My New Friend Dexcom

Then: One of the first insulin pumps.

Now: Insulin pump, sensor, receiver.

Me finishing a triathlon in Tahoe.

May 15, 2006: Sensor Comparison Part 1

The Artificial Pancreas
What emotions do you feel after reading the words "artificial pancreas"? As a person with type 1 diabetes, I have strong feelings of excitement, relief, and hope. Recently in the media, the news of continuous glucose sensors has usually been followed by a statement saying that the artificial pancreas or closed loop system is right around the corner.

I would absolutely love to have a device that monitored my BG and gave insulin automatically, but how soon is "right around the corner"? Experts are saying 5 to 10 years. However, I've been promised the same "5 to 10 year" artificial pancreas timeline since 1990. Has time stopped or have the estimates been way off? Now that continuous glucose sensors are available, the idea of an artificial pancreas sounds simple, right? Unfortunately, an automatic insulin delivery system is incredibly complicated and technology must overcome some substantial obstacles. I think it probably won't be available for at least 10 years..

Since writing my blog, I have talked to many parents and people with diabetes who think the artificial pancreas will be available in the near future (a few short years). Many people have been disappointed after hearing the realities and obstacles of an artificial pancreas. Just the other day, one parent told me that "I was bursting her bubble" after I explained the obstacles of an artificial pancreas. For this reason, I think the realities of the artificial pancreas/closed loop system are very important to discuss. After extensive research, here's my opinion of what is needed for a true artificial pancreas.

Definition of an Artificial Pancreas/Closed Loop System
An artificial pancreas/closed loop system is a mechanical device that automatically manages and regulates the body's blood glucose values without input from the user. There are three components that make up this system: a true real time blood glucose sensor, faster insulin, and an intelligent software program. It is crucial that all components of the artificial pancreas perform with 100% accuracy for 100% of the time.

Component 1: True Real Time Blood Glucose Sensor
This sensor must accurately monitor whole blood glucose values every minute for 24 hours a day. The Dexcom and other newly available sensors measure glucose values in the interstitial fluid. There is a strong correlation between interstitial fluid and whole blood glucose values. However, whole blood glucose values are the true indicator of diabetes control and needed to dose insulin. I've found Dexcom's readings to be accurate most of the time, but not when my glucose values are changing rapidly, during exercise for instance (read more about this lag time: week 1 and week 2 of this blog). This whole blood glucose sensor will probably be surgically implanted and replaced regularly to ensure accuracy. Interstitial sensors are just starting to become available, after years of development and FDA filings. So I think we are a long way off from seeing internal whole blood sensors.

Component 2: Faster Insulin
Ultra fast insulins need to be developed for the artificial pancreas to be effective. The current rapid-acting analog insulins start working in 5 to 15 minutes, peak in 30 to 90 minutes, and lose effectiveness in 3 to 5 hours. This action isn't fast enough to normalize rapidly increasing blood glucose values, especially after meals, for instance. The current rapid-acting insulin timing can be frustrating and I've run into serious problems stacking insulin doses (continually giving insulin to correct a high blood sugar without waiting for the insulin to run its course) and eventually having a hypoglycemic reaction. New ultra fast insulins should start working immediately after delivery and remain active for a short period of time. These insulins will take time to develop, test, and receive FDA approval.

Component 3: Software Program/Algorithm
A software program will use glucose information from the sensor and deliver the correct amount of ultra fast insulin. The algorithm (complex calculation) for the software program will need to adapt to the individual's metabolic needs. Each person with diabetes has unique insulin needs which change according to activity, stress, and hormone levels. How will the software program know that I've been increased my activity levels and require less insulin than I did a week ago? How will the algorithm account for insulin resistance due to illness? What if the program malfunctions or delivers too much insulin without my knowledge? The results could be disastrous if too much or too little insulin is delivered. Managing type one diabetes is very dynamic and complex, so the software program must equally match this dynamic complexity. A few programs are in development for the artificial pancreas. The data I've seen showed that one program was able to manage BG levels while subjects were inactive and fasting, but failed to regulate BG's during meals. The artificial pancreas' software program needs to overcome some significant obstacles, which will require a large amount of time and testing.

Other Factors
There are three other important issues that the artificial pancreas must address. First, recent research has revealed that there is much more to diabetes management than just insulin. Symlin, for instance, is an important regulatory hormone that is secreted along with insulin by a fully-functional pancreas. How will Symlin be incorporated in the artificial pancreas? Second, if too much insulin is delivered, then there probably needs to be an emergency glucose delivery system. Lastly, a person without diabetes' fully-functional pancreas will start to secrete insulin when that person starts thinking about eating a meal. Will the artificial pancreas be able to account for this phenomenon?

Outlook of the Future
As you can see, diabetes technology must overcome some very significant obstacles before an artificial pancreas or closed loop system will be available. If you read or are presented with the promise of an artificial pancreas, I would ask the tough questions about the device's three components and other factors before signing on the dotted line. The idea of an artificial pancreas gives me hope that the future of my diabetes won't require fingersticks, insulin dosing, or glucose tablets. However, hope for the future won't help my diabetes today. Hope won't help me improve my next HbA1C. Hope won't help me win my next triathlon this June. Hope certainly won't decrease my risks for diabetes related complications. In fact, the future of diabetes is today. The choices I make today will affect my life and risk for diabetes related complications in the future.

Don't worry, not all hope is lost. There are some great tools available now that make diabetes management much easier than it was 16 years ago. We have rapid-acting insulins, fast glucose meters that take a pin-sized amount of blood, smart insulin pumps that calculate and deliver micro-doses of insulin, and now continuous glucose sensors. Sounds like a great party to me!

Whether it's racing triathlons, climbing mountains, traveling to Asia, or watching TV, I've managed my diabetes using today's tools and not let the disease slow me down. So I encourage you to see your diabetes team regularly and pick the best tools for your diabetes management today.


I do not work for nor am I compensated by Dexcom in any way. I'm writing this story because I think continuous glucose technology is interesting and exciting. Also, I am not a health care professional and do not give medical advice. I will share my experiences, but please check with your health care team before making any changes to your diabetes or health management.