, full-feature insulin pumps are battery-powered devices that infuse rapid-acting insulin just below the skin.
Pumps are programmed to deliver tiny pulses of insulin every few minutes throughout the day and night (the basal insulin) along with larger doses at mealtimes (the bolus insulin).
The insulin is delivered by way of a small, flexible plastic tube or a tiny needle called an infusion set.
The infusion set must be changed every couple of days in order to prevent clogging and infection as well as to ensure consistent insulin absorption.
Figure 5.15: The type of action profile achievable with insulin pump therapy
The infusion set is usually worn on the abdomen, buttocks, arm, or thigh.
The infusion set adheres securely to the skin.
All tubed pumps feature a disconnect mechanism that allows the user to temporarily set the pump and tubing aside for situations such as bathing, contact sports, and intimacy, all while leaving the infusion set portion on the skin.
All pumps are either waterproof or water resistant, and they come with clips that let you attach them to a belt or waistband.
A variety of cases, pouches, and fashion accessories make the pump easy to wear in almost any situation. (See Chapter 10 for a list of companies that offer pump accessories.)
For those who prefer not to spend their spare time doing math, pumps have built-in bolus calculators.
Enter your blood sugar level and the grams of carbs you plan to eat, and the pump recommends a precise dose based on the dosing formulas you and your health care team set up in the pump.
The calculation includes a deduction for “insulin on board”, insulin that is still working from previous boluses.
Each pump keeps a record of all this information in its memory for on-screen recall or downloading to a computer or web-based program.
Some insulin pumps receive data via radio transmissions from blood glucose meters, thus eliminating the need to manually enter the reading when performing a bolus calculation. Some also receive and display data from a continuous glucose monitor.
One unique aspect of full-feature pump therapy is the ability to fine-tune and adjust basal insulin levels throughout the day and night.
For example, if you need more basal insulin in the morning and less in the afternoon or evening, you can program this into the pump.
By matching basal insulin to the liver’s normal output of glucose, glucose levels should hold steady between meals and during the night.
As a result, you can vary your schedule as much as you like in terms of meals, activities, and sleep (imagine: a more “normal” life!).
You can also adjust basal insulin levels on the fly for circumstances such as menstrual cycles, pregnancy, stress, illness, travel, high-fat meals, and extended exercise.
One unique aspect of full-feature pump therapy is the ability to fine-tune and adjust basal insulin levels throughout the day and night.
With insulin pumps, you can administer mealtime insulin at the touch of a button, actually, a sequence of button presses (accidental bolusing is virtually impossible). The doses are highly precise. Some pumps permit dosing in increments as low as one-fortieth of a unit. All pumps offer the option of delivering mealtime boluses all at once or over an extended period of time, in case you expect your meal to take a while to digest.
Benefits of full-feature pump therapy include
1. Better blood sugars. First and foremost, pump users tend to have lower A1cs and less glucose variability (fewer high-to-low and low-to-high swings) than those on injections.
2. Fewer lows. By using only rapid-acting insulin, there is no long-acting insulin peaking or working too hard at inappropriate times. This makes pump therapy a good choice for those who have frequent lows, a history of severe lows, or a hard time detecting low blood sugars.
3.
A more flexible lifestyle. Raise your hand if you can eat, sleep, and exercise at the same times every day. The pump lets you choose your own schedule.
4. Dose calculations. Pumps come equipped with a bolus calculator that helps you determine mealtime doses based on carb intake, blood glucose levels, and the amount of insulin still active from previous boluses. Imagine: no math!
5. Precise dosing. Pumps deliver insulin to the nearest 0.1, 0.05, or 0.025 units, ideal for those who are sensitive to very small doses, such as children and lean or active adults.
6. Convenience. There is no need to draw up syringes or inject with a pen every time you need insulin; just reach for your pump and press a few buttons.
7. Data analysis. Insulin pumps store a ton of historical information that can be displayed on the pump’s screen or transmitted to a computer programs for analysis and fine-tuning.
Potential drawbacks to pump therapy include
1. Cost. Although most insurance plans cover insulin pumps and supplies, there are often copays and deductibles that must be met.
2. Learning curve. When starting on an insulin pump, don’t expect good control right away. You may need a few weeks or months to get the basal and bolus doses properly regulated.
3. Inconvenience. Wearing the pump around-the-clock, even during sleep, can be awkward once in a while. Patch pumps take their share of bumps, and tubing seems to love getting caught on doorknobs and drawer handles.
4. Technical difficulties. As mechanical devices, pumps are prone to occasional infusion set clogs, electronic failures, computer glitches, or damage due to typical wear and tear. A backup plan (in the form of a second pump or programmer and a way to revert back to injections) is an absolute necessity.
5. Skin problems. Skin can sometimes become irritated from infusion set adhesive, and infections can occur if infusion sets are worn too long or inserted improperly. Insulin absorption can be hindered if you do not change infusion sets regularly and rotate sites properly.
6. Ketosis. The absence of long-acting insulin with pump use can present a problem if insulin delivery is interrupted for more than a few hours. Blood sugar can rise very quickly, and ketones may appear in the bloodstream and urine if the problem is not detected and corrected in a timely manner.
7. Infusion set changes. Every couple of days you must change your own infusion set. This three-to-five-minute procedure involves numerous steps and can be momentarily uncomfortable or challenging for some pump users.
Just about anyone with insulin-dependent diabetes and a decent insurance policy can go on an insulin pump. But to succeed with a pump takes preparation and follow-through. I consider the following to be essential prerequisites for anyone seeking an insulin pump:
• motivation and interest in going on a pump, keeping in mind that nobody is 100 percent sure that it is right for them until they give it a try; a bit of hesitancy and anxiety about making the switch to a pump are perfectly normal
• a true state of insulin dependence (type 1 or type 2, with little or no internal or pancreatic insulin production)
• adequate resources to afford the pump and ongoing supplies (via insurance or cash)
• ability to handle basic programming and infusion set changes; a guardian or caregiver can do this if the user is very young or has physical or cognitive disabilities
Certain skills are essential for making a successful transition to pump therapy. The following should be mastered prior to starting on the pump:
• carbohydrate counting (using grams rather than exchanges)
• blood glucose monitoring at least four times a day, or use of a continuous glucose monitor
• record keeping in paper or electronic form (including blood sugars, insulin doses, carb intake, and physical activities)
• self-adjustment of insulin doses (based on blood sugar levels, carb intake, and physical activity)
• an understanding of the basic principles of pump therapy (including the components of a pump and infusion set as well as the role of basal and bolus insulin)
Successful pump use will also require adequate follow-up and fine-tuning. This should include:
• basal rate testing throughout the day and night
• fine-tuning of bolus formulas
• troubleshooting and preventing emergencies such as DKA (diabetic ketoacidosis)
• using advanced pump features such as extended boluses and temporary basal rates
B&B Option 7: Hybrid Closed-Loop (HCL) Systems
HCL systems are really an extension of full-feature insulin pump therapy, whereby the pump receives data from a continuous glucose monitor and has a built-in computer program that adjusts basal insulin delivery automatically every few minutes based on:
• the current glucose level
• the rate of rise or fall in the glucose level
• the amount of insulin on board
• each individual’s sensitivity to insulin
HCLs have the potential to benefit many people with diabetes, but they are not for everyone. While they have the potential to improve glucose control for most people, they can also lead to a worsening of control for those who have managed to achieve very tight management on their own. And some systems add considerable work and disruption to an already demanding health condition, so it is important to weigh the benefits against the drawbacks before deciding whether HCL is right for you or which system is best for you.
Think of it this way: What’s the purpose of a diabetes management device? Is it to lower A1c? Prevent hypoglycemia? Spend more time in range? Some combination of all three? Don’t forget to look beyond blood sugar control. After all, quality of life has to count for something. Does it make living with diabetes safer and easier?
Since HCLs make adjustments based on data received from the linked glucose sensor, it is important that the sensor perform as well as possible.
Accuracy is probably the most important characteristic of a CGM system.
Currently, of all CGMs that link with HCLs, Dexcom G6 offers the best accuracy, followed by Medtronic Guardian and then the Freestyle Libre.
Ease of use is another key feature.
Dexcom and Libre are both highly regarded for their ease of use: neither requires fingerstick calibration, and both are very simple to insert.
The computer algorithm is the second key component of an HCL system.
Those found in the DIY (do-it-yourself?) systems such as the Loop app and Open APS are highly customizable.
Others are very conservative and do not allow the user to customize most of the settings.
The frequency of alarms or alerts and fingerstick calibration requirements also vary from system to system, with DIYs generally producing the least amount of disruption.
However, before jumping to a DIY system, be aware that “off the grid,” non-government-approved systems are not ideal for everyone.
The user must obtain special devices such as old, hackable insulin pumps, carry extra transmission equipment, build their own programming app, and seek out help on their own in the event of technical glitches.
For those who can get past these challenges, the DIY systems can produce tighter control with a highly pleasant user experience.
The insulin pump is the third component of an HCL.
Clearly, not all pumps are ideal for all people.
Since the pump is something that you will interact with and have attached to you just about all the time, consider the size, features, and usability of the pump when considering the various HCL systems.
The good news is that some companies are moving toward HCL systems with interoperable or modular components.
We should soon have the ability to choose a pump from one company, a CGM from another, and a computer algorithm from another, and have them all work together.