An Expert Opinion on Advanced Insulin Pump Use in Youth with Type 1 Diabetes

Abstract

Among children and adolescents with type 1 diabetes mellitus, the use of insulin pump therapy has increased since its introduction in the early 1980s. Optimal management of type 1 diabetes mellitus depends on sufficient understanding by patients, their families, and healthcare providers on how to use pump technology. The goal for the use of insulin pump therapy should be to advance proficiency over time from the basics taught at the initiation of pump therapy to utilizing advanced settings to obtain optimal glycemic control. However, this goal is often not met, and appropriate understanding of the full features of pump technology can be lacking. The objective of this review is to provide an expert perspective on the advanced features and use of insulin pump therapy, including practical guidelines for the successful use of insulin pump technology, and other considerations specific to patients and healthcare providers.

Expert Recommendations

Expert recommendations for the use of and reasons patients choose insulin pump therapy vary from reducing the risk of hypoglycemia to improving overall glycemic control, as well as having the freedom to eat and exercise as desired to suspending insulin delivery when needed to avoid hypoglycemia. Insulin pumps provide many options for optimal management of blood glucose control. These options range from the basic delivery of an insulin basal rate and bolus for food to more advanced settings that include temporary basal rates to decrease hypoglycemia with exercise and dual-wave boluses to cover high-fat meals. The goal for the use of insulin pump therapy should be to advance proficiency from the basic instructions during the initiation of pump therapy to utilizing advanced settings to obtain optimal glycemic control.

After insulin pump therapy is initiated, successful management of type 1 diabetes mellitus (T1DM) depends on an ongoing understanding of how to use pump technology by the patient, the patient's family, and professional support team.^1

–4 This article addresses the guidance recommended after the introduction period to insulin pump therapy. The focus encompasses appropriate pump settings and adjustments of the bolus and basal rate parameters as well as the advanced settings and therapy options available to the insulin pump user. Four points of discussion include insulin delivery options, insulin delivery to cover nutrition and hyperglycemia, evaluation of glucose management, and additional considerations.

Basics of Pump Therapy: Bolus Parameters and Basal Rates

Basic guidelines for initiating insulin pump therapy and adjusting the insulin pump are presented in Table 1.

Table 1.

Basic Guidelines for Initiating and Adjusting an Insulin Pump

Initial pump settings
Preparation
Key concepts	• Pumps use only rapid-acting insulin for basal and bolus needs.
	• Eliminate as much intermediate/long-acting insulin as possible before pump use.
Guidelines	• Stop intermediate-acting insulin 12 h and long-acting insulin 24 h before pump use.
	• Inject small amounts of rapid-acting insulin every 3–4 h as needed until pump use.
	• If intermediate/long-acting insulin is not eliminated, program a temporary basal rate for a reduced basal amount (50%–90% less than calculated starting amount) for the first 12–24 h of pump use.
Starting doses
Key concepts	• Basal insulin is continuous insulin delivery by the pump.
	• Bolus insulin is “on-demand” insulin delivery by the patient to cover food intake or correct blood glucose levels.
Pump TDD
Key concept	• Reduce current TDD by 25%, calculate weight dose, and average the two doses.
Guidelines	• Calculate reduced dose: daily injection dose × 0.75.
	• Calculate weight dose: kilograms × 0.50 or pounds × 0.23.
	• Calculate pump TDD: (reduced dose+weight dose)/2 (or use lower of the two doses if hypoglycemia or impaired awareness of hypoglycemia is a concern).
Other recommendations	• Reduce daily injection dose (reduced dose) by <25% if current daily injection dose is >70% rapid-acting insulin.
	• Pediatric patients with good control on injections may require as little as a 5% reduction for the reduced dose.
	• The TDD is variable for children and teens and may require as much as 1.0 U/kg to calculate weight dose.
	• If hypoglycemia or impaired awareness of hypoglycemia is a concern, use the lower of the two doses.
	• In the cases of persistent hyperglycemia, elevated hemoglobin A_1c, or pregnancy, use the higher of the two doses.
	• If glucose control is erratic or if the patient is starting on pump therapy from diagnosis or from oral medications, use the weight dose.
Total daily basal and bolus doses
Key concepts	• Initiate pump use with a single basal rate to be delivered evenly each hour, 24 h per day.
	• Determine what % of the pump TDD will be basal, and subtract the total daily basal dose to determine the total daily bolus dose.
Guidelines	• Calculate total daily basal dose: pump TDD × 40%–50%.
	• Calculate total daily bolus dose: pump TDD − total daily basal dose.
	• Calculate basal rate: total daily basal dose/24 h.
Other recommendations: Clinical guidelines for total daily basal and bolus percentages	• Adults: basal 40%–50%, bolus 50%–60%
	• Puberty to adult: basal 30%–40%, bolus 60%–70%
	• Prepuberty to puberty: basal 20%–40%, bolus 60%–80%
ICR
Key concepts	• The ICR is the amount of carbohydrate in grams that 1 U of insulin covers.
	• The ICR is used to calculate bolus doses to cover food intake.
Guidelines	• Calculate ICR by method 1 (estimated daily carbohydrate intake): grams of carbohydrate/total daily bolus.
	• Or calculate ICR by method 2 (450 rule): 450/pump TDD.
Other recommendations	• If an established ICR on multiple daily doses provides reasonable after-meal control, use that ICR.
	• Patients may require more than one ICR to obtain optimal after-meal control.
	• Different ICRs can be programmed into the pump for different times of the day such as for breakfast, lunch, dinner, or snacks.
ISF
Key concept	• The ISF is the drop in blood glucose in mg/dL per 1 U of insulin.
Guidelines	• Calculate ISF by method 1 (1700 rule): 1700/pump TDD.
	• Or calculate ISF by method 2 (2000 rule): 2000/pump TDD.
	• Calculate the correction dose: (current blood glucose − target blood glucose)/ISF.
Other recommendations	• If an established ISF on multiple daily doses provides reasonable correction doses, use that ISF.
	• If hypoglycemia or impaired awareness of hypoglycemia is a concern, use the 2000 rule.
Programming the pump
Key concept	• For some pumps, the above calculated values can be programmed into the pump. Then the patient can enter the current blood glucose and the amount of carbohydrate planned to be eaten into the pump, and the pump will calculate the insulin bolus dose for the patient.
Adjusting pump settings
Basal adjustments
Key concepts	• Correct basal rates should allow for variations in eating and sleeping patterns without the patient experiencing glycemic excursions.
	• Blood glucose should remain within target (does not rise or fall >30 mg/dL) through the night.
Guidelines: overnight basal	• If blood glucose rises or falls >30 mg/dL, adjust rate by 10%–20% 2 to 3 h before rise or fall, based on blood glucose data.
	• If blood glucose drops below 70 mg/dL, treat the low-blood glucose level and decrease by rate 10%–20%.
Guidelines: daytime basal (fasting and nonfasting)
Fasting	• Blood glucose should remain stable (does not rise or fall >30 mg/dL) during skipped meal time.
	• If blood glucose rises or falls >30 mg/dL, adjust rate by 10%–20% 2 to 3 h before rise or fall.
	• If blood glucose drops below 70 mg/dL, treat the low-blood glucose level and decrease rate by 10%–20%.
Nonfasting	• After-meal blood glucose values should steadily decline and return to premeal target range by next meal.
	• If blood glucose falls >60 mg/dL or drops below target, lower the rate by 10%–20%.
	• If blood glucose rises, stays the same, or decreases <30 mg/dL, increase rate by 10%–20%.
Bolus adjustments
Guidelines: ICR	• Two-hour after-meal blood glucose should be 30–60 mg/dL higher than premeal blood glucose.
	• If 2-h after-meal blood glucose increases >60 mg/dL from the premeal value, decrease ICR by 10%–20%. For example, take the ICR from 1:10 to 1:9.
	• If 2-h after-meal blood glucose increases <30 mg/dL from the premeal value, increase ICR by 10%–20%.
Guidelines: ISF	• After correction, 2-h blood glucose should be halfway to target and 4-h blood glucose should be at target.
	• After correction, if 2-h blood glucose is not halfway to target and 4-h blood glucose is not at target, adjust ISF by 10%–20% as needed.
Other recommendations	• Adjusting insulin is an ongoing process.
	• First adjust basal rates (especially overnight).
	• Make only one or two changes at a time.
	• Reevaluate blood glucose 3–7 days after adjustment.
	• Basal rate adjustments should be programmed to begin 2–3 h before the blood glucose rise or fall.
	• For ICRs and ISFs, increase the ratio to decrease the bolus amounts.
	• For ICRs and ISFs, decrease the ratio to increase the bolus amounts.

Data were derived from Medtronic Pumping Protocol.⁵⁰

ICR, insulin-to-carbohydrate ratio; ISF, insulin sensitivity factor; TDD, total daily dose.

Insulin-to-carbohydrate ratio

Meal-dose insulin is best calculated using an insulin-to-carbohydrate ratio (ICR) that is determined for every meal based on the carbohydrates to be consumed. The initial ICR for pump use can be calculated from the prior effective ICR used for multiple daily injections, or the ICR can be estimated using the 450 rule in which 450 is divided by the total daily dose to give the starting ICR. The pump support team along with the patient must validate the correct ICR at each meal by measuring the glucose before and 2 h after the meal. Ideally, after the meal, the rise in blood glucose should not exceed 30 to 60 mg/dL, or the actual blood glucose reading should not exceed 150 to 180 mg/dL. The ICR may differ at breakfast and other meals on the basis of insulin sensitivity during those times of the day.⁵ At breakfast, the ICR may be lower, meaning more insulin is needed for each gram of carbohydrate at breakfast than at other meals. Most insulin pumps can be programmed to deliver differing ICR rates at varying times of the day.

Correction factor

The correction factor, also known as the insulin sensitivity factor (ISF), is the amount that blood glucose levels will fall with 1 unit of rapid-acting insulin based on a set target glucose level, which typically is 100 mg/dL, but could be higher or lower based on the individual patient's target glucose level. For adults, the ISF can be estimated by dividing 1700 by the total daily insulin dose, and for children, the ISF can be estimated by dividing 2000 by the total daily insulin dose. As with the ICR, the ISF may differ at breakfast than at other meals because of insulin sensitivity during those times of the day. To validate the ISF, a high glucose value without eating can be corrected using this ISF. If the blood glucose level is within 20% of the target level, the ISF is correct. If the fall in glucose is 20% above the target, one would decrease the ISF by 20%, and if the fall in glucose is 20% below the target, one would increase the ISF by 20%.

Most insulin pumps are equipped with software to assist with calculations of insulin dose.^6
–8 Once programmed with the patient's ICR, ISF, glucose level target, and active insulin time, the pump software determines how much insulin to administer for an insulin bolus. The pump bolus calculator accounts for the insulin that is currently available from any previous dose by programming the time a bolus of insulin typically lasts, which generally is 2 to 5 h (the insulin on-board or active insulin time).⁹ The patient enters the number of grams of carbohydrate planned for consumption in the meal and the current self-monitored blood glucose (SMBG) value. The pump will suggest the amount of total insulin that should be administered before the meal. The patient should determine how this dose should be modified before delivery on the basis of other factors, including recent or planned activity, intake of high-fat food, stress, and illness.

Basal Rates

The basal rate is determined by how much insulin is needed when the patient is not eating. Typically, the total basal rate is 40% to 50% of the total daily insulin dose with the total daily dose at insulin initiation estimated at 0.5 times body weight in kilograms. On average, youth before puberty and adults will need 0.6 to 0.7 unit per kilogram per day, and adolescents will need 0.8 to 1.0 unit per kilogram per day. The basal rate often needs to be reduced for nighttime in young children and some adults and increased in people with an increased insulin need in the dawn hours from 4 to 8 am.

Adjusting basal rates

In general, the basal rate is correct if the blood glucose does not vary by >20% when one is not eating for 4 or more hours; however, there are many variables that can affect basal rates, including high-fat meals, exercise, illness, poor sleep, and stress. Following trends in blood glucose by frequent SMBG or continuous glucose monitoring (CGM; see section below) when not eating and adjusting the basal rate accordingly, by 10% to 20%, is a conservative approach. A more straightforward approach is adjusting basal rates according to basal-rate checks. Ideally, the patient should have blocks of time without excessive activity, such as avoiding moderate exercise for at least 8 h before the check, and with no carbohydrate intake for 4 h. This can be accomplished by assessing different basal rates on different days to fine-tune basal insulin needs. Here are a few recommendations for basal-rate checks:

• After each check, basal rates should be adjusted slowly and in small increments over time to avoid hypoglycemia. Insulin pumps currently available deliver basal rates in increments as low as 0.01 unit/h. Basal rates should be conservatively changed by 10% to 20% (generally 0.01 to 0.05 U/h for younger children and 0.1 to 0.2 U/h for adolescents). After the change, there should be a waiting period of 3 to 6 days to acclimate to the new rate, unless hypoglycemic events require more frequent changes.

• Aim to check routine blood glucose.

• Wait at least 4 h after the last insulin bolus and last carbohydrate intake before checking blood glucose. (This would be the baseline value.)

• Subsequently check blood glucose frequently (every 1–2 h) by SMBG or CGM.

• If blood glucose increases or decreases >30–40 mg/dL during the check, discontinue the check and adjust the basal rate accordingly by 10% to 20%.

Temporary basal rate

The ability to temporarily increase, decrease, or suspend insulin delivery is a notable advantage of insulin pump therapy over conventional insulin therapy with multiple daily injections.¹⁰ A temporary basal rate is set for a defined period of time in half-hour increments up to 24 h, either as a percentage (e.g., 50% of the usual basal rate [if the usual basal rate is 1.0, then the patient may decrease the rate to 0.5 for a set time period]) or as a discrete delivery increment in units per hour (e.g., if the usual basal rate is 1.0 U/h, then the patient may increase the rate to 1.4 U/h). This feature is particularly helpful for short periods during exercise and for extended periods of up to 8 h after intense activity of 2 or more hours, while glycogen stores are being replenished. Healthcare providers should strongly encourage use of this feature. Unexpected changes in schedule or level of physical activity may increase the risk of hypoglycemia. Furthermore, most patients' sensitivity to insulin and, therefore, their needs for insulin change throughout the day. In response to these changes, insulin delivery by the pump can be reduced or suspended temporarily. For example, if exercise is planned for 1 h, the basal rate can be reduced (i.e., 50% of the usual rate) or suspended. If exercise extends beyond 1 h, the temporary basal rate or suspension also could be extended. Conversely, if more insulin is needed during illness or a sick day, the basal rate can be temporarily increased.

In addition to periods of exercise and illness, other times to consider temporary basal rates include scheduled surgical procedures; persistent or refractory hypoglycemia, particularly hypoglycemia during the night; schedule changes on weekends or days away from work; long travel periods in which blood glucose tends to rise with inactivity; extended study sessions or testing periods in which stress can cause blood glucose levels to fall or rise; and the menstrual cycles of adolescent girls during which insulin requirements tend to vary. Some pumps allow for preset alternate basal programs for frequent needs to alter insulin delivery such as for weekends or nights following exercise when blood glucose levels are affected routinely.

Suspending basal rates

Suspending basal insulin may also be helpful during times of unusually rapid decreases in glucose and persistent hypoglycemia. It is not recommended to suspend or disconnect from the pump for more than an hour without checking blood glucose. Suspending basal rates when glucose is low does not treat hypoglycemia but decreases the duration and severity of the event.

Insulin bolus options

Pumps offer multiple insulin bolus options characterized by the amount of the total insulin bolus over varying lengths of time.¹¹ A regular bolus administers the insulin quickly, similar to an injection. A square-wave or extended bolus administers insulin more slowly over a specified time, such as 2 h.¹² An extended bolus may be preferred over a regular bolus for meals high in fat and/or protein (≥30% of the meal), such as a steak dinner, to cover the relatively gradual increase in blood glucose levels resulting from longer periods of digestion or during long periods of snacking, such as at social gatherings or sporting events. A dual-wave or combination-wave bolus is a combination of a regular bolus and an extended bolus. A dual-wave bolus may be preferred for meals high in carbohydrate and high in fat, such as Mexican, Chinese, or Italian foods. For a dual-wave bolus, the meal insulin dose generally is divided evenly between a regular bolus and an extended-wave bolus over 2 h. Different types of meals might be best covered by different distributions of the insulin boluses, which the patient or family will learn over time through experience.

Continuous Glucose Monitors

Integration of CGM^{13

–20} with pump therapy is an option.^4,21 CGM technology uses subcutaneous sensors that measure glucose levels in interstitial fluid every 1 to 5 min.^15,18,22 CGM supplements SMBG¹ and allows for more frequent insulin dose adjustment on the basis of sensor alerts that can be set for impending hypoglycemia or hyperglycemia. Although interstitial glucose levels and blood glucose levels correlate well, there can be a physiologic lag between them during periods of somewhat rapid glucose change. Depending on the rate of change in the blood glucose levels, CGM values usually are within 20% of blood glucose values obtained by SMBG. Therefore, CGM is recommended as a supplement to SMBG and not as a substitute.²³

Trend arrows

All CGM systems display trend arrows that indicate the rate and direction of change (rising or falling) in blood glucose.^24,25 Trend arrows indicate whether glucose levels are changing quickly (>2 mg/dL/min), changing moderately (1 to 2 mg/dL/min), or remaining stable (<1 mg/dL/min). Thus, the trend arrows along with the current glucose level and the predictive alerts indicate what action should be taken and thus may be used to adjust a patient's glucose management strategy (Table 2). For example, if the current blood glucose level and the trend arrows indicate that the blood glucose is likely to rise above the target range, administering a correction bolus of insulin or temporarily increasing the basal rate may be necessary to avoid high blood glucose. In this scenario before a meal, the meal dose may be increased by 20%. If the trend arrows indicate that the blood glucose is likely to fall, decreasing the meal dose by 10% to 20% and giving the meal dose during the meal instead of before the meal may be considered.

Table 2.

Continuous Glucose Monitoring Trend Arrows for Adjusting Insulin Dose

Trend arrow display	Glucose level indication	Actions to consider
1 upward arrow (↑)	Rising	• Confirm glucose level with SMBG.
		• If taking correction dose, add 5%–10%.
2 upward arrows (↑↑)	Rising quickly	• Confirm glucose level with SMBG.
		• If taking correction dose, add 10%–20%.
1 downward arrow (↓)	Falling	• Confirm glucose level with SMBG.
		• If taking correction dose, subtract 5%–10%.
		• Decrease or suspend insulin temporarily.
		• Consume carbohydrate.
2 downward arrows (↓↓)	Falling quickly	• Confirm glucose level with SMBG.
		• If taking correction dose, subtract 10%–20%.
		• Decrease or suspend insulin temporarily.
		• Consume carbohydrate.

Data were derived from the American Diabetes Association.⁵¹

SMBG, self-monitored blood glucose.

Alarms

Threshold and predictive alarms^4,18,26 can be programmed to signal actual or impending hyperglycemia, hypoglycemia, or rapidly changing glucose levels. These alarms can be especially helpful for the detection of hypoglycemia in the case of impaired awareness of hypoglycemia, a condition in which the symptoms of impending hypoglycemia are diminished.^27,28 The high-glucose threshold alarm and the low-glucose threshold alarm alert the patient when blood glucose reaches the upper or lower threshold blood glucose values, which the patient selects and programs into the CGM settings in the pump. When first using a CGM, it is recommended that the patient activate only the low-glucose threshold alarm, setting the threshold at a relatively low glucose value, to become acquainted with and gain experience in using the alarm.¹⁸ It is recommended for an alarm to be silenced after 15 to 30 min.²⁹ Later, the patient may set the low-glucose alarm at higher values to tighten glycemic control. With experience, the patient may then activate the high-glucose threshold alarm, beginning with a relatively high glucose value (e.g., 300 mg/dL) and later adjusting for tighter control. The duration of 15 to 30 min for alarms is also acceptable for high-glucose thresholds.

Predictive alarms should be programmed after the threshold alarms have been set optimally. Predictive high-glucose and predictive low-glucose alarms alert the patient before blood glucose reaches threshold levels, the timing of which is programmed by the patient. When first using the predictive alarms, it is recommended that the patient set the alarm at 10 min before threshold values are reached. After learning to respond to the alarm, the timing may be set to 15 or 20 min.

Rate-of-change alarms should be programmed after threshold and predictive alarms have been set optimally. Rate-of-change alarms alert the patient when blood glucose is rising or falling quickly. Rate-of-change alarms, when used successfully, can help the patient avoid hyperglycemia or hypoglycemia by allowing the patient time to take action. In the case of a missed insulin bolus, the rate-of-change alarm is likely to sound for a high rate of glucose increase; thus, the alarm may function as the equivalent of a missed-bolus alarm.

Other alarms include the low-battery alarm, the lost-sensor alarm that indicates that the CGM system has lost the signal from the insulin pump, and the weak-signal alarm that indicates that the signal from the insulin pump is not at full strength. CGM systems display graphs of glucose levels over time in comparison with the patient's target levels. With companion software, the patient and healthcare provider can review multiple days' worth of glucose information and make appropriate changes in their insulin delivery.

Suspending insulin delivery

The low-glucose suspend feature is an option in some CGM systems that are integrated with insulin pumps.^{3,4,26,30

–34} Insulin delivery is automatically suspended when a preset glycemic threshold is reached, which may reduce the risk of hypoglycemia when the patient is not aware of glucose trends.³⁴ The low-glucose suspend feature is not meant to prevent hypoglycemia but reduce the duration and severity of the event, which may be especially useful in the overnight period.

Optimization of Pump Settings

Evaluation of glucose management

Ongoing self-monitoring of blood glucose or use of CGM is necessary for effective and safe management of T1DM, allowing a patient to identify daily trends in hypoglycemia and hyperglycemia.^17,20,23,35 Understanding these trends can help the patient anticipate when glucose levels are likely to be too low or too high as a result of changes in diet and activity and give the patient the opportunity to plan for appropriate adjustments in insulin doses.

Although four to six SMBG measurements should be taken each day, one measurement before each meal and one measurement before bedtime,^1,20 additional SMBG measurements are required in most circumstances with pump therapy. By obtaining additional readings throughout the day, patterns in blood glucose will emerge, providing the patient with the ability to set appropriate basal rates and adjust the ICR or ISF.

Families of children with T1DM, who successfully help their children manage diabetes, also learn how to review blood glucose and CGM data as often as weekly and make adjustments as needed.¹⁷ A helpful strategy for families with adolescents with T1DM is to set a specific time to discuss blood glucose trends and adjustments. Having a set review time can alleviate the stress of parents “nagging” about blood glucose levels. Healthcare providers often encourage families to have reviewed the available information and suggest a course of action when calling or meeting with the diabetes team to foster independence with insulin adjustments; the family review can help work toward this goal. Pump therapy provides the ability to download and analyze information, including carbohydrate intake, insulin boluses for carbohydrates and corrections, basal rates, glucose data, and software-generated analyses, which help identify glycemic trends useful for insulin pump adjustment⁴ (Supplementary Figs. S1 and S2; Supplementary Data are available online at www.liebertpub.com/dia).

Use of data downloads

Insulin pump and CGM technology allow the patient to review data in multiple ways. Downloading data to available software allows the patient and healthcare professionals to review data such as how much basal, bolus (amount and number of boluses), and correction-dose insulin are used daily; how often patients are adding bolus insulin; how the bolus calculator is being used; how often the infusion sets are being changed; and CGM and blood glucose data¹⁷ (Supplementary Figs. S1–S3).

Keeping records of blood glucose over time will help patients recognize trends that will lead to improved glucose management.²³ The information may be downloaded either at the clinic or from home and brought to the clinic for regularly scheduled appointments with the professional diabetes team. Downloading data in between clinic visits to guide the adjustment of pump settings is highly recommended when starting pump therapy or when glucose values are not at goal. The professional team will help the patient review the information to identify areas for improvement.¹

Trend graphs and pie charts

Trend graphs include information on the average glucose values, as well as individual data. For example, lines may represent average glucose values for each day derived from CGM data, and dots may represent individual SMBG readings. These data are presented in the context of targets for glucose levels, which are adjustable according to the healthcare provider and the patient's needs. Trend graphs clearly show when glucose values have been higher than, lower than, or within the target values; thus, the graphs help the patient and professional team identify trends in blood glucose. For example, if the trend graph shows an increase in blood glucose every morning at 4:00 am, the patient likely is experiencing the dawn phenomenon, which occurs when an increase in hormones results in an increase in blood glucose. The dawn phenomenon often requires an increase in the early-morning basal insulin rate for 4 h starting 2 to 3 h before the rise in glucose.

Pie charts show the average of blood glucose values that have been higher than, lower than, or within target values for specific days or specific times during the day (Supplementary Fig. S3). Pie charts show in what glucose range the majority of blood glucose levels have fallen. For example, if 55% of a patient's blood glucose values were within range for a particular day, the majority of the pie chart (55%) would represent within-target values for that day. The goal is to keep as many glucose values within the target range and outside the low (hypoglycemia) and high (hyperglycemia) ranges as possible.

Standard deviation

The goal in diabetes management is to consistently maintain blood glucose within target values.³⁶ Standard deviation indicates how frequently blood glucose goes above or below the target range. A low standard deviation means that most of the numbers are very close to the average, and a high standard deviation means that the numbers vary greatly. Most device software will provide the standard deviation based on glucose input. The standard deviation should be either <55 or less than half the average glucose level. For example, if the average glucose level is 140 mg/dL, the standard deviation should be <70.

Insulin delivery to cover nutrition and hyperglycemia

As is the case with the initiation of pump therapy, the following factors continue to be very important in successful insulin adjustments¹:

• accurate carbohydrate counting^37

–40

• routine measurement of SMBG values

• consistency with timing of insulin delivery in relation to carbohydrate intake

• maintaining regular activity patterns

• maintaining consistent eating patterns

When one or more of these factors are not stable, it is difficult to adjust insulin to control glucose optimally.

Special Considerations

Exercise

The type, intensity, and duration of exercise can dramatically affect glucose levels and the sensitivity of the patient to insulin. Aerobic exercise (e.g., walking, running, cycling, and swimming) will cause the blood glucose levels to fall because of the utilization of ambient glucose and glucose stores in muscle glycogen and liver production of glucose for energy expenditure.²³ Anaerobic exercise (e.g., sprinting and weight lifting) can raise blood glucose levels because of the release of stress hormones such as epinephrine.²³ The longer the duration of exercise, the more energy expenditure and, thus, the greater need to replace glucose stores. On average, people need 30 to 60 g of carbohydrates for every 60 min of exercise to keep glucose levels stable and prevent ketosis.⁴¹

Basal insulin rates should be reduced or suspended and premeal boluses may need to be reduced depending on the intensity, duration, and timing of exercise.^23,41 The following are guidelines for making insulin adjustments with the goal of maintaining appropriate levels of active insulin and avoiding hypoglycemia:

• Obtain blood glucose readings before, during, and after exercise.

• Before exercise, ensure that blood glucose is within a safe range, ideally 100 to 180 mg/dL. If the glucose level is <100 mg/dL, consume carbohydrates (10 to 15 g) until it is >100 mg/dL.^41,42 If the glucose level is >180 mg/dL, take a conservative correction dose and delay exercise until the blood glucose is <180 mg/dL.

• For planned or unplanned exercise, the insulin dose may be reduced or suspended before, during, and after exercise according to the duration and intensity of activity²³ (Table 3). Consider starting to reduce the basal rate 30 to 60 min before exercise if glucose is in the low range (<100 mg/dL).^41,43,44

• If glucose levels tend to decrease while exercising, consider consuming 15 to 30 g of carbohydrate, preferably as liquids, for every 30 min of exercise to keep the glucose level between 100 and 180 mg/dL^25,42,45,46 or consider reducing the basal insulin rate by an additional 25% to 50% (thus delivering 50% to 75% of the regular basal insulin rate).^{23,41,43
–45}

• During exercise, check blood glucose every 30 to 60 min. SMBG and CGM results can help identify blood glucose level patterns in exercise to make insulin adjustments.

• The trend of glucose levels immediately before exercise may indicate how the glucose levels will respond during exercise.⁴⁷ For instance, if glucose levels are increasing immediately before exercise, they may continue to increase during exercise, possibly indicating too little insulin before exercise or a stress-related response because of the exercise.²³ If glucose levels are decreasing immediately before exercise, they may continue to decrease during exercise. Adjustments to basal rates may be made accordingly.

• Avoid suspending insulin delivery to zero for long periods of exercise (>1 to 2 h) because of the increase in glucose that occurs. Consider setting the temporary basal rate at 0% for a defined period of time (<2 h) or physically disconnecting from the pump. Using the temporary basal rate for a defined period without disconnecting from the pump will allow the pump to reactivate itself without the patient having to remember to do so. For those who exercise frequently and are accustomed to strenuous activity, moderate rather than drastic reductions in basal rates may be sufficient.

• After afternoon or evening workouts, consider temporarily reducing the basal insulin rate by 20% during the night until 3 am and checking blood glucose levels one or more times during the night to avoid hypoglycemia.^23,41,48 Exercise sensitizes the body's cells to insulin; thus, the body may metabolize insulin long after the exercise has been completed, and delayed hypoglycemia is possible.^23,49 Consumption of carbohydrates (1 g/kg) and protein (20 to 30 g) 1 to 2 h after exercise will restore glycogen stores and lessen the risk of hypoglycemia after exercise.⁴¹

• For long periods of strenuous exercise such as hiking, marathons, and other activities lasting ≥2 h, consider reducing the basal rate by 20% for 2 to 3 h immediately after exercise.^23,41,49

• For consistent exercise routines, consider setting an alternate basal rate pattern.

• Exercising outdoors on a hot day can damage the insulin; therefore, a backup insulin vial and pump supplies stored appropriately are recommended.

• Placing the pump site in a muscular area of the body, such as in the leg or arm, may increase the likelihood of hypoglycemia rather than placing the pump site in a more fatty area, such as the abdomen; insulin is absorbed more quickly in muscular areas.

Table 3.

Guidelines for Reducing Basal Insulin rates and Correction Doses for Exercise

Exercise intensity/duration	Characterized by/examples	Consider reducing basal rate or correction doses by
Reducing basal insulin rates according to exercise intensity
Mild	Easy breathing	5%–25% (deliver 75%–95% of regular basal rate)
Moderate	Sweat after 10 min, heavy breathing	25%–50%
Intense	Sweat soon after beginning, heavy breathing, unable to talk	50%–100% or disconnect (Check glucose often)
Reducing basal insulin rates according to exercise duration (using temporary basal insulin rates)
Long and strenuous or continuous	Distance running, backpacking, cross-country skiing	50% or adjust according to glucose values (check glucose often; continue consuming carbohydrate-rich snacks,^a sports drinks, and water; rates may need to be reduced by 20% after exercise)
Short intense workouts	High-intensity running	100% or disconnect
Adjusting correction doses when glucose levels are above target according to exercise intensity and duration
Mild/<30 min	100–180 mg/dL^b	50%–75%
	≥180 mg/dL^b	50%
Moderate/30–60 min	100–180 mg/dL^b	75%–100%
	≥180 mg/dL^b	50%–75%
Intense/≥60 min	100–180 mg/dL^b	85%–100%
	≥180 mg/dL^b	50%–85% (continue consuming carbohydrate-rich snacks,^a sports drinks, and water; rates may need to be reduced by 20% after exercise)

Data were derived from the American Diabetes Association.⁵²

Consume 15–30 g carbohydrate every 30 min.

Glucose level determined by SMBG (mg/dL).

Travel

To plan for safe travel with the insulin pump, frequent SMBG is essential, in addition to being prepared with extra pump sets, reservoirs, extra insulin, and food to treat glucose values. When traveling through airport security, the pump and CGM devices may be exposed to metal detectors; however, they should not be exposed to X-ray. Safety personnel may ask to see the devices to ensure they are for medical use.

Changing altitudes can create air bubbles; therefore, the pump tubing should be rechecked. For long trips, even long road trips, increasing basal rates may be necessary, because normal levels of activity are diminished. An increase of 10% to 20% is appropriate, depending on glucose values.

Pumps and school

For primary and secondary school students, the Diabetes Medical Management Plan outlines recommendations by the diabetes healthcare team for the student's healthcare and education plan. This document contains details about the student's diabetes management, including the pump, glucose meter, and CGM.

Students attending college will appreciate the flexibility of lifestyle that is possible with insulin pump therapy, which provides a means to effectively self-manage T1DM despite erratic schedules, irregular eating habits, and stress. Depending on the services available, the campus health services should become part of the patient's diabetes support network. The family should still have regular discussions about the patient's blood glucose levels and adjustments even while he or she is away at school.¹ The habit of this routine review will provide support away from home, lower the potential for feelings of isolation, and encourage good insulin management behaviors.

Conclusions

Advanced aspects of insulin pump therapy include the ability to use multiple bolus types dependent upon meal content; adjust or temporarily suspend basal insulin rates; use CGM in combination with the insulin pump; manage data; and adjust pump settings when exercising, traveling, and in school situations. Successful self-management of T1DM with insulin pump therapy depends on sufficient understanding of how to use pump technology, from basic instructions during the initiation phase to taking advantage of the advanced settings. Incorporating advanced therapy techniques can also provide insights into better glucose management through insulin pump use.

Footnotes

Acknowledgments

The authors thank Andrew Cagle (Lilly USA, LLC, Indianapolis, IN) for his critical review and Joseph Giaconia and Elizabeth Gardner (both INC Research, Raleigh, NC) for their writing and editorial support.

Funding source

Eli Lilly and Company and/or one of its wholly-owned subsidiaries.

Author Disclosure Statement

B.W.B. has received research support from Abbott, Animas, BI, DexCom, Janssen, Lexicon, Medtronic, Novo Nordisk, Sanofi, and Senseonics and consulting fees and speaker honoraria from Adocia, AstraZeneca, Insulet, Janssen, Medtronic, Merck, Novo Nordisk, Sanofi, and Valeritas. F.R.K. is an employee of and stockholder in Medtronic. N.V. is an employee of and stockholder in Eli Lilly and Company.

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