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American Diabetes Association
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Alexandria, Virginia 22311
DOI: 10.2337/9781580404617
Library of Congress Cataloging-in-Publication Data Kaufman, Francine Ratner. Insulin pumps and continuous glucose monitoring / Francine R. Kaufman, with Emily Westfall. — 1st ed. p. cm. Includes bibliographical references and index. ISBN 978-1-58040-461-7 (alk. paper) 1. Insulin pumps. 2. Diabetes—Treatment. 3. Insulin—Therapeutic use. 4. Blood sugar monitoring. 5. Patient education. I. Westfall, Emily. II. American Diabetes Association. III. Title. RC661.I63K38 2012 616.4’62061—dc23 2011050394 eISBN: 978-1-58040-499-0
CONTENTS
Chapter 1: What You Need to Know about Diabetes
Chapter 2: An Overview of Insulin Pumps
Chapter 3: How Does My Pump Work?
Chapter 4: All about Basal Rates
Chapter 5: All about Boluses
Chapter 6: Understanding the Meal Plan
Chapter 7: Understanding the Impact of Physical Activity
Chapter 8: The Facts about Infusion Sets
Chapter 9: Special Circumstances: Sick Days, In-Hospital Use, Discontinuing Pump Therapy
Chapter 10: Travel with the Pump
Chapter 11: The Pump at School: From the Beginning through College
SECTION 3: ADJUSTING TO INSULIN PUMP THERAPY
Chapter 12: Capabilities by Age
Chapter 13: Attitudes about the Pump
SECTION 4: CONTINUOUS GLUCOSE MONITORING
Chapter 14: The Facts about Continuous Glucose Monitoring
Chapter 15: How to Use Continuous Glucose Monitors and Pumps
SECTION 5: A LOOK INTO THE FUTURE
Chapter 16: A Look into the Future
I would like to acknowledge the contribution that Dr. Harry Keen made to the field of insulin pump therapy. Harry gave birth to the notion and was visionary in realizing what it could do to improve the lives of those dependent on exogenous insulin treatment. I would also like to acknowledge all that Dr. John Pickup has done to help bring pump therapy to life.
I would like to thank Talia Rabb, who helped me conceive of how to frame this book. I would also like to thank Kelly Joy, Linda Burkett, Kathy Beaver, and Susan Bristol. Their advice and editing were invaluable.
I met Emily Westfall by serendipity on a plane. During that brief encounter, I was so impressed (and in need of help with organizing this book) that I asked her if she wanted to assist me. She was an amazing collaborator, and I am grateful she sat next to me and said yes to my request.
As always, my inspiration comes from my patients and their families, along with my husband, Neal Kaufman, MD, and my own children.
I remember the first insulin pump I used with my patients in the early 1980s. It was jokingly referred to as the “big blue brick,” and it weighed several pounds. The insulin-filled syringe was on the outside of the pump, the pump used a butterfly needle (the needle commonly used for intravenous delivery of medications) placed in the subcutaneous tissue, and, for the most part, it could only be used in the hospital setting. I remember feeling that this was a great advance for my patients, and I appreciated that they benefited from the continuous delivery of basal insulin and from the intermittent boluses that were given to match their food intake and to correct an abnormal blood glucose level when indicated. When I reflect back, I realize we have come a long way over the ensuing 30 years. We have witnessed incredible advances in the understanding of what happens to the cells of the body as the result of the diabetes process. We have seen tremendous breakthroughs in diabetes drug discovery, including the development of insulin analogs, and rapid advances in glucose monitoring technology. We have determined better ways to deliver diabetes education and support, and we continue to combat discrimination against people with diabetes. And most importantly for this book, today we have insulin pumps that are small, fast, and smart, and we have continuous glucose monitors (CGMs). CGMs can give information in real time to help with diabetes management decisions. With some devices, the pump and the CGM work together in a single system.
When I diagnose someone with diabetes, I feel as if I start him or her on a new, different life’s journey. To succeed on that journey, one must effectively manage diabetes so that the maximal amount of time is spent with glucose levels in the target range, and the minimum amount of time in the low or high range. To accomplish this, people with diabetes, and their parents or caregivers, must track glucose levels to be able to deliver insulin in a manner that closely resembles how the body produces and uses its own insulin. Often the best way to achieve this is to use an insulin pump. And this may be accompanied by using a CGM. These technologies—although not really that much more complicated than your smartphone, computer, or DVD—do require basic understanding, training, and follow-up adjustment if they are going to be helpful in improving diabetes outcomes. The purpose of this book is to give you practical tips, including the knowledge and the skills to maximize insulin pump therapy and continuous glucose monitoring, if that is what you and your health care provider decide is best for you or your child. The goal is to enable you to make your journey through life with diabetes as successful as possible.
The goal of section 1 is to review the basic physiology of glucose control and what occurs when someone has diabetes. To understand what you are striving for, you must also be aware of glucose and A1C targets. The central principles of how diabetes is now managed are supported by a series of important research studies. The critical ones, such as the Diabetes Control and Complications Trial (DCCT) and important research studies concerning insulin pump therapy, are reviewed so that you understand the evidence surrounding the recommendations for meticulous diabetes control.
The insulin pump is a small mechanical device worn by someone who has diabetes and who is treated with insulin. The insulin pump helps facilitate diabetes control and lifestyle flexibility. Insulin enters the body from the pump after flowing down the tubing into a small cannula, which is a soft tube, or through a small needle placed under the skin. Newer pumps don’t even use tubing. The insulin regimen used by insulin pumps is called basal-bolus therapy, and the benefits of basal-bolus therapy will be outlined. In addition, you’ll see how you can balance insulin administration, food, and activity with greater ease while using an insulin pump.
Section 2 gets into the practical aspects of insulin pump therapy. The components and features of the pump are described, emphasizing the pump’s bolus calculator. Sections on both basal and bolus insulin delivery cover all aspects: from how to determine your initial pump settings to how to adjust settings over time. Because food is a critical element in diabetes management, there is a detailed discussion of carbohydrates, understanding how to read food labels, and ways to assess your portions. One of the true challenges in diabetes management is adjusting insulin and carbohydrate intake for planned and unplanned physical activity. An in-depth review of principles to manage exercise are given in this section.
To succeed with insulin pump therapy, it is critical to understand infusion sets, know how infusion sets differ, and what you need to consider in making the decision about which set you want to use. Although diabetes management can be challenging when you are at home, feeling well, and following your standard routine, special circumstances can make diabetes management more challenging. Situations like illness, traveling (particularly across time zones), or going off to school or college can affect glucose control. Understanding how to adjust your regimen and what do to with your glucose numbers is reviewed in this section.
SECTION 3: ADJUSTING TO INSULIN PUMP THERAPY
Section 3 covers the developmental capabilities of children with regard to managing pumps. You should have realistic expectations of what your child can do with his or her increasing self-management skills. If you don’t know what is reasonable, then you might push or hold back your child in the quest for independence.
When you begin pump therapy, it is like starting all over again. You have to check glucose levels more often, wake up in the night, assess and adjust, and think about diabetes all of the time. This can cause stress in and of itself. Deciding whom to tell about your pump, what it means to be attached to a device, and how your body image might be affected are critical issues in accepting—and ultimately succeeding with—pump therapy.
SECTION 4: CONTINUOUS GLUCOSE MONITORING AND PUMPS
There is increasing evidence of the benefits of continuous glucose monitoring. Having a glucose value displayed continuously and the ability to see trends in glucose levels can improve glucose control and help you avoid serious highs and lows. However, continuous glucose monitoring involves adding another device to your self-care toolbox and learning how to use the additional information that comes from it.
The goal of this section is to give you the information you need to start and succeed with continuous glucose monitoring. How the devices work, what the graphs and numbers mean, and how to integrate this new tool into your life will be discussed.
SECTION 5: A LOOK INTO THE FUTURE
Section 5 will give you a glimpse into the future. There is no doubt that the companies involved in diabetes technology, the diabetes associations—including the Juvenile Diabetes Research Foundation (JDRF), the Helmsley Trust, and the American Diabetes Association (ADA)—and many diabetes researchers are interested in seeing the “artificial pancreas” developed to benefit people with diabetes. The goal of the artificial pancreas is to deliver insulin automatically, almost minute to minute, in response to the glucose levels obtained in real time by the glucose sensor—just like the human pancreas does. Achieving this, however, requires a series of algorithms—mathematical equations that take into account a number of things, such as the glucose level at the time, the immediately prior glucose levels, and the rate of change of the glucose value, as well as how much insulin has already been delivered, and insulin sensitivity, to name a few. Ideally, the end result is near-perfect control of glucose levels without much human intervention. The dream of the artificial pancreas will become a reality through incremental steps that will make insulin pumps more automatic in their operation. We already have pumps that automatically suspend insulin delivery for actual hypoglycemia. In the near future, we may see pumps suspend insulin for predicted hypoglycemia, give an automatic bolus for sustained high glucose levels, or completely control insulin delivery during sleep. The future is bright, and sharing its promise with you will conclude the book.
The goal of this book is to help you understand why you or your child might want to use an insulin pump and a CGM, to give you the skills to use them, and to help you optimize your or your child’s journey with diabetes. Insulin pumps and CGMs may seem overwhelming at the beginning, but trust me, using them can become second nature in no time at all.
SECTION 1: THE BASICS
CHAPTER 1 WHAT YOU NEED TO KNOW ABOUT DIABETES
IN THIS CHAPTER
• Understanding the Basics about Insulin
• Understanding the Transition from Injections to Pumps
• Know Your Glucose and A1C Targets
• Research Supports Multiple Daily Insulin Injections and Insulin Pump Therapy
I bet you can remember the day you found out you or your child had diabetes. It is likely that you knew something was wrong for a few days—maybe even weeks—before the diagnosis was made, but you thought it was the flu or a new phase in your life or in your child’s development. It is possible you even called your doctor and were told that the problem would go away soon and that there was likely nothing to worry about. Obviously, that wasn’t the case.
Some children, teens, and adults are diagnosed with diabetes very early in the process, before they become sick. Some are diagnosed only after they become seriously ill. But most have some, if not all, of the typical signs and symptoms of diabetes: frequent urination, increased thirst, weight loss, and fatigue. These signs and symptoms occur because the pancreas can no longer make enough insulin. Without enough insulin, multiple problems occur with metabolism within the body.
And now remember how remarkable it was just a few days after you were given insulin by injection or through an intravenous infusion (an IV). You were back to your usual self—active, hungry, gaining weight, and learning all about diabetes.
Look back at the first tasks you were asked to do: you had to start to give insulin shots and check blood glucose levels before you had even had a chance to adjust to the fact that you had diabetes. In those first days, you were mostly asked to read, study, and listen to lectures about this disease. You must have felt overwhelmed as it became apparent you were expected to become an expert, something that took me (and all my health-care-provider friends) years and years to accomplish.
You were likely given a list of things to do and a schedule of when to do them after you were first diagnosed, like in the example above. But essentially, by this time you were aware that every day you need to:
1. Take insulin to be able to metabolize food (mainly carbohydrate) and control the release of glucose from body stores
2. Measure glucose levels throughout the day and night to determine whether insulin doses are working properly
3. Eat a healthy and balanced diet, understand the quantity and quality of food, and couple food with taking insulin
4. Be physically active and understand the role of activity in glucose management.
So see how far you have come from those first days? You have come far enough to now consider using an insulin pump and a continuous glucose monitor (CGM)—and to stay committed to doing what you can to optimize your journey with diabetes.
UNDERSTANDING THE BASICS ABOUT INSULIN
In a person who does not have diabetes, the body is designed to control glucose levels in the blood in a very tight range. Although there are fluctuations of glucose levels throughout the day and night, generally glucose levels fall between 70 and 140 mg/dL— highest after eating and lowest after fasting (not eating). Insulin is secreted to keep the glucose that is released from your food or your body’s stores moving into your body’s cells, where it is used as fuel.
Insulin is secreted in two ways: 1. background (called basal insulin), and 2. surges (called bolus insulin).
1. Background (or basal) insulin controls the glucose levels between meals and overnight. It is mainly acting to help regulate how much glucose is released from the stores in the liver (where it is stored as glycogen). The release of glucose from the liver between meals is critical for providing energy so the body’s cells can function. Without enough background or basal insulin, your liver would release too much glucose into the bloodstream and your cells would not be able to use it for energy. This could result in very high blood glucose levels. Additionally, without background insulin, the liver will start to produce acidic ketone bodies from the breakdown of fat. Like sugar, these ketone bodies can be measured in the blood and in the urine. As ketones build up in the bloodstream, there is the risk of developing diabetic ketoacidosis (known as DKA). This is potentially a very dangerous condition.
2. Surge insulin (or bolus) occurs at mealtime. As glucose levels rise from meals, the pancreas responds with a large increase in insulin release, so the glucose can be used by the body’s cells. In the human body without diabetes, these surges are very precise: eat more, and more insulin is released; eat less, and less is released.
With diabetes (always in type 1 and sometimes in type 2), the ability to release insulin is lost. Since the discovery of insulin, replacement insulin therapy has evolved into the modern system we have today. The older system used a fixed approach to insulin replacement (though this is still used today). Although you took only one to three shots a day, you had to take injections at set times and in set amounts. You had to eat the same amount of food at the same time every day, and you had to exercise at the same time every day. With this old way, keeping glucose in the target range was very difficult. And there was no flexibility in life. Essentially, your life had to fit into the diabetes regimen. The diabetes regimen controlled you.
The newer way to treat diabetes is with flexible regimens: multiple daily injections (MDI) or insulin pump therapy. These newer, flexible systems mimic the way the pancreas normally produces and releases insulin. MDI mimics background insulin and surges of insulin. It allows you to deliver insulin in doses to match your food intake and gives you flexibility in how much you eat and when you eat it. You can be active when you want, and with an insulin pump you can decrease basal insulin in order to avoid hypoglycemia. You can sleep when you want, wake up late, and travel around the globe with the flexibility to change from one day to the next.
UNDERSTANDING THE TRANSITION FROM INJECTIONS TO PUMPS
You are likely taking multiple injections of insulin every day—possibly two or three injections (perhaps using NPH insulin)—but you are most likely on MDI. With MDI, you use rapid-acting insulin and long-acting or basal insulin. These two different kinds of insulins have different jobs, but both work to keep your glucose in the target range.
Basal insulin is given as one or two shots each day, and it activates slowly after injection. This means that some amount of insulin will always be present in the blood. The blood can then bring insulin to the cells throughout the body, and glucose can then enter the cells, where it is converted into energy. In the liver, insulin helps regulate the slow release of stored glucose to meet the energy needs of the body’s cells between meals and during the night.
Bolus insulin is given as rapid-acting insulin. It is activated much faster after injection and brings the large amount of glucose from your meals into your body’s cells. There, glucose can be used right away for energy or stored for later use. Boluses with rapid-acting insulin can also be used to decrease a high blood glucose level. These doses are called correction boluses.
The difference between an insulin pump and MDI is that an insulin pump just uses rapid-acting insulin to do both jobs. The basal rates on the pump replace the basal insulin injection in MDI, and boluses given at meals and for correction replace the mealtime and correction shots.
KNOW YOUR GLUCOSE AND A1C TARGETS
What is the ultimate goal of diabetes treatment? To effectively manage diabetes day to day, so that glucose levels are in the right range—known as the target range—as much as possible to avoid highs and lows. Keeping glucose levels in the target range minimizes your risk of the short- and long-term complications. The target range for glucose is different at different times of the day. For example, in the morning when you haven’t eaten for several hours (fasting), your target will be lower than it is after meals, when blood glucose is highest. Overnight, when you are sleeping, your target may be higher than the fasting range to protect you from hypoglycemia.
The American Diabetes Association (ADA) has established general target ranges for glucose levels throughout the day for different age groups. Generally speaking, younger children have higher targets for their glucose levels. In addition, there are a number of conditions that might lead the diabetes team to suggest higher targets, such as having repeated low blood glucose (hypoglycemia), being unaware of the symptoms of hypoglycemia (referred to as hypoglycemia unawareness), or having diabetes complications. You should discuss this with your diabetes team and find out what your target range glucose levels should be throughout the day and night.
Similarly, you should be aware of the target range for your A1C test. A1C measures the percentage (%) of your hemoglobin (a protein in red blood cells) molecules that have glucose attached to them. The higher your average glucose levels day after day, the higher your A1C. It gives you a good picture of what your blood glucose levels have been in general over a longer amount of time. A1C should be measured every three to four months, and you should know what your level is each time it is taken. A1C is often referred to as the diabetes report card. By seeing if your A1C is in the target range set by your diabetes team, you can know if your diabetes control is optimal.
RESEARCH SUPPORTS MDI AND INSULIN PUMP THERAPY
There have been a lot of research studies in the fields of MDI and insulin pump therapy, and many of them have shown that there are potential benefits in diabetes care. Here are some studies that have helped us better understand how to manage diabetes and how MDI and particularly insulin pump therapy can be a useful tool.
The Diabetes Control and Complications Trial (DCCT)
Before the mid-1990s, someone with type 1 diabetes would take one (maybe two or, rarely, three) insulin injections per day. Back then, regular, NPH, lente, and ultralente insulins were in use. Except for NPH and regular, these other insulin preparations are not available today. Insulin doses weren’t adjusted from one day to the next, which meant that people had to follow a strict eating plan and physical activity regimen. That meant you couldn’t skip breakfast, you couldn’t delay having lunch, and if you routinely had a snack in the afternoon, you had to eat one even if you weren’t hungry! Although you might have taken fewer shots, the trade-off in having a fixed diet and activity pattern wasn’t worth it—and more importantly, this regimen led to inadequate diabetes control.
The Diabetes Control and Complications Trial (known as the DCCT) was a nine-year study. When the results were reported in 1993, the concept of how diabetes should be managed was changed forever. The investigators proved that tighter glucose control using MDI (three or more shots per day) or insulin pump therapy was better than conventional therapy at lowering A1C and reducing the risks of developing diabetes complications.
The DCCT conclusively showed that blood glucose control matters. Although the youngest participants in the DCCT were 13 years old when they entered the study, the overall results of the DCCT have been generalized to all of type 1 diabetes: effective blood glucose control is the most effective way to reduce the long-term complications of diabetes.
Over 1,400 people with type 1 diabetes took part in the study. They were divided among two groups: one for intensive management and the other for conventional therapy (the way diabetes used to be managed). The intensive group used MDI (three or more shots per day) or an insulin pump. This group also received a great deal of support from the study teams. At the end of the DCCT, the people who used MDI had an average A1C level of 7.4%. Those receiving conventional therapy took one or two shots a day, and did not have blood glucose targets or a lot of support from the study teams. Their average A1C levels were 9.1%. Nine years later, those in the intensive group had fewer severe eye, kidney, and nerve problems than those in the conventional group. This was a stunning discovery. However, the other lesson from the DCCT was that lowering A1C levels increases the risk of hypoglycemia.
Epidemiology of Diabetes Interventions and Complications (EDIC)
After the DCCT concluded in 1993, a follow-up study began, and it is still running today. The study is called Epidemiology of Diabetes Interventions and Complications (EDIC), and almost all of the DCCT participants entered into it (but they did return to their previous health care teams, not the study teams). By 2009, those who had been in the intensive group had lower rates of eye disease, kidney disease, and cardiovascular disease when compared with those in the conventional group. Although the people in the intensive group did see an increase in their average A1C levels over this period, there was still convincing evidence that intensive management and improved A1C levels provide noticeable health benefits, even if the therapy was provided years before. That is why considering an insulin pump to manage your diabetes makes sense.
LESSONS FROM DCCT AND EDIC
After 30 years of diabetes, fewer than 1% of participants in the intensive group had become blind, required kidney replacement, or had an amputation because of diabetes.
Other Studies and Guidelines
Many studies have evaluated insulin pump therapy. Although none have had the scientific rigor of the DCCT, overall they show that insulin pump therapy decreases A1C, and now it has also been shown to reduce rates of hypoglycemia. These studies have been done across age groups, for different conditions (such as pregnancy or severe hypoglycemia), and in many places around the globe. There have been 11 studies that compared insulin pumps to MDI, and across all of them, A1C was approximately 0.5% lower in those using insulin pumps. Regardless of who is using the insulin pump, the studies have shown an overwhelmingly positive benefit.
Studies with Sensors and Sensor-Augmented Pumps
A CGM is a device that can give information in real time to help with diabetes management decisions. With some devices, the pump and the CGM work together in a single system. The expanded availability and use of CGMs can be partially credited to clinical research into this new device. Some of the studies looked at the use of insulin pump therapy integrated with a CGM. This type of therapy is often called sensor-augmented pump therapy, or SAPT. Other studies looked at the benefits of individuals using a CGM either with an insulin pump or with MDI.
The Juvenile Diabetes Research Foundation (JDRF) sponsored one of the largest studies ever done on CGMs. The study included 322 adults and children who were receiving intensive therapy for type 1 diabetes (either with an insulin pump or MDI). After six months, adults showed improved blood glucose control. A subset of children and adults whose A1C values were less than 7.0% at the beginning of the study was also analyzed. In this group of individuals, low blood glucose (hypoglycemia) was less frequent, time spent out of the target blood glucose range was shorter, and average A1C levels were still excellent. The benefits of CGM go beyond just the clinical benefits and improved glucose control: the adults and parents of children who used CGM were also pleased with this method of treatment.
In 2010, the results of the STAR 3 study were published in the New England Journal of Medicine. The STAR 3 study is the largest study of its kind, and it examined the benefits of SAPT in people with type 1 diabetes comparing it against MDI. The study demonstrated that in both children and adults with inadequately controlled type 1 diabetes, SAPT improved A1C levels. A1C levels were 0.6% lower than those in the MDI group. Also, a greater number of individuals reached their A1C target levels.
Once the STAR 3 study was completed, the patients receiving MDI in the first year of the study were placed on SAPT for six months. They were compared with the people who received SAPT during the first year of the study and who continued on SAPT for the same six-month period. There was a significant and sustained decrease in A1C levels in the children and adults who went from MDI to SAPT for the final six months of the study.
One of the most important lessons we’ve learned from all of the clinical studies done with SAPT is that the biggest treatment benefit is seen in those individuals who use CGM on a consistent and sustained basis. The greatest improvement in blood glucose control was seen in individuals who wore the CGM for more than 60% of the time. This was true for children, adolescents, and adults.
Guidelines
In 2005, the American Diabetes Association published its guidelines for the management of diabetes in children: “The Care of Children and Adolescents with Type 1 Diabetes.” Here are a few of the key items from those guidelines:
• Insulin pump use is widespread in children with diabetes.
• There is no correct age at which to initiate insulin pump therapy, so treatment plans should consider the needs of the patient as well as those of the family to determine who is an appropriate candidate for an insulin pump and when he or she should begin pump therapy.
• The support of adults at home and at school is essential for the child’s success with all diabetes management, but especially with pump therapy.
Other medical associations have published recommendations. The International Society for Pediatric and Adolescent Diabetes published theirs in 2009. That guideline explains that insulin pump therapy is the best way to imitate how a human body without diabetes provides insulin. The American Association of Clinical Endocrinologists has a consensus statement that discusses the broad groups of patients with type 1 and type 2 diabetes who may benefit from insulin pump therapy.
CHAPTER REVIEW
• Appreciate how far you have come since your original diagnosis. You have learned so much about diabetes management, the tasks you need to perform, and ways to better control your glucose levels.
• The concepts of basal and bolus insulin delivery are the keys to pump therapy. Either method can be adjusted throughout the day and night to improve glucose control.
• Transitioning from MDI to pump therapy means you go from taking two
(or maybe even more) kinds of insulin to one—only rapid-acting insulin.
• You should know your blood glucose and A1C targets. You adjust your insulin doses, food intake, and activity levels to reach your glucose targets throughout the day and night. At your diabetes visits, find out your A1C so you can know if you have achieved your goal.
• There is a lot of evidence from scientific studies that shows the benefits of insulin pump therapy. Pumps reduce hypoglycemia, improve A1C levels, improve quality of life, and reduce daily insulin dosages. CGM has the ability to further improve diabetes care, particularly when used most of the time.
CHAPTER 2 AN OVERVIEW OF INSULIN PUMPS
IN THIS CHAPTER
• What Exactly Is an Insulin Pump?
• What Makes You a Good Pump Candidate?
WHAT EXACTLY IS AN INSULIN PUMP?
Simply put, an insulin pump is a device to deliver insulin. It is a small mechanical device that is worn externally. It is prescribed by your physician, and your diabetes team will determine your starting doses. You will need to learn how to program the pump, and then you will be responsible for telling it how much insulin to give you. You program it to provide both basal (the background insulin) and bolus
insulin (for meals and correction doses). A computer in the pump regulates the flow of insulin into the body. An insulin pump eliminates the use of daily injections and uses only rapid-acting insulin both for the basal rates and for boluses.
Durable Pumps and Patch Pumps
Durable insulin pumps are about the size of a deck of cards and can come in a variety of types and colors. Most pumps are connected to the body by tubing. This tubing runs from a reservoir filled with insulin in the pump to an infusion set, which is secured to your body. The infusion set is made up of a small 6–9 mm (less than ½ inch) soft plastic cannula that is inserted under the skin. It is inserted by a needle, which is then removed. The cannula can also be a very small steel needle that is easily inserted under the skin. The computer in the pump controls a motor that that dispenses the insulin in tiny amounts. The insulin flows from the reservoir into the tubing and then through the cannula into the tissue under the skin. There is a display screen on the pump, and buttons to program insulin delivery.
Patch pumps are attached directly to the body. They do not have an infusion set or tubing. The insulin reservoir is inside the patch, and you fill the reservoir before placing the patch on your body. There is a needle that places a small cannula under the skin, and this needle then retracts back, so it is no longer in the body. These pumps have a separate controller that communicates with the motor in the patch to control insulin release. There is no display screen on the patch; all interactions are made through the controller, which wirelessly transmits the commands to the patch pump.
Those are just the basics. As we go on, you will learn more about what pumps can do, how they work, and what other features pumps have.
Insulin pumps can be used to effectively manage your diabetes. They can help you achieve your blood glucose and A1C targets. They give you flexibility. Many people feel as if their quality of life has been enhanced by insulin pump therapy, and they feel like they are more in control. Let’s go over what else insulin pumps offer.
Multiple Basal Rates
Multiple basal rates can be used to avoid high and low glucose levels. Many people have specific patterns that can be addressed by changing their basal rates throughout the day and night. For example, if you have the dawn phenomenon (high blood glucose in the morning), then increasing the basal insulin rates at 3:00 A.M. may help you avoid it. If you go to the gym in the afternoon, basal rates can be decreased to avoid hypoglycemia. Adjustable rates can also be helpful if you have hypoglycemia unawareness (you don’t recognize the signs of low blood glucose), gastroparesis (a digestive disorder), or an unpredictable lifestyle.
Temporary Basal Rates
Pumps allow you to temporarily change basal insulin delivery. You can either increase or decrease it. This helps when you are ill (when you are not eating and are at risk for hypoglycemia), have high blood glucose from stress, have exercised more than usual, or are traveling across time zones. In addition, you can use temporary basal rates to help treat highs and lows as they occur.
Multiple Basal Patterns
You can have more than one 24-hour basal pattern from which to select. For example, when insulin sensitivity changes with menstruation (for women), you can program a separate 24-hour basal pattern that increases basal delivery all day long. You can have separate 24-hour basal patterns for weekdays and weekends (when you want to sleep in), for traveling, or for summer vacation.
Avoidance of Long-Acting and Intermediate-Acting Insulin
You use only rapid-acting insulin in the pump. If you use injections, you use long-acting or intermediate-acting insulin in addition to rapid-acting insulin. In an ideal world, long-acting insulin would be absorbed evenly over many hours, without any peak effect. Similarly, intermediate-acting insulin (or NPH insulin) has peaks that are supposed to be timed to meals. But neither of these insulins is completely predictably absorbed from one day to the next. This variation in insulin absorption may contribute to unexplained high and low glucose levels that can be seen with injection treatments; these fluctuations in blood glucose levels are less frequent with insulin pump therapy.
Precision in Insulin Delivery
Pumps deliver insulin with precision, particularly when compared with insulin injections. Insulin pumps can deliver very small amounts of insulin, as low as 0.025 unit. By contrast, the lowest a syringe can deliver accurately is 0.5 unit.
Dosing for Food Intake
Choosing the right dose of insulin for a meal is a huge challenge, particularly if you eat out a lot, like to snack, or aren’t sure what’s in your foods. With a pump, you can take multiple boluses by pressing a few buttons, in case you eat more than you planned. You can take one bolus to start with and then take another if you realize the portion you ate was more than you had intended. (Just be careful that you don’t take too many boluses.) An insulin pump also makes it much easier to take your dose before you begin to eat, which can be difficult when you are in public and have to give yourself a shot.
Bolus Calculators
Most insulin pumps have bolus calculators that help determine how much insulin is needed for food and for correcting hyperglycemia. By programming your insulin-to-carbohydrate ratio and correction factor (how much insulin you need to bring high glucose down to the intended range) into the pump, the bolus calculator will do the math and provide you with an estimate of how much insulin you need to give.
Dosing to Correct Hyperglycemia
Because the pump already has your programmed insulin correction factor, it is easier to take a bolus to correct a high glucose level. Once the glucose level is entered into the pump, the pump will calculate how much insulin is needed. With the push of a few buttons, treatment for hyperglycemia is on the way.
Weight Management
Some people can improve their weight, if they need to do so, with an insulin pump. This can occur if the person experiences less hypoglycemia and no longer needs to consume extra carbohydrate to treat it.
Child Safety Features
Many insulin pumps have features that protect children from accidentally delivering extra insulin or changing pump settings.
Summing Up the Advantages
You can eat when you want, be active when you choose, wake up when you want, take multiple boluses, have options for basal infusion rates, and get help with insulin dose calculations. This should lead to better diabetes control, more glucose levels within your target range with fewer highs and lows, better A1C, and a better journey with diabetes.
Even though there are many advantages to insulin pump therapy, there are some disadvantages. Understanding them is important, because deciding to go on insulin pump therapy should be a carefully considered decision.
Risk of Diabetic Ketoacidosis (DKA)
Because the pump only uses rapid-acting insulin, if there is an unexpected or accidental interruption of insulin delivery, there may not be enough insulin in the bloodstream to stop the liver from releasing glucose and producing ketones. This can rapidly progress to DKA, which is a serious medical condition. By closely monitoring glucose levels, checking for ketones, and dosing insulin to bring glucose and ketone levels down, DKA can be avoided. You can find out more about DKA in chapter 9.
Being Attached
Some people feel apprehensive about wearing an insulin pump all day, every day, and about being attached to a device, no matter how small it is. This was probably a bigger issue before we all became comfortable having cell phones with us 24/7. The insulin pump will be attached to you, and for some people that is a constant reminder that they have diabetes. Try to view the insulin pump as a key to good control and a healthy, more normal life.
Privacy
People can see your insulin pump, unless you conceal it. The pump will make it difficult to hide the fact that you have diabetes. If you are reluctant to let people know about your diabetes, then this is something to consider before starting insulin pump therapy.
Skin Issues
The infusion set and the tape can irritate the skin. To use a pump, you may have to try different combinations of tape and skin treatments until you find what works for you. If you use the same site for the infusion set repeatedly, you can get scar tissue and an increase in fatty tissue buildup (called lipohypertrophy).
Infusion Set Issues
The probability of your infusion set falling out or being jarred from the site can be minimized with good habits. Using appropriate taping techniques and changing your infusion set regularly can help avert problems. To be safe, you need to keep extra pump supplies with you at school or work, and have an insulin pen or syringe available so you never have to compromise your safety and health.
Missing Boluses
Some people forget to bolus with meals or to correct hyperglycemia. If you regularly miss or skip taking a bolus for food, then your A1C will increase. The good news is that many pumps have alarms that you can set to remind you to test or take a bolus at certain times; an example might be to set a bolus alarm to remind you at lunchtime to check your glucose and take your bolus insulin. You can also set the alarm on your phone or watch to remind you about boluses.
Weight Gain
Some people gain weight due to the ease of dosing insulin. But the pump doesn’t add excess calories to your meal plan—only you can do that. Remember your meal plan, and schedule a meeting with a registered dietitian if you’re having trouble following your healthy eating plan.
Cost
The insulin pump itself, plus the supplies (e.g., infusion sets, insulin reservoirs, tapes), have a cost. Most insurance companies cover insulin pump therapy, minus your deductible. It is important for you to find out what you will have to pay out of pocket for insulin pump therapy before you make the transition.
Summing Up the Disadvantages
These disadvantages usually become less significant as time passes and as you become more familiar with the pump. As your knowledge and experiences grow, you will be able to adapt to the pump and make it work for you. Insulin pumps can be a great tool for diabetes management and can mean better glucose control and fewer complications.
WHAT MAKES YOU A GOOD PUMP CANDIDATE?
Before anyone can take on an insulin pump, he or she needs to understand what the pump can do and how it works, be realistic about his or her capabilities, and know a good deal about diabetes management. Your diabetes team may be very enthusiastic about pump therapy for you, but are you ready for it? What do you need to do to be considered ready for an insulin pump?
• Realistic expectations. The pump is not an artificial pancreas. It doesn’t cure diabetes. It cannot correct anything on its own. This is true even if you have a sensor and use CGM. You must be committed to being very active in your diabetes—and pump—management. Successful management takes time, good habits, dedication, hard work, and commitment.
• No coercion. No one should be forced to get an insulin pump, including young children. Although a pump can motivate someone to participate in his or her diabetes management, this cannot be the primary reason to get a child or teen an insulin pump.
• Participation of others. No one can manage diabetes alone. Children, teens, and young adults need someone—a family member or a friend—who understands diabetes, insulin pumps, and diabetes emergencies.
• Sufficient diabetes knowledge. To succeed with pump therapy, it is important to understand the following concepts: basal/bolus therapy, your diabetes meal plan, carbohydrate counting, avoiding and treating hyperglycemia, and sick-day management. Gaining skills and knowledge should be your goal.
• Awareness of financial responsibilities. Find out exactly what your insurance will cover and what you will have to pay out of pocket. This is vital information.
• Sufficient glucose monitoring. The only way to effectively use an insulin pump is to check your glucose frequently and take action based on the glucose levels. Many health care providers and insurance carriers require proof of four or more glucose checks a day for at least 60 days before they will authorize you to get a pump. Without adequate glucose monitoring, pump therapy is less likely to be successful.
IF YOU’RE READY FOR AN INSULIN PUMP, HERE’S WHAT’S NEXT…
Your physician has to prescribe the insulin pump, and your insurance company will have to review and approve the claim. Your pump will be shipped to you or your health care professional. You will be given instructions on how to start learning about your new device.
If you are ready for an insulin pump and are confident that you meet the requirements listed above, then you’ll need to work with your diabetes team to determine which pump you should get.
Which Pump?
Different companies make different pumps. Although these different pumps are fundamentally similar, each individual pump has its own distinguishing features. Likewise, different pump manufacturers provide different services. Discuss the available options with your diabetes team, research them on the Internet, read the product brochures, talk to people who use pumps, and learn as much as possible. Decide what features or services are important to you. Once you have made your choice, work with your diabetes team, the insulin pump company, and a pump trainer to make your new journey successful and enjoyable.
When to Start Pump Therapy
There is no right or wrong time to start insulin pump therapy. It is becoming more common for people to begin pump therapy early in the course of their diabetes, while others wait for some time. Some decide to get an insulin pump only after they have had a problem, like severe hypoglycemia, or a complication. Sometimes the diabetes team is pushing for pump therapy; other times, team members are reluctant. Some health care providers are more willing to use pumps, and others have very strict criteria for who they think is a good candidate.
At the present time, pump therapy is usually considered to be the next step after MDI. If your diabetes center uses MDI at the time of the diagnosis of diabetes, it might only take weeks or months to switch to a pump. If your diabetes center starts people on one to three shots per day in a fixed regimen, then you likely have to go to MDI and then to a pump. This could take months or years.
Is there an advantage to starting insulin pump therapy earlier rather than later? Perhaps, but we don’t really know for sure. However, studies are underway to determine if more intensive management at diagnosis is beneficial.
Pump Training
Before you have your in-person pump training, do some research. Most companies have some easy online learning that will help you become familiar with how your pump operates. Your pump trainer will be certified in all of the features of your insulin pump and will verify that you know how to operate it. You will go through all the steps of setting up the pump, filling the reservoir, priming and inserting your infusion set, and practicing as many times as you need until you are comfortable and confident with the pump. There are online tools, instructional videos, and booklets to give you further guidance after training.
Data Management with Computer Programs
You can upload the information stored in your insulin pump to a computer program, which is either supplied by the manufacturer of your pump or available from another company. The program will allow you to store and upload information, such as number of insulin doses delivered, pump settings, glucose values, carbohydrates consumed, infusion set changes, pump suspends, and more. These data management programs then display data in pie charts, tables, graphs, and percentages above and below target range. The ability to transfer this data and analyze it with the software can help you improve your diabetes care by making it easier to detect trends and patterns that may require attention.
CHAPTER REVIEW
• An insulin pump is a small machine that continuously delivers insulin.
Pumps come in two varieties: durable and patch.
• There are many advantages to insulin pump therapy. The advantages of delivering basal insulin with a pump include multiple basal rates, temporary basal rates, multiple basal patterns, and precise insulin delivery. Boluses can be given to cover food, to correct an elevated glucose level, or both. This gives you flexibility.
• The disadvantages include the risk of DKA, the issues of being attached to a device that reminds you about diabetes and might be visible to others, issues with your skin and with infusion sets, missed boluses because diabetes management becomes more automatic, and cost.
• Pump users should have these qualities: realistic expectations, ability to participate with others in their diabetes care, sufficient diabetes knowledge, willingness to monitor glucose effectively, desire to use an insulin pump, and an understanding of the costs of the device.
• You need to decide which pump to use, and getting properly trained is critical.
SECTION 2: THE NITTY-GRITTY
CHAPTER 3 HOW DOES MY PUMP WORK?
IN THIS CHAPTER
• Uploading and Record Keeping
• Patch Pumps and Pumps in the Future
Although it’s only about the size of a deck of cards, an insulin pump is an impressive, complicated device that contains many components and can perform many different functions. There are two kinds of pumps: durable and patch.
Durable pumps are designed to last many years. They are made of a hard plastic case with buttons, a front screen, a battery compartment with a screw on top, and a space for the reservoir that will be filled with insulin. Clips can be attached to the outer surface so you can place the pump on a belt or waistband. There is a sticker on the pump that has some useful information: the serial number, model and type, company phone numbers, and other general information. At the base of the reservoir shaft is a computer-controlled mechanical plunger that can deliver incredibly small amounts of insulin.
Patch pumps are worn directly on the body. The pod component attaches to the body and has the insulin reservoir and motor inside. It is controlled by a separate controller or personal digital assistant (PDA).
Reservoir
The reservoir comes empty. There is a needle attachment that is used to draw insulin from the insulin vial into the reservoir. The needle is detached once the correct amount of insulin is drawn up; the correct amount depends on how much insulin you use in two or three days. The whole reservoir is screw-turned tightly into the chamber in the pump, and the tubing leads away to the infusion set, which is attached to the body. With a patch pump, the reservoir is contained within the pod, which adheres to the skin.
Screen
The pump has a front screen (the patch pump has the screen on the controller). When not in use, front screens generally display the time (some have the date), insulin remaining, and information about battery life. By pushing different buttons on the face of the pump, you can access different functions in the pump’s software. The software lets you deliver insulin; set or edit basal rates; set or edit the pump calculator; suspend insulin delivery; review your bolus, basal, and alarm histories; and see the exact amount of insulin remaining in the reservoir.
Software
The software not only lets you know the date and time, it also allows your pump to store tons of information, including weeks’ or months’ worth of bolus and alarm histories, blood glucose readings, and basal rates. The software allows the pump to consistently deliver the correct amount of basal insulin. It can also calculate the appropriate amount of insulin needed based on a glucose reading and a carb count entered into the system. Some pumps have a large database of food and carb counts. There are also safety features that prevent the user from providing too much or too little insulin in boluses or for the basal rate. Software also allows you to determine how you want to deliver a bolus every time you deliver one.
Pump History and Downloading
The information stored in the pump can be uploaded to a computer and analyzed by software. Generally the pump connects to the computer using a cable or wireless connection, and once the information is transferred from the pump to a computer, the user can look at graphs, pie charts, lists, and other visual information. Many diabetes care providers download information from the pump during clinic visits, or they may ask you to download it at home and bring a printed copy to your appointment. Between visits, you should look at this information and send it to your diabetes team if you need help troubleshooting some problems.
Blood and Interstitial Glucose Monitoring
Most pumps can connect to a blood glucose meter. In addition, it is possible for some of them to connect wirelessly to a continuous glucose monitor (CGM). This means that the glucose meter and sensor can transmit glucose values directly to the pump’s screen and memory.
Insulin Delivery
Pumps deliver basal and bolus rates of insulin. Basal rates are set by the user, with guidance from the diabetes team. Based on individual dosing, mealtime and correction boluses are given.
Suspend
All pumps have the ability to be suspended so that no insulin (basal or bolus) can be administered. A pump can remain suspended indefinitely but will sound an alarm every so often to remind you that you are not receiving insulin. With most pumps, it is easy to suspend insulin delivery in case you have an emergency.
Alarms
Pumps have alarms. Some are functionally important, such as “low battery” or “no delivery” (called an “occlusion” alarm in some pumps). There are alarms that you can set to remind you to test, take insulin, or check for ketones if your glucose is over a certain amount. If you need to, you can review the last 50 or so alarms. Pumps have different options for the way they notify you, such as various beeps or sounds or with vibration. Most pumps will beep or vibrate when a bolus is complete, when you are currently using a temporary basal rate, or when you have a low reservoir or low battery.
Active Insulin or Insulin on Board
After a bolus is given, insulin continues to affect your glucose level for some time. The amount of insulin left in your bloodstream is referred to as “active insulin” or “insulin on board.” You can set how long you want the pump to track active insulin, but discuss with your health care team how long you should have the pump track it. Generally, people set the active insulin time to two to five hours (most often, three). The pump calculator keeps track of the amount of insulin that is still active from previous boluses so you do not have boluses overlapping each other and dropping your glucose levels (this is referred to as “insulin stacking”).
Maximal Bolus and Basal Rates
You set a maximal rate for both basal and bolus insulin delivery to enhance safety. This prohibits you from accidently taking 20.0 units instead of 2.0, for example.
Pump Bolus Calculators Make Pumps Smart
The pump bolus calculator—which makes pumps smart—calculates how much insulin to give for boluses. It takes into account your insulin-to-carbohydrate ratio (ICR), the insulin sensitivity factor (ISF), the duration of active insulin, and your target glucose range. These values (except active insulin) can be altered by time of day, for example, because your insulin sensitivity and your ICR change over the course of 24 hours. When you first get your pump, your diabetes care team will help you determine these settings. They can be changed at any time (preferably in consultation with your diabetes team) as indicated by the patterns in your glucose control.
To determine the amount of insulin you take for a food bolus, you enter the number of grams of carbohydrate you plan to ingest and your current blood glucose level. Then the pump calculator will determine how much insulin you should take. If your blood glucose is above or below your target range, the bolus calculator will also figure out if you need to add or subtract insulin from the food dose.
However, you can always alter the insulin bolus dose suggested by the pump bolus calculator, giving yourself less or more insulin depending on any number of factors. If you are about to exercise or are not sure you will eat an entire meal, you might want to decrease your bolus from what the calculator suggests. If you have ketones or are sick, you might want to take more. Although it is convenient to have the pump calculator so you don’t have to do the calculations yourself, it is important to think before you push the button.
Here’s an example. If your blood glucose is 250 mg/dL and you are about to eat 15 grams of carbohydrate for lunch, you would enter those numbers into your bolus calculator (or the blood glucose would be automatically sent from your meter). The calculator suggests an amount of insulin to bring your glucose into your target range and cover your meal. Some pumps will show you the two different amounts, one for food and one for correction, and others will simply lump them together into one suggested bolus without showing a breakdown.
Keeping detailed records of your blood glucose levels, doses of insulin, food intake, and other events (such as exercise, illness, or stress) is important. It is also hard to keep a logbook or a record of all that you do every day. However, when this information is available for review, you are able to spot patterns and trends that may be problematic. In contrast, if you are looking only at your current glucose level, you won’t detect these patterns, even if you correct your high glucose nearly every morning and treat a low every afternoon.
By uploading data from your pump to the software, especially when it also includes information from your glucose meter (and a CGM, if you have one), you are able to review up to three months of data. Because the bolus calculator captures the carbohydrate history for meals and breaks out the bolus details so you can see when correction doses were administered, you have the ability to look for trends and patterns. By reviewing these data, you can identify what the problems are, why they are occurring, and how they can be fixed.
A Diabetes Meeting
The purpose of a diabetes meeting is to sit down with your diabetes team and review your glucose trends and patterns, your pump (and CGM) settings, and how you are doing with your diabetes regimen. The frequency should be weekly, or less often if there are no issues with your diabetes. The purpose of a diabetes meeting is to identify patterns and trends in your glucose levels, alterations that need to be made in your pump (and CGM) settings, or behaviors that you are looking to improve, such as remembering to bolus, measuring blood glucose levels, using the bolus calculator, and changing infusion sets at least every three days, and more. Set goals, monitor your progress over time, and reward yourself for achieving your goals. After you review your information, discuss it with someone—a friend, spouse, child, parent—and, if needed, with your health care team.
Interpreting Data
There are several ways to look at your pump or meter data. These include a logbook, trend graphs, pie charts, and data tables. The logbook is just a digital version of a handwritten log. Trend graphs, pie charts, and data tables are visual representations of the logbook information that make it easier to spot patterns and trends. The trend graphs and pie charts are colorful visual representations of your glucose numbers, averages, and high/low patterns, whereas the data table contains just numbers and values. Each method of displaying your information can be reviewed to identify specific problems or times of good control.
Logbooks
Logbooks, like the paper ones you were first given when you were diagnosed, are grids containing all of the pertinent information that affects your diabetes. They are either very detailed or they can just display your glucose values at certain times of day (before or after meals).
Trend Graphs
A trend graph is often the first thing that your diabetes team will look at because they easily show many days of data laid over each other. A trend graph has your blood glucose values along the vertical axis and the time of day along the horizontal axis. The horizontal axis generally shows 24 hours and can start at either 5:00 A.M. or midnight, depending on which pump, CGM, or meter you use. Customizable target ranges can be set and are shown as a shaded horizontal bar through the whole graph. Multiple days are represented on the graph as different colored lines with small symbols at each blood glucose value. On a CGM graph, the colored lines are more fluid, with no individual symbols because there are many, many more data points. There is usually also a dotted line that runs through the graph as an average of all the days’ values.
Trend graphs make it easy to spot repeating patterns. Trend graphs are also helpful because you can see your highest and lowest values on the graph, and with the adjustable target range you can also see how often your values swing outside this range.
The graph generated by CGM shows a spike of numbers beginning around 4:00 A.M. This graph offers a good visualization of the dawn phenomenon (it is circled in the graph below). The dawn phenomenon occurs when certain hormone levels, such as cortisol and growth hormone, spike in the early morning hours, resulting in increased blood glucose levels, which in turn requires a higher insulin dosage. Looking at this graph will help you identify the dawn phenomenon and allow you to treat it by increasing your early morning basal rate.
Pie Charts
Pie charts show the averages for the numbers in your target range, above it, and below it. Each pie chart represents a different time of day (e.g., before and after breakfast) or a specific day. Generally, each section is a different color, making it easy to see that a majority of your values are in a certain range. Ideally, you should aim for as much time in the target range as possible, but many people have difficulty achieving more than 50–60% of the time in that range. Similarly, you should aim for as little time in the hypoglycemia range as is possible. Many people have difficulty achieving less than 11% of their values as lows.
Although pie charts identify times when there are too many values in the high or low range, they don’t show you the most extreme values. Neither do they show you the standard deviation (covered in this chapter).
Data Tables
These are grids of numbers representing everything, including highest and lowest numbers, standard deviation, averages, number of times glucose testing was performed, frequency of infusion set changes, and percentage above and below target during the days you’ve selected for review. These types of tables work better with more data points and therefore are good when CGM is used.
Average Numbers
Average numbers are used to determine glucose levels during specific times of day, such as when you first wake up or when you go to sleep. Averages don’t show the highest or lowest numbers (for example, after lunch for the past two weeks).
Standard Deviation
The standard deviation assesses how frequently you go above or below your target range. The standard deviation is the amount, on average, that you swing above or below your target. If your standard deviation number is 35, then that is the average of your high and low numbers and you swing 35 mg/dL above target and 35 mg/dL below target. Optimally, standard deviation numbers should be less than 55 mg/dL or less than half of your average glucose level. For example, if your average glucose is 156, your standard deviation should be less than 78. The purpose of the standard deviation is to give you an idea of the variability within your blood glucose numbers. It is not beneficial to have a high degree of glucose variability.
Percent (%) High, Low, and in Range
The data sheet also shows the percentage (%) of glucose values in the high, low, and target range, just like the pie charts, but these are numerical values rather than graphic representations. These data can be used like the pie charts, and target ranges can be customized for each individual.
At Your Diabetes Appointment
