The Closed Loop for Diabetes: Is the Dream Still Alive?


Endocrinology is not known for being very heavy on anything "tech", aside from insulin pumps and CGMS (continuous glucose monitoring sensor) devices.

With this being my first contribution to MDNG, I was initially not sure which tack to take. Endocrinology is not known for being very heavy on anything “tech”, aside from insulin pumps and CGMS (continuous glucose monitoring sensor) devices. I guess that is one reason we tend not to be the millionaires in medicine, but that is another blog for another time…

Back to this issue: I thought, why not start with the biggie, the one big hope in our field that could change it entirely (and possibly put me out of work)—the artificial pancreas, or the “closed loop” system as it is called. When I was in medical school several moons ago this was really taking off, all this hope of an artificial pancreas. It would cure diabetes for good, everyone said. During my interviews for residency I met a fellow interviewee who was doing research on some sort of intra-abdominal device that would release insulin at slow levels. I was impressed, and jealous that he was so much at the leading edge of this new-world-for-diabetes. But it is now many years later, and we’ve got some great insulins and other medications, but where is the long awaited “ cure” for diabetes?

The closed-loop system for diabetes is still very much on the front burner for many companies and research institutions. With our current technology in insulin pumps coupled with the CGMS devices, we are close. The mega-medtech company Medtronic made a huge leap towards the closed loop system a few years ago with their introduction of the Minimed Paradigm Insulin pump and CGMS, with measurements taken every 5 minutes and automatically communicated to the insulin pump. For those not quite ready to accept a second indwelling needle with the CGMS and would rather have a glucometer, there is no need for juggling multiple devices: Deltec makes a Cozmore Insulin Technology system which incorporates a Cozmo pump that attaches to the glucometer, so it all travels neatly in one device. The excitement, the excitement—we don’t have stents or scopes in Endocrine, but these are pretty cool gadgets.

With these devices, we are closing in on our goal. A recent study in Diabetes Care Feb 2008 used the Paradigm system in a pediatric population as a “fully automated closed loop” in intervals over a 34-hour period and had good control of particularly overnight glucose levels. However the better control came with priming doses given with the pump (the “hybrid closed loop” model), requiring human factor intervention/action. Delays in insulin action and peaks secondary to variations in subcutaneous absorption also complicate matters further1.

As you notice, the human factor is still essential in even these devices that approximate the closed loop. The Paradigm is probably the closest we have at this time, and while it will monitor and calculate even down to the smallest detail you can imagine programmed into its complicated system, it still requires a person to validate the insulin calculated, and all importantly, PRESS the button to deliver the insulin. The fully automated model used in the previously referenced pediatric study is not how the Paradigm is commonly used in standard practice, but rather in the research setting. CGMS devices still require calibration with a regular glucometer as well, although on a less frequent basis.

So stay tuned because several companies are hot on the trail of Medtronic in their attempts to bring their own similar devices to the market. In addition, small trials are underway here and abroad using implantable insulin pumps as well as the true “artificial pancreas” made of special polymers encapsulating pig islet cells. I wonder if my interview colleague is on this team…

Will we get there? Most likely yes, and I will lose many patients at that time. Is it close? Personally I think we are still a few years off from a widely available true closed system where everyone can do what non-diabetics do: eat when/what they want and not think about it, then let something else do the work for us. In the meantime we will continue to marvel at the precision and perfection of our innate closed loop, encourage some of our brightest minds to work on it, and hope for the future. Let the dream live on.


1.Weinzimer et al. Fully Automated Closed-Loop Insulin Delivery vs. Semi-Automated Hybrid Control in Pediatric Patients with Type 1 Diabetes using an Artificial Pancreas. Diabetes Care 31:934-939, 2008.

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