A pump offers convenience, more consistent insulin action from day to day, easier problem solving, easier tracking of insulin use, less hypoglycemia, less risk of hypoglycemia unawareness, and fewer morning and post-meal highs. These conveniences come from specific features that are standard in most pumps. Training is required to benefit from all the pump features listed below. Read your pump manual carefully, work with your health care professionals, and talk with other pumpers for the best results.
A built-in bolus calculator (BC) uses personalized settings to make bolus doses more accurate and less likely to cause insulin stacking from prior boluses. The pump bolus calculator (BC) allows bolus recommendations to match the carbs you eat, bring down high readings, and minimize insulin stacking.
Basal rates from a pump replace the long-acting insulin doses taken by those on injections. This provides an around-the-clock delivery of insulin that stops the liver from making and releasing excess glucose into the bloodstream. Most pumps can change basal delivery every 1 to 30 minutes in increments as small as 0.01 to 0.025 unit per hour.
Boluses are short spurts of insulin given to cover the carbs in meals and snacks and to lower any high readings that may occur. Unlike basal rates, boluses are not programmed ahead of time but are given in the appropriate amount when they are needed. Once a pump BC is programmed with a carb factor and a correction factor by the user and health care provider, the user simply enters how many carbs they plan to eat and their current glucose. The bolus recommendation from the BC can always be adjusted by the wearer as needed for exercise, illness, or stress.
A glucose correction target or target range is the target that you want your glucose brought down to. It can be entered into the pump BC as a single target for the entire day, or as a different target for each meal and at bedtime.
Your correction target differs from the wider glucose goal range in which you would like your glucose to stay. Your correction target is used by your pump BC to calculate the bolus dose you need to reach this glucose 4 to 5 hours later. For example, if a reading of 140 mg/dL (7.8 mmol) is desired near bedtime at 10 pm, this target would be set in the pump by 5 pm to allow time for the pump to achieve this goal. If you select a wide range for your correction target, your pump BC’s aim becomes less precise. A single correction target like 110 mg/dl (6.1 mmol/L) or a narrow range is preferred.
The DIA or duration of insulin action is how long a bolus lowers the glucose. An accurate DIA must be entered in the pump to prevent insulin stacking when boluses are given close together. Stacking can occur any time a previous carb and correction bolus is still lowering your glucose when a new bolus is given. An accurate DIA time allows the BC to properly calculate subsequent carb and correction boluses once the first bolus of the day has been given.
Frequent boluses are easy to give on a pump, but this can also lead to insulin stacking of BOB. BOB is the insulin that remains active from one or more recent boluses. When a carb bolus is given for dinner, another for an unplanned dessert, and then a correction bolus is needed for the high reading that follows, the resulting insulin pileup can make it difficult to determine the amount of bolus insulin remaining in the body at bedtime. This is critical when deciding whether you need more insulin to cover a high reading, or whether you need to eat carbs to prevent your glucose from going low.
When a high glucose reading is entered into the pump before giving a correction bolus, pump BCs take into account the current BOB (insulin on board or active insulin) to prevent insulin stacking. This is especially helpful for those who live alone, those who have hypoglycemia unawareness, and those with a history of frequent lows.
Basal/Bolus Balance and Correction-Bolus Tracking
Basal and bolus doses have to be balanced for optimum control. The pump wearer’s basal/bolus balance can be calculated manually from the average insulin doses given over several days or may be calculated by the pump itself and shown in a history screen. This lets you see how your insulin is used and can help spot causes for any problems that may arise. For adults with Type 1 diabetes, glucose control is usually best when basal insulin delivery makes up 40% to 65% of the TDD. If control problems occur, the pump’s memory can be quickly checked to determine the percentage of the TDD currently used for basal rates, carb boluses, and correction boluses. Many diabetes clinicians check basal/bolus balance at each clinic visit because it gives helpful insight for improving control.
Some pumps track correction bolus doses to determine how much correction bolus insulin has been used over the last 2 to 30 days to bring down high readings. Correction boluses usually make up less than 9% of the TDD. If more than 9% of the TDD is used to bring down high readings, the basal rates or carb bolus doses need to be increased.
Many pumps have an associated meter that sends glucose readings directly into the pump for convenience and helps the pump calculate an accurate correction bolus to prevent insulin stacking. Direct entry ensures accurate data entry, reduces human error, speeds bolus calculations, and guarantees that every glucose reading is used by the BC to suggest appropriate boluses after accounting for BOB. If your meter does not automatically enter readings into your pump or yiou use more than one meter, be sure to enter a test each time it is taken. Only when you enter your glucose into your pump will it account for BOB in its bolus recommendations.
Reminders and alerts on pumps can be customized for safety and to improve control. For instance, a postmeal reminder can be set to recheck your blood glucose 1.5 or 2 hours after a bolus has been given. Post-meal testing lets you evaluate the meal bolus. You may need extra carbs to prevent a low or a correction bolus because the meal bolus was too small. Post-meal testing helps prevent lows and speeds correction of highs.