Medtronic 670g

I love your ingenuity! But I highly doubt many would be willing to do all this.

What really struck me is that all this effort would suggest the sensor itself is built better than Medtronic’s. I always assumed the major difference was in how the software interpreted the raw data, and Dexcom just had more experience to make software updates with. I think of the sensor as being nothing more than a wire coated in a reagent, but I guess there must be some more value built into it.

I wanted the Tslim so bad at the time. I still do. I get a bit envious knowing that all the workload to manage this condition is handled by the pump and not the user. Medtronic has partnered with dexcom it’s just when will it be available. I think that dexcom and a medtronic pump would almost as superior as the tslim. If Medtronic loses enough customer base maybe they’ll pull in their horns a little quicker. As long as I know it’s going to happen I can keep my sights on that and not focus so much on what I don’t have.

That sounds like alot of work. Hopefully Medtronic is listening to the Diabetic community that their sensors suck.

Well they have improved them compared to the original sof-sensors I started with in early 90s.

It must have some value that changes with the glucose level. It probably has a resistance value in Ohms that the transmitter uses to calculate estimated glucose level and then converts the value to a digital output that it sends to the pump.

I don’t know if CGM sensor technology has changed drastically or not. I poked around about 5 years ago to attempt to learn more about on how CGM sensors work. The link below is to a May 2014 Diabetes Forecast non-technical overview article.

The sensor starts with an enzyme, glucose oxidase, which converts glucose + oxygen to gluconic acid + hydrogen peroxide. The hydrogen peroxide then reacts with platinum inside the sensor, resulting in (I think) oxygen, hydrogen gas, and an electron or two. The electrons are the source of the current from the sensor.

Medtronic pumps at least as recently as my 630G reported this current from the sensor as the “ISIG” value. I’m pretty sure that acronym just stands for “current signal”. (“I” is a standard symbol for electrical current in the tech world).

The reason the sensor is calibrated after it is initially inserted is to allow time for the chemical process to stabilize (pretty much). Immediately after insertion the ISIG from my Enlites oscillated back and forth but then eventually stabilized.

At its simplest, calibration amounts to assuming your blood glucose is directly proportional to the current (ISIG) from the sensor. You divide the blood glucose value entered at calibration by the ISIG value reported by the sensor to get a conversion constant. After calibration, the sensor ISIG value is multiplied by that calibration constant to get a glucose value.

That’s the view from 30,000 feet as I understand it. As the technology has progressed, I’m sure there are a lot more nuanced details to it now.

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Medtronic is a very large company and will NEVER team up with others. They are insular. So don’t expect them to.

A few points from a (former) 670 user:

  • Guardian 3’s are about the same accuracy as a G6 (I wore both for a couple of weeks), but were still a major impediment for me because of errors, the way they interact (or don’t) with the pump, above all the elaborate and required taping system that made changing sensors a much more time consuming PITA compared to Dexcom.

  • Lots of getting woken in the wee-hours by the pump demanding attention due to sensor errors or other problems. One of the more annoying ones: if you go too long without requiring a micro-bolus (2 hrs?), it bumps you out of auto with an alert. NOT the hands-free experience promised.

  • The fixed BG target of 120 in practice yields something like a 140/ ~A1C 6.5+ average. If you’re struggling to get your BG down under 7A1C, you’ll like it more than I did. I was getting 6.0 before, but 6.5-6.6 on it.

  • My Range was 80-140, and I was getting 80% TIR, but my average was at the top of that range, not the middle. I did all the recommended hacks and couldn’t tweak it beyond that mark.

Coming improvements:

  • The 780G is going to allow a flexible target setting, allowing user to set it as low as 100. My understanding is that the 770G does not allow that adjustment.
  • I believe the next version of the Guardian sensor is going to eliminate the kludgy taping.

Well, they’ve said they were planning on it, but whether it ever actually happens? Yeah, not holding my breath.

Hey DrBB!

I agree with most of what you said. However, I don’t understand the comment about the PITA taping procedure. After inserting the sensor, I simply pull out the tape tab and apply the provided clear tape to hold the sensor in place. When the transmitter is charged, I insert it onto the sensor and apply the tape tab to hold it in place.

At the end of the first 7 days, I remove the tape tab holding the transmitter in place, charge it, reinsert it, reapply the tape tab and use another clear tape to hold both the sensor and transmitter in place for another 7 days.

Since I have been on the pump(2008) my A1c’s have been consistently in the 6’s. The only inconsistencies are when I change my site and if I correct a few times and it doesn’t come down then I know it is in blood. That is what the diabetic clinic I go to told me is that I don’t get the full correction or bolus because the insulin is in blood. I may be on a small dose of basal but I am quite able to receive the amount of insulin I need to keep me healthy and avoid complications.

I’m always quite blunt with you, trying to get you to understand the incompetence of your medical care team. They’ve proved it time and time again, but you continue to blindly trust them.

  1. They haven’t questioned your unusual insulin needs, nor performeded further diagnostic testing. I bet you’re the only patient in their practice with insulin dosages as low as yours, excluding infants if they treat them, but they continue to treat you just like the rest of the masses. You fight me on it with ZERO basis for refute, but you need to be tested for MODY. Though I’m starting to understand there’s little purpose to that when they probably wouldn’t know what MODY is nor how to treat it differently.

  2. They don’t know the limitations of the devices they prescribe. They’re clearly not doing any independent investigation.

  3. They’ve prescribed you a DANGEROUS insulin regime. You should be on diluted insulin. That’s not my personal opinion. It’s FACT. When your insulin needs are less than the margin of error of the delivery device, you NEED to dilute the insulin. It’s irresponsible and negligent of them. Pumps malfunction ALL THE TIME. Normal operating conditions are dangerous to you, but it malfunctions…

  4. Now they’re flat out making :poop: up, seeking explanations for what they don’t understand. I have a master’s in molecular and cellular biology.
    I accept that a master’s doesn’t sound as impressive as an MD, but I have more education in Physiology than they do. Physiologyy is my wheelhouse I assure you that your boluses are NOT getting dilluted by blood. That’s complete and utter nonsense. If your insulin is in blood, then it’s going to be circulated faster and more effectively than a subcutaneous infusion. I would wager anything that you’re simply not getting the insulin you requested because the pump can’t operate to your specifications.

I’m not a mean person, I promise. I’m not fighting you. I feel passionately FOR you. I’m angry at your medical team for their ineptitude. All I want is for you to be informed so you can advocate for yourself… Because your medical team isn’t capable of it. The fact that you’re doing so well has NOTHING to do with your care team nor your technology. It’s a testament to your own personal achievement. Imagine how much your life could improve if you had you more effective tools to manage with?

You can’t come back and claim now you’re getting all your insulin when you post often asking for help because of inconsistent behavior.