Getting the Most Out Of Hybrid Closed Loop Technology
As the name implies, HYBRID closed loop systems can’t do everything on their own. They can’t predict the stock market. They can’t figure out the teenage brain. And they can’t offset rapid changes in blood sugar levels. Users still must take responsibility for timely/accurate bolusing and adjusting to various lifestyle events. Think of it as a PARTNERSHIP between you and your technology.
That said, here are some strategies that can help you to gain the most benefit from your hybrid closed loop system.
Get your pump settings right first.
Having the correction basal and bolus settings will shorten the HCL “learning curve” and ultimately get you optimal results. That means doing basal testing/fine-tuning and analyzing your data so that the various aspects of your bolus settings are configured properly: including the insulin-to-carb ratios, correction factors, and duration of bolus action.
Count your carbs like a pro.
Even with the correct insulin-to-carb ratios, inaccurate carb counts will ultimately cause you (and the system) to come up short in terms of glycemic control.
Optimize your CGM performance.
Just about everything the HCL algorithm does is based on CGM data. To that end, if you use a sensor that requires calibration, do so on-schedule with a clean finger and a high-quality meter. Even if your CGM does not require calibration, it is worth spot-checking your sensor performance with periodic fingersticks and calibrating if necessary. Also, best not to use your sensors beyond their intended lifespan, as the accuracy can truly suffer.
Change the way you treat your lows.
Because the HCL will be cutting back on basal before, during and (sometimes) after a low occurs, you won’t need as much carb to treat your hypos.
Pay attention to bolus timing.
Bolusing late will cause the HCL to ramp up your basal insulin, and may produce hypos a few hours after the bolus is finally given. And since extended bolusing is not an option with most HCL systems, it will be necessary to alter the timing of boluses for slowly-digesting meals. This can be accomplished by entering the carbs in two parts or letting the system know that your meal will take many hours to clear (in HCLs that accept this type of information). A sound understanding of the glycemic index can be helpful in this regard.
Suspend when disconnecting.
If you use a pump with tubing that can be disconnected at the site, be sure to let the pump know when you are not connected. This way, the HCL knows that you are not receiving any insulin and can adjust the basal delivery accordingly when you reconnect.
It takes at least a few weeks to really understand how the HCL algorithm operates and to see if adjustments to your basic pump settings are needed. With some systems, the basal and correction bolus algorithms adapt based on your daily insulin use. So if you don’t see great results right away, hang in there.
Manage your infusion sites.
This can be the week link of the entire system… if you let it. For an HCL system to perform as intended, it is imperative that insulin absorb in a consistent, predictable manner. Change sites often, rotate carefully, and troubleshoot at the earliest signs of trouble. And choose a type of set that performs well. For many people, angled or steel needle sets produce better outcomes than flexible 90-degree sets.
Override with care.
In the vast majority of situations, it is best to trust the HCL’s dosing recommendations. However, if you feel the need to override, do so by c hanging carb entries rather than falsifying your glucose values. Entering incorrect glucose readings into your bolus calculator can negatively affect the performance of the CGM or algorithm.
Don’t hide anything.
The more the algorithm knows about your activities, the better it can perform. Enter EVERYTHING you eat – including the tiniest of snacks (unless you’re snacking prior to exercise to prevent a low) and treatments for lows.
Know when to shut it down.
Recognize that there may be times when you can manage your diabetes better manually than by using the HCL’s algorithm, such as days with very unusual foods and activities, or any time your CGM is operating poorly.
Use the system overrides.
All HCLs offer the opportunity to make the algorithm temporarily more or less aggressive. Some also allow you to switch to a different basal program or insulin profile. This is sort of like shifting gears when driving (when using a manual transmission). If you know your insulin needs will be higher or lower than usual, let the system know! Examples include illness, stress, high or low levels of physical activity, high-fat meals, alcohol consumption, and sleep times.
Plan ahead for physical activity.
Remember, HCLs have their limitations. They can’t reverse a sharply declining blood sugar caused by exercise. Setting a temporarily higher target or less-aggressive algorithm can help, but it needs to be set at least an hour prior to the activity. Even then, it will usually still be necessary to either cut back on any boluses given within two hours prior, or consume rapid-acting carbs before and perhaps during the exercise session.
Look at your damn data.
I know, nobody likes to look at their own data reports. It’s hard to be objective when evaluating one’s own information, and it’s just another task on an ever-growing list. Even if you just take a quick glance at some of your summary statistics and reports, it is worthwhile. People who do so tend to have much better control than those who don’t.
DIY Resources For Hybrid Closed Loop Resources
Useful Comparison Summary Between Loop and OpenAPS:
What you can see remotely on Nightscout:
Where to buy RileyLink:
Conference Presentations and Evidence for DIY APS (artificial pancreas system):
Officially Registered DIY APS Worldwide Numbers:
Current Popular Press Article in “The Guardian” – Good general background to DIY APS:
Internal Medicine Journal Article on DIY Closed Loop Systems Nov 2018:
Diabetes Australia Position Statement: