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CGMS Update

Innovation and improvement in CGMS technology has risen dramatically over the last 2 years, paving the way for the artificial pancreas.

The development of accurate and easy-to-use continuous glucose monitoring systems (CGMS) improved diabetes treatment by providing additional temporal information on glycemia and glucose trends to patient and physician. Automation of insulin administration, also known as closed-loop (CL) or artificial pancreas treatment, has the promise to reduce patient effort and improve glycemic control. CGM data serve as the conditional input for insulin automation devices. The first commercial product for partial automation of insulin administration used insulin delivery shutoff at a predefined glucose level. These systems showed a reduction in hypoglycemia. Insulin-only CL devices show increased time spent in euglycemia and a reduction of hypo- and hyperglycemia. Improved glycemic control, coinciding with a minor decrease in hemoglobin A1c level, was confirmed in recent long-term home studies investigating these devices, paving the way for pivotal studies for commercialization of the artificial pancreas.

Although the first results from dual-hormone CL systems are promising, long-term head-to-head studies will have to prove superiority over insulin-only approaches. Now CL glucose control for daily use might finally become reality. Improved continuous glucose sensing technology, miniaturization of electrical devices, and development of algorithms were key in making this possible. Using a CGMS means that the patient has to be motivated and educated.

Striving toward near-normal glycemia leads to an increase in episodes of severe hypoglycemia and is difficult to achieve without substantial patient and healthcare provider effort. Continuous glucose monitoring (CGM) technology can aid in this quest, especially in combination with continuous subcutaneous insulin infusion (CSII). CGM allows for safe therapy intensification with hemoglobin A1c (HbA1c) reduction and can partially relieve the psychological burden of diabetes. Nonetheless, patients still need to self-monitor glucose and take carbohydrate content of food and physical activity into account when making treatment decisions. The development of subcutaneous continuous glucose sensing technology allowed for less invasive glucose sensing, making at-home application of CGM technology a reality. This evolved into combined use of CSII and CGM, also known as the sensor-augmented pump (SAP), and enabled research into automation of insulin administration (artificial pancreas/CL).

Two hundred seventy-four abstracts were screened; of these, 11 met the inclusion criteria and were included in this review. They asked major CGM manufacturers to provide information about upcoming CGM products and CL technology and performed a review of clinical trial databases.

Innovation has brought interesting new products, like flash glucose monitoring and implantable CGM systems, to, or close to, market. Flash glucose monitoring (Abbott Diabetes Care) represents a new “on-demand” application of subcutaneous glucose sensing technology, effectively using CGM technology for replacement of self-monitoring of blood glucose. Flash glucose monitoring could be seen as CGM on-demand, but the lack of (false-positive) alarms might actually be experienced as a benefit by some.

Nonetheless, through innovation in sensor technology, the overall accuracy and point precision of CGM systems have improved toward the proposed mark required for making insulin dosing decisions based on CGM data (mean absolute relative difference of <10%).

Although CGM can improve glycemic control and partially relieve the psychological burden of diabetes, patients still need to self-monitor glucose and take carbohydrate content of food and physical activity into account when making treatment decisions.

The first steps in automation of insulin administration were taken with systems that automate insulin delivery shutoff at very low glucose levels based on CGM data. If the patient is unresponsive to the CGM hypoglycemia alarm, insulin delivery will remain shut off for 2 h or until the patient restarts insulin delivery. Although stopping insulin delivery might be considered only the first form of automation of insulin administration, these systems effectively represented the first approved nonadjunct use of CGM data for insulin administration decisions.

The first commercial product using partial automation of insulin administration used insulin delivery shutoff at a predefined LGS. These systems showed a reduction in (severe) hypoglycemia compared with the most advanced treatment (SAP). Systems using additional basic predictive technology (PLGS) also showed a decrease in hypoglycemia, but at the cost of a rise in mean overnight glucose level. Hybrid insulin-only CL devices were the first to show that an increased time spent in euglycemia, and a reduction of hypo- and hyperglycemia can be expected from CL technology. Improved glycemic control, with minor decreases in HbA1c levels, was confirmed in recent long-term home studies investigating these devices, paving the way for pivotal studies for commercialization of AP. Although the first results from dual-hormone CL systems are promising, because of increased cost of consumables of these systems, long-term head-to-head studies will have to prove superiority over insulin-only approaches.

Practice Pearls:

  • The development of the CGM has had a major impact on the control of blood glucose.
  • CGMS has enabled patients to prevent hypoglycemia.
  • The future of CGMS is the basis for developing an artificial pancreas.

Researched and prepared by Steve Freed, BPHarm, Diabetes Educator, Publisher and reviewed by Dave Joffe, BSPharm, CDE

 

DCCT Research Group: Epidemiology of severe hypoglycemia in the Diabetes Control and Complications Trial. Am J Med 1991;90:450–459 [PubMed]

Hermanides J., Nørgaard K., Bruttomesso D, et al. : Sensor-augmented pump therapy lowers HbA1c in suboptimally controlled Type 1 diabetes; a randomized controlled trial. Diabet Med 2011;28:1158–1167 [PubMed]

Albisser AM., Leibel BS., Ewart TG, et al. : Clinical control of diabetes by the artificial pancreas. Diabetes 1974;23:397–404 [PubMed]