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Updated February 08, 2006

Go Ahead, Pick Your Pump
Which Pump Is Right for You?

by Gary Scheiner, M.S., C.D.E.

Ask the following questions when making your insulin pump selection:

Will the pump hold enough insulin to last you at least three days?
Some pumps hold as little as 176 units of insulin, while others hold as much as 300 units. Since most pump users change their infusion set every three days, it is important to have enough insulin in the reservoir to last that long. To estimate your three-day insulin requirements, take the total daily insulin you take now by injection (including short-acting and long-acting), and multiply by three. Presently, the Medtronic pumps hold either 176 or 300 units (depending on the model), the Animas and OmniPod each hold 200 units (although the OmniPod has no tubing to prime, thus saving 10–20 units), and the Deltec holds 300.

Can you see the screen reasonably well?
Unless you have somebody who can help you perform all of your daily pump programming, it is important that you be able to read the pump’s screen clearly. Check the screen contrast and the size of the characters, with and without the backlight, to make sure you can see them well enough to perform all necessary programming. Presently, only the Animas pump allows the user to alter the screen contrast.

Will the bolus dose amounts work for you?
If you require very large or very small mealtime doses, be careful. Presently, the maximum bolus on the Medtronic pumps is 25 units, on OmniPod, it’s 30 units, on Animas, it’s 35 units, and on Deltec, it’s 75 units. If you are extremely sensitive to insulin, look for a pump that delivers boluses in extremely small increments (less than a tenth of a unit). The Animas, Deltec, and OmniPod pumps all permit bolusing to the nearest 20th of a unit.

Will the “bolus calculator” meet your needs?
One of the best features of modern pumps is the built-in bolus calculator. All of the pumps ask for your blood glucose level and the grams of carbohydrate you plan to eat in determining your dose. They then deduct insulin that is still “active” or “unused” from the last bolus given. When setting up the bolus calculator, some pumps allow you to enter your insulin-to-carbohydrate ratio in very precise proportions (the Deltec Cozmo is great for doing this), while others round to whole numbers such as 1 unit of insulin per 4 grams of carbohydrate, 1 unit per 6 grams of carbohydrate, and so on. Some will not allow a ratio of less than 1 unit per 2 grams of carbohydrate (Animas) or 3 grams of carbohydrate (Medtronic). While this is not a problem for the majority of pump users, it can be limiting for people who are on very large doses of insulin.

Likewise, the time intervals used when setting insulin-to-carbohydrate ratios are highly flexible in some pumps and less flexible in others. The Deltec Cozmo offers the most flexibility in that you can select insulin-to-carbohydrate ratios by the name of the meal rather than by the time of day. It also allows different insulin-to-carbohydrate ratios for active versus nonactive situations. The Medtronic and OmniPod pumps allow you to set up different insulin-to-carbohydrate ratios at time intervals that you choose, such as 5:30 AM to 11 AM for breakfast, 11 AM to 2:30 PM for lunch, etc. The Animas pump offers much less flexibility: The time intervals for insulin-to-carbohydrate ratios, as well as target blood glucose levels and insulin sensitivity (for setting up “correction boluses,” or insulin delivered to bring down high blood glucose levels) are preset in six-, four-, or two-hour time blocks.

When making adjustments for “active” or “unused” insulin, different pumps handle the data in different ways. Deltec has the most conservative approach, deducting all unused insulin from the bolus calculation. Medtronic and Animas are somewhat less conservative, only deducting unused insulin from food boluses and correction boluses. OmniPod only considers correction boluses when figuring the unused insulin (unused insulin given for food is not counted), and therefore may underestimate unused insulin—and overestimate bolus doses.

Also in this article:
Online Pump Reviews
Pump Manufacturers

Gary Scheiner is a diabetes educator with a private practice (Integrated Diabetes Services) near Philadelphia, and the author of Think Like A Pancreas: A Practical Guide to Managing Diabetes With Insulin. He has had Type 1 diabetes for 20 years, and he and his staff of Certified Diabetes Educators offer diabetes education and management consultations via phone, fax, and Internet to people throughout the world. Please direct inquiries to Gary at his Web site, www.integrateddiabetes.com, via e-mail at gary@integrateddiabetes.com, or by phone at (877) 735-3648.

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