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Tubing From Heaven: taking a look at the Medtronic and Steadi-Set Infusion Devices

article by gary scheiner

After nearly four decades of living with T1D and seeing plenty of new products fail to live up to expectations, it takes a lot to get me genuinely excited.  But there is something new (and improved) that can make a real difference in the lives of insulin pump users.  It has nothing to do with algorithms or programmable features.

It’s about the tubes that deliver the insulin from the pump into our bodies – collectively referred to as “infusion devices.”

OK, maybe I need to take a long, hard look at my life if this is what gets me excited.  But consider the last time you said to yourself, “I did the same things I did yesterday, but my blood sugar was completely different.”  This happens to me all the time, so chances are it wasn’t all that long ago for you.  In fact, I would suggest that at least half of the inconsistencies we see from day-to-day can be attributed to issues with the pump’s infusion device.

Infusion devices are truly where the “rubber meets the road.”  No car, regardless of the model, will perform well on a bad set of wheels.  And no insulin pump, with or without a sophisticated closed-loop system, will perform well if the insulin fails to reach the bloodstream in a consistent, predictable manner.  Unfortunately, infusion site issues continue to get in the way of daily glucose management for a large proportion of pump users.  These issues include partial spoilage of insulin, leakage, and malabsorption due to irritation or inflammation below the skin.  These issues account for a great deal of the day-to-day glucose variability that many of us see.

The good news is that we’re on the precipice of a big change for the better.  Both Medtronic and Tandem are investing in the development of better, longer-lasting infusion devices designed to minimize unpredictable glucose variability.  Interestingly, the two companies are tackling the problem from opposite ends of the infusion path.

Medtronic recently launched their new set under the name Medtronic Extended (how creative!).

Based on the already-existing Mio Advance, Medtronic’s engineers made virtually no changes to the set itself.  Instead, they focused on the insulin that makes its way into the body.  Their theory is that impurities, particulates and broken pieces of insulin called “fibrils” (caused by agitating the insulin in the pump) are the source of many of the problems seen at infusion sites.  They designed a filter, built into the cap that screws onto the reservoir, to keep impurities from entering the tubing.  They also redesigned the tubing to make sure the insulin’s preservative stays with the insulin until it enters the body.  This helps ensure that the insulin is at full strength when it is infused.

One minor change was made to the on-skin part of the infusion set.  Since canula “movement” can lead to canula crimping and site irritation, Medtronic Extended features stronger adhesive to minimize vertical movement of the canula below the skin.  Pre-launch studies on the extended wear set were very positive.  The set lasted a full seven days for the vast majority of users and produced a 2.8% improvement in time-in-range compared to traditional three-day sets.  Users reported less site discomfort, fewer accidental site pull-outs, and far fewer unexplained high glucose levels.medtronic extended infusion set

Here at Integrated Diabetes Services, we had a chance to try Medtronic Extended personally and provided samples to a number of our patients.

The results have been excellent.  Although not everyone was able to use the sets for a full seven days, we found that they do indeed last longer and produce far fewer site issues than traditional sets.  We are now recommending the Medtronic Extended set to all of our Medtronic pump-using patients.

tandem steadisetTandem Diabetes’ approach has been quite different, focusing more on the canula end of the infusion pipeline.

Last year, Tandem acquired Capillary Biomedical, a biotech company developing an extended-wear infusion set called Steadi-Set.  Their design features a very flexible canula reinforced by a thin steel coil that is wound within the canula itself.  The coil makes the canula virtually pinch-proof and kink-proof.  The 13mm canula, inserted at a 30-degree angle, has three opening along its length in addition to an opening at the tip so that obstacles won’t prevent the insulin from flowing as it should.  Like Medtronic, Capillary Bio also re-engineered the tubing in order to minimize the loss of all-important preservative as insulin flows from the pump towards the body.  Studies conducted on Steadi-Set showed excellent results:  7+ days of virtually trouble-free wear and more rapid insulin action during the later stages of set usage.

I had a chance to wear a Steadi-Set myself (without insulin) last year.  The inserter was extremely easy to use, the insertion was painless, the adhesive held the set on securely for a full seven days, and I experienced no site irritation or inflammation.  Tandem is working aggressively to bring this infusion set to market for the benefit of Tandem pump users.

steadiset inserterIf you are using a pump that offers an extended wear infusion set, by all means give it a try.  If not, there are several things you can do to minimize the incidence of infusion issues that contribute to unpredictable glucose levels:

  • Change your infusion sites BEFORE problems arise. Generally, the longer a set is worn in one place, the greater the chance for problems.  For some, that means changing more often than the 3-day intervals recommended by most infusion device manufacturers.
  • Select an infusion set that is less likely to contribute to problems.  Most (but not all) people benefit from using sets that are inserted at a 30-degree angle compared to a 90-degree angle.  Those who experience frequent occlusions or “kinking” of their flexible canula can benefit from using a steel needle set.
  • Rotate your sites carefully so that you don’t repeat the same spot for at least a month.  This can be accomplished by staying on one side of your body for multiple site changes, moving the infusion set just a few inches at a time.  An organized rotation pattern works better than random placement.
  • Ensure that your insulin is at full strength by minimizing exposure to heat and direct sunlight.  When heat exposure is unavoidable, replace the insulin, tubing and infusion device right afterwards.
  • Keep your infusion set stuck securely to your skin.  Less movement is better, so consider applying extra tape over the set or using wipes that aid adhesion prior to inserting.
  • At the FIRST sign of site problems (redness, inflammation, discomfort), move your infusion set to a new spot.  Likewise, don’t hesitate to change your set if you are experiencing unexplained elevated glucose levels.  From my experience, nine times out of ten, this will resolve the problem.
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