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By kristalamb
Posted date: March 24, 2020


By Bruce A. Perkins, MD, endocrinologist, and person living with T1D

Adapted by Krista Lamb

Living with type 1 diabetes can be complicated at times, and new technologies can add another layer of complexity. For some, new technology has meant better blood sugar control and improved quality of life. For others, well, it’s just another item on an already exhaustive list. Still others are achieving targets and self-managing fine without these systems, and they worry a new technology could throw off the delicate balance they’ve worked hard to achieve.

This is the reality as patients and healthcare providers try to determine if one of the latest technological advancements—a hybrid closed loop system—is the right fit.

A hybrid closed loop system automates basal insulin delivery throughout the day, still relying on the patient to deliver bolus insulin at meal times and correction doses for high blood sugars. For many, this system reduces the burden of managing blood sugar levels throughout the day. However, it requires an engaged and informed user who has been coached by their healthcare team in how to use the system safely and effectively.

In Canada, there is one approved technology (Medtronic 670G), some unapproved “do it yourself (DIY)” systems that use cell phone apps, and new systems are expected to be approved soon, following recent approvals in the U.S.

Is a hybrid closed loop system right for you? Below is some information, adapted from my recent paper in the Canadian Journal of Diabetes, to help you decide.

Maintaining the insulin pump and sensor functions require some work.

For a patient, this means changing and rotating the infusion sets regularly, managing the sensor and transmitter, calibrating with a glucose reading at least two to three times a day, and responding to the system when it requests additional information. For someone who is comfortable with the technology and with the level of awareness required, this may not be an issue, but you want to be certain you understand what needs to be done and how often before you start using the system.

It can be expensive.

The above-mentioned sensors and transmitters, as well as the hybrid closed loop system itself, involve a number of financial considerations. If you do not have an insurance plan or the ability to incorporate the cost of using a hybrid closed loop system into your budget, it is likely not the solution for you. Even a DIY version requires an investment in the initial technology (which can be challenging to find) and still requires the use of sensors. Starting with access to only a temporary supply of sensors is not advised.

You need to understand the goal blood sugar range – and it’s not necessarily what you think it should be.

Patients using a hybrid closed loop system like the Medtronic 670G may be surprised that their fasting blood sugars are as high as 6.7 mmol/L, for example. But this is the system’s intended target. Research shows that maintaining SG levels between 4-10mmol/L for at least 70% of the time will approximately equal an A1C of 7%.

Of course, the system won’t provide such a stable blood sugar level, but it aims to keep your blood sugars in target range of 4-10 mmol/L. If you think you can achieve better targets without intervention, then an open loop system is probably a better option for you.

You need to trust the system.

A hybrid closed loop system uses an algorithm to determine the user’s insulin needs. After two to six days of monitoring your glycemic patterns the Medtronic system can be used in auto mode. During this time, a micro bolus of insulin is delivered every five minutes and adjustments are made if the sensor glucose level drops below or rises above the set threshold. For the user of any system, there needs to be a certain amount of trust in the system. If you focus on management at meal times and let the algorithm make decisions the rest of the time, your outcomes will likely be better than if you try to override the system. Unless you receive an alert telling you to make an adjustment (for example a hypoglycemia alert), you should avoid adjusting your insulin between mealtimes. Forcing a correction bolus could lead to hypoglycemia.

You have to focus on accurate delivery of the food bolus.

Most hybrid closed loop systems are not completely automated—the patient still needs to deliver an accurate food bolus. So while the system does an excellent job of maintaining blood sugars in target when you’re not eating, it depends on accurate notification of meals. You still need to count carbohydrates, evaluate your carb ratio and, in many cases, bolus before starting a meal. In fact, it’s often the most important element of successfully working with a hybrid closed loop system. If you are able to take an accurate food bolus, the system adjusts to bring your levels into the target range by the next meal or bedtime. If the bolus is missed or the carb count is inaccurate, the sensor glucose level may rise dramatically and the algorithm will not be able to bring you back into range in such a short time. If carb counting is a struggle or you often find yourself out of range after meals, you will want to work closely with your healthcare team if you decide to try a closed loop system.

Your care team can help with the details.

You’ve decided to try a hybrid closed loop system. You can afford the costs, you’re comfortable with the technology and you are providing accurate information at meal times. You will still want to consult closely with your healthcare team.

In my practice, those on a closed loop system have reported issues with the “dawn phenomenon”, where glucose levels rise as you wake. Users may also need to adjust the amount of carbs used to treat a hypo or have a shorter active insulin time. These are all things where your endocrinologist or other members of your diabetes care team can provide support.

In the end, the best diabetes management system is the one that helps you maintain your optimum glucose control without creating unnecessary stress in your life. You need to consider honestly how much or how little technology makes sense for you. Your healthcare team can assist in making these decisions by outlining the pros and cons of your options.

Adapted from the paper “Talking Points for Helping your Type 1 Diabetes Patient Decide About Hybrid Closed Loop”, published in the Canadian Journal of Diabetes, October 2019, written by Bruce A. Perkins, MD, MPH, Nancy Cardinez, NP, CDE and Christine F. O


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