Optimizing Duration of Usage of Insulin Infusion Sets: A Response

Walsh and Heinemann’s editorial, “Optimizing Duration of Usage of Insulin Infusion Sets: Impact of Mechanical Stress on Infusion Sites and Identifying Individuals with IIS Issues,” raised several insightful points regarding insulin infusion set (IIS) performance. ¹ Undoubtedly, while motion-related stresses may cause IIS failure, designing IISs is deceptively complex, requiring deep expertise in biomechanics, immunology, material science, and an understanding of the wide range of end-user variability that factor into consistent insulin delivery. Addressing these challenges through the seven-day Extended Infusion Set (EIS), Medtronic journeyed to the River Styx and jumped right in—feet first.

Walsh and Heinemann noted that IISs with steel cannulas employ a second adhesive to minimize mechanical stress at the infusion site, thereby decreasing inflammation. ¹ In addition, post-insertion inflammation may also be caused by the immune response to insulin aggregates, as evidenced by the decrease in inflammation-related failures experienced by users of the seven-day EIS that is specially designed to address this issue. ² Importantly, the EIS is subject to the same mechanically induced stresses (or greater, over the extended lifetime), yet the failures due to biological responses (including insertion injury) fell to 1.6%. ² Nevertheless, educating users to anchor the tubing (a so-called “safety loop”) may reduce the risk of cannula movement and dislodgment, potentially reducing irritation, inflammation, and the appearance of “pump bumps,” ³ notwithstanding user burden and potential skin reactions to the adhesive.

Motion-related considerations aside, Walsh and Heinemann also raised valuable questions, including whether the Quick-Set (QS) is the best comparator. Until the advent of the EIS, the QS had been the nominal comparator with its long history of use. Centered on improving user experience, the Mio Advance, cleared in 2018, features a built-in insertion device with automatic needle retraction to ensure consistent insertion depth while reducing insertion failure, injury, and inflammation. ² Building on these improvements, the EIS [510(k) K210544] further reduced user burden, in addition to insulin and plastic waste, with an extended wear duration ⁴ and should be considered the state-of-the-art comparator. Quantitative analyses are underway to establish benchmarks in real-world performance metrics including improved glycemic outcomes and occlusion rates as a function of wear duration, with preliminary results indicating that longer wears are associated with better glycemic control (especially on days after set insertion) and decreased user burden. ⁵

Admittedly, IIS technology is still not perfect. Adhesive failure, including motion-related effects, contributed to 6.2% of EIS failures. ² Stronger, albeit comfortable, adhesives designed for extended wear applications are needed to buttress reliable insulin delivery. In addition, developing novel, biocompatible cannula materials with a modulus matching the subcutaneous tissues may further reduce the risk of inducing mechanical stresses throughout the duration of wear. ⁶

Finally, agreeing with Walsh and Heinemann, the wide range of inter-individual variability in user experiences with the whole gamut of IISs necessitates studies on the effect of demographics (eg, age, gender, body mass index [BMI], epidermal thickness) as well as practices (eg, cannula fills) on IIS performance. The results will inform the IIS selection process and user education, ultimately yielding more equitable and personalized care for all pump users.