Bolus delivery
• What types of bolus delivery options does the pump have? Is the bolus delivery increment in twentieths, tenths, halves, or whole-unit increments, or does the user have a choice? Patients who are insulin sensitive may prefer or require fractional-unit bolus increments.
• Is there more than one type of bolus delivery available? An extended (“square wave”) or combination immediate/extended (“dual wave”) bolus delivery is useful for patients with gastroparesis and also may be used when consuming high-protein, high-fat, or ethnic meals and if using pramlintide. How long can delivery be extended? Can the delivery be in increments of an hour, such as 15, 30, or 45 minutes?
• Is there a touch bolus button? Is it audio or vibratory? This is a consideration for the patient who prefers to wear the pump discreetly and does not want to visibly press buttons on the pump or use a remote device to deliver a bolus.
• Is there a remote device available to deliver a bolus?
• Can specific bolus types be “named” and programmed into the pump for ease of use, such as “pizza,” “ethnic meal,” “dessert”? This is helpful and alleviates the need to repeatedly program a frequently used combination (“dual wave”) bolus.
• How is “insulin on board” (active insulin) calculated for bolus deliveries, i.e., can the user determine the number of hours the most recent bolus is active, or does the pump automatically default to a specific duration of time setting, such as 4 hours? This is a useful feature to prevent “insulin stacking” for repeated correction boluses (see Use of Duration of Insulin Action “Insulin on Board” or “Active Insulin” Feature). How does the insulin on board feature account for the insulin dose required for the upcoming meal?
• Does the pump store a history of bolus deliveries? How many? Can this information be downloaded to track trends and patterns of use and dosages?
Safety
• Can a bolus dose be stopped easily during delivery? Can the user track exactly how much of the bolus was delivered before it was halted?
• Is there a maximum use lockout feature for children, so that a basal rate or bolus delivery cannot be programmed for more than a specific upper limit?
• Is there a time-out feature that the user can pre-set to halt all insulin delivery if a button is not pushed for a specific duration of time?
• Can the user set an hourly limit of insulin delivery?
• What type of safety and performance checks does the pump have? How often does the pump perform self-checks?
• What types of warning and alarm systems does the pump have? Is there an alarm for undelivered basal insulin?
• Does the pump alarm sound/vibrate when insulin is running low or the cartridge/reservoir is empty? How is the amount indicated? Is it approximate or exact?
• If batteries are removed for an extended period of time, does the pump retain its memory of programmed basal rates and history of bolus doses and alarms?
• Is the warning and/or alarm signal visual, auditory, or tactile? If audio, how loud is it? Patients may need a pump with vibrating warnings and alarms.
• In case of a major technical problem, is a backup pump provided? What are the procedures to obtain a backup pump if one is not provided at the time of purchase? How quickly does the patient receive the replacement pump?
• What is the repair policy? If the pump is returned for problems, is it repaired and reissued to the patient, or is a new pump provided? Are refurbished pumps redistributed?
Infusion Set and Tubing Options
Infusion sets distributed by the various pump and pump supply manufacturers may be interchangeable to work with several different brands of pumps or they may be proprietary and brand-specific. Some sets may be designed specifically for a particular age group, such as pediatric. It is best to check with each pump company for specific availability and recommendations and make sure your patient explores all the options with the assistance of the pump manufacturer.
An infusion set is inserted subcutaneously and the set “base” is attached to the insertion site with self-adhesive dressing or tape. An infusion set is worn for 1–3 days and then removed and discarded. Infusion sets left in longer can lead to infection and/or scarring, which slows insulin delivery. Although many brands exist, there are basically two types of infusion sets: metal/steel needle cannula and Teflon cannula, and both types are available in various models. Most infusion sets connect to an insulin pump using a Luer-lock connection, and thus are universal and can be used with a variety of pumps. Advise the potential pumper to be aware of pumps that use a proprietary infusion set, as their choice of infusion sets will be limited unless the pump has an adapter that allows it to accept a Luer-lock infusion set (Roche 2012).
A metal/steel needle infusion set is inserted at a 45- to 90°-angle and requires that the needle stay under the skin. The insertion base and tubing are attached to the site with either self-adhesive or separate dressing or tape. A metal/steel needle infusion set can be disconnected from the infusion site (close to the site or several inches from the site), thus providing lifestyle comfort for physical activity, bathing, and sexual activity. A variety of needles are available by type (straight or bent) and length. Children and lean adults may need shorter needles, and active people may need longer needles to guarantee subcutaneous insertion and placement. A metal/steel needle set may be appropriate for patients who have problems with kinking or dislodgment of Teflon cannula sets. A metal/steel needle set is made of surgical stainless steel and can contain up to 12% nickel and may not be appropriate for people who experience an allergic reaction to nickel or stainless steel (Roche 2012). Some people find the metal/steel needle sets to be uncomfortable because the needle may “pinch” or be felt during physical activity or movement. A metal/steel needle set should be changed every 24 to 48 hours (Roche 2012). A major advantage of the metal/steel needle infusion set is the guarantee of insulin delivery, as a metal/steel needle cannot kink below the skin like a Teflon cannula set. Many parents of child pumpers like them because they are easy to teach to the child’s teacher or babysitter in case the child’s usual cannula set becomes dislodged. Metal/steel needle infusion sets are also often recommended during pregnancy because they may be easier than a Teflon cannula to insert in the abdominal area or a “hard to reach” (such as the upper hip/buttocal) area and they guarantee insulin delivery with no risk of a kinked or bent cannula.
The metal/steel needle infusion sets had been in use for several decades when pumps were first introduced. They are generally less costly than the soft Teflon cannula sets but are not as commonly used today. Some people choose to alternate use of both types of sets depending on their activity or exercise.
An allergic reaction to the adhesive in the dressing or the glue used to manufacture the infusion sets can occur; trial and error with different products is recommended to determine individual sensitivity.
Because every person can react differently to infusion set material, suggest your patient try a variety of sets. Pump manufacturers and trainers may be able to provide a sample of a few different sets for the patient to try.
A soft Teflon cannula set uses a stainless steel introducer needle that is threaded into the cannula for a 20- to 90°-angle subcutaneous insertion, depending on the brand and the angle of the needle (angled 30 to 45° versus straight 90°). Teflon cannula sets are latex-free and do not contain PVC (polyvinyl chloride). After insertion the needle is removed (having been under the skin just a few seconds), leaving only the cannula below the skin and the infusion set base at the site. The set base has self-adhesive tape or dressing. With a 30°- to 45°-angled set, there is a clear “window” area in the self-adhesive tape, allowing