Insulin pump
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-->An insulin pump is a device used for administering insulin in the treatment of diabetes mellitus.
The device consists principally of three parts :
- the pump itself including controls, processing module, and batteries
- delivery tube to carry the insulin
- needle or more commonly a catheter inserted into the body subcutaneously
- a basal (small) dose that is delivered constantly
- a bolus dose that is delivered before meals mostly for adults, after mostly for children, or to correct high blood glucose (also known as blood sugar) levels
-->Because a single type of insulin is used, it is easier to determine the effect of a given dose by looking at the delivery profile of that insulin. Insulin pumps also make it possible to deliver much smaller amounts of insulin than can be injected using a syringe, and to deliver boluses of insulin more frequently than is tenable via a syringe. This provides tighter control over blood sugar and Hemoglobin A1c levels, reducing the chance of long-term complications associated with diabetes.
Insulin pumps are used in tandem with a glucose meter (or "glucometer"), a separate device that determines an individual's blood sugar level via a small drop of blood, usually obtained via a lancet device on the fingertip, hand, arm, or other areas. The glucometer can be completely independent (in brand and technology) from the pump, or can be part of an integrated system, such as more recent versions of the Minimed Paradigm, which allows for radio frequency (RF) communication from the glucometer to the pump. The Cozmo Pump, made by Smith's Medical, works with the Cozmonitor, a device made by Freestyle, attached to the back of the pump. The pump receives glucose readings from this attached meter via infrared (IR). This saves the user the trouble of inputing blood glucose readings into the pump, and aides in the ease of determining the size of a bolus.
The amount of insulin delivered for a bolus is determined by the blood sugar level and the grams of carbohydrates consumed. In all cases, delivery rates are determined by the user in consultation with his endocrinologist. Currently there is no means to automatically control the insulin delivery based on the blood glucose level of the user. However, several manufacturers of pumps, including Medtronic (Paradigm, Minimed), and Roche Diagnostics (Disetronic H-Tron and D-Tron) are testing the concept of a closed-loop system but even if the concept is as promising as it appears there remains the legal problem of what happens if the system is incorrect. For example, continuous blood glucose monitoring (CBGM) technology can report very wide variances of blood glucose. Using the non-US measuring system of mmol/l (multiply by 18 to get mg/dL glucose readings used in U.S)a closed-system that detects glucose of say, 15 mmol/l (270mg/dL) might dispense 10u of fast acting insulin. If the patient has an actual glucose of 6 mmol/l (108 mg/dL) (within the accepted glycaemic range), those 10 units of insulin could very quickly lead to hypoglycaemic coma which if not recognised and treated can kill very quickly. There is a lot more research to do on CBGM technology but the first closed-loop systems may be made available for clinical trials by mid-2006.
Use of insulin pumps is increasing as it provides an easier means to deliver multiple insulin injections for those using intensive insulin therapy. It's also interesting to note that because of differences in health insurance and public funding, the US has about 150,000 pump users. In the UK, NICE have now ruled that if a diabetic patient's doctor agrees that they should be using an insulin pump, they should apply to the NHS and they will fund it. Therefore numbers are increasing but are still less than the USA, there are around 1100 pump users in the UK by comparison.
"Closed loop" insulin pumps--whereby a continuous glucose monitoring system (essentially an implanted glucometer) works in tandem with the insulin pump to constantly monitor, dose, and control blood sugar levels--are currently in the testing phase, and are not in wide distribution. However, some manufacturers are introducing new devices that more fully integrate glucometers and pumps, such as the Minimed Paradigm Real-Time pump, which comprises a glucometer that measures interstitial blood sugar that communicates via RF with the pump to provide a constant (updated every five minutes) real-time readout of blood sugar levels. This is a significant advance over the separate-device approach, in which users test blood sugar on average only four to six times a day. Minimed recommends, however, that users still compare the results of the Real-Time system with an external glucometer to confirm accuracy before dosing. As such, while this is one step closer to an "artificial pancreas," it is not truly a closed-loop system.
References
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