Page 326 - Glucose Monitoring Devices

The algorithms: the final piece of the puzzle 333

The algorithms: the final piece of the puzzle
With the building blocks of continuous glucose monitors and CSII pumps in place,
what remained was the creation of an algorithm using sensor data to automatically
adjust insulin doses. Three primary control algorithms have emerged:
(1) Proportional integral derivative (PID)
(2) Model predictive control (MPC)
(3) Fuzzy logic (FL)
The PID algorithm primarily uses a linear model, while the MPC algorithm uses
a compartmental model of glucose and insulin dynamics. The FL system is designed
to imitate the reasoning used to adjust insulin doses by diabetes caregivers. Fig. 16.2
[36] reviews the multitude of factors and parameters utilized in the creation of a
closed-loop system.

FIGURE 16.2
Taxonomy of the AP design. A specific AP configuration is created by selecting options for
each of the major elements shown in the figure. Solid lines demonstrate connections that
are always present and dashed lines represent connections that may only be present in
some configurations. The tuning, model, and desired glucose concentration are all part of
the controller, as signified by the black arrows. Green color distinguishes physiological
states or properties from measured or digital signals. Black lines are used to indicate
predetermined features of a block, and blue lines indicate signals or actions conducted
during closed-loop operation.
Used with permission from Doyle FJ, 3rd, Huyett LM, Lee JB, Zisser HC, Dassau E. Closed-loop artificial
pancreas systems: engineering the algorithms. Diabetes Care 2014;37(5):1191e1197.