Smart Pumps

Mary Kay Weber, RN,CDE

Gay Williams, RN, BSN,CDE

                Continuous subcutaneous insulin infusion (CSII) pumps have been researched and available to people with diabetes for approximately 25 years. With time they have continued to get smaller in size, become compatible with commercial insulin preparations, have longer battery life, and have become easier to use. By easier to use we mean they are menu-driven, which eliminates the need to memorize complex button pushes. The introduction of the *quick release* infusion set technology in the early 1990s, combined with all of the above, has made prescribing pump therapy a viable and safe therapy for patients with type 1 diabetes. Quick release technology allows users to disconnect from the infusion tubing for showering, swimming, sexual intimacy, or as desired.  CSII more closely mimics a healthy pancreas.  It combines a continuous background level of insulin (basal) with bolus insulin taken before a meal and/or to correct for hyperglycemia.   In older or more basic pumps, the basal rate can be set in increments of 0.1 units per hour, and boluses can be given in the same increments.  With newer “smart” pumps, we can set the basal rate as low as 0.025 U/hr.

                With the introduction of the smart pumps, available from three pump manufacturers, the pump becomes a more sophisticated computer.  They now have the capability to store information on blood glucose (BG) levels and insulin doses given, as well as calculate the dose for the individual patient based on parameters entered by the patient and/or health care provider. Beyond just a simple calculator, the pumps “advise” the patient on insulin dose to prevent overcorrection based on previous boluses. The pump is always “trying” to get the patient to a set target BG range.

                 Pump set-up:

Smart pumps allow the patient and the health care provider to enter information specific to the patient. 

  • Blood glucose target:  A normal target may be 100 mg/dL. A person with hypoglycemia unawareness may have the target set at 120 mg/dL, while during pregnancy, the target may be set at 80 mg/dL.  The pumps will recommend a bolus to correct the person to the target number, or if a range is entered, to the highest number of the range if BG is above that number.  If the BG is below the target range and the person is entering a meal bolus, the pump will subtract insulin from the recommended food bolus to correct the BG up to the lowest number of a target.
  • Insulin to carb ratio is entered for the number of grams of carbohydrate covered by each unit of insulin.  This may vary by meal or time of day, and different ratios can be set in the pump for different meals or time periods.
  • Sensitivity factor allows the pump to calculate a correction bolus based on the person*s sensitivity to insulin. The pumps can recommend fractions of a unit for correction.
  • Food is usually entered by grams of carbohydrate, but may be done by exchanges or by personal food favorites entered into the pump.
  • Current BG may be entered from any meter, but two of the “smart” pumps have meters that can be programmed to communicate directly with the pump.  This communication may be infrared or by radio frequency.
  • Active insulin on board:  the pumps “remember” previous boluses, and have either a standard or programmable time for the duration of action of insulin for the pump user.  If programmable, this action may be set for 2-8 hours. Using this, the pump will decrease the amount of insulin recommended to correct a high BG during this action time, so that the risk of overcorrecting or stacking of insulin is decreased.
  • Various alerts or reminders can be entered into the smart pumps: A reminder to test after a bolus, a missed bolus alert, and a site change reminder are examples of these.

                The "smart" pumps allow insulin dose changes in smaller fractions of a unit.  For example, instead of a basal rate of 0.8 units per hour, the patient may fine-tune with 0.85 in any of these pumps, or even 0.825 units per hour in one pump.  Basal rates may change at 30-minute intervals, instead of hourly in the more basic pumps.

                With all of the features and the calculations on the “smart” pumps, the pump user still has control of boluses.  The dosage recommendation of the pump is simply a recommendation until the person activates the delivery of that bolus.  The user can back out of the feature without delivering the bolus. These pumps are ideal for the person who is carb counting.  A person using standard boluses and not carb counting may choose to use this pump without using all features, or can choose one of the basic pumps on the market.

                CSII is now being used for many patients with diabetes, not just type 1 diabetes.  We can use pump therapy with anyone who requires insulin.  This includes children or adults with type 1 diabetes, those with type 2 diabetes who require insulin, and gestational diabetes.  The new “smart” pumps can result in improved blood glucose control for our patients.  They can reduce math errors by doing the math for them and can decrease the number of correction boluses required.  Using a bolus estimator has been shown to reduce the need for post-meal correction boluses.  Probably the greatest benefit would be the patient’s inability to overcorrect for post-prandial elevations.  By measuring remaining unused or active insulin, the pump can prevent stacking of boluses, leading to hypoglycemia. 

                With the introduction of “smart” pumps, we meet new and different educational challenges.  The initiation of pump therapy takes more time.  There is more to teach the patient.  They must feel comfortable and possess knowledge about carbohydrate counting, and they must know their correction factor and their blood glucose target. These may not be terms that are familiar to some patients. With instruction and practice, pump therapy and using the new “smart” pumps can be mastered.

Mary Kay Weber and Gay Williams are diabetes nurse educators at St. Joseph's  Specialty Center for Diabetes