- Evidence-Based Practice Project: Intervention Presentation on Diabetes

DOI: 10.1177/1942602X18804491 For reprints and permission queries visit SAGE’s Web site, http://www.sagepub.com/journalsPermissions.nav.

© 2018 The Author(s)86 NASN School Nurse | March 2019

Diabetes/Endocrine

The hybrid closed-loop insulin delivery system, a form of “artificial pancreas,” is composed of an insulin pump, a standardized algorithm, and a continuous glucose monitor. The system streamlines insulin delivery by connecting continuous glucose monitor data with an insulin pump and an algorithm to drive basal insulin delivery. The hybrid closed-loop insulin delivery system, approved by the Food and Drug Administration in 2016 for children older than 7 years, is a major improvement in the management of type 1 diabetes. The purpose of this article is to educate school nurses about the components of the hybrid closed-loop insulin delivery system, the relevance to care, and the future direction of blood glucose management.

Keywords: artificial pancreas; hybrid closed-loop insulin delivery; diabetes; school nurse; children

T he hybrid closed-loop insulin delivery system is an emerging technology in diabetes management. Approved by

the U.S. Food and Drug Administration (FDA) in 2016, its use is growing for individuals with type 1 diabetes, including children older than 7 years old (FDA, 2018a). As use becomes more prevalent, it is important for school nurses to be able to confidently interact with the technology and provide care for school children who have this system. The purpose of this article is to inform school nurses about the components and

operating modes of the hybrid closed- loop insulin delivery system, the relevance to care, and the future direction of blood glucose management.

What Is the Hybrid Closed-Loop Insulin Delivery System?

Introduced in the United States in 2016, school nurses are now seeing children with type 1 diabetes using the hybrid closed-loop insulin delivery system. This system is commonly used by individuals who have trouble controlling their blood glucose and are interested in reducing the number of daily needle sticks associated with using insulin syringes or insulin pens.

Only one hybrid closed-loop insulin delivery system has been approved by the FDA and it is the MiniMed 670 by Medtronic. Closed-loop refers to the communication between insulin pump and continuous glucose monitor (CGM) that allows the insulin pump to titrate the basal insulin level to maintain the appropriate blood glucose level (Turksoy et al., 2017). The FDA has not yet approved a truly closed-loop system although there are systems currently in development (El-Khatib et al., 2016; Treviss, Simpson, & Wood, 2016). These new systems will have different and unique characteristics that will require the school nurse to learn more about them after FDA approval.

How Does the System Work?

The system requires several durable and nondurable pieces of equipment for use and replacement of system components. An insulin pump is

required, and for the pump to work, there needs to be insulin, an insulin infusion set, and a site where the infusion set can attach. The site consists of a subcutaneous catheter which can attach to and detach from the infusion set and is attached in place on the child with a durable sticker.

The insulin pump is similar to the insulin pump devices that have been used by diabetics for years, with some significant additional features. It provides a basal dose and has a program to calculate and deliver a one-time bolus of insulin (called the “bolus wizard”) (Medtronic, 2016).

The way in which the basal rate is calculated has changed. Traditional insulin pumps have a basal rate adjusted by the user’s care team, whereas this new system communicates with CGM to adjust the user’s basal insulin rate every 5 minutes in response to their interstitial glucose level. All user input is entered on the screen of the insulin pump. The screen also allows the user to see their glucose levels which are received from the CGM (Medtronic, 2018).

The CGM consists of a wire for blood glucose testing attached to a transmitter (FDA, 2018b). The CGM provides the glucose levels to the pump, where insulin is delivered based on the information received (FDA, 2018b).

The algorithm receives input from CGM, interprets it, and creates output in the form of a customized basal insulin delivery rate. The goal glucose level is 120 mg/dL for the user but can be temporarily altered to 150 mg/dL (Medtronic, 2016).

804491NASXXX10.1177/1942602X18804491NASN School NurseNASN School Nurse research-article2018

The Artificial Pancreas What School Nurses Need to Know

Jennifer Latham, MSN, RN

March 2019 | NASN School Nurse 87

How Does the System Operate?. School nurses need to know the basics about the artificial pancreas. Nurses need to know what mode it is operating in and how to assess a blood glucose level.

What Mode Is in Operation?. The nurse should first determine what mode is in operation. The pump can operate in “manual” or “auto” mode. Manual mode may look and act differently depending on whether the user is using CGM.

•• Auto Mode operates autonomously of the user apart from calibrations and prandial insulin boluses. When a pump is set to Auto Mode, it uses the input from the CGM to titrate the basal insulin rate up and down (FDA, 2018b; Medtronic, 2018). CGM data are displayed on the insulin pump screen (Medtronic, 2018). The most significant difference with Auto Mode is that the pump can initiate and cease administration of basal insulin and change the dose (FDA, 2018b). To remain in Auto Mode, the user must calibrate when prompted (Medtronic, 2018). Auto Mode can be identified by the presence of a blue shield in the background of the home screen on the insulin pump (Medtronic, 2016).

•• Manual Mode with CGM will no longer titrate the basal insulin based on CGM data, but it maintains one of the most important features of Auto Mode, low glucose insulin suspend (FDA, 2018b). If the user is trending toward a low glucose level, the pump will suspend insulin delivery. The glucose level is still displayed on the screen of the insulin pump, but will not have a blue shield in the background. The basal insulin rate will revert to a rate preprogrammed by the user’s care team.

•• Manual Mode without CGM will not be able to suspend insulin delivery based on predictive glucose values from CGM (Medtronic, 2018). This mode is similar to a traditional insulin pump, with the sole function of delivering the insulin it is programmed to deliver. The fallback basal rate will be used and the bolus

wizard will still function. However, the user will no longer have the rescue measure benefit of low glucose insulin suspend (Medtronic, 2016).

Why Is This System Called Hybrid Closed-Loop?

Since it is still recommended that the user initiate prandial insulin doses (insulin used to cover for carbohydrates consumed during a meal), it is not a completely closed-loop system; rather, it is hybrid closed-loop. Where a truly closed-loop system could deliver insulin autonomously, the hybrid system still works best when the user alerts the insulin pump before eating and gives themselves a dose of insulin to cover the food that will be consumed (FDA, 2018b). Although, research has shown that the system is capable of adjusting the prandial dose to cover a meal, currently available short-acting insulin does not act rapidly enough to maintain the appropriate blood glucose level after a meal (Ramkissoon, Herrero, Bondia, & Vehi, 2018).

How Much Support Is necessary?

Nurses should tailor their care to the child, and a large part of that may depend on the child’s knowledge of the system. Other considerations should include developmental level, cognitive abilities, age, and parental involvement. Nurses should communicate with parents and children to find out what education they have received and ascertain their current knowledge level about the device. For example, many individuals with diabetes already have some experience with insulin pumps, and although this system can still be life enhancing, it might not be as big of a life change as it is for someone who has never used an insulin pump or CGM. It may be helpful to know if a child is a novice to the technology, requiring closer monitoring and more guidance, or if they are experienced and require less oversight. For continuity of care, individualized healthcare plans should include the technology and level of support needed by the child, in enough detail that a substitute nurse can provide

safe support and emergency care if needed. Consider creating a list of local and online resources for support staff and substitutes.

How Should Blood Glucose Levels Be Assessed and Treated?

A glucometer is necessary to accurately measure blood glucose levels of children, even for those who wear CGM. Measurement of blood glucose levels is the foundation of care for diabetes, whether it be for prandial boluses, emergency management, or CGM calibration. There are only two wearable glucose monitoring systems approved for treatment decisions, the Dexcom G5, a CGM device, and the Freestyle Libre, a flash glucose monitor (American Diabetes Association [ADA], 2018; FDA, 2016, 2017). For children who do not have one of these systems determination of glucose level for treatment purposes should be made based on a capillary glucose check (ADA, 2018; FDA, 2016). The ADA (2018) advises that a target capillary plasma glucose range needs to be individualized based on factors such as the presence of hypoglycemia unawareness, but as a general guideline, preprandial levels should be 80 to 130 mg/dL and postprandial levels should not exceed 180 mg/dL.

It is important to remember that the measurement with CGM is not of current blood glucose level but is a measurement of interstitial glucose level (ADA, 2018). This is important because the value is similar to the plasma glucose level, but it reflects what the blood glucose level had been approximately 15 minutes prior to the measurement (ADA, 2018). A strong emergency plan should be covered in each child’s individualized healthcare plan as well as any other care needs unique to the child (National Institute of Diabetes and Digestive and Kidney Disease, 2018).

How Does This Compare With Other Systems?

The benefits of the hybrid closed-loop insulin delivery system are plentiful. Imagine a child who hates needles,

88 NASN School Nurse | March 2019

wants to do everything independently, rebels against authority but is known to have frequent low blood sugars. Although the problem of needle sticks is not completely alleviated by this system, needle sticks are limited to changing the pump and CGM, and calibration. As long as the CGM is communicating with the insulin pump, the child, parent, or nurse will be able to look at the insulin pump and see a glucose reading on the screen of the pump.

Without CGM, they should test their blood sugar whenever they want to give themselves insulin (such as before a meal), when their blood sugar feels low, after treating low blood glucose, before exercise, before going to bed and possibly at other times of the day, depending on their patterns (ADA, 2018).

Many CGMs allow the user to see a recent glucose level and trends over time, but for most devices, the user is advised not to base their insulin doses on the CGM data. With the CGM (Guardian 3) associated with the current hybrid closed-loop insulin delivery system, users are supposed to perform a capillary blood glucose check for every dose of insulin (FDA, 2018a). Even with these glucose checks, the user will not need as many needle sticks as they might with other diabetes management systems.

Depending on the type of CGM used, the glucose level will be displayed differently. A child’s glucose level may be displayed on the screen of the insulin pump, on a receiver, and/or via a mobile app. Even though there are devices that allow secondary users such as school nurses, to have remote access to a child’s CGM data, after obtaining permissions, it is important to research the program and to take into consideration the implication of having access to such data. There may need to be discussion with the parents or guardians about when the data will be available, and how to keep it protected if the decision is made to access data.

An older, but still commonly used method of diabetes management, is the use of insulin syringes or pens. As with all forms of insulin delivery, they may or

may not include CGM in their management. Insulin injections require the most frequent sticks for the user, including not only blood glucose checks but also injections with each dose of insulin. If users underestimate their carbohydrate count at a meal and their blood glucose becomes elevated, they may have to give themselves another injection.

For users of insulin pumps, insulin can be delivered with the press of buttons on the pump, and will be delivered through the subcutaneous catheter. Giving a second dose of insulin does not come with additional pain. There is protection as well, from the ill effects of overestimating carbohydrate count and giving too high a dose of insulin. The hybrid closed- loop insulin delivery system has low glucose predict insulin suspend, which halts the delivery of insulin when data from the CGM indicates that they are trending toward a low glucose level (FDA, 2018b).

Future Directions of Blood Glucose Management

Several exciting blood glucose management systems are on the horizon. Some, such as the bihormonal closed- loop insulin delivery systems, are not yet approved by the FDA, while others such as an implantable CGM system have recently received approval (FDA, 2018c).

Bihormonal systems include both insulin and glucagon. Because no systems of this type are FDA approved, all use is limited to clinical trials. The potential benefit of adding glucagon for blood glucose management is that glucagon is used to prevent hypoglycemia, allowing for tighter control of glucose levels with less risk for severe hypoglycemia. One system that has undergone clinical trials allows for the input of the user’s body mass and requires no further input from the user, a truly closed-loop system (El-Khatib et al., 2016).

Another recent development is implantable CGM, as opposed to the currently available transcutaneous CGM. Implantable CGM has the potential to be

in place for longer periods of time as it is currently FDA approved for up to 90 days of use (FDA, 2018c; Kropff et al., 2017). However, it requires placement in a provider’s office (FDA, 2018c). A relatively new technology, it has not yet been FDA approved for anyone younger than 18 years.

Conclusion

School nurses can support children as they navigate their disease and treatment, but only if they have current knowledge and skills in management of the illness. The hybrid closed-loop insulin delivery system is promising new technology that can help mute the high and low blood glucose levels that often occur in diabetes and facilitate a life less dictated by the need for routine insulin injections. School nurses can empower school children to apply the gold standards of diabetes management through understanding the advantages and limitations of treatment technologies and modalities. Knowledge of diabetes management allows us to provide an extra layer of support so that a child’s time in school can be focused more about learning and less about diabetes. ■

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Jennifer Latham, MSN, RN Registered Nurse Tacoma, WA Jennifer works as a pediatric nurse at Ashley House Kids taking care of children with complex care needs and at Mary Bridge Children’s Hospital in the Medical Surgical Unit.