Diabetes Insulin Pumps - How They Work
Insulin pumps are widely used in the treatment of diabetes as a replacement for insulin injections. This article gives information about the features that an insulin pump has and how it works, to ensure that the right amount of insulin is available at all times of the day and night.
Insulin pumps, used to provide a continuous supply of insulin rather than a series of injections through the day, are being used more and more commonly in the treatment of diabetes. They vary from one manufacturer to another but have a number of core features and also some variations. This article will help you to understand how an insulin pump can be used to deal with the variable insulin requirements throughout the day.
Basal rate insulin
This is the term used for the insulin dose that is given continuously. When someone starts using an insulin pump, it is set on an hourly rate which roughly corresponds with a slightly lower rate than the person's existing insulin doses (to avoid hypos). The person then checks their blood glucose frequently to establish which parts of the day need an increased dose and which parts need less insulin. Up to 48 different rates can be programmed into most pumps, so it can change as often as every half hour if necessary.
Insulin pumps also have a temporary basal rate function. This means that either an increased or a decreased rate can be set for a specific, short period of time chosen by the pump user. So if someone is unwell and their blood glucose rises, they can have additional insulin over a number of hours without changing their main basal rate. Also, if someone is taking some sort of exercise, which can result in blood glucose levels dropping, they can reduce their insulin dose for a period of time to avoid this. This feature makes the insulin pump extremely flexible and helps to fit insulin treatment into people's everyday lives.
Insulin bolus doses
A bolus dose of insulin is when additional insulin is given as a one-off dose. There are two main uses for this: to give more insulin at any time that carbohydrates are eaten, or to bring down a high blood glucose reading.
For insulin given with food, the pump user will (through trial and error, and with guidance from health professionals) learn how much insulin is needed for the amount of carbohydrate given - known as an 'insulin to carbohydrate' ratio. An example would be one unit of insulin for 10 grams of carbohydrate, or one unit of insulin for 5 grams of carbohydrate. This means that whatever food is eaten, the precise amount of insulin can be worked out and given at the time.
For insulin to bring down a high blood glucose, known as a 'correction dose', in a similar way to the food example above, the pump user learns how much effect a single unit of insulin will have on their blood glucose, and uses their 'correction ratio' (for example one unit to 4 mmol/l of blood glucose) to work out how much insulin is needed to bring their blood glucose level back into the range they are aiming for.
Bolus doses can be given immediately, or can be given over an amount of time. For example, if the food being eaten is very high in fat, it will digest quite slowly, so it might be better to let the extra insulin trickle in over 30-45 minutes rather than give it all when the meal is eaten. Similarly, if eating snack foods at a party, the pump can be programmed to give a number of units over a specified time to deal with this. Pumps can also be programmed to give a dose of insulin in a combination of some immediately and some over a longer period.
Blood glucose and insulin doses
Because the insulin doses given by a pump need to be closely connected with the pump user's blood glucose level, pumps are beginning to have a number of features that relate to this. Some pumps have a built-in blood glucose meter, some have a continuous monitoring device (although this usually isn't used all the time), and some have the option of programming in a blood glucose reading.
The advantage of this technology is that the pump can then work out how much insulin might be needed, on the basis of the correction ratio and the insulin to carbohydrate ratio, which are also programmed in. So if someone was about to eat a meal, they could program in the amount of carbohydrate they were going to eat and the pump could tell them how much insulin they would need.
In some cases, the pump can also hold a 'memory' of different foods and their carbohydrate values - usually developed by the pump user - so that someone could just look up 'potatoes' and the amount of insulin per 10g, or the amount per their usual portion, would be given.
All of these features reduce the potential for error, particularly in mathematical calculations which are difficult for most of us!
Other pump features
There are numerous other pump features that can be present. Standard features include alarms (audible beeps, vibrations or both) to let the person know if there is a problem with their pump or if their insulin supply or battery is running low. Also pumps have memories, so for example the last dose of insulin, the total insulin used in a day, or trends in insulin doses over periods of time can be looked up. The pump keys can be locked, for example to prevent an extra dose of insulin accidentally being given at night, and pumps also have some degree of water resistance, most being splashproof but not waterproof.
Extra features of some pumps include alarm settings for low blood glucose readings, different methods of computer downloading, being able to program the pump from a computer, remote controls to give insulin discretely, and storage of the amount of insulin needed for the usual meals of the pump user.
For anyone wanting to use an insulin pump, checking out what features they feel are most important, and finding a pump that they feel is easy to use, are important aspects of choosing which pump will suit them best.
Jill Rodgers is Business Director of Successful Diabetes, www,successfuldiabetes.com, and has written the UK's first-ever insulin pump book 'Using insulin pumps in diabetes', published by John Wiley & Sons Ltd in 2008.
Basal rate insulin
This is the term used for the insulin dose that is given continuously. When someone starts using an insulin pump, it is set on an hourly rate which roughly corresponds with a slightly lower rate than the person's existing insulin doses (to avoid hypos). The person then checks their blood glucose frequently to establish which parts of the day need an increased dose and which parts need less insulin. Up to 48 different rates can be programmed into most pumps, so it can change as often as every half hour if necessary.
Insulin pumps also have a temporary basal rate function. This means that either an increased or a decreased rate can be set for a specific, short period of time chosen by the pump user. So if someone is unwell and their blood glucose rises, they can have additional insulin over a number of hours without changing their main basal rate. Also, if someone is taking some sort of exercise, which can result in blood glucose levels dropping, they can reduce their insulin dose for a period of time to avoid this. This feature makes the insulin pump extremely flexible and helps to fit insulin treatment into people's everyday lives.
Insulin bolus doses
A bolus dose of insulin is when additional insulin is given as a one-off dose. There are two main uses for this: to give more insulin at any time that carbohydrates are eaten, or to bring down a high blood glucose reading.
For insulin given with food, the pump user will (through trial and error, and with guidance from health professionals) learn how much insulin is needed for the amount of carbohydrate given - known as an 'insulin to carbohydrate' ratio. An example would be one unit of insulin for 10 grams of carbohydrate, or one unit of insulin for 5 grams of carbohydrate. This means that whatever food is eaten, the precise amount of insulin can be worked out and given at the time.
For insulin to bring down a high blood glucose, known as a 'correction dose', in a similar way to the food example above, the pump user learns how much effect a single unit of insulin will have on their blood glucose, and uses their 'correction ratio' (for example one unit to 4 mmol/l of blood glucose) to work out how much insulin is needed to bring their blood glucose level back into the range they are aiming for.
Bolus doses can be given immediately, or can be given over an amount of time. For example, if the food being eaten is very high in fat, it will digest quite slowly, so it might be better to let the extra insulin trickle in over 30-45 minutes rather than give it all when the meal is eaten. Similarly, if eating snack foods at a party, the pump can be programmed to give a number of units over a specified time to deal with this. Pumps can also be programmed to give a dose of insulin in a combination of some immediately and some over a longer period.
Blood glucose and insulin doses
Because the insulin doses given by a pump need to be closely connected with the pump user's blood glucose level, pumps are beginning to have a number of features that relate to this. Some pumps have a built-in blood glucose meter, some have a continuous monitoring device (although this usually isn't used all the time), and some have the option of programming in a blood glucose reading.
The advantage of this technology is that the pump can then work out how much insulin might be needed, on the basis of the correction ratio and the insulin to carbohydrate ratio, which are also programmed in. So if someone was about to eat a meal, they could program in the amount of carbohydrate they were going to eat and the pump could tell them how much insulin they would need.
In some cases, the pump can also hold a 'memory' of different foods and their carbohydrate values - usually developed by the pump user - so that someone could just look up 'potatoes' and the amount of insulin per 10g, or the amount per their usual portion, would be given.
All of these features reduce the potential for error, particularly in mathematical calculations which are difficult for most of us!
Other pump features
There are numerous other pump features that can be present. Standard features include alarms (audible beeps, vibrations or both) to let the person know if there is a problem with their pump or if their insulin supply or battery is running low. Also pumps have memories, so for example the last dose of insulin, the total insulin used in a day, or trends in insulin doses over periods of time can be looked up. The pump keys can be locked, for example to prevent an extra dose of insulin accidentally being given at night, and pumps also have some degree of water resistance, most being splashproof but not waterproof.
Extra features of some pumps include alarm settings for low blood glucose readings, different methods of computer downloading, being able to program the pump from a computer, remote controls to give insulin discretely, and storage of the amount of insulin needed for the usual meals of the pump user.
For anyone wanting to use an insulin pump, checking out what features they feel are most important, and finding a pump that they feel is easy to use, are important aspects of choosing which pump will suit them best.
Jill Rodgers is Business Director of Successful Diabetes, www,successfuldiabetes.com, and has written the UK's first-ever insulin pump book 'Using insulin pumps in diabetes', published by John Wiley & Sons Ltd in 2008.
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