A closed-loop insulin delivery system is essentially an artificial pancreas. The loop refers to the continuous cycle of feedback information: the blood glucose level changes; the change is detected by the continuous glucose monitor (CGM); the CGM sends information to the insulin pump, which adjusts its insulin output; and the blood glucose level changes again in response to the insulin. The loop is closed when this happens automatically. At present CGM-insulin pump systems are not closed-loop because the person has to make the decision of how much insulin to give rather than this happening automatically. It's hard to predict when such a system will actually become available, but prototype systems are already being used in experimental settings.
One problem with these systems is that the glucose level in the tissue fluid doesn't change as quickly as the blood glucose level, and it takes some time for insulin injected into subcutaneous fat to take effect. As a result, the insulin effect always lags somewhat compared to insulin that's made by a normally functioning pancreas, where changes in blood glucose are sensed instantaneously and the insulin is released directly into the blood. Given the serious problems -- glucose levels that are dangerously high or dangerously low -- that can result if the wrong dose of insulin is given, such systems will have to be studied extensively before they are made available for widespread use. But I'm optimistic that the technical hurdles will be overcome. Along with islet cell transplantation, closed-loop insulin delivery systems offer the biggest promise of revolutionizing the management of type 1 diabetes.
I recommend looking for big announcements about the artificial pancreas around June when the research is made public at the American Diabetes Association Meetings. This is a great time to ask the researchers (via mail, email, social media) when you or your blue-shoed loved one will be able to actually use an artificial pancreas. There are typically alot of journalists (some with diabetes themselves) that cover the meeting so there should be an abundance of information available online.
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Jennifer Shine Dyer MD, MPH
Founder, EndoGoddess LLC
Chief Medical Advisor, Duet Health (Eproximiti)
Blog/website: http://endogoddess.blogspot.com/
Website: http://www.duethealth.com/
Twitter: http://twitter.com/#!/EndoGoddess
YouTube Channel: http://www.youtube.com/user/drjenshinedyer
Email: drjenshinedyer@gmail.com
Columbus, Ohio
