Continuous glucose monitoring

Continuous glucose monitoring

Continuous glucose monitoring (CGM) systems measure glucose in tissue (in interstitial fluid) automatically about every 5 minutes. Although currently available CGMs provide detailed information about changes in glycemic control, they are not designed to replace standard blood sugar monitoring as a part of long-term diabetes self-care. Instead, the information you get using CGM can show you and your healthcare provider trends in glycemic control that give you a real-time picture of how various factors, including food, physical activity, and medication, are affecting your blood glucose. This information can then be used to fine-tune your diabetes care plan to make sure that you achieve your glycemic targets.

CGMs can be particularly useful for people who are less aware of changes in blood glucose or have a difficult time remembering to do regular monitoring. If your glucose level decreases or increases over a pre-set level, the monitor can alert you with an alarm. This can be particularly helpful in people who require intensive insulin therapy. The monitors can be used in conjunction with an insulin pump.

How do continuous glucose monitors work?

CGMs include the following components:
Glucose sensor. A CGM includes glucose sensor, which you or your healthcare provider place just under the skin on your abdomen using an inserter. The sensor is fixed to a sticky patch that keeps it in place on the skin. The sensor consists of a small electrode that generates an electrical current used to detect fluctuations in glucose levels in interstial fluid. The patch with sensor must be removed once per week and placed in a different location.
Transmitter. The sensor is connected to a transmitter that sends glucose measurements to a receiver that records this data.
Receiver. The receiver recording device for the Dexcom G4 PLATINUM is the size of a cell phone and can be carried in a purse or bag or worn on clothing or set beside a bed table (during sleep). Glucose readings are typically made every 5 minutes.1
Software. The final component of a CGM system is the software that is used to analyze glucose measurements. The software that comes with each currently approved CGMs is a program that you and your healthcare provider can use to upload data from the receiver and track trends in glucose measurements. This information can be very useful in determining whether an adjustment is needed in insulin dosing.

For people who use CGMs, in addition to using this device, they must also do regular self-monitoring of blood glucose with a finger stick several times per day to calibrate the CGM with their blood glucose meter and ensure that it is working correctly.1

The future of CGM

CGM technology has advanced considerably since its introduction in the 1990s. There have been steady improvements in CGM accuracy, design (including size and comfort), and function (hypoglycemia warning features, range of transmitter/receiver function).4

While only a small fraction of people with diabetes currently use CGM systems, sales of CGMs are increasing dramatically for both people with type 1 and type 2 diabetes. CGMs offer benefits not only to people who are insulin dependent. By providing detailed feedback on hourly fluctuations in glucose, they are becoming a powerful tool in behavior-modification, showing how food and physical activity affect glucose levels and how medications (both oral and injectable diabetes medications and insulin) can be used to optimize glycemic control.

CGM technology is following a pathway of increased integration into diabetes care. For example, the Medtronic MiniMed Paradigm REAL-Time Revel system is the first to integrate a CGM with an insulin pump system. Several companies that manufacture insulin pumps are currently developing integrated CGM/pump systems for the US market.

Research is currently underway to link continuous glucose monitoring with an artificial pancreas that can replace the nonfunctioning pancreas in people with diabetes. An artificial pancreas system would incorporate continuous glucose monitoring to both detect when blood glucose is high and automatically release an appropriate amount of insulin to lower blood glucose.

Written by: Jonathan Simmons | Last reviewed: May 2014.
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