The Future of Infusion Sets
With the artificial pancreas on the horizon, today’s infusion sets are ready for a refresh
As diabetes technology evolves toward an eventual artificial pancreas, we’re learning more about the sophisticated algorithms needed to integrate insulin pumps with continuous glucose monitors (CGMs). We hear about cutting-edge glucose sensors and even new insulin pump platforms designed for ease of use.
When was the last time you heard anything exciting about insulin infusion sets? They are akin to the floppy disk of artificial pancreas systems—a technology suited to past insulin pump needs that have long been outdated. They are also the workhorses of insulin pump therapy, slipping under the skin and delivering variable amounts of insulin without causing a major bodily riot: inflammation, infection, or rejection.
Yet despite all of that, infusion sets may be the least-studied aspect of the artificial pancreas pathway. How must they evolve in order to accommodate an artificial pancreas? Future infusion set designs need to address three major concerns:
Days of Wear
Current infusion sets have short lifespans (about two to three days) for a number of reasons: Flexible plastic cannulas, the alternative to stainless steel needles, are prone to bend or kink under the skin. Plus, needles and cannulas may become clogged by clumps of cells or insulin, blocking insulin flow. Another concern is that the tissue surrounding the infusion set has a reduced ability to absorb insulin after several days of use. This causes higher blood glucose levels—even when taking the correct doses of insulin. What’s more, wearing an infusion set for longer than recommended ups the risk of infection. An infection, which can lead to pain, itching, swelling, and even an abscess if left untreated, can make an insertion site useless.
Because CGM sensors can be worn for six to seven days before replacement, infusion sets need to last longer as well. One approach to making them last longer: a novel infusion set in development by Becton, Dickinson, and Co. that utilizes “BD FlowSmart” technology (more on that here). This flexible infusion set has an additional hole in the side of the cannula to help reduce clogging by offering a secondary exit for insulin to get into the tissue. More clinical data is needed to see if the new technology allows users to wear infusion sets for longer periods of time.
There are other approaches as well. Some companies have explored reducing insertion site infections by coating the cannula with antimicrobial compounds. Still others have employed additives such as hyaluronidase to try to increase set wear time, but so far this has only proven to make insulin work faster (which it’s intended to do).
For years, both manufacturers and people with diabetes have envisioned a combined CGM sensor and infusion set. The inherent roadblock is the disparity in wear lengths: How do you incorporate a three-day infusion set with a seven-day sensor? The Duo system from Medtronic (available only in Europe) consolidates the infusion set and glucose sensor into the same site on the skin—with two insertions only millimeters apart. Although this means there’s just one technology hub on the skin, it requires that both the sensor and infusion set be changed after three days.
Lack of Innovation
Infusion sets of the future might not resemble the past—and that’s okay. For infusion sets to work with artificial pancreas systems, device designers may need to think beyond the current paradigm. How about microneedles, eyelash-sized spines that deliver insulin to surface skin layers that absorb faster than deeper layers? What about skin sensors that tell you when to change an infusion set? How about a system that would automatically change your insulin doses over the life of an infusion set based on day-to-day insulin absorption?
I believe these innovations are the future of insulin infusion and the artificial pancreas. Until then, working with your diabetes educator on optimal site selection, site rotation, and set type is crucial for pumping success. Yet it is exciting to think beyond the floppy disk, don’t you think?
Laurel Messer, RN, MPH, CDE, is a certified diabetes educator and clinical research nurse at the Barbara Davis Center for Diabetes. She has been working with children and adults with type 1 diabetes for over 10 years and currently manages pediatric artificial pancreas research trials.