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Why I won’t be switching to Medtronic’s 670G insulin delivery system billed as the first artificial pancreas

As a type 1 diabetes patient, I have decided to stay on an open-source insulin delivery solution instead of switching to a hybrid closed-loop insulin delivery system from Medtronic whose FDA approval was widely hailed.

The MiniMed 670G system from Medtronic

When Medtronic won approval for the MiniMed 670G from the FDA in 2016, it was a big deal. Advertised as “The World’s First Hybrid Closed Loop System,” it is the first commercial product of its kind – able to automate insulin delivery and requiring lesser patient input than in the past.

However, after reading more about the specifics, and having heard more first-hand accounts, I can now safely say that I am somewhat underwhelmed.

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When evaluating the 670G I was exclusively looking at the features of the “auto mode” in comparison to the system I use now. That is the OpenAPS, which is an open source artificial pancreas solution built using an Intel Edison (tiny computer) and a Medtronic insulin pump. My initial thought was that it might be nice to use a commercial solution instead of an open source one if it could make my daily life easier (there are elements of using an open source solution that are tiring at best).

Here I lay out the reasons that drove my decision to stick with what I have instead of switching to Medtronic’s CGM. It should be noted, however, there is no one-size-fits-all solution for insulin-dependent diabetics. Ultimately, it’s a personal choice.

I can’t see what the device is doing
What it’s really doing, not just what the basal rate has been adjusted to, but how the system got to that decision. It’s not that I always read the exact calculations of the OpenAPS algorithm, but I could because I can access my live information at any time. I can access not just my blood glucose (BG) and basal insulin rate, but also the actual numbers and calculations going into the recommendations and changes that the system is making.

No personalized targets for blood glucose levels
The system targets 120 — all of the time. The only other option is a temp target of 150 meant for exercise. This means that I can’t set my own goal range. Using the OpenAPS my target BG is 100, my exercise temp target is 120-140. These may not be so far off of what the static targets for the 670G are, but the simple fact is that if my doctor and I decide that I want my targets to be higher or lower, I can’t just change them on the 670G. I don’t like the idea of a pump manufacturer deciding what my targets should be for me, let alone the fact that it is absurd to believe that a single target could be appropriate for every diabetic that could potentially use this pump. You wouldn’t expect a 5-year-old boy and a 60-year-old woman to have the same daily routines, so I don’t know why you would expect them to use the same BG targets either.

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The Guardian 3 sensor is “not intended to be used directly for making therapy adjustments.”
That is a direct quote from the Medtronic website. While the 670G system operates based on the readings from the Guardian 3 sensor, if you read the fine print it is approved “to control insulin dosing” – i.e. to be used in the context of the hybrid closed loop. This is different than the Dexcom G5 and Abbott Libre, which are approved to be used to make treatment decisions without confirming the reading with a blood glucose meter.

While diabetics were using the Dexcom readings to make treatment decisions long before it was approved, and people with the 670G will probably do the same thing, as far as the FDA is concerned, you should still be checking your Guardian 3 readings with a finger stick before making treatment decisions yourself. I initially had a concern about the accuracy of Medtronic sensors affecting the overall performance of the 670G system. Although I’m still skeptical based on the historical performance of the Enlite sensors, it appears that the Guardian 3 sensors represent a marked improvement from the Enlite sensors, addressing this concern.

None of this is to deny that some people have gotten fabulous results using the 670G. But I demand more flexibility and uptime and am willing to put up with the additional management required to build and maintain the OpenAPS solution.

With all that I’ve read on this, it seems like Medtronic has kind of been hyping the capability of the 670G. To me, it seems like a fantastic pump with a new feature, rather than the “The World’s First Hybrid Closed Loop System.”

And yet there is something that I do prefer about the 670G over OpenAPS and that is the relative support available for a commercial solution compared to a patient-built solution. By that I mean the commercial support that is available when you are using a pump or system from a manufacturer versus building and maintaining your own solution. With OpenAPS, I have to be ready to be my own system expert.

At the end of the day, it won’t be a single solution that “solves” diabetes for all patients. It is going to take different products for the many different types of people who live with this disease every day. The 670G and OpenAPS are just two of the many possible solutions helping insulin-dependent diabetics reach the best possible health outcomes.

Editor’s Note: This article was taken down for a period of time to verify an issue related to the accuracy of the belief of the author that the device has a 48-hour warm-up period beyond the first time it’s being set up. That entire section and any references to it has been removed. MedCity apologizes for the error. 

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