Insulin Pump Basics

This month’s column is for anybody interested in understanding the terms used with insulin pump therapy. Clip and save this for your reference.

Basal insulin delivery/basal rate. The amount of insulin needed to meet metabolic needs and maintain blood glucose levels between meals and during the night. Using only short-acting or rapid-acting insulin, basal delivery rates in insulin pumps can be programmed to automatically change at predetermined time frames to meet varying basal insulin requirements. Delivery rates typically range from 0.025 to 2 units per hour, but can vary among individuals. Basal insulin delivery ranges from 40 to 60 percent of the total daily insulin.

Bolus insulin delivery. Insulin doses calculated for meals, snacks and to correct for elevated glucose levels. Bolus insulin doses account for the remaining total daily insulin percentage.

Basal program. A function of each individual pump, programmed by the user with the help of the diabetes care team, to deliver a specific amount of insulin at specific time frames within a 24-hour period. For example:

Time frame Units per hour

midnight to 3 a.m. 0.35 units

3 a.m. to 9 a.m. 0.7 units

9 a.m. to 2 p.m. 0.4 units

2 p.m. to midnight 0.6 units

Several pumps offer the option of setting more than one basal program, that is, one for normal daily activities, one for weekends and others for exercise, menstrual cycles or illness.

Correction factor (CF). Your correction factor is how many points (mg/dl) your blood glucose generally drops per each unit of short-acting or rapid-acting insulin.

Insulin to carbohydrate ratio. Based on the concept of carbohydrate counting, these are individual calculations to assist in programming the amount of insulin bolus required to cover carbohydrate intake.

Total daily dose (TDD). An total of all injected insulins within a 24-hour time frame. Starting basal insulin rates are based on the total daily insulin intake.

Square wave/extended bolus. A dose programmed to deliver over a specified amount of time, usually 30 minutes to one or more hours. Typically, this bolus method is used for high-fat or high-protein meals or for delayed digestion (gastroparesis).

Dual wave/combination bolus. A method used to deliver a portion of the insulin bolus immediately, at the start of a meal; the remaining bolus insulin dose is programmed to deliver over time. According to some endocrinologists, this is an effective bolus method because it simulates the first- and second-phase insulin release that normally occurs.

Infusion set. A transparent, flexible tubing of various lengths attached to the pump syringe at one end and an insertion catheter, or needle, at the opposite end. An insertion needle may be fused to the end of the tubing or have a connector for a separate flexible insertion catheter placed under the skin. The base of the set is waterproofed cotton or plastic material with an adhesive side that is affixed to the skin. A few sets have separate tape applications. Infusion sets and catheters/needles are available in different lengths to suit your needs.

Infusion site. A location for placement of the infusion set. While the abdomen is a frequently used site, insulin pump infusion may use any location where you could inject manually. It is recommended to change infusion sets and sites every two to three days to avoid site-related infections or insulin absorption problems.

Cartridge/reservoir/syringe. Interchangeable names (chosen by a manufacturer) for the insulin container placed inside the pump. These items are pump-brand specific. You would not use one pump manufacturer’s syringe in another manufacturer’s pump.

Temporary basal rate. A programmable rate to raise or lower basal delivery from 30 minutes to several hours. This is useful for situations of increased or decreased activity and in cases of illness or stress.

Suspend/stop function. Another manufacturer-specific term for halting insulin delivery. Used when refilling cartridges, changing infusion sets or replacing batteries. The use of this function should be reviewed by the pump trainer. Details on safe use should be located in the product manual supplied by the specific manufacturer.

Dawn phenomenon. A rise in insulin requirements occurring in the early morning hours, influenced by rising levels of other insulin-resistant hormones (growth hormone, cortisol, glucagon, adrenaline), often doubling the morning basal insulin need.

Reverse dawn phenomenon. May be seen in children younger than 12 years of age where the blood glucose is higher from late evening to early morning hours (9 pm to 3 am) and lower from early morning hours to early evening (3 am to 6 pm).

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