Insulin Pumps and Continuous Glucose Monitoring. Francine R. Kaufman

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