Lesson #22: "The Human Gap"

Stephen W. Ponder MD, FAAP, CDCES

In the era of continuous glucose monitoring (CGM), staying “in range” competes with the hemoglobin A1c as the most desired result of quality diabetes self-management. Why this shift in focus? In February 2019, the Advanced Technologies & Treatments for Diabetes (ATTD) Congress convened an international panel of physicians, researchers, and individuals with diabetes who are expert in CGM technologies to address this issue.

The International Consensus in Time in Range (TIR) group recommended persons using CGM strive to achieve blood sugar levels between 70-180 mg/dL at least 70% of the day. Furthermore, values below 70 mg/dL should be less than 5% of the day and over 180 mg/dL should be less than 25%.

The image below show TWO different 3 month time windows highlighting the consistency of TIR, average blood sugar and variability (standard deviation) using MDI-based Sugar Surfing™

Clinical studies now emphasize improved time in range as a primary outcome of hybrid closed loop insulin delivery devices. These high-tech devices are numerous now. They include several commercial versions and even more flexible DIY systems. Common to all systems is the machine-based ability to use patient CGM data to automatically adjust delivery rates and doses to achieve optimal TIR.

As more studies are published, it’s clear that these devices are a step (or leap) forward compared to standard insulin pumps with or without a CGM worn by the user. The ability to meet the 70% recommendation is now possible. Without these systems, TIR ranges were often far below the 70% minimum target.

Yet these studies have not reported results attaining the 90% or higher TIR range in large groups of users. It’s less common to find an established (non-honeymoon) type 1 diabetes hybrid closed loop insulin pump user attaining consistent 90% or greater TIR’s. But it does happen in some of my patients who Sugar Surf (manage dynamically).

In my opinion, the challenge we face in consistently achieving > 90% TIR has less to do with our technology and all to do with us. I call this the “Human Gap”.

I am a pediatric endocrinologist. My patients are still growing, learning, and maturing. This has a great effect on how well they use and maintain these high-tech devices over time. Most are enthusiastic adopters at first, but with time the luster of new tech settles into something less exciting and more tedious or even mundane. Just how much less exciting or more mundane impacts the width of the “Human Gap”.

So far, the best published clinical studies report up to 70% average TIR for some hybrid closed loop users. This is certainly positive without question. Frankly, many persons would be very pleased by this and not have much reason to strive for any higher. Others might ask why 70% seems to be an upper limit that is so challenging to break through.

Therefore, what contributes to the Human Gap? There are at least three reasons which account for most of this barrier. They are: 1. Quality and consistency of carbohydrate counting skills, 2. Insulin bolus timing and 3. Just remembering to bolus. Another minor but occasionally challenging barrier is how all the wearable tech is maintained by the user (pump sites, proper programming and in some cases keeping things charged up properly).

As a person with diabetes of over 56 years, I still find carb counting challenging. Not only regarding the carb amount in a meal or snack, but in judging the speed of a carbohydrate (or meal containing carbs) in changing my blood sugar levels. Sugar Surfers know carbs have different onset speeds, a bit like insulin speeds. Sugar Surfing teaches me to focus on knowing the blood sugar raising effect of commonly eaten foods. But this is far from totally predictable. Nothing in human biology can be viewed with a complete sense of accuracy and precision. Nevertheless, getting close does count when you Sugar Surf.

Patients using hybrid closed loop systems may or may not download their system data reports for occasional lookovers. When I do this with many of my patients and families it’s common to find blood sugar spikes with no accompanying meal insulin dose or a bolus insulin dose that is given well after the meal has been eaten. In cases of small children it might be a compromise to eat first, bolus later. There are other valid examples supporting insulin after-bolusing. But I’m not referring to these exceptions. These examples I refer to are missed or delayed boluses due to lack of attention or even forgetfulness. I refer to them in clinic using the baseball metaphor “unforced errors”.

I’ve been consistently using a CGM since 2008. It’s simply a part of my daily routine to glance at my CGM trendline (as I write in the book Sugar Surfing) many times a day. This creates a pattern of “glycemic mindfulness” which I rely upon to base self-care choices on “in the moment”. This forms the foundation of Dynamic Diabetes Management (aka Sugar Surfing). Furthermore, I practice this approach without the benefit of an insulin pump now. I use multi-dose insulin (MDI).

My TIR using MDI and CGM, driven by Sugar Surfing, is consistently in the mid 90% range over time (see above). No hybrid closed loop system is necessary for me. As I compare my results with others, the reasons come down to these:

1. Mindfulness: being aware of what my CGM trendline is doing (i.e., glancing)

2. Recognizing/remembering patterns to make better future dosing/eating choices

3. Insulin dose timing based on the trendline direction and current circumstances

4. Not forgetting to dose when the opportunity presents itself

5. Taking the time to best estimate the carbs in my food/snacks

Your hybrid closed loop pump does not know what you are eating, how much, how long you take to eat, what you are doing physically, if you are feeling ill, tired, or stressed. You have to input most of these things by yourself. And even then, you may be guessing.

I have no doubt that many of you who have gotten this far will say “I do all those things”. My response would be that you are likely to have very respectable TIRs. Some Sugar Surfers do an outstanding job Surfing with hybrid closed loop systems. It's truly the best of both worlds. I applaud you!

So… how does my MDI and CGM TIR approach “beat” CGM-enabled hybrid closed loop systems? Now you know why: Sugar Surfing helps me close the human gap. And only YOU can close it. Maybe our diabetes tech will close this gap someday. But until then: Surf on!