Fully Closed

Treating Type 1 Diabetes as a teenager can be extremely difficult for many reasons. During high school and college, adolescents experience hormonal variations, stress, and abnormal sleeping and eating patterns. All of these elements influence the regulation of blood sugar. Being diagnosed around this time (13- 20 years old) is a challenge because of these reasons. Knowing all of this, we came across an article presented by the American Diabetes Association in 2008 which discussed the efficiency of a fully closed- loop system (mimicking a healthy pancreas) versus a semi-automated hybrid closed-loop system (mimicking a healthy direction- oriented pancreas). In this experiment, 17 adolescents with Type 1 Diabetes were used as subjects. The integral difference between the two systems is that with the hybrid closed- loop system, rather than the pump dictating the insulin dose, the person does. Also, the hybrid closed- loop system gives the preemptitive bolous dose, whereas the closed-loop does not.

The major variable of the experiment was testing blood glucose levels at various points during the day. They also measured A1C levels and the frequency of hypoglycemic events. The results proved that the variation between the fully closed and hybrid loop were minimal (1 to 2 points). The fully closed system did nevertheless prove to be slightly more efficient. This was due to the fact that the insulin pump could administer pre-meal bolus doses which broke down the initial insulin resistance and smoothed out the blood sugar fluctuation.
Glucose levels with FCL control almost never exceeded 300 mg/dl. 85% of all sensor glucose levels were between 70 and 180 mg/dl in the FCL group during the 24-hour study period. During standard open-loop pump therapy, during which time only 58% of sensor glucose values were between 70 and 180 mg/dl. These subjects were already in excellent control, with mean A1C level of only 7.1%.

Hypoglycemia is a main concern as the best blood sugar control comes with the price of potential hypoglycemia. Hypoglycemia occurred only at nighttime in the experiment. Two patients of the Hybrid control group suffered hypoglycemic events in which blood glucose levels reached 57 (mg/dl). The fully closed loop control group patient reached 51 (mg/dl). These episodes were easily fixed with 15g of carbohydrates.

http://care.diabetesjournals.org/content/31/5/934.full#sec-13