Why We Chose to #Loop #WeAreNotWaiting

I’ve started to document our Loop journey. Here’s an explanation of why we chose to begin it.

Caleb and I were in the lobby of his dance studio and he started jumping up and down - not for dance but because he has just received an email announcing his acceptance to the Global Leadership program to which he applied. Up until that moment, I was pretty certain I had nothing to worry about, expecting he would not be awarded the scholarship. Not that I don’t have confidence is his abilities, I just assumed it was a competitive program (which it was) and a long shot (apparently not).

As Caleb is celebrating, I really want to be happy for him, but I’m overwhelmed with dread. I’m responsible for Caleb’s care overnight. I prioritize his need to sleep as a growing young man, and take any measures necessary to keep him safe with as little disturbance to his rest as possible. He’s been on sleepovers and overnight field trips, and although he’s gotten through them, they’ve been complicated. We were just in Italy for a family trip last summer and with irregular eating patterns, carb intense meals, and walking seven miles a day, diabetes management worked out reasonably well, but took a lot of extra attention, creative extended boluses, temp basals, and corrections overnight to keep him safe. All of which I did.

Caleb knows what to do in the waking hours of the day, and if he has any questions, I’m usually accessible to trouble-shoot, but overnights and vacations are my responsibility. He’s fourteen - vacation should be a vacation, not extra work and stress. He’s not immune to the anxiety that the variables of traveling bring, I just do my best to soften the burden as much as possible.

I couldn’t grasp how we were going to get him prepared to do it all within the next five months. All I could think of were the overnights - him exhausted after a long, active day, with carbohydrates releasing into his bloodstream willy nilly, an artificial process crudely, manually, and non-scientifically slapping insulin at him, with aftereffects of varying levels of activity unpredictably lowering his blood sugar - to me, it was somewhat horrifying.

I heard it over and over again - “He’ll be fine!” Yes, he’s a bright young man and very responsible about his diabetes - he’s never forgotten to bolus for a meal, for example - but that isn’t useful when you’re in a deep sleep, unresponsive to alarms blaring directly into your ear, and your blood sugar is 70 with a rapid drop alarm. I know the term “dead in bed,” and I can’t ignore it.

My goal for Caleb’s blood sugar on this trip was not optimal care. My goal was no need for emergency intervention: no severe hypoglycemia resulting in unconsciousness and no hypoglycemia resulting in vomiting. Okay, something a little tighter than that, but really, if that’s what it ended up being, it would have been fine. I just wanted Caleb to be safe.

We decided to try Loop because overwhelmingly what I read about a hybrid closed loop system was the safety and assurance it provided overnight and how users were able to sleep like never before.

Simplistically, this is what Loop does:

An app on Caleb’s phone performs a bit of magic. It communicates with his pump through a little computer (see the pic above) via bluetooth. The app connects with Dexcom, assesses his current blood sugar level, the direction of his blood sugar, the amount of carbohydrates he has on board and the amount of insulin he has on board predicts what his future blood sugar will be. Based upon those predictions and the defined target bg range, the Loop app will calculate a need for insulin dosing, either higher, lower or the same and change Caleb’s basal insulin to administer any adjustments. This evaluation is done every five minutes, and his basal is adjusted every five minutes. Caleb does nothing while the app, dexcom and his pump do the work.

If Loop predicts a low blood sugar three or four hours in the future, basal will be reduced or shut off. If Loop predicts a high blood sugar, basal is raised. We’ve managed Caleb’s blood sugar manually in a similar, albeit much broader way - played with basal to address rising and dropping bgs that weren’t what we expected. We’ve used SuperBolus techniques, again, using basal to deal with the peaks and valleys of certain foods, like breakfast cereal. But what we’ve achieved manually doesn’t compare to what is attained by recalculating future bg and adjusting dosing every five minutes.

My hope was that Loop could be the watchdog over Caleb while he slept, when I couldn’t be there, softening out the Dexcom line and keeping him safe.) our Loop journey. Here’s an explanation of why we decided to travel it.


Does that take into account variation throughout the day in insulin sensitivities, dietary fat intake, or changes in activity? there are so many factors that influence our bg’s…

Insulin sensitivities - yes. I can set different insulin sensitivities throughout the day.

Dietary fat intake - yes. There is a Dynamic Carb Absorption feature which assesses how your blood sugar reacts to the amount of carbs you’ve consumed (because you input them when you eat) compared to how it expected it to react. If it believes you haven’t absorbed all the carbs you said it would, it will lower insulin delivery sooner to compensate for the delay and it keeps the carbs “on board” for an extended period which increases insulin delivery later. This is a relatively new feature (July 2017 and available after Caleb came back from his trip) and in addition to Loop’s ability to apply different carb absorption durations for different foods - cereal fast, pizza slow - which is programmed into the app and is a choice you make when you input your carbs when you eat.

Changes in activity - not so much. This is where we have the most difficulty. When we know Caleb will be active, we can change his target bg to a higher range so that insulin delivery is reduced overall. This is more guessing than anything though. It’s helpful but imperfect.

All of these aspects are not completely hands-off. They are just less hands-on that non-Loop pumping.

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That sounds like it’s calculating a lot like a well-informed pumper (but in more detail than most of us could endure) Excellent, Lorraine. Thanks for the info.
My activity level is what so drastically changes my insulin needs. Even without IOB, it doesn’t take a lot of activity increase to see my bg’s plummet. Unplanned activity is what I “fear” the most. :slight_smile: Not reducing boluses and basal ahead of unplanned activity means I’ve got to eat something, and guess as to what would be the correct amount–a guess that sometimes is rewarded with no major hypos/hypers. Other times, its an utter failure.

We have found this system to not be able to compensate fully for significant levels of activity - even that which is planned. For example, Caleb used this while he was at week-long tap dancing festivals. He would dance for five or more hours a day. Our strategy was usually to have him start with a bg over 200 and a higher target bg range set.

His weeks of tapping were pretty uneventful though thanks to Loop looking out for him. He danced without interruption because of us being proactive combined with Loop turning basal off when his bg started to drop. There were times when he ended the day and needed to treat, but I’m confident without Loop he would have had to check throughout the day and compensate one way or another, likely eating carbs throughout the day. So it’s not perfect, but it has definitely softened the effect. Not a lot of double arrows, or even single straight down arrows.

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@Lorraine - Loop predicts the BG and so will cut basal to prevent a low. Can it also predict that the cut of the basal will not be sufficient and raise an alarm that says you need to eat 14 carbs now?

This is a good point to raise as it is a limitation to a looping system - there is only so much insulin you can subtract from delivery.

It does not not alarm - I think the only time there is an alert is when Loop is not connected and I’m not sure if that’s audible. I’m at a disadvantage bc I’m not a user and I haven’t had to pay close attention. That’s not completely true, actually. As a caregiver, I get alerts on Nightscout for highs, lows, and disconnected Loop, but there is no alarm for a predicted low. The user, of course, gets high and low alerts directly from dexcom.

However, you can see the expected low on the Loop graph, see that Loop has shut down basal and that it’s not sufficient to address the low and then decide to take action. I’ll have to ask Caleb - I don’t think it estimates an amount of carbs that will help, but you can input an amount and it will adjust the predicted bg to give you validation of the amount. You have to be attentive to do all this though. It’s not a “set and forget” scenario.

Which of course is the thought behind the pump from (I think) Beta Bionics? (under development or trials or FDA or something but not released in any event) which would have two chambers for both insulin and glucagon. And there is no predicting how long this might take to actually hit the market.

It seems like an easy approach using existing technology (once the tech already has BG prediction and basal reduction/cutoff) is to simply alert the user and with a “feed me” message. I assume Loop has some sort of “request” queue for new enhancements? Maybe this would be an easy one to get added into a future Loop software release?

Yes iLet. They expect to release an insulin only closed loop system before the dual chamber one.

Yes, I do believe there is a request queue and this would be a good one!

@Lorraine is right. Loop does not currently predict a low and suggest a carb correction. There are plenty of audible alarms, however, from both the Dex receiver and the Nightscout display. If your other settings are matched well to your needs, Loop is dependable, but not perfect, with preventing lows. The user does need to still pay attention but not nearly as much as without a closed loop system.

You’re right, though, that a bi-hormonal pump that includes insulin and glucagon will give the system both an “accelerator” and a “brake.” At this moment in the development of these systems, I am impressed with how much control an insulin only basal adjusting system has.

Shelf-stable glucagon has been on the horizon of closed loop designers and hopeful users for a while and seems to be one of those technical improvements to tantalizingly remain one to two years out for the last several years.

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It seems to me that another thing that looping is unable to do is completely compensate for how long it takes insulin to start and stop working. Of course because it is able to predict lows somewhat and start reducing insulin ahead of time, it does a better job than I do with temporary basals. But it still takes a long time for temporary basals to take effect.

I still think that looping is magical, but I have determined that I just don’t want to or need to do it. I actually gave a D-friend my old Medtronic pump and he is successfully looping.


We only have so much glycogen stored in our livers. You can’t keep pumping in glucagon, expecting it to stimulate glycogen release, after it’s all gone…at some point, one is going to have to eat carbs. I see so much potential abuse of a system that contains glucagon. Sort of like “self driving” cars, in their infancy. Better keep your hands on the wheel, folks!

Not to mention the extraordinary high cost of glucagon. And until an insulin is available that lasts mere minutes, subq application of insulins as they are now, simply last too long. Humalog lasts over 4 hours for me.

This is a good point. I’ve read that people who experience a severe hypo should be vigilant about avoiding another one within the next day or so. If the liver glucose tank is empty, no amount of additional glucagon is going to draw more glucose from it.

My understanding is that the iLet pump dispenses extremely small amounts of Glucagon unlike a Glucagon injection which is a massive amount of the hormone. But you’re right that we can’t get help from Glucagon if our liver is depleted.

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Yes, I know the idea is that small amounts of glucagon would be used.


Glucose-normals and non-insulin-dependent T2s do fine and don’t run out of glycogen. That’s about 97% of humanity :slight_smile:

Too bad I don’t fit into that category, Pecos. (and were you referring to GLYCOGEN, not “glucagon”?)

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You wouldn’t either. You don’t have any less than they do :slight_smile:

Thanks for the edit, I corrected the original!

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