Figure 1.

An illustrative representation of a closed-loop insulin delivery system. (A) A sensor (black rectangle) transmits information about interstitial glucose levels to a handheld device about the size of a cellphone (red box) which holds a control algorithm and interacts with the user. An insulin pump (blue box in the pocket) delivers a rapid-acting insulin analog subcutaneously. Insulin delivery is modulated by the control algorithm. The communication between the system components is wireless. The control algorithm can also reside within the insulin pump. (Adapted from Hovorka [12]). (B) The closed loop replicates the physiological feedback normally provided by the β-cell.

Elleri et al. BMC Medicine 2011 9:120   doi:10.1186/1741-7015-9-120
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