We Need More Research and Better Designs for Insulin Infusion Sets

An insulin infusion set (IIS) is an indispensable conduit in insulin pump systems that transfers insulin from the reservoir to the subcutaneous tissue. Some form of IIS is required for all pumps, including patch pumps. Transfer of insulin across the skin occurs through a stainless steel needle or through a Teflon cannula once its steel needle has been removed during the insertion process. With their ease of insertion, steel needles are inserted manually while Teflon catheters can be inserted manually, with an auto-insertion device, or in some cases either. An insulin pump delivers only rapid-acting insulin, so any failure of the IIS can become a critical health issue. At best, IIS failure increases health care costs, while at the worst it can lead to elevated HbA1c levels, diabetic ketoacidosis (DKA), or death. Even though IIS designs have improved and fewer adverse events occur today, pump plumbing (IIS) continues to retain many similarities to home plumbing in the era of galvanized pipes fraught with a variety of ways to fail. When an IIS issue of unexplained hyperglycemia or occlusion arises, several factors may be involved, including the physical design of the IIS, material composition of the catheter, tendency for dislodgement, presence or absence of a safety anchor or anchoring tape, type of insulin, strength of the adhesive used to fix the set to the skin, and the lubricant used to coat the exterior of a Teflon or steel cannula. Any of these may impact glucose outcomes, duration of use, and comfort. Variations in the manufacturing process over time can also impact IIS reliability. Small changes or adjustments in IIS materials or the manufacturing process will sometimes have a considerable impact on IIS properties in daily life. For example, the thickness of the Teflon wall of a cannula is directly related to its risk of kinking during insertion, while its comfort is inversely related to a lesser degree. Fixation of IIS systems to the skin with adhesive also has a major impact on glucose outcomes, yet this remains a relatively ignored area for clinical research. IIS reliability seems to vary by user and set. In pump blogs and in clinic and support group discussions, many users report that they have experienced acute metabolic deteriorations with one IIS or another that vanish once they switch to a different one, particularly when switching from a Teflon IIS to steel. Although anecdotal reports have to be taken with care, the number and consistency of these reports suggest that the type of IIS an individual chooses has a real impact on glucose control.