The Insulin Pump
An insulin pump consists of a reservoir (essentially, a large syringe) containing rapid-acting insulin, a battery-powered pump, and a computer chip controller. The pump delivers insulin via an infusion set (catheter tubing and a needle or soft cannula).
The pump closely mimics a healthy pancreas. It delivers rapid-acting insulin as a continuous infusion of small amounts (the basal dose) and can be programmed to release a bolus of additional insulin to compensate for carbohydrates consumed during meals or for high blood glucose levels. Patients can choose to receive a bolus of rapid-acting insulin before, during, or after the meal; other options include the square-wave bolus (a bolus released evenly over a set period of time, usually 30 minutes to two hours).
Because the pump allows for more efficient insulin absorption, most people need 25% less insulin when using the pump than when using injections.
1 Whoever prescribes the insulin pump should calculate the patient's initial dosage. Typically, 50% of the initial dosage is delivered at the basal rate and 50% is reserved for boluses. But patients must also learn how to verify the accuracy of their basal and bolus doses through frequent blood glucose monitoring and meticulous record keeping. For a beginning pump user, the basal rate can be calculated according to either body weight or total combined daily dosage of longer- and shorter-acting insulins given via injections.
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