Best Ways and Practices to Avoid Insulin Pump Catheter Occlusions

Over the past decade, significant strides have been made in the technology of insulin delivery and glucose monitoring. Insulin pump use has become standard of care, and the development and improvement of continuous glucose monitoring have not only helped to reduce severe hypoglycemia, but have also placed us firmly on the path to development of closed-loop (artificial pancreas) management of diabetes.

Despite the widespread use of continuous subcutaneous insulin infusion (CSII), there has been relatively little improvement in insulin infusion sets. They have been described recently as the Achilles heel of CSII. ¹ In fact, a recent joint statement issued by the American Diabetes Association and the European Association for the Study of Diabetes stresses the small number of publications around the use of set occlusions and failures, ² especially when compared with the high number of adverse events reported to the Food and Drug Administration in the United States.

The role of the insulin infusion set is reliable transfer of pumped insulin to a subcutaneous insulin depot. Accurate, uninterrupted delivery can be affected by site placement, duration of use, interstitial pressure, occlusion by cellular debris or insulin, and the material of which the infusion set is made.

In order to evaluate the difference in occlusion rate by insulin analogs, in vitro testing of the three commonly available rapid-acting insulin analogs was performed, ³ studying flow rates and pressures over a 5-day period. There were no differences between analogs in the first 48 h at either low or high (bolus) delivery rates. By Day 5, however, there were occlusions that varied with the analog used, with insulin glulisine having the highest rate (40.9%) and insulin aspart the lowest (9.2%). Because use of an infusion set for over 3 days is longer than the recommended duration, the authors concluded that early occlusions are uncommon and independent of insulin type and that sets should be changed at least every 72 h. Furthermore, a randomized trial of insulin infusion set function comparing steel with Teflon^® (Dupont, Wilmington, DE) catheters failed to demonstrate a difference in occlusion rate. ⁴ However, 15% of the Teflon sets failed because of kinking during insertion. It has also been demonstrated that median tissue resistance pressure increased significantly with higher infusion rates, and it was suggested that occlusion detection might be better measured using rate-dependent detection thresholds. ⁵

There is a growing awareness that infusion set failure may result in silent occlusions, especially with low flow volumes such as are used in small children, because CSII uses in-line pressure to determine flow and to trigger occlusion alarms. Such silent occlusions can lead to deterioration in glucose control and to delays in recognition of insulin delivery failure, causing the development of hyperglycemia and ketosis or diabetic ketoacidosis.

The research group from Becton Dickinson presents in this issue of the journal a new infusion catheter that adds a side port to the traditional end port. ⁶ This innovation, presented last year in abstract form at the Advanced Technology and Treatments for Diabetes ⁷ and the American Diabetes Association ⁸ scientific sessions, shows real promise in reducing silent occlusions by 74–79%, with no difference in leakage or alarms when compared with currently available infusion sets. Unfortunately, the studies were only short term, and long-term home studies need to be performed before strong conclusions can be made regarding the longer use of these infusion sets.

This is a welcome technologic advance, attending as it does to this weakest link in the CSII chain. More work needs to be done in redefining occlusion alarm sensitivity, studying interstitial pressures related to site and duration of use, and creating catheters less likely to fail at insertion or to kink over time.