For Now, Artificial Pancreas May Be Next Best Thing to a Cure (Continued)
Does this step – which we would love to experience as soon as possible! - seem relatively straightforward compared to the jump to a completely independent closed-loop system? If you say yes, we concur; it will be difficult, but the fact that it appears possible reflects enormous progress. Indeed, at the Diabetes Technology Meeting, a panel discussion of algorithms for a closed-loop system revealed the magnitude and complexity of the challenge. One key barrier is lag time. In a natural pancreas, the sensing of rising glucose and release of endogenous insulin happens swiftly, but in an artificial system, there would be delays – both associated with insulin currently used and the current timing of continuous monitors. Yes, the continuous glucose sensor would need to see rising glucose for several readings—systems recently approved and in development currently report somewhere between every one minute and every five minutes—before signaling the release of insulin. Once released, subcutaneous insulin works with different kinetics than does natural insulin, and the steep rise of glucose levels and the rise of insulin would be mismatched assuming currently approved analogs are used. Experiments have shown that timing is critical, and mismatching insulin and glucose would likely result in at least some instability in glucose levels.
One way to resolve this issue may be an intermediate step of "closed loop with meal announcement," a term suggested in the panel discussion by Dr. Roman Hovorka of the University of Cambridge, England. In this model, user intervention is required, as the person with diabetes "boluses" in a way similar to today's insulin pumps, by keying in the desired insulin before they eat a meal. This would minimize the time lag until engineers can find a way to solve the time lag problem, but it would not have some of the advantages of a closed loop, as there would still be user involvement.
At the Diabetes Technology Meeting, there was also a focus on in-hospital closed-loop systems. Recent research has shown that tight control of blood glucose during surgical procedures and in the post-operative period significantly lowers mortality rates as well as rates of infection. In a presentation at the meeting by Dr. Anthony Furnary, we learned that his hospital had lowered the rate of mortality for cardiac procedures to 0.9% compared to the national average of 3.9% for patients with diabetes by maintaining blood glucose in a narrow range. That's three people out of every hundred who lived instead of died because of tight glucose control in the hospital, which could be further advanced by a closed-loop system. Closed-loop systems in the hospital may actually appear sooner than others, actually, since the hospital is in such a controlled environment – meaning they are stationary and are typically hooked to an IV and external factors like food and exercise aren't typically part of the equation.
While we are still at a basic level in our concept of an artificial pancreas, the possibilities are intriguing. For example, an algorithm may be an "adaptive learning" algorithm, using experience to adapt an algorithm to be individualized to the physiology of the person wearing the artificial pancreas. There could be other hormones in the system in addition to insulin. For instance, amylin, another hormone absent or defective in people with diabetes that is especially important in post-prandial glycemic control, might be infused in addition to insulin; glucagon might be incorporated into a more complicated system to raise blood glucose levels if they dropped too low.
Eventually, a well-designed artificial pancreas could bring to people with diabetes stable and reliable glucose control, freedom from hypoglycemia, and a sharp drop in complications through reduced hyperglycemia. While many hurdles remain, we are optimistic about the potential for an artificial pancreas, as there are committed and brilliant researchers working to design a closed-loop system. Yes, the notion of an artificial pancreas is exciting because it would have the power to raise the quality of life and health of people with diabetes. While we don't believe an artificial pancreas will be as routine as a pacemaker anytime in the next decade, we do hold out hopes that progress will be made on this front from which patients on insulin could mightily benefit.
Kelly Close is Editor-in-Chief of diaTribe, an electronic newsletter that helps people learn about new ways to manage diabetes better. diaTribe focuses on new drugs, devices and research. diaTribe is free and available online at www.diatribe.us.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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