Continuous Subcutaneous Insulin Infusion (CSII), commonly known as insulin pump therapy, is a medical technology that helps manage blood sugar levels by delivering insulin beneath the skin twenty-four hours a day. This delivery system closely mimics the function of a healthy pancreas, providing both a steady background supply and extra doses for meals or corrections. The effectiveness of this advanced delivery method relies entirely on using a specific type of insulin formulated for continuous, precise dosing.
The Essential Insulin Type for Pump Delivery
Insulin pumps are designed to be used exclusively with rapid-acting insulin analogs. This category of insulin is chemically modified to start working very quickly after administration, providing the necessary immediate effect for meal coverage and blood sugar corrections. Rapid-acting insulins typically have an onset of action within 5 to 15 minutes of delivery. Their glucose-lowering effect usually reaches its peak activity within 45 to 90 minutes, and the overall duration of action is relatively short, lasting about three to five hours. This quick onset and limited duration are what make them suitable for the continuous, flexible delivery required by the pump.
Why Rapid-Acting Insulin is Necessary for Pumps
The design of the insulin pump aims to simulate the body’s natural insulin release, which requires two distinct delivery patterns: basal and bolus. Rapid-acting insulin’s unique profile is ideally suited to fulfill both roles with precision. The pump provides a continuous basal rate by administering minute micro-doses of rapid-acting insulin every few minutes.
The short duration of action is important here because it prevents the stacking of insulin, which could otherwise lead to prolonged periods of low blood sugar, or hypoglycemia. If the basal rate needs to be temporarily suspended or reduced, the insulin already delivered clears the system quickly, allowing for prompt adjustment to changing needs, such as during exercise. The pump’s ability to dynamically increase or decrease the basal rate at different times of the day to match the body’s varying requirements is completely dependent on this short half-life.
For meal coverage, known as a bolus dose, a rapid onset is crucial for managing the post-meal rise in blood glucose. Since the insulin starts working within minutes, the user can deliver the bolus dose just before or shortly after eating, offering significant flexibility in meal timing. This immediate action helps to prevent post-meal blood sugar spikes more effectively than older, slower-acting insulins.
Approved Insulin Formulations for Pump Use
Several specific rapid-acting insulin analogs are approved for use in continuous subcutaneous insulin infusion devices. The most common formulations include insulin lispro, insulin aspart, and insulin glulisine. Newer ultra-rapid formulations of these analogs are also available and are being increasingly used in pump therapy due to their even faster absorption rates.
The physical stability of the insulin inside the pump reservoir is a major consideration, as the constant movement and body temperature can cause degradation. Manufacturers typically recommend changing the infusion set and the reservoir containing the insulin every two to three days. This regular change is necessary to maintain the integrity of the insulin and to prevent the infusion set from becoming blocked, or occluded, which would stop insulin delivery.
Specific formulations have different guidelines regarding how long they can safely remain in the reservoir. For instance, insulin lispro and insulin aspart are generally approved for up to 144 hours of pump use, but insulin glulisine often requires replacement every 48 hours due to a higher risk of crystallization. When filling the pump’s reservoir, it is important to carefully prime the tubing and tap the cartridge to remove any air bubbles, as air in the line can interfere with accurate insulin delivery and cause alarms. Avoiding exposure to extreme temperatures is also important, as this can accelerate the breakdown of the insulin analog.