Implantable Pumps in Diabetes Management
Back at the end of November, my brother sent me an article from the Wall Street Journal about an implantable pump that was being developed for people with type 2 diabetes. The design is ground breaking and could lead the way for better implantable devices, but I wondered how many people living with type 2 would opt for an implanted device, and I also wondered what people with type 1 diabetes had to say about their experience.
After reviewing some NIH studies and reading reviews and personal accounts, I am intrigued by the enthusiasm of those type 1 folks who have experienced an implantable pump. In 2011, Diabetesmine did a survey for Medtronic on market interest in an implantable device, which showed overwhelming interest in an implantable device.
I thought I would start with some basics about how an implantable pump works for type 1 diabetes.
Normally, insulin is released from the pancreas and flows directly into the liver through the portal circulation, and it is the liver that regulates normal blood sugar levels. When insulin arrives in the liver, the liver hangs on to 50% of the insulin and the other 50% is absorbed elsewhere in the body. This action is called a “positive portal-peripheral gradient of insulin.”
The way insulin is delivered to the majority of people living with diabetes (PWD) is through subcutaneous (sub-Q) injection or pump, which means that the insulin goes in the subcutaneous layer of fat and is absorbed into the body. The way we utilize insulin with sub-Q delivery is completely reversed from the body’s normal routine of “positive portal-peripheral gradient. “ This lack of ability for the body to produce the proper mechanism of naturally occurring insulin uptake is part of what makes diabetes hard to manage.
By injecting sub-Q, only 60-65% of the insulin injected is absorbed because of sub-Q enzymes that break down the injected insulin. Additionally, we all know that rotation is important, but injection sites further away from the abdomen also slow down the peak time for insulin. For rapid acting insulin, an injection in the abdomen can take 20 minutes, but from the arm it can take as much as 60 minutes.
With an implantable pump, the insulin is delivered directly into the peritoneal cavity, which is a similar delivery route for people without diabetes. The peritoneal cavity is comprised of two membranes that surround the abdomen and helps separate the organs and holds them in place. An implanted device is also referred to as an IP, intraperitoneal pump. By injecting the insulin so close to the organs, you bypass the sub-Q enzyme issue, giving you faster uptake and better insulin sensitivity. This reduces hypoglycemia, but also restores awareness of low blood sugars AND revives the response to lower blood sugar by engaging a glycogen response. (Research is so complex, sometimes it leaves me breathless!)
This medical device wonder has had a rough road, though. Battery life was not sufficient, post surgical scaring was a problem, as well as preventing infection and catheter blockage, and the most vital issue was that insulin couldn’t tolerate the body temperature and constant movement. In addition to the past problems with insulin pumps, there are other factors.
IPs have not been approved in the US market, but Medtronic sells one in France. As noted on this website, some people in the US have bought their IIP (implantable insulin pump) in France and continue to have it serviced and refilled. Medtronic seems to be committed to the implantable pump, and perhaps the new evolution of implantable pump, Freedom by Intarcia will help improve the concept and development of this interesting idea for diabetes management.