Page 124 - Glucose Monitoring Devices

System user interface and connectivity 125

user to compensate for exercise, illness, etc. The user can deliver and program on-
demand larger, bolus doses, to cover meals and to correct for high glucose. The user
fills a cartridge with insulin and loads it into the pump. An infusion set is connected
to the insulin cartridge on one end and connected to the user with a catheter placed
subcutaneously and held in place with an adhesive patch. Infusion sets are typically
changed about every 3 days. When inulin pumps were first introduced, patients had
to “do the math” to calculate the amount of insulin needed to correct for high glucose
or compensate for meals. Insulin pumps today typically include sophisticated bolus
calculators that track insulin on board to avoid stacking of insulin, as well as offer
advanced bolus features such as the ability to extend delivery of a bolus dose over a
period of time to compensate for certain types of food and conditions such as gastro-
paresis. The latest generation of insulin pumps incorporates wireless communication
technology to connect with CGM systems to allow users to collect more information
and to automatically adjust basal insulin to avoid extreme high and low glucose [12].

Artificial pancreas
A CGM system can be integrated with an insulin pump to automatically adjust
insulin delivery based on glucose levels and individual settings such as correction
factor and insulin to carb ratios, with no user intervention required. This type of
closed-loop, automated system is called an artificial pancreas, or AP, because it stim-
ulates the function of a healthy pancreas with these automatic insulin adjustments.
This closed-loop system works by communicating with both the sensor and the
pump. Although no artificial pancreas system has been approved for use, the
Medtronic Minimed 670G was introduced as a hybrid closed loop system in 2017.
Research at the University of Virginia and the University of Padova are devel-
oping “advanced algorithms that use CGM data to automatically adjust insulin
delivery” [5]. These groups have developed the type 1 diabetes metabolic simulator
(T1DMS), an in silico computer simulator that has been accepted by the FDA as a
substitute for animal trials in certain cases. Researchers and manufacturers are
utilizing these types of simulations to further develop autonomous systems for the
administration of insulin. Fig. 6.7 shows the components of an artificial pancreas
system.
As the figure shows, the artificial pancreas system uses CGM to measure changes
in the wearer’s glucose levels. Based on this information, the algorithm calculates
adjustments to the amount of insulin being delivered by the pump.

Connected pens
Several manufacturers are working to develop a connected pen as an easier to use,
less expensive alternative to insulin pumps, enabling an artificial pancreas system
while also addressing the significant barrier to insulin pump adoption by users
who are reluctant to wear a device 24/7. Although insulin pens have been widely
used as they were introduced by Novo Nordisk in 1985, they did not provide data