two or three days. The whole reservoir is screw-turned tightly into the chamber in the pump, and the tubing leads away to the infusion set, which is attached to the body. With a patch pump, the reservoir is contained within the pod, which adheres to the skin.
Screen
The pump has a front screen (the patch pump has the screen on the controller). When not in use, front screens generally display the time (some have the date), insulin remaining, and information about battery life. By pushing different buttons on the face of the pump, you can access different functions in the pump’s software. The software lets you deliver insulin; set or edit basal rates; set or edit the pump calculator; suspend insulin delivery; review your bolus, basal, and alarm histories; and see the exact amount of insulin remaining in the reservoir.
Software
The software not only lets you know the date and time, it also allows your pump to store tons of information, including weeks’ or months’ worth of bolus and alarm histories, blood glucose readings, and basal rates. The software allows the pump to consistently deliver the correct amount of basal insulin. It can also calculate the appropriate amount of insulin needed based on a glucose reading and a carb count entered into the system. Some pumps have a large database of food and carb counts. There are also safety features that prevent the user from providing too much or too little insulin in boluses or for the basal rate. Software also allows you to determine how you want to deliver a bolus every time you deliver one.
Pump History and Downloading
The information stored in the pump can be uploaded to a computer and analyzed by software. Generally the pump connects to the computer using a cable or wireless connection, and once the information is transferred from the pump to a computer, the user can look at graphs, pie charts, lists, and other visual information. Many diabetes care providers download information from the pump during clinic visits, or they may ask you to download it at home and bring a printed copy to your appointment. Between visits, you should look at this information and send it to your diabetes team if you need help troubleshooting some problems.
Blood and Interstitial Glucose Monitoring
Most pumps can connect to a blood glucose meter. In addition, it is possible for some of them to connect wirelessly to a continuous glucose monitor (CGM). This means that the glucose meter and sensor can transmit glucose values directly to the pump’s screen and memory.
Insulin Delivery
Pumps deliver basal and bolus rates of insulin. Basal rates are set by the user, with guidance from the diabetes team. Based on individual dosing, mealtime and correction boluses are given.
Suspend
All pumps have the ability to be suspended so that no insulin (basal or bolus) can be administered. A pump can remain suspended indefinitely but will sound an alarm every so often to remind you that you are not receiving insulin. With most pumps, it is easy to suspend insulin delivery in case you have an emergency.
Alarms
Pumps have alarms. Some are functionally important, such as “low battery” or “no delivery” (called an “occlusion” alarm in some pumps). There are alarms that you can set to remind you to test, take insulin, or check for ketones if your glucose is over a certain amount. If you need to, you can review the last 50 or so alarms. Pumps have different options for the way they notify you, such as various beeps or sounds or with vibration. Most pumps will beep or vibrate when a bolus is complete, when you are currently using a temporary basal rate, or when you have a low reservoir or low battery.
Active Insulin or Insulin on Board
After a bolus is given, insulin continues to affect your glucose level for some time. The amount of insulin left in your bloodstream is referred to as “active insulin” or “insulin on board.” You can set how long you want the pump to track active insulin, but discuss with your health care team how long you should have the pump track it. Generally, people set the active insulin time to two to five hours (most often, three). The pump calculator keeps track of the amount of insulin that is still active from previous boluses so you do not have boluses overlapping each other and dropping your glucose levels (this is referred to as “insulin stacking”).
Maximal Bolus and Basal Rates
You set a maximal rate for both basal and bolus insulin delivery to enhance safety. This prohibits you from accidently taking 20.0 units instead of 2.0, for example.
Pump Bolus Calculators Make Pumps Smart
The pump bolus calculator—which makes pumps smart—calculates how much insulin to give for boluses. It takes into account your insulin-to-carbohydrate ratio (ICR), the insulin sensitivity factor (ISF), the duration of active insulin, and your target glucose range. These values (except active insulin) can be altered by time of day, for example, because your insulin sensitivity and your ICR change over the course of 24 hours. When you first get your pump, your diabetes care team will help you determine these settings. They can be changed at any time (preferably in consultation with your diabetes team) as indicated by the patterns in your glucose control.
To determine the amount of insulin you take for a food bolus, you enter the number of grams of carbohydrate you plan to ingest and your current blood glucose level. Then the pump calculator will determine how much insulin you should take. If your blood glucose is above or below your target range, the bolus calculator will also figure out if you need to add or subtract insulin from the food dose.
However, you can always alter the insulin bolus dose suggested by the pump bolus calculator, giving yourself less or more insulin depending on any number of factors. If you are about to exercise or are not sure you will eat an entire meal, you might want to decrease your bolus from what the calculator suggests. If you have ketones or are sick, you might want to take more. Although it is convenient to have the pump calculator so you don’t have to do the calculations yourself, it is important to think before you push the button.
Here’s an example. If your blood glucose is 250 mg/dL and you are about to eat 15 grams of carbohydrate for lunch, you would enter those numbers into your bolus calculator (or the blood glucose would be automatically sent from your meter). The calculator suggests an amount of insulin to bring your glucose into your target range and cover your meal. Some pumps will show you the two different amounts, one for food and one for correction, and others will simply lump them together into one suggested bolus without showing a breakdown.
Keeping detailed records of your blood glucose levels, doses of insulin, food intake, and other events (such as exercise, illness, or stress) is important. It is also hard to keep a logbook or a record of all that you do every day. However, when this information is available for review, you are able to spot patterns and trends that may be problematic. In contrast, if you are looking only at your current glucose level, you won’t detect these patterns, even if you correct your high glucose nearly every morning and treat a low every afternoon.
By uploading data from your pump to the software, especially when it also includes information from your glucose meter (and a CGM, if you have one), you are able to review up to three months of data. Because the bolus calculator captures the carbohydrate history for meals and breaks out the bolus details so you can see when correction doses were administered, you have the ability to look for trends and patterns. By reviewing these data, you can identify what the problems are, why they are occurring, and how they can be fixed.
A Diabetes Meeting
The purpose of a diabetes meeting is to sit down with your diabetes team and review your glucose trends and patterns, your pump (and CGM) settings, and how you are doing with your diabetes regimen. The frequency should be weekly, or less often if there are no issues with your diabetes. The purpose of a diabetes meeting is to identify patterns and trends in your glucose levels, alterations that need to be made in your pump (and CGM) settings, or behaviors