What has anyone heard about the difference between Medtronic’s extended west infusion sets and the old ones besides 7 day vs 3-4 day wear? Everything looks the same/ package the same except says “extended wear.”
Do you supposed the cannula is a different material?
No, the cannula is exactly the same, at least in the Medtronic one. Tandem has one in the works, too, which does have a new cannula. The primary mechanism of action is that the tubing is made from a different material. They both also have a filter incorporated in the line to keep any chunky bits out of the cannula and infusion site that would physically block the flow of insulin.
What you need to understand about the insulin we take is that there’s very little of the actual hormone in the vial. It’s primarily made up of saline and LOTS of preservatives. We tend to think of preservatives as things that stop dangerous bacteria and mold from growing in our food, but in this case, most of the preservatives are actually preserving the shape of the insulin. They keep the different chains of insulin from interacting with one another. Unfortunately, the preservatives are highly volatile. They really want to escape the mix. The old tubing likes to absorb the preservatives and basically off-gas them into the environment. That leaves more opportunity for the insulin peptides to interact with one another, turning them into chunky clumps that can clog up the works… and worse yet, those clumpy chunks of insulin are completely useless in the body.
The new tubing and filter are pretty much designed to keep insulin flowing and not clumping.
If you want a refresher: Insulin is a protein, which is assembled like a long chain, but parts of the chain are kinda magnetically attracted to other parts of the chain, tying it up into a crazy shaped knot. (It’s not really magnetic, but a very similar type of physical attraction, being pulled together.) Think of a tangled, knotted chain in the bottom of a jewelry box. Those parts of the chain that “magnetically” attract other parts, well they look mighty sexy to segments on entirely different insulin chains, too. That’s how different insulin peptides get stuck together. Unfortunately, the shape of that knot is really critical. Do you remember hearing “insulin is the key the opens the door for glucose to get into your cells?”. You can take that quite literally. It’s that very specific shape of the insulin “key” that fits the very specific shaped lock of the cell receptors. If different chains of insulin get knotted up together, then they just don’t fit the lock anymore.
The shape of the insulin is also pretty important for immune reactions. Our bodies recognize individual insulin peptides, but not these giant, multi-chain insulin clumps. Those look like foreign invaders, and we send the immune calvary in to attack it, which is where some of the inflammation and subsequent scar tissue come from.
So basically, the more preservative you can keep in your insulin, the easier it flows, the better it works, and the longer you can hold off immune reactions to the site. It’s not a perfect system, but it is a better system.
4 Likes
Thank you! I really appreciate it.
1 Like