|Coombe Abbey Hotel and Conference Centre, June 2015|
Insulin Pumps and Insulin Pens
A working pancreas responds automatically to blood glucose levels, secreting exactly the right amount of insulin to maintain blood glucose within the ideal range. The person with diabetes has to take on the role of the pancreas by measuring capillary blood glucose via a finger-prick, then guessing at what blood glucose levels will do next, and injecting insulin according to their guess. Insulin pen users inject a long-acting insulin once or twice a day and rapid-acting insulin at mealtimes or with snacks, or else a twice-a-day mixture of long- and short-acting insulins.
The insulin pump is designed to try and mimic the physiological action of a working pancreas more closely. It contains a reservoir of rapid-acting insulin, and a background rate is programmed to inject this dripwise at an adjustable rate instead of the daily or twice-daily injections of long-acting insulin. With food there is the same process of estimation and guesswork about what blood glucose is likely to do, and the user tells the pump how much insulin to deliver from the same reservoir of rapid-acting insulin.
The pump delivers its insulin into subcutaneous fat via a cannula, which is a hollow needle made of metal or teflon that you insert into your body. The cannula stays in place for only two or three days otherwise you risk irritation around the insertion site and the formation of lipohypertrophy, which is a lump caused by insulin being delivered into a specific location for too long. Available sites are round the abdomen, the top of the buttocks, back of arms and sides of legs as long as there is a decent covering of fat - the same locations as for standard insulin injections.
Benefits and drawbacks
We often come across people in our service who are desperate to have a pump because they think it will make their diabetes management easier. In fact a pump is no easy option, and if you don't put any effort into managing diet and insulin and lifestyle then your outcomes will be as bad or worse than on multiple injections with an insulin pen. None of the benefits I list below relate to doing less work in managing calculations and all the rest of the overheads associated with doing the job of your defunct pancreas.
Disconnect the pump for more than an hour and you start to risk rising blood glucose levels, because you don't have any long-acting insulin in your system. After about four hours insulin-free there is the further risk of developing ketoacidosis, which is unpleasant at best and life-threatening at worst. So another disadvantage is that if anything goes wrong with the pump or your cannula or your insulin, you'd better have a back-up option handy or you might find yourself in A&E. If you're away from home, even on a short trip, you may find the journey cut short or have to make a whole lot of calls or trips to hospitals or pharmacies unless you carry spare equipment with you.
One clear advantage of the pump is fewer injections - in the three days that one cannula lasts you might expect to give at least 12 injections using a pen, and probably more. Another advantage of the pump is the ability to reduce your dose of insulin as well as increase it - with a pen, once the injection is given you can't dial the dose down. The third main advantage is that the background dose can be varied in a diurnal pattern that better matches the body's requirement for insulin, and the fourth advantage is that insulin to match food can be delivered in an adjustable dose over a period of time, which better mimics the action of a working pancreas compared with one or more isolated injections. Lastly, insulin pens only allow administration of insulin in whole (or occasionally half) units, while the pump can deliver much smaller amounts.
Other pump features
The pumps on the market also have no end of other features that are useful rather than necessary, like alarms, and the ability to download data from the handset and pump for viewing in all sorts of different ways designed to help you improve your carb counting and insulin delivery. The software for the pump that nearly all our patients use has some further features such as the ability to create a new profile by adjusting the background insulin up or down by a percentage - the alternative would be to change each of the 24 hourly settings using the pump or handset menus. The main feature that this pump lacks is the ability to upload all its data to the Internet so that it can be accessed anywhere. In our department we can only view the data on the specific computer that it's downloaded to, although we're working on a networked option so at least we can see the data on more than one computer in the building.
Mr M has a number of objections to the way the the software for his pump works that are probably a bit too technical to discuss here. I expect there are annoying features with every pump and handset. We recently held a session where we invited all the different pump manufacturers to show us their wares in an afternoon, and while they all do roughly the same job they are all quite different.
Coming soon: Part 2 of the Pumping Insulin series covers my own experience on the course, including wearing a pump myself for 12 hours.