Hybrid closed loop (HCL) insulin pumps are integrated with CGM devices. These systems use algorithms in apps that are off-label (not approved by Health Canada) to make decisions about automated insulin dosing. These algorithms are developed and made available for free by online communities. Systems require an external piece of hardware (a Link or a Rig) to communicate decisions between the app and pump. Some systems require older pump models to work. The algorithms use the data from some CGMs to make some decisions about automatically adjusting insulin without the user’s interaction e.g. can automatically increase, decrease or turn off basal insulin multiple times in an hour and may also provide automated boluses for corrections in addition to modulated basal rates. (Note, algorithms change regularly, as do features.) Carb counting is still necessary.
The algorithms used for each off-label HCL system is usually available for the public to view (unlike those for pumps with Health Canada approved HCL systems).
Patients building and using these systems do so at their own risk There are no warranties or liabilities assumed by the online communities that build these algorithms.
Of note, one of the "Looping" algorithms was submitted to the FDA in Jan 2021 with the hopes of it being approved as an app for iPhone for integration with an Omnipod version (first) prior to seeking integrations with other companies with whom they have agreements (Medtronic).
Role of Educators in Off-Label Pump Programming
It is important to still review the basics of diabetes control in pump therapy, especially safety and DKA prevention. As of April 2021 these off-label apps still require basal rates programmed by the user. Rates that are not appropriate for the user are likely to pose problems with glycemic control. This information below may also be of value.
- Since these are "off label" usages, we advise diabetes educators to not suggest the systems but rather to support those who are on them.
- Off-Label HCL pumping can be complex. Fortunately, most patients who loop are savvy in how to address most of their concerns and are safe on the system. If you feel they are not safe and cannot troubleshoot to stay safe, please consider discussions with the patient and endocrinologist to return to normal pumping (or as an alternate “open the loop”) for a time. This gives patients time to refer to their algorithm’s extensive documentation to become better informed, talk with their key looping resources (endos, some trainers) and gives other clinicians time to seek guidance if available. If patients don’t know what “open their loop means”…that might be an indication that they aren’t informed enough to be safe on the system.
- "Opening their loop" usually returns the user to most (but not neccesarily all) of the features of manual pumping while still using the Looping App with current programmed basal rates, ICR and ISF but not using automated basal (or bolus modulations).
- Patients returning to "normal" pumping (e.g. choosing not to "open the loop" in their app when troubleshooting) need to know their TDD at a minimum, but ideally their basal rates, ISF, ICR and insulin action time. Patients can provide clinicians their TDD according to what they see on their app at the end of each day (they would need to note that), or to view the history in their Apple Health App under Insulin Delivery (where they can swipe back to view each day’s TDD), or in Nightscout or Tidepool if using.
- Please note that any off-label algorithm can be updated and revised at any time, eg. tweaks, new features etc (assuming the patient updates).
- The electronic boxes that facilitate communication between off-label apps and pumps can lose connections. Usually after 20-30 minutes of lost connection the app resumes the reguarlly programmed basal rate.
- Learn from your patients. People who pursue this will likely pay close attention, and will be able to teach you a lot about what works for them. Avoid generalizing what patients tell you, as versions and types of algorithms differ and regularly change. Ask for explanations when you hear information that is unknown to you or sounds contrary to your knowledge.
- In an ideal world, clinicians would be just as informed of these algorithms as are savvy users. However, numerous pragmatics prevent this. Resources for learning about algorithms are below for clinicians, with the repeated caveat that algorithms can be updated at any time with different features and tweaks that are not Health Canada approved.
FYI re: "Looping" elements that the user can adjust
The following options can be adjusted by the user in the Master Version of Loop App as of now (April 13, 2021, tomorrow may be different.). This means, any of the following can be adjusted by the user to address glycemic control. Sorry for any ommissions!
- Basal rates
- Glucose targets for any time(s) of day can be preset and of course, changed on the fly (see Overrides below)
- Any units that are suggested for meal bolus or correction can be overriden with the units preferred by the user.
- Duration of Insulin Action (Settings >Insulin Model > Walsh)
- Overrides. These can be preset options or programmed on the fly. These can change glucose target and/or insulin dosing for any duration from 15 minutes up to indefinite. Note: 110% override of insulin means that all basal, and manual boluses and corrections will be increased by 10% while that override is on.
- Add Carbs Button and Absorption Time.
- Absorption time: For each addition of carb the person must choose an absorption time from 30 minutes to max 8 hours (although the dial offers 24 hours, it will roll back to 8 hr max). In other words, every food bolus is an extended bolus of some fashion. In this Master Branch, you cannot give all the food bolus at 0 minutes when entering the insulin through the "Add Carb Entry" button. Instead, 30 minutes is the lowest option, but most of the bolus is given at the time of manually programming, with the rest given as increased basal over the 30-minute period if that is the absorption period chosen. Pre bolusing is important for many people. Less important for those on very low carb diets. There are different options/methods for bolus delivery in the AB and FreeAPS branches of Loop (see below under Resources for URLs).
- People can input the meal in sections with different absorption times eg 20 g CHO @ 30 minutes plus 40g CHO @ 4 hours absorption. They can do as many of these as they wish (versus normal pumps that usually only allow for one extended bolus).
- Backwards adjustments to grams of carb eaten and duration of absorption are possible. e.g. The user can program in 30 g carb with suspected absorption over 2 hr. At 1 hour pc they are trending towards a low and realize they didn’t eat it all. They can go back and edit that they ate only 20 g. The algorithm will reduce the basal to adjust. They could also go backwards in time to change the absorption time to 1 hr.
- Any CHO entered can be "Saved without Bolusing." The system will interpret this to mean the user ate the carb and didn't bolus. The system will attempt to increase the basal over time to address the carb eaten for the absorption duration chosen...although it will still modulate basal according to glucose readings, so may not give all the insulin a user expected. This is not perfect. It can still over-deliver and result in hypoglycemia or under-deliver and result in hyperglyemia. Carbs saved without bolusing that weren’t actually eaten require the user to view the history, swipe left and delete, elsewise the current Master algorithm will still give insulin for it as per above.
- For any CHO entered, the user can look at the progress of the CHO eaten and bolus delivered. e.g. 30 g CHO programmed for 3 hr absorption and currently 16 g has been absorbed with a system-estimated 4 hr 15 min time for full absorption of the 30 grams.
- Many users will be surprised to go back through their day's meals to learn how much "estimated" CHO was truly absorbed. e.g. more CHO absorbed than what they ate. In other words, many users may find it beneficial to bolus for protein and fat according to whatever method they prefer or works for them.
- Again, these algorithms are tweaked regularly so the above items many not be accurate at the time you are viewing this. Please see the resources below for more up to date documents.
Please note that any off-label hybrid closed loop algorithm may be updated and revised at any time, eg. tweaks, new features etc.
- Looping Resources
- Looping information at https://loopkit.github.io/loopdocs/
- YouTube videos at https://www.youtube.com/watch?v=kgu-AYSnyZ8
- See Kenny Fox ones as start from begining and goes through step by step https://www.youtube.com/playlist?list=PLfnu6D6qjfHsXnqCqpnlZTBDryaj2m-gk
- Looping basal and ISF . https://www.youtube.com/watch?v=AgSZp7juPc4&list=PLfnu6D6qjfHsXnqCqpnlZTBDryaj2m-gk&index=7
- RileyLink or OrangeLink or EmaLink (one is needed to create communications betwee pump and iPhone Loop app) GetRileyLink Order Site - GetRileyLink or Step 5 Order a RileyLink - LoopDocs (loopkit.github.io).
- Note, there 3 algorithms commonly available for Loop as of April 15, 2021, and endless "developer" versions. All of these can be changed, tweaked at any point in time and be available for patients to use.
- OpenAPS Resources
- at https://openaps.org/
- #openaps and #WeAreNotWaiting on Twitter
- A "Rig" or "Edison" or sometimes even a Link (Riley etc) could be used. These are all "boxes" that faciliate communications between pump and off-label looping apps.