An insulin pump is a small battery-powered device, worn on the body, that delivers insulin under the skin through the day and night. People with type 1 diabetes use it most. Their bodies make no insulin, the hormone that moves sugar from the blood into the body's cells. Without a pump, they inject insulin several times a day with a pen or a syringe.
The pump is about the size of a mobile phone, or smaller. It holds a reservoir of insulin. A thin tube, called an infusion set, leads from the pump to a cannula, a tiny soft plastic tube that sits just under the skin of the belly or the arm. The user changes the infusion set every two or three days. Some pumps have no tube and stick straight onto the skin. They are called patch pumps. A pump is worn, not implanted. It is grouped with implants here because it is built and regulated in a similar way.
The pump gives insulin in two ways. A basal dose is a small, steady amount through the day, such as 0.8 units an hour. A bolus is a larger dose at a meal. The user enters the amount of carbohydrate in the meal, and the pump's software suggests the bolus.
Many pumps now take readings from a continuous glucose monitor (CGM), a sensor on the skin that measures blood sugar every five minutes. Software in the pump then adjusts the basal dose by itself. This is called automated insulin delivery, or a hybrid closed loop. "Hybrid" means that the user still has to enter each meal.
Say a 14-year-old schoolboy in Lucknow uses such a pump. After lunch, his blood sugar rises to 210 mg/dL. Every five minutes, the pump reads the CGM and adds a little extra insulin. At 3 a.m., his sugar falls towards 75 mg/dL, and the pump pauses the basal dose for an hour without waking him. The pump records every dose. His parents and his doctor can see the records in an app. Digital diabetes management software can show patterns in them over weeks.
The dosing decisions are made by firmware inside the pump. A wrong dose can cause harm, so the dosing algorithm is regulated as part of the device, as explained in software as a medical device. Every change is tested before it is released. The pump also has alarms for a blocked tube, an empty reservoir and a low battery.
In India, insulin pumps are used by a fairly small number of people, mostly with type 1 diabetes. A pump and a year of its supplies cost lakhs of rupees, which most families pay themselves. Watching a patient's readings from a distance in this way is a form of remote patient monitoring.