Figure 5
" Automatic Insulin Infusion System" (AIIS) for Inpatient Treatment: Severe positive challenge. "Automatic Insulin Infusion System" (AIIS) for Inpatient Treatment: Severe positive challenge given by the sudden intravenous injection of 10 grams of glucose into a 70-Kg patient with Type-1 diabetes mellitus and average hepatic sensitivity (Sh = 0.5) as shown in the 23d row of Table 1. (A) Glycemia [mg × dL-1]. The arrow shows the start of the severe positive challenge. The black area under the curve is the overshoot that lasts for 15 minutes. Although the time it takes for the blood glucose to return to a value just below 120 mg × dL-1 is 16 minutes, the real TS = 120 minutes, which is the time it takes for the system to stabilize itself within the 90-120 mg × dL-1 range. There is no undershoot, as the glycemia does not fall below 60 mg × dL-1. (B) As in the case of figure 4-B, the insulin infusion rate moves around an average of 1.0 I.U. × h-1 before the challenge. Immediately after the challenge, the insulin infusion rises up to 12.0 I.U. × h-1 during 15 minutes. This was followed by minimal infusion rate for the next 45 minutes (KVO for the Abbott pump) in order to avoid excessive hyperinsulinemia (see 5-C, below). Please observe that the insulin infusion rate is not a continuous function but a step function representing orders given by the controller to the clinical infusion pumps, whose flow rate has to be adjusted by steps not smaller than 0.1 mL × h-1 (see "Actuators", part I-D in methods section, above). (C) The AIIS response to the severe positive challenge produced a period of hyperinsulinemia that lasted for 55 minutes. The elevated levels of serum insulin were the result of the sharp increase in insulin infusion (as shown in 5-B, above), and its duration was limited to 55 minutes thanks to the 45-minute period of minimal insulin infusion that ensued. The result was a undershoot-free normalization of glycemia.