetes (BPK004)

Each patient had an outpatient screening evaluation, and two 22 h overnight hospital admissions separated by a 2- to 4-week waiting period. Each inpatient admission began at 15:00 and ended at 13:00 on the following day. Subjects ate dinners and lunches with carbohydrate content that was the same at admission 1 and admission 2 and had identical morning meals of Ensure Plus (Abbott Nutrition, Columbus, OH). Two days before each admission, two Freestyle Navigator CGM devices (Abbott Diabetes Care) continuous glucose monitors were applied to the patient to allow for stabilization of the sensors and for assessment of their performance.

During admission 1, open-loop control was used, with the subjects' usual insulin routine and their personal insulin pump. During admission 2, an OmniPod Insulin Management System (Insulet Corp.) was inserted and used for closed-loop control of blood glucose. Insulin lispro (Eli Lilly, Indianapolis, IN), chosen based on commercial assays available, was used during both inpatient admissions.

At the beginning of admission 2, one of the two CGM devices was designated as primary, and the closed-loop control algorithm used the data of that system, unless a problem was detected. At 17:00, the model-predictive control (MPC) was initiated in a data-collection mode, automatically receiving CGM data every minute. Administration of the predinner insulin bolus was overseen by the attending physician. MPC, closed-loop control began at 21:30 and continued until 12:00 the next day for a total of 14.5 h.

Per FDA restrictions, the algorithm did not automatically control the insulin pump. Instead, the algorithm suggested insulin boluses every 15 min, which, if accepted, were programmed into the insulin pump by the attending physician. This was done for safety reasons, allowing the physician to override insulin delivery suggestions at any time. Reference blood glucose (using a YSI Life Sciences or a Beckman glucose analyzer) was sampled every 30 min. The protocol required switching to more frequent 15 min reference blood glucose sampling if hypoglycemia occurred or was imminent. Fast-acting carbohydrate (glucose tablets or fruit juice) was given when reference blood glucose fell below 3.9 mmol/liter, regardless of the CGM readings.

Inclusion criteria

• 21 years of age or older
• Have Type 1 Diabetes Mellitus as defined by American Diabetes Association criteria or judgment of physician for at least 2 years (including those who may also be treated with metformin, thiazolidinedione, exenatide, or pramlintide).
• Use of an insulin pump
• If on antihypertensive, thyroid, anti-depressant or lipid lowering medication, have stability on the medication for at least 1 month prior to enrollment in the study
• Willingness to use lispro (Humalog) insulin for the duration of the inpatient study
• Demonstration of proper mental status and cognition for the study

Exclusion criteria

• Age <21
• Pregnancy
• Hematocrit <36% (females); <38% (males)
• Symptomatic coronary artery disease (e.g. history of myocardial infarction, history of acute coronary syndrome, history of therapeutic coronary intervention, history of coronary bypass or stenting procedure, stable or unstable angina, episode of chest pain of cardiac etiology with documented EKG changes, positive stress test or catheterization with coronary blockages >50%).
• Congestive heart failure
• History of a cerebrovascular event
• Use of a medication that significantly impacts glucose metabolism (oral steroids)
• Atrial fibrillation
• Uncontrolled hypertension (resting blood pressure >140/90)
• History of a systemic or deep tissue infection with methicillin-resistant staph aureus or Candida albicans
• Use of a device that may pose electromagnetic compatibility issues and/or radiofrequency interference with the FreeStyle NavigatorTM CGM (implantable cardioverter-defibrillator, electronic pacemaker, neurostimulator, intrathecal pump, and cochlear implants)
• Active enrollment in another clinical trial
• Allergy or adverse reaction to lispro insulin
• Known adrenal gland problem, pancreatic tumor, or insulinoma
• Current alcohol abuse, substance abuse, or severe mental illness
• Retinopathy and renal failure
• Uncontrolled anxiety or panic disorder
• Known bleeding diathesis or dyscrasia
• Renal insufficiency (creatinine >1.5)
• Any comorbid condition affecting glucose metabolism